ETH Price: $2,523.33 (-1.24%)

Transaction Decoder

Block:
22547051 at May-23-2025 05:27:23 PM +UTC
Transaction Fee:
0.000484236792588732 ETH $1.22
Gas Used:
195,812 Gas / 2.472967911 Gwei

Emitted Events:

89 FiatTokenProxy.0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef( 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef, 0x000000000000000000000000e420c6095f04789236332b4e1877001c651c7fce, 0x00000000000000000000000074de5d4fcbf63e00296fd95d33236b9794016631, 0000000000000000000000000000000000000000000000000000000020c85580 )
90 FiatTokenProxy.0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef( 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef, 0x00000000000000000000000074de5d4fcbf63e00296fd95d33236b9794016631, 0x000000000000000000000000a69babef1ca67a37ffaf7a485dfff3382056e78c, 00000000000000000000000000000000000000000000000000000000207ee6ac )
91 ENA.Transfer( from=0xA69babEF1cA67A37Ffaf7a485DfFF3382056e78C, to=Spender, value=1362202415361501825117 )
92 ZeroEx.0x829fa99d94dc4636925b38632e625736a614c154d55006b7ab6bea979c210c32( 0x829fa99d94dc4636925b38632e625736a614c154d55006b7ab6bea979c210c32, 58f273ed50222da430199c4d74a313923c1635097143bb48024876af9375673e, 000000000000000000000000a69babef1ca67a37ffaf7a485dfff3382056e78c, 00000000000000000000000074de5d4fcbf63e00296fd95d33236b9794016631, 00000000000000000000000057e114b691db790c35207b2e685d4a43181e6061, 000000000000000000000000a0b86991c6218b36c1d19d4a2e9eb0ce3606eb48, 00000000000000000000000000000000000000000000000000000000207ee6ac, 000000000000000000000000000000000000000000000049d85b2783796e085d, 0000000000000000000000000000000000000000000000000000000000000000 )
93 FiatTokenProxy.0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef( 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef, 0x00000000000000000000000074de5d4fcbf63e00296fd95d33236b9794016631, 0x0000000000000000000000002acf35c9a3f4c5c3f4c78ef5fb64c3ee82f07c45, 0000000000000000000000000000000000000000000000000000000000496ed4 )
94 ENA.Transfer( from=Spender, to=[Sender] 0xe420c6095f04789236332b4e1877001c651c7fce, value=1362202415361501825117 )
95 MetaSwap.Swap( 0xbeee1e6e7fe307ddcf84b0a16137a4430ad5e2480fc4f4a8e250ab56ccd7630d, 0x62db2e87ad4360c521a990935f97f7c44833c4f99a8f1c09129331715b07f525, 0x000000000000000000000000e420c6095f04789236332b4e1877001c651c7fce )

Account State Difference:

  Address   Before After State Difference Code
(Titan Builder)
5.04333903584582694 Eth5.043534847846610188 Eth0.000195812000783248
0x57e114B6...3181e6061
0xA0b86991...E3606eB48
0xDef1C0de...027b25EfF
(0x: Exchange Proxy)
0xe420c609...c651c7FCe
0.056803958010632429 Eth
Nonce: 223
0.056319721218043697 Eth
Nonce: 224
0.000484236792588732

Execution Trace

MetaSwap.swap( aggregatorId=pmmFeeDynamicv4, tokenFrom=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48, amount=550000000, data=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
  • FiatTokenProxy.23b872dd( )
    • FiatTokenV2_2.transferFrom( from=0xe420c6095F04789236332B4e1877001c651c7FCe, to=0x74de5d4FCbf63E00296fd95d33236B9794016631, value=550000000 ) => ( True )
    • Spender.swap( adapter=0x7bBa8Bd42A19DA78326bE908E2cd52604399a748, data=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
      • 0x7bba8bd42a19da78326be908e2cd52604399a748.92f5f037( )
        • FiatTokenProxy.dd62ed3e( )
          • FiatTokenV2_2.allowance( owner=0x74de5d4FCbf63E00296fd95d33236B9794016631, spender=0xDef1C0ded9bec7F1a1670819833240f027b25EfF ) => ( 115792089237316195423570985008687907853269984665640564039457582503589178396239 )
          • ZeroEx.aa77476c( )
            • NativeOrdersFeature.fillRfqOrder( order=[{name:makerToken, type:address, order:1, indexed:false, value:0x57e114B691Db790C35207b2e685D4A43181e6061, valueString:0x57e114B691Db790C35207b2e685D4A43181e6061}, {name:takerToken, type:address, order:2, indexed:false, value:0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48, valueString:0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48}, {name:makerAmount, type:uint128, order:3, indexed:false, value:1362202415361501825117, valueString:1362202415361501825117}, {name:takerAmount, type:uint128, order:4, indexed:false, value:545187500, valueString:545187500}, {name:maker, type:address, order:5, indexed:false, value:0xA69babEF1cA67A37Ffaf7a485DfFF3382056e78C, valueString:0xA69babEF1cA67A37Ffaf7a485DfFF3382056e78C}, {name:taker, type:address, order:6, indexed:false, value:0x74de5d4FCbf63E00296fd95d33236B9794016631, valueString:0x74de5d4FCbf63E00296fd95d33236B9794016631}, {name:txOrigin, type:address, order:7, indexed:false, value:0xe420c6095F04789236332B4e1877001c651c7FCe, valueString:0xe420c6095F04789236332B4e1877001c651c7FCe}, {name:pool, type:bytes32, order:8, indexed:false, value:0000000000000000000000000000000000000000000000000000000000000000, valueString:0000000000000000000000000000000000000000000000000000000000000000}, {name:expiry, type:uint64, order:9, indexed:false, value:1748021273, valueString:1748021273}, {name:salt, type:uint256, order:10, indexed:false, value:904625697166532776746648320380374280103671755129338649140235469090245836851, valueString:904625697166532776746648320380374280103671755129338649140235469090245836851}], signature=[{name:signatureType, type:uint8, order:1, indexed:false, value:3, valueString:3}, {name:v, type:uint8, order:2, indexed:false, value:27, valueString:27}, {name:r, type:bytes32, order:3, indexed:false, value:E03E0E0E61B0B1043147F6FBAF8498C577937692578B2EDD45A4DF4C999CBD09, valueString:E03E0E0E61B0B1043147F6FBAF8498C577937692578B2EDD45A4DF4C999CBD09}, {name:s, type:bytes32, order:4, indexed:false, value:5A6AB7C07182A3430B0C1260074C69D898AB3E3AABDE12B677B75D5F4CA1AD1C, valueString:5A6AB7C07182A3430B0C1260074C69D898AB3E3AABDE12B677B75D5F4CA1AD1C}], takerTokenFillAmount=545187500 ) => ( takerTokenFilledAmount=545187500, makerTokenFilledAmount=1362202415361501825117 )
              • Null: 0x000...001.8d6d00bf( )
              • FiatTokenProxy.23b872dd( )
                • FiatTokenV2_2.transferFrom( from=0x74de5d4FCbf63E00296fd95d33236B9794016631, to=0xA69babEF1cA67A37Ffaf7a485DfFF3382056e78C, value=545187500 ) => ( True )
                • ENA.transferFrom( from=0xA69babEF1cA67A37Ffaf7a485DfFF3382056e78C, to=0x74de5d4FCbf63E00296fd95d33236B9794016631, amount=1362202415361501825117 ) => ( True )
                • FiatTokenProxy.a9059cbb( )
                  • FiatTokenV2_2.transfer( to=0x2aCf35C9A3F4c5C3F4c78EF5Fb64c3EE82f07c45, value=4812500 ) => ( True )
                  • FiatTokenProxy.70a08231( )
                    • FiatTokenV2_2.balanceOf( account=0x74de5d4FCbf63E00296fd95d33236B9794016631 ) => ( 0 )
                    • ENA.balanceOf( account=0x74de5d4FCbf63E00296fd95d33236B9794016631 ) => ( 1362202415361501825117 )
                    • ENA.transfer( to=0xe420c6095F04789236332B4e1877001c651c7FCe, amount=1362202415361501825117 ) => ( True )
                      File 1 of 7: MetaSwap
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      import "@openzeppelin/contracts/utils/Address.sol";
                      import "../Constants.sol";
                      contract CommonAdapter {
                          using SafeERC20 for IERC20;
                          using Address for address;
                          using Address for address payable;
                          /**
                           * @dev Performs a swap
                           * @param recipient The original msg.sender performing the swap
                           * @param aggregator Address of the aggregator's contract
                           * @param spender Address to which tokens will be approved
                           * @param method Selector of the function to be called in the aggregator's contract
                           * @param tokenFrom Token to be swapped
                           * @param tokenTo Token to be received
                           * @param amountFrom Amount of tokenFrom to swap
                           * @param amountTo Minimum amount of tokenTo to receive
                           * @param data Data used for the call made to the aggregator's contract
                           */
                          function swap(
                              address payable recipient,
                              address aggregator,
                              address spender,
                              bytes4 method,
                              IERC20 tokenFrom,
                              IERC20 tokenTo,
                              uint256 amountFrom,
                              uint256 amountTo,
                              bytes calldata data
                          ) external payable {
                              require(tokenFrom != tokenTo, "TOKEN_PAIR_INVALID");
                              if (address(tokenFrom) != Constants.ETH) {
                                  _approveSpender(tokenFrom, spender, amountFrom);
                              }
                              // We always forward msg.value as it may be necessary to pay fees
                              bytes memory encodedData = abi.encodePacked(method, data);
                              aggregator.functionCallWithValue(encodedData, msg.value);
                              // Transfer remaining balance of tokenFrom to sender
                              if (address(tokenFrom) != Constants.ETH) {
                                  uint256 balance = tokenFrom.balanceOf(address(this));
                                  _transfer(tokenFrom, balance, recipient);
                              }
                              uint256 weiBalance = address(this).balance;
                              // Transfer remaining balance of tokenTo to sender
                              if (address(tokenTo) != Constants.ETH) {
                                  uint256 balance = tokenTo.balanceOf(address(this));
                                  require(balance >= amountTo, "INSUFFICIENT_AMOUNT");
                                  _transfer(tokenTo, balance, recipient);
                              } else {
                                  // If tokenTo == ETH, then check that the remaining ETH balance >= amountTo
                                  require(weiBalance >= amountTo, "INSUFFICIENT_AMOUNT");
                              }
                              // If there are unused fees or if tokenTo is ETH, transfer to sender
                              if (weiBalance > 0) {
                                  recipient.sendValue(weiBalance);
                              }
                          }
                          /**
                           * @dev Transfers token to sender if amount > 0
                           * @param token IERC20 token to transfer to sender
                           * @param amount Amount of token to transfer
                           * @param recipient Address that will receive the tokens
                           */
                          function _transfer(
                              IERC20 token,
                              uint256 amount,
                              address recipient
                          ) internal {
                              if (amount > 0) {
                                  token.safeTransfer(recipient, amount);
                              }
                          }
                          // https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol
                          /**
                           * @dev Approves max amount of token to the spender if the allowance is lower than amount
                           * @param token The ERC20 token to approve
                           * @param spender Address to which funds will be approved
                           * @param amount Amount used to compare current allowance
                           */
                          function _approveSpender(
                              IERC20 token,
                              address spender,
                              uint256 amount
                          ) internal {
                              // If allowance is not enough, approve max possible amount
                              uint256 allowance = token.allowance(address(this), spender);
                              if (allowance < amount) {
                                  bytes memory returndata = address(token).functionCall(
                                      abi.encodeWithSelector(
                                          token.approve.selector,
                                          spender,
                                          type(uint256).max
                                      )
                                  );
                                  if (returndata.length > 0) {
                                      // Return data is optional
                                      require(abi.decode(returndata, (bool)), "APPROVAL_FAILED");
                                  }
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      /**
                       * @dev Interface of the ERC20 standard as defined in the EIP.
                       */
                      interface IERC20 {
                          /**
                           * @dev Returns the amount of tokens in existence.
                           */
                          function totalSupply() external view returns (uint256);
                          /**
                           * @dev Returns the amount of tokens owned by `account`.
                           */
                          function balanceOf(address account) external view returns (uint256);
                          /**
                           * @dev Moves `amount` tokens from the caller's account to `recipient`.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * Emits a {Transfer} event.
                           */
                          function transfer(address recipient, uint256 amount) external returns (bool);
                          /**
                           * @dev Returns the remaining number of tokens that `spender` will be
                           * allowed to spend on behalf of `owner` through {transferFrom}. This is
                           * zero by default.
                           *
                           * This value changes when {approve} or {transferFrom} are called.
                           */
                          function allowance(address owner, address spender) external view returns (uint256);
                          /**
                           * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * IMPORTANT: Beware that changing an allowance with this method brings the risk
                           * that someone may use both the old and the new allowance by unfortunate
                           * transaction ordering. One possible solution to mitigate this race
                           * condition is to first reduce the spender's allowance to 0 and set the
                           * desired value afterwards:
                           * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
                           *
                           * Emits an {Approval} event.
                           */
                          function approve(address spender, uint256 amount) external returns (bool);
                          /**
                           * @dev Moves `amount` tokens from `sender` to `recipient` using the
                           * allowance mechanism. `amount` is then deducted from the caller's
                           * allowance.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * Emits a {Transfer} event.
                           */
                          function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
                          /**
                           * @dev Emitted when `value` tokens are moved from one account (`from`) to
                           * another (`to`).
                           *
                           * Note that `value` may be zero.
                           */
                          event Transfer(address indexed from, address indexed to, uint256 value);
                          /**
                           * @dev Emitted when the allowance of a `spender` for an `owner` is set by
                           * a call to {approve}. `value` is the new allowance.
                           */
                          event Approval(address indexed owner, address indexed spender, uint256 value);
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      import "./IERC20.sol";
                      import "../../math/SafeMath.sol";
                      import "../../utils/Address.sol";
                      /**
                       * @title SafeERC20
                       * @dev Wrappers around ERC20 operations that throw on failure (when the token
                       * contract returns false). Tokens that return no value (and instead revert or
                       * throw on failure) are also supported, non-reverting calls are assumed to be
                       * successful.
                       * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
                       * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
                       */
                      library SafeERC20 {
                          using SafeMath for uint256;
                          using Address for address;
                          function safeTransfer(IERC20 token, address to, uint256 value) internal {
                              _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
                          }
                          function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
                              _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
                          }
                          /**
                           * @dev Deprecated. This function has issues similar to the ones found in
                           * {IERC20-approve}, and its usage is discouraged.
                           *
                           * Whenever possible, use {safeIncreaseAllowance} and
                           * {safeDecreaseAllowance} instead.
                           */
                          function safeApprove(IERC20 token, address spender, uint256 value) internal {
                              // safeApprove should only be called when setting an initial allowance,
                              // or when resetting it to zero. To increase and decrease it, use
                              // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
                              // solhint-disable-next-line max-line-length
                              require((value == 0) || (token.allowance(address(this), spender) == 0),
                                  "SafeERC20: approve from non-zero to non-zero allowance"
                              );
                              _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
                          }
                          function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
                              uint256 newAllowance = token.allowance(address(this), spender).add(value);
                              _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
                          }
                          function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
                              uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
                              _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
                          }
                          /**
                           * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
                           * on the return value: the return value is optional (but if data is returned, it must not be false).
                           * @param token The token targeted by the call.
                           * @param data The call data (encoded using abi.encode or one of its variants).
                           */
                          function _callOptionalReturn(IERC20 token, bytes memory data) private {
                              // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
                              // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
                              // the target address contains contract code and also asserts for success in the low-level call.
                              bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
                              if (returndata.length > 0) { // Return data is optional
                                  // solhint-disable-next-line max-line-length
                                  require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      /**
                       * @dev Wrappers over Solidity's arithmetic operations with added overflow
                       * checks.
                       *
                       * Arithmetic operations in Solidity wrap on overflow. This can easily result
                       * in bugs, because programmers usually assume that an overflow raises an
                       * error, which is the standard behavior in high level programming languages.
                       * `SafeMath` restores this intuition by reverting the transaction when an
                       * operation overflows.
                       *
                       * Using this library instead of the unchecked operations eliminates an entire
                       * class of bugs, so it's recommended to use it always.
                       */
                      library SafeMath {
                          /**
                           * @dev Returns the addition of two unsigned integers, reverting on
                           * overflow.
                           *
                           * Counterpart to Solidity's `+` operator.
                           *
                           * Requirements:
                           *
                           * - Addition cannot overflow.
                           */
                          function add(uint256 a, uint256 b) internal pure returns (uint256) {
                              uint256 c = a + b;
                              require(c >= a, "SafeMath: addition overflow");
                              return c;
                          }
                          /**
                           * @dev Returns the subtraction of two unsigned integers, reverting on
                           * overflow (when the result is negative).
                           *
                           * Counterpart to Solidity's `-` operator.
                           *
                           * Requirements:
                           *
                           * - Subtraction cannot overflow.
                           */
                          function sub(uint256 a, uint256 b) internal pure returns (uint256) {
                              return sub(a, b, "SafeMath: subtraction overflow");
                          }
                          /**
                           * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
                           * overflow (when the result is negative).
                           *
                           * Counterpart to Solidity's `-` operator.
                           *
                           * Requirements:
                           *
                           * - Subtraction cannot overflow.
                           */
                          function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
                              require(b <= a, errorMessage);
                              uint256 c = a - b;
                              return c;
                          }
                          /**
                           * @dev Returns the multiplication of two unsigned integers, reverting on
                           * overflow.
                           *
                           * Counterpart to Solidity's `*` operator.
                           *
                           * Requirements:
                           *
                           * - Multiplication cannot overflow.
                           */
                          function mul(uint256 a, uint256 b) internal pure returns (uint256) {
                              // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
                              // benefit is lost if 'b' is also tested.
                              // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
                              if (a == 0) {
                                  return 0;
                              }
                              uint256 c = a * b;
                              require(c / a == b, "SafeMath: multiplication overflow");
                              return c;
                          }
                          /**
                           * @dev Returns the integer division of two unsigned integers. Reverts on
                           * division by zero. The result is rounded towards zero.
                           *
                           * Counterpart to Solidity's `/` operator. Note: this function uses a
                           * `revert` opcode (which leaves remaining gas untouched) while Solidity
                           * uses an invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function div(uint256 a, uint256 b) internal pure returns (uint256) {
                              return div(a, b, "SafeMath: division by zero");
                          }
                          /**
                           * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
                           * division by zero. The result is rounded towards zero.
                           *
                           * Counterpart to Solidity's `/` operator. Note: this function uses a
                           * `revert` opcode (which leaves remaining gas untouched) while Solidity
                           * uses an invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
                              require(b > 0, errorMessage);
                              uint256 c = a / b;
                              // assert(a == b * c + a % b); // There is no case in which this doesn't hold
                              return c;
                          }
                          /**
                           * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
                           * Reverts when dividing by zero.
                           *
                           * Counterpart to Solidity's `%` operator. This function uses a `revert`
                           * opcode (which leaves remaining gas untouched) while Solidity uses an
                           * invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function mod(uint256 a, uint256 b) internal pure returns (uint256) {
                              return mod(a, b, "SafeMath: modulo by zero");
                          }
                          /**
                           * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
                           * Reverts with custom message when dividing by zero.
                           *
                           * Counterpart to Solidity's `%` operator. This function uses a `revert`
                           * opcode (which leaves remaining gas untouched) while Solidity uses an
                           * invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
                              require(b != 0, errorMessage);
                              return a % b;
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.2;
                      /**
                       * @dev Collection of functions related to the address type
                       */
                      library Address {
                          /**
                           * @dev Returns true if `account` is a contract.
                           *
                           * [IMPORTANT]
                           * ====
                           * It is unsafe to assume that an address for which this function returns
                           * false is an externally-owned account (EOA) and not a contract.
                           *
                           * Among others, `isContract` will return false for the following
                           * types of addresses:
                           *
                           *  - an externally-owned account
                           *  - a contract in construction
                           *  - an address where a contract will be created
                           *  - an address where a contract lived, but was destroyed
                           * ====
                           */
                          function isContract(address account) internal view returns (bool) {
                              // This method relies in extcodesize, which returns 0 for contracts in
                              // construction, since the code is only stored at the end of the
                              // constructor execution.
                              uint256 size;
                              // solhint-disable-next-line no-inline-assembly
                              assembly { size := extcodesize(account) }
                              return size > 0;
                          }
                          /**
                           * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
                           * `recipient`, forwarding all available gas and reverting on errors.
                           *
                           * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
                           * of certain opcodes, possibly making contracts go over the 2300 gas limit
                           * imposed by `transfer`, making them unable to receive funds via
                           * `transfer`. {sendValue} removes this limitation.
                           *
                           * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
                           *
                           * IMPORTANT: because control is transferred to `recipient`, care must be
                           * taken to not create reentrancy vulnerabilities. Consider using
                           * {ReentrancyGuard} or the
                           * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
                           */
                          function sendValue(address payable recipient, uint256 amount) internal {
                              require(address(this).balance >= amount, "Address: insufficient balance");
                              // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
                              (bool success, ) = recipient.call{ value: amount }("");
                              require(success, "Address: unable to send value, recipient may have reverted");
                          }
                          /**
                           * @dev Performs a Solidity function call using a low level `call`. A
                           * plain`call` is an unsafe replacement for a function call: use this
                           * function instead.
                           *
                           * If `target` reverts with a revert reason, it is bubbled up by this
                           * function (like regular Solidity function calls).
                           *
                           * Returns the raw returned data. To convert to the expected return value,
                           * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
                           *
                           * Requirements:
                           *
                           * - `target` must be a contract.
                           * - calling `target` with `data` must not revert.
                           *
                           * _Available since v3.1._
                           */
                          function functionCall(address target, bytes memory data) internal returns (bytes memory) {
                            return functionCall(target, data, "Address: low-level call failed");
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
                           * `errorMessage` as a fallback revert reason when `target` reverts.
                           *
                           * _Available since v3.1._
                           */
                          function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
                              return _functionCallWithValue(target, data, 0, errorMessage);
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
                           * but also transferring `value` wei to `target`.
                           *
                           * Requirements:
                           *
                           * - the calling contract must have an ETH balance of at least `value`.
                           * - the called Solidity function must be `payable`.
                           *
                           * _Available since v3.1._
                           */
                          function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
                              return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
                          }
                          /**
                           * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
                           * with `errorMessage` as a fallback revert reason when `target` reverts.
                           *
                           * _Available since v3.1._
                           */
                          function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
                              require(address(this).balance >= value, "Address: insufficient balance for call");
                              return _functionCallWithValue(target, data, value, errorMessage);
                          }
                          function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
                              require(isContract(target), "Address: call to non-contract");
                              // solhint-disable-next-line avoid-low-level-calls
                              (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
                              if (success) {
                                  return returndata;
                              } else {
                                  // Look for revert reason and bubble it up if present
                                  if (returndata.length > 0) {
                                      // The easiest way to bubble the revert reason is using memory via assembly
                                      // solhint-disable-next-line no-inline-assembly
                                      assembly {
                                          let returndata_size := mload(returndata)
                                          revert(add(32, returndata), returndata_size)
                                      }
                                  } else {
                                      revert(errorMessage);
                                  }
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      library Constants {
                          address internal constant ETH = 0x0000000000000000000000000000000000000000;
                      }
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      import "@openzeppelin/contracts/math/SafeMath.sol";
                      import "@openzeppelin/contracts/utils/Address.sol";
                      import "../Constants.sol";
                      contract FeeCommonAdapter {
                          using SafeERC20 for IERC20;
                          using Address for address;
                          using Address for address payable;
                          using SafeMath for uint256;
                          // solhint-disable-next-line var-name-mixedcase
                          address payable public immutable FEE_WALLET;
                          constructor(address payable feeWallet) public {
                              FEE_WALLET = feeWallet;
                          }
                          /**
                           * @dev Performs a swap
                           * @param recipient The original msg.sender performing the swap
                           * @param aggregator Address of the aggregator's contract
                           * @param spender Address to which tokens will be approved
                           * @param method Selector of the function to be called in the aggregator's contract
                           * @param tokenFrom Token to be swapped
                           * @param tokenTo Token to be received
                           * @param amountFrom Amount of tokenFrom to swap
                           * @param amountTo Minimum amount of tokenTo to receive
                           * @param data Data used for the call made to the aggregator's contract
                           * @param fee Amount of tokenFrom sent to the fee wallet
                           */
                          function swap(
                              address payable recipient,
                              address aggregator,
                              address spender,
                              bytes4 method,
                              IERC20 tokenFrom,
                              IERC20 tokenTo,
                              uint256 amountFrom,
                              uint256 amountTo,
                              bytes calldata data,
                              uint256 fee
                          ) external payable {
                              require(tokenFrom != tokenTo, "TOKEN_PAIR_INVALID");
                              if (address(tokenFrom) == Constants.ETH) {
                                  FEE_WALLET.sendValue(fee);
                              } else {
                                  _transfer(tokenFrom, fee, FEE_WALLET);
                                  _approveSpender(tokenFrom, spender, amountFrom);
                              }
                              // We always forward msg.value as it may be necessary to pay fees
                              aggregator.functionCallWithValue(
                                  abi.encodePacked(method, data),
                                  address(this).balance
                              );
                              // Transfer remaining balance of tokenFrom to sender
                              if (address(tokenFrom) != Constants.ETH) {
                                  _transfer(tokenFrom, tokenFrom.balanceOf(address(this)), recipient);
                              }
                              uint256 weiBalance = address(this).balance;
                              // Transfer remaining balance of tokenTo to sender
                              if (address(tokenTo) != Constants.ETH) {
                                  uint256 balance = tokenTo.balanceOf(address(this));
                                  require(balance >= amountTo, "INSUFFICIENT_AMOUNT");
                                  _transfer(tokenTo, balance, recipient);
                              } else {
                                  // If tokenTo == ETH, then check that the remaining ETH balance >= amountTo
                                  require(weiBalance >= amountTo, "INSUFFICIENT_AMOUNT");
                              }
                              // If there are unused fees or if tokenTo is ETH, transfer to sender
                              if (weiBalance > 0) {
                                  recipient.sendValue(weiBalance);
                              }
                          }
                          /**
                           * @dev Transfers token to sender if amount > 0
                           * @param token IERC20 token to transfer to sender
                           * @param amount Amount of token to transfer
                           * @param recipient Address that will receive the tokens
                           */
                          function _transfer(
                              IERC20 token,
                              uint256 amount,
                              address recipient
                          ) internal {
                              if (amount > 0) {
                                  token.safeTransfer(recipient, amount);
                              }
                          }
                          // https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol
                          /**
                           * @dev Approves max amount of token to the spender if the allowance is lower than amount
                           * @param token The ERC20 token to approve
                           * @param spender Address to which funds will be approved
                           * @param amount Amount used to compare current allowance
                           */
                          function _approveSpender(
                              IERC20 token,
                              address spender,
                              uint256 amount
                          ) internal {
                              // If allowance is not enough, approve max possible amount
                              uint256 allowance = token.allowance(address(this), spender);
                              if (allowance < amount) {
                                  bytes memory returndata = address(token).functionCall(
                                      abi.encodeWithSelector(
                                          token.approve.selector,
                                          spender,
                                          type(uint256).max
                                      )
                                  );
                                  if (returndata.length > 0) {
                                      // Return data is optional
                                      require(abi.decode(returndata, (bool)), "APPROVAL_FAILED");
                                  }
                              }
                          }
                      }
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      import "@openzeppelin/contracts/math/SafeMath.sol";
                      import "@openzeppelin/contracts/utils/Address.sol";
                      import "../Constants.sol";
                      import "../IWETH.sol";
                      contract FeeWethAdapter {
                          using SafeERC20 for IERC20;
                          using Address for address;
                          using Address for address payable;
                          using SafeMath for uint256;
                          IWETH public immutable weth;
                          // solhint-disable-next-line var-name-mixedcase
                          address payable public immutable FEE_WALLET;
                          constructor(IWETH _weth, address payable feeWallet) public {
                              weth = _weth;
                              FEE_WALLET = feeWallet;
                          }
                          /**
                           * @dev Performs a swap
                           * @param recipient The original msg.sender performing the swap
                           * @param aggregator Address of the aggregator's contract
                           * @param spender Address to which tokens will be approved
                           * @param method Selector of the function to be called in the aggregator's contract
                           * @param tokenFrom Token to be swapped
                           * @param tokenTo Token to be received
                           * @param amountFrom Amount of tokenFrom to swap
                           * @param amountTo Minimum amount of tokenTo to receive
                           * @param data Data used for the call made to the aggregator's contract
                           * @param fee Amount of tokenFrom sent to the fee wallet
                           */
                          function swap(
                              address payable recipient,
                              address aggregator,
                              address spender,
                              bytes4 method,
                              IERC20 tokenFrom,
                              IERC20 tokenTo,
                              uint256 amountFrom,
                              uint256 amountTo,
                              bytes calldata data,
                              uint256 fee
                          ) external payable {
                              require(tokenFrom != tokenTo, "TOKEN_PAIR_INVALID");
                              if (address(tokenFrom) == Constants.ETH) {
                                  FEE_WALLET.sendValue(fee);
                                  // If tokenFrom is ETH, msg.value = fee + amountFrom (total fee could be 0)
                                  // Can't deal with ETH, convert to WETH, the remaining balance will be the fee
                                  weth.deposit{value: amountFrom}();
                                  _approveSpender(weth, spender, amountFrom);
                              } else {
                                  _transfer(tokenFrom, fee, FEE_WALLET);
                                  // Otherwise capture tokens from sender
                                  _approveSpender(tokenFrom, spender, amountFrom);
                              }
                              // Perform the swap
                              aggregator.functionCallWithValue(
                                  abi.encodePacked(method, data),
                                  address(this).balance
                              );
                              // Transfer remaining balance of tokenFrom to sender
                              if (address(tokenFrom) != Constants.ETH) {
                                  _transfer(tokenFrom, tokenFrom.balanceOf(address(this)), recipient);
                              } else {
                                  // If using ETH, just unwrap any remaining WETH
                                  // At the end of this function all ETH will be transferred to the sender
                                  _unwrapWETH();
                              }
                              uint256 weiBalance = address(this).balance;
                              // Transfer remaining balance of tokenTo to sender
                              if (address(tokenTo) != Constants.ETH) {
                                  uint256 balance = tokenTo.balanceOf(address(this));
                                  require(balance >= amountTo, "INSUFFICIENT_AMOUNT");
                                  _transfer(tokenTo, balance, recipient);
                              } else {
                                  // If tokenTo == ETH, unwrap received WETH and add it to the wei balance,
                                  // then check that the remaining ETH balance >= amountTo
                                  // It is safe to not use safeMath as no one can have enough Ether to overflow
                                  weiBalance += _unwrapWETH();
                                  require(weiBalance >= amountTo, "INSUFFICIENT_AMOUNT");
                              }
                              // If there are unused fees or if tokenTo is ETH, transfer to sender
                              if (weiBalance > 0) {
                                  recipient.sendValue(weiBalance);
                              }
                          }
                          /**
                           * @dev Unwraps all available WETH into ETH
                           */
                          function _unwrapWETH() internal returns (uint256) {
                              uint256 balance = weth.balanceOf(address(this));
                              weth.withdraw(balance);
                              return balance;
                          }
                          /**
                           * @dev Transfers token to sender if amount > 0
                           * @param token IERC20 token to transfer to sender
                           * @param amount Amount of token to transfer
                           * @param recipient Address that will receive the tokens
                           */
                          function _transfer(
                              IERC20 token,
                              uint256 amount,
                              address recipient
                          ) internal {
                              if (amount > 0) {
                                  token.safeTransfer(recipient, amount);
                              }
                          }
                          // https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol
                          /**
                           * @dev Approves max amount of token to the spender if the allowance is lower than amount
                           * @param token The ERC20 token to approve
                           * @param spender Address to which funds will be approved
                           * @param amount Amount used to compare current allowance
                           */
                          function _approveSpender(
                              IERC20 token,
                              address spender,
                              uint256 amount
                          ) internal {
                              // If allowance is not enough, approve max possible amount
                              uint256 allowance = token.allowance(address(this), spender);
                              if (allowance < amount) {
                                  bytes memory returndata = address(token).functionCall(
                                      abi.encodeWithSelector(
                                          token.approve.selector,
                                          spender,
                                          type(uint256).max
                                      )
                                  );
                                  if (returndata.length > 0) {
                                      // Return data is optional
                                      require(abi.decode(returndata, (bool)), "APPROVAL_FAILED");
                                  }
                              }
                          }
                      }
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      interface IWETH is IERC20 {
                          function deposit() external payable;
                          function withdraw(uint256) external;
                      }
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      import "@openzeppelin/contracts/math/SafeMath.sol";
                      import "@openzeppelin/contracts/utils/Address.sol";
                      import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol";
                      import "../Constants.sol";
                      contract UniswapAdapter {
                          using SafeERC20 for IERC20;
                          using Address for address;
                          using Address for address payable;
                          using SafeMath for uint256;
                          // solhint-disable-next-line var-name-mixedcase
                          IUniswapV2Router02 public immutable UNISWAP;
                          // solhint-disable-next-line var-name-mixedcase
                          address payable public immutable FEE_WALLET;
                          constructor(address payable feeWallet, IUniswapV2Router02 uniswap) public {
                              FEE_WALLET = feeWallet;
                              UNISWAP = uniswap;
                          }
                          /**
                           * @dev Performs a swap
                           * @param recipient The original msg.sender performing the swap
                           * @param tokenFrom Token to be swapped
                           * @param tokenTo Token to be received
                           * @param amountFrom Amount of tokenFrom to swap
                           * @param amountTo Minimum amount of tokenTo to receive
                           * @param path Used by Uniswap
                           * @param deadline Timestamp at which the swap becomes invalid. Used by Uniswap
                           * @param feeOnTransfer Use `supportingFeeOnTransfer` Uniswap methods
                           * @param fee Amount of tokenFrom sent to the fee wallet
                           */
                          function swap(
                              address payable recipient,
                              IERC20 tokenFrom,
                              IERC20 tokenTo,
                              uint256 amountFrom,
                              uint256 amountTo,
                              address[] calldata path,
                              uint256 deadline,
                              bool feeOnTransfer,
                              uint256 fee
                          ) external payable {
                              require(tokenFrom != tokenTo, "TOKEN_PAIR_INVALID");
                              if (address(tokenFrom) == Constants.ETH) {
                                  FEE_WALLET.sendValue(fee);
                              } else {
                                  _transfer(tokenFrom, fee, FEE_WALLET);
                              }
                              if (address(tokenFrom) == Constants.ETH) {
                                  if (feeOnTransfer) {
                                      UNISWAP.swapExactETHForTokensSupportingFeeOnTransferTokens{
                                          value: address(this).balance
                                      }(amountTo, path, address(this), deadline);
                                  } else {
                                      UNISWAP.swapExactETHForTokens{value: address(this).balance}(
                                          amountTo,
                                          path,
                                          address(this),
                                          deadline
                                      );
                                  }
                              } else {
                                  _approveSpender(tokenFrom, address(UNISWAP), amountFrom);
                                  if (address(tokenTo) == Constants.ETH) {
                                      if (feeOnTransfer) {
                                          UNISWAP.swapExactTokensForETHSupportingFeeOnTransferTokens(
                                              amountFrom,
                                              amountTo,
                                              path,
                                              address(this),
                                              deadline
                                          );
                                      } else {
                                          UNISWAP.swapExactTokensForETH(
                                              amountFrom,
                                              amountTo,
                                              path,
                                              address(this),
                                              deadline
                                          );
                                      }
                                  } else {
                                      if (feeOnTransfer) {
                                          UNISWAP
                                              .swapExactTokensForTokensSupportingFeeOnTransferTokens(
                                              amountFrom,
                                              amountTo,
                                              path,
                                              address(this),
                                              deadline
                                          );
                                      } else {
                                          UNISWAP.swapExactTokensForTokens(
                                              amountFrom,
                                              amountTo,
                                              path,
                                              address(this),
                                              deadline
                                          );
                                      }
                                  }
                              }
                              // Transfer remaining balance of tokenFrom to sender
                              if (address(tokenFrom) != Constants.ETH) {
                                  _transfer(tokenFrom, tokenFrom.balanceOf(address(this)), recipient);
                              }
                              uint256 weiBalance = address(this).balance;
                              // Transfer remaining balance of tokenTo to sender
                              if (address(tokenTo) != Constants.ETH) {
                                  uint256 balance = tokenTo.balanceOf(address(this));
                                  require(balance >= amountTo, "INSUFFICIENT_AMOUNT");
                                  _transfer(tokenTo, balance, recipient);
                              } else {
                                  // If tokenTo == ETH, then check that the remaining ETH balance >= amountTo
                                  require(weiBalance >= amountTo, "INSUFFICIENT_AMOUNT");
                              }
                              // If there are unused fees or if tokenTo is ETH, transfer to sender
                              if (weiBalance > 0) {
                                  recipient.sendValue(weiBalance);
                              }
                          }
                          /**
                           * @dev Transfers token to sender if amount > 0
                           * @param token IERC20 token to transfer to sender
                           * @param amount Amount of token to transfer
                           * @param recipient Address that will receive the tokens
                           */
                          function _transfer(
                              IERC20 token,
                              uint256 amount,
                              address recipient
                          ) internal {
                              if (amount > 0) {
                                  token.safeTransfer(recipient, amount);
                              }
                          }
                          // https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol
                          /**
                           * @dev Approves max amount of token to the spender if the allowance is lower than amount
                           * @param token The ERC20 token to approve
                           * @param spender Address to which funds will be approved
                           * @param amount Amount used to compare current allowance
                           */
                          function _approveSpender(
                              IERC20 token,
                              address spender,
                              uint256 amount
                          ) internal {
                              // If allowance is not enough, approve max possible amount
                              uint256 allowance = token.allowance(address(this), spender);
                              if (allowance < amount) {
                                  bytes memory returndata = address(token).functionCall(
                                      abi.encodeWithSelector(
                                          token.approve.selector,
                                          spender,
                                          type(uint256).max
                                      )
                                  );
                                  if (returndata.length > 0) {
                                      // Return data is optional
                                      require(abi.decode(returndata, (bool)), "APPROVAL_FAILED");
                                  }
                              }
                          }
                      }
                      pragma solidity >=0.6.2;
                      import './IUniswapV2Router01.sol';
                      interface IUniswapV2Router02 is IUniswapV2Router01 {
                          function removeLiquidityETHSupportingFeeOnTransferTokens(
                              address token,
                              uint liquidity,
                              uint amountTokenMin,
                              uint amountETHMin,
                              address to,
                              uint deadline
                          ) external returns (uint amountETH);
                          function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
                              address token,
                              uint liquidity,
                              uint amountTokenMin,
                              uint amountETHMin,
                              address to,
                              uint deadline,
                              bool approveMax, uint8 v, bytes32 r, bytes32 s
                          ) external returns (uint amountETH);
                          function swapExactTokensForTokensSupportingFeeOnTransferTokens(
                              uint amountIn,
                              uint amountOutMin,
                              address[] calldata path,
                              address to,
                              uint deadline
                          ) external;
                          function swapExactETHForTokensSupportingFeeOnTransferTokens(
                              uint amountOutMin,
                              address[] calldata path,
                              address to,
                              uint deadline
                          ) external payable;
                          function swapExactTokensForETHSupportingFeeOnTransferTokens(
                              uint amountIn,
                              uint amountOutMin,
                              address[] calldata path,
                              address to,
                              uint deadline
                          ) external;
                      }
                      pragma solidity >=0.6.2;
                      interface IUniswapV2Router01 {
                          function factory() external pure returns (address);
                          function WETH() external pure returns (address);
                          function addLiquidity(
                              address tokenA,
                              address tokenB,
                              uint amountADesired,
                              uint amountBDesired,
                              uint amountAMin,
                              uint amountBMin,
                              address to,
                              uint deadline
                          ) external returns (uint amountA, uint amountB, uint liquidity);
                          function addLiquidityETH(
                              address token,
                              uint amountTokenDesired,
                              uint amountTokenMin,
                              uint amountETHMin,
                              address to,
                              uint deadline
                          ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
                          function removeLiquidity(
                              address tokenA,
                              address tokenB,
                              uint liquidity,
                              uint amountAMin,
                              uint amountBMin,
                              address to,
                              uint deadline
                          ) external returns (uint amountA, uint amountB);
                          function removeLiquidityETH(
                              address token,
                              uint liquidity,
                              uint amountTokenMin,
                              uint amountETHMin,
                              address to,
                              uint deadline
                          ) external returns (uint amountToken, uint amountETH);
                          function removeLiquidityWithPermit(
                              address tokenA,
                              address tokenB,
                              uint liquidity,
                              uint amountAMin,
                              uint amountBMin,
                              address to,
                              uint deadline,
                              bool approveMax, uint8 v, bytes32 r, bytes32 s
                          ) external returns (uint amountA, uint amountB);
                          function removeLiquidityETHWithPermit(
                              address token,
                              uint liquidity,
                              uint amountTokenMin,
                              uint amountETHMin,
                              address to,
                              uint deadline,
                              bool approveMax, uint8 v, bytes32 r, bytes32 s
                          ) external returns (uint amountToken, uint amountETH);
                          function swapExactTokensForTokens(
                              uint amountIn,
                              uint amountOutMin,
                              address[] calldata path,
                              address to,
                              uint deadline
                          ) external returns (uint[] memory amounts);
                          function swapTokensForExactTokens(
                              uint amountOut,
                              uint amountInMax,
                              address[] calldata path,
                              address to,
                              uint deadline
                          ) external returns (uint[] memory amounts);
                          function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
                              external
                              payable
                              returns (uint[] memory amounts);
                          function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
                              external
                              returns (uint[] memory amounts);
                          function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
                              external
                              returns (uint[] memory amounts);
                          function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
                              external
                              payable
                              returns (uint[] memory amounts);
                          function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
                          function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
                          function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
                          function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
                          function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
                      }
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      import "@openzeppelin/contracts/utils/Address.sol";
                      import "../Constants.sol";
                      import "../IWETH.sol";
                      contract WethAdapter {
                          using SafeERC20 for IERC20;
                          using Address for address;
                          using Address for address payable;
                          IWETH public immutable weth;
                          constructor(IWETH _weth) public {
                              weth = _weth;
                          }
                          /**
                           * @dev Performs a swap
                           * @param recipient The original msg.sender performing the swap
                           * @param aggregator Address of the aggregator's contract
                           * @param spender Address to which tokens will be approved
                           * @param method Selector of the function to be called in the aggregator's contract
                           * @param tokenFrom Token to be swapped
                           * @param tokenTo Token to be received
                           * @param amountFrom Amount of tokenFrom to swap
                           * @param amountTo Minimum amount of tokenTo to receive
                           * @param data Data used for the call made to the aggregator's contract
                           */
                          function swap(
                              address payable recipient,
                              address aggregator,
                              address spender,
                              bytes4 method,
                              IERC20 tokenFrom,
                              IERC20 tokenTo,
                              uint256 amountFrom,
                              uint256 amountTo,
                              bytes calldata data
                          ) external payable {
                              require(tokenFrom != tokenTo, "TOKEN_PAIR_INVALID");
                              if (address(tokenFrom) == Constants.ETH) {
                                  // If tokenFrom is ETH, msg.value = fee + amountFrom (total fee could be 0)
                                  // Can't deal with ETH, convert to WETH, the remaining balance will be the fee
                                  weth.deposit{value: amountFrom}();
                                  _approveSpender(weth, spender, amountFrom);
                              } else {
                                  // Otherwise capture tokens from sender
                                  _approveSpender(tokenFrom, spender, amountFrom);
                              }
                              // Perform the swap
                              aggregator.functionCallWithValue(
                                  abi.encodePacked(method, data),
                                  address(this).balance
                              );
                              // Transfer remaining balance of tokenFrom to sender
                              if (address(tokenFrom) != Constants.ETH) {
                                  _transfer(tokenFrom, tokenFrom.balanceOf(address(this)), recipient);
                              } else {
                                  // If using ETH, just unwrap any remaining WETH
                                  // At the end of this function all ETH will be transferred to the sender
                                  _unwrapWETH();
                              }
                              uint256 weiBalance = address(this).balance;
                              // Transfer remaining balance of tokenTo to sender
                              if (address(tokenTo) != Constants.ETH) {
                                  uint256 balance = tokenTo.balanceOf(address(this));
                                  require(balance >= amountTo, "INSUFFICIENT_AMOUNT");
                                  _transfer(tokenTo, balance, recipient);
                              } else {
                                  // If tokenTo == ETH, unwrap received WETH and add it to the wei balance,
                                  // then check that the remaining ETH balance >= amountTo
                                  // It is safe to not use safeMath as no one can have enough Ether to overflow
                                  weiBalance += _unwrapWETH();
                                  require(weiBalance >= amountTo, "INSUFFICIENT_AMOUNT");
                              }
                              // If there are unused fees or if tokenTo is ETH, transfer to sender
                              if (weiBalance > 0) {
                                  recipient.sendValue(weiBalance);
                              }
                          }
                          /**
                           * @dev Unwraps all available WETH into ETH
                           */
                          function _unwrapWETH() internal returns (uint256) {
                              uint256 balance = weth.balanceOf(address(this));
                              weth.withdraw(balance);
                              return balance;
                          }
                          /**
                           * @dev Transfers token to sender if amount > 0
                           * @param token IERC20 token to transfer to sender
                           * @param amount Amount of token to transfer
                           * @param recipient Address that will receive the tokens
                           */
                          function _transfer(
                              IERC20 token,
                              uint256 amount,
                              address recipient
                          ) internal {
                              if (amount > 0) {
                                  token.safeTransfer(recipient, amount);
                              }
                          }
                          // https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol
                          /**
                           * @dev Approves max amount of token to the spender if the allowance is lower than amount
                           * @param token The ERC20 token to approve
                           * @param spender Address to which funds will be approved
                           * @param amount Amount used to compare current allowance
                           */
                          function _approveSpender(
                              IERC20 token,
                              address spender,
                              uint256 amount
                          ) internal {
                              // If allowance is not enough, approve max possible amount
                              uint256 allowance = token.allowance(address(this), spender);
                              if (allowance < amount) {
                                  bytes memory returndata = address(token).functionCall(
                                      abi.encodeWithSelector(
                                          token.approve.selector,
                                          spender,
                                          type(uint256).max
                                      )
                                  );
                                  if (returndata.length > 0) {
                                      // Return data is optional
                                      require(abi.decode(returndata, (bool)), "APPROVAL_FAILED");
                                  }
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      interface ICHI is IERC20 {
                          function freeUpTo(uint256 value) external returns (uint256);
                          function freeFromUpTo(
                              address from,
                              uint256 value
                          ) external returns (uint256);
                          function mint(uint256 value) external;
                      }
                        
                      // SPDX-License-Identifier: UNLICENSED
                      pragma solidity ^0.6.0;
                      // We import the contract so truffle compiles it, and we have the ABI
                      // available when working from truffle console.
                      import "@openzeppelin/contracts/token/ERC20/ERC20.sol"; //helpers// SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      import "../../GSN/Context.sol";
                      import "./IERC20.sol";
                      import "../../math/SafeMath.sol";
                      import "../../utils/Address.sol";
                      /**
                       * @dev Implementation of the {IERC20} interface.
                       *
                       * This implementation is agnostic to the way tokens are created. This means
                       * that a supply mechanism has to be added in a derived contract using {_mint}.
                       * For a generic mechanism see {ERC20PresetMinterPauser}.
                       *
                       * TIP: For a detailed writeup see our guide
                       * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
                       * to implement supply mechanisms].
                       *
                       * We have followed general OpenZeppelin guidelines: functions revert instead
                       * of returning `false` on failure. This behavior is nonetheless conventional
                       * and does not conflict with the expectations of ERC20 applications.
                       *
                       * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
                       * This allows applications to reconstruct the allowance for all accounts just
                       * by listening to said events. Other implementations of the EIP may not emit
                       * these events, as it isn't required by the specification.
                       *
                       * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
                       * functions have been added to mitigate the well-known issues around setting
                       * allowances. See {IERC20-approve}.
                       */
                      contract ERC20 is Context, IERC20 {
                          using SafeMath for uint256;
                          using Address for address;
                          mapping (address => uint256) private _balances;
                          mapping (address => mapping (address => uint256)) private _allowances;
                          uint256 private _totalSupply;
                          string private _name;
                          string private _symbol;
                          uint8 private _decimals;
                          /**
                           * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
                           * a default value of 18.
                           *
                           * To select a different value for {decimals}, use {_setupDecimals}.
                           *
                           * All three of these values are immutable: they can only be set once during
                           * construction.
                           */
                          constructor (string memory name, string memory symbol) public {
                              _name = name;
                              _symbol = symbol;
                              _decimals = 18;
                          }
                          /**
                           * @dev Returns the name of the token.
                           */
                          function name() public view returns (string memory) {
                              return _name;
                          }
                          /**
                           * @dev Returns the symbol of the token, usually a shorter version of the
                           * name.
                           */
                          function symbol() public view returns (string memory) {
                              return _symbol;
                          }
                          /**
                           * @dev Returns the number of decimals used to get its user representation.
                           * For example, if `decimals` equals `2`, a balance of `505` tokens should
                           * be displayed to a user as `5,05` (`505 / 10 ** 2`).
                           *
                           * Tokens usually opt for a value of 18, imitating the relationship between
                           * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
                           * called.
                           *
                           * NOTE: This information is only used for _display_ purposes: it in
                           * no way affects any of the arithmetic of the contract, including
                           * {IERC20-balanceOf} and {IERC20-transfer}.
                           */
                          function decimals() public view returns (uint8) {
                              return _decimals;
                          }
                          /**
                           * @dev See {IERC20-totalSupply}.
                           */
                          function totalSupply() public view override returns (uint256) {
                              return _totalSupply;
                          }
                          /**
                           * @dev See {IERC20-balanceOf}.
                           */
                          function balanceOf(address account) public view override returns (uint256) {
                              return _balances[account];
                          }
                          /**
                           * @dev See {IERC20-transfer}.
                           *
                           * Requirements:
                           *
                           * - `recipient` cannot be the zero address.
                           * - the caller must have a balance of at least `amount`.
                           */
                          function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
                              _transfer(_msgSender(), recipient, amount);
                              return true;
                          }
                          /**
                           * @dev See {IERC20-allowance}.
                           */
                          function allowance(address owner, address spender) public view virtual override returns (uint256) {
                              return _allowances[owner][spender];
                          }
                          /**
                           * @dev See {IERC20-approve}.
                           *
                           * Requirements:
                           *
                           * - `spender` cannot be the zero address.
                           */
                          function approve(address spender, uint256 amount) public virtual override returns (bool) {
                              _approve(_msgSender(), spender, amount);
                              return true;
                          }
                          /**
                           * @dev See {IERC20-transferFrom}.
                           *
                           * Emits an {Approval} event indicating the updated allowance. This is not
                           * required by the EIP. See the note at the beginning of {ERC20};
                           *
                           * Requirements:
                           * - `sender` and `recipient` cannot be the zero address.
                           * - `sender` must have a balance of at least `amount`.
                           * - the caller must have allowance for ``sender``'s tokens of at least
                           * `amount`.
                           */
                          function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
                              _transfer(sender, recipient, amount);
                              _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
                              return true;
                          }
                          /**
                           * @dev Atomically increases the allowance granted to `spender` by the caller.
                           *
                           * This is an alternative to {approve} that can be used as a mitigation for
                           * problems described in {IERC20-approve}.
                           *
                           * Emits an {Approval} event indicating the updated allowance.
                           *
                           * Requirements:
                           *
                           * - `spender` cannot be the zero address.
                           */
                          function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
                              _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
                              return true;
                          }
                          /**
                           * @dev Atomically decreases the allowance granted to `spender` by the caller.
                           *
                           * This is an alternative to {approve} that can be used as a mitigation for
                           * problems described in {IERC20-approve}.
                           *
                           * Emits an {Approval} event indicating the updated allowance.
                           *
                           * Requirements:
                           *
                           * - `spender` cannot be the zero address.
                           * - `spender` must have allowance for the caller of at least
                           * `subtractedValue`.
                           */
                          function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
                              _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
                              return true;
                          }
                          /**
                           * @dev Moves tokens `amount` from `sender` to `recipient`.
                           *
                           * This is internal function is equivalent to {transfer}, and can be used to
                           * e.g. implement automatic token fees, slashing mechanisms, etc.
                           *
                           * Emits a {Transfer} event.
                           *
                           * Requirements:
                           *
                           * - `sender` cannot be the zero address.
                           * - `recipient` cannot be the zero address.
                           * - `sender` must have a balance of at least `amount`.
                           */
                          function _transfer(address sender, address recipient, uint256 amount) internal virtual {
                              require(sender != address(0), "ERC20: transfer from the zero address");
                              require(recipient != address(0), "ERC20: transfer to the zero address");
                              _beforeTokenTransfer(sender, recipient, amount);
                              _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
                              _balances[recipient] = _balances[recipient].add(amount);
                              emit Transfer(sender, recipient, amount);
                          }
                          /** @dev Creates `amount` tokens and assigns them to `account`, increasing
                           * the total supply.
                           *
                           * Emits a {Transfer} event with `from` set to the zero address.
                           *
                           * Requirements
                           *
                           * - `to` cannot be the zero address.
                           */
                          function _mint(address account, uint256 amount) internal virtual {
                              require(account != address(0), "ERC20: mint to the zero address");
                              _beforeTokenTransfer(address(0), account, amount);
                              _totalSupply = _totalSupply.add(amount);
                              _balances[account] = _balances[account].add(amount);
                              emit Transfer(address(0), account, amount);
                          }
                          /**
                           * @dev Destroys `amount` tokens from `account`, reducing the
                           * total supply.
                           *
                           * Emits a {Transfer} event with `to` set to the zero address.
                           *
                           * Requirements
                           *
                           * - `account` cannot be the zero address.
                           * - `account` must have at least `amount` tokens.
                           */
                          function _burn(address account, uint256 amount) internal virtual {
                              require(account != address(0), "ERC20: burn from the zero address");
                              _beforeTokenTransfer(account, address(0), amount);
                              _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
                              _totalSupply = _totalSupply.sub(amount);
                              emit Transfer(account, address(0), amount);
                          }
                          /**
                           * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
                           *
                           * This internal function is equivalent to `approve`, and can be used to
                           * e.g. set automatic allowances for certain subsystems, etc.
                           *
                           * Emits an {Approval} event.
                           *
                           * Requirements:
                           *
                           * - `owner` cannot be the zero address.
                           * - `spender` cannot be the zero address.
                           */
                          function _approve(address owner, address spender, uint256 amount) internal virtual {
                              require(owner != address(0), "ERC20: approve from the zero address");
                              require(spender != address(0), "ERC20: approve to the zero address");
                              _allowances[owner][spender] = amount;
                              emit Approval(owner, spender, amount);
                          }
                          /**
                           * @dev Sets {decimals} to a value other than the default one of 18.
                           *
                           * WARNING: This function should only be called from the constructor. Most
                           * applications that interact with token contracts will not expect
                           * {decimals} to ever change, and may work incorrectly if it does.
                           */
                          function _setupDecimals(uint8 decimals_) internal {
                              _decimals = decimals_;
                          }
                          /**
                           * @dev Hook that is called before any transfer of tokens. This includes
                           * minting and burning.
                           *
                           * Calling conditions:
                           *
                           * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
                           * will be to transferred to `to`.
                           * - when `from` is zero, `amount` tokens will be minted for `to`.
                           * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
                           * - `from` and `to` are never both zero.
                           *
                           * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
                           */
                          function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      /*
                       * @dev Provides information about the current execution context, including the
                       * sender of the transaction and its data. While these are generally available
                       * via msg.sender and msg.data, they should not be accessed in such a direct
                       * manner, since when dealing with GSN meta-transactions the account sending and
                       * paying for execution may not be the actual sender (as far as an application
                       * is concerned).
                       *
                       * This contract is only required for intermediate, library-like contracts.
                       */
                      abstract contract Context {
                          function _msgSender() internal view virtual returns (address payable) {
                              return msg.sender;
                          }
                          function _msgData() internal view virtual returns (bytes memory) {
                              this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
                              return msg.data;
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/access/Ownable.sol";
                      import "@openzeppelin/contracts/utils/Pausable.sol";
                      import "@openzeppelin/contracts/utils/Address.sol";
                      import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      import "./ICHI.sol";
                      import "./Spender.sol";
                      /**
                       * @title MetaSwap
                       */
                      contract MetaSwap is Ownable, Pausable, ReentrancyGuard {
                          using SafeERC20 for IERC20;
                          using Address for address;
                          using Address for address payable;
                          struct Adapter {
                              address addr; // adapter's address
                              bytes4 selector;
                              bytes data; // adapter's fixed data
                          }
                          ICHI public immutable chi;
                          Spender public immutable spender;
                          // Mapping of aggregatorId to aggregator
                          mapping(string => Adapter) public adapters;
                          mapping(string => bool) public adapterRemoved;
                          event AdapterSet(
                              string indexed aggregatorId,
                              address indexed addr,
                              bytes4 selector,
                              bytes data
                          );
                          event AdapterRemoved(string indexed aggregatorId);
                          event Swap(string indexed aggregatorId, address indexed sender);
                          constructor(ICHI _chi) public {
                              chi = _chi;
                              spender = new Spender();
                          }
                          /**
                           * @dev Sets the adapter for an aggregator. It can't be changed later.
                           * @param aggregatorId Aggregator's identifier
                           * @param addr Address of the contract that contains the logic for this aggregator
                           * @param selector The function selector of the swap function in the adapter
                           * @param data Fixed abi encoded data the will be passed in each delegatecall made to the adapter
                           */
                          function setAdapter(
                              string calldata aggregatorId,
                              address addr,
                              bytes4 selector,
                              bytes calldata data
                          ) external onlyOwner {
                              require(addr.isContract(), "ADAPTER_IS_NOT_A_CONTRACT");
                              require(!adapterRemoved[aggregatorId], "ADAPTER_REMOVED");
                              Adapter storage adapter = adapters[aggregatorId];
                              require(adapter.addr == address(0), "ADAPTER_EXISTS");
                              adapter.addr = addr;
                              adapter.selector = selector;
                              adapter.data = data;
                              emit AdapterSet(aggregatorId, addr, selector, data);
                          }
                          /**
                           * @dev Removes the adapter for an existing aggregator. This can't be undone.
                           * @param aggregatorId Aggregator's identifier
                           */
                          function removeAdapter(string calldata aggregatorId) external onlyOwner {
                              require(
                                  adapters[aggregatorId].addr != address(0),
                                  "ADAPTER_DOES_NOT_EXIST"
                              );
                              delete adapters[aggregatorId];
                              adapterRemoved[aggregatorId] = true;
                              emit AdapterRemoved(aggregatorId);
                          }
                          /**
                           * @dev Performs a swap
                           * @param aggregatorId Identifier of the aggregator to be used for the swap
                           * @param data Dynamic data which is concatenated with the fixed aggregator's
                           * data in the delecatecall made to the adapter
                           */
                          function swap(
                              string calldata aggregatorId,
                              IERC20 tokenFrom,
                              uint256 amount,
                              bytes calldata data
                          ) external payable whenNotPaused nonReentrant {
                              _swap(aggregatorId, tokenFrom, amount, data);
                          }
                          /**
                           * @dev Performs a swap
                           * @param aggregatorId Identifier of the aggregator to be used for the swap
                           * @param data Dynamic data which is concatenated with the fixed aggregator's
                           * data in the delecatecall made to the adapter
                           */
                          function swapUsingGasToken(
                              string calldata aggregatorId,
                              IERC20 tokenFrom,
                              uint256 amount,
                              bytes calldata data
                          ) external payable whenNotPaused nonReentrant {
                              uint256 gas = gasleft();
                              _swap(aggregatorId, tokenFrom, amount, data);
                              uint256 gasSpent = 21000 + gas - gasleft() + 16 * msg.data.length;
                              chi.freeFromUpTo(msg.sender, (gasSpent + 14154) / 41947);
                          }
                          function pauseSwaps() external onlyOwner {
                              _pause();
                          }
                          function unpauseSwaps() external onlyOwner {
                              _unpause();
                          }
                          function _swap(
                              string calldata aggregatorId,
                              IERC20 tokenFrom,
                              uint256 amount,
                              bytes calldata data
                          ) internal {
                              Adapter storage adapter = adapters[aggregatorId];
                              if (address(tokenFrom) != Constants.ETH) {
                                  tokenFrom.safeTransferFrom(msg.sender, address(spender), amount);
                              }
                              spender.swap{value: msg.value}(
                                  adapter.addr,
                                  abi.encodePacked(
                                      adapter.selector,
                                      abi.encode(msg.sender),
                                      adapter.data,
                                      data
                                  )
                              );
                              emit Swap(aggregatorId, msg.sender);
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      import "../GSN/Context.sol";
                      /**
                       * @dev Contract module which provides a basic access control mechanism, where
                       * there is an account (an owner) that can be granted exclusive access to
                       * specific functions.
                       *
                       * By default, the owner account will be the one that deploys the contract. This
                       * can later be changed with {transferOwnership}.
                       *
                       * This module is used through inheritance. It will make available the modifier
                       * `onlyOwner`, which can be applied to your functions to restrict their use to
                       * the owner.
                       */
                      contract Ownable is Context {
                          address private _owner;
                          event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
                          /**
                           * @dev Initializes the contract setting the deployer as the initial owner.
                           */
                          constructor () internal {
                              address msgSender = _msgSender();
                              _owner = msgSender;
                              emit OwnershipTransferred(address(0), msgSender);
                          }
                          /**
                           * @dev Returns the address of the current owner.
                           */
                          function owner() public view returns (address) {
                              return _owner;
                          }
                          /**
                           * @dev Throws if called by any account other than the owner.
                           */
                          modifier onlyOwner() {
                              require(_owner == _msgSender(), "Ownable: caller is not the owner");
                              _;
                          }
                          /**
                           * @dev Leaves the contract without owner. It will not be possible to call
                           * `onlyOwner` functions anymore. Can only be called by the current owner.
                           *
                           * NOTE: Renouncing ownership will leave the contract without an owner,
                           * thereby removing any functionality that is only available to the owner.
                           */
                          function renounceOwnership() public virtual onlyOwner {
                              emit OwnershipTransferred(_owner, address(0));
                              _owner = address(0);
                          }
                          /**
                           * @dev Transfers ownership of the contract to a new account (`newOwner`).
                           * Can only be called by the current owner.
                           */
                          function transferOwnership(address newOwner) public virtual onlyOwner {
                              require(newOwner != address(0), "Ownable: new owner is the zero address");
                              emit OwnershipTransferred(_owner, newOwner);
                              _owner = newOwner;
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      import "../GSN/Context.sol";
                      /**
                       * @dev Contract module which allows children to implement an emergency stop
                       * mechanism that can be triggered by an authorized account.
                       *
                       * This module is used through inheritance. It will make available the
                       * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
                       * the functions of your contract. Note that they will not be pausable by
                       * simply including this module, only once the modifiers are put in place.
                       */
                      contract Pausable is Context {
                          /**
                           * @dev Emitted when the pause is triggered by `account`.
                           */
                          event Paused(address account);
                          /**
                           * @dev Emitted when the pause is lifted by `account`.
                           */
                          event Unpaused(address account);
                          bool private _paused;
                          /**
                           * @dev Initializes the contract in unpaused state.
                           */
                          constructor () internal {
                              _paused = false;
                          }
                          /**
                           * @dev Returns true if the contract is paused, and false otherwise.
                           */
                          function paused() public view returns (bool) {
                              return _paused;
                          }
                          /**
                           * @dev Modifier to make a function callable only when the contract is not paused.
                           *
                           * Requirements:
                           *
                           * - The contract must not be paused.
                           */
                          modifier whenNotPaused() {
                              require(!_paused, "Pausable: paused");
                              _;
                          }
                          /**
                           * @dev Modifier to make a function callable only when the contract is paused.
                           *
                           * Requirements:
                           *
                           * - The contract must be paused.
                           */
                          modifier whenPaused() {
                              require(_paused, "Pausable: not paused");
                              _;
                          }
                          /**
                           * @dev Triggers stopped state.
                           *
                           * Requirements:
                           *
                           * - The contract must not be paused.
                           */
                          function _pause() internal virtual whenNotPaused {
                              _paused = true;
                              emit Paused(_msgSender());
                          }
                          /**
                           * @dev Returns to normal state.
                           *
                           * Requirements:
                           *
                           * - The contract must be paused.
                           */
                          function _unpause() internal virtual whenPaused {
                              _paused = false;
                              emit Unpaused(_msgSender());
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      /**
                       * @dev Contract module that helps prevent reentrant calls to a function.
                       *
                       * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
                       * available, which can be applied to functions to make sure there are no nested
                       * (reentrant) calls to them.
                       *
                       * Note that because there is a single `nonReentrant` guard, functions marked as
                       * `nonReentrant` may not call one another. This can be worked around by making
                       * those functions `private`, and then adding `external` `nonReentrant` entry
                       * points to them.
                       *
                       * TIP: If you would like to learn more about reentrancy and alternative ways
                       * to protect against it, check out our blog post
                       * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
                       */
                      contract ReentrancyGuard {
                          // Booleans are more expensive than uint256 or any type that takes up a full
                          // word because each write operation emits an extra SLOAD to first read the
                          // slot's contents, replace the bits taken up by the boolean, and then write
                          // back. This is the compiler's defense against contract upgrades and
                          // pointer aliasing, and it cannot be disabled.
                          // The values being non-zero value makes deployment a bit more expensive,
                          // but in exchange the refund on every call to nonReentrant will be lower in
                          // amount. Since refunds are capped to a percentage of the total
                          // transaction's gas, it is best to keep them low in cases like this one, to
                          // increase the likelihood of the full refund coming into effect.
                          uint256 private constant _NOT_ENTERED = 1;
                          uint256 private constant _ENTERED = 2;
                          uint256 private _status;
                          constructor () internal {
                              _status = _NOT_ENTERED;
                          }
                          /**
                           * @dev Prevents a contract from calling itself, directly or indirectly.
                           * Calling a `nonReentrant` function from another `nonReentrant`
                           * function is not supported. It is possible to prevent this from happening
                           * by making the `nonReentrant` function external, and make it call a
                           * `private` function that does the actual work.
                           */
                          modifier nonReentrant() {
                              // On the first call to nonReentrant, _notEntered will be true
                              require(_status != _ENTERED, "ReentrancyGuard: reentrant call");
                              // Any calls to nonReentrant after this point will fail
                              _status = _ENTERED;
                              _;
                              // By storing the original value once again, a refund is triggered (see
                              // https://eips.ethereum.org/EIPS/eip-2200)
                              _status = _NOT_ENTERED;
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity ^0.6.0;
                      import "./Constants.sol";
                      contract Spender {
                          address public immutable metaswap;
                          constructor() public {
                              metaswap = msg.sender;
                          }
                          /// @dev Receives ether from swaps
                          fallback() external payable {}
                          function swap(address adapter, bytes calldata data) external payable {
                              require(msg.sender == metaswap, "FORBIDDEN");
                              require(adapter != address(0), "ADAPTER_NOT_PROVIDED");
                              _delegate(adapter, data, "ADAPTER_DELEGATECALL_FAILED");
                          }
                          /**
                           * @dev Performs a delegatecall and bubbles up the errors, adapted from
                           * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Address.sol
                           * @param target Address of the contract to delegatecall
                           * @param data Data passed in the delegatecall
                           * @param errorMessage Fallback revert reason
                           */
                          function _delegate(
                              address target,
                              bytes memory data,
                              string memory errorMessage
                          ) private returns (bytes memory) {
                              // solhint-disable-next-line avoid-low-level-calls
                              (bool success, bytes memory returndata) = target.delegatecall(data);
                              if (success) {
                                  return returndata;
                              } else {
                                  // Look for revert reason and bubble it up if present
                                  if (returndata.length > 0) {
                                      // The easiest way to bubble the revert reason is using memory via assembly
                                      // solhint-disable-next-line no-inline-assembly
                                      assembly {
                                          let returndata_size := mload(returndata)
                                          revert(add(32, returndata), returndata_size)
                                      }
                                  } else {
                                      revert(errorMessage);
                                  }
                              }
                          }
                      }
                      pragma solidity ^0.6.0;
                      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      import "@openzeppelin/contracts/utils/Address.sol";
                      contract MockAdapter {
                          using SafeERC20 for IERC20;
                          using Address for address;
                          using Address for address payable;
                          event MockAdapterEvent(
                              address sender,
                              uint256 valueFixed,
                              uint256 valueDynamic
                          );
                          function test(
                              address sender,
                              uint256 valueFixed,
                              uint256 valueDynamic
                          ) external payable {
                              emit MockAdapterEvent(sender, valueFixed, valueDynamic);
                          }
                          function testRevert(
                              address,
                              uint256,
                              uint256
                          ) external payable {
                              revert("SWAP_FAILED");
                          }
                          function testRevertNoReturnData(
                              address,
                              uint256,
                              uint256
                          ) external payable {
                              revert();
                          }
                      }
                      pragma solidity ^0.6.0;
                      // TAKEN FROM https://github.com/gnosis/mock-contract
                      // TODO: use their npm package once it is published for solidity 0.6
                      interface MockInterface {
                          /**
                           * @dev After calling this method, the mock will return `response` when it is called
                           * with any calldata that is not mocked more specifically below
                           * (e.g. using givenMethodReturn).
                           * @param response ABI encoded response that will be returned if method is invoked
                           */
                          function givenAnyReturn(bytes calldata response) external;
                          function givenAnyReturnBool(bool response) external;
                          function givenAnyReturnUint(uint256 response) external;
                          function givenAnyReturnAddress(address response) external;
                          function givenAnyRevert() external;
                          function givenAnyRevertWithMessage(string calldata message) external;
                          function givenAnyRunOutOfGas() external;
                          /**
                           * @dev After calling this method, the mock will return `response` when the given
                           * methodId is called regardless of arguments. If the methodId and arguments
                           * are mocked more specifically (using `givenMethodAndArguments`) the latter
                           * will take precedence.
                           * @param method ABI encoded methodId. It is valid to pass full calldata (including arguments). The mock will extract the methodId from it
                           * @param response ABI encoded response that will be returned if method is invoked
                           */
                          function givenMethodReturn(bytes calldata method, bytes calldata response)
                              external;
                          function givenMethodReturnBool(bytes calldata method, bool response)
                              external;
                          function givenMethodReturnUint(bytes calldata method, uint256 response)
                              external;
                          function givenMethodReturnAddress(bytes calldata method, address response)
                              external;
                          function givenMethodRevert(bytes calldata method) external;
                          function givenMethodRevertWithMessage(
                              bytes calldata method,
                              string calldata message
                          ) external;
                          function givenMethodRunOutOfGas(bytes calldata method) external;
                          /**
                           * @dev After calling this method, the mock will return `response` when the given
                           * methodId is called with matching arguments. These exact calldataMocks will take
                           * precedence over all other calldataMocks.
                           * @param call ABI encoded calldata (methodId and arguments)
                           * @param response ABI encoded response that will be returned if contract is invoked with calldata
                           */
                          function givenCalldataReturn(bytes calldata call, bytes calldata response)
                              external;
                          function givenCalldataReturnBool(bytes calldata call, bool response)
                              external;
                          function givenCalldataReturnUint(bytes calldata call, uint256 response)
                              external;
                          function givenCalldataReturnAddress(bytes calldata call, address response)
                              external;
                          function givenCalldataRevert(bytes calldata call) external;
                          function givenCalldataRevertWithMessage(
                              bytes calldata call,
                              string calldata message
                          ) external;
                          function givenCalldataRunOutOfGas(bytes calldata call) external;
                          /**
                           * @dev Returns the number of times anything has been called on this mock since last reset
                           */
                          function invocationCount() external returns (uint256);
                          /**
                           * @dev Returns the number of times the given method has been called on this mock since last reset
                           * @param method ABI encoded methodId. It is valid to pass full calldata (including arguments). The mock will extract the methodId from it
                           */
                          function invocationCountForMethod(bytes calldata method)
                              external
                              returns (uint256);
                          /**
                           * @dev Returns the number of times this mock has been called with the exact calldata since last reset.
                           * @param call ABI encoded calldata (methodId and arguments)
                           */
                          function invocationCountForCalldata(bytes calldata call)
                              external
                              returns (uint256);
                          /**
                           * @dev Resets all mocked methods and invocation counts.
                           */
                          function reset() external;
                      }
                      /**
                       * Implementation of the MockInterface.
                       */
                      contract MockContract is MockInterface {
                          enum MockType {Return, Revert, OutOfGas}
                          bytes32 public constant MOCKS_LIST_START = hex"01";
                          bytes public constant MOCKS_LIST_END = "0xff";
                          bytes32 public constant MOCKS_LIST_END_HASH = keccak256(MOCKS_LIST_END);
                          bytes4 public constant SENTINEL_ANY_MOCKS = hex"01";
                          bytes public constant DEFAULT_FALLBACK_VALUE = abi.encode(false);
                          // A linked list allows easy iteration and inclusion checks
                          mapping(bytes32 => bytes) calldataMocks;
                          mapping(bytes => MockType) calldataMockTypes;
                          mapping(bytes => bytes) calldataExpectations;
                          mapping(bytes => string) calldataRevertMessage;
                          mapping(bytes32 => uint256) calldataInvocations;
                          mapping(bytes4 => bytes4) methodIdMocks;
                          mapping(bytes4 => MockType) methodIdMockTypes;
                          mapping(bytes4 => bytes) methodIdExpectations;
                          mapping(bytes4 => string) methodIdRevertMessages;
                          mapping(bytes32 => uint256) methodIdInvocations;
                          MockType fallbackMockType;
                          bytes fallbackExpectation = DEFAULT_FALLBACK_VALUE;
                          string fallbackRevertMessage;
                          uint256 invocations;
                          uint256 resetCount;
                          constructor() public {
                              calldataMocks[MOCKS_LIST_START] = MOCKS_LIST_END;
                              methodIdMocks[SENTINEL_ANY_MOCKS] = SENTINEL_ANY_MOCKS;
                          }
                          function trackCalldataMock(bytes memory call) private {
                              bytes32 callHash = keccak256(call);
                              if (calldataMocks[callHash].length == 0) {
                                  calldataMocks[callHash] = calldataMocks[MOCKS_LIST_START];
                                  calldataMocks[MOCKS_LIST_START] = call;
                              }
                          }
                          function trackMethodIdMock(bytes4 methodId) private {
                              if (methodIdMocks[methodId] == 0x0) {
                                  methodIdMocks[methodId] = methodIdMocks[SENTINEL_ANY_MOCKS];
                                  methodIdMocks[SENTINEL_ANY_MOCKS] = methodId;
                              }
                          }
                          function _givenAnyReturn(bytes memory response) internal {
                              fallbackMockType = MockType.Return;
                              fallbackExpectation = response;
                          }
                          function givenAnyReturn(bytes calldata response) external override {
                              _givenAnyReturn(response);
                          }
                          function givenAnyReturnBool(bool response) external override {
                              uint256 flag = response ? 1 : 0;
                              _givenAnyReturn(uintToBytes(flag));
                          }
                          function givenAnyReturnUint(uint256 response) external override {
                              _givenAnyReturn(uintToBytes(response));
                          }
                          function givenAnyReturnAddress(address response) external override {
                              _givenAnyReturn(uintToBytes(uint256(response)));
                          }
                          function givenAnyRevert() external override {
                              fallbackMockType = MockType.Revert;
                              fallbackRevertMessage = "";
                          }
                          function givenAnyRevertWithMessage(string calldata message)
                              external
                              override
                          {
                              fallbackMockType = MockType.Revert;
                              fallbackRevertMessage = message;
                          }
                          function givenAnyRunOutOfGas() external override {
                              fallbackMockType = MockType.OutOfGas;
                          }
                          function _givenCalldataReturn(bytes memory call, bytes memory response)
                              private
                          {
                              calldataMockTypes[call] = MockType.Return;
                              calldataExpectations[call] = response;
                              trackCalldataMock(call);
                          }
                          function givenCalldataReturn(bytes calldata call, bytes calldata response)
                              external
                              override
                          {
                              _givenCalldataReturn(call, response);
                          }
                          function givenCalldataReturnBool(bytes calldata call, bool response)
                              external
                              override
                          {
                              uint256 flag = response ? 1 : 0;
                              _givenCalldataReturn(call, uintToBytes(flag));
                          }
                          function givenCalldataReturnUint(bytes calldata call, uint256 response)
                              external
                              override
                          {
                              _givenCalldataReturn(call, uintToBytes(response));
                          }
                          function givenCalldataReturnAddress(bytes calldata call, address response)
                              external
                              override
                          {
                              _givenCalldataReturn(call, uintToBytes(uint256(response)));
                          }
                          function _givenMethodReturn(bytes memory call, bytes memory response)
                              private
                          {
                              bytes4 method = bytesToBytes4(call);
                              methodIdMockTypes[method] = MockType.Return;
                              methodIdExpectations[method] = response;
                              trackMethodIdMock(method);
                          }
                          function givenMethodReturn(bytes calldata call, bytes calldata response)
                              external
                              override
                          {
                              _givenMethodReturn(call, response);
                          }
                          function givenMethodReturnBool(bytes calldata call, bool response)
                              external
                              override
                          {
                              uint256 flag = response ? 1 : 0;
                              _givenMethodReturn(call, uintToBytes(flag));
                          }
                          function givenMethodReturnUint(bytes calldata call, uint256 response)
                              external
                              override
                          {
                              _givenMethodReturn(call, uintToBytes(response));
                          }
                          function givenMethodReturnAddress(bytes calldata call, address response)
                              external
                              override
                          {
                              _givenMethodReturn(call, uintToBytes(uint256(response)));
                          }
                          function givenCalldataRevert(bytes calldata call) external override {
                              calldataMockTypes[call] = MockType.Revert;
                              calldataRevertMessage[call] = "";
                              trackCalldataMock(call);
                          }
                          function givenMethodRevert(bytes calldata call) external override {
                              bytes4 method = bytesToBytes4(call);
                              methodIdMockTypes[method] = MockType.Revert;
                              trackMethodIdMock(method);
                          }
                          function givenCalldataRevertWithMessage(
                              bytes calldata call,
                              string calldata message
                          ) external override {
                              calldataMockTypes[call] = MockType.Revert;
                              calldataRevertMessage[call] = message;
                              trackCalldataMock(call);
                          }
                          function givenMethodRevertWithMessage(
                              bytes calldata call,
                              string calldata message
                          ) external override {
                              bytes4 method = bytesToBytes4(call);
                              methodIdMockTypes[method] = MockType.Revert;
                              methodIdRevertMessages[method] = message;
                              trackMethodIdMock(method);
                          }
                          function givenCalldataRunOutOfGas(bytes calldata call) external override {
                              calldataMockTypes[call] = MockType.OutOfGas;
                              trackCalldataMock(call);
                          }
                          function givenMethodRunOutOfGas(bytes calldata call) external override {
                              bytes4 method = bytesToBytes4(call);
                              methodIdMockTypes[method] = MockType.OutOfGas;
                              trackMethodIdMock(method);
                          }
                          function invocationCount() external override returns (uint256) {
                              return invocations;
                          }
                          function invocationCountForMethod(bytes calldata call)
                              external
                              override
                              returns (uint256)
                          {
                              bytes4 method = bytesToBytes4(call);
                              return
                                  methodIdInvocations[keccak256(
                                      abi.encodePacked(resetCount, method)
                                  )];
                          }
                          function invocationCountForCalldata(bytes calldata call)
                              external
                              override
                              returns (uint256)
                          {
                              return
                                  calldataInvocations[keccak256(abi.encodePacked(resetCount, call))];
                          }
                          function reset() external override {
                              // Reset all exact calldataMocks
                              bytes memory nextMock = calldataMocks[MOCKS_LIST_START];
                              bytes32 mockHash = keccak256(nextMock);
                              // We cannot compary bytes
                              while (mockHash != MOCKS_LIST_END_HASH) {
                                  // Reset all mock maps
                                  calldataMockTypes[nextMock] = MockType.Return;
                                  calldataExpectations[nextMock] = hex"";
                                  calldataRevertMessage[nextMock] = "";
                                  // Set next mock to remove
                                  nextMock = calldataMocks[mockHash];
                                  // Remove from linked list
                                  calldataMocks[mockHash] = "";
                                  // Update mock hash
                                  mockHash = keccak256(nextMock);
                              }
                              // Clear list
                              calldataMocks[MOCKS_LIST_START] = MOCKS_LIST_END;
                              // Reset all any calldataMocks
                              bytes4 nextAnyMock = methodIdMocks[SENTINEL_ANY_MOCKS];
                              while (nextAnyMock != SENTINEL_ANY_MOCKS) {
                                  bytes4 currentAnyMock = nextAnyMock;
                                  methodIdMockTypes[currentAnyMock] = MockType.Return;
                                  methodIdExpectations[currentAnyMock] = hex"";
                                  methodIdRevertMessages[currentAnyMock] = "";
                                  nextAnyMock = methodIdMocks[currentAnyMock];
                                  // Remove from linked list
                                  methodIdMocks[currentAnyMock] = 0x0;
                              }
                              // Clear list
                              methodIdMocks[SENTINEL_ANY_MOCKS] = SENTINEL_ANY_MOCKS;
                              fallbackExpectation = DEFAULT_FALLBACK_VALUE;
                              fallbackMockType = MockType.Return;
                              invocations = 0;
                              resetCount += 1;
                          }
                          function useAllGas() private {
                              while (true) {
                                  bool s;
                                  assembly {
                                      //expensive call to EC multiply contract
                                      s := call(sub(gas(), 2000), 6, 0, 0x0, 0xc0, 0x0, 0x60)
                                  }
                              }
                          }
                          function bytesToBytes4(bytes memory b) private pure returns (bytes4) {
                              bytes4 out;
                              for (uint256 i = 0; i < 4; i++) {
                                  out |= bytes4(b[i] & 0xFF) >> (i * 8);
                              }
                              return out;
                          }
                          function uintToBytes(uint256 x) private pure returns (bytes memory b) {
                              b = new bytes(32);
                              assembly {
                                  mstore(add(b, 32), x)
                              }
                          }
                          function updateInvocationCount(
                              bytes4 methodId,
                              bytes memory originalMsgData
                          ) public {
                              require(
                                  msg.sender == address(this),
                                  "Can only be called from the contract itself"
                              );
                              invocations += 1;
                              methodIdInvocations[keccak256(
                                  abi.encodePacked(resetCount, methodId)
                              )] += 1;
                              calldataInvocations[keccak256(
                                  abi.encodePacked(resetCount, originalMsgData)
                              )] += 1;
                          }
                          fallback() external payable {
                              bytes4 methodId;
                              assembly {
                                  methodId := calldataload(0)
                              }
                              // First, check exact matching overrides
                              if (calldataMockTypes[msg.data] == MockType.Revert) {
                                  revert(calldataRevertMessage[msg.data]);
                              }
                              if (calldataMockTypes[msg.data] == MockType.OutOfGas) {
                                  useAllGas();
                              }
                              bytes memory result = calldataExpectations[msg.data];
                              // Then check method Id overrides
                              if (result.length == 0) {
                                  if (methodIdMockTypes[methodId] == MockType.Revert) {
                                      revert(methodIdRevertMessages[methodId]);
                                  }
                                  if (methodIdMockTypes[methodId] == MockType.OutOfGas) {
                                      useAllGas();
                                  }
                                  result = methodIdExpectations[methodId];
                              }
                              // Last, use the fallback override
                              if (result.length == 0) {
                                  if (fallbackMockType == MockType.Revert) {
                                      revert(fallbackRevertMessage);
                                  }
                                  if (fallbackMockType == MockType.OutOfGas) {
                                      useAllGas();
                                  }
                                  result = fallbackExpectation;
                              }
                              // Record invocation as separate call so we don't rollback in case we are called with STATICCALL
                              (, bytes memory r) = address(this).call{gas: 100000}(
                                  abi.encodeWithSignature(
                                      "updateInvocationCount(bytes4,bytes)",
                                      methodId,
                                      msg.data
                                  )
                              );
                              assert(r.length == 0);
                              assembly {
                                  return(add(0x20, result), mload(result))
                              }
                          }
                      }
                      pragma solidity ^0.6.0;
                      contract MockSelfDestruct {
                          constructor() public payable {}
                          fallback() external payable {
                              selfdestruct(msg.sender);
                          }
                          function kill(address payable target) external payable {
                              selfdestruct(target);
                          }
                      }
                      

                      File 2 of 7: FiatTokenProxy
                      pragma solidity ^0.4.24;
                      
                      // File: zos-lib/contracts/upgradeability/Proxy.sol
                      
                      /**
                       * @title Proxy
                       * @dev Implements delegation of calls to other contracts, with proper
                       * forwarding of return values and bubbling of failures.
                       * It defines a fallback function that delegates all calls to the address
                       * returned by the abstract _implementation() internal function.
                       */
                      contract Proxy {
                        /**
                         * @dev Fallback function.
                         * Implemented entirely in `_fallback`.
                         */
                        function () payable external {
                          _fallback();
                        }
                      
                        /**
                         * @return The Address of the implementation.
                         */
                        function _implementation() internal view returns (address);
                      
                        /**
                         * @dev Delegates execution to an implementation contract.
                         * This is a low level function that doesn't return to its internal call site.
                         * It will return to the external caller whatever the implementation returns.
                         * @param implementation Address to delegate.
                         */
                        function _delegate(address implementation) internal {
                          assembly {
                            // Copy msg.data. We take full control of memory in this inline assembly
                            // block because it will not return to Solidity code. We overwrite the
                            // Solidity scratch pad at memory position 0.
                            calldatacopy(0, 0, calldatasize)
                      
                            // Call the implementation.
                            // out and outsize are 0 because we don't know the size yet.
                            let result := delegatecall(gas, implementation, 0, calldatasize, 0, 0)
                      
                            // Copy the returned data.
                            returndatacopy(0, 0, returndatasize)
                      
                            switch result
                            // delegatecall returns 0 on error.
                            case 0 { revert(0, returndatasize) }
                            default { return(0, returndatasize) }
                          }
                        }
                      
                        /**
                         * @dev Function that is run as the first thing in the fallback function.
                         * Can be redefined in derived contracts to add functionality.
                         * Redefinitions must call super._willFallback().
                         */
                        function _willFallback() internal {
                        }
                      
                        /**
                         * @dev fallback implementation.
                         * Extracted to enable manual triggering.
                         */
                        function _fallback() internal {
                          _willFallback();
                          _delegate(_implementation());
                        }
                      }
                      
                      // File: openzeppelin-solidity/contracts/AddressUtils.sol
                      
                      /**
                       * Utility library of inline functions on addresses
                       */
                      library AddressUtils {
                      
                        /**
                         * Returns whether the target address is a contract
                         * @dev This function will return false if invoked during the constructor of a contract,
                         * as the code is not actually created until after the constructor finishes.
                         * @param addr address to check
                         * @return whether the target address is a contract
                         */
                        function isContract(address addr) internal view returns (bool) {
                          uint256 size;
                          // XXX Currently there is no better way to check if there is a contract in an address
                          // than to check the size of the code at that address.
                          // See https://ethereum.stackexchange.com/a/14016/36603
                          // for more details about how this works.
                          // TODO Check this again before the Serenity release, because all addresses will be
                          // contracts then.
                          // solium-disable-next-line security/no-inline-assembly
                          assembly { size := extcodesize(addr) }
                          return size > 0;
                        }
                      
                      }
                      
                      // File: zos-lib/contracts/upgradeability/UpgradeabilityProxy.sol
                      
                      /**
                       * @title UpgradeabilityProxy
                       * @dev This contract implements a proxy that allows to change the
                       * implementation address to which it will delegate.
                       * Such a change is called an implementation upgrade.
                       */
                      contract UpgradeabilityProxy is Proxy {
                        /**
                         * @dev Emitted when the implementation is upgraded.
                         * @param implementation Address of the new implementation.
                         */
                        event Upgraded(address implementation);
                      
                        /**
                         * @dev Storage slot with the address of the current implementation.
                         * This is the keccak-256 hash of "org.zeppelinos.proxy.implementation", and is
                         * validated in the constructor.
                         */
                        bytes32 private constant IMPLEMENTATION_SLOT = 0x7050c9e0f4ca769c69bd3a8ef740bc37934f8e2c036e5a723fd8ee048ed3f8c3;
                      
                        /**
                         * @dev Contract constructor.
                         * @param _implementation Address of the initial implementation.
                         */
                        constructor(address _implementation) public {
                          assert(IMPLEMENTATION_SLOT == keccak256("org.zeppelinos.proxy.implementation"));
                      
                          _setImplementation(_implementation);
                        }
                      
                        /**
                         * @dev Returns the current implementation.
                         * @return Address of the current implementation
                         */
                        function _implementation() internal view returns (address impl) {
                          bytes32 slot = IMPLEMENTATION_SLOT;
                          assembly {
                            impl := sload(slot)
                          }
                        }
                      
                        /**
                         * @dev Upgrades the proxy to a new implementation.
                         * @param newImplementation Address of the new implementation.
                         */
                        function _upgradeTo(address newImplementation) internal {
                          _setImplementation(newImplementation);
                          emit Upgraded(newImplementation);
                        }
                      
                        /**
                         * @dev Sets the implementation address of the proxy.
                         * @param newImplementation Address of the new implementation.
                         */
                        function _setImplementation(address newImplementation) private {
                          require(AddressUtils.isContract(newImplementation), "Cannot set a proxy implementation to a non-contract address");
                      
                          bytes32 slot = IMPLEMENTATION_SLOT;
                      
                          assembly {
                            sstore(slot, newImplementation)
                          }
                        }
                      }
                      
                      // File: zos-lib/contracts/upgradeability/AdminUpgradeabilityProxy.sol
                      
                      /**
                       * @title AdminUpgradeabilityProxy
                       * @dev This contract combines an upgradeability proxy with an authorization
                       * mechanism for administrative tasks.
                       * All external functions in this contract must be guarded by the
                       * `ifAdmin` modifier. See ethereum/solidity#3864 for a Solidity
                       * feature proposal that would enable this to be done automatically.
                       */
                      contract AdminUpgradeabilityProxy is UpgradeabilityProxy {
                        /**
                         * @dev Emitted when the administration has been transferred.
                         * @param previousAdmin Address of the previous admin.
                         * @param newAdmin Address of the new admin.
                         */
                        event AdminChanged(address previousAdmin, address newAdmin);
                      
                        /**
                         * @dev Storage slot with the admin of the contract.
                         * This is the keccak-256 hash of "org.zeppelinos.proxy.admin", and is
                         * validated in the constructor.
                         */
                        bytes32 private constant ADMIN_SLOT = 0x10d6a54a4754c8869d6886b5f5d7fbfa5b4522237ea5c60d11bc4e7a1ff9390b;
                      
                        /**
                         * @dev Modifier to check whether the `msg.sender` is the admin.
                         * If it is, it will run the function. Otherwise, it will delegate the call
                         * to the implementation.
                         */
                        modifier ifAdmin() {
                          if (msg.sender == _admin()) {
                            _;
                          } else {
                            _fallback();
                          }
                        }
                      
                        /**
                         * Contract constructor.
                         * It sets the `msg.sender` as the proxy administrator.
                         * @param _implementation address of the initial implementation.
                         */
                        constructor(address _implementation) UpgradeabilityProxy(_implementation) public {
                          assert(ADMIN_SLOT == keccak256("org.zeppelinos.proxy.admin"));
                      
                          _setAdmin(msg.sender);
                        }
                      
                        /**
                         * @return The address of the proxy admin.
                         */
                        function admin() external view ifAdmin returns (address) {
                          return _admin();
                        }
                      
                        /**
                         * @return The address of the implementation.
                         */
                        function implementation() external view ifAdmin returns (address) {
                          return _implementation();
                        }
                      
                        /**
                         * @dev Changes the admin of the proxy.
                         * Only the current admin can call this function.
                         * @param newAdmin Address to transfer proxy administration to.
                         */
                        function changeAdmin(address newAdmin) external ifAdmin {
                          require(newAdmin != address(0), "Cannot change the admin of a proxy to the zero address");
                          emit AdminChanged(_admin(), newAdmin);
                          _setAdmin(newAdmin);
                        }
                      
                        /**
                         * @dev Upgrade the backing implementation of the proxy.
                         * Only the admin can call this function.
                         * @param newImplementation Address of the new implementation.
                         */
                        function upgradeTo(address newImplementation) external ifAdmin {
                          _upgradeTo(newImplementation);
                        }
                      
                        /**
                         * @dev Upgrade the backing implementation of the proxy and call a function
                         * on the new implementation.
                         * This is useful to initialize the proxied contract.
                         * @param newImplementation Address of the new implementation.
                         * @param data Data to send as msg.data in the low level call.
                         * It should include the signature and the parameters of the function to be
                         * called, as described in
                         * https://solidity.readthedocs.io/en/develop/abi-spec.html#function-selector-and-argument-encoding.
                         */
                        function upgradeToAndCall(address newImplementation, bytes data) payable external ifAdmin {
                          _upgradeTo(newImplementation);
                          require(address(this).call.value(msg.value)(data));
                        }
                      
                        /**
                         * @return The admin slot.
                         */
                        function _admin() internal view returns (address adm) {
                          bytes32 slot = ADMIN_SLOT;
                          assembly {
                            adm := sload(slot)
                          }
                        }
                      
                        /**
                         * @dev Sets the address of the proxy admin.
                         * @param newAdmin Address of the new proxy admin.
                         */
                        function _setAdmin(address newAdmin) internal {
                          bytes32 slot = ADMIN_SLOT;
                      
                          assembly {
                            sstore(slot, newAdmin)
                          }
                        }
                      
                        /**
                         * @dev Only fall back when the sender is not the admin.
                         */
                        function _willFallback() internal {
                          require(msg.sender != _admin(), "Cannot call fallback function from the proxy admin");
                          super._willFallback();
                        }
                      }
                      
                      // File: contracts/FiatTokenProxy.sol
                      
                      /**
                      * Copyright CENTRE SECZ 2018
                      *
                      * Permission is hereby granted, free of charge, to any person obtaining a copy 
                      * of this software and associated documentation files (the "Software"), to deal 
                      * in the Software without restriction, including without limitation the rights 
                      * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
                      * copies of the Software, and to permit persons to whom the Software is furnished to 
                      * do so, subject to the following conditions:
                      *
                      * The above copyright notice and this permission notice shall be included in all 
                      * copies or substantial portions of the Software.
                      *
                      * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
                      * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
                      * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
                      * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
                      * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 
                      * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
                      */
                      
                      pragma solidity ^0.4.24;
                      
                      
                      /**
                       * @title FiatTokenProxy
                       * @dev This contract proxies FiatToken calls and enables FiatToken upgrades
                      */ 
                      contract FiatTokenProxy is AdminUpgradeabilityProxy {
                          constructor(address _implementation) public AdminUpgradeabilityProxy(_implementation) {
                          }
                      }

                      File 3 of 7: Spender
                      {"Constants.84ef19f8.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity ^0.6.0;\r\n\r\nlibrary Constants {\r\n    address internal constant ETH = 0x0000000000000000000000000000000000000000;\r\n}\r\n"},"Spender.3372a096.sol":{"content":"// SPDX-License-Identifier: MIT\r\n\r\npragma solidity ^0.6.0;\r\n\r\nimport \"./Constants.84ef19f8.sol\";\r\n\r\ncontract Spender {\r\n    address public immutable metaswap;\r\n\r\n    constructor() public {\r\n        metaswap = msg.sender;\r\n    }\r\n\r\n    /// @dev Receives ether from swaps\r\n    fallback() external payable {}\r\n\r\n    function swap(address adapter, bytes calldata data) external payable {\r\n        require(msg.sender == metaswap, \"FORBIDDEN\");\r\n        require(adapter != address(0), \"ADAPTER_NOT_PROVIDED\");\r\n        _delegate(adapter, data, \"ADAPTER_DELEGATECALL_FAILED\");\r\n    }\r\n\r\n    /**\r\n     * @dev Performs a delegatecall and bubbles up the errors, adapted from\r\n     * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Address.sol\r\n     * @param target Address of the contract to delegatecall\r\n     * @param data Data passed in the delegatecall\r\n     * @param errorMessage Fallback revert reason\r\n     */\r\n    function _delegate(\r\n        address target,\r\n        bytes memory data,\r\n        string memory errorMessage\r\n    ) private returns (bytes memory) {\r\n        // solhint-disable-next-line avoid-low-level-calls\r\n        (bool success, bytes memory returndata) = target.delegatecall(data);\r\n        if (success) {\r\n            return returndata;\r\n        } else {\r\n            // Look for revert reason and bubble it up if present\r\n            if (returndata.length \u003e 0) {\r\n                // The easiest way to bubble the revert reason is using memory via assembly\r\n\r\n                // solhint-disable-next-line no-inline-assembly\r\n                assembly {\r\n                    let returndata_size := mload(returndata)\r\n                    revert(add(32, returndata), returndata_size)\r\n                }\r\n            } else {\r\n                revert(errorMessage);\r\n            }\r\n        }\r\n    }\r\n}\r\n"}}

                      File 4 of 7: ENA
                      // SPDX-License-Identifier: GPL-3.0
                      pragma solidity 0.8.20;
                      import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
                      import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";
                      import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Permit.sol";
                      import "@openzeppelin/contracts/access/Ownable2Step.sol";
                      import "./interfaces/IENADefinitions.sol";
                      /**
                       * @title ENA
                       * @notice Governance token for the Ethena protocol
                       */
                      contract ENA is Ownable2Step, ERC20Burnable, ERC20Permit, IENADefinitions {
                        /// @notice Maximum inflation rate per year (percentage) expressed as an integer
                        uint8 public constant MAX_INFLATION = 10;
                        /// @notice The maximum frequency of inflationary mint invocations
                        uint32 public constant MINT_WAIT_PERIOD = 365 days;
                        /// @notice The last time the mint function was called
                        uint40 public lastMintTimestamp;
                        constructor(address _initialOwner, address _treasury, address _foundation) ERC20("ENA", "ENA") ERC20Permit("ENA") {
                          // first mint not allowed until 1 year after deployment
                          lastMintTimestamp = uint40(block.timestamp);
                          if (_initialOwner == address(0) || _treasury == address(0) || _foundation == address(0)) revert ZeroAddressException();
                          _transferOwnership(_initialOwner);
                          // initial supply of 15 billion tokens
                          _mint(_treasury, 3_750_000_000 * 10 ** 18);
                          _mint(_foundation, 11_250_000_000 * 10 ** 18);
                        }
                        /**
                         * @notice Mints new ENA tokens
                         * @param to The address to mint tokens to
                         * @param amount The amount of tokens to mint
                         * @dev Only callable by the owner once per year and amount must be less than max inflation rate
                         */
                        function mint(address to, uint256 amount) external onlyOwner {
                          if (block.timestamp - lastMintTimestamp < MINT_WAIT_PERIOD) revert MintWaitPeriodInProgress();
                          uint256 _maxInflationAmount = totalSupply() * MAX_INFLATION / 100;
                          if (amount > _maxInflationAmount) revert MaxInflationExceeded();
                          lastMintTimestamp = uint40(block.timestamp);
                          _mint(to, amount);
                          emit Mint(to, amount);
                        }
                        /// @notice Prevents the owner from renouncing ownership
                        function renounceOwnership() public view override onlyOwner {
                          revert CantRenounceOwnership();
                        }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/ERC20.sol)
                      pragma solidity ^0.8.0;
                      import "./IERC20.sol";
                      import "./extensions/IERC20Metadata.sol";
                      import "../../utils/Context.sol";
                      /**
                       * @dev Implementation of the {IERC20} interface.
                       *
                       * This implementation is agnostic to the way tokens are created. This means
                       * that a supply mechanism has to be added in a derived contract using {_mint}.
                       * For a generic mechanism see {ERC20PresetMinterPauser}.
                       *
                       * TIP: For a detailed writeup see our guide
                       * https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
                       * to implement supply mechanisms].
                       *
                       * The default value of {decimals} is 18. To change this, you should override
                       * this function so it returns a different value.
                       *
                       * We have followed general OpenZeppelin Contracts guidelines: functions revert
                       * instead returning `false` on failure. This behavior is nonetheless
                       * conventional and does not conflict with the expectations of ERC20
                       * applications.
                       *
                       * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
                       * This allows applications to reconstruct the allowance for all accounts just
                       * by listening to said events. Other implementations of the EIP may not emit
                       * these events, as it isn't required by the specification.
                       *
                       * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
                       * functions have been added to mitigate the well-known issues around setting
                       * allowances. See {IERC20-approve}.
                       */
                      contract ERC20 is Context, IERC20, IERC20Metadata {
                          mapping(address => uint256) private _balances;
                          mapping(address => mapping(address => uint256)) private _allowances;
                          uint256 private _totalSupply;
                          string private _name;
                          string private _symbol;
                          /**
                           * @dev Sets the values for {name} and {symbol}.
                           *
                           * All two of these values are immutable: they can only be set once during
                           * construction.
                           */
                          constructor(string memory name_, string memory symbol_) {
                              _name = name_;
                              _symbol = symbol_;
                          }
                          /**
                           * @dev Returns the name of the token.
                           */
                          function name() public view virtual override returns (string memory) {
                              return _name;
                          }
                          /**
                           * @dev Returns the symbol of the token, usually a shorter version of the
                           * name.
                           */
                          function symbol() public view virtual override returns (string memory) {
                              return _symbol;
                          }
                          /**
                           * @dev Returns the number of decimals used to get its user representation.
                           * For example, if `decimals` equals `2`, a balance of `505` tokens should
                           * be displayed to a user as `5.05` (`505 / 10 ** 2`).
                           *
                           * Tokens usually opt for a value of 18, imitating the relationship between
                           * Ether and Wei. This is the default value returned by this function, unless
                           * it's overridden.
                           *
                           * NOTE: This information is only used for _display_ purposes: it in
                           * no way affects any of the arithmetic of the contract, including
                           * {IERC20-balanceOf} and {IERC20-transfer}.
                           */
                          function decimals() public view virtual override returns (uint8) {
                              return 18;
                          }
                          /**
                           * @dev See {IERC20-totalSupply}.
                           */
                          function totalSupply() public view virtual override returns (uint256) {
                              return _totalSupply;
                          }
                          /**
                           * @dev See {IERC20-balanceOf}.
                           */
                          function balanceOf(address account) public view virtual override returns (uint256) {
                              return _balances[account];
                          }
                          /**
                           * @dev See {IERC20-transfer}.
                           *
                           * Requirements:
                           *
                           * - `to` cannot be the zero address.
                           * - the caller must have a balance of at least `amount`.
                           */
                          function transfer(address to, uint256 amount) public virtual override returns (bool) {
                              address owner = _msgSender();
                              _transfer(owner, to, amount);
                              return true;
                          }
                          /**
                           * @dev See {IERC20-allowance}.
                           */
                          function allowance(address owner, address spender) public view virtual override returns (uint256) {
                              return _allowances[owner][spender];
                          }
                          /**
                           * @dev See {IERC20-approve}.
                           *
                           * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
                           * `transferFrom`. This is semantically equivalent to an infinite approval.
                           *
                           * Requirements:
                           *
                           * - `spender` cannot be the zero address.
                           */
                          function approve(address spender, uint256 amount) public virtual override returns (bool) {
                              address owner = _msgSender();
                              _approve(owner, spender, amount);
                              return true;
                          }
                          /**
                           * @dev See {IERC20-transferFrom}.
                           *
                           * Emits an {Approval} event indicating the updated allowance. This is not
                           * required by the EIP. See the note at the beginning of {ERC20}.
                           *
                           * NOTE: Does not update the allowance if the current allowance
                           * is the maximum `uint256`.
                           *
                           * Requirements:
                           *
                           * - `from` and `to` cannot be the zero address.
                           * - `from` must have a balance of at least `amount`.
                           * - the caller must have allowance for ``from``'s tokens of at least
                           * `amount`.
                           */
                          function transferFrom(address from, address to, uint256 amount) public virtual override returns (bool) {
                              address spender = _msgSender();
                              _spendAllowance(from, spender, amount);
                              _transfer(from, to, amount);
                              return true;
                          }
                          /**
                           * @dev Atomically increases the allowance granted to `spender` by the caller.
                           *
                           * This is an alternative to {approve} that can be used as a mitigation for
                           * problems described in {IERC20-approve}.
                           *
                           * Emits an {Approval} event indicating the updated allowance.
                           *
                           * Requirements:
                           *
                           * - `spender` cannot be the zero address.
                           */
                          function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
                              address owner = _msgSender();
                              _approve(owner, spender, allowance(owner, spender) + addedValue);
                              return true;
                          }
                          /**
                           * @dev Atomically decreases the allowance granted to `spender` by the caller.
                           *
                           * This is an alternative to {approve} that can be used as a mitigation for
                           * problems described in {IERC20-approve}.
                           *
                           * Emits an {Approval} event indicating the updated allowance.
                           *
                           * Requirements:
                           *
                           * - `spender` cannot be the zero address.
                           * - `spender` must have allowance for the caller of at least
                           * `subtractedValue`.
                           */
                          function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
                              address owner = _msgSender();
                              uint256 currentAllowance = allowance(owner, spender);
                              require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
                              unchecked {
                                  _approve(owner, spender, currentAllowance - subtractedValue);
                              }
                              return true;
                          }
                          /**
                           * @dev Moves `amount` of tokens from `from` to `to`.
                           *
                           * This internal function is equivalent to {transfer}, and can be used to
                           * e.g. implement automatic token fees, slashing mechanisms, etc.
                           *
                           * Emits a {Transfer} event.
                           *
                           * Requirements:
                           *
                           * - `from` cannot be the zero address.
                           * - `to` cannot be the zero address.
                           * - `from` must have a balance of at least `amount`.
                           */
                          function _transfer(address from, address to, uint256 amount) internal virtual {
                              require(from != address(0), "ERC20: transfer from the zero address");
                              require(to != address(0), "ERC20: transfer to the zero address");
                              _beforeTokenTransfer(from, to, amount);
                              uint256 fromBalance = _balances[from];
                              require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
                              unchecked {
                                  _balances[from] = fromBalance - amount;
                                  // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
                                  // decrementing then incrementing.
                                  _balances[to] += amount;
                              }
                              emit Transfer(from, to, amount);
                              _afterTokenTransfer(from, to, amount);
                          }
                          /** @dev Creates `amount` tokens and assigns them to `account`, increasing
                           * the total supply.
                           *
                           * Emits a {Transfer} event with `from` set to the zero address.
                           *
                           * Requirements:
                           *
                           * - `account` cannot be the zero address.
                           */
                          function _mint(address account, uint256 amount) internal virtual {
                              require(account != address(0), "ERC20: mint to the zero address");
                              _beforeTokenTransfer(address(0), account, amount);
                              _totalSupply += amount;
                              unchecked {
                                  // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
                                  _balances[account] += amount;
                              }
                              emit Transfer(address(0), account, amount);
                              _afterTokenTransfer(address(0), account, amount);
                          }
                          /**
                           * @dev Destroys `amount` tokens from `account`, reducing the
                           * total supply.
                           *
                           * Emits a {Transfer} event with `to` set to the zero address.
                           *
                           * Requirements:
                           *
                           * - `account` cannot be the zero address.
                           * - `account` must have at least `amount` tokens.
                           */
                          function _burn(address account, uint256 amount) internal virtual {
                              require(account != address(0), "ERC20: burn from the zero address");
                              _beforeTokenTransfer(account, address(0), amount);
                              uint256 accountBalance = _balances[account];
                              require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
                              unchecked {
                                  _balances[account] = accountBalance - amount;
                                  // Overflow not possible: amount <= accountBalance <= totalSupply.
                                  _totalSupply -= amount;
                              }
                              emit Transfer(account, address(0), amount);
                              _afterTokenTransfer(account, address(0), amount);
                          }
                          /**
                           * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
                           *
                           * This internal function is equivalent to `approve`, and can be used to
                           * e.g. set automatic allowances for certain subsystems, etc.
                           *
                           * Emits an {Approval} event.
                           *
                           * Requirements:
                           *
                           * - `owner` cannot be the zero address.
                           * - `spender` cannot be the zero address.
                           */
                          function _approve(address owner, address spender, uint256 amount) internal virtual {
                              require(owner != address(0), "ERC20: approve from the zero address");
                              require(spender != address(0), "ERC20: approve to the zero address");
                              _allowances[owner][spender] = amount;
                              emit Approval(owner, spender, amount);
                          }
                          /**
                           * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
                           *
                           * Does not update the allowance amount in case of infinite allowance.
                           * Revert if not enough allowance is available.
                           *
                           * Might emit an {Approval} event.
                           */
                          function _spendAllowance(address owner, address spender, uint256 amount) internal virtual {
                              uint256 currentAllowance = allowance(owner, spender);
                              if (currentAllowance != type(uint256).max) {
                                  require(currentAllowance >= amount, "ERC20: insufficient allowance");
                                  unchecked {
                                      _approve(owner, spender, currentAllowance - amount);
                                  }
                              }
                          }
                          /**
                           * @dev Hook that is called before any transfer of tokens. This includes
                           * minting and burning.
                           *
                           * Calling conditions:
                           *
                           * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
                           * will be transferred to `to`.
                           * - when `from` is zero, `amount` tokens will be minted for `to`.
                           * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
                           * - `from` and `to` are never both zero.
                           *
                           * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
                           */
                          function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual {}
                          /**
                           * @dev Hook that is called after any transfer of tokens. This includes
                           * minting and burning.
                           *
                           * Calling conditions:
                           *
                           * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
                           * has been transferred to `to`.
                           * - when `from` is zero, `amount` tokens have been minted for `to`.
                           * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
                           * - `from` and `to` are never both zero.
                           *
                           * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
                           */
                          function _afterTokenTransfer(address from, address to, uint256 amount) internal virtual {}
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/extensions/ERC20Burnable.sol)
                      pragma solidity ^0.8.0;
                      import "../ERC20.sol";
                      import "../../../utils/Context.sol";
                      /**
                       * @dev Extension of {ERC20} that allows token holders to destroy both their own
                       * tokens and those that they have an allowance for, in a way that can be
                       * recognized off-chain (via event analysis).
                       */
                      abstract contract ERC20Burnable is Context, ERC20 {
                          /**
                           * @dev Destroys `amount` tokens from the caller.
                           *
                           * See {ERC20-_burn}.
                           */
                          function burn(uint256 amount) public virtual {
                              _burn(_msgSender(), amount);
                          }
                          /**
                           * @dev Destroys `amount` tokens from `account`, deducting from the caller's
                           * allowance.
                           *
                           * See {ERC20-_burn} and {ERC20-allowance}.
                           *
                           * Requirements:
                           *
                           * - the caller must have allowance for ``accounts``'s tokens of at least
                           * `amount`.
                           */
                          function burnFrom(address account, uint256 amount) public virtual {
                              _spendAllowance(account, _msgSender(), amount);
                              _burn(account, amount);
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.4) (token/ERC20/extensions/ERC20Permit.sol)
                      pragma solidity ^0.8.0;
                      import "./IERC20Permit.sol";
                      import "../ERC20.sol";
                      import "../../../utils/cryptography/ECDSA.sol";
                      import "../../../utils/cryptography/EIP712.sol";
                      import "../../../utils/Counters.sol";
                      /**
                       * @dev Implementation of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
                       * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
                       *
                       * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
                       * presenting a message signed by the account. By not relying on `{IERC20-approve}`, the token holder account doesn't
                       * need to send a transaction, and thus is not required to hold Ether at all.
                       *
                       * _Available since v3.4._
                       */
                      abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
                          using Counters for Counters.Counter;
                          mapping(address => Counters.Counter) private _nonces;
                          // solhint-disable-next-line var-name-mixedcase
                          bytes32 private constant _PERMIT_TYPEHASH =
                              keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
                          /**
                           * @dev In previous versions `_PERMIT_TYPEHASH` was declared as `immutable`.
                           * However, to ensure consistency with the upgradeable transpiler, we will continue
                           * to reserve a slot.
                           * @custom:oz-renamed-from _PERMIT_TYPEHASH
                           */
                          // solhint-disable-next-line var-name-mixedcase
                          bytes32 private _PERMIT_TYPEHASH_DEPRECATED_SLOT;
                          /**
                           * @dev Initializes the {EIP712} domain separator using the `name` parameter, and setting `version` to `"1"`.
                           *
                           * It's a good idea to use the same `name` that is defined as the ERC20 token name.
                           */
                          constructor(string memory name) EIP712(name, "1") {}
                          /**
                           * @inheritdoc IERC20Permit
                           */
                          function permit(
                              address owner,
                              address spender,
                              uint256 value,
                              uint256 deadline,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) public virtual override {
                              require(block.timestamp <= deadline, "ERC20Permit: expired deadline");
                              bytes32 structHash = keccak256(abi.encode(_PERMIT_TYPEHASH, owner, spender, value, _useNonce(owner), deadline));
                              bytes32 hash = _hashTypedDataV4(structHash);
                              address signer = ECDSA.recover(hash, v, r, s);
                              require(signer == owner, "ERC20Permit: invalid signature");
                              _approve(owner, spender, value);
                          }
                          /**
                           * @inheritdoc IERC20Permit
                           */
                          function nonces(address owner) public view virtual override returns (uint256) {
                              return _nonces[owner].current();
                          }
                          /**
                           * @inheritdoc IERC20Permit
                           */
                          // solhint-disable-next-line func-name-mixedcase
                          function DOMAIN_SEPARATOR() external view override returns (bytes32) {
                              return _domainSeparatorV4();
                          }
                          /**
                           * @dev "Consume a nonce": return the current value and increment.
                           *
                           * _Available since v4.1._
                           */
                          function _useNonce(address owner) internal virtual returns (uint256 current) {
                              Counters.Counter storage nonce = _nonces[owner];
                              current = nonce.current();
                              nonce.increment();
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable2Step.sol)
                      pragma solidity ^0.8.0;
                      import "./Ownable.sol";
                      /**
                       * @dev Contract module which provides access control mechanism, where
                       * there is an account (an owner) that can be granted exclusive access to
                       * specific functions.
                       *
                       * By default, the owner account will be the one that deploys the contract. This
                       * can later be changed with {transferOwnership} and {acceptOwnership}.
                       *
                       * This module is used through inheritance. It will make available all functions
                       * from parent (Ownable).
                       */
                      abstract contract Ownable2Step is Ownable {
                          address private _pendingOwner;
                          event OwnershipTransferStarted(address indexed previousOwner, address indexed newOwner);
                          /**
                           * @dev Returns the address of the pending owner.
                           */
                          function pendingOwner() public view virtual returns (address) {
                              return _pendingOwner;
                          }
                          /**
                           * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
                           * Can only be called by the current owner.
                           */
                          function transferOwnership(address newOwner) public virtual override onlyOwner {
                              _pendingOwner = newOwner;
                              emit OwnershipTransferStarted(owner(), newOwner);
                          }
                          /**
                           * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
                           * Internal function without access restriction.
                           */
                          function _transferOwnership(address newOwner) internal virtual override {
                              delete _pendingOwner;
                              super._transferOwnership(newOwner);
                          }
                          /**
                           * @dev The new owner accepts the ownership transfer.
                           */
                          function acceptOwnership() public virtual {
                              address sender = _msgSender();
                              require(pendingOwner() == sender, "Ownable2Step: caller is not the new owner");
                              _transferOwnership(sender);
                          }
                      }
                      // SPDX-License-Identifier: GPL-3.0
                      pragma solidity 0.8.20;
                      interface IENADefinitions {
                        /// @notice Event emitted when a new ENA token is minted (inflation) by the owner
                        event Mint(address indexed to, uint256 amount);
                        /// @notice This error is returned if the zero address is used
                        error ZeroAddressException();
                        /// @notice This error is returned if mint is called within 1 year of last mint
                        error MintWaitPeriodInProgress();
                        /// @notice This error is returned if the owner tries to renounce ownership
                        error CantRenounceOwnership();
                        /// @notice This error is returned if the max inflation rate is exceeded on mint
                        error MaxInflationExceeded();
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)
                      pragma solidity ^0.8.0;
                      /**
                       * @dev Interface of the ERC20 standard as defined in the EIP.
                       */
                      interface IERC20 {
                          /**
                           * @dev Emitted when `value` tokens are moved from one account (`from`) to
                           * another (`to`).
                           *
                           * Note that `value` may be zero.
                           */
                          event Transfer(address indexed from, address indexed to, uint256 value);
                          /**
                           * @dev Emitted when the allowance of a `spender` for an `owner` is set by
                           * a call to {approve}. `value` is the new allowance.
                           */
                          event Approval(address indexed owner, address indexed spender, uint256 value);
                          /**
                           * @dev Returns the amount of tokens in existence.
                           */
                          function totalSupply() external view returns (uint256);
                          /**
                           * @dev Returns the amount of tokens owned by `account`.
                           */
                          function balanceOf(address account) external view returns (uint256);
                          /**
                           * @dev Moves `amount` tokens from the caller's account to `to`.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * Emits a {Transfer} event.
                           */
                          function transfer(address to, uint256 amount) external returns (bool);
                          /**
                           * @dev Returns the remaining number of tokens that `spender` will be
                           * allowed to spend on behalf of `owner` through {transferFrom}. This is
                           * zero by default.
                           *
                           * This value changes when {approve} or {transferFrom} are called.
                           */
                          function allowance(address owner, address spender) external view returns (uint256);
                          /**
                           * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * IMPORTANT: Beware that changing an allowance with this method brings the risk
                           * that someone may use both the old and the new allowance by unfortunate
                           * transaction ordering. One possible solution to mitigate this race
                           * condition is to first reduce the spender's allowance to 0 and set the
                           * desired value afterwards:
                           * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
                           *
                           * Emits an {Approval} event.
                           */
                          function approve(address spender, uint256 amount) external returns (bool);
                          /**
                           * @dev Moves `amount` tokens from `from` to `to` using the
                           * allowance mechanism. `amount` is then deducted from the caller's
                           * allowance.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * Emits a {Transfer} event.
                           */
                          function transferFrom(address from, address to, uint256 amount) external returns (bool);
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)
                      pragma solidity ^0.8.0;
                      import "../IERC20.sol";
                      /**
                       * @dev Interface for the optional metadata functions from the ERC20 standard.
                       *
                       * _Available since v4.1._
                       */
                      interface IERC20Metadata is IERC20 {
                          /**
                           * @dev Returns the name of the token.
                           */
                          function name() external view returns (string memory);
                          /**
                           * @dev Returns the symbol of the token.
                           */
                          function symbol() external view returns (string memory);
                          /**
                           * @dev Returns the decimals places of the token.
                           */
                          function decimals() external view returns (uint8);
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.4) (utils/Context.sol)
                      pragma solidity ^0.8.0;
                      /**
                       * @dev Provides information about the current execution context, including the
                       * sender of the transaction and its data. While these are generally available
                       * via msg.sender and msg.data, they should not be accessed in such a direct
                       * manner, since when dealing with meta-transactions the account sending and
                       * paying for execution may not be the actual sender (as far as an application
                       * is concerned).
                       *
                       * This contract is only required for intermediate, library-like contracts.
                       */
                      abstract contract Context {
                          function _msgSender() internal view virtual returns (address) {
                              return msg.sender;
                          }
                          function _msgData() internal view virtual returns (bytes calldata) {
                              return msg.data;
                          }
                          function _contextSuffixLength() internal view virtual returns (uint256) {
                              return 0;
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.4) (token/ERC20/extensions/IERC20Permit.sol)
                      pragma solidity ^0.8.0;
                      /**
                       * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
                       * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
                       *
                       * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
                       * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
                       * need to send a transaction, and thus is not required to hold Ether at all.
                       *
                       * ==== Security Considerations
                       *
                       * There are two important considerations concerning the use of `permit`. The first is that a valid permit signature
                       * expresses an allowance, and it should not be assumed to convey additional meaning. In particular, it should not be
                       * considered as an intention to spend the allowance in any specific way. The second is that because permits have
                       * built-in replay protection and can be submitted by anyone, they can be frontrun. A protocol that uses permits should
                       * take this into consideration and allow a `permit` call to fail. Combining these two aspects, a pattern that may be
                       * generally recommended is:
                       *
                       * ```solidity
                       * function doThingWithPermit(..., uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s) public {
                       *     try token.permit(msg.sender, address(this), value, deadline, v, r, s) {} catch {}
                       *     doThing(..., value);
                       * }
                       *
                       * function doThing(..., uint256 value) public {
                       *     token.safeTransferFrom(msg.sender, address(this), value);
                       *     ...
                       * }
                       * ```
                       *
                       * Observe that: 1) `msg.sender` is used as the owner, leaving no ambiguity as to the signer intent, and 2) the use of
                       * `try/catch` allows the permit to fail and makes the code tolerant to frontrunning. (See also
                       * {SafeERC20-safeTransferFrom}).
                       *
                       * Additionally, note that smart contract wallets (such as Argent or Safe) are not able to produce permit signatures, so
                       * contracts should have entry points that don't rely on permit.
                       */
                      interface IERC20Permit {
                          /**
                           * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
                           * given ``owner``'s signed approval.
                           *
                           * IMPORTANT: The same issues {IERC20-approve} has related to transaction
                           * ordering also apply here.
                           *
                           * Emits an {Approval} event.
                           *
                           * Requirements:
                           *
                           * - `spender` cannot be the zero address.
                           * - `deadline` must be a timestamp in the future.
                           * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
                           * over the EIP712-formatted function arguments.
                           * - the signature must use ``owner``'s current nonce (see {nonces}).
                           *
                           * For more information on the signature format, see the
                           * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
                           * section].
                           *
                           * CAUTION: See Security Considerations above.
                           */
                          function permit(
                              address owner,
                              address spender,
                              uint256 value,
                              uint256 deadline,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) external;
                          /**
                           * @dev Returns the current nonce for `owner`. This value must be
                           * included whenever a signature is generated for {permit}.
                           *
                           * Every successful call to {permit} increases ``owner``'s nonce by one. This
                           * prevents a signature from being used multiple times.
                           */
                          function nonces(address owner) external view returns (uint256);
                          /**
                           * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
                           */
                          // solhint-disable-next-line func-name-mixedcase
                          function DOMAIN_SEPARATOR() external view returns (bytes32);
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (utils/cryptography/ECDSA.sol)
                      pragma solidity ^0.8.0;
                      import "../Strings.sol";
                      /**
                       * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
                       *
                       * These functions can be used to verify that a message was signed by the holder
                       * of the private keys of a given address.
                       */
                      library ECDSA {
                          enum RecoverError {
                              NoError,
                              InvalidSignature,
                              InvalidSignatureLength,
                              InvalidSignatureS,
                              InvalidSignatureV // Deprecated in v4.8
                          }
                          function _throwError(RecoverError error) private pure {
                              if (error == RecoverError.NoError) {
                                  return; // no error: do nothing
                              } else if (error == RecoverError.InvalidSignature) {
                                  revert("ECDSA: invalid signature");
                              } else if (error == RecoverError.InvalidSignatureLength) {
                                  revert("ECDSA: invalid signature length");
                              } else if (error == RecoverError.InvalidSignatureS) {
                                  revert("ECDSA: invalid signature 's' value");
                              }
                          }
                          /**
                           * @dev Returns the address that signed a hashed message (`hash`) with
                           * `signature` or error string. This address can then be used for verification purposes.
                           *
                           * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
                           * this function rejects them by requiring the `s` value to be in the lower
                           * half order, and the `v` value to be either 27 or 28.
                           *
                           * IMPORTANT: `hash` _must_ be the result of a hash operation for the
                           * verification to be secure: it is possible to craft signatures that
                           * recover to arbitrary addresses for non-hashed data. A safe way to ensure
                           * this is by receiving a hash of the original message (which may otherwise
                           * be too long), and then calling {toEthSignedMessageHash} on it.
                           *
                           * Documentation for signature generation:
                           * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
                           * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
                           *
                           * _Available since v4.3._
                           */
                          function tryRecover(bytes32 hash, bytes memory signature) internal pure returns (address, RecoverError) {
                              if (signature.length == 65) {
                                  bytes32 r;
                                  bytes32 s;
                                  uint8 v;
                                  // ecrecover takes the signature parameters, and the only way to get them
                                  // currently is to use assembly.
                                  /// @solidity memory-safe-assembly
                                  assembly {
                                      r := mload(add(signature, 0x20))
                                      s := mload(add(signature, 0x40))
                                      v := byte(0, mload(add(signature, 0x60)))
                                  }
                                  return tryRecover(hash, v, r, s);
                              } else {
                                  return (address(0), RecoverError.InvalidSignatureLength);
                              }
                          }
                          /**
                           * @dev Returns the address that signed a hashed message (`hash`) with
                           * `signature`. This address can then be used for verification purposes.
                           *
                           * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
                           * this function rejects them by requiring the `s` value to be in the lower
                           * half order, and the `v` value to be either 27 or 28.
                           *
                           * IMPORTANT: `hash` _must_ be the result of a hash operation for the
                           * verification to be secure: it is possible to craft signatures that
                           * recover to arbitrary addresses for non-hashed data. A safe way to ensure
                           * this is by receiving a hash of the original message (which may otherwise
                           * be too long), and then calling {toEthSignedMessageHash} on it.
                           */
                          function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
                              (address recovered, RecoverError error) = tryRecover(hash, signature);
                              _throwError(error);
                              return recovered;
                          }
                          /**
                           * @dev Overload of {ECDSA-tryRecover} that receives the `r` and `vs` short-signature fields separately.
                           *
                           * See https://eips.ethereum.org/EIPS/eip-2098[EIP-2098 short signatures]
                           *
                           * _Available since v4.3._
                           */
                          function tryRecover(bytes32 hash, bytes32 r, bytes32 vs) internal pure returns (address, RecoverError) {
                              bytes32 s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
                              uint8 v = uint8((uint256(vs) >> 255) + 27);
                              return tryRecover(hash, v, r, s);
                          }
                          /**
                           * @dev Overload of {ECDSA-recover} that receives the `r and `vs` short-signature fields separately.
                           *
                           * _Available since v4.2._
                           */
                          function recover(bytes32 hash, bytes32 r, bytes32 vs) internal pure returns (address) {
                              (address recovered, RecoverError error) = tryRecover(hash, r, vs);
                              _throwError(error);
                              return recovered;
                          }
                          /**
                           * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
                           * `r` and `s` signature fields separately.
                           *
                           * _Available since v4.3._
                           */
                          function tryRecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal pure returns (address, RecoverError) {
                              // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
                              // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
                              // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
                              // signatures from current libraries generate a unique signature with an s-value in the lower half order.
                              //
                              // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
                              // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
                              // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
                              // these malleable signatures as well.
                              if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
                                  return (address(0), RecoverError.InvalidSignatureS);
                              }
                              // If the signature is valid (and not malleable), return the signer address
                              address signer = ecrecover(hash, v, r, s);
                              if (signer == address(0)) {
                                  return (address(0), RecoverError.InvalidSignature);
                              }
                              return (signer, RecoverError.NoError);
                          }
                          /**
                           * @dev Overload of {ECDSA-recover} that receives the `v`,
                           * `r` and `s` signature fields separately.
                           */
                          function recover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal pure returns (address) {
                              (address recovered, RecoverError error) = tryRecover(hash, v, r, s);
                              _throwError(error);
                              return recovered;
                          }
                          /**
                           * @dev Returns an Ethereum Signed Message, created from a `hash`. This
                           * produces hash corresponding to the one signed with the
                           * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
                           * JSON-RPC method as part of EIP-191.
                           *
                           * See {recover}.
                           */
                          function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32 message) {
                              // 32 is the length in bytes of hash,
                              // enforced by the type signature above
                              /// @solidity memory-safe-assembly
                              assembly {
                                  mstore(0x00, "\\x19Ethereum Signed Message:\
                      32")
                                  mstore(0x1c, hash)
                                  message := keccak256(0x00, 0x3c)
                              }
                          }
                          /**
                           * @dev Returns an Ethereum Signed Message, created from `s`. This
                           * produces hash corresponding to the one signed with the
                           * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
                           * JSON-RPC method as part of EIP-191.
                           *
                           * See {recover}.
                           */
                          function toEthSignedMessageHash(bytes memory s) internal pure returns (bytes32) {
                              return keccak256(abi.encodePacked("\\x19Ethereum Signed Message:\
                      ", Strings.toString(s.length), s));
                          }
                          /**
                           * @dev Returns an Ethereum Signed Typed Data, created from a
                           * `domainSeparator` and a `structHash`. This produces hash corresponding
                           * to the one signed with the
                           * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`]
                           * JSON-RPC method as part of EIP-712.
                           *
                           * See {recover}.
                           */
                          function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash) internal pure returns (bytes32 data) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  let ptr := mload(0x40)
                                  mstore(ptr, "\\x19\\x01")
                                  mstore(add(ptr, 0x02), domainSeparator)
                                  mstore(add(ptr, 0x22), structHash)
                                  data := keccak256(ptr, 0x42)
                              }
                          }
                          /**
                           * @dev Returns an Ethereum Signed Data with intended validator, created from a
                           * `validator` and `data` according to the version 0 of EIP-191.
                           *
                           * See {recover}.
                           */
                          function toDataWithIntendedValidatorHash(address validator, bytes memory data) internal pure returns (bytes32) {
                              return keccak256(abi.encodePacked("\\x19\\x00", validator, data));
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (utils/cryptography/EIP712.sol)
                      pragma solidity ^0.8.8;
                      import "./ECDSA.sol";
                      import "../ShortStrings.sol";
                      import "../../interfaces/IERC5267.sol";
                      /**
                       * @dev https://eips.ethereum.org/EIPS/eip-712[EIP 712] is a standard for hashing and signing of typed structured data.
                       *
                       * The encoding specified in the EIP is very generic, and such a generic implementation in Solidity is not feasible,
                       * thus this contract does not implement the encoding itself. Protocols need to implement the type-specific encoding
                       * they need in their contracts using a combination of `abi.encode` and `keccak256`.
                       *
                       * This contract implements the EIP 712 domain separator ({_domainSeparatorV4}) that is used as part of the encoding
                       * scheme, and the final step of the encoding to obtain the message digest that is then signed via ECDSA
                       * ({_hashTypedDataV4}).
                       *
                       * The implementation of the domain separator was designed to be as efficient as possible while still properly updating
                       * the chain id to protect against replay attacks on an eventual fork of the chain.
                       *
                       * NOTE: This contract implements the version of the encoding known as "v4", as implemented by the JSON RPC method
                       * https://docs.metamask.io/guide/signing-data.html[`eth_signTypedDataV4` in MetaMask].
                       *
                       * NOTE: In the upgradeable version of this contract, the cached values will correspond to the address, and the domain
                       * separator of the implementation contract. This will cause the `_domainSeparatorV4` function to always rebuild the
                       * separator from the immutable values, which is cheaper than accessing a cached version in cold storage.
                       *
                       * _Available since v3.4._
                       *
                       * @custom:oz-upgrades-unsafe-allow state-variable-immutable state-variable-assignment
                       */
                      abstract contract EIP712 is IERC5267 {
                          using ShortStrings for *;
                          bytes32 private constant _TYPE_HASH =
                              keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)");
                          // Cache the domain separator as an immutable value, but also store the chain id that it corresponds to, in order to
                          // invalidate the cached domain separator if the chain id changes.
                          bytes32 private immutable _cachedDomainSeparator;
                          uint256 private immutable _cachedChainId;
                          address private immutable _cachedThis;
                          bytes32 private immutable _hashedName;
                          bytes32 private immutable _hashedVersion;
                          ShortString private immutable _name;
                          ShortString private immutable _version;
                          string private _nameFallback;
                          string private _versionFallback;
                          /**
                           * @dev Initializes the domain separator and parameter caches.
                           *
                           * The meaning of `name` and `version` is specified in
                           * https://eips.ethereum.org/EIPS/eip-712#definition-of-domainseparator[EIP 712]:
                           *
                           * - `name`: the user readable name of the signing domain, i.e. the name of the DApp or the protocol.
                           * - `version`: the current major version of the signing domain.
                           *
                           * NOTE: These parameters cannot be changed except through a xref:learn::upgrading-smart-contracts.adoc[smart
                           * contract upgrade].
                           */
                          constructor(string memory name, string memory version) {
                              _name = name.toShortStringWithFallback(_nameFallback);
                              _version = version.toShortStringWithFallback(_versionFallback);
                              _hashedName = keccak256(bytes(name));
                              _hashedVersion = keccak256(bytes(version));
                              _cachedChainId = block.chainid;
                              _cachedDomainSeparator = _buildDomainSeparator();
                              _cachedThis = address(this);
                          }
                          /**
                           * @dev Returns the domain separator for the current chain.
                           */
                          function _domainSeparatorV4() internal view returns (bytes32) {
                              if (address(this) == _cachedThis && block.chainid == _cachedChainId) {
                                  return _cachedDomainSeparator;
                              } else {
                                  return _buildDomainSeparator();
                              }
                          }
                          function _buildDomainSeparator() private view returns (bytes32) {
                              return keccak256(abi.encode(_TYPE_HASH, _hashedName, _hashedVersion, block.chainid, address(this)));
                          }
                          /**
                           * @dev Given an already https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct[hashed struct], this
                           * function returns the hash of the fully encoded EIP712 message for this domain.
                           *
                           * This hash can be used together with {ECDSA-recover} to obtain the signer of a message. For example:
                           *
                           * ```solidity
                           * bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
                           *     keccak256("Mail(address to,string contents)"),
                           *     mailTo,
                           *     keccak256(bytes(mailContents))
                           * )));
                           * address signer = ECDSA.recover(digest, signature);
                           * ```
                           */
                          function _hashTypedDataV4(bytes32 structHash) internal view virtual returns (bytes32) {
                              return ECDSA.toTypedDataHash(_domainSeparatorV4(), structHash);
                          }
                          /**
                           * @dev See {EIP-5267}.
                           *
                           * _Available since v4.9._
                           */
                          function eip712Domain()
                              public
                              view
                              virtual
                              override
                              returns (
                                  bytes1 fields,
                                  string memory name,
                                  string memory version,
                                  uint256 chainId,
                                  address verifyingContract,
                                  bytes32 salt,
                                  uint256[] memory extensions
                              )
                          {
                              return (
                                  hex"0f", // 01111
                                  _name.toStringWithFallback(_nameFallback),
                                  _version.toStringWithFallback(_versionFallback),
                                  block.chainid,
                                  address(this),
                                  bytes32(0),
                                  new uint256[](0)
                              );
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts v4.4.1 (utils/Counters.sol)
                      pragma solidity ^0.8.0;
                      /**
                       * @title Counters
                       * @author Matt Condon (@shrugs)
                       * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
                       * of elements in a mapping, issuing ERC721 ids, or counting request ids.
                       *
                       * Include with `using Counters for Counters.Counter;`
                       */
                      library Counters {
                          struct Counter {
                              // This variable should never be directly accessed by users of the library: interactions must be restricted to
                              // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
                              // this feature: see https://github.com/ethereum/solidity/issues/4637
                              uint256 _value; // default: 0
                          }
                          function current(Counter storage counter) internal view returns (uint256) {
                              return counter._value;
                          }
                          function increment(Counter storage counter) internal {
                              unchecked {
                                  counter._value += 1;
                              }
                          }
                          function decrement(Counter storage counter) internal {
                              uint256 value = counter._value;
                              require(value > 0, "Counter: decrement overflow");
                              unchecked {
                                  counter._value = value - 1;
                              }
                          }
                          function reset(Counter storage counter) internal {
                              counter._value = 0;
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable.sol)
                      pragma solidity ^0.8.0;
                      import "../utils/Context.sol";
                      /**
                       * @dev Contract module which provides a basic access control mechanism, where
                       * there is an account (an owner) that can be granted exclusive access to
                       * specific functions.
                       *
                       * By default, the owner account will be the one that deploys the contract. This
                       * can later be changed with {transferOwnership}.
                       *
                       * This module is used through inheritance. It will make available the modifier
                       * `onlyOwner`, which can be applied to your functions to restrict their use to
                       * the owner.
                       */
                      abstract contract Ownable is Context {
                          address private _owner;
                          event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
                          /**
                           * @dev Initializes the contract setting the deployer as the initial owner.
                           */
                          constructor() {
                              _transferOwnership(_msgSender());
                          }
                          /**
                           * @dev Throws if called by any account other than the owner.
                           */
                          modifier onlyOwner() {
                              _checkOwner();
                              _;
                          }
                          /**
                           * @dev Returns the address of the current owner.
                           */
                          function owner() public view virtual returns (address) {
                              return _owner;
                          }
                          /**
                           * @dev Throws if the sender is not the owner.
                           */
                          function _checkOwner() internal view virtual {
                              require(owner() == _msgSender(), "Ownable: caller is not the owner");
                          }
                          /**
                           * @dev Leaves the contract without owner. It will not be possible to call
                           * `onlyOwner` functions. Can only be called by the current owner.
                           *
                           * NOTE: Renouncing ownership will leave the contract without an owner,
                           * thereby disabling any functionality that is only available to the owner.
                           */
                          function renounceOwnership() public virtual onlyOwner {
                              _transferOwnership(address(0));
                          }
                          /**
                           * @dev Transfers ownership of the contract to a new account (`newOwner`).
                           * Can only be called by the current owner.
                           */
                          function transferOwnership(address newOwner) public virtual onlyOwner {
                              require(newOwner != address(0), "Ownable: new owner is the zero address");
                              _transferOwnership(newOwner);
                          }
                          /**
                           * @dev Transfers ownership of the contract to a new account (`newOwner`).
                           * Internal function without access restriction.
                           */
                          function _transferOwnership(address newOwner) internal virtual {
                              address oldOwner = _owner;
                              _owner = newOwner;
                              emit OwnershipTransferred(oldOwner, newOwner);
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (utils/Strings.sol)
                      pragma solidity ^0.8.0;
                      import "./math/Math.sol";
                      import "./math/SignedMath.sol";
                      /**
                       * @dev String operations.
                       */
                      library Strings {
                          bytes16 private constant _SYMBOLS = "0123456789abcdef";
                          uint8 private constant _ADDRESS_LENGTH = 20;
                          /**
                           * @dev Converts a `uint256` to its ASCII `string` decimal representation.
                           */
                          function toString(uint256 value) internal pure returns (string memory) {
                              unchecked {
                                  uint256 length = Math.log10(value) + 1;
                                  string memory buffer = new string(length);
                                  uint256 ptr;
                                  /// @solidity memory-safe-assembly
                                  assembly {
                                      ptr := add(buffer, add(32, length))
                                  }
                                  while (true) {
                                      ptr--;
                                      /// @solidity memory-safe-assembly
                                      assembly {
                                          mstore8(ptr, byte(mod(value, 10), _SYMBOLS))
                                      }
                                      value /= 10;
                                      if (value == 0) break;
                                  }
                                  return buffer;
                              }
                          }
                          /**
                           * @dev Converts a `int256` to its ASCII `string` decimal representation.
                           */
                          function toString(int256 value) internal pure returns (string memory) {
                              return string(abi.encodePacked(value < 0 ? "-" : "", toString(SignedMath.abs(value))));
                          }
                          /**
                           * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
                           */
                          function toHexString(uint256 value) internal pure returns (string memory) {
                              unchecked {
                                  return toHexString(value, Math.log256(value) + 1);
                              }
                          }
                          /**
                           * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
                           */
                          function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
                              bytes memory buffer = new bytes(2 * length + 2);
                              buffer[0] = "0";
                              buffer[1] = "x";
                              for (uint256 i = 2 * length + 1; i > 1; --i) {
                                  buffer[i] = _SYMBOLS[value & 0xf];
                                  value >>= 4;
                              }
                              require(value == 0, "Strings: hex length insufficient");
                              return string(buffer);
                          }
                          /**
                           * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
                           */
                          function toHexString(address addr) internal pure returns (string memory) {
                              return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
                          }
                          /**
                           * @dev Returns true if the two strings are equal.
                           */
                          function equal(string memory a, string memory b) internal pure returns (bool) {
                              return keccak256(bytes(a)) == keccak256(bytes(b));
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (utils/ShortStrings.sol)
                      pragma solidity ^0.8.8;
                      import "./StorageSlot.sol";
                      // | string  | 0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA   |
                      // | length  | 0x                                                              BB |
                      type ShortString is bytes32;
                      /**
                       * @dev This library provides functions to convert short memory strings
                       * into a `ShortString` type that can be used as an immutable variable.
                       *
                       * Strings of arbitrary length can be optimized using this library if
                       * they are short enough (up to 31 bytes) by packing them with their
                       * length (1 byte) in a single EVM word (32 bytes). Additionally, a
                       * fallback mechanism can be used for every other case.
                       *
                       * Usage example:
                       *
                       * ```solidity
                       * contract Named {
                       *     using ShortStrings for *;
                       *
                       *     ShortString private immutable _name;
                       *     string private _nameFallback;
                       *
                       *     constructor(string memory contractName) {
                       *         _name = contractName.toShortStringWithFallback(_nameFallback);
                       *     }
                       *
                       *     function name() external view returns (string memory) {
                       *         return _name.toStringWithFallback(_nameFallback);
                       *     }
                       * }
                       * ```
                       */
                      library ShortStrings {
                          // Used as an identifier for strings longer than 31 bytes.
                          bytes32 private constant _FALLBACK_SENTINEL = 0x00000000000000000000000000000000000000000000000000000000000000FF;
                          error StringTooLong(string str);
                          error InvalidShortString();
                          /**
                           * @dev Encode a string of at most 31 chars into a `ShortString`.
                           *
                           * This will trigger a `StringTooLong` error is the input string is too long.
                           */
                          function toShortString(string memory str) internal pure returns (ShortString) {
                              bytes memory bstr = bytes(str);
                              if (bstr.length > 31) {
                                  revert StringTooLong(str);
                              }
                              return ShortString.wrap(bytes32(uint256(bytes32(bstr)) | bstr.length));
                          }
                          /**
                           * @dev Decode a `ShortString` back to a "normal" string.
                           */
                          function toString(ShortString sstr) internal pure returns (string memory) {
                              uint256 len = byteLength(sstr);
                              // using `new string(len)` would work locally but is not memory safe.
                              string memory str = new string(32);
                              /// @solidity memory-safe-assembly
                              assembly {
                                  mstore(str, len)
                                  mstore(add(str, 0x20), sstr)
                              }
                              return str;
                          }
                          /**
                           * @dev Return the length of a `ShortString`.
                           */
                          function byteLength(ShortString sstr) internal pure returns (uint256) {
                              uint256 result = uint256(ShortString.unwrap(sstr)) & 0xFF;
                              if (result > 31) {
                                  revert InvalidShortString();
                              }
                              return result;
                          }
                          /**
                           * @dev Encode a string into a `ShortString`, or write it to storage if it is too long.
                           */
                          function toShortStringWithFallback(string memory value, string storage store) internal returns (ShortString) {
                              if (bytes(value).length < 32) {
                                  return toShortString(value);
                              } else {
                                  StorageSlot.getStringSlot(store).value = value;
                                  return ShortString.wrap(_FALLBACK_SENTINEL);
                              }
                          }
                          /**
                           * @dev Decode a string that was encoded to `ShortString` or written to storage using {setWithFallback}.
                           */
                          function toStringWithFallback(ShortString value, string storage store) internal pure returns (string memory) {
                              if (ShortString.unwrap(value) != _FALLBACK_SENTINEL) {
                                  return toString(value);
                              } else {
                                  return store;
                              }
                          }
                          /**
                           * @dev Return the length of a string that was encoded to `ShortString` or written to storage using {setWithFallback}.
                           *
                           * WARNING: This will return the "byte length" of the string. This may not reflect the actual length in terms of
                           * actual characters as the UTF-8 encoding of a single character can span over multiple bytes.
                           */
                          function byteLengthWithFallback(ShortString value, string storage store) internal view returns (uint256) {
                              if (ShortString.unwrap(value) != _FALLBACK_SENTINEL) {
                                  return byteLength(value);
                              } else {
                                  return bytes(store).length;
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (interfaces/IERC5267.sol)
                      pragma solidity ^0.8.0;
                      interface IERC5267 {
                          /**
                           * @dev MAY be emitted to signal that the domain could have changed.
                           */
                          event EIP712DomainChanged();
                          /**
                           * @dev returns the fields and values that describe the domain separator used by this contract for EIP-712
                           * signature.
                           */
                          function eip712Domain()
                              external
                              view
                              returns (
                                  bytes1 fields,
                                  string memory name,
                                  string memory version,
                                  uint256 chainId,
                                  address verifyingContract,
                                  bytes32 salt,
                                  uint256[] memory extensions
                              );
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (utils/math/Math.sol)
                      pragma solidity ^0.8.0;
                      /**
                       * @dev Standard math utilities missing in the Solidity language.
                       */
                      library Math {
                          enum Rounding {
                              Down, // Toward negative infinity
                              Up, // Toward infinity
                              Zero // Toward zero
                          }
                          /**
                           * @dev Returns the largest of two numbers.
                           */
                          function max(uint256 a, uint256 b) internal pure returns (uint256) {
                              return a > b ? a : b;
                          }
                          /**
                           * @dev Returns the smallest of two numbers.
                           */
                          function min(uint256 a, uint256 b) internal pure returns (uint256) {
                              return a < b ? a : b;
                          }
                          /**
                           * @dev Returns the average of two numbers. The result is rounded towards
                           * zero.
                           */
                          function average(uint256 a, uint256 b) internal pure returns (uint256) {
                              // (a + b) / 2 can overflow.
                              return (a & b) + (a ^ b) / 2;
                          }
                          /**
                           * @dev Returns the ceiling of the division of two numbers.
                           *
                           * This differs from standard division with `/` in that it rounds up instead
                           * of rounding down.
                           */
                          function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
                              // (a + b - 1) / b can overflow on addition, so we distribute.
                              return a == 0 ? 0 : (a - 1) / b + 1;
                          }
                          /**
                           * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
                           * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
                           * with further edits by Uniswap Labs also under MIT license.
                           */
                          function mulDiv(uint256 x, uint256 y, uint256 denominator) internal pure returns (uint256 result) {
                              unchecked {
                                  // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
                                  // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
                                  // variables such that product = prod1 * 2^256 + prod0.
                                  uint256 prod0; // Least significant 256 bits of the product
                                  uint256 prod1; // Most significant 256 bits of the product
                                  assembly {
                                      let mm := mulmod(x, y, not(0))
                                      prod0 := mul(x, y)
                                      prod1 := sub(sub(mm, prod0), lt(mm, prod0))
                                  }
                                  // Handle non-overflow cases, 256 by 256 division.
                                  if (prod1 == 0) {
                                      // Solidity will revert if denominator == 0, unlike the div opcode on its own.
                                      // The surrounding unchecked block does not change this fact.
                                      // See https://docs.soliditylang.org/en/latest/control-structures.html#checked-or-unchecked-arithmetic.
                                      return prod0 / denominator;
                                  }
                                  // Make sure the result is less than 2^256. Also prevents denominator == 0.
                                  require(denominator > prod1, "Math: mulDiv overflow");
                                  ///////////////////////////////////////////////
                                  // 512 by 256 division.
                                  ///////////////////////////////////////////////
                                  // Make division exact by subtracting the remainder from [prod1 prod0].
                                  uint256 remainder;
                                  assembly {
                                      // Compute remainder using mulmod.
                                      remainder := mulmod(x, y, denominator)
                                      // Subtract 256 bit number from 512 bit number.
                                      prod1 := sub(prod1, gt(remainder, prod0))
                                      prod0 := sub(prod0, remainder)
                                  }
                                  // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
                                  // See https://cs.stackexchange.com/q/138556/92363.
                                  // Does not overflow because the denominator cannot be zero at this stage in the function.
                                  uint256 twos = denominator & (~denominator + 1);
                                  assembly {
                                      // Divide denominator by twos.
                                      denominator := div(denominator, twos)
                                      // Divide [prod1 prod0] by twos.
                                      prod0 := div(prod0, twos)
                                      // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                                      twos := add(div(sub(0, twos), twos), 1)
                                  }
                                  // Shift in bits from prod1 into prod0.
                                  prod0 |= prod1 * twos;
                                  // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
                                  // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
                                  // four bits. That is, denominator * inv = 1 mod 2^4.
                                  uint256 inverse = (3 * denominator) ^ 2;
                                  // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
                                  // in modular arithmetic, doubling the correct bits in each step.
                                  inverse *= 2 - denominator * inverse; // inverse mod 2^8
                                  inverse *= 2 - denominator * inverse; // inverse mod 2^16
                                  inverse *= 2 - denominator * inverse; // inverse mod 2^32
                                  inverse *= 2 - denominator * inverse; // inverse mod 2^64
                                  inverse *= 2 - denominator * inverse; // inverse mod 2^128
                                  inverse *= 2 - denominator * inverse; // inverse mod 2^256
                                  // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
                                  // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
                                  // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
                                  // is no longer required.
                                  result = prod0 * inverse;
                                  return result;
                              }
                          }
                          /**
                           * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
                           */
                          function mulDiv(uint256 x, uint256 y, uint256 denominator, Rounding rounding) internal pure returns (uint256) {
                              uint256 result = mulDiv(x, y, denominator);
                              if (rounding == Rounding.Up && mulmod(x, y, denominator) > 0) {
                                  result += 1;
                              }
                              return result;
                          }
                          /**
                           * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded down.
                           *
                           * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
                           */
                          function sqrt(uint256 a) internal pure returns (uint256) {
                              if (a == 0) {
                                  return 0;
                              }
                              // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
                              //
                              // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
                              // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
                              //
                              // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
                              // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
                              // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
                              //
                              // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
                              uint256 result = 1 << (log2(a) >> 1);
                              // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
                              // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
                              // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
                              // into the expected uint128 result.
                              unchecked {
                                  result = (result + a / result) >> 1;
                                  result = (result + a / result) >> 1;
                                  result = (result + a / result) >> 1;
                                  result = (result + a / result) >> 1;
                                  result = (result + a / result) >> 1;
                                  result = (result + a / result) >> 1;
                                  result = (result + a / result) >> 1;
                                  return min(result, a / result);
                              }
                          }
                          /**
                           * @notice Calculates sqrt(a), following the selected rounding direction.
                           */
                          function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
                              unchecked {
                                  uint256 result = sqrt(a);
                                  return result + (rounding == Rounding.Up && result * result < a ? 1 : 0);
                              }
                          }
                          /**
                           * @dev Return the log in base 2, rounded down, of a positive value.
                           * Returns 0 if given 0.
                           */
                          function log2(uint256 value) internal pure returns (uint256) {
                              uint256 result = 0;
                              unchecked {
                                  if (value >> 128 > 0) {
                                      value >>= 128;
                                      result += 128;
                                  }
                                  if (value >> 64 > 0) {
                                      value >>= 64;
                                      result += 64;
                                  }
                                  if (value >> 32 > 0) {
                                      value >>= 32;
                                      result += 32;
                                  }
                                  if (value >> 16 > 0) {
                                      value >>= 16;
                                      result += 16;
                                  }
                                  if (value >> 8 > 0) {
                                      value >>= 8;
                                      result += 8;
                                  }
                                  if (value >> 4 > 0) {
                                      value >>= 4;
                                      result += 4;
                                  }
                                  if (value >> 2 > 0) {
                                      value >>= 2;
                                      result += 2;
                                  }
                                  if (value >> 1 > 0) {
                                      result += 1;
                                  }
                              }
                              return result;
                          }
                          /**
                           * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
                           * Returns 0 if given 0.
                           */
                          function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
                              unchecked {
                                  uint256 result = log2(value);
                                  return result + (rounding == Rounding.Up && 1 << result < value ? 1 : 0);
                              }
                          }
                          /**
                           * @dev Return the log in base 10, rounded down, of a positive value.
                           * Returns 0 if given 0.
                           */
                          function log10(uint256 value) internal pure returns (uint256) {
                              uint256 result = 0;
                              unchecked {
                                  if (value >= 10 ** 64) {
                                      value /= 10 ** 64;
                                      result += 64;
                                  }
                                  if (value >= 10 ** 32) {
                                      value /= 10 ** 32;
                                      result += 32;
                                  }
                                  if (value >= 10 ** 16) {
                                      value /= 10 ** 16;
                                      result += 16;
                                  }
                                  if (value >= 10 ** 8) {
                                      value /= 10 ** 8;
                                      result += 8;
                                  }
                                  if (value >= 10 ** 4) {
                                      value /= 10 ** 4;
                                      result += 4;
                                  }
                                  if (value >= 10 ** 2) {
                                      value /= 10 ** 2;
                                      result += 2;
                                  }
                                  if (value >= 10 ** 1) {
                                      result += 1;
                                  }
                              }
                              return result;
                          }
                          /**
                           * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
                           * Returns 0 if given 0.
                           */
                          function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
                              unchecked {
                                  uint256 result = log10(value);
                                  return result + (rounding == Rounding.Up && 10 ** result < value ? 1 : 0);
                              }
                          }
                          /**
                           * @dev Return the log in base 256, rounded down, of a positive value.
                           * Returns 0 if given 0.
                           *
                           * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
                           */
                          function log256(uint256 value) internal pure returns (uint256) {
                              uint256 result = 0;
                              unchecked {
                                  if (value >> 128 > 0) {
                                      value >>= 128;
                                      result += 16;
                                  }
                                  if (value >> 64 > 0) {
                                      value >>= 64;
                                      result += 8;
                                  }
                                  if (value >> 32 > 0) {
                                      value >>= 32;
                                      result += 4;
                                  }
                                  if (value >> 16 > 0) {
                                      value >>= 16;
                                      result += 2;
                                  }
                                  if (value >> 8 > 0) {
                                      result += 1;
                                  }
                              }
                              return result;
                          }
                          /**
                           * @dev Return the log in base 256, following the selected rounding direction, of a positive value.
                           * Returns 0 if given 0.
                           */
                          function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
                              unchecked {
                                  uint256 result = log256(value);
                                  return result + (rounding == Rounding.Up && 1 << (result << 3) < value ? 1 : 0);
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.8.0) (utils/math/SignedMath.sol)
                      pragma solidity ^0.8.0;
                      /**
                       * @dev Standard signed math utilities missing in the Solidity language.
                       */
                      library SignedMath {
                          /**
                           * @dev Returns the largest of two signed numbers.
                           */
                          function max(int256 a, int256 b) internal pure returns (int256) {
                              return a > b ? a : b;
                          }
                          /**
                           * @dev Returns the smallest of two signed numbers.
                           */
                          function min(int256 a, int256 b) internal pure returns (int256) {
                              return a < b ? a : b;
                          }
                          /**
                           * @dev Returns the average of two signed numbers without overflow.
                           * The result is rounded towards zero.
                           */
                          function average(int256 a, int256 b) internal pure returns (int256) {
                              // Formula from the book "Hacker's Delight"
                              int256 x = (a & b) + ((a ^ b) >> 1);
                              return x + (int256(uint256(x) >> 255) & (a ^ b));
                          }
                          /**
                           * @dev Returns the absolute unsigned value of a signed value.
                           */
                          function abs(int256 n) internal pure returns (uint256) {
                              unchecked {
                                  // must be unchecked in order to support `n = type(int256).min`
                                  return uint256(n >= 0 ? n : -n);
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      // OpenZeppelin Contracts (last updated v4.9.0) (utils/StorageSlot.sol)
                      // This file was procedurally generated from scripts/generate/templates/StorageSlot.js.
                      pragma solidity ^0.8.0;
                      /**
                       * @dev Library for reading and writing primitive types to specific storage slots.
                       *
                       * Storage slots are often used to avoid storage conflict when dealing with upgradeable contracts.
                       * This library helps with reading and writing to such slots without the need for inline assembly.
                       *
                       * The functions in this library return Slot structs that contain a `value` member that can be used to read or write.
                       *
                       * Example usage to set ERC1967 implementation slot:
                       * ```solidity
                       * contract ERC1967 {
                       *     bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
                       *
                       *     function _getImplementation() internal view returns (address) {
                       *         return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
                       *     }
                       *
                       *     function _setImplementation(address newImplementation) internal {
                       *         require(Address.isContract(newImplementation), "ERC1967: new implementation is not a contract");
                       *         StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
                       *     }
                       * }
                       * ```
                       *
                       * _Available since v4.1 for `address`, `bool`, `bytes32`, `uint256`._
                       * _Available since v4.9 for `string`, `bytes`._
                       */
                      library StorageSlot {
                          struct AddressSlot {
                              address value;
                          }
                          struct BooleanSlot {
                              bool value;
                          }
                          struct Bytes32Slot {
                              bytes32 value;
                          }
                          struct Uint256Slot {
                              uint256 value;
                          }
                          struct StringSlot {
                              string value;
                          }
                          struct BytesSlot {
                              bytes value;
                          }
                          /**
                           * @dev Returns an `AddressSlot` with member `value` located at `slot`.
                           */
                          function getAddressSlot(bytes32 slot) internal pure returns (AddressSlot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := slot
                              }
                          }
                          /**
                           * @dev Returns an `BooleanSlot` with member `value` located at `slot`.
                           */
                          function getBooleanSlot(bytes32 slot) internal pure returns (BooleanSlot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := slot
                              }
                          }
                          /**
                           * @dev Returns an `Bytes32Slot` with member `value` located at `slot`.
                           */
                          function getBytes32Slot(bytes32 slot) internal pure returns (Bytes32Slot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := slot
                              }
                          }
                          /**
                           * @dev Returns an `Uint256Slot` with member `value` located at `slot`.
                           */
                          function getUint256Slot(bytes32 slot) internal pure returns (Uint256Slot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := slot
                              }
                          }
                          /**
                           * @dev Returns an `StringSlot` with member `value` located at `slot`.
                           */
                          function getStringSlot(bytes32 slot) internal pure returns (StringSlot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := slot
                              }
                          }
                          /**
                           * @dev Returns an `StringSlot` representation of the string storage pointer `store`.
                           */
                          function getStringSlot(string storage store) internal pure returns (StringSlot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := store.slot
                              }
                          }
                          /**
                           * @dev Returns an `BytesSlot` with member `value` located at `slot`.
                           */
                          function getBytesSlot(bytes32 slot) internal pure returns (BytesSlot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := slot
                              }
                          }
                          /**
                           * @dev Returns an `BytesSlot` representation of the bytes storage pointer `store`.
                           */
                          function getBytesSlot(bytes storage store) internal pure returns (BytesSlot storage r) {
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r.slot := store.slot
                              }
                          }
                      }
                      

                      File 5 of 7: ZeroEx
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
                      import "./migrations/LibBootstrap.sol";
                      import "./features/Bootstrap.sol";
                      import "./storage/LibProxyStorage.sol";
                      import "./errors/LibProxyRichErrors.sol";
                      /// @dev An extensible proxy contract that serves as a universal entry point for
                      ///      interacting with the 0x protocol.
                      contract ZeroEx {
                          // solhint-disable separate-by-one-line-in-contract,indent,var-name-mixedcase
                          using LibBytesV06 for bytes;
                          /// @dev Construct this contract and register the `Bootstrap` feature.
                          ///      After constructing this contract, `bootstrap()` should be called
                          ///      to seed the initial feature set.
                          constructor() public {
                              // Temporarily create and register the bootstrap feature.
                              // It will deregister itself after `bootstrap()` has been called.
                              Bootstrap bootstrap = new Bootstrap(msg.sender);
                              LibProxyStorage.getStorage().impls[bootstrap.bootstrap.selector] =
                                  address(bootstrap);
                          }
                          // solhint-disable state-visibility
                          /// @dev Forwards calls to the appropriate implementation contract.
                          fallback() external payable {
                              bytes4 selector = msg.data.readBytes4(0);
                              address impl = getFunctionImplementation(selector);
                              if (impl == address(0)) {
                                  _revertWithData(LibProxyRichErrors.NotImplementedError(selector));
                              }
                              (bool success, bytes memory resultData) = impl.delegatecall(msg.data);
                              if (!success) {
                                  _revertWithData(resultData);
                              }
                              _returnWithData(resultData);
                          }
                          /// @dev Fallback for just receiving ether.
                          receive() external payable {}
                          // solhint-enable state-visibility
                          /// @dev Get the implementation contract of a registered function.
                          /// @param selector The function selector.
                          /// @return impl The implementation contract address.
                          function getFunctionImplementation(bytes4 selector)
                              public
                              view
                              returns (address impl)
                          {
                              return LibProxyStorage.getStorage().impls[selector];
                          }
                          /// @dev Revert with arbitrary bytes.
                          /// @param data Revert data.
                          function _revertWithData(bytes memory data) private pure {
                              assembly { revert(add(data, 32), mload(data)) }
                          }
                          /// @dev Return with arbitrary bytes.
                          /// @param data Return data.
                          function _returnWithData(bytes memory data) private pure {
                              assembly { return(add(data, 32), mload(data)) }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./errors/LibBytesRichErrorsV06.sol";
                      import "./errors/LibRichErrorsV06.sol";
                      library LibBytesV06 {
                          using LibBytesV06 for bytes;
                          /// @dev Gets the memory address for a byte array.
                          /// @param input Byte array to lookup.
                          /// @return memoryAddress Memory address of byte array. This
                          ///         points to the header of the byte array which contains
                          ///         the length.
                          function rawAddress(bytes memory input)
                              internal
                              pure
                              returns (uint256 memoryAddress)
                          {
                              assembly {
                                  memoryAddress := input
                              }
                              return memoryAddress;
                          }
                          /// @dev Gets the memory address for the contents of a byte array.
                          /// @param input Byte array to lookup.
                          /// @return memoryAddress Memory address of the contents of the byte array.
                          function contentAddress(bytes memory input)
                              internal
                              pure
                              returns (uint256 memoryAddress)
                          {
                              assembly {
                                  memoryAddress := add(input, 32)
                              }
                              return memoryAddress;
                          }
                          /// @dev Copies `length` bytes from memory location `source` to `dest`.
                          /// @param dest memory address to copy bytes to.
                          /// @param source memory address to copy bytes from.
                          /// @param length number of bytes to copy.
                          function memCopy(
                              uint256 dest,
                              uint256 source,
                              uint256 length
                          )
                              internal
                              pure
                          {
                              if (length < 32) {
                                  // Handle a partial word by reading destination and masking
                                  // off the bits we are interested in.
                                  // This correctly handles overlap, zero lengths and source == dest
                                  assembly {
                                      let mask := sub(exp(256, sub(32, length)), 1)
                                      let s := and(mload(source), not(mask))
                                      let d := and(mload(dest), mask)
                                      mstore(dest, or(s, d))
                                  }
                              } else {
                                  // Skip the O(length) loop when source == dest.
                                  if (source == dest) {
                                      return;
                                  }
                                  // For large copies we copy whole words at a time. The final
                                  // word is aligned to the end of the range (instead of after the
                                  // previous) to handle partial words. So a copy will look like this:
                                  //
                                  //  ####
                                  //      ####
                                  //          ####
                                  //            ####
                                  //
                                  // We handle overlap in the source and destination range by
                                  // changing the copying direction. This prevents us from
                                  // overwriting parts of source that we still need to copy.
                                  //
                                  // This correctly handles source == dest
                                  //
                                  if (source > dest) {
                                      assembly {
                                          // We subtract 32 from `sEnd` and `dEnd` because it
                                          // is easier to compare with in the loop, and these
                                          // are also the addresses we need for copying the
                                          // last bytes.
                                          length := sub(length, 32)
                                          let sEnd := add(source, length)
                                          let dEnd := add(dest, length)
                                          // Remember the last 32 bytes of source
                                          // This needs to be done here and not after the loop
                                          // because we may have overwritten the last bytes in
                                          // source already due to overlap.
                                          let last := mload(sEnd)
                                          // Copy whole words front to back
                                          // Note: the first check is always true,
                                          // this could have been a do-while loop.
                                          // solhint-disable-next-line no-empty-blocks
                                          for {} lt(source, sEnd) {} {
                                              mstore(dest, mload(source))
                                              source := add(source, 32)
                                              dest := add(dest, 32)
                                          }
                                          // Write the last 32 bytes
                                          mstore(dEnd, last)
                                      }
                                  } else {
                                      assembly {
                                          // We subtract 32 from `sEnd` and `dEnd` because those
                                          // are the starting points when copying a word at the end.
                                          length := sub(length, 32)
                                          let sEnd := add(source, length)
                                          let dEnd := add(dest, length)
                                          // Remember the first 32 bytes of source
                                          // This needs to be done here and not after the loop
                                          // because we may have overwritten the first bytes in
                                          // source already due to overlap.
                                          let first := mload(source)
                                          // Copy whole words back to front
                                          // We use a signed comparisson here to allow dEnd to become
                                          // negative (happens when source and dest < 32). Valid
                                          // addresses in local memory will never be larger than
                                          // 2**255, so they can be safely re-interpreted as signed.
                                          // Note: the first check is always true,
                                          // this could have been a do-while loop.
                                          // solhint-disable-next-line no-empty-blocks
                                          for {} slt(dest, dEnd) {} {
                                              mstore(dEnd, mload(sEnd))
                                              sEnd := sub(sEnd, 32)
                                              dEnd := sub(dEnd, 32)
                                          }
                                          // Write the first 32 bytes
                                          mstore(dest, first)
                                      }
                                  }
                              }
                          }
                          /// @dev Returns a slices from a byte array.
                          /// @param b The byte array to take a slice from.
                          /// @param from The starting index for the slice (inclusive).
                          /// @param to The final index for the slice (exclusive).
                          /// @return result The slice containing bytes at indices [from, to)
                          function slice(
                              bytes memory b,
                              uint256 from,
                              uint256 to
                          )
                              internal
                              pure
                              returns (bytes memory result)
                          {
                              // Ensure that the from and to positions are valid positions for a slice within
                              // the byte array that is being used.
                              if (from > to) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.FromLessThanOrEqualsToRequired,
                                      from,
                                      to
                                  ));
                              }
                              if (to > b.length) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.ToLessThanOrEqualsLengthRequired,
                                      to,
                                      b.length
                                  ));
                              }
                              // Create a new bytes structure and copy contents
                              result = new bytes(to - from);
                              memCopy(
                                  result.contentAddress(),
                                  b.contentAddress() + from,
                                  result.length
                              );
                              return result;
                          }
                          /// @dev Returns a slice from a byte array without preserving the input.
                          ///      When `from == 0`, the original array will match the slice.
                          ///      In other cases its state will be corrupted.
                          /// @param b The byte array to take a slice from. Will be destroyed in the process.
                          /// @param from The starting index for the slice (inclusive).
                          /// @param to The final index for the slice (exclusive).
                          /// @return result The slice containing bytes at indices [from, to)
                          function sliceDestructive(
                              bytes memory b,
                              uint256 from,
                              uint256 to
                          )
                              internal
                              pure
                              returns (bytes memory result)
                          {
                              // Ensure that the from and to positions are valid positions for a slice within
                              // the byte array that is being used.
                              if (from > to) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.FromLessThanOrEqualsToRequired,
                                      from,
                                      to
                                  ));
                              }
                              if (to > b.length) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.ToLessThanOrEqualsLengthRequired,
                                      to,
                                      b.length
                                  ));
                              }
                              // Create a new bytes structure around [from, to) in-place.
                              assembly {
                                  result := add(b, from)
                                  mstore(result, sub(to, from))
                              }
                              return result;
                          }
                          /// @dev Pops the last byte off of a byte array by modifying its length.
                          /// @param b Byte array that will be modified.
                          /// @return result The byte that was popped off.
                          function popLastByte(bytes memory b)
                              internal
                              pure
                              returns (bytes1 result)
                          {
                              if (b.length == 0) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanZeroRequired,
                                      b.length,
                                      0
                                  ));
                              }
                              // Store last byte.
                              result = b[b.length - 1];
                              assembly {
                                  // Decrement length of byte array.
                                  let newLen := sub(mload(b), 1)
                                  mstore(b, newLen)
                              }
                              return result;
                          }
                          /// @dev Tests equality of two byte arrays.
                          /// @param lhs First byte array to compare.
                          /// @param rhs Second byte array to compare.
                          /// @return equal True if arrays are the same. False otherwise.
                          function equals(
                              bytes memory lhs,
                              bytes memory rhs
                          )
                              internal
                              pure
                              returns (bool equal)
                          {
                              // Keccak gas cost is 30 + numWords * 6. This is a cheap way to compare.
                              // We early exit on unequal lengths, but keccak would also correctly
                              // handle this.
                              return lhs.length == rhs.length && keccak256(lhs) == keccak256(rhs);
                          }
                          /// @dev Reads an address from a position in a byte array.
                          /// @param b Byte array containing an address.
                          /// @param index Index in byte array of address.
                          /// @return result address from byte array.
                          function readAddress(
                              bytes memory b,
                              uint256 index
                          )
                              internal
                              pure
                              returns (address result)
                          {
                              if (b.length < index + 20) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsTwentyRequired,
                                      b.length,
                                      index + 20 // 20 is length of address
                                  ));
                              }
                              // Add offset to index:
                              // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
                              // 2. Account for size difference between address length and 32-byte storage word (subtract 12 from index)
                              index += 20;
                              // Read address from array memory
                              assembly {
                                  // 1. Add index to address of bytes array
                                  // 2. Load 32-byte word from memory
                                  // 3. Apply 20-byte mask to obtain address
                                  result := and(mload(add(b, index)), 0xffffffffffffffffffffffffffffffffffffffff)
                              }
                              return result;
                          }
                          /// @dev Writes an address into a specific position in a byte array.
                          /// @param b Byte array to insert address into.
                          /// @param index Index in byte array of address.
                          /// @param input Address to put into byte array.
                          function writeAddress(
                              bytes memory b,
                              uint256 index,
                              address input
                          )
                              internal
                              pure
                          {
                              if (b.length < index + 20) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsTwentyRequired,
                                      b.length,
                                      index + 20 // 20 is length of address
                                  ));
                              }
                              // Add offset to index:
                              // 1. Arrays are prefixed by 32-byte length parameter (add 32 to index)
                              // 2. Account for size difference between address length and 32-byte storage word (subtract 12 from index)
                              index += 20;
                              // Store address into array memory
                              assembly {
                                  // The address occupies 20 bytes and mstore stores 32 bytes.
                                  // First fetch the 32-byte word where we'll be storing the address, then
                                  // apply a mask so we have only the bytes in the word that the address will not occupy.
                                  // Then combine these bytes with the address and store the 32 bytes back to memory with mstore.
                                  // 1. Add index to address of bytes array
                                  // 2. Load 32-byte word from memory
                                  // 3. Apply 12-byte mask to obtain extra bytes occupying word of memory where we'll store the address
                                  let neighbors := and(
                                      mload(add(b, index)),
                                      0xffffffffffffffffffffffff0000000000000000000000000000000000000000
                                  )
                                  // Make sure input address is clean.
                                  // (Solidity does not guarantee this)
                                  input := and(input, 0xffffffffffffffffffffffffffffffffffffffff)
                                  // Store the neighbors and address into memory
                                  mstore(add(b, index), xor(input, neighbors))
                              }
                          }
                          /// @dev Reads a bytes32 value from a position in a byte array.
                          /// @param b Byte array containing a bytes32 value.
                          /// @param index Index in byte array of bytes32 value.
                          /// @return result bytes32 value from byte array.
                          function readBytes32(
                              bytes memory b,
                              uint256 index
                          )
                              internal
                              pure
                              returns (bytes32 result)
                          {
                              if (b.length < index + 32) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsThirtyTwoRequired,
                                      b.length,
                                      index + 32
                                  ));
                              }
                              // Arrays are prefixed by a 256 bit length parameter
                              index += 32;
                              // Read the bytes32 from array memory
                              assembly {
                                  result := mload(add(b, index))
                              }
                              return result;
                          }
                          /// @dev Writes a bytes32 into a specific position in a byte array.
                          /// @param b Byte array to insert <input> into.
                          /// @param index Index in byte array of <input>.
                          /// @param input bytes32 to put into byte array.
                          function writeBytes32(
                              bytes memory b,
                              uint256 index,
                              bytes32 input
                          )
                              internal
                              pure
                          {
                              if (b.length < index + 32) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsThirtyTwoRequired,
                                      b.length,
                                      index + 32
                                  ));
                              }
                              // Arrays are prefixed by a 256 bit length parameter
                              index += 32;
                              // Read the bytes32 from array memory
                              assembly {
                                  mstore(add(b, index), input)
                              }
                          }
                          /// @dev Reads a uint256 value from a position in a byte array.
                          /// @param b Byte array containing a uint256 value.
                          /// @param index Index in byte array of uint256 value.
                          /// @return result uint256 value from byte array.
                          function readUint256(
                              bytes memory b,
                              uint256 index
                          )
                              internal
                              pure
                              returns (uint256 result)
                          {
                              result = uint256(readBytes32(b, index));
                              return result;
                          }
                          /// @dev Writes a uint256 into a specific position in a byte array.
                          /// @param b Byte array to insert <input> into.
                          /// @param index Index in byte array of <input>.
                          /// @param input uint256 to put into byte array.
                          function writeUint256(
                              bytes memory b,
                              uint256 index,
                              uint256 input
                          )
                              internal
                              pure
                          {
                              writeBytes32(b, index, bytes32(input));
                          }
                          /// @dev Reads an unpadded bytes4 value from a position in a byte array.
                          /// @param b Byte array containing a bytes4 value.
                          /// @param index Index in byte array of bytes4 value.
                          /// @return result bytes4 value from byte array.
                          function readBytes4(
                              bytes memory b,
                              uint256 index
                          )
                              internal
                              pure
                              returns (bytes4 result)
                          {
                              if (b.length < index + 4) {
                                  LibRichErrorsV06.rrevert(LibBytesRichErrorsV06.InvalidByteOperationError(
                                      LibBytesRichErrorsV06.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsFourRequired,
                                      b.length,
                                      index + 4
                                  ));
                              }
                              // Arrays are prefixed by a 32 byte length field
                              index += 32;
                              // Read the bytes4 from array memory
                              assembly {
                                  result := mload(add(b, index))
                                  // Solidity does not require us to clean the trailing bytes.
                                  // We do it anyway
                                  result := and(result, 0xFFFFFFFF00000000000000000000000000000000000000000000000000000000)
                              }
                              return result;
                          }
                          /// @dev Writes a new length to a byte array.
                          ///      Decreasing length will lead to removing the corresponding lower order bytes from the byte array.
                          ///      Increasing length may lead to appending adjacent in-memory bytes to the end of the byte array.
                          /// @param b Bytes array to write new length to.
                          /// @param length New length of byte array.
                          function writeLength(bytes memory b, uint256 length)
                              internal
                              pure
                          {
                              assembly {
                                  mstore(b, length)
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibBytesRichErrorsV06 {
                          enum InvalidByteOperationErrorCodes {
                              FromLessThanOrEqualsToRequired,
                              ToLessThanOrEqualsLengthRequired,
                              LengthGreaterThanZeroRequired,
                              LengthGreaterThanOrEqualsFourRequired,
                              LengthGreaterThanOrEqualsTwentyRequired,
                              LengthGreaterThanOrEqualsThirtyTwoRequired,
                              LengthGreaterThanOrEqualsNestedBytesLengthRequired,
                              DestinationLengthGreaterThanOrEqualSourceLengthRequired
                          }
                          // bytes4(keccak256("InvalidByteOperationError(uint8,uint256,uint256)"))
                          bytes4 internal constant INVALID_BYTE_OPERATION_ERROR_SELECTOR =
                              0x28006595;
                          // solhint-disable func-name-mixedcase
                          function InvalidByteOperationError(
                              InvalidByteOperationErrorCodes errorCode,
                              uint256 offset,
                              uint256 required
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  INVALID_BYTE_OPERATION_ERROR_SELECTOR,
                                  errorCode,
                                  offset,
                                  required
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibRichErrorsV06 {
                          // bytes4(keccak256("Error(string)"))
                          bytes4 internal constant STANDARD_ERROR_SELECTOR = 0x08c379a0;
                          // solhint-disable func-name-mixedcase
                          /// @dev ABI encode a standard, string revert error payload.
                          ///      This is the same payload that would be included by a `revert(string)`
                          ///      solidity statement. It has the function signature `Error(string)`.
                          /// @param message The error string.
                          /// @return The ABI encoded error.
                          function StandardError(string memory message)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  STANDARD_ERROR_SELECTOR,
                                  bytes(message)
                              );
                          }
                          // solhint-enable func-name-mixedcase
                          /// @dev Reverts an encoded rich revert reason `errorData`.
                          /// @param errorData ABI encoded error data.
                          function rrevert(bytes memory errorData)
                              internal
                              pure
                          {
                              assembly {
                                  revert(add(errorData, 0x20), mload(errorData))
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../errors/LibProxyRichErrors.sol";
                      library LibBootstrap {
                          /// @dev Magic bytes returned by the bootstrapper to indicate success.
                          ///      This is `keccack('BOOTSTRAP_SUCCESS')`.
                          bytes4 internal constant BOOTSTRAP_SUCCESS = 0xd150751b;
                          using LibRichErrorsV06 for bytes;
                          /// @dev Perform a delegatecall and ensure it returns the magic bytes.
                          /// @param target The call target.
                          /// @param data The call data.
                          function delegatecallBootstrapFunction(
                              address target,
                              bytes memory data
                          )
                              internal
                          {
                              (bool success, bytes memory resultData) = target.delegatecall(data);
                              if (!success ||
                                  resultData.length != 32 ||
                                  abi.decode(resultData, (bytes4)) != BOOTSTRAP_SUCCESS)
                              {
                                  LibProxyRichErrors.BootstrapCallFailedError(target, resultData).rrevert();
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibProxyRichErrors {
                          // solhint-disable func-name-mixedcase
                          function NotImplementedError(bytes4 selector)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("NotImplementedError(bytes4)")),
                                  selector
                              );
                          }
                          function InvalidBootstrapCallerError(address actual, address expected)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InvalidBootstrapCallerError(address,address)")),
                                  actual,
                                  expected
                              );
                          }
                          function InvalidDieCallerError(address actual, address expected)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InvalidDieCallerError(address,address)")),
                                  actual,
                                  expected
                              );
                          }
                          function BootstrapCallFailedError(address target, bytes memory resultData)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("BootstrapCallFailedError(address,bytes)")),
                                  target,
                                  resultData
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../migrations/LibBootstrap.sol";
                      import "../storage/LibProxyStorage.sol";
                      import "./IBootstrap.sol";
                      /// @dev Detachable `bootstrap()` feature.
                      contract Bootstrap is
                          IBootstrap
                      {
                          // solhint-disable state-visibility,indent
                          /// @dev The ZeroEx contract.
                          ///      This has to be immutable to persist across delegatecalls.
                          address immutable private _deployer;
                          /// @dev The implementation address of this contract.
                          ///      This has to be immutable to persist across delegatecalls.
                          address immutable private _implementation;
                          /// @dev The deployer.
                          ///      This has to be immutable to persist across delegatecalls.
                          address immutable private _bootstrapCaller;
                          // solhint-enable state-visibility,indent
                          using LibRichErrorsV06 for bytes;
                          /// @dev Construct this contract and set the bootstrap migration contract.
                          ///      After constructing this contract, `bootstrap()` should be called
                          ///      to seed the initial feature set.
                          /// @param bootstrapCaller The allowed caller of `bootstrap()`.
                          constructor(address bootstrapCaller) public {
                              _deployer = msg.sender;
                              _implementation = address(this);
                              _bootstrapCaller = bootstrapCaller;
                          }
                          /// @dev Bootstrap the initial feature set of this contract by delegatecalling
                          ///      into `target`. Before exiting the `bootstrap()` function will
                          ///      deregister itself from the proxy to prevent being called again.
                          /// @param target The bootstrapper contract address.
                          /// @param callData The call data to execute on `target`.
                          function bootstrap(address target, bytes calldata callData) external override {
                              // Only the bootstrap caller can call this function.
                              if (msg.sender != _bootstrapCaller) {
                                  LibProxyRichErrors.InvalidBootstrapCallerError(
                                      msg.sender,
                                      _bootstrapCaller
                                  ).rrevert();
                              }
                              // Deregister.
                              LibProxyStorage.getStorage().impls[this.bootstrap.selector] = address(0);
                              // Self-destruct.
                              Bootstrap(_implementation).die();
                              // Call the bootstrapper.
                              LibBootstrap.delegatecallBootstrapFunction(target, callData);
                          }
                          /// @dev Self-destructs this contract.
                          ///      Can only be called by the deployer.
                          function die() external {
                              if (msg.sender != _deployer) {
                                  LibProxyRichErrors.InvalidDieCallerError(msg.sender, _deployer).rrevert();
                              }
                              selfdestruct(msg.sender);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./LibStorage.sol";
                      /// @dev Storage helpers for the proxy contract.
                      library LibProxyStorage {
                          /// @dev Storage bucket for proxy contract.
                          struct Storage {
                              // Mapping of function selector -> function implementation
                              mapping(bytes4 => address) impls;
                              // The owner of the proxy contract.
                              address owner;
                          }
                          /// @dev Get the storage bucket for this contract.
                          function getStorage() internal pure returns (Storage storage stor) {
                              uint256 storageSlot = LibStorage.getStorageSlot(
                                  LibStorage.StorageId.Proxy
                              );
                              // Dip into assembly to change the slot pointed to by the local
                              // variable `stor`.
                              // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                              assembly { stor_slot := storageSlot }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Common storage helpers
                      library LibStorage {
                          /// @dev What to bit-shift a storage ID by to get its slot.
                          ///      This gives us a maximum of 2**128 inline fields in each bucket.
                          uint256 private constant STORAGE_SLOT_EXP = 128;
                          /// @dev Storage IDs for feature storage buckets.
                          ///      WARNING: APPEND-ONLY.
                          enum StorageId {
                              Proxy,
                              SimpleFunctionRegistry,
                              Ownable,
                              TokenSpender,
                              TransformERC20
                          }
                          /// @dev Get the storage slot given a storage ID. We assign unique, well-spaced
                          ///     slots to storage bucket variables to ensure they do not overlap.
                          ///     See: https://solidity.readthedocs.io/en/v0.6.6/assembly.html#access-to-external-variables-functions-and-libraries
                          /// @param storageId An entry in `StorageId`
                          /// @return slot The storage slot.
                          function getStorageSlot(StorageId storageId)
                              internal
                              pure
                              returns (uint256 slot)
                          {
                              // This should never overflow with a reasonable `STORAGE_SLOT_EXP`
                              // because Solidity will do a range check on `storageId` during the cast.
                              return (uint256(storageId) + 1) << STORAGE_SLOT_EXP;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Detachable `bootstrap()` feature.
                      interface IBootstrap {
                          /// @dev Bootstrap the initial feature set of this contract by delegatecalling
                          ///      into `target`. Before exiting the `bootstrap()` function will
                          ///      deregister itself from the proxy to prevent being called again.
                          /// @param target The bootstrapper contract address.
                          /// @param callData The call data to execute on `target`.
                          function bootstrap(address target, bytes calldata callData) external;
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibCommonRichErrors {
                          // solhint-disable func-name-mixedcase
                          function OnlyCallableBySelfError(address sender)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OnlyCallableBySelfError(address)")),
                                  sender
                              );
                          }
                          function IllegalReentrancyError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("IllegalReentrancyError()"))
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibOwnableRichErrors {
                          // solhint-disable func-name-mixedcase
                          function OnlyOwnerError(
                              address sender,
                              address owner
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OnlyOwnerError(address,address)")),
                                  sender,
                                  owner
                              );
                          }
                          function TransferOwnerToZeroError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("TransferOwnerToZeroError()"))
                              );
                          }
                          function MigrateCallFailedError(address target, bytes memory resultData)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("MigrateCallFailedError(address,bytes)")),
                                  target,
                                  resultData
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibSimpleFunctionRegistryRichErrors {
                          // solhint-disable func-name-mixedcase
                          function NotInRollbackHistoryError(bytes4 selector, address targetImpl)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("NotInRollbackHistoryError(bytes4,address)")),
                                  selector,
                                  targetImpl
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibSpenderRichErrors {
                          // solhint-disable func-name-mixedcase
                          function SpenderERC20TransferFromFailedError(
                              address token,
                              address owner,
                              address to,
                              uint256 amount,
                              bytes memory errorData
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("SpenderERC20TransferFromFailedError(address,address,address,uint256,bytes)")),
                                  token,
                                  owner,
                                  to,
                                  amount,
                                  errorData
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibTransformERC20RichErrors {
                          // solhint-disable func-name-mixedcase,separate-by-one-line-in-contract
                          function InsufficientEthAttachedError(
                              uint256 ethAttached,
                              uint256 ethNeeded
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InsufficientEthAttachedError(uint256,uint256)")),
                                  ethAttached,
                                  ethNeeded
                              );
                          }
                          function IncompleteTransformERC20Error(
                              address outputToken,
                              uint256 outputTokenAmount,
                              uint256 minOutputTokenAmount
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("IncompleteTransformERC20Error(address,uint256,uint256)")),
                                  outputToken,
                                  outputTokenAmount,
                                  minOutputTokenAmount
                              );
                          }
                          function NegativeTransformERC20OutputError(
                              address outputToken,
                              uint256 outputTokenLostAmount
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("NegativeTransformERC20OutputError(address,uint256)")),
                                  outputToken,
                                  outputTokenLostAmount
                              );
                          }
                          function TransformerFailedError(
                              address transformer,
                              bytes memory transformerData,
                              bytes memory resultData
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("TransformerFailedError(address,bytes,bytes)")),
                                  transformer,
                                  transformerData,
                                  resultData
                              );
                          }
                          // Common Transformer errors ///////////////////////////////////////////////
                          function OnlyCallableByDeployerError(
                              address caller,
                              address deployer
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OnlyCallableByDeployerError(address,address)")),
                                  caller,
                                  deployer
                              );
                          }
                          function InvalidExecutionContextError(
                              address actualContext,
                              address expectedContext
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InvalidExecutionContextError(address,address)")),
                                  actualContext,
                                  expectedContext
                              );
                          }
                          enum InvalidTransformDataErrorCode {
                              INVALID_TOKENS,
                              INVALID_ARRAY_LENGTH
                          }
                          function InvalidTransformDataError(
                              InvalidTransformDataErrorCode errorCode,
                              bytes memory transformData
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InvalidTransformDataError(uint8,bytes)")),
                                  errorCode,
                                  transformData
                              );
                          }
                          // FillQuoteTransformer errors /////////////////////////////////////////////
                          function IncompleteFillSellQuoteError(
                              address sellToken,
                              uint256 soldAmount,
                              uint256 sellAmount
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("IncompleteFillSellQuoteError(address,uint256,uint256)")),
                                  sellToken,
                                  soldAmount,
                                  sellAmount
                              );
                          }
                          function IncompleteFillBuyQuoteError(
                              address buyToken,
                              uint256 boughtAmount,
                              uint256 buyAmount
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("IncompleteFillBuyQuoteError(address,uint256,uint256)")),
                                  buyToken,
                                  boughtAmount,
                                  buyAmount
                              );
                          }
                          function InsufficientTakerTokenError(
                              uint256 tokenBalance,
                              uint256 tokensNeeded
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InsufficientTakerTokenError(uint256,uint256)")),
                                  tokenBalance,
                                  tokensNeeded
                              );
                          }
                          function InsufficientProtocolFeeError(
                              uint256 ethBalance,
                              uint256 ethNeeded
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InsufficientProtocolFeeError(uint256,uint256)")),
                                  ethBalance,
                                  ethNeeded
                              );
                          }
                          function InvalidERC20AssetDataError(
                              bytes memory assetData
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InvalidERC20AssetDataError(bytes)")),
                                  assetData
                              );
                          }
                          function InvalidTakerFeeTokenError(
                              address token
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InvalidTakerFeeTokenError(address)")),
                                  token
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibWalletRichErrors {
                          // solhint-disable func-name-mixedcase
                          function WalletExecuteCallFailedError(
                              address wallet,
                              address callTarget,
                              bytes memory callData,
                              uint256 callValue,
                              bytes memory errorData
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("WalletExecuteCallFailedError(address,address,bytes,uint256,bytes)")),
                                  wallet,
                                  callTarget,
                                  callData,
                                  callValue,
                                  errorData
                              );
                          }
                          function WalletExecuteDelegateCallFailedError(
                              address wallet,
                              address callTarget,
                              bytes memory callData,
                              bytes memory errorData
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("WalletExecuteDelegateCallFailedError(address,address,bytes,bytes)")),
                                  wallet,
                                  callTarget,
                                  callData,
                                  errorData
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/AuthorizableV06.sol";
                      import "../errors/LibSpenderRichErrors.sol";
                      import "./IAllowanceTarget.sol";
                      /// @dev The allowance target for the TokenSpender feature.
                      contract AllowanceTarget is
                          IAllowanceTarget,
                          AuthorizableV06
                      {
                          // solhint-disable no-unused-vars,indent,no-empty-blocks
                          using LibRichErrorsV06 for bytes;
                          /// @dev Execute an arbitrary call. Only an authority can call this.
                          /// @param target The call target.
                          /// @param callData The call data.
                          /// @return resultData The data returned by the call.
                          function executeCall(
                              address payable target,
                              bytes calldata callData
                          )
                              external
                              override
                              onlyAuthorized
                              returns (bytes memory resultData)
                          {
                              bool success;
                              (success, resultData) = target.call(callData);
                              if (!success) {
                                  resultData.rrevert();
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./interfaces/IAuthorizableV06.sol";
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibAuthorizableRichErrorsV06.sol";
                      import "./OwnableV06.sol";
                      // solhint-disable no-empty-blocks
                      contract AuthorizableV06 is
                          OwnableV06,
                          IAuthorizableV06
                      {
                          /// @dev Only authorized addresses can invoke functions with this modifier.
                          modifier onlyAuthorized {
                              _assertSenderIsAuthorized();
                              _;
                          }
                          // @dev Whether an address is authorized to call privileged functions.
                          // @param 0 Address to query.
                          // @return 0 Whether the address is authorized.
                          mapping (address => bool) public override authorized;
                          // @dev Whether an address is authorized to call privileged functions.
                          // @param 0 Index of authorized address.
                          // @return 0 Authorized address.
                          address[] public override authorities;
                          /// @dev Initializes the `owner` address.
                          constructor()
                              public
                              OwnableV06()
                          {}
                          /// @dev Authorizes an address.
                          /// @param target Address to authorize.
                          function addAuthorizedAddress(address target)
                              external
                              override
                              onlyOwner
                          {
                              _addAuthorizedAddress(target);
                          }
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          function removeAuthorizedAddress(address target)
                              external
                              override
                              onlyOwner
                          {
                              if (!authorized[target]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetNotAuthorizedError(target));
                              }
                              for (uint256 i = 0; i < authorities.length; i++) {
                                  if (authorities[i] == target) {
                                      _removeAuthorizedAddressAtIndex(target, i);
                                      break;
                                  }
                              }
                          }
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          /// @param index Index of target in authorities array.
                          function removeAuthorizedAddressAtIndex(
                              address target,
                              uint256 index
                          )
                              external
                              override
                              onlyOwner
                          {
                              _removeAuthorizedAddressAtIndex(target, index);
                          }
                          /// @dev Gets all authorized addresses.
                          /// @return Array of authorized addresses.
                          function getAuthorizedAddresses()
                              external
                              override
                              view
                              returns (address[] memory)
                          {
                              return authorities;
                          }
                          /// @dev Reverts if msg.sender is not authorized.
                          function _assertSenderIsAuthorized()
                              internal
                              view
                          {
                              if (!authorized[msg.sender]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.SenderNotAuthorizedError(msg.sender));
                              }
                          }
                          /// @dev Authorizes an address.
                          /// @param target Address to authorize.
                          function _addAuthorizedAddress(address target)
                              internal
                          {
                              // Ensure that the target is not the zero address.
                              if (target == address(0)) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.ZeroCantBeAuthorizedError());
                              }
                              // Ensure that the target is not already authorized.
                              if (authorized[target]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetAlreadyAuthorizedError(target));
                              }
                              authorized[target] = true;
                              authorities.push(target);
                              emit AuthorizedAddressAdded(target, msg.sender);
                          }
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          /// @param index Index of target in authorities array.
                          function _removeAuthorizedAddressAtIndex(
                              address target,
                              uint256 index
                          )
                              internal
                          {
                              if (!authorized[target]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetNotAuthorizedError(target));
                              }
                              if (index >= authorities.length) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.IndexOutOfBoundsError(
                                      index,
                                      authorities.length
                                  ));
                              }
                              if (authorities[index] != target) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.AuthorizedAddressMismatchError(
                                      authorities[index],
                                      target
                                  ));
                              }
                              delete authorized[target];
                              authorities[index] = authorities[authorities.length - 1];
                              authorities.pop();
                              emit AuthorizedAddressRemoved(target, msg.sender);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./IOwnableV06.sol";
                      interface IAuthorizableV06 is
                          IOwnableV06
                      {
                          // Event logged when a new address is authorized.
                          event AuthorizedAddressAdded(
                              address indexed target,
                              address indexed caller
                          );
                          // Event logged when a currently authorized address is unauthorized.
                          event AuthorizedAddressRemoved(
                              address indexed target,
                              address indexed caller
                          );
                          /// @dev Authorizes an address.
                          /// @param target Address to authorize.
                          function addAuthorizedAddress(address target)
                              external;
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          function removeAuthorizedAddress(address target)
                              external;
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          /// @param index Index of target in authorities array.
                          function removeAuthorizedAddressAtIndex(
                              address target,
                              uint256 index
                          )
                              external;
                          /// @dev Gets all authorized addresses.
                          /// @return authorizedAddresses Array of authorized addresses.
                          function getAuthorizedAddresses()
                              external
                              view
                              returns (address[] memory authorizedAddresses);
                          /// @dev Whether an adderss is authorized to call privileged functions.
                          /// @param addr Address to query.
                          /// @return isAuthorized Whether the address is authorized.
                          function authorized(address addr) external view returns (bool isAuthorized);
                          /// @dev All addresseses authorized to call privileged functions.
                          /// @param idx Index of authorized address.
                          /// @return addr Authorized address.
                          function authorities(uint256 idx) external view returns (address addr);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      interface IOwnableV06 {
                          /// @dev Emitted by Ownable when ownership is transferred.
                          /// @param previousOwner The previous owner of the contract.
                          /// @param newOwner The new owner of the contract.
                          event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
                          /// @dev Transfers ownership of the contract to a new address.
                          /// @param newOwner The address that will become the owner.
                          function transferOwnership(address newOwner) external;
                          /// @dev The owner of this contract.
                          /// @return ownerAddress The owner address.
                          function owner() external view returns (address ownerAddress);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibAuthorizableRichErrorsV06 {
                          // bytes4(keccak256("AuthorizedAddressMismatchError(address,address)"))
                          bytes4 internal constant AUTHORIZED_ADDRESS_MISMATCH_ERROR_SELECTOR =
                              0x140a84db;
                          // bytes4(keccak256("IndexOutOfBoundsError(uint256,uint256)"))
                          bytes4 internal constant INDEX_OUT_OF_BOUNDS_ERROR_SELECTOR =
                              0xe9f83771;
                          // bytes4(keccak256("SenderNotAuthorizedError(address)"))
                          bytes4 internal constant SENDER_NOT_AUTHORIZED_ERROR_SELECTOR =
                              0xb65a25b9;
                          // bytes4(keccak256("TargetAlreadyAuthorizedError(address)"))
                          bytes4 internal constant TARGET_ALREADY_AUTHORIZED_ERROR_SELECTOR =
                              0xde16f1a0;
                          // bytes4(keccak256("TargetNotAuthorizedError(address)"))
                          bytes4 internal constant TARGET_NOT_AUTHORIZED_ERROR_SELECTOR =
                              0xeb5108a2;
                          // bytes4(keccak256("ZeroCantBeAuthorizedError()"))
                          bytes internal constant ZERO_CANT_BE_AUTHORIZED_ERROR_BYTES =
                              hex"57654fe4";
                          // solhint-disable func-name-mixedcase
                          function AuthorizedAddressMismatchError(
                              address authorized,
                              address target
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  AUTHORIZED_ADDRESS_MISMATCH_ERROR_SELECTOR,
                                  authorized,
                                  target
                              );
                          }
                          function IndexOutOfBoundsError(
                              uint256 index,
                              uint256 length
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  INDEX_OUT_OF_BOUNDS_ERROR_SELECTOR,
                                  index,
                                  length
                              );
                          }
                          function SenderNotAuthorizedError(address sender)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  SENDER_NOT_AUTHORIZED_ERROR_SELECTOR,
                                  sender
                              );
                          }
                          function TargetAlreadyAuthorizedError(address target)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  TARGET_ALREADY_AUTHORIZED_ERROR_SELECTOR,
                                  target
                              );
                          }
                          function TargetNotAuthorizedError(address target)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  TARGET_NOT_AUTHORIZED_ERROR_SELECTOR,
                                  target
                              );
                          }
                          function ZeroCantBeAuthorizedError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return ZERO_CANT_BE_AUTHORIZED_ERROR_BYTES;
                          }
                      }
                      /*
                        Copyright 2019 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./interfaces/IOwnableV06.sol";
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibOwnableRichErrorsV06.sol";
                      contract OwnableV06 is
                          IOwnableV06
                      {
                          /// @dev The owner of this contract.
                          /// @return 0 The owner address.
                          address public override owner;
                          constructor() public {
                              owner = msg.sender;
                          }
                          modifier onlyOwner() {
                              _assertSenderIsOwner();
                              _;
                          }
                          /// @dev Change the owner of this contract.
                          /// @param newOwner New owner address.
                          function transferOwnership(address newOwner)
                              public
                              override
                              onlyOwner
                          {
                              if (newOwner == address(0)) {
                                  LibRichErrorsV06.rrevert(LibOwnableRichErrorsV06.TransferOwnerToZeroError());
                              } else {
                                  owner = newOwner;
                                  emit OwnershipTransferred(msg.sender, newOwner);
                              }
                          }
                          function _assertSenderIsOwner()
                              internal
                              view
                          {
                              if (msg.sender != owner) {
                                  LibRichErrorsV06.rrevert(LibOwnableRichErrorsV06.OnlyOwnerError(
                                      msg.sender,
                                      owner
                                  ));
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibOwnableRichErrorsV06 {
                          // bytes4(keccak256("OnlyOwnerError(address,address)"))
                          bytes4 internal constant ONLY_OWNER_ERROR_SELECTOR =
                              0x1de45ad1;
                          // bytes4(keccak256("TransferOwnerToZeroError()"))
                          bytes internal constant TRANSFER_OWNER_TO_ZERO_ERROR_BYTES =
                              hex"e69edc3e";
                          // solhint-disable func-name-mixedcase
                          function OnlyOwnerError(
                              address sender,
                              address owner
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  ONLY_OWNER_ERROR_SELECTOR,
                                  sender,
                                  owner
                              );
                          }
                          function TransferOwnerToZeroError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return TRANSFER_OWNER_TO_ZERO_ERROR_BYTES;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/interfaces/IAuthorizableV06.sol";
                      /// @dev The allowance target for the TokenSpender feature.
                      interface IAllowanceTarget is
                          IAuthorizableV06
                      {
                          /// @dev Execute an arbitrary call. Only an authority can call this.
                          /// @param target The call target.
                          /// @param callData The call data.
                          /// @return resultData The data returned by the call.
                          function executeCall(
                              address payable target,
                              bytes calldata callData
                          )
                              external
                              returns (bytes memory resultData);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibOwnableRichErrorsV06.sol";
                      import "../errors/LibWalletRichErrors.sol";
                      import "./IFlashWallet.sol";
                      /// @dev A contract that can execute arbitrary calls from its owner.
                      contract FlashWallet is
                          IFlashWallet
                      {
                          // solhint-disable no-unused-vars,indent,no-empty-blocks
                          using LibRichErrorsV06 for bytes;
                          // solhint-disable
                          /// @dev Store the owner/deployer as an immutable to make this contract stateless.
                          address public override immutable owner;
                          // solhint-enable
                          constructor() public {
                              // The deployer is the owner.
                              owner = msg.sender;
                          }
                          /// @dev Allows only the (immutable) owner to call a function.
                          modifier onlyOwner() virtual {
                              if (msg.sender != owner) {
                                  LibOwnableRichErrorsV06.OnlyOwnerError(
                                      msg.sender,
                                      owner
                                  ).rrevert();
                              }
                              _;
                          }
                          /// @dev Execute an arbitrary call. Only an authority can call this.
                          /// @param target The call target.
                          /// @param callData The call data.
                          /// @param value Ether to attach to the call.
                          /// @return resultData The data returned by the call.
                          function executeCall(
                              address payable target,
                              bytes calldata callData,
                              uint256 value
                          )
                              external
                              payable
                              override
                              onlyOwner
                              returns (bytes memory resultData)
                          {
                              bool success;
                              (success, resultData) = target.call{value: value}(callData);
                              if (!success) {
                                  LibWalletRichErrors
                                      .WalletExecuteCallFailedError(
                                          address(this),
                                          target,
                                          callData,
                                          value,
                                          resultData
                                      )
                                      .rrevert();
                              }
                          }
                          /// @dev Execute an arbitrary delegatecall, in the context of this puppet.
                          ///      Only an authority can call this.
                          /// @param target The call target.
                          /// @param callData The call data.
                          /// @return resultData The data returned by the call.
                          function executeDelegateCall(
                              address payable target,
                              bytes calldata callData
                          )
                              external
                              payable
                              override
                              onlyOwner
                              returns (bytes memory resultData)
                          {
                              bool success;
                              (success, resultData) = target.delegatecall(callData);
                              if (!success) {
                                  LibWalletRichErrors
                                      .WalletExecuteDelegateCallFailedError(
                                          address(this),
                                          target,
                                          callData,
                                          resultData
                                      )
                                      .rrevert();
                              }
                          }
                          // solhint-disable
                          /// @dev Allows this contract to receive ether.
                          receive() external override payable {}
                          // solhint-enable
                          /// @dev Signal support for receiving ERC1155 tokens.
                          /// @param interfaceID The interface ID, as per ERC-165 rules.
                          /// @return hasSupport `true` if this contract supports an ERC-165 interface.
                          function supportsInterface(bytes4 interfaceID)
                              external
                              pure
                              returns (bool hasSupport)
                          {
                              return  interfaceID == this.supportsInterface.selector ||
                                      interfaceID == this.onERC1155Received.selector ^ this.onERC1155BatchReceived.selector ||
                                      interfaceID == this.tokenFallback.selector;
                          }
                          ///  @dev Allow this contract to receive ERC1155 tokens.
                          ///  @return success  `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
                          function onERC1155Received(
                              address, // operator,
                              address, // from,
                              uint256, // id,
                              uint256, // value,
                              bytes calldata //data
                          )
                              external
                              pure
                              returns (bytes4 success)
                          {
                              return this.onERC1155Received.selector;
                          }
                          ///  @dev Allow this contract to receive ERC1155 tokens.
                          ///  @return success  `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
                          function onERC1155BatchReceived(
                              address, // operator,
                              address, // from,
                              uint256[] calldata, // ids,
                              uint256[] calldata, // values,
                              bytes calldata // data
                          )
                              external
                              pure
                              returns (bytes4 success)
                          {
                              return this.onERC1155BatchReceived.selector;
                          }
                          /// @dev Allows this contract to receive ERC223 tokens.
                          function tokenFallback(
                              address, // from,
                              uint256, // value,
                              bytes calldata // value
                          )
                              external
                              pure
                          {}
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/interfaces/IOwnableV06.sol";
                      /// @dev A contract that can execute arbitrary calls from its owner.
                      interface IFlashWallet {
                          /// @dev Execute an arbitrary call. Only an authority can call this.
                          /// @param target The call target.
                          /// @param callData The call data.
                          /// @param value Ether to attach to the call.
                          /// @return resultData The data returned by the call.
                          function executeCall(
                              address payable target,
                              bytes calldata callData,
                              uint256 value
                          )
                              external
                              payable
                              returns (bytes memory resultData);
                          /// @dev Execute an arbitrary delegatecall, in the context of this puppet.
                          ///      Only an authority can call this.
                          /// @param target The call target.
                          /// @param callData The call data.
                          /// @return resultData The data returned by the call.
                          function executeDelegateCall(
                              address payable target,
                              bytes calldata callData
                          )
                              external
                              payable
                              returns (bytes memory resultData);
                          /// @dev Allows the puppet to receive ETH.
                          receive() external payable;
                          /// @dev Fetch the immutable owner/deployer of this contract.
                          /// @return owner_ The immutable owner/deployer/
                          function owner() external view returns (address owner_);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/AuthorizableV06.sol";
                      /// @dev A contract with a `die()` function.
                      interface IKillable {
                          function die() external;
                      }
                      /// @dev Deployer contract for ERC20 transformers.
                      ///      Only authorities may call `deploy()` and `kill()`.
                      contract TransformerDeployer is
                          AuthorizableV06
                      {
                          /// @dev Emitted when a contract is deployed via `deploy()`.
                          /// @param deployedAddress The address of the deployed contract.
                          /// @param nonce The deployment nonce.
                          /// @param sender The caller of `deploy()`.
                          event Deployed(address deployedAddress, uint256 nonce, address sender);
                          /// @dev Emitted when a contract is killed via `kill()`.
                          /// @param target The address of the contract being killed..
                          /// @param sender The caller of `kill()`.
                          event Killed(address target, address sender);
                          // @dev The current nonce of this contract.
                          uint256 public nonce = 1;
                          // @dev Mapping of deployed contract address to deployment nonce.
                          mapping (address => uint256) public toDeploymentNonce;
                          /// @dev Create this contract and register authorities.
                          constructor(address[] memory authorities) public {
                              for (uint256 i = 0; i < authorities.length; ++i) {
                                  _addAuthorizedAddress(authorities[i]);
                              }
                          }
                          /// @dev Deploy a new contract. Only callable by an authority.
                          ///      Any attached ETH will also be forwarded.
                          function deploy(bytes memory bytecode)
                              public
                              payable
                              onlyAuthorized
                              returns (address deployedAddress)
                          {
                              uint256 deploymentNonce = nonce;
                              nonce += 1;
                              assembly {
                                  deployedAddress := create(callvalue(), add(bytecode, 32), mload(bytecode))
                              }
                              toDeploymentNonce[deployedAddress] = deploymentNonce;
                              emit Deployed(deployedAddress, deploymentNonce, msg.sender);
                          }
                          /// @dev Call `die()` on a contract. Only callable by an authority.
                          function kill(IKillable target)
                              public
                              onlyAuthorized
                          {
                              target.die();
                              emit Killed(address(target), msg.sender);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Basic interface for a feature contract.
                      interface IFeature {
                          // solhint-disable func-name-mixedcase
                          /// @dev The name of this feature set.
                          function FEATURE_NAME() external view returns (string memory name);
                          /// @dev The version of this feature set.
                          function FEATURE_VERSION() external view returns (uint256 version);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/interfaces/IOwnableV06.sol";
                      // solhint-disable no-empty-blocks
                      /// @dev Owner management and migration features.
                      interface IOwnable is
                          IOwnableV06
                      {
                          /// @dev Emitted when `migrate()` is called.
                          /// @param caller The caller of `migrate()`.
                          /// @param migrator The migration contract.
                          /// @param newOwner The address of the new owner.
                          event Migrated(address caller, address migrator, address newOwner);
                          /// @dev Execute a migration function in the context of the ZeroEx contract.
                          ///      The result of the function being called should be the magic bytes
                          ///      0x2c64c5ef (`keccack('MIGRATE_SUCCESS')`). Only callable by the owner.
                          ///      The owner will be temporarily set to `address(this)` inside the call.
                          ///      Before returning, the owner will be set to `newOwner`.
                          /// @param target The migrator contract address.
                          /// @param newOwner The address of the new owner.
                          /// @param data The call data.
                          function migrate(address target, bytes calldata data, address newOwner) external;
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Basic registry management features.
                      interface ISimpleFunctionRegistry {
                          /// @dev A function implementation was updated via `extend()` or `rollback()`.
                          /// @param selector The function selector.
                          /// @param oldImpl The implementation contract address being replaced.
                          /// @param newImpl The replacement implementation contract address.
                          event ProxyFunctionUpdated(bytes4 indexed selector, address oldImpl, address newImpl);
                          /// @dev Roll back to a prior implementation of a function.
                          /// @param selector The function selector.
                          /// @param targetImpl The address of an older implementation of the function.
                          function rollback(bytes4 selector, address targetImpl) external;
                          /// @dev Register or replace a function.
                          /// @param selector The function selector.
                          /// @param impl The implementation contract for the function.
                          function extend(bytes4 selector, address impl) external;
                          /// @dev Retrieve the length of the rollback history for a function.
                          /// @param selector The function selector.
                          /// @return rollbackLength The number of items in the rollback history for
                          ///         the function.
                          function getRollbackLength(bytes4 selector)
                              external
                              view
                              returns (uint256 rollbackLength);
                          /// @dev Retrieve an entry in the rollback history for a function.
                          /// @param selector The function selector.
                          /// @param idx The index in the rollback history.
                          /// @return impl An implementation address for the function at
                          ///         index `idx`.
                          function getRollbackEntryAtIndex(bytes4 selector, uint256 idx)
                              external
                              view
                              returns (address impl);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      /// @dev Feature that allows spending token allowances.
                      interface ITokenSpender {
                          /// @dev Transfers ERC20 tokens from `owner` to `to`.
                          ///      Only callable from within.
                          /// @param token The token to spend.
                          /// @param owner The owner of the tokens.
                          /// @param to The recipient of the tokens.
                          /// @param amount The amount of `token` to transfer.
                          function _spendERC20Tokens(
                              IERC20TokenV06 token,
                              address owner,
                              address to,
                              uint256 amount
                          )
                              external;
                          /// @dev Gets the maximum amount of an ERC20 token `token` that can be
                          ///      pulled from `owner`.
                          /// @param token The token to spend.
                          /// @param owner The owner of the tokens.
                          /// @return amount The amount of tokens that can be pulled.
                          function getSpendableERC20BalanceOf(IERC20TokenV06 token, address owner)
                              external
                              view
                              returns (uint256 amount);
                          /// @dev Get the address of the allowance target.
                          /// @return target The target of token allowances.
                          function getAllowanceTarget() external view returns (address target);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      interface IERC20TokenV06 {
                          // solhint-disable no-simple-event-func-name
                          event Transfer(
                              address indexed from,
                              address indexed to,
                              uint256 value
                          );
                          event Approval(
                              address indexed owner,
                              address indexed spender,
                              uint256 value
                          );
                          /// @dev send `value` token to `to` from `msg.sender`
                          /// @param to The address of the recipient
                          /// @param value The amount of token to be transferred
                          /// @return True if transfer was successful
                          function transfer(address to, uint256 value)
                              external
                              returns (bool);
                          /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
                          /// @param from The address of the sender
                          /// @param to The address of the recipient
                          /// @param value The amount of token to be transferred
                          /// @return True if transfer was successful
                          function transferFrom(
                              address from,
                              address to,
                              uint256 value
                          )
                              external
                              returns (bool);
                          /// @dev `msg.sender` approves `spender` to spend `value` tokens
                          /// @param spender The address of the account able to transfer the tokens
                          /// @param value The amount of wei to be approved for transfer
                          /// @return Always true if the call has enough gas to complete execution
                          function approve(address spender, uint256 value)
                              external
                              returns (bool);
                          /// @dev Query total supply of token
                          /// @return Total supply of token
                          function totalSupply()
                              external
                              view
                              returns (uint256);
                          /// @dev Get the balance of `owner`.
                          /// @param owner The address from which the balance will be retrieved
                          /// @return Balance of owner
                          function balanceOf(address owner)
                              external
                              view
                              returns (uint256);
                          /// @dev Get the allowance for `spender` to spend from `owner`.
                          /// @param owner The address of the account owning tokens
                          /// @param spender The address of the account able to transfer the tokens
                          /// @return Amount of remaining tokens allowed to spent
                          function allowance(address owner, address spender)
                              external
                              view
                              returns (uint256);
                          /// @dev Get the number of decimals this token has.
                          function decimals()
                              external
                              view
                              returns (uint8);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "../transformers/IERC20Transformer.sol";
                      import "../external/IFlashWallet.sol";
                      /// @dev Feature to composably transform between ERC20 tokens.
                      interface ITransformERC20 {
                          /// @dev Defines a transformation to run in `transformERC20()`.
                          struct Transformation {
                              // The deployment nonce for the transformer.
                              // The address of the transformer contract will be derived from this
                              // value.
                              uint32 deploymentNonce;
                              // Arbitrary data to pass to the transformer.
                              bytes data;
                          }
                          /// @dev Raised upon a successful `transformERC20`.
                          /// @param taker The taker (caller) address.
                          /// @param inputToken The token being provided by the taker.
                          ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                          /// @param outputToken The token to be acquired by the taker.
                          ///        `0xeee...` implies ETH.
                          /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                          /// @param outputTokenAmount The amount of `outputToken` received by the taker.
                          event TransformedERC20(
                              address indexed taker,
                              address inputToken,
                              address outputToken,
                              uint256 inputTokenAmount,
                              uint256 outputTokenAmount
                          );
                          /// @dev Raised when `setTransformerDeployer()` is called.
                          /// @param transformerDeployer The new deployer address.
                          event TransformerDeployerUpdated(address transformerDeployer);
                          /// @dev Replace the allowed deployer for transformers.
                          ///      Only callable by the owner.
                          /// @param transformerDeployer The address of the trusted deployer for transformers.
                          function setTransformerDeployer(address transformerDeployer)
                              external;
                          /// @dev Deploy a new flash wallet instance and replace the current one with it.
                          ///      Useful if we somehow break the current wallet instance.
                          ///      Anyone can call this.
                          /// @return wallet The new wallet instance.
                          function createTransformWallet()
                              external
                              returns (IFlashWallet wallet);
                          /// @dev Executes a series of transformations to convert an ERC20 `inputToken`
                          ///      to an ERC20 `outputToken`.
                          /// @param inputToken The token being provided by the sender.
                          ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                          /// @param outputToken The token to be acquired by the sender.
                          ///        `0xeee...` implies ETH.
                          /// @param inputTokenAmount The amount of `inputToken` to take from the sender.
                          /// @param minOutputTokenAmount The minimum amount of `outputToken` the sender
                          ///        must receive for the entire transformation to succeed.
                          /// @param transformations The transformations to execute on the token balance(s)
                          ///        in sequence.
                          /// @return outputTokenAmount The amount of `outputToken` received by the sender.
                          function transformERC20(
                              IERC20TokenV06 inputToken,
                              IERC20TokenV06 outputToken,
                              uint256 inputTokenAmount,
                              uint256 minOutputTokenAmount,
                              Transformation[] calldata transformations
                          )
                              external
                              payable
                              returns (uint256 outputTokenAmount);
                          /// @dev Internal version of `transformERC20()`. Only callable from within.
                          /// @param callDataHash Hash of the ingress calldata.
                          /// @param taker The taker address.
                          /// @param inputToken The token being provided by the taker.
                          ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                          /// @param outputToken The token to be acquired by the taker.
                          ///        `0xeee...` implies ETH.
                          /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                          /// @param minOutputTokenAmount The minimum amount of `outputToken` the taker
                          ///        must receive for the entire transformation to succeed.
                          /// @param transformations The transformations to execute on the token balance(s)
                          ///        in sequence.
                          /// @return outputTokenAmount The amount of `outputToken` received by the taker.
                          function _transformERC20(
                              bytes32 callDataHash,
                              address payable taker,
                              IERC20TokenV06 inputToken,
                              IERC20TokenV06 outputToken,
                              uint256 inputTokenAmount,
                              uint256 minOutputTokenAmount,
                              Transformation[] calldata transformations
                          )
                              external
                              payable
                              returns (uint256 outputTokenAmount);
                          /// @dev Return the current wallet instance that will serve as the execution
                          ///      context for transformations.
                          /// @return wallet The wallet instance.
                          function getTransformWallet()
                              external
                              view
                              returns (IFlashWallet wallet);
                          /// @dev Return the allowed deployer for transformers.
                          /// @return deployer The transform deployer address.
                          function getTransformerDeployer()
                              external
                              view
                              returns (address deployer);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      /// @dev A transformation callback used in `TransformERC20.transformERC20()`.
                      interface IERC20Transformer {
                          /// @dev Called from `TransformERC20.transformERC20()`. This will be
                          ///      delegatecalled in the context of the FlashWallet instance being used.
                          /// @param callDataHash The hash of the `TransformERC20.transformERC20()` calldata.
                          /// @param taker The taker address (caller of `TransformERC20.transformERC20()`).
                          /// @param data Arbitrary data to pass to the transformer.
                          /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                          function transform(
                              bytes32 callDataHash,
                              address payable taker,
                              bytes calldata data
                          )
                              external
                              returns (bytes4 success);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../fixins/FixinCommon.sol";
                      import "../errors/LibOwnableRichErrors.sol";
                      import "../storage/LibOwnableStorage.sol";
                      import "../migrations/LibBootstrap.sol";
                      import "../migrations/LibMigrate.sol";
                      import "./IFeature.sol";
                      import "./IOwnable.sol";
                      import "./SimpleFunctionRegistry.sol";
                      /// @dev Owner management features.
                      contract Ownable is
                          IFeature,
                          IOwnable,
                          FixinCommon
                      {
                          // solhint-disable
                          /// @dev Name of this feature.
                          string public constant override FEATURE_NAME = "Ownable";
                          /// @dev Version of this feature.
                          uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                          /// @dev The deployed address of this contract.
                          address immutable private _implementation;
                          // solhint-enable
                          using LibRichErrorsV06 for bytes;
                          constructor() public {
                              _implementation = address(this);
                          }
                          /// @dev Initializes this feature. The intial owner will be set to this (ZeroEx)
                          ///      to allow the bootstrappers to call `extend()`. Ownership should be
                          ///      transferred to the real owner by the bootstrapper after
                          ///      bootstrapping is complete.
                          /// @return success Magic bytes if successful.
                          function bootstrap() external returns (bytes4 success) {
                              // Set the owner to ourselves to allow bootstrappers to call `extend()`.
                              LibOwnableStorage.getStorage().owner = address(this);
                              // Register feature functions.
                              SimpleFunctionRegistry(address(this))._extendSelf(this.transferOwnership.selector, _implementation);
                              SimpleFunctionRegistry(address(this))._extendSelf(this.owner.selector, _implementation);
                              SimpleFunctionRegistry(address(this))._extendSelf(this.migrate.selector, _implementation);
                              return LibBootstrap.BOOTSTRAP_SUCCESS;
                          }
                          /// @dev Change the owner of this contract.
                          ///      Only directly callable by the owner.
                          /// @param newOwner New owner address.
                          function transferOwnership(address newOwner)
                              external
                              override
                              onlyOwner
                          {
                              LibOwnableStorage.Storage storage proxyStor = LibOwnableStorage.getStorage();
                              if (newOwner == address(0)) {
                                  LibOwnableRichErrors.TransferOwnerToZeroError().rrevert();
                              } else {
                                  proxyStor.owner = newOwner;
                                  emit OwnershipTransferred(msg.sender, newOwner);
                              }
                          }
                          /// @dev Execute a migration function in the context of the ZeroEx contract.
                          ///      The result of the function being called should be the magic bytes
                          ///      0x2c64c5ef (`keccack('MIGRATE_SUCCESS')`). Only callable by the owner.
                          ///      Temporarily sets the owner to ourselves so we can perform admin functions.
                          ///      Before returning, the owner will be set to `newOwner`.
                          /// @param target The migrator contract address.
                          /// @param data The call data.
                          /// @param newOwner The address of the new owner.
                          function migrate(address target, bytes calldata data, address newOwner)
                              external
                              override
                              onlyOwner
                          {
                              if (newOwner == address(0)) {
                                  LibOwnableRichErrors.TransferOwnerToZeroError().rrevert();
                              }
                              LibOwnableStorage.Storage storage stor = LibOwnableStorage.getStorage();
                              // The owner will be temporarily set to `address(this)` inside the call.
                              stor.owner = address(this);
                              // Perform the migration.
                              LibMigrate.delegatecallMigrateFunction(target, data);
                              // Update the owner.
                              stor.owner = newOwner;
                              emit Migrated(msg.sender, target, newOwner);
                          }
                          /// @dev Get the owner of this contract.
                          /// @return owner_ The owner of this contract.
                          function owner() external override view returns (address owner_) {
                              return LibOwnableStorage.getStorage().owner;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../errors/LibCommonRichErrors.sol";
                      import "../errors/LibOwnableRichErrors.sol";
                      import "../features/IOwnable.sol";
                      /// @dev Common feature utilities.
                      contract FixinCommon {
                          using LibRichErrorsV06 for bytes;
                          /// @dev The caller must be this contract.
                          modifier onlySelf() virtual {
                              if (msg.sender != address(this)) {
                                  LibCommonRichErrors.OnlyCallableBySelfError(msg.sender).rrevert();
                              }
                              _;
                          }
                          /// @dev The caller of this function must be the owner.
                          modifier onlyOwner() virtual {
                              {
                                  address owner = IOwnable(address(this)).owner();
                                  if (msg.sender != owner) {
                                      LibOwnableRichErrors.OnlyOwnerError(
                                          msg.sender,
                                          owner
                                      ).rrevert();
                                  }
                              }
                              _;
                          }
                          /// @dev Encode a feature version as a `uint256`.
                          /// @param major The major version number of the feature.
                          /// @param minor The minor version number of the feature.
                          /// @param revision The revision number of the feature.
                          /// @return encodedVersion The encoded version number.
                          function _encodeVersion(uint32 major, uint32 minor, uint32 revision)
                              internal
                              pure
                              returns (uint256 encodedVersion)
                          {
                              return (major << 64) | (minor << 32) | revision;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./LibStorage.sol";
                      /// @dev Storage helpers for the `Ownable` feature.
                      library LibOwnableStorage {
                          /// @dev Storage bucket for this feature.
                          struct Storage {
                              // The owner of this contract.
                              address owner;
                          }
                          /// @dev Get the storage bucket for this contract.
                          function getStorage() internal pure returns (Storage storage stor) {
                              uint256 storageSlot = LibStorage.getStorageSlot(
                                  LibStorage.StorageId.Ownable
                              );
                              // Dip into assembly to change the slot pointed to by the local
                              // variable `stor`.
                              // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                              assembly { stor_slot := storageSlot }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../errors/LibOwnableRichErrors.sol";
                      library LibMigrate {
                          /// @dev Magic bytes returned by a migrator to indicate success.
                          ///      This is `keccack('MIGRATE_SUCCESS')`.
                          bytes4 internal constant MIGRATE_SUCCESS = 0x2c64c5ef;
                          using LibRichErrorsV06 for bytes;
                          /// @dev Perform a delegatecall and ensure it returns the magic bytes.
                          /// @param target The call target.
                          /// @param data The call data.
                          function delegatecallMigrateFunction(
                              address target,
                              bytes memory data
                          )
                              internal
                          {
                              (bool success, bytes memory resultData) = target.delegatecall(data);
                              if (!success ||
                                  resultData.length != 32 ||
                                  abi.decode(resultData, (bytes4)) != MIGRATE_SUCCESS)
                              {
                                  LibOwnableRichErrors.MigrateCallFailedError(target, resultData).rrevert();
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../fixins/FixinCommon.sol";
                      import "../storage/LibProxyStorage.sol";
                      import "../storage/LibSimpleFunctionRegistryStorage.sol";
                      import "../errors/LibSimpleFunctionRegistryRichErrors.sol";
                      import "../migrations/LibBootstrap.sol";
                      import "./IFeature.sol";
                      import "./ISimpleFunctionRegistry.sol";
                      /// @dev Basic registry management features.
                      contract SimpleFunctionRegistry is
                          IFeature,
                          ISimpleFunctionRegistry,
                          FixinCommon
                      {
                          // solhint-disable
                          /// @dev Name of this feature.
                          string public constant override FEATURE_NAME = "SimpleFunctionRegistry";
                          /// @dev Version of this feature.
                          uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                          /// @dev The deployed address of this contract.
                          address private immutable _implementation;
                          // solhint-enable
                          using LibRichErrorsV06 for bytes;
                          constructor() public {
                              _implementation = address(this);
                          }
                          /// @dev Initializes this feature, registering its own functions.
                          /// @return success Magic bytes if successful.
                          function bootstrap()
                              external
                              returns (bytes4 success)
                          {
                              // Register the registration functions (inception vibes).
                              _extend(this.extend.selector, _implementation);
                              _extend(this._extendSelf.selector, _implementation);
                              // Register the rollback function.
                              _extend(this.rollback.selector, _implementation);
                              // Register getters.
                              _extend(this.getRollbackLength.selector, _implementation);
                              _extend(this.getRollbackEntryAtIndex.selector, _implementation);
                              return LibBootstrap.BOOTSTRAP_SUCCESS;
                          }
                          /// @dev Roll back to a prior implementation of a function.
                          ///      Only directly callable by an authority.
                          /// @param selector The function selector.
                          /// @param targetImpl The address of an older implementation of the function.
                          function rollback(bytes4 selector, address targetImpl)
                              external
                              override
                              onlyOwner
                          {
                              (
                                  LibSimpleFunctionRegistryStorage.Storage storage stor,
                                  LibProxyStorage.Storage storage proxyStor
                              ) = _getStorages();
                              address currentImpl = proxyStor.impls[selector];
                              if (currentImpl == targetImpl) {
                                  // Do nothing if already at targetImpl.
                                  return;
                              }
                              // Walk history backwards until we find the target implementation.
                              address[] storage history = stor.implHistory[selector];
                              uint256 i = history.length;
                              for (; i > 0; --i) {
                                  address impl = history[i - 1];
                                  history.pop();
                                  if (impl == targetImpl) {
                                      break;
                                  }
                              }
                              if (i == 0) {
                                  LibSimpleFunctionRegistryRichErrors.NotInRollbackHistoryError(
                                      selector,
                                      targetImpl
                                  ).rrevert();
                              }
                              proxyStor.impls[selector] = targetImpl;
                              emit ProxyFunctionUpdated(selector, currentImpl, targetImpl);
                          }
                          /// @dev Register or replace a function.
                          ///      Only directly callable by an authority.
                          /// @param selector The function selector.
                          /// @param impl The implementation contract for the function.
                          function extend(bytes4 selector, address impl)
                              external
                              override
                              onlyOwner
                          {
                              _extend(selector, impl);
                          }
                          /// @dev Register or replace a function.
                          ///      Only callable from within.
                          ///      This function is only used during the bootstrap process and
                          ///      should be deregistered by the deployer after bootstrapping is
                          ///      complete.
                          /// @param selector The function selector.
                          /// @param impl The implementation contract for the function.
                          function _extendSelf(bytes4 selector, address impl)
                              external
                              onlySelf
                          {
                              _extend(selector, impl);
                          }
                          /// @dev Retrieve the length of the rollback history for a function.
                          /// @param selector The function selector.
                          /// @return rollbackLength The number of items in the rollback history for
                          ///         the function.
                          function getRollbackLength(bytes4 selector)
                              external
                              override
                              view
                              returns (uint256 rollbackLength)
                          {
                              return LibSimpleFunctionRegistryStorage.getStorage().implHistory[selector].length;
                          }
                          /// @dev Retrieve an entry in the rollback history for a function.
                          /// @param selector The function selector.
                          /// @param idx The index in the rollback history.
                          /// @return impl An implementation address for the function at
                          ///         index `idx`.
                          function getRollbackEntryAtIndex(bytes4 selector, uint256 idx)
                              external
                              override
                              view
                              returns (address impl)
                          {
                              return LibSimpleFunctionRegistryStorage.getStorage().implHistory[selector][idx];
                          }
                          /// @dev Register or replace a function.
                          /// @param selector The function selector.
                          /// @param impl The implementation contract for the function.
                          function _extend(bytes4 selector, address impl)
                              private
                          {
                              (
                                  LibSimpleFunctionRegistryStorage.Storage storage stor,
                                  LibProxyStorage.Storage storage proxyStor
                              ) = _getStorages();
                              address oldImpl = proxyStor.impls[selector];
                              address[] storage history = stor.implHistory[selector];
                              history.push(oldImpl);
                              proxyStor.impls[selector] = impl;
                              emit ProxyFunctionUpdated(selector, oldImpl, impl);
                          }
                          /// @dev Get the storage buckets for this feature and the proxy.
                          /// @return stor Storage bucket for this feature.
                          /// @return proxyStor age bucket for the proxy.
                          function _getStorages()
                              private
                              pure
                              returns (
                                  LibSimpleFunctionRegistryStorage.Storage storage stor,
                                  LibProxyStorage.Storage storage proxyStor
                              )
                          {
                              return (
                                  LibSimpleFunctionRegistryStorage.getStorage(),
                                  LibProxyStorage.getStorage()
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./LibStorage.sol";
                      /// @dev Storage helpers for the `SimpleFunctionRegistry` feature.
                      library LibSimpleFunctionRegistryStorage {
                          /// @dev Storage bucket for this feature.
                          struct Storage {
                              // Mapping of function selector -> implementation history.
                              mapping(bytes4 => address[]) implHistory;
                          }
                          /// @dev Get the storage bucket for this contract.
                          function getStorage() internal pure returns (Storage storage stor) {
                              uint256 storageSlot = LibStorage.getStorageSlot(
                                  LibStorage.StorageId.SimpleFunctionRegistry
                              );
                              // Dip into assembly to change the slot pointed to by the local
                              // variable `stor`.
                              // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                              assembly { stor_slot := storageSlot }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
                      import "../errors/LibSpenderRichErrors.sol";
                      import "../fixins/FixinCommon.sol";
                      import "../migrations/LibMigrate.sol";
                      import "../external/IAllowanceTarget.sol";
                      import "../storage/LibTokenSpenderStorage.sol";
                      import "./ITokenSpender.sol";
                      import "./IFeature.sol";
                      import "./ISimpleFunctionRegistry.sol";
                      /// @dev Feature that allows spending token allowances.
                      contract TokenSpender is
                          IFeature,
                          ITokenSpender,
                          FixinCommon
                      {
                          // solhint-disable
                          /// @dev Name of this feature.
                          string public constant override FEATURE_NAME = "TokenSpender";
                          /// @dev Version of this feature.
                          uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                          /// @dev The implementation address of this feature.
                          address private immutable _implementation;
                          // solhint-enable
                          using LibRichErrorsV06 for bytes;
                          constructor() public {
                              _implementation = address(this);
                          }
                          /// @dev Initialize and register this feature. Should be delegatecalled
                          ///      into during a `Migrate.migrate()`.
                          /// @param allowanceTarget An `allowanceTarget` instance, configured to have
                          ///        the ZeroeEx contract as an authority.
                          /// @return success `MIGRATE_SUCCESS` on success.
                          function migrate(IAllowanceTarget allowanceTarget) external returns (bytes4 success) {
                              LibTokenSpenderStorage.getStorage().allowanceTarget = allowanceTarget;
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this.getAllowanceTarget.selector, _implementation);
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this._spendERC20Tokens.selector, _implementation);
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this.getSpendableERC20BalanceOf.selector, _implementation);
                              return LibMigrate.MIGRATE_SUCCESS;
                          }
                          /// @dev Transfers ERC20 tokens from `owner` to `to`. Only callable from within.
                          /// @param token The token to spend.
                          /// @param owner The owner of the tokens.
                          /// @param to The recipient of the tokens.
                          /// @param amount The amount of `token` to transfer.
                          function _spendERC20Tokens(
                              IERC20TokenV06 token,
                              address owner,
                              address to,
                              uint256 amount
                          )
                              external
                              override
                              onlySelf
                          {
                              IAllowanceTarget spender = LibTokenSpenderStorage.getStorage().allowanceTarget;
                              // Have the allowance target execute an ERC20 `transferFrom()`.
                              (bool didSucceed, bytes memory resultData) = address(spender).call(
                                  abi.encodeWithSelector(
                                      IAllowanceTarget.executeCall.selector,
                                      address(token),
                                      abi.encodeWithSelector(
                                          IERC20TokenV06.transferFrom.selector,
                                          owner,
                                          to,
                                          amount
                                      )
                                  )
                              );
                              if (didSucceed) {
                                  resultData = abi.decode(resultData, (bytes));
                              }
                              if (!didSucceed || !LibERC20TokenV06.isSuccessfulResult(resultData)) {
                                  LibSpenderRichErrors.SpenderERC20TransferFromFailedError(
                                      address(token),
                                      owner,
                                      to,
                                      amount,
                                      resultData
                                  ).rrevert();
                              }
                          }
                          /// @dev Gets the maximum amount of an ERC20 token `token` that can be
                          ///      pulled from `owner` by the token spender.
                          /// @param token The token to spend.
                          /// @param owner The owner of the tokens.
                          /// @return amount The amount of tokens that can be pulled.
                          function getSpendableERC20BalanceOf(IERC20TokenV06 token, address owner)
                              external
                              override
                              view
                              returns (uint256 amount)
                          {
                              return LibSafeMathV06.min256(
                                  token.allowance(owner, address(LibTokenSpenderStorage.getStorage().allowanceTarget)),
                                  token.balanceOf(owner)
                              );
                          }
                          /// @dev Get the address of the allowance target.
                          /// @return target The target of token allowances.
                          function getAllowanceTarget()
                              external
                              override
                              view
                              returns (address target)
                          {
                              return address(LibTokenSpenderStorage.getStorage().allowanceTarget);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibSafeMathRichErrorsV06.sol";
                      library LibSafeMathV06 {
                          function safeMul(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              if (a == 0) {
                                  return 0;
                              }
                              uint256 c = a * b;
                              if (c / a != b) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.MULTIPLICATION_OVERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return c;
                          }
                          function safeDiv(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              if (b == 0) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.DIVISION_BY_ZERO,
                                      a,
                                      b
                                  ));
                              }
                              uint256 c = a / b;
                              return c;
                          }
                          function safeSub(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              if (b > a) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.SUBTRACTION_UNDERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return a - b;
                          }
                          function safeAdd(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              uint256 c = a + b;
                              if (c < a) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.ADDITION_OVERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return c;
                          }
                          function max256(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              return a >= b ? a : b;
                          }
                          function min256(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              return a < b ? a : b;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibSafeMathRichErrorsV06 {
                          // bytes4(keccak256("Uint256BinOpError(uint8,uint256,uint256)"))
                          bytes4 internal constant UINT256_BINOP_ERROR_SELECTOR =
                              0xe946c1bb;
                          // bytes4(keccak256("Uint256DowncastError(uint8,uint256)"))
                          bytes4 internal constant UINT256_DOWNCAST_ERROR_SELECTOR =
                              0xc996af7b;
                          enum BinOpErrorCodes {
                              ADDITION_OVERFLOW,
                              MULTIPLICATION_OVERFLOW,
                              SUBTRACTION_UNDERFLOW,
                              DIVISION_BY_ZERO
                          }
                          enum DowncastErrorCodes {
                              VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT32,
                              VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT64,
                              VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT96
                          }
                          // solhint-disable func-name-mixedcase
                          function Uint256BinOpError(
                              BinOpErrorCodes errorCode,
                              uint256 a,
                              uint256 b
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  UINT256_BINOP_ERROR_SELECTOR,
                                  errorCode,
                                  a,
                                  b
                              );
                          }
                          function Uint256DowncastError(
                              DowncastErrorCodes errorCode,
                              uint256 a
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  UINT256_DOWNCAST_ERROR_SELECTOR,
                                  errorCode,
                                  a
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
                      import "./IERC20TokenV06.sol";
                      library LibERC20TokenV06 {
                          bytes constant private DECIMALS_CALL_DATA = hex"313ce567";
                          /// @dev Calls `IERC20TokenV06(token).approve()`.
                          ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                          /// @param token The address of the token contract.
                          /// @param spender The address that receives an allowance.
                          /// @param allowance The allowance to set.
                          function compatApprove(
                              IERC20TokenV06 token,
                              address spender,
                              uint256 allowance
                          )
                              internal
                          {
                              bytes memory callData = abi.encodeWithSelector(
                                  token.approve.selector,
                                  spender,
                                  allowance
                              );
                              _callWithOptionalBooleanResult(address(token), callData);
                          }
                          /// @dev Calls `IERC20TokenV06(token).approve()` and sets the allowance to the
                          ///      maximum if the current approval is not already >= an amount.
                          ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                          /// @param token The address of the token contract.
                          /// @param spender The address that receives an allowance.
                          /// @param amount The minimum allowance needed.
                          function approveIfBelow(
                              IERC20TokenV06 token,
                              address spender,
                              uint256 amount
                          )
                              internal
                          {
                              if (token.allowance(address(this), spender) < amount) {
                                  compatApprove(token, spender, uint256(-1));
                              }
                          }
                          /// @dev Calls `IERC20TokenV06(token).transfer()`.
                          ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                          /// @param token The address of the token contract.
                          /// @param to The address that receives the tokens
                          /// @param amount Number of tokens to transfer.
                          function compatTransfer(
                              IERC20TokenV06 token,
                              address to,
                              uint256 amount
                          )
                              internal
                          {
                              bytes memory callData = abi.encodeWithSelector(
                                  token.transfer.selector,
                                  to,
                                  amount
                              );
                              _callWithOptionalBooleanResult(address(token), callData);
                          }
                          /// @dev Calls `IERC20TokenV06(token).transferFrom()`.
                          ///      Reverts if the result fails `isSuccessfulResult()` or the call reverts.
                          /// @param token The address of the token contract.
                          /// @param from The owner of the tokens.
                          /// @param to The address that receives the tokens
                          /// @param amount Number of tokens to transfer.
                          function compatTransferFrom(
                              IERC20TokenV06 token,
                              address from,
                              address to,
                              uint256 amount
                          )
                              internal
                          {
                              bytes memory callData = abi.encodeWithSelector(
                                  token.transferFrom.selector,
                                  from,
                                  to,
                                  amount
                              );
                              _callWithOptionalBooleanResult(address(token), callData);
                          }
                          /// @dev Retrieves the number of decimals for a token.
                          ///      Returns `18` if the call reverts.
                          /// @param token The address of the token contract.
                          /// @return tokenDecimals The number of decimals places for the token.
                          function compatDecimals(IERC20TokenV06 token)
                              internal
                              view
                              returns (uint8 tokenDecimals)
                          {
                              tokenDecimals = 18;
                              (bool didSucceed, bytes memory resultData) = address(token).staticcall(DECIMALS_CALL_DATA);
                              if (didSucceed && resultData.length == 32) {
                                  tokenDecimals = uint8(LibBytesV06.readUint256(resultData, 0));
                              }
                          }
                          /// @dev Retrieves the allowance for a token, owner, and spender.
                          ///      Returns `0` if the call reverts.
                          /// @param token The address of the token contract.
                          /// @param owner The owner of the tokens.
                          /// @param spender The address the spender.
                          /// @return allowance_ The allowance for a token, owner, and spender.
                          function compatAllowance(IERC20TokenV06 token, address owner, address spender)
                              internal
                              view
                              returns (uint256 allowance_)
                          {
                              (bool didSucceed, bytes memory resultData) = address(token).staticcall(
                                  abi.encodeWithSelector(
                                      token.allowance.selector,
                                      owner,
                                      spender
                                  )
                              );
                              if (didSucceed && resultData.length == 32) {
                                  allowance_ = LibBytesV06.readUint256(resultData, 0);
                              }
                          }
                          /// @dev Retrieves the balance for a token owner.
                          ///      Returns `0` if the call reverts.
                          /// @param token The address of the token contract.
                          /// @param owner The owner of the tokens.
                          /// @return balance The token balance of an owner.
                          function compatBalanceOf(IERC20TokenV06 token, address owner)
                              internal
                              view
                              returns (uint256 balance)
                          {
                              (bool didSucceed, bytes memory resultData) = address(token).staticcall(
                                  abi.encodeWithSelector(
                                      token.balanceOf.selector,
                                      owner
                                  )
                              );
                              if (didSucceed && resultData.length == 32) {
                                  balance = LibBytesV06.readUint256(resultData, 0);
                              }
                          }
                          /// @dev Check if the data returned by a non-static call to an ERC20 token
                          ///      is a successful result. Supported functions are `transfer()`,
                          ///      `transferFrom()`, and `approve()`.
                          /// @param resultData The raw data returned by a non-static call to the ERC20 token.
                          /// @return isSuccessful Whether the result data indicates success.
                          function isSuccessfulResult(bytes memory resultData)
                              internal
                              pure
                              returns (bool isSuccessful)
                          {
                              if (resultData.length == 0) {
                                  return true;
                              }
                              if (resultData.length == 32) {
                                  uint256 result = LibBytesV06.readUint256(resultData, 0);
                                  if (result == 1) {
                                      return true;
                                  }
                              }
                          }
                          /// @dev Executes a call on address `target` with calldata `callData`
                          ///      and asserts that either nothing was returned or a single boolean
                          ///      was returned equal to `true`.
                          /// @param target The call target.
                          /// @param callData The abi-encoded call data.
                          function _callWithOptionalBooleanResult(
                              address target,
                              bytes memory callData
                          )
                              private
                          {
                              (bool didSucceed, bytes memory resultData) = target.call(callData);
                              if (didSucceed && isSuccessfulResult(resultData)) {
                                  return;
                              }
                              LibRichErrorsV06.rrevert(resultData);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./LibStorage.sol";
                      import "../external/IAllowanceTarget.sol";
                      /// @dev Storage helpers for the `TokenSpender` feature.
                      library LibTokenSpenderStorage {
                          /// @dev Storage bucket for this feature.
                          struct Storage {
                              // Allowance target contract.
                              IAllowanceTarget allowanceTarget;
                          }
                          /// @dev Get the storage bucket for this contract.
                          function getStorage() internal pure returns (Storage storage stor) {
                              uint256 storageSlot = LibStorage.getStorageSlot(
                                  LibStorage.StorageId.TokenSpender
                              );
                              // Dip into assembly to change the slot pointed to by the local
                              // variable `stor`.
                              // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                              assembly { stor_slot := storageSlot }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "../errors/LibTransformERC20RichErrors.sol";
                      import "../fixins/FixinCommon.sol";
                      import "../migrations/LibMigrate.sol";
                      import "../external/IFlashWallet.sol";
                      import "../external/FlashWallet.sol";
                      import "../storage/LibTransformERC20Storage.sol";
                      import "../transformers/IERC20Transformer.sol";
                      import "../transformers/LibERC20Transformer.sol";
                      import "./ITransformERC20.sol";
                      import "./ITokenSpender.sol";
                      import "./IFeature.sol";
                      import "./ISimpleFunctionRegistry.sol";
                      /// @dev Feature to composably transform between ERC20 tokens.
                      contract TransformERC20 is
                          IFeature,
                          ITransformERC20,
                          FixinCommon
                      {
                          /// @dev Stack vars for `_transformERC20Private()`.
                          struct TransformERC20PrivateState {
                              IFlashWallet wallet;
                              address transformerDeployer;
                              uint256 takerOutputTokenBalanceBefore;
                              uint256 takerOutputTokenBalanceAfter;
                          }
                          // solhint-disable
                          /// @dev Name of this feature.
                          string public constant override FEATURE_NAME = "TransformERC20";
                          /// @dev Version of this feature.
                          uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 0, 0);
                          /// @dev The implementation address of this feature.
                          address private immutable _implementation;
                          // solhint-enable
                          using LibSafeMathV06 for uint256;
                          using LibRichErrorsV06 for bytes;
                          constructor() public {
                              _implementation = address(this);
                          }
                          /// @dev Initialize and register this feature.
                          ///      Should be delegatecalled by `Migrate.migrate()`.
                          /// @param transformerDeployer The trusted deployer for transformers.
                          /// @return success `LibMigrate.SUCCESS` on success.
                          function migrate(address transformerDeployer) external returns (bytes4 success) {
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this.getTransformerDeployer.selector, _implementation);
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this.createTransformWallet.selector, _implementation);
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this.getTransformWallet.selector, _implementation);
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this.setTransformerDeployer.selector, _implementation);
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this.transformERC20.selector, _implementation);
                              ISimpleFunctionRegistry(address(this))
                                  .extend(this._transformERC20.selector, _implementation);
                              createTransformWallet();
                              LibTransformERC20Storage.getStorage().transformerDeployer = transformerDeployer;
                              return LibMigrate.MIGRATE_SUCCESS;
                          }
                          /// @dev Replace the allowed deployer for transformers.
                          ///      Only callable by the owner.
                          /// @param transformerDeployer The address of the trusted deployer for transformers.
                          function setTransformerDeployer(address transformerDeployer)
                              external
                              override
                              onlyOwner
                          {
                              LibTransformERC20Storage.getStorage().transformerDeployer = transformerDeployer;
                              emit TransformerDeployerUpdated(transformerDeployer);
                          }
                          /// @dev Return the allowed deployer for transformers.
                          /// @return deployer The transform deployer address.
                          function getTransformerDeployer()
                              public
                              override
                              view
                              returns (address deployer)
                          {
                              return LibTransformERC20Storage.getStorage().transformerDeployer;
                          }
                          /// @dev Deploy a new wallet instance and replace the current one with it.
                          ///      Useful if we somehow break the current wallet instance.
                          ///      Anyone can call this.
                          /// @return wallet The new wallet instance.
                          function createTransformWallet()
                              public
                              override
                              returns (IFlashWallet wallet)
                          {
                              wallet = new FlashWallet();
                              LibTransformERC20Storage.getStorage().wallet = wallet;
                          }
                          /// @dev Executes a series of transformations to convert an ERC20 `inputToken`
                          ///      to an ERC20 `outputToken`.
                          /// @param inputToken The token being provided by the sender.
                          ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                          /// @param outputToken The token to be acquired by the sender.
                          ///        `0xeee...` implies ETH.
                          /// @param inputTokenAmount The amount of `inputToken` to take from the sender.
                          ///        If set to `uint256(-1)`, the entire spendable balance of the taker
                          ///        will be solt.
                          /// @param minOutputTokenAmount The minimum amount of `outputToken` the sender
                          ///        must receive for the entire transformation to succeed. If set to zero,
                          ///        the minimum output token transfer will not be asserted.
                          /// @param transformations The transformations to execute on the token balance(s)
                          ///        in sequence.
                          /// @return outputTokenAmount The amount of `outputToken` received by the sender.
                          function transformERC20(
                              IERC20TokenV06 inputToken,
                              IERC20TokenV06 outputToken,
                              uint256 inputTokenAmount,
                              uint256 minOutputTokenAmount,
                              Transformation[] memory transformations
                          )
                              public
                              override
                              payable
                              returns (uint256 outputTokenAmount)
                          {
                              return _transformERC20Private(
                                  keccak256(msg.data),
                                  msg.sender,
                                  inputToken,
                                  outputToken,
                                  inputTokenAmount,
                                  minOutputTokenAmount,
                                  transformations
                              );
                          }
                          /// @dev Internal version of `transformERC20()`. Only callable from within.
                          /// @param callDataHash Hash of the ingress calldata.
                          /// @param taker The taker address.
                          /// @param inputToken The token being provided by the taker.
                          ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                          /// @param outputToken The token to be acquired by the taker.
                          ///        `0xeee...` implies ETH.
                          /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                          ///        If set to `uint256(-1)`, the entire spendable balance of the taker
                          ///        will be solt.
                          /// @param minOutputTokenAmount The minimum amount of `outputToken` the taker
                          ///        must receive for the entire transformation to succeed. If set to zero,
                          ///        the minimum output token transfer will not be asserted.
                          /// @param transformations The transformations to execute on the token balance(s)
                          ///        in sequence.
                          /// @return outputTokenAmount The amount of `outputToken` received by the taker.
                          function _transformERC20(
                              bytes32 callDataHash,
                              address payable taker,
                              IERC20TokenV06 inputToken,
                              IERC20TokenV06 outputToken,
                              uint256 inputTokenAmount,
                              uint256 minOutputTokenAmount,
                              Transformation[] memory transformations
                          )
                              public
                              override
                              payable
                              onlySelf
                              returns (uint256 outputTokenAmount)
                          {
                              return _transformERC20Private(
                                  callDataHash,
                                  taker,
                                  inputToken,
                                  outputToken,
                                  inputTokenAmount,
                                  minOutputTokenAmount,
                                  transformations
                              );
                          }
                          /// @dev Private version of `transformERC20()`.
                          /// @param callDataHash Hash of the ingress calldata.
                          /// @param taker The taker address.
                          /// @param inputToken The token being provided by the taker.
                          ///        If `0xeee...`, ETH is implied and should be provided with the call.`
                          /// @param outputToken The token to be acquired by the taker.
                          ///        `0xeee...` implies ETH.
                          /// @param inputTokenAmount The amount of `inputToken` to take from the taker.
                          ///        If set to `uint256(-1)`, the entire spendable balance of the taker
                          ///        will be solt.
                          /// @param minOutputTokenAmount The minimum amount of `outputToken` the taker
                          ///        must receive for the entire transformation to succeed. If set to zero,
                          ///        the minimum output token transfer will not be asserted.
                          /// @param transformations The transformations to execute on the token balance(s)
                          ///        in sequence.
                          /// @return outputTokenAmount The amount of `outputToken` received by the taker.
                          function _transformERC20Private(
                              bytes32 callDataHash,
                              address payable taker,
                              IERC20TokenV06 inputToken,
                              IERC20TokenV06 outputToken,
                              uint256 inputTokenAmount,
                              uint256 minOutputTokenAmount,
                              Transformation[] memory transformations
                          )
                              private
                              returns (uint256 outputTokenAmount)
                          {
                              // If the input token amount is -1, transform the taker's entire
                              // spendable balance.
                              if (inputTokenAmount == uint256(-1)) {
                                  inputTokenAmount = ITokenSpender(address(this))
                                      .getSpendableERC20BalanceOf(inputToken, taker);
                              }
                              TransformERC20PrivateState memory state;
                              state.wallet = getTransformWallet();
                              state.transformerDeployer = getTransformerDeployer();
                              // Remember the initial output token balance of the taker.
                              state.takerOutputTokenBalanceBefore =
                                  LibERC20Transformer.getTokenBalanceOf(outputToken, taker);
                              // Pull input tokens from the taker to the wallet and transfer attached ETH.
                              _transferInputTokensAndAttachedEth(
                                  inputToken,
                                  taker,
                                  address(state.wallet),
                                  inputTokenAmount
                              );
                              // Perform transformations.
                              for (uint256 i = 0; i < transformations.length; ++i) {
                                  _executeTransformation(
                                      state.wallet,
                                      transformations[i],
                                      state.transformerDeployer,
                                      taker,
                                      callDataHash
                                  );
                              }
                              // Compute how much output token has been transferred to the taker.
                              state.takerOutputTokenBalanceAfter =
                                  LibERC20Transformer.getTokenBalanceOf(outputToken, taker);
                              if (state.takerOutputTokenBalanceAfter > state.takerOutputTokenBalanceBefore) {
                                  outputTokenAmount = state.takerOutputTokenBalanceAfter.safeSub(
                                      state.takerOutputTokenBalanceBefore
                                  );
                              } else if (state.takerOutputTokenBalanceAfter < state.takerOutputTokenBalanceBefore) {
                                  LibTransformERC20RichErrors.NegativeTransformERC20OutputError(
                                      address(outputToken),
                                      state.takerOutputTokenBalanceBefore - state.takerOutputTokenBalanceAfter
                                  ).rrevert();
                              }
                              // Ensure enough output token has been sent to the taker.
                              if (outputTokenAmount < minOutputTokenAmount) {
                                  LibTransformERC20RichErrors.IncompleteTransformERC20Error(
                                      address(outputToken),
                                      outputTokenAmount,
                                      minOutputTokenAmount
                                  ).rrevert();
                              }
                              // Emit an event.
                              emit TransformedERC20(
                                  taker,
                                  address(inputToken),
                                  address(outputToken),
                                  inputTokenAmount,
                                  outputTokenAmount
                              );
                          }
                          /// @dev Return the current wallet instance that will serve as the execution
                          ///      context for transformations.
                          /// @return wallet The wallet instance.
                          function getTransformWallet()
                              public
                              override
                              view
                              returns (IFlashWallet wallet)
                          {
                              return LibTransformERC20Storage.getStorage().wallet;
                          }
                          /// @dev Transfer input tokens from the taker and any attached ETH to `to`
                          /// @param inputToken The token to pull from the taker.
                          /// @param from The from (taker) address.
                          /// @param to The recipient of tokens and ETH.
                          /// @param amount Amount of `inputToken` tokens to transfer.
                          function _transferInputTokensAndAttachedEth(
                              IERC20TokenV06 inputToken,
                              address from,
                              address payable to,
                              uint256 amount
                          )
                              private
                          {
                              // Transfer any attached ETH.
                              if (msg.value != 0) {
                                  to.transfer(msg.value);
                              }
                              // Transfer input tokens.
                              if (!LibERC20Transformer.isTokenETH(inputToken)) {
                                  // Token is not ETH, so pull ERC20 tokens.
                                  ITokenSpender(address(this))._spendERC20Tokens(
                                      inputToken,
                                      from,
                                      to,
                                      amount
                                  );
                              } else if (msg.value < amount) {
                                   // Token is ETH, so the caller must attach enough ETH to the call.
                                  LibTransformERC20RichErrors.InsufficientEthAttachedError(
                                      msg.value,
                                      amount
                                  ).rrevert();
                              }
                          }
                          /// @dev Executs a transformer in the context of `wallet`.
                          /// @param wallet The wallet instance.
                          /// @param transformation The transformation.
                          /// @param transformerDeployer The address of the transformer deployer.
                          /// @param taker The taker address.
                          /// @param callDataHash Hash of the calldata.
                          function _executeTransformation(
                              IFlashWallet wallet,
                              Transformation memory transformation,
                              address transformerDeployer,
                              address payable taker,
                              bytes32 callDataHash
                          )
                              private
                          {
                              // Derive the transformer address from the deployment nonce.
                              address payable transformer = LibERC20Transformer.getDeployedAddress(
                                  transformerDeployer,
                                  transformation.deploymentNonce
                              );
                              // Call `transformer.transform()` as the wallet.
                              bytes memory resultData = wallet.executeDelegateCall(
                                  // The call target.
                                  transformer,
                                  // Call data.
                                  abi.encodeWithSelector(
                                      IERC20Transformer.transform.selector,
                                      callDataHash,
                                      taker,
                                      transformation.data
                                  )
                              );
                              // Ensure the transformer returned the magic bytes.
                              if (resultData.length != 32 ||
                                  abi.decode(resultData, (bytes4)) != LibERC20Transformer.TRANSFORMER_SUCCESS
                              ) {
                                  LibTransformERC20RichErrors.TransformerFailedError(
                                      transformer,
                                      transformation.data,
                                      resultData
                                  ).rrevert();
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./LibStorage.sol";
                      import "../external/IFlashWallet.sol";
                      /// @dev Storage helpers for the `TokenSpender` feature.
                      library LibTransformERC20Storage {
                          /// @dev Storage bucket for this feature.
                          struct Storage {
                              // The current wallet instance.
                              IFlashWallet wallet;
                              // The transformer deployer address.
                              address transformerDeployer;
                          }
                          /// @dev Get the storage bucket for this contract.
                          function getStorage() internal pure returns (Storage storage stor) {
                              uint256 storageSlot = LibStorage.getStorageSlot(
                                  LibStorage.StorageId.TransformERC20
                              );
                              // Dip into assembly to change the slot pointed to by the local
                              // variable `stor`.
                              // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                              assembly { stor_slot := storageSlot }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
                      library LibERC20Transformer {
                          using LibERC20TokenV06 for IERC20TokenV06;
                          /// @dev ETH pseudo-token address.
                          address constant internal ETH_TOKEN_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
                          /// @dev Return value indicating success in `IERC20Transformer.transform()`.
                          ///      This is just `keccak256('TRANSFORMER_SUCCESS')`.
                          bytes4 constant internal TRANSFORMER_SUCCESS = 0x13c9929e;
                          /// @dev Transfer ERC20 tokens and ETH.
                          /// @param token An ERC20 or the ETH pseudo-token address (`ETH_TOKEN_ADDRESS`).
                          /// @param to The recipient.
                          /// @param amount The transfer amount.
                          function transformerTransfer(
                              IERC20TokenV06 token,
                              address payable to,
                              uint256 amount
                          )
                              internal
                          {
                              if (isTokenETH(token)) {
                                  to.transfer(amount);
                              } else {
                                  token.compatTransfer(to, amount);
                              }
                          }
                          /// @dev Check if a token is the ETH pseudo-token.
                          /// @param token The token to check.
                          /// @return isETH `true` if the token is the ETH pseudo-token.
                          function isTokenETH(IERC20TokenV06 token)
                              internal
                              pure
                              returns (bool isETH)
                          {
                              return address(token) == ETH_TOKEN_ADDRESS;
                          }
                          /// @dev Check the balance of an ERC20 token or ETH.
                          /// @param token An ERC20 or the ETH pseudo-token address (`ETH_TOKEN_ADDRESS`).
                          /// @param owner Holder of the tokens.
                          /// @return tokenBalance The balance of `owner`.
                          function getTokenBalanceOf(IERC20TokenV06 token, address owner)
                              internal
                              view
                              returns (uint256 tokenBalance)
                          {
                              if (isTokenETH(token)) {
                                  return owner.balance;
                              }
                              return token.balanceOf(owner);
                          }
                          /// @dev RLP-encode a 32-bit or less account nonce.
                          /// @param nonce A positive integer in the range 0 <= nonce < 2^32.
                          /// @return rlpNonce The RLP encoding.
                          function rlpEncodeNonce(uint32 nonce)
                              internal
                              pure
                              returns (bytes memory rlpNonce)
                          {
                              // See https://github.com/ethereum/wiki/wiki/RLP for RLP encoding rules.
                              if (nonce == 0) {
                                  rlpNonce = new bytes(1);
                                  rlpNonce[0] = 0x80;
                              } else if (nonce < 0x80) {
                                  rlpNonce = new bytes(1);
                                  rlpNonce[0] = byte(uint8(nonce));
                              } else if (nonce <= 0xFF) {
                                  rlpNonce = new bytes(2);
                                  rlpNonce[0] = 0x81;
                                  rlpNonce[1] = byte(uint8(nonce));
                              } else if (nonce <= 0xFFFF) {
                                  rlpNonce = new bytes(3);
                                  rlpNonce[0] = 0x82;
                                  rlpNonce[1] = byte(uint8((nonce & 0xFF00) >> 8));
                                  rlpNonce[2] = byte(uint8(nonce));
                              } else if (nonce <= 0xFFFFFF) {
                                  rlpNonce = new bytes(4);
                                  rlpNonce[0] = 0x83;
                                  rlpNonce[1] = byte(uint8((nonce & 0xFF0000) >> 16));
                                  rlpNonce[2] = byte(uint8((nonce & 0xFF00) >> 8));
                                  rlpNonce[3] = byte(uint8(nonce));
                              } else {
                                  rlpNonce = new bytes(5);
                                  rlpNonce[0] = 0x84;
                                  rlpNonce[1] = byte(uint8((nonce & 0xFF000000) >> 24));
                                  rlpNonce[2] = byte(uint8((nonce & 0xFF0000) >> 16));
                                  rlpNonce[3] = byte(uint8((nonce & 0xFF00) >> 8));
                                  rlpNonce[4] = byte(uint8(nonce));
                              }
                          }
                          /// @dev Compute the expected deployment address by `deployer` at
                          ///      the nonce given by `deploymentNonce`.
                          /// @param deployer The address of the deployer.
                          /// @param deploymentNonce The nonce that the deployer had when deploying
                          ///        a contract.
                          /// @return deploymentAddress The deployment address.
                          function getDeployedAddress(address deployer, uint32 deploymentNonce)
                              internal
                              pure
                              returns (address payable deploymentAddress)
                          {
                              // The address of if a deployed contract is the lower 20 bytes of the
                              // hash of the RLP-encoded deployer's account address + account nonce.
                              // See: https://ethereum.stackexchange.com/questions/760/how-is-the-address-of-an-ethereum-contract-computed
                              bytes memory rlpNonce = rlpEncodeNonce(deploymentNonce);
                              return address(uint160(uint256(keccak256(abi.encodePacked(
                                  byte(uint8(0xC0 + 21 + rlpNonce.length)),
                                  byte(uint8(0x80 + 20)),
                                  deployer,
                                  rlpNonce
                              )))));
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../ZeroEx.sol";
                      import "../features/IOwnable.sol";
                      import "../features/TokenSpender.sol";
                      import "../features/TransformERC20.sol";
                      import "../external/AllowanceTarget.sol";
                      import "./InitialMigration.sol";
                      /// @dev A contract for deploying and configuring the full ZeroEx contract.
                      contract FullMigration {
                          // solhint-disable no-empty-blocks,indent
                          /// @dev Features to add the the proxy contract.
                          struct Features {
                              SimpleFunctionRegistry registry;
                              Ownable ownable;
                              TokenSpender tokenSpender;
                              TransformERC20 transformERC20;
                          }
                          /// @dev Parameters needed to initialize features.
                          struct MigrateOpts {
                              address transformerDeployer;
                          }
                          /// @dev The allowed caller of `deploy()`.
                          address public immutable deployer;
                          /// @dev The initial migration contract.
                          InitialMigration private _initialMigration;
                          /// @dev Instantiate this contract and set the allowed caller of `deploy()`
                          ///      to `deployer`.
                          /// @param deployer_ The allowed caller of `deploy()`.
                          constructor(address payable deployer_)
                              public
                          {
                              deployer = deployer_;
                              // Create an initial migration contract with this contract set to the
                              // allowed deployer.
                              _initialMigration = new InitialMigration(address(this));
                          }
                          /// @dev Deploy the `ZeroEx` contract with the full feature set,
                          ///      transfer ownership to `owner`, then self-destruct.
                          /// @param owner The owner of the contract.
                          /// @param features Features to add to the proxy.
                          /// @return zeroEx The deployed and configured `ZeroEx` contract.
                          /// @param migrateOpts Parameters needed to initialize features.
                          function deploy(
                              address payable owner,
                              Features memory features,
                              MigrateOpts memory migrateOpts
                          )
                              public
                              returns (ZeroEx zeroEx)
                          {
                              require(msg.sender == deployer, "FullMigration/INVALID_SENDER");
                              // Perform the initial migration with the owner set to this contract.
                              zeroEx = _initialMigration.deploy(
                                  address(uint160(address(this))),
                                  InitialMigration.BootstrapFeatures({
                                      registry: features.registry,
                                      ownable: features.ownable
                                  })
                              );
                              // Add features.
                              _addFeatures(zeroEx, owner, features, migrateOpts);
                              // Transfer ownership to the real owner.
                              IOwnable(address(zeroEx)).transferOwnership(owner);
                              // Self-destruct.
                              this.die(owner);
                          }
                          /// @dev Destroy this contract. Only callable from ourselves (from `deploy()`).
                          /// @param ethRecipient Receiver of any ETH in this contract.
                          function die(address payable ethRecipient)
                              external
                              virtual
                          {
                              require(msg.sender == address(this), "FullMigration/INVALID_SENDER");
                              // This contract should not hold any funds but we send
                              // them to the ethRecipient just in case.
                              selfdestruct(ethRecipient);
                          }
                          /// @dev Deploy and register features to the ZeroEx contract.
                          /// @param zeroEx The bootstrapped ZeroEx contract.
                          /// @param owner The ultimate owner of the ZeroEx contract.
                          /// @param features Features to add to the proxy.
                          /// @param migrateOpts Parameters needed to initialize features.
                          function _addFeatures(
                              ZeroEx zeroEx,
                              address owner,
                              Features memory features,
                              MigrateOpts memory migrateOpts
                          )
                              private
                          {
                              IOwnable ownable = IOwnable(address(zeroEx));
                              // TokenSpender
                              {
                                  // Create the allowance target.
                                  AllowanceTarget allowanceTarget = new AllowanceTarget();
                                  // Let the ZeroEx contract use the allowance target.
                                  allowanceTarget.addAuthorizedAddress(address(zeroEx));
                                  // Transfer ownership of the allowance target to the (real) owner.
                                  allowanceTarget.transferOwnership(owner);
                                  // Register the feature.
                                  ownable.migrate(
                                      address(features.tokenSpender),
                                      abi.encodeWithSelector(
                                          TokenSpender.migrate.selector,
                                          allowanceTarget
                                      ),
                                      address(this)
                                  );
                              }
                              // TransformERC20
                              {
                                  // Register the feature.
                                  ownable.migrate(
                                      address(features.transformERC20),
                                      abi.encodeWithSelector(
                                          TransformERC20.migrate.selector,
                                          migrateOpts.transformerDeployer
                                      ),
                                      address(this)
                                  );
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../ZeroEx.sol";
                      import "../features/IBootstrap.sol";
                      import "../features/SimpleFunctionRegistry.sol";
                      import "../features/Ownable.sol";
                      import "./LibBootstrap.sol";
                      /// @dev A contract for deploying and configuring a minimal ZeroEx contract.
                      contract InitialMigration {
                          /// @dev Features to bootstrap into the the proxy contract.
                          struct BootstrapFeatures {
                              SimpleFunctionRegistry registry;
                              Ownable ownable;
                          }
                          /// @dev The allowed caller of `deploy()`. In production, this would be
                          ///      the governor.
                          address public immutable deployer;
                          /// @dev The real address of this contract.
                          address private immutable _implementation;
                          /// @dev Instantiate this contract and set the allowed caller of `deploy()`
                          ///      to `deployer_`.
                          /// @param deployer_ The allowed caller of `deploy()`.
                          constructor(address deployer_) public {
                              deployer = deployer_;
                              _implementation = address(this);
                          }
                          /// @dev Deploy the `ZeroEx` contract with the minimum feature set,
                          ///      transfers ownership to `owner`, then self-destructs.
                          ///      Only callable by `deployer` set in the contstructor.
                          /// @param owner The owner of the contract.
                          /// @param features Features to bootstrap into the proxy.
                          /// @return zeroEx The deployed and configured `ZeroEx` contract.
                          function deploy(address payable owner, BootstrapFeatures memory features)
                              public
                              virtual
                              returns (ZeroEx zeroEx)
                          {
                              // Must be called by the allowed deployer.
                              require(msg.sender == deployer, "InitialMigration/INVALID_SENDER");
                              // Deploy the ZeroEx contract, setting ourselves as the bootstrapper.
                              zeroEx = new ZeroEx();
                              // Bootstrap the initial feature set.
                              IBootstrap(address(zeroEx)).bootstrap(
                                  address(this),
                                  abi.encodeWithSelector(this.bootstrap.selector, owner, features)
                              );
                              // Self-destruct. This contract should not hold any funds but we send
                              // them to the owner just in case.
                              this.die(owner);
                          }
                          /// @dev Sets up the initial state of the `ZeroEx` contract.
                          ///      The `ZeroEx` contract will delegatecall into this function.
                          /// @param owner The new owner of the ZeroEx contract.
                          /// @param features Features to bootstrap into the proxy.
                          /// @return success Magic bytes if successful.
                          function bootstrap(address owner, BootstrapFeatures memory features)
                              public
                              virtual
                              returns (bytes4 success)
                          {
                              // Deploy and migrate the initial features.
                              // Order matters here.
                              // Initialize Registry.
                              LibBootstrap.delegatecallBootstrapFunction(
                                  address(features.registry),
                                  abi.encodeWithSelector(
                                      SimpleFunctionRegistry.bootstrap.selector
                                  )
                              );
                              // Initialize Ownable.
                              LibBootstrap.delegatecallBootstrapFunction(
                                  address(features.ownable),
                                  abi.encodeWithSelector(
                                      Ownable.bootstrap.selector
                                  )
                              );
                              // De-register `SimpleFunctionRegistry._extendSelf`.
                              SimpleFunctionRegistry(address(this)).rollback(
                                  SimpleFunctionRegistry._extendSelf.selector,
                                  address(0)
                              );
                              // Transfer ownership to the real owner.
                              Ownable(address(this)).transferOwnership(owner);
                              success = LibBootstrap.BOOTSTRAP_SUCCESS;
                          }
                          /// @dev Self-destructs this contract. Only callable by this contract.
                          /// @param ethRecipient Who to transfer outstanding ETH to.
                          function die(address payable ethRecipient) public virtual {
                              require(msg.sender == _implementation, "InitialMigration/INVALID_SENDER");
                              selfdestruct(ethRecipient);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
                      import "../errors/LibTransformERC20RichErrors.sol";
                      import "./Transformer.sol";
                      import "./LibERC20Transformer.sol";
                      /// @dev A transformer that transfers tokens to arbitrary addresses.
                      contract AffiliateFeeTransformer is
                          Transformer
                      {
                          // solhint-disable no-empty-blocks
                          using LibRichErrorsV06 for bytes;
                          using LibSafeMathV06 for uint256;
                          using LibERC20Transformer for IERC20TokenV06;
                          /// @dev Information for a single fee.
                          struct TokenFee {
                              // The token to transfer to `recipient`.
                              IERC20TokenV06 token;
                              // Amount of each `token` to transfer to `recipient`.
                              // If `amount == uint256(-1)`, the entire balance of `token` will be
                              // transferred.
                              uint256 amount;
                              // Recipient of `token`.
                              address payable recipient;
                          }
                          uint256 private constant MAX_UINT256 = uint256(-1);
                          /// @dev Create this contract.
                          constructor()
                              public
                              Transformer()
                          {}
                          /// @dev Transfers tokens to recipients.
                          /// @param data ABI-encoded `TokenFee[]`, indicating which tokens to transfer.
                          /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                          function transform(
                              bytes32, // callDataHash,
                              address payable, // taker,
                              bytes calldata data
                          )
                              external
                              override
                              returns (bytes4 success)
                          {
                              TokenFee[] memory fees = abi.decode(data, (TokenFee[]));
                              // Transfer tokens to recipients.
                              for (uint256 i = 0; i < fees.length; ++i) {
                                  uint256 amount = fees[i].amount;
                                  if (amount == MAX_UINT256) {
                                      amount = LibERC20Transformer.getTokenBalanceOf(fees[i].token, address(this));
                                  }
                                  if (amount != 0) {
                                      fees[i].token.transformerTransfer(fees[i].recipient, amount);
                                  }
                              }
                              return LibERC20Transformer.TRANSFORMER_SUCCESS;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../errors/LibTransformERC20RichErrors.sol";
                      import "./IERC20Transformer.sol";
                      /// @dev Abstract base class for transformers.
                      abstract contract Transformer is
                          IERC20Transformer
                      {
                          using LibRichErrorsV06 for bytes;
                          /// @dev The address of the deployer.
                          address public immutable deployer;
                          /// @dev The original address of this contract.
                          address private immutable _implementation;
                          /// @dev Create this contract.
                          constructor() public {
                              deployer = msg.sender;
                              _implementation = address(this);
                          }
                          /// @dev Destruct this contract. Only callable by the deployer and will not
                          ///      succeed in the context of a delegatecall (from another contract).
                          /// @param ethRecipient The recipient of ETH held in this contract.
                          function die(address payable ethRecipient)
                              external
                              virtual
                          {
                              // Only the deployer can call this.
                              if (msg.sender != deployer) {
                                  LibTransformERC20RichErrors
                                      .OnlyCallableByDeployerError(msg.sender, deployer)
                                      .rrevert();
                              }
                              // Must be executing our own context.
                              if (address(this) != _implementation) {
                                  LibTransformERC20RichErrors
                                      .InvalidExecutionContextError(address(this), _implementation)
                                      .rrevert();
                              }
                              selfdestruct(ethRecipient);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibMathV06.sol";
                      import "../errors/LibTransformERC20RichErrors.sol";
                      import "../vendor/v3/IExchange.sol";
                      import "./Transformer.sol";
                      import "./LibERC20Transformer.sol";
                      /// @dev A transformer that fills an ERC20 market sell/buy quote.
                      contract FillQuoteTransformer is
                          Transformer
                      {
                          using LibERC20TokenV06 for IERC20TokenV06;
                          using LibERC20Transformer for IERC20TokenV06;
                          using LibSafeMathV06 for uint256;
                          using LibRichErrorsV06 for bytes;
                          /// @dev Whether we are performing a market sell or buy.
                          enum Side {
                              Sell,
                              Buy
                          }
                          /// @dev Transform data to ABI-encode and pass into `transform()`.
                          struct TransformData {
                              // Whether we aer performing a market sell or buy.
                              Side side;
                              // The token being sold.
                              // This should be an actual token, not the ETH pseudo-token.
                              IERC20TokenV06 sellToken;
                              // The token being bought.
                              // This should be an actual token, not the ETH pseudo-token.
                              IERC20TokenV06 buyToken;
                              // The orders to fill.
                              IExchange.Order[] orders;
                              // Signatures for each respective order in `orders`.
                              bytes[] signatures;
                              // Maximum fill amount for each order. This may be shorter than the
                              // number of orders, where missing entries will be treated as `uint256(-1)`.
                              // For sells, this will be the maximum sell amount (taker asset).
                              // For buys, this will be the maximum buy amount (maker asset).
                              uint256[] maxOrderFillAmounts;
                              // Amount of `sellToken` to sell or `buyToken` to buy.
                              // For sells, this may be `uint256(-1)` to sell the entire balance of
                              // `sellToken`.
                              uint256 fillAmount;
                          }
                          /// @dev Results of a call to `_fillOrder()`.
                          struct FillOrderResults {
                              // The amount of taker tokens sold, according to balance checks.
                              uint256 takerTokenSoldAmount;
                              // The amount of maker tokens sold, according to balance checks.
                              uint256 makerTokenBoughtAmount;
                              // The amount of protocol fee paid.
                              uint256 protocolFeePaid;
                          }
                          /// @dev The Exchange ERC20Proxy ID.
                          bytes4 private constant ERC20_ASSET_PROXY_ID = 0xf47261b0;
                          /// @dev Maximum uint256 value.
                          uint256 private constant MAX_UINT256 = uint256(-1);
                          /// @dev The Exchange contract.
                          IExchange public immutable exchange;
                          /// @dev The ERC20Proxy address.
                          address public immutable erc20Proxy;
                          /// @dev Create this contract.
                          /// @param exchange_ The Exchange V3 instance.
                          constructor(IExchange exchange_)
                              public
                              Transformer()
                          {
                              exchange = exchange_;
                              erc20Proxy = exchange_.getAssetProxy(ERC20_ASSET_PROXY_ID);
                          }
                          /// @dev Sell this contract's entire balance of of `sellToken` in exchange
                          ///      for `buyToken` by filling `orders`. Protocol fees should be attached
                          ///      to this call. `buyToken` and excess ETH will be transferred back to the caller.
                          /// @param data_ ABI-encoded `TransformData`.
                          /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                          function transform(
                              bytes32, // callDataHash,
                              address payable, // taker,
                              bytes calldata data_
                          )
                              external
                              override
                              returns (bytes4 success)
                          {
                              TransformData memory data = abi.decode(data_, (TransformData));
                              // Validate data fields.
                              if (data.sellToken.isTokenETH() || data.buyToken.isTokenETH()) {
                                  LibTransformERC20RichErrors.InvalidTransformDataError(
                                      LibTransformERC20RichErrors.InvalidTransformDataErrorCode.INVALID_TOKENS,
                                      data_
                                  ).rrevert();
                              }
                              if (data.orders.length != data.signatures.length) {
                                  LibTransformERC20RichErrors.InvalidTransformDataError(
                                      LibTransformERC20RichErrors.InvalidTransformDataErrorCode.INVALID_ARRAY_LENGTH,
                                      data_
                                  ).rrevert();
                              }
                              if (data.side == Side.Sell && data.fillAmount == MAX_UINT256) {
                                  // If `sellAmount == -1 then we are selling
                                  // the entire balance of `sellToken`. This is useful in cases where
                                  // the exact sell amount is not exactly known in advance, like when
                                  // unwrapping Chai/cUSDC/cDAI.
                                  data.fillAmount = data.sellToken.getTokenBalanceOf(address(this));
                              }
                              // Approve the ERC20 proxy to spend `sellToken`.
                              data.sellToken.approveIfBelow(erc20Proxy, data.fillAmount);
                              // Fill the orders.
                              uint256 singleProtocolFee = exchange.protocolFeeMultiplier().safeMul(tx.gasprice);
                              uint256 ethRemaining = address(this).balance;
                              uint256 boughtAmount = 0;
                              uint256 soldAmount = 0;
                              for (uint256 i = 0; i < data.orders.length; ++i) {
                                  // Check if we've hit our targets.
                                  if (data.side == Side.Sell) {
                                      // Market sell check.
                                      if (soldAmount >= data.fillAmount) {
                                          break;
                                      }
                                  } else {
                                      // Market buy check.
                                      if (boughtAmount >= data.fillAmount) {
                                          break;
                                      }
                                  }
                                  // Ensure we have enough ETH to cover the protocol fee.
                                  if (ethRemaining < singleProtocolFee) {
                                      LibTransformERC20RichErrors
                                          .InsufficientProtocolFeeError(ethRemaining, singleProtocolFee)
                                          .rrevert();
                                  }
                                  // Fill the order.
                                  FillOrderResults memory results;
                                  if (data.side == Side.Sell) {
                                      // Market sell.
                                      results = _sellToOrder(
                                          data.buyToken,
                                          data.sellToken,
                                          data.orders[i],
                                          data.signatures[i],
                                          data.fillAmount.safeSub(soldAmount).min256(
                                              data.maxOrderFillAmounts.length > i
                                              ? data.maxOrderFillAmounts[i]
                                              : MAX_UINT256
                                          ),
                                          singleProtocolFee
                                      );
                                  } else {
                                      // Market buy.
                                      results = _buyFromOrder(
                                          data.buyToken,
                                          data.sellToken,
                                          data.orders[i],
                                          data.signatures[i],
                                          data.fillAmount.safeSub(boughtAmount).min256(
                                              data.maxOrderFillAmounts.length > i
                                              ? data.maxOrderFillAmounts[i]
                                              : MAX_UINT256
                                          ),
                                          singleProtocolFee
                                      );
                                  }
                                  // Accumulate totals.
                                  soldAmount = soldAmount.safeAdd(results.takerTokenSoldAmount);
                                  boughtAmount = boughtAmount.safeAdd(results.makerTokenBoughtAmount);
                                  ethRemaining = ethRemaining.safeSub(results.protocolFeePaid);
                              }
                              // Ensure we hit our targets.
                              if (data.side == Side.Sell) {
                                  // Market sell check.
                                  if (soldAmount < data.fillAmount) {
                                      LibTransformERC20RichErrors
                                          .IncompleteFillSellQuoteError(
                                              address(data.sellToken),
                                              soldAmount,
                                              data.fillAmount
                                          ).rrevert();
                                  }
                              } else {
                                  // Market buy check.
                                  if (boughtAmount < data.fillAmount) {
                                      LibTransformERC20RichErrors
                                          .IncompleteFillBuyQuoteError(
                                              address(data.buyToken),
                                              boughtAmount,
                                              data.fillAmount
                                          ).rrevert();
                                  }
                              }
                              return LibERC20Transformer.TRANSFORMER_SUCCESS;
                          }
                          /// @dev Try to sell up to `sellAmount` from an order.
                          /// @param makerToken The maker/buy token.
                          /// @param takerToken The taker/sell token.
                          /// @param order The order to fill.
                          /// @param signature The signature for `order`.
                          /// @param sellAmount Amount of taker token to sell.
                          /// @param protocolFee The protocol fee needed to fill `order`.
                          function _sellToOrder(
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              IExchange.Order memory order,
                              bytes memory signature,
                              uint256 sellAmount,
                              uint256 protocolFee
                          )
                              private
                              returns (FillOrderResults memory results)
                          {
                              IERC20TokenV06 takerFeeToken =
                                  _getTokenFromERC20AssetData(order.takerFeeAssetData);
                              uint256 takerTokenFillAmount = sellAmount;
                              if (order.takerFee != 0) {
                                  if (takerFeeToken == makerToken) {
                                      // Taker fee is payable in the maker token, so we need to
                                      // approve the proxy to spend the maker token.
                                      // It isn't worth computing the actual taker fee
                                      // since `approveIfBelow()` will set the allowance to infinite. We
                                      // just need a reasonable upper bound to avoid unnecessarily re-approving.
                                      takerFeeToken.approveIfBelow(erc20Proxy, order.takerFee);
                                  } else if (takerFeeToken == takerToken){
                                      // Taker fee is payable in the taker token, so we need to
                                      // reduce the fill amount to cover the fee.
                                      // takerTokenFillAmount' =
                                      //   (takerTokenFillAmount * order.takerAssetAmount) /
                                      //   (order.takerAssetAmount + order.takerFee)
                                      takerTokenFillAmount = LibMathV06.getPartialAmountCeil(
                                          order.takerAssetAmount,
                                          order.takerAssetAmount.safeAdd(order.takerFee),
                                          sellAmount
                                      );
                                  } else {
                                      //  Only support taker or maker asset denominated taker fees.
                                      LibTransformERC20RichErrors.InvalidTakerFeeTokenError(
                                          address(takerFeeToken)
                                      ).rrevert();
                                  }
                              }
                              // Clamp fill amount to order size.
                              takerTokenFillAmount = LibSafeMathV06.min256(
                                  takerTokenFillAmount,
                                  order.takerAssetAmount
                              );
                              // Perform the fill.
                              return _fillOrder(
                                  order,
                                  signature,
                                  takerTokenFillAmount,
                                  protocolFee,
                                  makerToken,
                                  takerFeeToken == takerToken
                              );
                          }
                          /// @dev Try to buy up to `buyAmount` from an order.
                          /// @param makerToken The maker/buy token.
                          /// @param takerToken The taker/sell token.
                          /// @param order The order to fill.
                          /// @param signature The signature for `order`.
                          /// @param buyAmount Amount of maker token to buy.
                          /// @param protocolFee The protocol fee needed to fill `order`.
                          function _buyFromOrder(
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              IExchange.Order memory order,
                              bytes memory signature,
                              uint256 buyAmount,
                              uint256 protocolFee
                          )
                              private
                              returns (FillOrderResults memory results)
                          {
                              IERC20TokenV06 takerFeeToken =
                                  _getTokenFromERC20AssetData(order.takerFeeAssetData);
                              // Compute the default taker token fill amount.
                              uint256 takerTokenFillAmount = LibMathV06.getPartialAmountCeil(
                                  buyAmount,
                                  order.makerAssetAmount,
                                  order.takerAssetAmount
                              );
                              if (order.takerFee != 0) {
                                  if (takerFeeToken == makerToken) {
                                      // Taker fee is payable in the maker token.
                                      // Adjust the taker token fill amount to account for maker
                                      // tokens being lost to the taker fee.
                                      // takerTokenFillAmount' =
                                      //  (order.takerAssetAmount * buyAmount) /
                                      //  (order.makerAssetAmount - order.takerFee)
                                      takerTokenFillAmount = LibMathV06.getPartialAmountCeil(
                                          buyAmount,
                                          order.makerAssetAmount.safeSub(order.takerFee),
                                          order.takerAssetAmount
                                      );
                                      // Approve the proxy to spend the maker token.
                                      // It isn't worth computing the actual taker fee
                                      // since `approveIfBelow()` will set the allowance to infinite. We
                                      // just need a reasonable upper bound to avoid unnecessarily re-approving.
                                      takerFeeToken.approveIfBelow(erc20Proxy, order.takerFee);
                                  } else if (takerFeeToken != takerToken) {
                                      //  Only support taker or maker asset denominated taker fees.
                                      LibTransformERC20RichErrors.InvalidTakerFeeTokenError(
                                          address(takerFeeToken)
                                      ).rrevert();
                                  }
                              }
                              // Clamp to order size.
                              takerTokenFillAmount = LibSafeMathV06.min256(
                                  order.takerAssetAmount,
                                  takerTokenFillAmount
                              );
                              // Perform the fill.
                              return _fillOrder(
                                  order,
                                  signature,
                                  takerTokenFillAmount,
                                  protocolFee,
                                  makerToken,
                                  takerFeeToken == takerToken
                              );
                          }
                          /// @dev Attempt to fill an order. If the fill reverts, the revert will be
                          ///      swallowed and `results` will be zeroed out.
                          /// @param order The order to fill.
                          /// @param signature The order signature.
                          /// @param takerAssetFillAmount How much taker asset to fill.
                          /// @param protocolFee The protocol fee needed to fill this order.
                          /// @param makerToken The maker token.
                          /// @param isTakerFeeInTakerToken Whether the taker fee token is the same as the
                          ///        taker token.
                          function _fillOrder(
                              IExchange.Order memory order,
                              bytes memory signature,
                              uint256 takerAssetFillAmount,
                              uint256 protocolFee,
                              IERC20TokenV06 makerToken,
                              bool isTakerFeeInTakerToken
                          )
                              private
                              returns (FillOrderResults memory results)
                          {
                              // Track changes in the maker token balance.
                              uint256 initialMakerTokenBalance = makerToken.balanceOf(address(this));
                              try
                                  exchange.fillOrder
                                      {value: protocolFee}
                                      (order, takerAssetFillAmount, signature)
                                  returns (IExchange.FillResults memory fillResults)
                              {
                                  // Update maker quantity based on changes in token balances.
                                  results.makerTokenBoughtAmount = makerToken.balanceOf(address(this))
                                      .safeSub(initialMakerTokenBalance);
                                  // We can trust the other fill result quantities.
                                  results.protocolFeePaid = fillResults.protocolFeePaid;
                                  results.takerTokenSoldAmount = fillResults.takerAssetFilledAmount;
                                  // If the taker fee is payable in the taker asset, include the
                                  // taker fee in the total amount sold.
                                  if (isTakerFeeInTakerToken) {
                                      results.takerTokenSoldAmount =
                                          results.takerTokenSoldAmount.safeAdd(fillResults.takerFeePaid);
                                  }
                              } catch (bytes memory) {
                                  // Swallow failures, leaving all results as zero.
                              }
                          }
                          /// @dev Extract the token from plain ERC20 asset data.
                          ///      If the asset-data is empty, a zero token address will be returned.
                          /// @param assetData The order asset data.
                          function _getTokenFromERC20AssetData(bytes memory assetData)
                              private
                              pure
                              returns (IERC20TokenV06 token)
                          {
                              if (assetData.length == 0) {
                                  return IERC20TokenV06(address(0));
                              }
                              if (assetData.length != 36 ||
                                  LibBytesV06.readBytes4(assetData, 0) != ERC20_ASSET_PROXY_ID)
                              {
                                  LibTransformERC20RichErrors
                                      .InvalidERC20AssetDataError(assetData)
                                      .rrevert();
                              }
                              return IERC20TokenV06(LibBytesV06.readAddress(assetData, 16));
                          }
                      }
                      /*
                        Copyright 2019 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./LibSafeMathV06.sol";
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibMathRichErrorsV06.sol";
                      library LibMathV06 {
                          using LibSafeMathV06 for uint256;
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          ///      Reverts if rounding error is >= 0.1%
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded down.
                          function safeGetPartialAmountFloor(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              if (isRoundingErrorFloor(
                                      numerator,
                                      denominator,
                                      target
                              )) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.RoundingError(
                                      numerator,
                                      denominator,
                                      target
                                  ));
                              }
                              partialAmount = numerator.safeMul(target).safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          ///      Reverts if rounding error is >= 0.1%
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded up.
                          function safeGetPartialAmountCeil(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              if (isRoundingErrorCeil(
                                      numerator,
                                      denominator,
                                      target
                              )) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.RoundingError(
                                      numerator,
                                      denominator,
                                      target
                                  ));
                              }
                              // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
                              //       ceil(a / b) = floor((a + b - 1) / b)
                              // To implement `ceil(a / b)` using safeDiv.
                              partialAmount = numerator.safeMul(target)
                                  .safeAdd(denominator.safeSub(1))
                                  .safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded down.
                          function getPartialAmountFloor(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              partialAmount = numerator.safeMul(target).safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded up.
                          function getPartialAmountCeil(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
                              //       ceil(a / b) = floor((a + b - 1) / b)
                              // To implement `ceil(a / b)` using safeDiv.
                              partialAmount = numerator.safeMul(target)
                                  .safeAdd(denominator.safeSub(1))
                                  .safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Checks if rounding error >= 0.1% when rounding down.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to multiply with numerator/denominator.
                          /// @return isError Rounding error is present.
                          function isRoundingErrorFloor(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (bool isError)
                          {
                              if (denominator == 0) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.DivisionByZeroError());
                              }
                              // The absolute rounding error is the difference between the rounded
                              // value and the ideal value. The relative rounding error is the
                              // absolute rounding error divided by the absolute value of the
                              // ideal value. This is undefined when the ideal value is zero.
                              //
                              // The ideal value is `numerator * target / denominator`.
                              // Let's call `numerator * target % denominator` the remainder.
                              // The absolute error is `remainder / denominator`.
                              //
                              // When the ideal value is zero, we require the absolute error to
                              // be zero. Fortunately, this is always the case. The ideal value is
                              // zero iff `numerator == 0` and/or `target == 0`. In this case the
                              // remainder and absolute error are also zero.
                              if (target == 0 || numerator == 0) {
                                  return false;
                              }
                              // Otherwise, we want the relative rounding error to be strictly
                              // less than 0.1%.
                              // The relative error is `remainder / (numerator * target)`.
                              // We want the relative error less than 1 / 1000:
                              //        remainder / (numerator * denominator)  <  1 / 1000
                              // or equivalently:
                              //        1000 * remainder  <  numerator * target
                              // so we have a rounding error iff:
                              //        1000 * remainder  >=  numerator * target
                              uint256 remainder = mulmod(
                                  target,
                                  numerator,
                                  denominator
                              );
                              isError = remainder.safeMul(1000) >= numerator.safeMul(target);
                              return isError;
                          }
                          /// @dev Checks if rounding error >= 0.1% when rounding up.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to multiply with numerator/denominator.
                          /// @return isError Rounding error is present.
                          function isRoundingErrorCeil(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (bool isError)
                          {
                              if (denominator == 0) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.DivisionByZeroError());
                              }
                              // See the comments in `isRoundingError`.
                              if (target == 0 || numerator == 0) {
                                  // When either is zero, the ideal value and rounded value are zero
                                  // and there is no rounding error. (Although the relative error
                                  // is undefined.)
                                  return false;
                              }
                              // Compute remainder as before
                              uint256 remainder = mulmod(
                                  target,
                                  numerator,
                                  denominator
                              );
                              remainder = denominator.safeSub(remainder) % denominator;
                              isError = remainder.safeMul(1000) >= numerator.safeMul(target);
                              return isError;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibMathRichErrorsV06 {
                          // bytes4(keccak256("DivisionByZeroError()"))
                          bytes internal constant DIVISION_BY_ZERO_ERROR =
                              hex"a791837c";
                          // bytes4(keccak256("RoundingError(uint256,uint256,uint256)"))
                          bytes4 internal constant ROUNDING_ERROR_SELECTOR =
                              0x339f3de2;
                          // solhint-disable func-name-mixedcase
                          function DivisionByZeroError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return DIVISION_BY_ZERO_ERROR;
                          }
                          function RoundingError(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  ROUNDING_ERROR_SELECTOR,
                                  numerator,
                                  denominator,
                                  target
                              );
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Interface to the V3 Exchange.
                      interface IExchange {
                          /// @dev V3 Order structure.
                          struct Order {
                              // Address that created the order.
                              address makerAddress;
                              // Address that is allowed to fill the order.
                              // If set to 0, any address is allowed to fill the order.
                              address takerAddress;
                              // Address that will recieve fees when order is filled.
                              address feeRecipientAddress;
                              // Address that is allowed to call Exchange contract methods that affect this order.
                              // If set to 0, any address is allowed to call these methods.
                              address senderAddress;
                              // Amount of makerAsset being offered by maker. Must be greater than 0.
                              uint256 makerAssetAmount;
                              // Amount of takerAsset being bid on by maker. Must be greater than 0.
                              uint256 takerAssetAmount;
                              // Fee paid to feeRecipient by maker when order is filled.
                              uint256 makerFee;
                              // Fee paid to feeRecipient by taker when order is filled.
                              uint256 takerFee;
                              // Timestamp in seconds at which order expires.
                              uint256 expirationTimeSeconds;
                              // Arbitrary number to facilitate uniqueness of the order's hash.
                              uint256 salt;
                              // Encoded data that can be decoded by a specified proxy contract when transferring makerAsset.
                              // The leading bytes4 references the id of the asset proxy.
                              bytes makerAssetData;
                              // Encoded data that can be decoded by a specified proxy contract when transferring takerAsset.
                              // The leading bytes4 references the id of the asset proxy.
                              bytes takerAssetData;
                              // Encoded data that can be decoded by a specified proxy contract when transferring makerFeeAsset.
                              // The leading bytes4 references the id of the asset proxy.
                              bytes makerFeeAssetData;
                              // Encoded data that can be decoded by a specified proxy contract when transferring takerFeeAsset.
                              // The leading bytes4 references the id of the asset proxy.
                              bytes takerFeeAssetData;
                          }
                          /// @dev V3 `fillOrder()` results.`
                          struct FillResults {
                              // Total amount of makerAsset(s) filled.
                              uint256 makerAssetFilledAmount;
                              // Total amount of takerAsset(s) filled.
                              uint256 takerAssetFilledAmount;
                              // Total amount of fees paid by maker(s) to feeRecipient(s).
                              uint256 makerFeePaid;
                              // Total amount of fees paid by taker to feeRecipients(s).
                              uint256 takerFeePaid;
                              // Total amount of fees paid by taker to the staking contract.
                              uint256 protocolFeePaid;
                          }
                          /// @dev Fills the input order.
                          /// @param order Order struct containing order specifications.
                          /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
                          /// @param signature Proof that order has been created by maker.
                          /// @return fillResults Amounts filled and fees paid by maker and taker.
                          function fillOrder(
                              Order calldata order,
                              uint256 takerAssetFillAmount,
                              bytes calldata signature
                          )
                              external
                              payable
                              returns (FillResults memory fillResults);
                          /// @dev Returns the protocolFeeMultiplier
                          /// @return multiplier The multiplier for protocol fees.
                          function protocolFeeMultiplier()
                              external
                              view
                              returns (uint256 multiplier);
                          /// @dev Gets an asset proxy.
                          /// @param assetProxyId Id of the asset proxy.
                          /// @return proxyAddress The asset proxy registered to assetProxyId.
                          ///         Returns 0x0 if no proxy is registered.
                          function getAssetProxy(bytes4 assetProxyId)
                              external
                              view
                              returns (address proxyAddress);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/LibERC20TokenV06.sol";
                      import "../errors/LibTransformERC20RichErrors.sol";
                      import "./Transformer.sol";
                      import "./LibERC20Transformer.sol";
                      /// @dev A transformer that transfers tokens to the taker.
                      contract PayTakerTransformer is
                          Transformer
                      {
                          // solhint-disable no-empty-blocks
                          using LibRichErrorsV06 for bytes;
                          using LibSafeMathV06 for uint256;
                          using LibERC20Transformer for IERC20TokenV06;
                          /// @dev Transform data to ABI-encode and pass into `transform()`.
                          struct TransformData {
                              // The tokens to transfer to the taker.
                              IERC20TokenV06[] tokens;
                              // Amount of each token in `tokens` to transfer to the taker.
                              // `uint(-1)` will transfer the entire balance.
                              uint256[] amounts;
                          }
                          /// @dev Maximum uint256 value.
                          uint256 private constant MAX_UINT256 = uint256(-1);
                          /// @dev Create this contract.
                          constructor()
                              public
                              Transformer()
                          {}
                          /// @dev Forwards tokens to the taker.
                          /// @param taker The taker address (caller of `TransformERC20.transformERC20()`).
                          /// @param data_ ABI-encoded `TransformData`, indicating which tokens to transfer.
                          /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                          function transform(
                              bytes32, // callDataHash,
                              address payable taker,
                              bytes calldata data_
                          )
                              external
                              override
                              returns (bytes4 success)
                          {
                              TransformData memory data = abi.decode(data_, (TransformData));
                              // Transfer tokens directly to the taker.
                              for (uint256 i = 0; i < data.tokens.length; ++i) {
                                  // The `amounts` array can be shorter than the `tokens` array.
                                  // Missing elements are treated as `uint256(-1)`.
                                  uint256 amount = data.amounts.length > i ? data.amounts[i] : uint256(-1);
                                  if (amount == MAX_UINT256) {
                                      amount = data.tokens[i].getTokenBalanceOf(address(this));
                                  }
                                  if (amount != 0) {
                                      data.tokens[i].transformerTransfer(taker, amount);
                                  }
                              }
                              return LibERC20Transformer.TRANSFORMER_SUCCESS;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
                      import "../errors/LibTransformERC20RichErrors.sol";
                      import "./Transformer.sol";
                      import "./LibERC20Transformer.sol";
                      /// @dev A transformer that wraps or unwraps WETH.
                      contract WethTransformer is
                          Transformer
                      {
                          using LibRichErrorsV06 for bytes;
                          using LibSafeMathV06 for uint256;
                          using LibERC20Transformer for IERC20TokenV06;
                          /// @dev Transform data to ABI-encode and pass into `transform()`.
                          struct TransformData {
                              // The token to wrap/unwrap. Must be either ETH or WETH.
                              IERC20TokenV06 token;
                              // Amount of `token` to wrap or unwrap.
                              // `uint(-1)` will unwrap the entire balance.
                              uint256 amount;
                          }
                          /// @dev The WETH contract address.
                          IEtherTokenV06 public immutable weth;
                          /// @dev Maximum uint256 value.
                          uint256 private constant MAX_UINT256 = uint256(-1);
                          /// @dev Construct the transformer and store the WETH address in an immutable.
                          /// @param weth_ The weth token.
                          constructor(IEtherTokenV06 weth_)
                              public
                              Transformer()
                          {
                              weth = weth_;
                          }
                          /// @dev Wraps and unwraps WETH.
                          /// @param data_ ABI-encoded `TransformData`, indicating which token to wrap/umwrap.
                          /// @return success The success bytes (`LibERC20Transformer.TRANSFORMER_SUCCESS`).
                          function transform(
                              bytes32, // callDataHash,
                              address payable, // taker,
                              bytes calldata data_
                          )
                              external
                              override
                              returns (bytes4 success)
                          {
                              TransformData memory data = abi.decode(data_, (TransformData));
                              if (!data.token.isTokenETH() && data.token != weth) {
                                  LibTransformERC20RichErrors.InvalidTransformDataError(
                                      LibTransformERC20RichErrors.InvalidTransformDataErrorCode.INVALID_TOKENS,
                                      data_
                                  ).rrevert();
                              }
                              uint256 amount = data.amount;
                              if (amount == MAX_UINT256) {
                                  amount = data.token.getTokenBalanceOf(address(this));
                              }
                              if (amount != 0) {
                                  if (data.token.isTokenETH()) {
                                      // Wrap ETH.
                                      weth.deposit{value: amount}();
                                  } else {
                                      // Unwrap WETH.
                                      weth.withdraw(amount);
                                  }
                              }
                              return LibERC20Transformer.TRANSFORMER_SUCCESS;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./IERC20TokenV06.sol";
                      interface IEtherTokenV06 is
                          IERC20TokenV06
                      {
                          /// @dev Wrap ether.
                          function deposit() external payable;
                          /// @dev Unwrap ether.
                          function withdraw(uint256 amount) external;
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      interface ITestSimpleFunctionRegistryFeature {
                          function testFn() external view returns (uint256 id);
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      contract TestCallTarget {
                          event CallTargetCalled(
                              address context,
                              address sender,
                              bytes data,
                              uint256 value
                          );
                          bytes4 private constant MAGIC_BYTES = 0x12345678;
                          bytes private constant REVERTING_DATA = hex"1337";
                          fallback() external payable {
                              if (keccak256(msg.data) == keccak256(REVERTING_DATA)) {
                                  revert("TestCallTarget/REVERT");
                              }
                              emit CallTargetCalled(
                                  address(this),
                                  msg.sender,
                                  msg.data,
                                  msg.value
                              );
                              bytes4 rval = MAGIC_BYTES;
                              assembly {
                                  mstore(0, rval)
                                  return(0, 32)
                              }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      contract TestDelegateCaller {
                          function executeDelegateCall(
                              address target,
                              bytes calldata callData
                          )
                              external
                          {
                              (bool success, bytes memory resultData) = target.delegatecall(callData);
                              if (!success) {
                                  assembly { revert(add(resultData, 32), mload(resultData)) }
                              }
                              assembly { return(add(resultData, 32), mload(resultData)) }
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibMathV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "../src/vendor/v3/IExchange.sol";
                      import "./TestMintableERC20Token.sol";
                      contract TestFillQuoteTransformerExchange {
                          struct FillBehavior {
                              // How much of the order is filled, in taker asset amount.
                              uint256 filledTakerAssetAmount;
                              // Scaling for maker assets minted, in 1e18.
                              uint256 makerAssetMintRatio;
                          }
                          uint256 private constant PROTOCOL_FEE_MULTIPLIER = 1337;
                          using LibSafeMathV06 for uint256;
                          function fillOrder(
                              IExchange.Order calldata order,
                              uint256 takerAssetFillAmount,
                              bytes calldata signature
                          )
                              external
                              payable
                              returns (IExchange.FillResults memory fillResults)
                          {
                              require(
                                  signature.length != 0,
                                  "TestFillQuoteTransformerExchange/INVALID_SIGNATURE"
                              );
                              // The signature is the ABI-encoded FillBehavior data.
                              FillBehavior memory behavior = abi.decode(signature, (FillBehavior));
                              uint256 protocolFee = PROTOCOL_FEE_MULTIPLIER * tx.gasprice;
                              require(
                                  msg.value == protocolFee,
                                  "TestFillQuoteTransformerExchange/INSUFFICIENT_PROTOCOL_FEE"
                              );
                              // Return excess protocol fee.
                              msg.sender.transfer(msg.value - protocolFee);
                              // Take taker tokens.
                              TestMintableERC20Token takerToken = _getTokenFromAssetData(order.takerAssetData);
                              takerAssetFillAmount = LibSafeMathV06.min256(
                                  order.takerAssetAmount.safeSub(behavior.filledTakerAssetAmount),
                                  takerAssetFillAmount
                              );
                              require(
                                  takerToken.getSpendableAmount(msg.sender, address(this)) >= takerAssetFillAmount,
                                  "TestFillQuoteTransformerExchange/INSUFFICIENT_TAKER_FUNDS"
                              );
                              takerToken.transferFrom(msg.sender, order.makerAddress, takerAssetFillAmount);
                              // Mint maker tokens.
                              uint256 makerAssetFilledAmount = LibMathV06.getPartialAmountFloor(
                                  takerAssetFillAmount,
                                  order.takerAssetAmount,
                                  order.makerAssetAmount
                              );
                              TestMintableERC20Token makerToken = _getTokenFromAssetData(order.makerAssetData);
                              makerToken.mint(
                                  msg.sender,
                                  LibMathV06.getPartialAmountFloor(
                                      behavior.makerAssetMintRatio,
                                      1e18,
                                      makerAssetFilledAmount
                                  )
                              );
                              // Take taker fee.
                              TestMintableERC20Token takerFeeToken = _getTokenFromAssetData(order.takerFeeAssetData);
                              uint256 takerFee = LibMathV06.getPartialAmountFloor(
                                  takerAssetFillAmount,
                                  order.takerAssetAmount,
                                  order.takerFee
                              );
                              require(
                                  takerFeeToken.getSpendableAmount(msg.sender, address(this)) >= takerFee,
                                  "TestFillQuoteTransformerExchange/INSUFFICIENT_TAKER_FEE_FUNDS"
                              );
                              takerFeeToken.transferFrom(msg.sender, order.feeRecipientAddress, takerFee);
                              fillResults.makerAssetFilledAmount = makerAssetFilledAmount;
                              fillResults.takerAssetFilledAmount = takerAssetFillAmount;
                              fillResults.makerFeePaid = uint256(-1);
                              fillResults.takerFeePaid = takerFee;
                              fillResults.protocolFeePaid = protocolFee;
                          }
                          function encodeBehaviorData(FillBehavior calldata behavior)
                              external
                              pure
                              returns (bytes memory encoded)
                          {
                              return abi.encode(behavior);
                          }
                          function protocolFeeMultiplier()
                              external
                              pure
                              returns (uint256)
                          {
                              return PROTOCOL_FEE_MULTIPLIER;
                          }
                          function getAssetProxy(bytes4)
                              external
                              view
                              returns (address)
                          {
                              return address(this);
                          }
                          function _getTokenFromAssetData(bytes memory assetData)
                              private
                              pure
                              returns (TestMintableERC20Token token)
                          {
                              return TestMintableERC20Token(LibBytesV06.readAddress(assetData, 16));
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      contract TestMintableERC20Token {
                          mapping(address => uint256) public balanceOf;
                          mapping(address => mapping(address => uint256)) public allowance;
                          function transfer(address to, uint256 amount)
                              external
                              virtual
                              returns (bool)
                          {
                              return transferFrom(msg.sender, to, amount);
                          }
                          function approve(address spender, uint256 amount)
                              external
                              virtual
                              returns (bool)
                          {
                              allowance[msg.sender][spender] = amount;
                              return true;
                          }
                          function mint(address owner, uint256 amount)
                              external
                              virtual
                          {
                              balanceOf[owner] += amount;
                          }
                          function burn(address owner, uint256 amount)
                              external
                              virtual
                          {
                              require(balanceOf[owner] >= amount, "TestMintableERC20Token/INSUFFICIENT_FUNDS");
                              balanceOf[owner] -= amount;
                          }
                          function transferFrom(address from, address to, uint256 amount)
                              public
                              virtual
                              returns (bool)
                          {
                              if (from != msg.sender) {
                                  require(
                                      allowance[from][msg.sender] >= amount,
                                      "TestMintableERC20Token/INSUFFICIENT_ALLOWANCE"
                                  );
                                  allowance[from][msg.sender] -= amount;
                              }
                              require(balanceOf[from] >= amount, "TestMintableERC20Token/INSUFFICIENT_FUNDS");
                              balanceOf[from] -= amount;
                              balanceOf[to] += amount;
                              return true;
                          }
                          function getSpendableAmount(address owner, address spender)
                              external
                              view
                              returns (uint256)
                          {
                              return balanceOf[owner] < allowance[owner][spender]
                                  ? balanceOf[owner]
                                  : allowance[owner][spender];
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/transformers/IERC20Transformer.sol";
                      import "./TestMintableERC20Token.sol";
                      import "./TestTransformerHost.sol";
                      contract TestFillQuoteTransformerHost is
                          TestTransformerHost
                      {
                          function executeTransform(
                              IERC20Transformer transformer,
                              TestMintableERC20Token inputToken,
                              uint256 inputTokenAmount,
                              bytes calldata data
                          )
                              external
                              payable
                          {
                              if (inputTokenAmount != 0) {
                                  inputToken.mint(address(this), inputTokenAmount);
                              }
                              // Have to make this call externally because transformers aren't payable.
                              this.rawExecuteTransform(transformer, bytes32(0), msg.sender, data);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "../src/transformers/IERC20Transformer.sol";
                      import "../src/transformers/LibERC20Transformer.sol";
                      contract TestTransformerHost {
                          using LibERC20Transformer for IERC20TokenV06;
                          using LibRichErrorsV06 for bytes;
                          function rawExecuteTransform(
                              IERC20Transformer transformer,
                              bytes32 callDataHash,
                              address taker,
                              bytes calldata data
                          )
                              external
                          {
                              (bool _success, bytes memory resultData) =
                                  address(transformer).delegatecall(abi.encodeWithSelector(
                                      transformer.transform.selector,
                                      callDataHash,
                                      taker,
                                      data
                                  ));
                              if (!_success) {
                                  resultData.rrevert();
                              }
                              require(
                                  abi.decode(resultData, (bytes4)) == LibERC20Transformer.TRANSFORMER_SUCCESS,
                                  "TestTransformerHost/INVALID_TRANSFORMER_RESULT"
                              );
                          }
                          // solhint-disable
                          receive() external payable {}
                          // solhint-enable
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/ZeroEx.sol";
                      import "../src/features/IBootstrap.sol";
                      import "../src/migrations/FullMigration.sol";
                      contract TestFullMigration is
                          FullMigration
                      {
                          address public dieRecipient;
                          // solhint-disable-next-line no-empty-blocks
                          constructor(address payable deployer) public FullMigration(deployer) {}
                          function die(address payable ethRecipient) external override {
                              dieRecipient = ethRecipient;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/ZeroEx.sol";
                      import "../src/features/IBootstrap.sol";
                      import "../src/migrations/InitialMigration.sol";
                      contract TestInitialMigration is
                          InitialMigration
                      {
                          address public bootstrapFeature;
                          address public dieRecipient;
                          // solhint-disable-next-line no-empty-blocks
                          constructor(address deployer) public InitialMigration(deployer) {}
                          function callBootstrap(ZeroEx zeroEx) external {
                              IBootstrap(address(zeroEx)).bootstrap(address(this), new bytes(0));
                          }
                          function bootstrap(address owner, BootstrapFeatures memory features)
                              public
                              override
                              returns (bytes4 success)
                          {
                              success = InitialMigration.bootstrap(owner, features);
                              // Snoop the bootstrap feature contract.
                              bootstrapFeature = ZeroEx(address(uint160(address(this))))
                                  .getFunctionImplementation(IBootstrap.bootstrap.selector);
                          }
                          function die(address payable ethRecipient) public override {
                              dieRecipient = ethRecipient;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/migrations/LibMigrate.sol";
                      import "../src/features/IOwnable.sol";
                      contract TestMigrator {
                          event TestMigrateCalled(
                              bytes callData,
                              address owner
                          );
                          function succeedingMigrate() external returns (bytes4 success) {
                              emit TestMigrateCalled(
                                  msg.data,
                                  IOwnable(address(this)).owner()
                              );
                              return LibMigrate.MIGRATE_SUCCESS;
                          }
                          function failingMigrate() external returns (bytes4 success) {
                              emit TestMigrateCalled(
                                  msg.data,
                                  IOwnable(address(this)).owner()
                              );
                              return 0xdeadbeef;
                          }
                          function revertingMigrate() external pure {
                              revert("OOPSIE");
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "../src/transformers/IERC20Transformer.sol";
                      import "../src/transformers/LibERC20Transformer.sol";
                      import "./TestMintableERC20Token.sol";
                      contract TestMintTokenERC20Transformer is
                          IERC20Transformer
                      {
                          struct TransformData {
                              IERC20TokenV06 inputToken;
                              TestMintableERC20Token outputToken;
                              uint256 burnAmount;
                              uint256 mintAmount;
                              uint256 feeAmount;
                          }
                          event MintTransform(
                              address context,
                              address caller,
                              bytes32 callDataHash,
                              address taker,
                              bytes data,
                              uint256 inputTokenBalance,
                              uint256 ethBalance
                          );
                          function transform(
                              bytes32 callDataHash,
                              address payable taker,
                              bytes calldata data_
                          )
                              external
                              override
                              returns (bytes4 success)
                          {
                              TransformData memory data = abi.decode(data_, (TransformData));
                              emit MintTransform(
                                  address(this),
                                  msg.sender,
                                  callDataHash,
                                  taker,
                                  data_,
                                  data.inputToken.balanceOf(address(this)),
                                  address(this).balance
                              );
                              // "Burn" input tokens.
                              data.inputToken.transfer(address(0), data.burnAmount);
                              // Mint output tokens.
                              if (LibERC20Transformer.isTokenETH(IERC20TokenV06(address(data.outputToken)))) {
                                  taker.transfer(data.mintAmount);
                              } else {
                                  data.outputToken.mint(
                                      taker,
                                      data.mintAmount
                                  );
                                  // Burn fees from output.
                                  data.outputToken.burn(taker, data.feeAmount);
                              }
                              return LibERC20Transformer.TRANSFORMER_SUCCESS;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/fixins/FixinCommon.sol";
                      contract TestSimpleFunctionRegistryFeatureImpl1 is
                          FixinCommon
                      {
                          function testFn()
                              external
                              pure
                              returns (uint256 id)
                          {
                              return 1337;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/fixins/FixinCommon.sol";
                      contract TestSimpleFunctionRegistryFeatureImpl2 is
                          FixinCommon
                      {
                          function testFn()
                              external
                              pure
                              returns (uint256 id)
                          {
                              return 1338;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/features/TokenSpender.sol";
                      contract TestTokenSpender is
                          TokenSpender
                      {
                          modifier onlySelf() override {
                              _;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./TestMintableERC20Token.sol";
                      contract TestTokenSpenderERC20Token is
                          TestMintableERC20Token
                      {
                          event TransferFromCalled(
                              address sender,
                              address from,
                              address to,
                              uint256 amount
                          );
                          // `transferFrom()` behavior depends on the value of `amount`.
                          uint256 constant private EMPTY_RETURN_AMOUNT = 1337;
                          uint256 constant private FALSE_RETURN_AMOUNT = 1338;
                          uint256 constant private REVERT_RETURN_AMOUNT = 1339;
                          function transferFrom(address from, address to, uint256 amount)
                              public
                              override
                              returns (bool)
                          {
                              emit TransferFromCalled(msg.sender, from, to, amount);
                              if (amount == EMPTY_RETURN_AMOUNT) {
                                  assembly { return(0, 0) }
                              }
                              if (amount == FALSE_RETURN_AMOUNT) {
                                  return false;
                              }
                              if (amount == REVERT_RETURN_AMOUNT) {
                                  revert("TestTokenSpenderERC20Token/Revert");
                              }
                              return true;
                          }
                          function setBalanceAndAllowanceOf(
                              address owner,
                              uint256 balance,
                              address spender,
                              uint256 allowance_
                          )
                              external
                          {
                              balanceOf[owner] = balance;
                              allowance[owner][spender] = allowance_;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/features/TransformERC20.sol";
                      contract TestTransformERC20 is
                          TransformERC20
                      {
                          // solhint-disable no-empty-blocks
                          constructor()
                              TransformERC20()
                              public
                          {}
                          modifier onlySelf() override {
                              _;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/transformers/Transformer.sol";
                      import "../src/transformers/LibERC20Transformer.sol";
                      contract TestTransformerBase is
                          Transformer
                      {
                          function transform(
                              bytes32,
                              address payable,
                              bytes calldata
                          )
                              external
                              override
                              returns (bytes4 success)
                          {
                              return LibERC20Transformer.TRANSFORMER_SUCCESS;
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/transformers/LibERC20Transformer.sol";
                      contract TestTransformerDeployerTransformer {
                          address payable public immutable deployer;
                          constructor() public payable {
                              deployer = msg.sender;
                          }
                          modifier onlyDeployer() {
                              require(msg.sender == deployer, "TestTransformerDeployerTransformer/ONLY_DEPLOYER");
                              _;
                          }
                          function die()
                              external
                              onlyDeployer
                          {
                              selfdestruct(deployer);
                          }
                          function isDeployedByDeployer(uint32 nonce)
                              external
                              view
                              returns (bool)
                          {
                              return LibERC20Transformer.getDeployedAddress(deployer, nonce) == address(this);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./TestMintableERC20Token.sol";
                      contract TestWeth is
                          TestMintableERC20Token
                      {
                          function deposit()
                              external
                              payable
                          {
                              this.mint(msg.sender, msg.value);
                          }
                          function withdraw(uint256 amount)
                              external
                          {
                              require(balanceOf[msg.sender] >= amount, "TestWeth/INSUFFICIENT_FUNDS");
                              balanceOf[msg.sender] -= amount;
                              msg.sender.transfer(amount);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/transformers/IERC20Transformer.sol";
                      import "./TestMintableERC20Token.sol";
                      import "./TestTransformerHost.sol";
                      import "./TestWeth.sol";
                      contract TestWethTransformerHost is
                          TestTransformerHost
                      {
                          // solhint-disable
                          TestWeth private immutable _weth;
                          // solhint-enable
                          constructor(TestWeth weth) public {
                              _weth = weth;
                          }
                          function executeTransform(
                              uint256 wethAmount,
                              IERC20Transformer transformer,
                              bytes calldata data
                          )
                              external
                              payable
                          {
                              if (wethAmount != 0) {
                                  _weth.deposit{value: wethAmount}();
                              }
                              // Have to make this call externally because transformers aren't payable.
                              this.rawExecuteTransform(transformer, bytes32(0), msg.sender, data);
                          }
                      }
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../src/fixins/FixinCommon.sol";
                      import "../src/ZeroEx.sol";
                      contract TestZeroExFeature is
                          FixinCommon
                      {
                          event PayableFnCalled(uint256 value);
                          event NotPayableFnCalled();
                          function payableFn()
                              external
                              payable
                          {
                              emit PayableFnCalled(msg.value);
                          }
                          function notPayableFn()
                              external
                          {
                              emit NotPayableFnCalled();
                          }
                          // solhint-disable no-empty-blocks
                          function unimplmentedFn()
                              external
                          {}
                          function internalFn()
                              external
                              onlySelf
                          {}
                      }
                      

                      File 6 of 7: FiatTokenV2_2
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { EIP712Domain } from "./EIP712Domain.sol"; // solhint-disable-line no-unused-import
                      import { Blacklistable } from "../v1/Blacklistable.sol"; // solhint-disable-line no-unused-import
                      import { FiatTokenV1 } from "../v1/FiatTokenV1.sol"; // solhint-disable-line no-unused-import
                      import { FiatTokenV2 } from "./FiatTokenV2.sol"; // solhint-disable-line no-unused-import
                      import { FiatTokenV2_1 } from "./FiatTokenV2_1.sol";
                      import { EIP712 } from "../util/EIP712.sol";
                      // solhint-disable func-name-mixedcase
                      /**
                       * @title FiatToken V2.2
                       * @notice ERC20 Token backed by fiat reserves, version 2.2
                       */
                      contract FiatTokenV2_2 is FiatTokenV2_1 {
                          /**
                           * @notice Initialize v2.2
                           * @param accountsToBlacklist   A list of accounts to migrate from the old blacklist
                           * @param newSymbol             New token symbol
                           * data structure to the new blacklist data structure.
                           */
                          function initializeV2_2(
                              address[] calldata accountsToBlacklist,
                              string calldata newSymbol
                          ) external {
                              // solhint-disable-next-line reason-string
                              require(_initializedVersion == 2);
                              // Update fiat token symbol
                              symbol = newSymbol;
                              // Add previously blacklisted accounts to the new blacklist data structure
                              // and remove them from the old blacklist data structure.
                              for (uint256 i = 0; i < accountsToBlacklist.length; i++) {
                                  require(
                                      _deprecatedBlacklisted[accountsToBlacklist[i]],
                                      "FiatTokenV2_2: Blacklisting previously unblacklisted account!"
                                  );
                                  _blacklist(accountsToBlacklist[i]);
                                  delete _deprecatedBlacklisted[accountsToBlacklist[i]];
                              }
                              _blacklist(address(this));
                              delete _deprecatedBlacklisted[address(this)];
                              _initializedVersion = 3;
                          }
                          /**
                           * @dev Internal function to get the current chain id.
                           * @return The current chain id.
                           */
                          function _chainId() internal virtual view returns (uint256) {
                              uint256 chainId;
                              assembly {
                                  chainId := chainid()
                              }
                              return chainId;
                          }
                          /**
                           * @inheritdoc EIP712Domain
                           */
                          function _domainSeparator() internal override view returns (bytes32) {
                              return EIP712.makeDomainSeparator(name, "2", _chainId());
                          }
                          /**
                           * @notice Update allowance with a signed permit
                           * @dev EOA wallet signatures should be packed in the order of r, s, v.
                           * @param owner       Token owner's address (Authorizer)
                           * @param spender     Spender's address
                           * @param value       Amount of allowance
                           * @param deadline    The time at which the signature expires (unix time), or max uint256 value to signal no expiration
                           * @param signature   Signature bytes signed by an EOA wallet or a contract wallet
                           */
                          function permit(
                              address owner,
                              address spender,
                              uint256 value,
                              uint256 deadline,
                              bytes memory signature
                          ) external whenNotPaused {
                              _permit(owner, spender, value, deadline, signature);
                          }
                          /**
                           * @notice Execute a transfer with a signed authorization
                           * @dev EOA wallet signatures should be packed in the order of r, s, v.
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param signature     Signature bytes signed by an EOA wallet or a contract wallet
                           */
                          function transferWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              bytes memory signature
                          ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
                              _transferWithAuthorization(
                                  from,
                                  to,
                                  value,
                                  validAfter,
                                  validBefore,
                                  nonce,
                                  signature
                              );
                          }
                          /**
                           * @notice Receive a transfer with a signed authorization from the payer
                           * @dev This has an additional check to ensure that the payee's address
                           * matches the caller of this function to prevent front-running attacks.
                           * EOA wallet signatures should be packed in the order of r, s, v.
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param signature     Signature bytes signed by an EOA wallet or a contract wallet
                           */
                          function receiveWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              bytes memory signature
                          ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
                              _receiveWithAuthorization(
                                  from,
                                  to,
                                  value,
                                  validAfter,
                                  validBefore,
                                  nonce,
                                  signature
                              );
                          }
                          /**
                           * @notice Attempt to cancel an authorization
                           * @dev Works only if the authorization is not yet used.
                           * EOA wallet signatures should be packed in the order of r, s, v.
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           * @param signature     Signature bytes signed by an EOA wallet or a contract wallet
                           */
                          function cancelAuthorization(
                              address authorizer,
                              bytes32 nonce,
                              bytes memory signature
                          ) external whenNotPaused {
                              _cancelAuthorization(authorizer, nonce, signature);
                          }
                          /**
                           * @dev Helper method that sets the blacklist state of an account on balanceAndBlacklistStates.
                           * If _shouldBlacklist is true, we apply a (1 << 255) bitmask with an OR operation on the
                           * account's balanceAndBlacklistState. This flips the high bit for the account to 1,
                           * indicating that the account is blacklisted.
                           *
                           * If _shouldBlacklist if false, we reset the account's balanceAndBlacklistStates to their
                           * balances. This clears the high bit for the account, indicating that the account is unblacklisted.
                           * @param _account         The address of the account.
                           * @param _shouldBlacklist True if the account should be blacklisted, false if the account should be unblacklisted.
                           */
                          function _setBlacklistState(address _account, bool _shouldBlacklist)
                              internal
                              override
                          {
                              balanceAndBlacklistStates[_account] = _shouldBlacklist
                                  ? balanceAndBlacklistStates[_account] | (1 << 255)
                                  : _balanceOf(_account);
                          }
                          /**
                           * @dev Helper method that sets the balance of an account on balanceAndBlacklistStates.
                           * Since balances are stored in the last 255 bits of the balanceAndBlacklistStates value,
                           * we need to ensure that the updated balance does not exceed (2^255 - 1).
                           * Since blacklisted accounts' balances cannot be updated, the method will also
                           * revert if the account is blacklisted
                           * @param _account The address of the account.
                           * @param _balance The new fiat token balance of the account (max: (2^255 - 1)).
                           */
                          function _setBalance(address _account, uint256 _balance) internal override {
                              require(
                                  _balance <= ((1 << 255) - 1),
                                  "FiatTokenV2_2: Balance exceeds (2^255 - 1)"
                              );
                              require(
                                  !_isBlacklisted(_account),
                                  "FiatTokenV2_2: Account is blacklisted"
                              );
                              balanceAndBlacklistStates[_account] = _balance;
                          }
                          /**
                           * @inheritdoc Blacklistable
                           */
                          function _isBlacklisted(address _account)
                              internal
                              override
                              view
                              returns (bool)
                          {
                              return balanceAndBlacklistStates[_account] >> 255 == 1;
                          }
                          /**
                           * @dev Helper method to obtain the balance of an account. Since balances
                           * are stored in the last 255 bits of the balanceAndBlacklistStates value,
                           * we apply a ((1 << 255) - 1) bit bitmask with an AND operation on the
                           * balanceAndBlacklistState to obtain the balance.
                           * @param _account  The address of the account.
                           * @return          The fiat token balance of the account.
                           */
                          function _balanceOf(address _account)
                              internal
                              override
                              view
                              returns (uint256)
                          {
                              return balanceAndBlacklistStates[_account] & ((1 << 255) - 1);
                          }
                          /**
                           * @inheritdoc FiatTokenV1
                           */
                          function approve(address spender, uint256 value)
                              external
                              override
                              whenNotPaused
                              returns (bool)
                          {
                              _approve(msg.sender, spender, value);
                              return true;
                          }
                          /**
                           * @inheritdoc FiatTokenV2
                           */
                          function permit(
                              address owner,
                              address spender,
                              uint256 value,
                              uint256 deadline,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) external override whenNotPaused {
                              _permit(owner, spender, value, deadline, v, r, s);
                          }
                          /**
                           * @inheritdoc FiatTokenV2
                           */
                          function increaseAllowance(address spender, uint256 increment)
                              external
                              override
                              whenNotPaused
                              returns (bool)
                          {
                              _increaseAllowance(msg.sender, spender, increment);
                              return true;
                          }
                          /**
                           * @inheritdoc FiatTokenV2
                           */
                          function decreaseAllowance(address spender, uint256 decrement)
                              external
                              override
                              whenNotPaused
                              returns (bool)
                          {
                              _decreaseAllowance(msg.sender, spender, decrement);
                              return true;
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity >=0.6.2 <0.8.0;
                      /**
                       * @dev Collection of functions related to the address type
                       */
                      library Address {
                          /**
                           * @dev Returns true if `account` is a contract.
                           *
                           * [IMPORTANT]
                           * ====
                           * It is unsafe to assume that an address for which this function returns
                           * false is an externally-owned account (EOA) and not a contract.
                           *
                           * Among others, `isContract` will return false for the following
                           * types of addresses:
                           *
                           *  - an externally-owned account
                           *  - a contract in construction
                           *  - an address where a contract will be created
                           *  - an address where a contract lived, but was destroyed
                           * ====
                           */
                          function isContract(address account) internal view returns (bool) {
                              // This method relies on extcodesize, which returns 0 for contracts in
                              // construction, since the code is only stored at the end of the
                              // constructor execution.
                              uint256 size;
                              // solhint-disable-next-line no-inline-assembly
                              assembly { size := extcodesize(account) }
                              return size > 0;
                          }
                          /**
                           * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
                           * `recipient`, forwarding all available gas and reverting on errors.
                           *
                           * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
                           * of certain opcodes, possibly making contracts go over the 2300 gas limit
                           * imposed by `transfer`, making them unable to receive funds via
                           * `transfer`. {sendValue} removes this limitation.
                           *
                           * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
                           *
                           * IMPORTANT: because control is transferred to `recipient`, care must be
                           * taken to not create reentrancy vulnerabilities. Consider using
                           * {ReentrancyGuard} or the
                           * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
                           */
                          function sendValue(address payable recipient, uint256 amount) internal {
                              require(address(this).balance >= amount, "Address: insufficient balance");
                              // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
                              (bool success, ) = recipient.call{ value: amount }("");
                              require(success, "Address: unable to send value, recipient may have reverted");
                          }
                          /**
                           * @dev Performs a Solidity function call using a low level `call`. A
                           * plain`call` is an unsafe replacement for a function call: use this
                           * function instead.
                           *
                           * If `target` reverts with a revert reason, it is bubbled up by this
                           * function (like regular Solidity function calls).
                           *
                           * Returns the raw returned data. To convert to the expected return value,
                           * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
                           *
                           * Requirements:
                           *
                           * - `target` must be a contract.
                           * - calling `target` with `data` must not revert.
                           *
                           * _Available since v3.1._
                           */
                          function functionCall(address target, bytes memory data) internal returns (bytes memory) {
                            return functionCall(target, data, "Address: low-level call failed");
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
                           * `errorMessage` as a fallback revert reason when `target` reverts.
                           *
                           * _Available since v3.1._
                           */
                          function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
                              return functionCallWithValue(target, data, 0, errorMessage);
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
                           * but also transferring `value` wei to `target`.
                           *
                           * Requirements:
                           *
                           * - the calling contract must have an ETH balance of at least `value`.
                           * - the called Solidity function must be `payable`.
                           *
                           * _Available since v3.1._
                           */
                          function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
                              return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
                          }
                          /**
                           * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
                           * with `errorMessage` as a fallback revert reason when `target` reverts.
                           *
                           * _Available since v3.1._
                           */
                          function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
                              require(address(this).balance >= value, "Address: insufficient balance for call");
                              require(isContract(target), "Address: call to non-contract");
                              // solhint-disable-next-line avoid-low-level-calls
                              (bool success, bytes memory returndata) = target.call{ value: value }(data);
                              return _verifyCallResult(success, returndata, errorMessage);
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
                           * but performing a static call.
                           *
                           * _Available since v3.3._
                           */
                          function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
                              return functionStaticCall(target, data, "Address: low-level static call failed");
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
                           * but performing a static call.
                           *
                           * _Available since v3.3._
                           */
                          function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
                              require(isContract(target), "Address: static call to non-contract");
                              // solhint-disable-next-line avoid-low-level-calls
                              (bool success, bytes memory returndata) = target.staticcall(data);
                              return _verifyCallResult(success, returndata, errorMessage);
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
                           * but performing a delegate call.
                           *
                           * _Available since v3.4._
                           */
                          function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
                              return functionDelegateCall(target, data, "Address: low-level delegate call failed");
                          }
                          /**
                           * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
                           * but performing a delegate call.
                           *
                           * _Available since v3.4._
                           */
                          function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
                              require(isContract(target), "Address: delegate call to non-contract");
                              // solhint-disable-next-line avoid-low-level-calls
                              (bool success, bytes memory returndata) = target.delegatecall(data);
                              return _verifyCallResult(success, returndata, errorMessage);
                          }
                          function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
                              if (success) {
                                  return returndata;
                              } else {
                                  // Look for revert reason and bubble it up if present
                                  if (returndata.length > 0) {
                                      // The easiest way to bubble the revert reason is using memory via assembly
                                      // solhint-disable-next-line no-inline-assembly
                                      assembly {
                                          let returndata_size := mload(returndata)
                                          revert(add(32, returndata), returndata_size)
                                      }
                                  } else {
                                      revert(errorMessage);
                                  }
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity >=0.6.0 <0.8.0;
                      import "./IERC20.sol";
                      import "../../math/SafeMath.sol";
                      import "../../utils/Address.sol";
                      /**
                       * @title SafeERC20
                       * @dev Wrappers around ERC20 operations that throw on failure (when the token
                       * contract returns false). Tokens that return no value (and instead revert or
                       * throw on failure) are also supported, non-reverting calls are assumed to be
                       * successful.
                       * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
                       * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
                       */
                      library SafeERC20 {
                          using SafeMath for uint256;
                          using Address for address;
                          function safeTransfer(IERC20 token, address to, uint256 value) internal {
                              _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
                          }
                          function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
                              _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
                          }
                          /**
                           * @dev Deprecated. This function has issues similar to the ones found in
                           * {IERC20-approve}, and its usage is discouraged.
                           *
                           * Whenever possible, use {safeIncreaseAllowance} and
                           * {safeDecreaseAllowance} instead.
                           */
                          function safeApprove(IERC20 token, address spender, uint256 value) internal {
                              // safeApprove should only be called when setting an initial allowance,
                              // or when resetting it to zero. To increase and decrease it, use
                              // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
                              // solhint-disable-next-line max-line-length
                              require((value == 0) || (token.allowance(address(this), spender) == 0),
                                  "SafeERC20: approve from non-zero to non-zero allowance"
                              );
                              _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
                          }
                          function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
                              uint256 newAllowance = token.allowance(address(this), spender).add(value);
                              _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
                          }
                          function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
                              uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
                              _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
                          }
                          /**
                           * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
                           * on the return value: the return value is optional (but if data is returned, it must not be false).
                           * @param token The token targeted by the call.
                           * @param data The call data (encoded using abi.encode or one of its variants).
                           */
                          function _callOptionalReturn(IERC20 token, bytes memory data) private {
                              // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
                              // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
                              // the target address contains contract code and also asserts for success in the low-level call.
                              bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
                              if (returndata.length > 0) { // Return data is optional
                                  // solhint-disable-next-line max-line-length
                                  require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
                              }
                          }
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity >=0.6.0 <0.8.0;
                      /**
                       * @dev Interface of the ERC20 standard as defined in the EIP.
                       */
                      interface IERC20 {
                          /**
                           * @dev Returns the amount of tokens in existence.
                           */
                          function totalSupply() external view returns (uint256);
                          /**
                           * @dev Returns the amount of tokens owned by `account`.
                           */
                          function balanceOf(address account) external view returns (uint256);
                          /**
                           * @dev Moves `amount` tokens from the caller's account to `recipient`.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * Emits a {Transfer} event.
                           */
                          function transfer(address recipient, uint256 amount) external returns (bool);
                          /**
                           * @dev Returns the remaining number of tokens that `spender` will be
                           * allowed to spend on behalf of `owner` through {transferFrom}. This is
                           * zero by default.
                           *
                           * This value changes when {approve} or {transferFrom} are called.
                           */
                          function allowance(address owner, address spender) external view returns (uint256);
                          /**
                           * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * IMPORTANT: Beware that changing an allowance with this method brings the risk
                           * that someone may use both the old and the new allowance by unfortunate
                           * transaction ordering. One possible solution to mitigate this race
                           * condition is to first reduce the spender's allowance to 0 and set the
                           * desired value afterwards:
                           * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
                           *
                           * Emits an {Approval} event.
                           */
                          function approve(address spender, uint256 amount) external returns (bool);
                          /**
                           * @dev Moves `amount` tokens from `sender` to `recipient` using the
                           * allowance mechanism. `amount` is then deducted from the caller's
                           * allowance.
                           *
                           * Returns a boolean value indicating whether the operation succeeded.
                           *
                           * Emits a {Transfer} event.
                           */
                          function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
                          /**
                           * @dev Emitted when `value` tokens are moved from one account (`from`) to
                           * another (`to`).
                           *
                           * Note that `value` may be zero.
                           */
                          event Transfer(address indexed from, address indexed to, uint256 value);
                          /**
                           * @dev Emitted when the allowance of a `spender` for an `owner` is set by
                           * a call to {approve}. `value` is the new allowance.
                           */
                          event Approval(address indexed owner, address indexed spender, uint256 value);
                      }
                      // SPDX-License-Identifier: MIT
                      pragma solidity >=0.6.0 <0.8.0;
                      /**
                       * @dev Wrappers over Solidity's arithmetic operations with added overflow
                       * checks.
                       *
                       * Arithmetic operations in Solidity wrap on overflow. This can easily result
                       * in bugs, because programmers usually assume that an overflow raises an
                       * error, which is the standard behavior in high level programming languages.
                       * `SafeMath` restores this intuition by reverting the transaction when an
                       * operation overflows.
                       *
                       * Using this library instead of the unchecked operations eliminates an entire
                       * class of bugs, so it's recommended to use it always.
                       */
                      library SafeMath {
                          /**
                           * @dev Returns the addition of two unsigned integers, with an overflow flag.
                           *
                           * _Available since v3.4._
                           */
                          function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
                              uint256 c = a + b;
                              if (c < a) return (false, 0);
                              return (true, c);
                          }
                          /**
                           * @dev Returns the substraction of two unsigned integers, with an overflow flag.
                           *
                           * _Available since v3.4._
                           */
                          function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
                              if (b > a) return (false, 0);
                              return (true, a - b);
                          }
                          /**
                           * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
                           *
                           * _Available since v3.4._
                           */
                          function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
                              // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
                              // benefit is lost if 'b' is also tested.
                              // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
                              if (a == 0) return (true, 0);
                              uint256 c = a * b;
                              if (c / a != b) return (false, 0);
                              return (true, c);
                          }
                          /**
                           * @dev Returns the division of two unsigned integers, with a division by zero flag.
                           *
                           * _Available since v3.4._
                           */
                          function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
                              if (b == 0) return (false, 0);
                              return (true, a / b);
                          }
                          /**
                           * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
                           *
                           * _Available since v3.4._
                           */
                          function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
                              if (b == 0) return (false, 0);
                              return (true, a % b);
                          }
                          /**
                           * @dev Returns the addition of two unsigned integers, reverting on
                           * overflow.
                           *
                           * Counterpart to Solidity's `+` operator.
                           *
                           * Requirements:
                           *
                           * - Addition cannot overflow.
                           */
                          function add(uint256 a, uint256 b) internal pure returns (uint256) {
                              uint256 c = a + b;
                              require(c >= a, "SafeMath: addition overflow");
                              return c;
                          }
                          /**
                           * @dev Returns the subtraction of two unsigned integers, reverting on
                           * overflow (when the result is negative).
                           *
                           * Counterpart to Solidity's `-` operator.
                           *
                           * Requirements:
                           *
                           * - Subtraction cannot overflow.
                           */
                          function sub(uint256 a, uint256 b) internal pure returns (uint256) {
                              require(b <= a, "SafeMath: subtraction overflow");
                              return a - b;
                          }
                          /**
                           * @dev Returns the multiplication of two unsigned integers, reverting on
                           * overflow.
                           *
                           * Counterpart to Solidity's `*` operator.
                           *
                           * Requirements:
                           *
                           * - Multiplication cannot overflow.
                           */
                          function mul(uint256 a, uint256 b) internal pure returns (uint256) {
                              if (a == 0) return 0;
                              uint256 c = a * b;
                              require(c / a == b, "SafeMath: multiplication overflow");
                              return c;
                          }
                          /**
                           * @dev Returns the integer division of two unsigned integers, reverting on
                           * division by zero. The result is rounded towards zero.
                           *
                           * Counterpart to Solidity's `/` operator. Note: this function uses a
                           * `revert` opcode (which leaves remaining gas untouched) while Solidity
                           * uses an invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function div(uint256 a, uint256 b) internal pure returns (uint256) {
                              require(b > 0, "SafeMath: division by zero");
                              return a / b;
                          }
                          /**
                           * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
                           * reverting when dividing by zero.
                           *
                           * Counterpart to Solidity's `%` operator. This function uses a `revert`
                           * opcode (which leaves remaining gas untouched) while Solidity uses an
                           * invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function mod(uint256 a, uint256 b) internal pure returns (uint256) {
                              require(b > 0, "SafeMath: modulo by zero");
                              return a % b;
                          }
                          /**
                           * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
                           * overflow (when the result is negative).
                           *
                           * CAUTION: This function is deprecated because it requires allocating memory for the error
                           * message unnecessarily. For custom revert reasons use {trySub}.
                           *
                           * Counterpart to Solidity's `-` operator.
                           *
                           * Requirements:
                           *
                           * - Subtraction cannot overflow.
                           */
                          function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
                              require(b <= a, errorMessage);
                              return a - b;
                          }
                          /**
                           * @dev Returns the integer division of two unsigned integers, reverting with custom message on
                           * division by zero. The result is rounded towards zero.
                           *
                           * CAUTION: This function is deprecated because it requires allocating memory for the error
                           * message unnecessarily. For custom revert reasons use {tryDiv}.
                           *
                           * Counterpart to Solidity's `/` operator. Note: this function uses a
                           * `revert` opcode (which leaves remaining gas untouched) while Solidity
                           * uses an invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
                              require(b > 0, errorMessage);
                              return a / b;
                          }
                          /**
                           * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
                           * reverting with custom message when dividing by zero.
                           *
                           * CAUTION: This function is deprecated because it requires allocating memory for the error
                           * message unnecessarily. For custom revert reasons use {tryMod}.
                           *
                           * Counterpart to Solidity's `%` operator. This function uses a `revert`
                           * opcode (which leaves remaining gas untouched) while Solidity uses an
                           * invalid opcode to revert (consuming all remaining gas).
                           *
                           * Requirements:
                           *
                           * - The divisor cannot be zero.
                           */
                          function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
                              require(b > 0, errorMessage);
                              return a % b;
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { FiatTokenV2 } from "./FiatTokenV2.sol";
                      // solhint-disable func-name-mixedcase
                      /**
                       * @title FiatToken V2.1
                       * @notice ERC20 Token backed by fiat reserves, version 2.1
                       */
                      contract FiatTokenV2_1 is FiatTokenV2 {
                          /**
                           * @notice Initialize v2.1
                           * @param lostAndFound  The address to which the locked funds are sent
                           */
                          function initializeV2_1(address lostAndFound) external {
                              // solhint-disable-next-line reason-string
                              require(_initializedVersion == 1);
                              uint256 lockedAmount = _balanceOf(address(this));
                              if (lockedAmount > 0) {
                                  _transfer(address(this), lostAndFound, lockedAmount);
                              }
                              _blacklist(address(this));
                              _initializedVersion = 2;
                          }
                          /**
                           * @notice Version string for the EIP712 domain separator
                           * @return Version string
                           */
                          function version() external pure returns (string memory) {
                              return "2";
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { FiatTokenV1_1 } from "../v1.1/FiatTokenV1_1.sol";
                      import { EIP712 } from "../util/EIP712.sol";
                      import { EIP3009 } from "./EIP3009.sol";
                      import { EIP2612 } from "./EIP2612.sol";
                      /**
                       * @title FiatToken V2
                       * @notice ERC20 Token backed by fiat reserves, version 2
                       */
                      contract FiatTokenV2 is FiatTokenV1_1, EIP3009, EIP2612 {
                          uint8 internal _initializedVersion;
                          /**
                           * @notice Initialize v2
                           * @param newName   New token name
                           */
                          function initializeV2(string calldata newName) external {
                              // solhint-disable-next-line reason-string
                              require(initialized && _initializedVersion == 0);
                              name = newName;
                              _DEPRECATED_CACHED_DOMAIN_SEPARATOR = EIP712.makeDomainSeparator(
                                  newName,
                                  "2"
                              );
                              _initializedVersion = 1;
                          }
                          /**
                           * @notice Increase the allowance by a given increment
                           * @param spender   Spender's address
                           * @param increment Amount of increase in allowance
                           * @return True if successful
                           */
                          function increaseAllowance(address spender, uint256 increment)
                              external
                              virtual
                              whenNotPaused
                              notBlacklisted(msg.sender)
                              notBlacklisted(spender)
                              returns (bool)
                          {
                              _increaseAllowance(msg.sender, spender, increment);
                              return true;
                          }
                          /**
                           * @notice Decrease the allowance by a given decrement
                           * @param spender   Spender's address
                           * @param decrement Amount of decrease in allowance
                           * @return True if successful
                           */
                          function decreaseAllowance(address spender, uint256 decrement)
                              external
                              virtual
                              whenNotPaused
                              notBlacklisted(msg.sender)
                              notBlacklisted(spender)
                              returns (bool)
                          {
                              _decreaseAllowance(msg.sender, spender, decrement);
                              return true;
                          }
                          /**
                           * @notice Execute a transfer with a signed authorization
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param v             v of the signature
                           * @param r             r of the signature
                           * @param s             s of the signature
                           */
                          function transferWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
                              _transferWithAuthorization(
                                  from,
                                  to,
                                  value,
                                  validAfter,
                                  validBefore,
                                  nonce,
                                  v,
                                  r,
                                  s
                              );
                          }
                          /**
                           * @notice Receive a transfer with a signed authorization from the payer
                           * @dev This has an additional check to ensure that the payee's address
                           * matches the caller of this function to prevent front-running attacks.
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param v             v of the signature
                           * @param r             r of the signature
                           * @param s             s of the signature
                           */
                          function receiveWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
                              _receiveWithAuthorization(
                                  from,
                                  to,
                                  value,
                                  validAfter,
                                  validBefore,
                                  nonce,
                                  v,
                                  r,
                                  s
                              );
                          }
                          /**
                           * @notice Attempt to cancel an authorization
                           * @dev Works only if the authorization is not yet used.
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           * @param v             v of the signature
                           * @param r             r of the signature
                           * @param s             s of the signature
                           */
                          function cancelAuthorization(
                              address authorizer,
                              bytes32 nonce,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) external whenNotPaused {
                              _cancelAuthorization(authorizer, nonce, v, r, s);
                          }
                          /**
                           * @notice Update allowance with a signed permit
                           * @param owner       Token owner's address (Authorizer)
                           * @param spender     Spender's address
                           * @param value       Amount of allowance
                           * @param deadline    The time at which the signature expires (unix time), or max uint256 value to signal no expiration
                           * @param v           v of the signature
                           * @param r           r of the signature
                           * @param s           s of the signature
                           */
                          function permit(
                              address owner,
                              address spender,
                              uint256 value,
                              uint256 deadline,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          )
                              external
                              virtual
                              whenNotPaused
                              notBlacklisted(owner)
                              notBlacklisted(spender)
                          {
                              _permit(owner, spender, value, deadline, v, r, s);
                          }
                          /**
                           * @dev Internal function to increase the allowance by a given increment
                           * @param owner     Token owner's address
                           * @param spender   Spender's address
                           * @param increment Amount of increase
                           */
                          function _increaseAllowance(
                              address owner,
                              address spender,
                              uint256 increment
                          ) internal override {
                              _approve(owner, spender, allowed[owner][spender].add(increment));
                          }
                          /**
                           * @dev Internal function to decrease the allowance by a given decrement
                           * @param owner     Token owner's address
                           * @param spender   Spender's address
                           * @param decrement Amount of decrease
                           */
                          function _decreaseAllowance(
                              address owner,
                              address spender,
                              uint256 decrement
                          ) internal override {
                              _approve(
                                  owner,
                                  spender,
                                  allowed[owner][spender].sub(
                                      decrement,
                                      "ERC20: decreased allowance below zero"
                                  )
                              );
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      // solhint-disable func-name-mixedcase
                      /**
                       * @title EIP712 Domain
                       */
                      contract EIP712Domain {
                          // was originally DOMAIN_SEPARATOR
                          // but that has been moved to a method so we can override it in V2_2+
                          bytes32 internal _DEPRECATED_CACHED_DOMAIN_SEPARATOR;
                          /**
                           * @notice Get the EIP712 Domain Separator.
                           * @return The bytes32 EIP712 domain separator.
                           */
                          function DOMAIN_SEPARATOR() external view returns (bytes32) {
                              return _domainSeparator();
                          }
                          /**
                           * @dev Internal method to get the EIP712 Domain Separator.
                           * @return The bytes32 EIP712 domain separator.
                           */
                          function _domainSeparator() internal virtual view returns (bytes32) {
                              return _DEPRECATED_CACHED_DOMAIN_SEPARATOR;
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { AbstractFiatTokenV2 } from "./AbstractFiatTokenV2.sol";
                      import { EIP712Domain } from "./EIP712Domain.sol";
                      import { SignatureChecker } from "../util/SignatureChecker.sol";
                      import { MessageHashUtils } from "../util/MessageHashUtils.sol";
                      /**
                       * @title EIP-3009
                       * @notice Provide internal implementation for gas-abstracted transfers
                       * @dev Contracts that inherit from this must wrap these with publicly
                       * accessible functions, optionally adding modifiers where necessary
                       */
                      abstract contract EIP3009 is AbstractFiatTokenV2, EIP712Domain {
                          // keccak256("TransferWithAuthorization(address from,address to,uint256 value,uint256 validAfter,uint256 validBefore,bytes32 nonce)")
                          bytes32
                              public constant TRANSFER_WITH_AUTHORIZATION_TYPEHASH = 0x7c7c6cdb67a18743f49ec6fa9b35f50d52ed05cbed4cc592e13b44501c1a2267;
                          // keccak256("ReceiveWithAuthorization(address from,address to,uint256 value,uint256 validAfter,uint256 validBefore,bytes32 nonce)")
                          bytes32
                              public constant RECEIVE_WITH_AUTHORIZATION_TYPEHASH = 0xd099cc98ef71107a616c4f0f941f04c322d8e254fe26b3c6668db87aae413de8;
                          // keccak256("CancelAuthorization(address authorizer,bytes32 nonce)")
                          bytes32
                              public constant CANCEL_AUTHORIZATION_TYPEHASH = 0x158b0a9edf7a828aad02f63cd515c68ef2f50ba807396f6d12842833a1597429;
                          /**
                           * @dev authorizer address => nonce => bool (true if nonce is used)
                           */
                          mapping(address => mapping(bytes32 => bool)) private _authorizationStates;
                          event AuthorizationUsed(address indexed authorizer, bytes32 indexed nonce);
                          event AuthorizationCanceled(
                              address indexed authorizer,
                              bytes32 indexed nonce
                          );
                          /**
                           * @notice Returns the state of an authorization
                           * @dev Nonces are randomly generated 32-byte data unique to the
                           * authorizer's address
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           * @return True if the nonce is used
                           */
                          function authorizationState(address authorizer, bytes32 nonce)
                              external
                              view
                              returns (bool)
                          {
                              return _authorizationStates[authorizer][nonce];
                          }
                          /**
                           * @notice Execute a transfer with a signed authorization
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param v             v of the signature
                           * @param r             r of the signature
                           * @param s             s of the signature
                           */
                          function _transferWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) internal {
                              _transferWithAuthorization(
                                  from,
                                  to,
                                  value,
                                  validAfter,
                                  validBefore,
                                  nonce,
                                  abi.encodePacked(r, s, v)
                              );
                          }
                          /**
                           * @notice Execute a transfer with a signed authorization
                           * @dev EOA wallet signatures should be packed in the order of r, s, v.
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
                           */
                          function _transferWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              bytes memory signature
                          ) internal {
                              _requireValidAuthorization(from, nonce, validAfter, validBefore);
                              _requireValidSignature(
                                  from,
                                  keccak256(
                                      abi.encode(
                                          TRANSFER_WITH_AUTHORIZATION_TYPEHASH,
                                          from,
                                          to,
                                          value,
                                          validAfter,
                                          validBefore,
                                          nonce
                                      )
                                  ),
                                  signature
                              );
                              _markAuthorizationAsUsed(from, nonce);
                              _transfer(from, to, value);
                          }
                          /**
                           * @notice Receive a transfer with a signed authorization from the payer
                           * @dev This has an additional check to ensure that the payee's address
                           * matches the caller of this function to prevent front-running attacks.
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param v             v of the signature
                           * @param r             r of the signature
                           * @param s             s of the signature
                           */
                          function _receiveWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) internal {
                              _receiveWithAuthorization(
                                  from,
                                  to,
                                  value,
                                  validAfter,
                                  validBefore,
                                  nonce,
                                  abi.encodePacked(r, s, v)
                              );
                          }
                          /**
                           * @notice Receive a transfer with a signed authorization from the payer
                           * @dev This has an additional check to ensure that the payee's address
                           * matches the caller of this function to prevent front-running attacks.
                           * EOA wallet signatures should be packed in the order of r, s, v.
                           * @param from          Payer's address (Authorizer)
                           * @param to            Payee's address
                           * @param value         Amount to be transferred
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           * @param nonce         Unique nonce
                           * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
                           */
                          function _receiveWithAuthorization(
                              address from,
                              address to,
                              uint256 value,
                              uint256 validAfter,
                              uint256 validBefore,
                              bytes32 nonce,
                              bytes memory signature
                          ) internal {
                              require(to == msg.sender, "FiatTokenV2: caller must be the payee");
                              _requireValidAuthorization(from, nonce, validAfter, validBefore);
                              _requireValidSignature(
                                  from,
                                  keccak256(
                                      abi.encode(
                                          RECEIVE_WITH_AUTHORIZATION_TYPEHASH,
                                          from,
                                          to,
                                          value,
                                          validAfter,
                                          validBefore,
                                          nonce
                                      )
                                  ),
                                  signature
                              );
                              _markAuthorizationAsUsed(from, nonce);
                              _transfer(from, to, value);
                          }
                          /**
                           * @notice Attempt to cancel an authorization
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           * @param v             v of the signature
                           * @param r             r of the signature
                           * @param s             s of the signature
                           */
                          function _cancelAuthorization(
                              address authorizer,
                              bytes32 nonce,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) internal {
                              _cancelAuthorization(authorizer, nonce, abi.encodePacked(r, s, v));
                          }
                          /**
                           * @notice Attempt to cancel an authorization
                           * @dev EOA wallet signatures should be packed in the order of r, s, v.
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
                           */
                          function _cancelAuthorization(
                              address authorizer,
                              bytes32 nonce,
                              bytes memory signature
                          ) internal {
                              _requireUnusedAuthorization(authorizer, nonce);
                              _requireValidSignature(
                                  authorizer,
                                  keccak256(
                                      abi.encode(CANCEL_AUTHORIZATION_TYPEHASH, authorizer, nonce)
                                  ),
                                  signature
                              );
                              _authorizationStates[authorizer][nonce] = true;
                              emit AuthorizationCanceled(authorizer, nonce);
                          }
                          /**
                           * @notice Validates that signature against input data struct
                           * @param signer        Signer's address
                           * @param dataHash      Hash of encoded data struct
                           * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
                           */
                          function _requireValidSignature(
                              address signer,
                              bytes32 dataHash,
                              bytes memory signature
                          ) private view {
                              require(
                                  SignatureChecker.isValidSignatureNow(
                                      signer,
                                      MessageHashUtils.toTypedDataHash(_domainSeparator(), dataHash),
                                      signature
                                  ),
                                  "FiatTokenV2: invalid signature"
                              );
                          }
                          /**
                           * @notice Check that an authorization is unused
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           */
                          function _requireUnusedAuthorization(address authorizer, bytes32 nonce)
                              private
                              view
                          {
                              require(
                                  !_authorizationStates[authorizer][nonce],
                                  "FiatTokenV2: authorization is used or canceled"
                              );
                          }
                          /**
                           * @notice Check that authorization is valid
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           * @param validAfter    The time after which this is valid (unix time)
                           * @param validBefore   The time before which this is valid (unix time)
                           */
                          function _requireValidAuthorization(
                              address authorizer,
                              bytes32 nonce,
                              uint256 validAfter,
                              uint256 validBefore
                          ) private view {
                              require(
                                  now > validAfter,
                                  "FiatTokenV2: authorization is not yet valid"
                              );
                              require(now < validBefore, "FiatTokenV2: authorization is expired");
                              _requireUnusedAuthorization(authorizer, nonce);
                          }
                          /**
                           * @notice Mark an authorization as used
                           * @param authorizer    Authorizer's address
                           * @param nonce         Nonce of the authorization
                           */
                          function _markAuthorizationAsUsed(address authorizer, bytes32 nonce)
                              private
                          {
                              _authorizationStates[authorizer][nonce] = true;
                              emit AuthorizationUsed(authorizer, nonce);
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { AbstractFiatTokenV2 } from "./AbstractFiatTokenV2.sol";
                      import { EIP712Domain } from "./EIP712Domain.sol";
                      import { MessageHashUtils } from "../util/MessageHashUtils.sol";
                      import { SignatureChecker } from "../util/SignatureChecker.sol";
                      /**
                       * @title EIP-2612
                       * @notice Provide internal implementation for gas-abstracted approvals
                       */
                      abstract contract EIP2612 is AbstractFiatTokenV2, EIP712Domain {
                          // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)")
                          bytes32
                              public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
                          mapping(address => uint256) private _permitNonces;
                          /**
                           * @notice Nonces for permit
                           * @param owner Token owner's address (Authorizer)
                           * @return Next nonce
                           */
                          function nonces(address owner) external view returns (uint256) {
                              return _permitNonces[owner];
                          }
                          /**
                           * @notice Verify a signed approval permit and execute if valid
                           * @param owner     Token owner's address (Authorizer)
                           * @param spender   Spender's address
                           * @param value     Amount of allowance
                           * @param deadline  The time at which the signature expires (unix time), or max uint256 value to signal no expiration
                           * @param v         v of the signature
                           * @param r         r of the signature
                           * @param s         s of the signature
                           */
                          function _permit(
                              address owner,
                              address spender,
                              uint256 value,
                              uint256 deadline,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) internal {
                              _permit(owner, spender, value, deadline, abi.encodePacked(r, s, v));
                          }
                          /**
                           * @notice Verify a signed approval permit and execute if valid
                           * @dev EOA wallet signatures should be packed in the order of r, s, v.
                           * @param owner      Token owner's address (Authorizer)
                           * @param spender    Spender's address
                           * @param value      Amount of allowance
                           * @param deadline   The time at which the signature expires (unix time), or max uint256 value to signal no expiration
                           * @param signature  Signature byte array signed by an EOA wallet or a contract wallet
                           */
                          function _permit(
                              address owner,
                              address spender,
                              uint256 value,
                              uint256 deadline,
                              bytes memory signature
                          ) internal {
                              require(
                                  deadline == type(uint256).max || deadline >= now,
                                  "FiatTokenV2: permit is expired"
                              );
                              bytes32 typedDataHash = MessageHashUtils.toTypedDataHash(
                                  _domainSeparator(),
                                  keccak256(
                                      abi.encode(
                                          PERMIT_TYPEHASH,
                                          owner,
                                          spender,
                                          value,
                                          _permitNonces[owner]++,
                                          deadline
                                      )
                                  )
                              );
                              require(
                                  SignatureChecker.isValidSignatureNow(
                                      owner,
                                      typedDataHash,
                                      signature
                                  ),
                                  "EIP2612: invalid signature"
                              );
                              _approve(owner, spender, value);
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { AbstractFiatTokenV1 } from "../v1/AbstractFiatTokenV1.sol";
                      abstract contract AbstractFiatTokenV2 is AbstractFiatTokenV1 {
                          function _increaseAllowance(
                              address owner,
                              address spender,
                              uint256 increment
                          ) internal virtual;
                          function _decreaseAllowance(
                              address owner,
                              address spender,
                              uint256 decrement
                          ) internal virtual;
                      }
                      /**
                       * SPDX-License-Identifier: MIT
                       *
                       * Copyright (c) 2016 Smart Contract Solutions, Inc.
                       * Copyright (c) 2018-2020 CENTRE SECZ
                       *
                       * Permission is hereby granted, free of charge, to any person obtaining a copy
                       * of this software and associated documentation files (the "Software"), to deal
                       * in the Software without restriction, including without limitation the rights
                       * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
                       * copies of the Software, and to permit persons to whom the Software is
                       * furnished to do so, subject to the following conditions:
                       *
                       * The above copyright notice and this permission notice shall be included in
                       * copies or substantial portions of the Software.
                       *
                       * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
                       * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
                       * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
                       * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
                       * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
                       * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
                       * SOFTWARE.
                       */
                      pragma solidity 0.6.12;
                      import { Ownable } from "./Ownable.sol";
                      /**
                       * @notice Base contract which allows children to implement an emergency stop
                       * mechanism
                       * @dev Forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/feb665136c0dae9912e08397c1a21c4af3651ef3/contracts/lifecycle/Pausable.sol
                       * Modifications:
                       * 1. Added pauser role, switched pause/unpause to be onlyPauser (6/14/2018)
                       * 2. Removed whenNotPause/whenPaused from pause/unpause (6/14/2018)
                       * 3. Removed whenPaused (6/14/2018)
                       * 4. Switches ownable library to use ZeppelinOS (7/12/18)
                       * 5. Remove constructor (7/13/18)
                       * 6. Reformat, conform to Solidity 0.6 syntax and add error messages (5/13/20)
                       * 7. Make public functions external (5/27/20)
                       */
                      contract Pausable is Ownable {
                          event Pause();
                          event Unpause();
                          event PauserChanged(address indexed newAddress);
                          address public pauser;
                          bool public paused = false;
                          /**
                           * @dev Modifier to make a function callable only when the contract is not paused.
                           */
                          modifier whenNotPaused() {
                              require(!paused, "Pausable: paused");
                              _;
                          }
                          /**
                           * @dev throws if called by any account other than the pauser
                           */
                          modifier onlyPauser() {
                              require(msg.sender == pauser, "Pausable: caller is not the pauser");
                              _;
                          }
                          /**
                           * @dev called by the owner to pause, triggers stopped state
                           */
                          function pause() external onlyPauser {
                              paused = true;
                              emit Pause();
                          }
                          /**
                           * @dev called by the owner to unpause, returns to normal state
                           */
                          function unpause() external onlyPauser {
                              paused = false;
                              emit Unpause();
                          }
                          /**
                           * @notice Updates the pauser address.
                           * @param _newPauser The address of the new pauser.
                           */
                          function updatePauser(address _newPauser) external onlyOwner {
                              require(
                                  _newPauser != address(0),
                                  "Pausable: new pauser is the zero address"
                              );
                              pauser = _newPauser;
                              emit PauserChanged(pauser);
                          }
                      }
                      /**
                       * SPDX-License-Identifier: MIT
                       *
                       * Copyright (c) 2018 zOS Global Limited.
                       * Copyright (c) 2018-2020 CENTRE SECZ
                       *
                       * Permission is hereby granted, free of charge, to any person obtaining a copy
                       * of this software and associated documentation files (the "Software"), to deal
                       * in the Software without restriction, including without limitation the rights
                       * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
                       * copies of the Software, and to permit persons to whom the Software is
                       * furnished to do so, subject to the following conditions:
                       *
                       * The above copyright notice and this permission notice shall be included in
                       * copies or substantial portions of the Software.
                       *
                       * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
                       * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
                       * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
                       * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
                       * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
                       * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
                       * SOFTWARE.
                       */
                      pragma solidity 0.6.12;
                      /**
                       * @notice The Ownable contract has an owner address, and provides basic
                       * authorization control functions
                       * @dev Forked from https://github.com/OpenZeppelin/openzeppelin-labs/blob/3887ab77b8adafba4a26ace002f3a684c1a3388b/upgradeability_ownership/contracts/ownership/Ownable.sol
                       * Modifications:
                       * 1. Consolidate OwnableStorage into this contract (7/13/18)
                       * 2. Reformat, conform to Solidity 0.6 syntax, and add error messages (5/13/20)
                       * 3. Make public functions external (5/27/20)
                       */
                      contract Ownable {
                          // Owner of the contract
                          address private _owner;
                          /**
                           * @dev Event to show ownership has been transferred
                           * @param previousOwner representing the address of the previous owner
                           * @param newOwner representing the address of the new owner
                           */
                          event OwnershipTransferred(address previousOwner, address newOwner);
                          /**
                           * @dev The constructor sets the original owner of the contract to the sender account.
                           */
                          constructor() public {
                              setOwner(msg.sender);
                          }
                          /**
                           * @dev Tells the address of the owner
                           * @return the address of the owner
                           */
                          function owner() external view returns (address) {
                              return _owner;
                          }
                          /**
                           * @dev Sets a new owner address
                           */
                          function setOwner(address newOwner) internal {
                              _owner = newOwner;
                          }
                          /**
                           * @dev Throws if called by any account other than the owner.
                           */
                          modifier onlyOwner() {
                              require(msg.sender == _owner, "Ownable: caller is not the owner");
                              _;
                          }
                          /**
                           * @dev Allows the current owner to transfer control of the contract to a newOwner.
                           * @param newOwner The address to transfer ownership to.
                           */
                          function transferOwnership(address newOwner) external onlyOwner {
                              require(
                                  newOwner != address(0),
                                  "Ownable: new owner is the zero address"
                              );
                              emit OwnershipTransferred(_owner, newOwner);
                              setOwner(newOwner);
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
                      import { AbstractFiatTokenV1 } from "./AbstractFiatTokenV1.sol";
                      import { Ownable } from "./Ownable.sol";
                      import { Pausable } from "./Pausable.sol";
                      import { Blacklistable } from "./Blacklistable.sol";
                      /**
                       * @title FiatToken
                       * @dev ERC20 Token backed by fiat reserves
                       */
                      contract FiatTokenV1 is AbstractFiatTokenV1, Ownable, Pausable, Blacklistable {
                          using SafeMath for uint256;
                          string public name;
                          string public symbol;
                          uint8 public decimals;
                          string public currency;
                          address public masterMinter;
                          bool internal initialized;
                          /// @dev A mapping that stores the balance and blacklist states for a given address.
                          /// The first bit defines whether the address is blacklisted (1 if blacklisted, 0 otherwise).
                          /// The last 255 bits define the balance for the address.
                          mapping(address => uint256) internal balanceAndBlacklistStates;
                          mapping(address => mapping(address => uint256)) internal allowed;
                          uint256 internal totalSupply_ = 0;
                          mapping(address => bool) internal minters;
                          mapping(address => uint256) internal minterAllowed;
                          event Mint(address indexed minter, address indexed to, uint256 amount);
                          event Burn(address indexed burner, uint256 amount);
                          event MinterConfigured(address indexed minter, uint256 minterAllowedAmount);
                          event MinterRemoved(address indexed oldMinter);
                          event MasterMinterChanged(address indexed newMasterMinter);
                          /**
                           * @notice Initializes the fiat token contract.
                           * @param tokenName       The name of the fiat token.
                           * @param tokenSymbol     The symbol of the fiat token.
                           * @param tokenCurrency   The fiat currency that the token represents.
                           * @param tokenDecimals   The number of decimals that the token uses.
                           * @param newMasterMinter The masterMinter address for the fiat token.
                           * @param newPauser       The pauser address for the fiat token.
                           * @param newBlacklister  The blacklister address for the fiat token.
                           * @param newOwner        The owner of the fiat token.
                           */
                          function initialize(
                              string memory tokenName,
                              string memory tokenSymbol,
                              string memory tokenCurrency,
                              uint8 tokenDecimals,
                              address newMasterMinter,
                              address newPauser,
                              address newBlacklister,
                              address newOwner
                          ) public {
                              require(!initialized, "FiatToken: contract is already initialized");
                              require(
                                  newMasterMinter != address(0),
                                  "FiatToken: new masterMinter is the zero address"
                              );
                              require(
                                  newPauser != address(0),
                                  "FiatToken: new pauser is the zero address"
                              );
                              require(
                                  newBlacklister != address(0),
                                  "FiatToken: new blacklister is the zero address"
                              );
                              require(
                                  newOwner != address(0),
                                  "FiatToken: new owner is the zero address"
                              );
                              name = tokenName;
                              symbol = tokenSymbol;
                              currency = tokenCurrency;
                              decimals = tokenDecimals;
                              masterMinter = newMasterMinter;
                              pauser = newPauser;
                              blacklister = newBlacklister;
                              setOwner(newOwner);
                              initialized = true;
                          }
                          /**
                           * @dev Throws if called by any account other than a minter.
                           */
                          modifier onlyMinters() {
                              require(minters[msg.sender], "FiatToken: caller is not a minter");
                              _;
                          }
                          /**
                           * @notice Mints fiat tokens to an address.
                           * @param _to The address that will receive the minted tokens.
                           * @param _amount The amount of tokens to mint. Must be less than or equal
                           * to the minterAllowance of the caller.
                           * @return True if the operation was successful.
                           */
                          function mint(address _to, uint256 _amount)
                              external
                              whenNotPaused
                              onlyMinters
                              notBlacklisted(msg.sender)
                              notBlacklisted(_to)
                              returns (bool)
                          {
                              require(_to != address(0), "FiatToken: mint to the zero address");
                              require(_amount > 0, "FiatToken: mint amount not greater than 0");
                              uint256 mintingAllowedAmount = minterAllowed[msg.sender];
                              require(
                                  _amount <= mintingAllowedAmount,
                                  "FiatToken: mint amount exceeds minterAllowance"
                              );
                              totalSupply_ = totalSupply_.add(_amount);
                              _setBalance(_to, _balanceOf(_to).add(_amount));
                              minterAllowed[msg.sender] = mintingAllowedAmount.sub(_amount);
                              emit Mint(msg.sender, _to, _amount);
                              emit Transfer(address(0), _to, _amount);
                              return true;
                          }
                          /**
                           * @dev Throws if called by any account other than the masterMinter
                           */
                          modifier onlyMasterMinter() {
                              require(
                                  msg.sender == masterMinter,
                                  "FiatToken: caller is not the masterMinter"
                              );
                              _;
                          }
                          /**
                           * @notice Gets the minter allowance for an account.
                           * @param minter The address to check.
                           * @return The remaining minter allowance for the account.
                           */
                          function minterAllowance(address minter) external view returns (uint256) {
                              return minterAllowed[minter];
                          }
                          /**
                           * @notice Checks if an account is a minter.
                           * @param account The address to check.
                           * @return True if the account is a minter, false if the account is not a minter.
                           */
                          function isMinter(address account) external view returns (bool) {
                              return minters[account];
                          }
                          /**
                           * @notice Gets the remaining amount of fiat tokens a spender is allowed to transfer on
                           * behalf of the token owner.
                           * @param owner   The token owner's address.
                           * @param spender The spender's address.
                           * @return The remaining allowance.
                           */
                          function allowance(address owner, address spender)
                              external
                              override
                              view
                              returns (uint256)
                          {
                              return allowed[owner][spender];
                          }
                          /**
                           * @notice Gets the totalSupply of the fiat token.
                           * @return The totalSupply of the fiat token.
                           */
                          function totalSupply() external override view returns (uint256) {
                              return totalSupply_;
                          }
                          /**
                           * @notice Gets the fiat token balance of an account.
                           * @param account  The address to check.
                           * @return balance The fiat token balance of the account.
                           */
                          function balanceOf(address account)
                              external
                              override
                              view
                              returns (uint256)
                          {
                              return _balanceOf(account);
                          }
                          /**
                           * @notice Sets a fiat token allowance for a spender to spend on behalf of the caller.
                           * @param spender The spender's address.
                           * @param value   The allowance amount.
                           * @return True if the operation was successful.
                           */
                          function approve(address spender, uint256 value)
                              external
                              virtual
                              override
                              whenNotPaused
                              notBlacklisted(msg.sender)
                              notBlacklisted(spender)
                              returns (bool)
                          {
                              _approve(msg.sender, spender, value);
                              return true;
                          }
                          /**
                           * @dev Internal function to set allowance.
                           * @param owner     Token owner's address.
                           * @param spender   Spender's address.
                           * @param value     Allowance amount.
                           */
                          function _approve(
                              address owner,
                              address spender,
                              uint256 value
                          ) internal override {
                              require(owner != address(0), "ERC20: approve from the zero address");
                              require(spender != address(0), "ERC20: approve to the zero address");
                              allowed[owner][spender] = value;
                              emit Approval(owner, spender, value);
                          }
                          /**
                           * @notice Transfers tokens from an address to another by spending the caller's allowance.
                           * @dev The caller must have some fiat token allowance on the payer's tokens.
                           * @param from  Payer's address.
                           * @param to    Payee's address.
                           * @param value Transfer amount.
                           * @return True if the operation was successful.
                           */
                          function transferFrom(
                              address from,
                              address to,
                              uint256 value
                          )
                              external
                              override
                              whenNotPaused
                              notBlacklisted(msg.sender)
                              notBlacklisted(from)
                              notBlacklisted(to)
                              returns (bool)
                          {
                              require(
                                  value <= allowed[from][msg.sender],
                                  "ERC20: transfer amount exceeds allowance"
                              );
                              _transfer(from, to, value);
                              allowed[from][msg.sender] = allowed[from][msg.sender].sub(value);
                              return true;
                          }
                          /**
                           * @notice Transfers tokens from the caller.
                           * @param to    Payee's address.
                           * @param value Transfer amount.
                           * @return True if the operation was successful.
                           */
                          function transfer(address to, uint256 value)
                              external
                              override
                              whenNotPaused
                              notBlacklisted(msg.sender)
                              notBlacklisted(to)
                              returns (bool)
                          {
                              _transfer(msg.sender, to, value);
                              return true;
                          }
                          /**
                           * @dev Internal function to process transfers.
                           * @param from  Payer's address.
                           * @param to    Payee's address.
                           * @param value Transfer amount.
                           */
                          function _transfer(
                              address from,
                              address to,
                              uint256 value
                          ) internal override {
                              require(from != address(0), "ERC20: transfer from the zero address");
                              require(to != address(0), "ERC20: transfer to the zero address");
                              require(
                                  value <= _balanceOf(from),
                                  "ERC20: transfer amount exceeds balance"
                              );
                              _setBalance(from, _balanceOf(from).sub(value));
                              _setBalance(to, _balanceOf(to).add(value));
                              emit Transfer(from, to, value);
                          }
                          /**
                           * @notice Adds or updates a new minter with a mint allowance.
                           * @param minter The address of the minter.
                           * @param minterAllowedAmount The minting amount allowed for the minter.
                           * @return True if the operation was successful.
                           */
                          function configureMinter(address minter, uint256 minterAllowedAmount)
                              external
                              whenNotPaused
                              onlyMasterMinter
                              returns (bool)
                          {
                              minters[minter] = true;
                              minterAllowed[minter] = minterAllowedAmount;
                              emit MinterConfigured(minter, minterAllowedAmount);
                              return true;
                          }
                          /**
                           * @notice Removes a minter.
                           * @param minter The address of the minter to remove.
                           * @return True if the operation was successful.
                           */
                          function removeMinter(address minter)
                              external
                              onlyMasterMinter
                              returns (bool)
                          {
                              minters[minter] = false;
                              minterAllowed[minter] = 0;
                              emit MinterRemoved(minter);
                              return true;
                          }
                          /**
                           * @notice Allows a minter to burn some of its own tokens.
                           * @dev The caller must be a minter, must not be blacklisted, and the amount to burn
                           * should be less than or equal to the account's balance.
                           * @param _amount the amount of tokens to be burned.
                           */
                          function burn(uint256 _amount)
                              external
                              whenNotPaused
                              onlyMinters
                              notBlacklisted(msg.sender)
                          {
                              uint256 balance = _balanceOf(msg.sender);
                              require(_amount > 0, "FiatToken: burn amount not greater than 0");
                              require(balance >= _amount, "FiatToken: burn amount exceeds balance");
                              totalSupply_ = totalSupply_.sub(_amount);
                              _setBalance(msg.sender, balance.sub(_amount));
                              emit Burn(msg.sender, _amount);
                              emit Transfer(msg.sender, address(0), _amount);
                          }
                          /**
                           * @notice Updates the master minter address.
                           * @param _newMasterMinter The address of the new master minter.
                           */
                          function updateMasterMinter(address _newMasterMinter) external onlyOwner {
                              require(
                                  _newMasterMinter != address(0),
                                  "FiatToken: new masterMinter is the zero address"
                              );
                              masterMinter = _newMasterMinter;
                              emit MasterMinterChanged(masterMinter);
                          }
                          /**
                           * @inheritdoc Blacklistable
                           */
                          function _blacklist(address _account) internal override {
                              _setBlacklistState(_account, true);
                          }
                          /**
                           * @inheritdoc Blacklistable
                           */
                          function _unBlacklist(address _account) internal override {
                              _setBlacklistState(_account, false);
                          }
                          /**
                           * @dev Helper method that sets the blacklist state of an account.
                           * @param _account         The address of the account.
                           * @param _shouldBlacklist True if the account should be blacklisted, false if the account should be unblacklisted.
                           */
                          function _setBlacklistState(address _account, bool _shouldBlacklist)
                              internal
                              virtual
                          {
                              _deprecatedBlacklisted[_account] = _shouldBlacklist;
                          }
                          /**
                           * @dev Helper method that sets the balance of an account.
                           * @param _account The address of the account.
                           * @param _balance The new fiat token balance of the account.
                           */
                          function _setBalance(address _account, uint256 _balance) internal virtual {
                              balanceAndBlacklistStates[_account] = _balance;
                          }
                          /**
                           * @inheritdoc Blacklistable
                           */
                          function _isBlacklisted(address _account)
                              internal
                              virtual
                              override
                              view
                              returns (bool)
                          {
                              return _deprecatedBlacklisted[_account];
                          }
                          /**
                           * @dev Helper method to obtain the balance of an account.
                           * @param _account  The address of the account.
                           * @return          The fiat token balance of the account.
                           */
                          function _balanceOf(address _account)
                              internal
                              virtual
                              view
                              returns (uint256)
                          {
                              return balanceAndBlacklistStates[_account];
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { Ownable } from "./Ownable.sol";
                      /**
                       * @title Blacklistable Token
                       * @dev Allows accounts to be blacklisted by a "blacklister" role
                       */
                      abstract contract Blacklistable is Ownable {
                          address public blacklister;
                          mapping(address => bool) internal _deprecatedBlacklisted;
                          event Blacklisted(address indexed _account);
                          event UnBlacklisted(address indexed _account);
                          event BlacklisterChanged(address indexed newBlacklister);
                          /**
                           * @dev Throws if called by any account other than the blacklister.
                           */
                          modifier onlyBlacklister() {
                              require(
                                  msg.sender == blacklister,
                                  "Blacklistable: caller is not the blacklister"
                              );
                              _;
                          }
                          /**
                           * @dev Throws if argument account is blacklisted.
                           * @param _account The address to check.
                           */
                          modifier notBlacklisted(address _account) {
                              require(
                                  !_isBlacklisted(_account),
                                  "Blacklistable: account is blacklisted"
                              );
                              _;
                          }
                          /**
                           * @notice Checks if account is blacklisted.
                           * @param _account The address to check.
                           * @return True if the account is blacklisted, false if the account is not blacklisted.
                           */
                          function isBlacklisted(address _account) external view returns (bool) {
                              return _isBlacklisted(_account);
                          }
                          /**
                           * @notice Adds account to blacklist.
                           * @param _account The address to blacklist.
                           */
                          function blacklist(address _account) external onlyBlacklister {
                              _blacklist(_account);
                              emit Blacklisted(_account);
                          }
                          /**
                           * @notice Removes account from blacklist.
                           * @param _account The address to remove from the blacklist.
                           */
                          function unBlacklist(address _account) external onlyBlacklister {
                              _unBlacklist(_account);
                              emit UnBlacklisted(_account);
                          }
                          /**
                           * @notice Updates the blacklister address.
                           * @param _newBlacklister The address of the new blacklister.
                           */
                          function updateBlacklister(address _newBlacklister) external onlyOwner {
                              require(
                                  _newBlacklister != address(0),
                                  "Blacklistable: new blacklister is the zero address"
                              );
                              blacklister = _newBlacklister;
                              emit BlacklisterChanged(blacklister);
                          }
                          /**
                           * @dev Checks if account is blacklisted.
                           * @param _account The address to check.
                           * @return true if the account is blacklisted, false otherwise.
                           */
                          function _isBlacklisted(address _account)
                              internal
                              virtual
                              view
                              returns (bool);
                          /**
                           * @dev Helper method that blacklists an account.
                           * @param _account The address to blacklist.
                           */
                          function _blacklist(address _account) internal virtual;
                          /**
                           * @dev Helper method that unblacklists an account.
                           * @param _account The address to unblacklist.
                           */
                          function _unBlacklist(address _account) internal virtual;
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      abstract contract AbstractFiatTokenV1 is IERC20 {
                          function _approve(
                              address owner,
                              address spender,
                              uint256 value
                          ) internal virtual;
                          function _transfer(
                              address from,
                              address to,
                              uint256 value
                          ) internal virtual;
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { Ownable } from "../v1/Ownable.sol";
                      import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
                      import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
                      contract Rescuable is Ownable {
                          using SafeERC20 for IERC20;
                          address private _rescuer;
                          event RescuerChanged(address indexed newRescuer);
                          /**
                           * @notice Returns current rescuer
                           * @return Rescuer's address
                           */
                          function rescuer() external view returns (address) {
                              return _rescuer;
                          }
                          /**
                           * @notice Revert if called by any account other than the rescuer.
                           */
                          modifier onlyRescuer() {
                              require(msg.sender == _rescuer, "Rescuable: caller is not the rescuer");
                              _;
                          }
                          /**
                           * @notice Rescue ERC20 tokens locked up in this contract.
                           * @param tokenContract ERC20 token contract address
                           * @param to        Recipient address
                           * @param amount    Amount to withdraw
                           */
                          function rescueERC20(
                              IERC20 tokenContract,
                              address to,
                              uint256 amount
                          ) external onlyRescuer {
                              tokenContract.safeTransfer(to, amount);
                          }
                          /**
                           * @notice Updates the rescuer address.
                           * @param newRescuer The address of the new rescuer.
                           */
                          function updateRescuer(address newRescuer) external onlyOwner {
                              require(
                                  newRescuer != address(0),
                                  "Rescuable: new rescuer is the zero address"
                              );
                              _rescuer = newRescuer;
                              emit RescuerChanged(newRescuer);
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { FiatTokenV1 } from "../v1/FiatTokenV1.sol";
                      import { Rescuable } from "./Rescuable.sol";
                      /**
                       * @title FiatTokenV1_1
                       * @dev ERC20 Token backed by fiat reserves
                       */
                      contract FiatTokenV1_1 is FiatTokenV1, Rescuable {
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      import { ECRecover } from "./ECRecover.sol";
                      import { IERC1271 } from "../interface/IERC1271.sol";
                      /**
                       * @dev Signature verification helper that can be used instead of `ECRecover.recover` to seamlessly support both ECDSA
                       * signatures from externally owned accounts (EOAs) as well as ERC1271 signatures from smart contract wallets.
                       *
                       * Adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/21bb89ef5bfc789b9333eb05e3ba2b7b284ac77c/contracts/utils/cryptography/SignatureChecker.sol
                       */
                      library SignatureChecker {
                          /**
                           * @dev Checks if a signature is valid for a given signer and data hash. If the signer is a smart contract, the
                           * signature is validated against that smart contract using ERC1271, otherwise it's validated using `ECRecover.recover`.
                           * @param signer        Address of the claimed signer
                           * @param digest        Keccak-256 hash digest of the signed message
                           * @param signature     Signature byte array associated with hash
                           */
                          function isValidSignatureNow(
                              address signer,
                              bytes32 digest,
                              bytes memory signature
                          ) external view returns (bool) {
                              if (!isContract(signer)) {
                                  return ECRecover.recover(digest, signature) == signer;
                              }
                              return isValidERC1271SignatureNow(signer, digest, signature);
                          }
                          /**
                           * @dev Checks if a signature is valid for a given signer and data hash. The signature is validated
                           * against the signer smart contract using ERC1271.
                           * @param signer        Address of the claimed signer
                           * @param digest        Keccak-256 hash digest of the signed message
                           * @param signature     Signature byte array associated with hash
                           *
                           * NOTE: Unlike ECDSA signatures, contract signatures are revocable, and the outcome of this function can thus
                           * change through time. It could return true at block N and false at block N+1 (or the opposite).
                           */
                          function isValidERC1271SignatureNow(
                              address signer,
                              bytes32 digest,
                              bytes memory signature
                          ) internal view returns (bool) {
                              (bool success, bytes memory result) = signer.staticcall(
                                  abi.encodeWithSelector(
                                      IERC1271.isValidSignature.selector,
                                      digest,
                                      signature
                                  )
                              );
                              return (success &&
                                  result.length >= 32 &&
                                  abi.decode(result, (bytes32)) ==
                                  bytes32(IERC1271.isValidSignature.selector));
                          }
                          /**
                           * @dev Checks if the input address is a smart contract.
                           */
                          function isContract(address addr) internal view returns (bool) {
                              uint256 size;
                              assembly {
                                  size := extcodesize(addr)
                              }
                              return size > 0;
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      /**
                       * @dev Signature message hash utilities for producing digests to be consumed by {ECDSA} recovery or signing.
                       *
                       * The library provides methods for generating a hash of a message that conforms to the
                       * https://eips.ethereum.org/EIPS/eip-191[EIP 191] and https://eips.ethereum.org/EIPS/eip-712[EIP 712]
                       * specifications.
                       */
                      library MessageHashUtils {
                          /**
                           * @dev Returns the keccak256 digest of an EIP-712 typed data (EIP-191 version `0x01`).
                           * Adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/21bb89ef5bfc789b9333eb05e3ba2b7b284ac77c/contracts/utils/cryptography/MessageHashUtils.sol
                           *
                           * The digest is calculated from a `domainSeparator` and a `structHash`, by prefixing them with
                           * `\\x19\\x01` and hashing the result. It corresponds to the hash signed by the
                           * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`] JSON-RPC method as part of EIP-712.
                           *
                           * @param domainSeparator    Domain separator
                           * @param structHash         Hashed EIP-712 data struct
                           * @return digest            The keccak256 digest of an EIP-712 typed data
                           */
                          function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash)
                              internal
                              pure
                              returns (bytes32 digest)
                          {
                              assembly {
                                  let ptr := mload(0x40)
                                  mstore(ptr, "\\x19\\x01")
                                  mstore(add(ptr, 0x02), domainSeparator)
                                  mstore(add(ptr, 0x22), structHash)
                                  digest := keccak256(ptr, 0x42)
                              }
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      /**
                       * @title EIP712
                       * @notice A library that provides EIP712 helper functions
                       */
                      library EIP712 {
                          /**
                           * @notice Make EIP712 domain separator
                           * @param name      Contract name
                           * @param version   Contract version
                           * @param chainId   Blockchain ID
                           * @return Domain separator
                           */
                          function makeDomainSeparator(
                              string memory name,
                              string memory version,
                              uint256 chainId
                          ) internal view returns (bytes32) {
                              return
                                  keccak256(
                                      abi.encode(
                                          // keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)")
                                          0x8b73c3c69bb8fe3d512ecc4cf759cc79239f7b179b0ffacaa9a75d522b39400f,
                                          keccak256(bytes(name)),
                                          keccak256(bytes(version)),
                                          chainId,
                                          address(this)
                                      )
                                  );
                          }
                          /**
                           * @notice Make EIP712 domain separator
                           * @param name      Contract name
                           * @param version   Contract version
                           * @return Domain separator
                           */
                          function makeDomainSeparator(string memory name, string memory version)
                              internal
                              view
                              returns (bytes32)
                          {
                              uint256 chainId;
                              assembly {
                                  chainId := chainid()
                              }
                              return makeDomainSeparator(name, version, chainId);
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      /**
                       * @title ECRecover
                       * @notice A library that provides a safe ECDSA recovery function
                       */
                      library ECRecover {
                          /**
                           * @notice Recover signer's address from a signed message
                           * @dev Adapted from: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/65e4ffde586ec89af3b7e9140bdc9235d1254853/contracts/cryptography/ECDSA.sol
                           * Modifications: Accept v, r, and s as separate arguments
                           * @param digest    Keccak-256 hash digest of the signed message
                           * @param v         v of the signature
                           * @param r         r of the signature
                           * @param s         s of the signature
                           * @return Signer address
                           */
                          function recover(
                              bytes32 digest,
                              uint8 v,
                              bytes32 r,
                              bytes32 s
                          ) internal pure returns (address) {
                              // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
                              // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
                              // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
                              // signatures from current libraries generate a unique signature with an s-value in the lower half order.
                              //
                              // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
                              // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
                              // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
                              // these malleable signatures as well.
                              if (
                                  uint256(s) >
                                  0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0
                              ) {
                                  revert("ECRecover: invalid signature 's' value");
                              }
                              if (v != 27 && v != 28) {
                                  revert("ECRecover: invalid signature 'v' value");
                              }
                              // If the signature is valid (and not malleable), return the signer address
                              address signer = ecrecover(digest, v, r, s);
                              require(signer != address(0), "ECRecover: invalid signature");
                              return signer;
                          }
                          /**
                           * @notice Recover signer's address from a signed message
                           * @dev Adapted from: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/0053ee040a7ff1dbc39691c9e67a69f564930a88/contracts/utils/cryptography/ECDSA.sol
                           * @param digest    Keccak-256 hash digest of the signed message
                           * @param signature Signature byte array associated with hash
                           * @return Signer address
                           */
                          function recover(bytes32 digest, bytes memory signature)
                              internal
                              pure
                              returns (address)
                          {
                              require(signature.length == 65, "ECRecover: invalid signature length");
                              bytes32 r;
                              bytes32 s;
                              uint8 v;
                              // ecrecover takes the signature parameters, and the only way to get them
                              // currently is to use assembly.
                              /// @solidity memory-safe-assembly
                              assembly {
                                  r := mload(add(signature, 0x20))
                                  s := mload(add(signature, 0x40))
                                  v := byte(0, mload(add(signature, 0x60)))
                              }
                              return recover(digest, v, r, s);
                          }
                      }
                      /**
                       * SPDX-License-Identifier: Apache-2.0
                       *
                       * Copyright (c) 2023, Circle Internet Financial, LLC.
                       *
                       * Licensed under the Apache License, Version 2.0 (the "License");
                       * you may not use this file except in compliance with the License.
                       * You may obtain a copy of the License at
                       *
                       * http://www.apache.org/licenses/LICENSE-2.0
                       *
                       * Unless required by applicable law or agreed to in writing, software
                       * distributed under the License is distributed on an "AS IS" BASIS,
                       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                       * See the License for the specific language governing permissions and
                       * limitations under the License.
                       */
                      pragma solidity 0.6.12;
                      /**
                       * @dev Interface of the ERC1271 standard signature validation method for
                       * contracts as defined in https://eips.ethereum.org/EIPS/eip-1271[ERC-1271].
                       */
                      interface IERC1271 {
                          /**
                           * @dev Should return whether the signature provided is valid for the provided data
                           * @param hash          Hash of the data to be signed
                           * @param signature     Signature byte array associated with the provided data hash
                           * @return magicValue   bytes4 magic value 0x1626ba7e when function passes
                           */
                          function isValidSignature(bytes32 hash, bytes memory signature)
                              external
                              view
                              returns (bytes4 magicValue);
                      }
                      

                      File 7 of 7: NativeOrdersFeature
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2021 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "../migrations/LibMigrate.sol";
                      import "./interfaces/IFeature.sol";
                      import "./interfaces/INativeOrdersFeature.sol";
                      import "./native_orders/NativeOrdersSettlement.sol";
                      /// @dev Feature for interacting with limit and RFQ orders.
                      contract NativeOrdersFeature is
                          IFeature,
                          NativeOrdersSettlement
                      {
                          /// @dev Name of this feature.
                          string public constant override FEATURE_NAME = "LimitOrders";
                          /// @dev Version of this feature.
                          uint256 public immutable override FEATURE_VERSION = _encodeVersion(1, 3, 0);
                          constructor(
                              address zeroExAddress,
                              IEtherTokenV06 weth,
                              IStaking staking,
                              FeeCollectorController feeCollectorController,
                              uint32 protocolFeeMultiplier
                          )
                              public
                              NativeOrdersSettlement(
                                  zeroExAddress,
                                  weth,
                                  staking,
                                  feeCollectorController,
                                  protocolFeeMultiplier
                              )
                          {
                              // solhint-disable no-empty-blocks
                          }
                          /// @dev Initialize and register this feature.
                          ///      Should be delegatecalled by `Migrate.migrate()`.
                          /// @return success `LibMigrate.SUCCESS` on success.
                          function migrate()
                              external
                              returns (bytes4 success)
                          {
                              _registerFeatureFunction(this.transferProtocolFeesForPools.selector);
                              _registerFeatureFunction(this.fillLimitOrder.selector);
                              _registerFeatureFunction(this.fillRfqOrder.selector);
                              _registerFeatureFunction(this.fillOrKillLimitOrder.selector);
                              _registerFeatureFunction(this.fillOrKillRfqOrder.selector);
                              _registerFeatureFunction(this._fillLimitOrder.selector);
                              _registerFeatureFunction(this._fillRfqOrder.selector);
                              _registerFeatureFunction(this.cancelLimitOrder.selector);
                              _registerFeatureFunction(this.cancelRfqOrder.selector);
                              _registerFeatureFunction(this.batchCancelLimitOrders.selector);
                              _registerFeatureFunction(this.batchCancelRfqOrders.selector);
                              _registerFeatureFunction(this.cancelPairLimitOrders.selector);
                              _registerFeatureFunction(this.cancelPairLimitOrdersWithSigner.selector);
                              _registerFeatureFunction(this.batchCancelPairLimitOrders.selector);
                              _registerFeatureFunction(this.batchCancelPairLimitOrdersWithSigner.selector);
                              _registerFeatureFunction(this.cancelPairRfqOrders.selector);
                              _registerFeatureFunction(this.cancelPairRfqOrdersWithSigner.selector);
                              _registerFeatureFunction(this.batchCancelPairRfqOrders.selector);
                              _registerFeatureFunction(this.batchCancelPairRfqOrdersWithSigner.selector);
                              _registerFeatureFunction(this.getLimitOrderInfo.selector);
                              _registerFeatureFunction(this.getRfqOrderInfo.selector);
                              _registerFeatureFunction(this.getLimitOrderHash.selector);
                              _registerFeatureFunction(this.getRfqOrderHash.selector);
                              _registerFeatureFunction(this.getProtocolFeeMultiplier.selector);
                              _registerFeatureFunction(this.registerAllowedRfqOrigins.selector);
                              _registerFeatureFunction(this.getLimitOrderRelevantState.selector);
                              _registerFeatureFunction(this.getRfqOrderRelevantState.selector);
                              _registerFeatureFunction(this.batchGetLimitOrderRelevantStates.selector);
                              _registerFeatureFunction(this.batchGetRfqOrderRelevantStates.selector);
                              _registerFeatureFunction(this.registerAllowedOrderSigner.selector);
                              _registerFeatureFunction(this.isValidOrderSigner.selector);
                              return LibMigrate.MIGRATE_SUCCESS;
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../errors/LibOwnableRichErrors.sol";
                      library LibMigrate {
                          /// @dev Magic bytes returned by a migrator to indicate success.
                          ///      This is `keccack('MIGRATE_SUCCESS')`.
                          bytes4 internal constant MIGRATE_SUCCESS = 0x2c64c5ef;
                          using LibRichErrorsV06 for bytes;
                          /// @dev Perform a delegatecall and ensure it returns the magic bytes.
                          /// @param target The call target.
                          /// @param data The call data.
                          function delegatecallMigrateFunction(
                              address target,
                              bytes memory data
                          )
                              internal
                          {
                              (bool success, bytes memory resultData) = target.delegatecall(data);
                              if (!success ||
                                  resultData.length != 32 ||
                                  abi.decode(resultData, (bytes4)) != MIGRATE_SUCCESS)
                              {
                                  LibOwnableRichErrors.MigrateCallFailedError(target, resultData).rrevert();
                              }
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibRichErrorsV06 {
                          // bytes4(keccak256("Error(string)"))
                          bytes4 internal constant STANDARD_ERROR_SELECTOR = 0x08c379a0;
                          // solhint-disable func-name-mixedcase
                          /// @dev ABI encode a standard, string revert error payload.
                          ///      This is the same payload that would be included by a `revert(string)`
                          ///      solidity statement. It has the function signature `Error(string)`.
                          /// @param message The error string.
                          /// @return The ABI encoded error.
                          function StandardError(string memory message)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  STANDARD_ERROR_SELECTOR,
                                  bytes(message)
                              );
                          }
                          // solhint-enable func-name-mixedcase
                          /// @dev Reverts an encoded rich revert reason `errorData`.
                          /// @param errorData ABI encoded error data.
                          function rrevert(bytes memory errorData)
                              internal
                              pure
                          {
                              assembly {
                                  revert(add(errorData, 0x20), mload(errorData))
                              }
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibOwnableRichErrors {
                          // solhint-disable func-name-mixedcase
                          function OnlyOwnerError(
                              address sender,
                              address owner
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OnlyOwnerError(address,address)")),
                                  sender,
                                  owner
                              );
                          }
                          function TransferOwnerToZeroError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("TransferOwnerToZeroError()"))
                              );
                          }
                          function MigrateCallFailedError(address target, bytes memory resultData)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("MigrateCallFailedError(address,bytes)")),
                                  target,
                                  resultData
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Basic interface for a feature contract.
                      interface IFeature {
                          // solhint-disable func-name-mixedcase
                          /// @dev The name of this feature set.
                          function FEATURE_NAME() external view returns (string memory name);
                          /// @dev The version of this feature set.
                          function FEATURE_VERSION() external view returns (uint256 version);
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "../libs/LibSignature.sol";
                      import "../libs/LibNativeOrder.sol";
                      import "./INativeOrdersEvents.sol";
                      /// @dev Feature for interacting with limit orders.
                      interface INativeOrdersFeature is
                          INativeOrdersEvents
                      {
                          /// @dev Transfers protocol fees from the `FeeCollector` pools into
                          ///      the staking contract.
                          /// @param poolIds Staking pool IDs
                          function transferProtocolFeesForPools(bytes32[] calldata poolIds)
                              external;
                          /// @dev Fill a limit order. The taker and sender will be the caller.
                          /// @param order The limit order. ETH protocol fees can be
                          ///      attached to this call. Any unspent ETH will be refunded to
                          ///      the caller.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token amount to fill this order with.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillLimitOrder(
                              LibNativeOrder.LimitOrder calldata order,
                              LibSignature.Signature calldata signature,
                              uint128 takerTokenFillAmount
                          )
                              external
                              payable
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount);
                          /// @dev Fill an RFQ order for up to `takerTokenFillAmount` taker tokens.
                          ///      The taker will be the caller.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token amount to fill this order with.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillRfqOrder(
                              LibNativeOrder.RfqOrder calldata order,
                              LibSignature.Signature calldata signature,
                              uint128 takerTokenFillAmount
                          )
                              external
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount);
                          /// @dev Fill an RFQ order for exactly `takerTokenFillAmount` taker tokens.
                          ///      The taker will be the caller. ETH protocol fees can be
                          ///      attached to this call. Any unspent ETH will be refunded to
                          ///      the caller.
                          /// @param order The limit order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount How much taker token to fill this order with.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillOrKillLimitOrder(
                              LibNativeOrder.LimitOrder calldata order,
                              LibSignature.Signature calldata signature,
                              uint128 takerTokenFillAmount
                          )
                              external
                              payable
                              returns (uint128 makerTokenFilledAmount);
                          /// @dev Fill an RFQ order for exactly `takerTokenFillAmount` taker tokens.
                          ///      The taker will be the caller.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount How much taker token to fill this order with.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillOrKillRfqOrder(
                              LibNativeOrder.RfqOrder calldata order,
                              LibSignature.Signature calldata signature,
                              uint128 takerTokenFillAmount
                          )
                              external
                              returns (uint128 makerTokenFilledAmount);
                          /// @dev Fill a limit order. Internal variant. ETH protocol fees can be
                          ///      attached to this call. Any unspent ETH will be refunded to
                          ///      `msg.sender` (not `sender`).
                          /// @param order The limit order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token to fill this order with.
                          /// @param taker The order taker.
                          /// @param sender The order sender.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function _fillLimitOrder(
                              LibNativeOrder.LimitOrder calldata order,
                              LibSignature.Signature calldata signature,
                              uint128 takerTokenFillAmount,
                              address taker,
                              address sender
                          )
                              external
                              payable
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount);
                          /// @dev Fill an RFQ order. Internal variant.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token to fill this order with.
                          /// @param taker The order taker.
                          /// @param useSelfBalance Whether to use the ExchangeProxy's transient
                          ///        balance of taker tokens to fill the order.
                          /// @param recipient The recipient of the maker tokens.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function _fillRfqOrder(
                              LibNativeOrder.RfqOrder calldata order,
                              LibSignature.Signature calldata signature,
                              uint128 takerTokenFillAmount,
                              address taker,
                              bool useSelfBalance,
                              address recipient
                          )
                              external
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount);
                          /// @dev Cancel a single limit order. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param order The limit order.
                          function cancelLimitOrder(LibNativeOrder.LimitOrder calldata order)
                              external;
                          /// @dev Cancel a single RFQ order. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param order The RFQ order.
                          function cancelRfqOrder(LibNativeOrder.RfqOrder calldata order)
                              external;
                          /// @dev Mark what tx.origin addresses are allowed to fill an order that
                          ///      specifies the message sender as its txOrigin.
                          /// @param origins An array of origin addresses to update.
                          /// @param allowed True to register, false to unregister.
                          function registerAllowedRfqOrigins(address[] memory origins, bool allowed)
                              external;
                          /// @dev Cancel multiple limit orders. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param orders The limit orders.
                          function batchCancelLimitOrders(LibNativeOrder.LimitOrder[] calldata orders)
                              external;
                          /// @dev Cancel multiple RFQ orders. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param orders The RFQ orders.
                          function batchCancelRfqOrders(LibNativeOrder.RfqOrder[] calldata orders)
                              external;
                          /// @dev Cancel all limit orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairLimitOrders(
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              external;
                          /// @dev Cancel all limit orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same maker and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker The maker for which to cancel.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairLimitOrdersWithSigner(
                              address maker,
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              external;
                          /// @dev Cancel all limit orders for a given maker and pairs with salts less
                          ///      than the values provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairLimitOrders(
                              IERC20TokenV06[] calldata makerTokens,
                              IERC20TokenV06[] calldata takerTokens,
                              uint256[] calldata minValidSalts
                          )
                              external;
                          /// @dev Cancel all limit orders for a given maker and pairs with salts less
                          ///      than the values provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same maker and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker The maker for which to cancel.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairLimitOrdersWithSigner(
                              address maker,
                              IERC20TokenV06[] memory makerTokens,
                              IERC20TokenV06[] memory takerTokens,
                              uint256[] memory minValidSalts
                          )
                              external;
                          /// @dev Cancel all RFQ orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairRfqOrders(
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              external;
                          /// @dev Cancel all RFQ orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same maker and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker The maker for which to cancel.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairRfqOrdersWithSigner(
                              address maker,
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              external;
                          /// @dev Cancel all RFQ orders for a given maker and pairs with salts less
                          ///      than the values provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairRfqOrders(
                              IERC20TokenV06[] calldata makerTokens,
                              IERC20TokenV06[] calldata takerTokens,
                              uint256[] calldata minValidSalts
                          )
                              external;
                          /// @dev Cancel all RFQ orders for a given maker and pairs with salts less
                          ///      than the values provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same maker and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker The maker for which to cancel.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairRfqOrdersWithSigner(
                              address maker,
                              IERC20TokenV06[] memory makerTokens,
                              IERC20TokenV06[] memory takerTokens,
                              uint256[] memory minValidSalts
                          )
                              external;
                          /// @dev Get the order info for a limit order.
                          /// @param order The limit order.
                          /// @return orderInfo Info about the order.
                          function getLimitOrderInfo(LibNativeOrder.LimitOrder calldata order)
                              external
                              view
                              returns (LibNativeOrder.OrderInfo memory orderInfo);
                          /// @dev Get the order info for an RFQ order.
                          /// @param order The RFQ order.
                          /// @return orderInfo Info about the order.
                          function getRfqOrderInfo(LibNativeOrder.RfqOrder calldata order)
                              external
                              view
                              returns (LibNativeOrder.OrderInfo memory orderInfo);
                          /// @dev Get the canonical hash of a limit order.
                          /// @param order The limit order.
                          /// @return orderHash The order hash.
                          function getLimitOrderHash(LibNativeOrder.LimitOrder calldata order)
                              external
                              view
                              returns (bytes32 orderHash);
                          /// @dev Get the canonical hash of an RFQ order.
                          /// @param order The RFQ order.
                          /// @return orderHash The order hash.
                          function getRfqOrderHash(LibNativeOrder.RfqOrder calldata order)
                              external
                              view
                              returns (bytes32 orderHash);
                          /// @dev Get the protocol fee multiplier. This should be multiplied by the
                          ///      gas price to arrive at the required protocol fee to fill a native order.
                          /// @return multiplier The protocol fee multiplier.
                          function getProtocolFeeMultiplier()
                              external
                              view
                              returns (uint32 multiplier);
                          /// @dev Get order info, fillable amount, and signature validity for a limit order.
                          ///      Fillable amount is determined using balances and allowances of the maker.
                          /// @param order The limit order.
                          /// @param signature The order signature.
                          /// @return orderInfo Info about the order.
                          /// @return actualFillableTakerTokenAmount How much of the order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValid Whether the signature is valid.
                          function getLimitOrderRelevantState(
                              LibNativeOrder.LimitOrder calldata order,
                              LibSignature.Signature calldata signature
                          )
                              external
                              view
                              returns (
                                  LibNativeOrder.OrderInfo memory orderInfo,
                                  uint128 actualFillableTakerTokenAmount,
                                  bool isSignatureValid
                              );
                          /// @dev Get order info, fillable amount, and signature validity for an RFQ order.
                          ///      Fillable amount is determined using balances and allowances of the maker.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @return orderInfo Info about the order.
                          /// @return actualFillableTakerTokenAmount How much of the order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValid Whether the signature is valid.
                          function getRfqOrderRelevantState(
                              LibNativeOrder.RfqOrder calldata order,
                              LibSignature.Signature calldata signature
                          )
                              external
                              view
                              returns (
                                  LibNativeOrder.OrderInfo memory orderInfo,
                                  uint128 actualFillableTakerTokenAmount,
                                  bool isSignatureValid
                              );
                          /// @dev Batch version of `getLimitOrderRelevantState()`, without reverting.
                          ///      Orders that would normally cause `getLimitOrderRelevantState()`
                          ///      to revert will have empty results.
                          /// @param orders The limit orders.
                          /// @param signatures The order signatures.
                          /// @return orderInfos Info about the orders.
                          /// @return actualFillableTakerTokenAmounts How much of each order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValids Whether each signature is valid for the order.
                          function batchGetLimitOrderRelevantStates(
                              LibNativeOrder.LimitOrder[] calldata orders,
                              LibSignature.Signature[] calldata signatures
                          )
                              external
                              view
                              returns (
                                  LibNativeOrder.OrderInfo[] memory orderInfos,
                                  uint128[] memory actualFillableTakerTokenAmounts,
                                  bool[] memory isSignatureValids
                              );
                          /// @dev Batch version of `getRfqOrderRelevantState()`, without reverting.
                          ///      Orders that would normally cause `getRfqOrderRelevantState()`
                          ///      to revert will have empty results.
                          /// @param orders The RFQ orders.
                          /// @param signatures The order signatures.
                          /// @return orderInfos Info about the orders.
                          /// @return actualFillableTakerTokenAmounts How much of each order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValids Whether each signature is valid for the order.
                          function batchGetRfqOrderRelevantStates(
                              LibNativeOrder.RfqOrder[] calldata orders,
                              LibSignature.Signature[] calldata signatures
                          )
                              external
                              view
                              returns (
                                  LibNativeOrder.OrderInfo[] memory orderInfos,
                                  uint128[] memory actualFillableTakerTokenAmounts,
                                  bool[] memory isSignatureValids
                              );
                          /// @dev Register a signer who can sign on behalf of msg.sender
                          ///      This allows one to sign on behalf of a contract that calls this function
                          /// @param signer The address from which you plan to generate signatures
                          /// @param allowed True to register, false to unregister.
                          function registerAllowedOrderSigner(
                              address signer,
                              bool allowed
                          )
                              external;
                          /// @dev checks if a given address is registered to sign on behalf of a maker address
                          /// @param maker The maker address encoded in an order (can be a contract)
                          /// @param signer The address that is providing a signature
                          function isValidOrderSigner(
                              address maker,
                              address signer
                          )
                              external
                              view
                              returns (bool isAllowed);
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      interface IERC20TokenV06 {
                          // solhint-disable no-simple-event-func-name
                          event Transfer(
                              address indexed from,
                              address indexed to,
                              uint256 value
                          );
                          event Approval(
                              address indexed owner,
                              address indexed spender,
                              uint256 value
                          );
                          /// @dev send `value` token to `to` from `msg.sender`
                          /// @param to The address of the recipient
                          /// @param value The amount of token to be transferred
                          /// @return True if transfer was successful
                          function transfer(address to, uint256 value)
                              external
                              returns (bool);
                          /// @dev send `value` token to `to` from `from` on the condition it is approved by `from`
                          /// @param from The address of the sender
                          /// @param to The address of the recipient
                          /// @param value The amount of token to be transferred
                          /// @return True if transfer was successful
                          function transferFrom(
                              address from,
                              address to,
                              uint256 value
                          )
                              external
                              returns (bool);
                          /// @dev `msg.sender` approves `spender` to spend `value` tokens
                          /// @param spender The address of the account able to transfer the tokens
                          /// @param value The amount of wei to be approved for transfer
                          /// @return Always true if the call has enough gas to complete execution
                          function approve(address spender, uint256 value)
                              external
                              returns (bool);
                          /// @dev Query total supply of token
                          /// @return Total supply of token
                          function totalSupply()
                              external
                              view
                              returns (uint256);
                          /// @dev Get the balance of `owner`.
                          /// @param owner The address from which the balance will be retrieved
                          /// @return Balance of owner
                          function balanceOf(address owner)
                              external
                              view
                              returns (uint256);
                          /// @dev Get the allowance for `spender` to spend from `owner`.
                          /// @param owner The address of the account owning tokens
                          /// @param spender The address of the account able to transfer the tokens
                          /// @return Amount of remaining tokens allowed to spent
                          function allowance(address owner, address spender)
                              external
                              view
                              returns (uint256);
                          /// @dev Get the number of decimals this token has.
                          function decimals()
                              external
                              view
                              returns (uint8);
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../../errors/LibSignatureRichErrors.sol";
                      /// @dev A library for validating signatures.
                      library LibSignature {
                          using LibRichErrorsV06 for bytes;
                          // '\\x19Ethereum Signed Message:\
                      32\\x00\\x00\\x00\\x00' in a word.
                          uint256 private constant ETH_SIGN_HASH_PREFIX =
                              0x19457468657265756d205369676e6564204d6573736167653a0a333200000000;
                          /// @dev Exclusive upper limit on ECDSA signatures 'R' values.
                          ///      The valid range is given by fig (282) of the yellow paper.
                          uint256 private constant ECDSA_SIGNATURE_R_LIMIT =
                              uint256(0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141);
                          /// @dev Exclusive upper limit on ECDSA signatures 'S' values.
                          ///      The valid range is given by fig (283) of the yellow paper.
                          uint256 private constant ECDSA_SIGNATURE_S_LIMIT = ECDSA_SIGNATURE_R_LIMIT / 2 + 1;
                          /// @dev Allowed signature types.
                          enum SignatureType {
                              ILLEGAL,
                              INVALID,
                              EIP712,
                              ETHSIGN
                          }
                          /// @dev Encoded EC signature.
                          struct Signature {
                              // How to validate the signature.
                              SignatureType signatureType;
                              // EC Signature data.
                              uint8 v;
                              // EC Signature data.
                              bytes32 r;
                              // EC Signature data.
                              bytes32 s;
                          }
                          /// @dev Retrieve the signer of a signature.
                          ///      Throws if the signature can't be validated.
                          /// @param hash The hash that was signed.
                          /// @param signature The signature.
                          /// @return recovered The recovered signer address.
                          function getSignerOfHash(
                              bytes32 hash,
                              Signature memory signature
                          )
                              internal
                              pure
                              returns (address recovered)
                          {
                              // Ensure this is a signature type that can be validated against a hash.
                              _validateHashCompatibleSignature(hash, signature);
                              if (signature.signatureType == SignatureType.EIP712) {
                                  // Signed using EIP712
                                  recovered = ecrecover(
                                      hash,
                                      signature.v,
                                      signature.r,
                                      signature.s
                                  );
                              } else if (signature.signatureType == SignatureType.ETHSIGN) {
                                  // Signed using `eth_sign`
                                  // Need to hash `hash` with "\\x19Ethereum Signed Message:\
                      32" prefix
                                  // in packed encoding.
                                  bytes32 ethSignHash;
                                  assembly {
                                      // Use scratch space
                                      mstore(0, ETH_SIGN_HASH_PREFIX) // length of 28 bytes
                                      mstore(28, hash) // length of 32 bytes
                                      ethSignHash := keccak256(0, 60)
                                  }
                                  recovered = ecrecover(
                                      ethSignHash,
                                      signature.v,
                                      signature.r,
                                      signature.s
                                  );
                              }
                              // `recovered` can be null if the signature values are out of range.
                              if (recovered == address(0)) {
                                  LibSignatureRichErrors.SignatureValidationError(
                                      LibSignatureRichErrors.SignatureValidationErrorCodes.BAD_SIGNATURE_DATA,
                                      hash
                                  ).rrevert();
                              }
                          }
                          /// @dev Validates that a signature is compatible with a hash signee.
                          /// @param hash The hash that was signed.
                          /// @param signature The signature.
                          function _validateHashCompatibleSignature(
                              bytes32 hash,
                              Signature memory signature
                          )
                              private
                              pure
                          {
                              // Ensure the r and s are within malleability limits.
                              if (uint256(signature.r) >= ECDSA_SIGNATURE_R_LIMIT ||
                                  uint256(signature.s) >= ECDSA_SIGNATURE_S_LIMIT)
                              {
                                  LibSignatureRichErrors.SignatureValidationError(
                                      LibSignatureRichErrors.SignatureValidationErrorCodes.BAD_SIGNATURE_DATA,
                                      hash
                                  ).rrevert();
                              }
                              // Always illegal signature.
                              if (signature.signatureType == SignatureType.ILLEGAL) {
                                  LibSignatureRichErrors.SignatureValidationError(
                                      LibSignatureRichErrors.SignatureValidationErrorCodes.ILLEGAL,
                                      hash
                                  ).rrevert();
                              }
                              // Always invalid.
                              if (signature.signatureType == SignatureType.INVALID) {
                                  LibSignatureRichErrors.SignatureValidationError(
                                      LibSignatureRichErrors.SignatureValidationErrorCodes.ALWAYS_INVALID,
                                      hash
                                  ).rrevert();
                              }
                              // Solidity should check that the signature type is within enum range for us
                              // when abi-decoding.
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibSignatureRichErrors {
                          enum SignatureValidationErrorCodes {
                              ALWAYS_INVALID,
                              INVALID_LENGTH,
                              UNSUPPORTED,
                              ILLEGAL,
                              WRONG_SIGNER,
                              BAD_SIGNATURE_DATA
                          }
                          // solhint-disable func-name-mixedcase
                          function SignatureValidationError(
                              SignatureValidationErrorCodes code,
                              bytes32 hash,
                              address signerAddress,
                              bytes memory signature
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("SignatureValidationError(uint8,bytes32,address,bytes)")),
                                  code,
                                  hash,
                                  signerAddress,
                                  signature
                              );
                          }
                          function SignatureValidationError(
                              SignatureValidationErrorCodes code,
                              bytes32 hash
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("SignatureValidationError(uint8,bytes32)")),
                                  code,
                                  hash
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "../../errors/LibNativeOrdersRichErrors.sol";
                      /// @dev A library for common native order operations.
                      library LibNativeOrder {
                          using LibSafeMathV06 for uint256;
                          using LibRichErrorsV06 for bytes;
                          enum OrderStatus {
                              INVALID,
                              FILLABLE,
                              FILLED,
                              CANCELLED,
                              EXPIRED
                          }
                          /// @dev A standard OTC or OO limit order.
                          struct LimitOrder {
                              IERC20TokenV06 makerToken;
                              IERC20TokenV06 takerToken;
                              uint128 makerAmount;
                              uint128 takerAmount;
                              uint128 takerTokenFeeAmount;
                              address maker;
                              address taker;
                              address sender;
                              address feeRecipient;
                              bytes32 pool;
                              uint64 expiry;
                              uint256 salt;
                          }
                          /// @dev An RFQ limit order.
                          struct RfqOrder {
                              IERC20TokenV06 makerToken;
                              IERC20TokenV06 takerToken;
                              uint128 makerAmount;
                              uint128 takerAmount;
                              address maker;
                              address taker;
                              address txOrigin;
                              bytes32 pool;
                              uint64 expiry;
                              uint256 salt;
                          }
                          /// @dev An OTC limit order.
                          struct OtcOrder {
                              IERC20TokenV06 makerToken;
                              IERC20TokenV06 takerToken;
                              uint128 makerAmount;
                              uint128 takerAmount;
                              address maker;
                              address taker;
                              address txOrigin;
                              uint256 expiryAndNonce; // [uint64 expiry, uint64 nonceBucket, uint128 nonce]
                          }
                          /// @dev Info on a limit or RFQ order.
                          struct OrderInfo {
                              bytes32 orderHash;
                              OrderStatus status;
                              uint128 takerTokenFilledAmount;
                          }
                          /// @dev Info on an OTC order.
                          struct OtcOrderInfo {
                              bytes32 orderHash;
                              OrderStatus status;
                          }
                          uint256 private constant UINT_128_MASK = (1 << 128) - 1;
                          uint256 private constant UINT_64_MASK = (1 << 64) - 1;
                          uint256 private constant ADDRESS_MASK = (1 << 160) - 1;
                          // The type hash for limit orders, which is:
                          // keccak256(abi.encodePacked(
                          //     "LimitOrder(",
                          //       "address makerToken,",
                          //       "address takerToken,",
                          //       "uint128 makerAmount,",
                          //       "uint128 takerAmount,",
                          //       "uint128 takerTokenFeeAmount,",
                          //       "address maker,",
                          //       "address taker,",
                          //       "address sender,",
                          //       "address feeRecipient,",
                          //       "bytes32 pool,",
                          //       "uint64 expiry,",
                          //       "uint256 salt"
                          //     ")"
                          // ))
                          uint256 private constant _LIMIT_ORDER_TYPEHASH =
                              0xce918627cb55462ddbb85e73de69a8b322f2bc88f4507c52fcad6d4c33c29d49;
                          // The type hash for RFQ orders, which is:
                          // keccak256(abi.encodePacked(
                          //     "RfqOrder(",
                          //       "address makerToken,",
                          //       "address takerToken,",
                          //       "uint128 makerAmount,",
                          //       "uint128 takerAmount,",
                          //       "address maker,",
                          //       "address taker,",
                          //       "address txOrigin,",
                          //       "bytes32 pool,",
                          //       "uint64 expiry,",
                          //       "uint256 salt"
                          //     ")"
                          // ))
                          uint256 private constant _RFQ_ORDER_TYPEHASH =
                              0xe593d3fdfa8b60e5e17a1b2204662ecbe15c23f2084b9ad5bae40359540a7da9;
                          // The type hash for OTC orders, which is:
                          // keccak256(abi.encodePacked(
                          //     "OtcOrder(",
                          //       "address makerToken,",
                          //       "address takerToken,",
                          //       "uint128 makerAmount,",
                          //       "uint128 takerAmount,",
                          //       "address maker,",
                          //       "address taker,",
                          //       "address txOrigin,",
                          //       "uint256 expiryAndNonce"
                          //     ")"
                          // ))
                          uint256 private constant _OTC_ORDER_TYPEHASH =
                              0x2f754524de756ae72459efbe1ec88c19a745639821de528ac3fb88f9e65e35c8;
                          /// @dev Get the struct hash of a limit order.
                          /// @param order The limit order.
                          /// @return structHash The struct hash of the order.
                          function getLimitOrderStructHash(LimitOrder memory order)
                              internal
                              pure
                              returns (bytes32 structHash)
                          {
                              // The struct hash is:
                              // keccak256(abi.encode(
                              //   TYPE_HASH,
                              //   order.makerToken,
                              //   order.takerToken,
                              //   order.makerAmount,
                              //   order.takerAmount,
                              //   order.takerTokenFeeAmount,
                              //   order.maker,
                              //   order.taker,
                              //   order.sender,
                              //   order.feeRecipient,
                              //   order.pool,
                              //   order.expiry,
                              //   order.salt,
                              // ))
                              assembly {
                                  let mem := mload(0x40)
                                  mstore(mem, _LIMIT_ORDER_TYPEHASH)
                                  // order.makerToken;
                                  mstore(add(mem, 0x20), and(ADDRESS_MASK, mload(order)))
                                  // order.takerToken;
                                  mstore(add(mem, 0x40), and(ADDRESS_MASK, mload(add(order, 0x20))))
                                  // order.makerAmount;
                                  mstore(add(mem, 0x60), and(UINT_128_MASK, mload(add(order, 0x40))))
                                  // order.takerAmount;
                                  mstore(add(mem, 0x80), and(UINT_128_MASK, mload(add(order, 0x60))))
                                  // order.takerTokenFeeAmount;
                                  mstore(add(mem, 0xA0), and(UINT_128_MASK, mload(add(order, 0x80))))
                                  // order.maker;
                                  mstore(add(mem, 0xC0), and(ADDRESS_MASK, mload(add(order, 0xA0))))
                                  // order.taker;
                                  mstore(add(mem, 0xE0), and(ADDRESS_MASK, mload(add(order, 0xC0))))
                                  // order.sender;
                                  mstore(add(mem, 0x100), and(ADDRESS_MASK, mload(add(order, 0xE0))))
                                  // order.feeRecipient;
                                  mstore(add(mem, 0x120), and(ADDRESS_MASK, mload(add(order, 0x100))))
                                  // order.pool;
                                  mstore(add(mem, 0x140), mload(add(order, 0x120)))
                                  // order.expiry;
                                  mstore(add(mem, 0x160), and(UINT_64_MASK, mload(add(order, 0x140))))
                                  // order.salt;
                                  mstore(add(mem, 0x180), mload(add(order, 0x160)))
                                  structHash := keccak256(mem, 0x1A0)
                              }
                          }
                          /// @dev Get the struct hash of a RFQ order.
                          /// @param order The RFQ order.
                          /// @return structHash The struct hash of the order.
                          function getRfqOrderStructHash(RfqOrder memory order)
                              internal
                              pure
                              returns (bytes32 structHash)
                          {
                              // The struct hash is:
                              // keccak256(abi.encode(
                              //   TYPE_HASH,
                              //   order.makerToken,
                              //   order.takerToken,
                              //   order.makerAmount,
                              //   order.takerAmount,
                              //   order.maker,
                              //   order.taker,
                              //   order.txOrigin,
                              //   order.pool,
                              //   order.expiry,
                              //   order.salt,
                              // ))
                              assembly {
                                  let mem := mload(0x40)
                                  mstore(mem, _RFQ_ORDER_TYPEHASH)
                                  // order.makerToken;
                                  mstore(add(mem, 0x20), and(ADDRESS_MASK, mload(order)))
                                  // order.takerToken;
                                  mstore(add(mem, 0x40), and(ADDRESS_MASK, mload(add(order, 0x20))))
                                  // order.makerAmount;
                                  mstore(add(mem, 0x60), and(UINT_128_MASK, mload(add(order, 0x40))))
                                  // order.takerAmount;
                                  mstore(add(mem, 0x80), and(UINT_128_MASK, mload(add(order, 0x60))))
                                  // order.maker;
                                  mstore(add(mem, 0xA0), and(ADDRESS_MASK, mload(add(order, 0x80))))
                                  // order.taker;
                                  mstore(add(mem, 0xC0), and(ADDRESS_MASK, mload(add(order, 0xA0))))
                                  // order.txOrigin;
                                  mstore(add(mem, 0xE0), and(ADDRESS_MASK, mload(add(order, 0xC0))))
                                  // order.pool;
                                  mstore(add(mem, 0x100), mload(add(order, 0xE0)))
                                  // order.expiry;
                                  mstore(add(mem, 0x120), and(UINT_64_MASK, mload(add(order, 0x100))))
                                  // order.salt;
                                  mstore(add(mem, 0x140), mload(add(order, 0x120)))
                                  structHash := keccak256(mem, 0x160)
                              }
                          }
                          /// @dev Get the struct hash of an OTC order.
                          /// @param order The OTC order.
                          /// @return structHash The struct hash of the order.
                          function getOtcOrderStructHash(OtcOrder memory order)
                              internal
                              pure
                              returns (bytes32 structHash)
                          {
                              // The struct hash is:
                              // keccak256(abi.encode(
                              //   TYPE_HASH,
                              //   order.makerToken,
                              //   order.takerToken,
                              //   order.makerAmount,
                              //   order.takerAmount,
                              //   order.maker,
                              //   order.taker,
                              //   order.txOrigin,
                              //   order.expiryAndNonce,
                              // ))
                              assembly {
                                  let mem := mload(0x40)
                                  mstore(mem, _OTC_ORDER_TYPEHASH)
                                  // order.makerToken;
                                  mstore(add(mem, 0x20), and(ADDRESS_MASK, mload(order)))
                                  // order.takerToken;
                                  mstore(add(mem, 0x40), and(ADDRESS_MASK, mload(add(order, 0x20))))
                                  // order.makerAmount;
                                  mstore(add(mem, 0x60), and(UINT_128_MASK, mload(add(order, 0x40))))
                                  // order.takerAmount;
                                  mstore(add(mem, 0x80), and(UINT_128_MASK, mload(add(order, 0x60))))
                                  // order.maker;
                                  mstore(add(mem, 0xA0), and(ADDRESS_MASK, mload(add(order, 0x80))))
                                  // order.taker;
                                  mstore(add(mem, 0xC0), and(ADDRESS_MASK, mload(add(order, 0xA0))))
                                  // order.txOrigin;
                                  mstore(add(mem, 0xE0), and(ADDRESS_MASK, mload(add(order, 0xC0))))
                                  // order.expiryAndNonce;
                                  mstore(add(mem, 0x100), mload(add(order, 0xE0)))
                                  structHash := keccak256(mem, 0x120)
                              }
                          }
                          /// @dev Refund any leftover protocol fees in `msg.value` to `msg.sender`.
                          /// @param ethProtocolFeePaid How much ETH was paid in protocol fees.
                          function refundExcessProtocolFeeToSender(uint256 ethProtocolFeePaid)
                              internal
                          {
                              if (msg.value > ethProtocolFeePaid && msg.sender != address(this)) {
                                  uint256 refundAmount = msg.value.safeSub(ethProtocolFeePaid);
                                  (bool success,) = msg
                                      .sender
                                      .call{value: refundAmount}("");
                                  if (!success) {
                                      LibNativeOrdersRichErrors.ProtocolFeeRefundFailed(
                                          msg.sender,
                                          refundAmount
                                      ).rrevert();
                                  }
                              }
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibSafeMathRichErrorsV06.sol";
                      library LibSafeMathV06 {
                          function safeMul(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              if (a == 0) {
                                  return 0;
                              }
                              uint256 c = a * b;
                              if (c / a != b) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.MULTIPLICATION_OVERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return c;
                          }
                          function safeDiv(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              if (b == 0) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.DIVISION_BY_ZERO,
                                      a,
                                      b
                                  ));
                              }
                              uint256 c = a / b;
                              return c;
                          }
                          function safeSub(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              if (b > a) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.SUBTRACTION_UNDERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return a - b;
                          }
                          function safeAdd(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              uint256 c = a + b;
                              if (c < a) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.ADDITION_OVERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return c;
                          }
                          function max256(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              return a >= b ? a : b;
                          }
                          function min256(uint256 a, uint256 b)
                              internal
                              pure
                              returns (uint256)
                          {
                              return a < b ? a : b;
                          }
                          function safeMul128(uint128 a, uint128 b)
                              internal
                              pure
                              returns (uint128)
                          {
                              if (a == 0) {
                                  return 0;
                              }
                              uint128 c = a * b;
                              if (c / a != b) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.MULTIPLICATION_OVERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return c;
                          }
                          function safeDiv128(uint128 a, uint128 b)
                              internal
                              pure
                              returns (uint128)
                          {
                              if (b == 0) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.DIVISION_BY_ZERO,
                                      a,
                                      b
                                  ));
                              }
                              uint128 c = a / b;
                              return c;
                          }
                          function safeSub128(uint128 a, uint128 b)
                              internal
                              pure
                              returns (uint128)
                          {
                              if (b > a) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.SUBTRACTION_UNDERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return a - b;
                          }
                          function safeAdd128(uint128 a, uint128 b)
                              internal
                              pure
                              returns (uint128)
                          {
                              uint128 c = a + b;
                              if (c < a) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256BinOpError(
                                      LibSafeMathRichErrorsV06.BinOpErrorCodes.ADDITION_OVERFLOW,
                                      a,
                                      b
                                  ));
                              }
                              return c;
                          }
                          function max128(uint128 a, uint128 b)
                              internal
                              pure
                              returns (uint128)
                          {
                              return a >= b ? a : b;
                          }
                          function min128(uint128 a, uint128 b)
                              internal
                              pure
                              returns (uint128)
                          {
                              return a < b ? a : b;
                          }
                          function safeDowncastToUint128(uint256 a)
                              internal
                              pure
                              returns (uint128)
                          {
                              if (a > type(uint128).max) {
                                  LibRichErrorsV06.rrevert(LibSafeMathRichErrorsV06.Uint256DowncastError(
                                      LibSafeMathRichErrorsV06.DowncastErrorCodes.VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT128,
                                      a
                                  ));
                              }
                              return uint128(a);
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibSafeMathRichErrorsV06 {
                          // bytes4(keccak256("Uint256BinOpError(uint8,uint256,uint256)"))
                          bytes4 internal constant UINT256_BINOP_ERROR_SELECTOR =
                              0xe946c1bb;
                          // bytes4(keccak256("Uint256DowncastError(uint8,uint256)"))
                          bytes4 internal constant UINT256_DOWNCAST_ERROR_SELECTOR =
                              0xc996af7b;
                          enum BinOpErrorCodes {
                              ADDITION_OVERFLOW,
                              MULTIPLICATION_OVERFLOW,
                              SUBTRACTION_UNDERFLOW,
                              DIVISION_BY_ZERO
                          }
                          enum DowncastErrorCodes {
                              VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT32,
                              VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT64,
                              VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT96,
                              VALUE_TOO_LARGE_TO_DOWNCAST_TO_UINT128
                          }
                          // solhint-disable func-name-mixedcase
                          function Uint256BinOpError(
                              BinOpErrorCodes errorCode,
                              uint256 a,
                              uint256 b
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  UINT256_BINOP_ERROR_SELECTOR,
                                  errorCode,
                                  a,
                                  b
                              );
                          }
                          function Uint256DowncastError(
                              DowncastErrorCodes errorCode,
                              uint256 a
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  UINT256_DOWNCAST_ERROR_SELECTOR,
                                  errorCode,
                                  a
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibNativeOrdersRichErrors {
                          // solhint-disable func-name-mixedcase
                          function ProtocolFeeRefundFailed(
                              address receiver,
                              uint256 refundAmount
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("ProtocolFeeRefundFailed(address,uint256)")),
                                  receiver,
                                  refundAmount
                              );
                          }
                          function OrderNotFillableByOriginError(
                              bytes32 orderHash,
                              address txOrigin,
                              address orderTxOrigin
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OrderNotFillableByOriginError(bytes32,address,address)")),
                                  orderHash,
                                  txOrigin,
                                  orderTxOrigin
                              );
                          }
                          function OrderNotFillableError(
                              bytes32 orderHash,
                              uint8 orderStatus
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OrderNotFillableError(bytes32,uint8)")),
                                  orderHash,
                                  orderStatus
                              );
                          }
                          function OrderNotSignedByMakerError(
                              bytes32 orderHash,
                              address signer,
                              address maker
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OrderNotSignedByMakerError(bytes32,address,address)")),
                                  orderHash,
                                  signer,
                                  maker
                              );
                          }
                          function InvalidSignerError(
                              address maker,
                              address signer
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("InvalidSignerError(address,address)")),
                                  maker,
                                  signer
                              );
                          }
                          function OrderNotFillableBySenderError(
                              bytes32 orderHash,
                              address sender,
                              address orderSender
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OrderNotFillableBySenderError(bytes32,address,address)")),
                                  orderHash,
                                  sender,
                                  orderSender
                              );
                          }
                          function OrderNotFillableByTakerError(
                              bytes32 orderHash,
                              address taker,
                              address orderTaker
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OrderNotFillableByTakerError(bytes32,address,address)")),
                                  orderHash,
                                  taker,
                                  orderTaker
                              );
                          }
                          function CancelSaltTooLowError(
                              uint256 minValidSalt,
                              uint256 oldMinValidSalt
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("CancelSaltTooLowError(uint256,uint256)")),
                                  minValidSalt,
                                  oldMinValidSalt
                              );
                          }
                          function FillOrKillFailedError(
                              bytes32 orderHash,
                              uint256 takerTokenFilledAmount,
                              uint256 takerTokenFillAmount
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("FillOrKillFailedError(bytes32,uint256,uint256)")),
                                  orderHash,
                                  takerTokenFilledAmount,
                                  takerTokenFillAmount
                              );
                          }
                          function OnlyOrderMakerAllowed(
                              bytes32 orderHash,
                              address sender,
                              address maker
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OnlyOrderMakerAllowed(bytes32,address,address)")),
                                  orderHash,
                                  sender,
                                  maker
                              );
                          }
                          function BatchFillIncompleteError(
                              bytes32 orderHash,
                              uint256 takerTokenFilledAmount,
                              uint256 takerTokenFillAmount
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("BatchFillIncompleteError(bytes32,uint256,uint256)")),
                                  orderHash,
                                  takerTokenFilledAmount,
                                  takerTokenFillAmount
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2021 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "../libs/LibSignature.sol";
                      import "../libs/LibNativeOrder.sol";
                      /// @dev Events emitted by NativeOrdersFeature.
                      interface INativeOrdersEvents {
                          /// @dev Emitted whenever a `LimitOrder` is filled.
                          /// @param orderHash The canonical hash of the order.
                          /// @param maker The maker of the order.
                          /// @param taker The taker of the order.
                          /// @param feeRecipient Fee recipient of the order.
                          /// @param takerTokenFilledAmount How much taker token was filled.
                          /// @param makerTokenFilledAmount How much maker token was filled.
                          /// @param protocolFeePaid How much protocol fee was paid.
                          /// @param pool The fee pool associated with this order.
                          event LimitOrderFilled(
                              bytes32 orderHash,
                              address maker,
                              address taker,
                              address feeRecipient,
                              address makerToken,
                              address takerToken,
                              uint128 takerTokenFilledAmount,
                              uint128 makerTokenFilledAmount,
                              uint128 takerTokenFeeFilledAmount,
                              uint256 protocolFeePaid,
                              bytes32 pool
                          );
                          /// @dev Emitted whenever an `RfqOrder` is filled.
                          /// @param orderHash The canonical hash of the order.
                          /// @param maker The maker of the order.
                          /// @param taker The taker of the order.
                          /// @param takerTokenFilledAmount How much taker token was filled.
                          /// @param makerTokenFilledAmount How much maker token was filled.
                          /// @param pool The fee pool associated with this order.
                          event RfqOrderFilled(
                              bytes32 orderHash,
                              address maker,
                              address taker,
                              address makerToken,
                              address takerToken,
                              uint128 takerTokenFilledAmount,
                              uint128 makerTokenFilledAmount,
                              bytes32 pool
                          );
                          /// @dev Emitted whenever a limit or RFQ order is cancelled.
                          /// @param orderHash The canonical hash of the order.
                          /// @param maker The order maker.
                          event OrderCancelled(
                              bytes32 orderHash,
                              address maker
                          );
                          /// @dev Emitted whenever Limit orders are cancelled by pair by a maker.
                          /// @param maker The maker of the order.
                          /// @param makerToken The maker token in a pair for the orders cancelled.
                          /// @param takerToken The taker token in a pair for the orders cancelled.
                          /// @param minValidSalt The new minimum valid salt an order with this pair must
                          ///        have.
                          event PairCancelledLimitOrders(
                              address maker,
                              address makerToken,
                              address takerToken,
                              uint256 minValidSalt
                          );
                          /// @dev Emitted whenever RFQ orders are cancelled by pair by a maker.
                          /// @param maker The maker of the order.
                          /// @param makerToken The maker token in a pair for the orders cancelled.
                          /// @param takerToken The taker token in a pair for the orders cancelled.
                          /// @param minValidSalt The new minimum valid salt an order with this pair must
                          ///        have.
                          event PairCancelledRfqOrders(
                              address maker,
                              address makerToken,
                              address takerToken,
                              uint256 minValidSalt
                          );
                          /// @dev Emitted when new addresses are allowed or disallowed to fill
                          ///      orders with a given txOrigin.
                          /// @param origin The address doing the allowing.
                          /// @param addrs The address being allowed/disallowed.
                          /// @param allowed Indicates whether the address should be allowed.
                          event RfqOrderOriginsAllowed(
                              address origin,
                              address[] addrs,
                              bool allowed
                          );
                          /// @dev Emitted when new order signers are registered
                          /// @param maker The maker address that is registering a designated signer.
                          /// @param signer The address that will sign on behalf of maker.
                          /// @param allowed Indicates whether the address should be allowed.
                          event OrderSignerRegistered(
                              address maker,
                              address signer,
                              bool allowed
                          );
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2021 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibMathV06.sol";
                      import "../../errors/LibNativeOrdersRichErrors.sol";
                      import "../../fixins/FixinCommon.sol";
                      import "../../storage/LibNativeOrdersStorage.sol";
                      import "../../vendor/v3/IStaking.sol";
                      import "../interfaces/INativeOrdersEvents.sol";
                      import "../libs/LibSignature.sol";
                      import "../libs/LibNativeOrder.sol";
                      import "./NativeOrdersCancellation.sol";
                      import "./NativeOrdersProtocolFees.sol";
                      /// @dev Mixin for settling limit and RFQ orders.
                      abstract contract NativeOrdersSettlement is
                          INativeOrdersEvents,
                          NativeOrdersCancellation,
                          NativeOrdersProtocolFees,
                          FixinCommon
                      {
                          using LibSafeMathV06 for uint128;
                          using LibRichErrorsV06 for bytes;
                          /// @dev Params for `_settleOrder()`.
                          struct SettleOrderInfo {
                              // Order hash.
                              bytes32 orderHash;
                              // Maker of the order.
                              address maker;
                              // The address holding the taker tokens.
                              address payer;
                              // Recipient of the maker tokens.
                              address recipient;
                              // Maker token.
                              IERC20TokenV06 makerToken;
                              // Taker token.
                              IERC20TokenV06 takerToken;
                              // Maker token amount.
                              uint128 makerAmount;
                              // Taker token amount.
                              uint128 takerAmount;
                              // Maximum taker token amount to fill.
                              uint128 takerTokenFillAmount;
                              // How much taker token amount has already been filled in this order.
                              uint128 takerTokenFilledAmount;
                          }
                          /// @dev Params for `_fillLimitOrderPrivate()`
                          struct FillLimitOrderPrivateParams {
                              // The limit order.
                              LibNativeOrder.LimitOrder order;
                              // The order signature.
                              LibSignature.Signature signature;
                              // Maximum taker token to fill this order with.
                              uint128 takerTokenFillAmount;
                              // The order taker.
                              address taker;
                              // The order sender.
                              address sender;
                          }
                          /// @dev Params for `_fillRfqOrderPrivate()`
                          struct FillRfqOrderPrivateParams {
                              LibNativeOrder.RfqOrder order;
                              // The order signature.
                              LibSignature.Signature signature;
                              // Maximum taker token to fill this order with.
                              uint128 takerTokenFillAmount;
                              // The order taker.
                              address taker;
                              // Whether to use the Exchange Proxy's balance
                              // of taker tokens.
                              bool useSelfBalance;
                              // The recipient of the maker tokens.
                              address recipient;
                          }
                          // @dev Fill results returned by `_fillLimitOrderPrivate()` and
                          ///     `_fillRfqOrderPrivate()`.
                          struct FillNativeOrderResults {
                              uint256 ethProtocolFeePaid;
                              uint128 takerTokenFilledAmount;
                              uint128 makerTokenFilledAmount;
                              uint128 takerTokenFeeFilledAmount;
                          }
                          constructor(
                              address zeroExAddress,
                              IEtherTokenV06 weth,
                              IStaking staking,
                              FeeCollectorController feeCollectorController,
                              uint32 protocolFeeMultiplier
                          )
                              public
                              NativeOrdersCancellation(zeroExAddress)
                              NativeOrdersProtocolFees(weth, staking, feeCollectorController, protocolFeeMultiplier)
                          {
                              // solhint-disable no-empty-blocks
                          }
                          /// @dev Fill a limit order. The taker and sender will be the caller.
                          /// @param order The limit order. ETH protocol fees can be
                          ///      attached to this call. Any unspent ETH will be refunded to
                          ///      the caller.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token amount to fill this order with.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillLimitOrder(
                              LibNativeOrder.LimitOrder memory order,
                              LibSignature.Signature memory signature,
                              uint128 takerTokenFillAmount
                          )
                              public
                              payable
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount)
                          {
                              FillNativeOrderResults memory results =
                                  _fillLimitOrderPrivate(FillLimitOrderPrivateParams({
                                      order: order,
                                      signature: signature,
                                      takerTokenFillAmount: takerTokenFillAmount,
                                      taker: msg.sender,
                                      sender: msg.sender
                                  }));
                              LibNativeOrder.refundExcessProtocolFeeToSender(results.ethProtocolFeePaid);
                              (takerTokenFilledAmount, makerTokenFilledAmount) = (
                                  results.takerTokenFilledAmount,
                                  results.makerTokenFilledAmount
                              );
                          }
                          /// @dev Fill an RFQ order for up to `takerTokenFillAmount` taker tokens.
                          ///      The taker will be the caller. ETH should be attached to pay the
                          ///      protocol fee.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token amount to fill this order with.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillRfqOrder(
                              LibNativeOrder.RfqOrder memory order,
                              LibSignature.Signature memory signature,
                              uint128 takerTokenFillAmount
                          )
                              public
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount)
                          {
                              FillNativeOrderResults memory results =
                                  _fillRfqOrderPrivate(FillRfqOrderPrivateParams({
                                      order: order,
                                      signature: signature,
                                      takerTokenFillAmount: takerTokenFillAmount,
                                      taker: msg.sender,
                                      useSelfBalance: false,
                                      recipient: msg.sender
                                  }));
                              (takerTokenFilledAmount, makerTokenFilledAmount) = (
                                  results.takerTokenFilledAmount,
                                  results.makerTokenFilledAmount
                              );
                          }
                          /// @dev Fill an RFQ order for exactly `takerTokenFillAmount` taker tokens.
                          ///      The taker will be the caller. ETH protocol fees can be
                          ///      attached to this call. Any unspent ETH will be refunded to
                          ///      the caller.
                          /// @param order The limit order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount How much taker token to fill this order with.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillOrKillLimitOrder(
                              LibNativeOrder.LimitOrder memory order,
                              LibSignature.Signature memory signature,
                              uint128 takerTokenFillAmount
                          )
                              public
                              payable
                              returns (uint128 makerTokenFilledAmount)
                          {
                              FillNativeOrderResults memory results =
                                  _fillLimitOrderPrivate(FillLimitOrderPrivateParams({
                                      order: order,
                                      signature: signature,
                                      takerTokenFillAmount: takerTokenFillAmount,
                                      taker: msg.sender,
                                      sender: msg.sender
                                  }));
                              // Must have filled exactly the amount requested.
                              if (results.takerTokenFilledAmount < takerTokenFillAmount) {
                                  LibNativeOrdersRichErrors.FillOrKillFailedError(
                                      getLimitOrderHash(order),
                                      results.takerTokenFilledAmount,
                                      takerTokenFillAmount
                                  ).rrevert();
                              }
                              LibNativeOrder.refundExcessProtocolFeeToSender(results.ethProtocolFeePaid);
                              makerTokenFilledAmount = results.makerTokenFilledAmount;
                          }
                          /// @dev Fill an RFQ order for exactly `takerTokenFillAmount` taker tokens.
                          ///      The taker will be the caller. ETH protocol fees can be
                          ///      attached to this call. Any unspent ETH will be refunded to
                          ///      the caller.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount How much taker token to fill this order with.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function fillOrKillRfqOrder(
                              LibNativeOrder.RfqOrder memory order,
                              LibSignature.Signature memory signature,
                              uint128 takerTokenFillAmount
                          )
                              public
                              returns (uint128 makerTokenFilledAmount)
                          {
                              FillNativeOrderResults memory results =
                                  _fillRfqOrderPrivate(FillRfqOrderPrivateParams({
                                      order: order,
                                      signature: signature,
                                      takerTokenFillAmount: takerTokenFillAmount,
                                      taker: msg.sender,
                                      useSelfBalance: false,
                                      recipient: msg.sender
                                  }));
                              // Must have filled exactly the amount requested.
                              if (results.takerTokenFilledAmount < takerTokenFillAmount) {
                                  LibNativeOrdersRichErrors.FillOrKillFailedError(
                                      getRfqOrderHash(order),
                                      results.takerTokenFilledAmount,
                                      takerTokenFillAmount
                                  ).rrevert();
                              }
                              makerTokenFilledAmount = results.makerTokenFilledAmount;
                          }
                          /// @dev Fill a limit order. Internal variant. ETH protocol fees can be
                          ///      attached to this call.
                          /// @param order The limit order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token to fill this order with.
                          /// @param taker The order taker.
                          /// @param sender The order sender.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function _fillLimitOrder(
                              LibNativeOrder.LimitOrder memory order,
                              LibSignature.Signature memory signature,
                              uint128 takerTokenFillAmount,
                              address taker,
                              address sender
                          )
                              public
                              virtual
                              payable
                              onlySelf
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount)
                          {
                              FillNativeOrderResults memory results =
                                  _fillLimitOrderPrivate(FillLimitOrderPrivateParams(
                                      order,
                                      signature,
                                      takerTokenFillAmount,
                                      taker,
                                      sender
                                  ));
                              (takerTokenFilledAmount, makerTokenFilledAmount) = (
                                  results.takerTokenFilledAmount,
                                  results.makerTokenFilledAmount
                              );
                          }
                          /// @dev Fill an RFQ order. Internal variant.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @param takerTokenFillAmount Maximum taker token to fill this order with.
                          /// @param taker The order taker.
                          /// @param useSelfBalance Whether to use the ExchangeProxy's transient
                          ///        balance of taker tokens to fill the order.
                          /// @param recipient The recipient of the maker tokens.
                          /// @return takerTokenFilledAmount How much maker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function _fillRfqOrder(
                              LibNativeOrder.RfqOrder memory order,
                              LibSignature.Signature memory signature,
                              uint128 takerTokenFillAmount,
                              address taker,
                              bool useSelfBalance,
                              address recipient
                          )
                              public
                              virtual
                              onlySelf
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount)
                          {
                              FillNativeOrderResults memory results =
                                  _fillRfqOrderPrivate(FillRfqOrderPrivateParams(
                                      order,
                                      signature,
                                      takerTokenFillAmount,
                                      taker,
                                      useSelfBalance,
                                      recipient
                                  ));
                              (takerTokenFilledAmount, makerTokenFilledAmount) = (
                                  results.takerTokenFilledAmount,
                                  results.makerTokenFilledAmount
                              );
                          }
                          /// @dev Mark what tx.origin addresses are allowed to fill an order that
                          ///      specifies the message sender as its txOrigin.
                          /// @param origins An array of origin addresses to update.
                          /// @param allowed True to register, false to unregister.
                          function registerAllowedRfqOrigins(
                              address[] memory origins,
                              bool allowed
                          )
                              external
                          {
                              require(msg.sender == tx.origin,
                                  "NativeOrdersFeature/NO_CONTRACT_ORIGINS");
                              LibNativeOrdersStorage.Storage storage stor =
                                  LibNativeOrdersStorage.getStorage();
                              for (uint256 i = 0; i < origins.length; i++) {
                                  stor.originRegistry[msg.sender][origins[i]] = allowed;
                              }
                              emit RfqOrderOriginsAllowed(msg.sender, origins, allowed);
                          }
                          /// @dev Fill a limit order. Private variant. Does not refund protocol fees.
                          /// @param params Function params.
                          /// @return results Results of the fill.
                          function _fillLimitOrderPrivate(FillLimitOrderPrivateParams memory params)
                              private
                              returns (FillNativeOrderResults memory results)
                          {
                              LibNativeOrder.OrderInfo memory orderInfo = getLimitOrderInfo(params.order);
                              // Must be fillable.
                              if (orderInfo.status != LibNativeOrder.OrderStatus.FILLABLE) {
                                  LibNativeOrdersRichErrors.OrderNotFillableError(
                                      orderInfo.orderHash,
                                      uint8(orderInfo.status)
                                  ).rrevert();
                              }
                              // Must be fillable by the taker.
                              if (params.order.taker != address(0) && params.order.taker != params.taker) {
                                  LibNativeOrdersRichErrors.OrderNotFillableByTakerError(
                                      orderInfo.orderHash,
                                      params.taker,
                                      params.order.taker
                                  ).rrevert();
                              }
                              // Must be fillable by the sender.
                              if (params.order.sender != address(0) && params.order.sender != params.sender) {
                                  LibNativeOrdersRichErrors.OrderNotFillableBySenderError(
                                      orderInfo.orderHash,
                                      params.sender,
                                      params.order.sender
                                  ).rrevert();
                              }
                              // Signature must be valid for the order.
                              {
                                  address signer = LibSignature.getSignerOfHash(
                                      orderInfo.orderHash,
                                      params.signature
                                  );
                                  if (signer != params.order.maker && !isValidOrderSigner(params.order.maker, signer)) {
                                      LibNativeOrdersRichErrors.OrderNotSignedByMakerError(
                                          orderInfo.orderHash,
                                          signer,
                                          params.order.maker
                                      ).rrevert();
                                  }
                              }
                              // Pay the protocol fee.
                              results.ethProtocolFeePaid = _collectProtocolFee(params.order.pool);
                              // Settle between the maker and taker.
                              (results.takerTokenFilledAmount, results.makerTokenFilledAmount) = _settleOrder(
                                  SettleOrderInfo({
                                      orderHash: orderInfo.orderHash,
                                      maker: params.order.maker,
                                      payer: params.taker,
                                      recipient: params.taker,
                                      makerToken: IERC20TokenV06(params.order.makerToken),
                                      takerToken: IERC20TokenV06(params.order.takerToken),
                                      makerAmount: params.order.makerAmount,
                                      takerAmount: params.order.takerAmount,
                                      takerTokenFillAmount: params.takerTokenFillAmount,
                                      takerTokenFilledAmount: orderInfo.takerTokenFilledAmount
                                  })
                              );
                              // Pay the fee recipient.
                              if (params.order.takerTokenFeeAmount > 0) {
                                  results.takerTokenFeeFilledAmount = uint128(LibMathV06.getPartialAmountFloor(
                                      results.takerTokenFilledAmount,
                                      params.order.takerAmount,
                                      params.order.takerTokenFeeAmount
                                  ));
                                  _transferERC20TokensFrom(
                                      params.order.takerToken,
                                      params.taker,
                                      params.order.feeRecipient,
                                      uint256(results.takerTokenFeeFilledAmount)
                                  );
                              }
                              emit LimitOrderFilled(
                                  orderInfo.orderHash,
                                  params.order.maker,
                                  params.taker,
                                  params.order.feeRecipient,
                                  address(params.order.makerToken),
                                  address(params.order.takerToken),
                                  results.takerTokenFilledAmount,
                                  results.makerTokenFilledAmount,
                                  results.takerTokenFeeFilledAmount,
                                  results.ethProtocolFeePaid,
                                  params.order.pool
                              );
                          }
                          /// @dev Fill an RFQ order. Private variant.
                          /// @param params Function params.
                          /// @return results Results of the fill.
                          function _fillRfqOrderPrivate(FillRfqOrderPrivateParams memory params)
                              private
                              returns (FillNativeOrderResults memory results)
                          {
                              LibNativeOrder.OrderInfo memory orderInfo = getRfqOrderInfo(params.order);
                              // Must be fillable.
                              if (orderInfo.status != LibNativeOrder.OrderStatus.FILLABLE) {
                                  LibNativeOrdersRichErrors.OrderNotFillableError(
                                      orderInfo.orderHash,
                                      uint8(orderInfo.status)
                                  ).rrevert();
                              }
                              {
                                  LibNativeOrdersStorage.Storage storage stor =
                                      LibNativeOrdersStorage.getStorage();
                                  // Must be fillable by the tx.origin.
                                  if (
                                      params.order.txOrigin != tx.origin &&
                                      !stor.originRegistry[params.order.txOrigin][tx.origin]
                                  ) {
                                      LibNativeOrdersRichErrors.OrderNotFillableByOriginError(
                                          orderInfo.orderHash,
                                          tx.origin,
                                          params.order.txOrigin
                                      ).rrevert();
                                  }
                              }
                              // Must be fillable by the taker.
                              if (params.order.taker != address(0) && params.order.taker != params.taker) {
                                  LibNativeOrdersRichErrors.OrderNotFillableByTakerError(
                                      orderInfo.orderHash,
                                      params.taker,
                                      params.order.taker
                                  ).rrevert();
                              }
                              // Signature must be valid for the order.
                              {
                                  address signer = LibSignature.getSignerOfHash(
                                      orderInfo.orderHash,
                                      params.signature
                                  );
                                  if (
                                      signer != params.order.maker &&
                                      !isValidOrderSigner(params.order.maker, signer)
                                  ) {
                                      LibNativeOrdersRichErrors.OrderNotSignedByMakerError(
                                          orderInfo.orderHash,
                                          signer,
                                          params.order.maker
                                      ).rrevert();
                                  }
                              }
                              // Settle between the maker and taker.
                              (results.takerTokenFilledAmount, results.makerTokenFilledAmount) = _settleOrder(
                                  SettleOrderInfo({
                                      orderHash: orderInfo.orderHash,
                                      maker: params.order.maker,
                                      payer: params.useSelfBalance ? address(this) : params.taker,
                                      recipient: params.recipient,
                                      makerToken: IERC20TokenV06(params.order.makerToken),
                                      takerToken: IERC20TokenV06(params.order.takerToken),
                                      makerAmount: params.order.makerAmount,
                                      takerAmount: params.order.takerAmount,
                                      takerTokenFillAmount: params.takerTokenFillAmount,
                                      takerTokenFilledAmount: orderInfo.takerTokenFilledAmount
                                  })
                              );
                              emit RfqOrderFilled(
                                  orderInfo.orderHash,
                                  params.order.maker,
                                  params.taker,
                                  address(params.order.makerToken),
                                  address(params.order.takerToken),
                                  results.takerTokenFilledAmount,
                                  results.makerTokenFilledAmount,
                                  params.order.pool
                              );
                          }
                          /// @dev Settle the trade between an order's maker and taker.
                          /// @param settleInfo Information needed to execute the settlement.
                          /// @return takerTokenFilledAmount How much taker token was filled.
                          /// @return makerTokenFilledAmount How much maker token was filled.
                          function _settleOrder(SettleOrderInfo memory settleInfo)
                              private
                              returns (uint128 takerTokenFilledAmount, uint128 makerTokenFilledAmount)
                          {
                              // Clamp the taker token fill amount to the fillable amount.
                              takerTokenFilledAmount = LibSafeMathV06.min128(
                                  settleInfo.takerTokenFillAmount,
                                  settleInfo.takerAmount.safeSub128(settleInfo.takerTokenFilledAmount)
                              );
                              // Compute the maker token amount.
                              // This should never overflow because the values are all clamped to
                              // (2^128-1).
                              makerTokenFilledAmount = uint128(LibMathV06.getPartialAmountFloor(
                                  uint256(takerTokenFilledAmount),
                                  uint256(settleInfo.takerAmount),
                                  uint256(settleInfo.makerAmount)
                              ));
                              if (takerTokenFilledAmount == 0 || makerTokenFilledAmount == 0) {
                                  // Nothing to do.
                                  return (0, 0);
                              }
                              // Update filled state for the order.
                              LibNativeOrdersStorage
                                  .getStorage()
                                  .orderHashToTakerTokenFilledAmount[settleInfo.orderHash] =
                                  // OK to overwrite the whole word because we shouldn't get to this
                                  // function if the order is cancelled.
                                      settleInfo.takerTokenFilledAmount.safeAdd128(takerTokenFilledAmount);
                              if (settleInfo.payer == address(this)) {
                                  // Transfer this -> maker.
                                  _transferERC20Tokens(
                                      settleInfo.takerToken,
                                      settleInfo.maker,
                                      takerTokenFilledAmount
                                  );
                              } else {
                                  // Transfer taker -> maker.
                                  _transferERC20TokensFrom(
                                      settleInfo.takerToken,
                                      settleInfo.payer,
                                      settleInfo.maker,
                                      takerTokenFilledAmount
                                  );
                              }
                              // Transfer maker -> recipient.
                              _transferERC20TokensFrom(
                                  settleInfo.makerToken,
                                  settleInfo.maker,
                                  settleInfo.recipient,
                                  makerTokenFilledAmount
                              );
                          }
                          /// @dev register a signer who can sign on behalf of msg.sender
                          /// @param signer The address from which you plan to generate signatures
                          /// @param allowed True to register, false to unregister.
                          function registerAllowedOrderSigner(
                              address signer,
                              bool allowed
                          )
                              external
                          {
                              LibNativeOrdersStorage.Storage storage stor =
                                  LibNativeOrdersStorage.getStorage();
                              stor.orderSignerRegistry[msg.sender][signer] = allowed;
                              emit OrderSignerRegistered(msg.sender, signer, allowed);
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./IERC20TokenV06.sol";
                      interface IEtherTokenV06 is
                          IERC20TokenV06
                      {
                          /// @dev Wrap ether.
                          function deposit() external payable;
                          /// @dev Unwrap ether.
                          function withdraw(uint256 amount) external;
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2019 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./LibSafeMathV06.sol";
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibMathRichErrorsV06.sol";
                      library LibMathV06 {
                          using LibSafeMathV06 for uint256;
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          ///      Reverts if rounding error is >= 0.1%
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded down.
                          function safeGetPartialAmountFloor(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              if (isRoundingErrorFloor(
                                      numerator,
                                      denominator,
                                      target
                              )) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.RoundingError(
                                      numerator,
                                      denominator,
                                      target
                                  ));
                              }
                              partialAmount = numerator.safeMul(target).safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          ///      Reverts if rounding error is >= 0.1%
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded up.
                          function safeGetPartialAmountCeil(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              if (isRoundingErrorCeil(
                                      numerator,
                                      denominator,
                                      target
                              )) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.RoundingError(
                                      numerator,
                                      denominator,
                                      target
                                  ));
                              }
                              // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
                              //       ceil(a / b) = floor((a + b - 1) / b)
                              // To implement `ceil(a / b)` using safeDiv.
                              partialAmount = numerator.safeMul(target)
                                  .safeAdd(denominator.safeSub(1))
                                  .safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded down.
                          function getPartialAmountFloor(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              partialAmount = numerator.safeMul(target).safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Calculates partial value given a numerator and denominator rounded down.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to calculate partial of.
                          /// @return partialAmount Partial value of target rounded up.
                          function getPartialAmountCeil(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (uint256 partialAmount)
                          {
                              // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
                              //       ceil(a / b) = floor((a + b - 1) / b)
                              // To implement `ceil(a / b)` using safeDiv.
                              partialAmount = numerator.safeMul(target)
                                  .safeAdd(denominator.safeSub(1))
                                  .safeDiv(denominator);
                              return partialAmount;
                          }
                          /// @dev Checks if rounding error >= 0.1% when rounding down.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to multiply with numerator/denominator.
                          /// @return isError Rounding error is present.
                          function isRoundingErrorFloor(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (bool isError)
                          {
                              if (denominator == 0) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.DivisionByZeroError());
                              }
                              // The absolute rounding error is the difference between the rounded
                              // value and the ideal value. The relative rounding error is the
                              // absolute rounding error divided by the absolute value of the
                              // ideal value. This is undefined when the ideal value is zero.
                              //
                              // The ideal value is `numerator * target / denominator`.
                              // Let's call `numerator * target % denominator` the remainder.
                              // The absolute error is `remainder / denominator`.
                              //
                              // When the ideal value is zero, we require the absolute error to
                              // be zero. Fortunately, this is always the case. The ideal value is
                              // zero iff `numerator == 0` and/or `target == 0`. In this case the
                              // remainder and absolute error are also zero.
                              if (target == 0 || numerator == 0) {
                                  return false;
                              }
                              // Otherwise, we want the relative rounding error to be strictly
                              // less than 0.1%.
                              // The relative error is `remainder / (numerator * target)`.
                              // We want the relative error less than 1 / 1000:
                              //        remainder / (numerator * denominator)  <  1 / 1000
                              // or equivalently:
                              //        1000 * remainder  <  numerator * target
                              // so we have a rounding error iff:
                              //        1000 * remainder  >=  numerator * target
                              uint256 remainder = mulmod(
                                  target,
                                  numerator,
                                  denominator
                              );
                              isError = remainder.safeMul(1000) >= numerator.safeMul(target);
                              return isError;
                          }
                          /// @dev Checks if rounding error >= 0.1% when rounding up.
                          /// @param numerator Numerator.
                          /// @param denominator Denominator.
                          /// @param target Value to multiply with numerator/denominator.
                          /// @return isError Rounding error is present.
                          function isRoundingErrorCeil(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (bool isError)
                          {
                              if (denominator == 0) {
                                  LibRichErrorsV06.rrevert(LibMathRichErrorsV06.DivisionByZeroError());
                              }
                              // See the comments in `isRoundingError`.
                              if (target == 0 || numerator == 0) {
                                  // When either is zero, the ideal value and rounded value are zero
                                  // and there is no rounding error. (Although the relative error
                                  // is undefined.)
                                  return false;
                              }
                              // Compute remainder as before
                              uint256 remainder = mulmod(
                                  target,
                                  numerator,
                                  denominator
                              );
                              remainder = denominator.safeSub(remainder) % denominator;
                              isError = remainder.safeMul(1000) >= numerator.safeMul(target);
                              return isError;
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibMathRichErrorsV06 {
                          // bytes4(keccak256("DivisionByZeroError()"))
                          bytes internal constant DIVISION_BY_ZERO_ERROR =
                              hex"a791837c";
                          // bytes4(keccak256("RoundingError(uint256,uint256,uint256)"))
                          bytes4 internal constant ROUNDING_ERROR_SELECTOR =
                              0x339f3de2;
                          // solhint-disable func-name-mixedcase
                          function DivisionByZeroError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return DIVISION_BY_ZERO_ERROR;
                          }
                          function RoundingError(
                              uint256 numerator,
                              uint256 denominator,
                              uint256 target
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  ROUNDING_ERROR_SELECTOR,
                                  numerator,
                                  denominator,
                                  target
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../errors/LibCommonRichErrors.sol";
                      import "../errors/LibOwnableRichErrors.sol";
                      import "../features/interfaces/IOwnableFeature.sol";
                      import "../features/interfaces/ISimpleFunctionRegistryFeature.sol";
                      /// @dev Common feature utilities.
                      abstract contract FixinCommon {
                          using LibRichErrorsV06 for bytes;
                          /// @dev The implementation address of this feature.
                          address internal immutable _implementation;
                          /// @dev The caller must be this contract.
                          modifier onlySelf() virtual {
                              if (msg.sender != address(this)) {
                                  LibCommonRichErrors.OnlyCallableBySelfError(msg.sender).rrevert();
                              }
                              _;
                          }
                          /// @dev The caller of this function must be the owner.
                          modifier onlyOwner() virtual {
                              {
                                  address owner = IOwnableFeature(address(this)).owner();
                                  if (msg.sender != owner) {
                                      LibOwnableRichErrors.OnlyOwnerError(
                                          msg.sender,
                                          owner
                                      ).rrevert();
                                  }
                              }
                              _;
                          }
                          constructor() internal {
                              // Remember this feature's original address.
                              _implementation = address(this);
                          }
                          /// @dev Registers a function implemented by this feature at `_implementation`.
                          ///      Can and should only be called within a `migrate()`.
                          /// @param selector The selector of the function whose implementation
                          ///        is at `_implementation`.
                          function _registerFeatureFunction(bytes4 selector)
                              internal
                          {
                              ISimpleFunctionRegistryFeature(address(this)).extend(selector, _implementation);
                          }
                          /// @dev Encode a feature version as a `uint256`.
                          /// @param major The major version number of the feature.
                          /// @param minor The minor version number of the feature.
                          /// @param revision The revision number of the feature.
                          /// @return encodedVersion The encoded version number.
                          function _encodeVersion(uint32 major, uint32 minor, uint32 revision)
                              internal
                              pure
                              returns (uint256 encodedVersion)
                          {
                              return (uint256(major) << 64) | (uint256(minor) << 32) | uint256(revision);
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibCommonRichErrors {
                          // solhint-disable func-name-mixedcase
                          function OnlyCallableBySelfError(address sender)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("OnlyCallableBySelfError(address)")),
                                  sender
                              );
                          }
                          function IllegalReentrancyError(bytes4 selector, uint256 reentrancyFlags)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  bytes4(keccak256("IllegalReentrancyError(bytes4,uint256)")),
                                  selector,
                                  reentrancyFlags
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/interfaces/IOwnableV06.sol";
                      // solhint-disable no-empty-blocks
                      /// @dev Owner management and migration features.
                      interface IOwnableFeature is
                          IOwnableV06
                      {
                          /// @dev Emitted when `migrate()` is called.
                          /// @param caller The caller of `migrate()`.
                          /// @param migrator The migration contract.
                          /// @param newOwner The address of the new owner.
                          event Migrated(address caller, address migrator, address newOwner);
                          /// @dev Execute a migration function in the context of the ZeroEx contract.
                          ///      The result of the function being called should be the magic bytes
                          ///      0x2c64c5ef (`keccack('MIGRATE_SUCCESS')`). Only callable by the owner.
                          ///      The owner will be temporarily set to `address(this)` inside the call.
                          ///      Before returning, the owner will be set to `newOwner`.
                          /// @param target The migrator contract address.
                          /// @param newOwner The address of the new owner.
                          /// @param data The call data.
                          function migrate(address target, bytes calldata data, address newOwner) external;
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      interface IOwnableV06 {
                          /// @dev Emitted by Ownable when ownership is transferred.
                          /// @param previousOwner The previous owner of the contract.
                          /// @param newOwner The new owner of the contract.
                          event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
                          /// @dev Transfers ownership of the contract to a new address.
                          /// @param newOwner The address that will become the owner.
                          function transferOwnership(address newOwner) external;
                          /// @dev The owner of this contract.
                          /// @return ownerAddress The owner address.
                          function owner() external view returns (address ownerAddress);
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Basic registry management features.
                      interface ISimpleFunctionRegistryFeature {
                          /// @dev A function implementation was updated via `extend()` or `rollback()`.
                          /// @param selector The function selector.
                          /// @param oldImpl The implementation contract address being replaced.
                          /// @param newImpl The replacement implementation contract address.
                          event ProxyFunctionUpdated(bytes4 indexed selector, address oldImpl, address newImpl);
                          /// @dev Roll back to a prior implementation of a function.
                          /// @param selector The function selector.
                          /// @param targetImpl The address of an older implementation of the function.
                          function rollback(bytes4 selector, address targetImpl) external;
                          /// @dev Register or replace a function.
                          /// @param selector The function selector.
                          /// @param impl The implementation contract for the function.
                          function extend(bytes4 selector, address impl) external;
                          /// @dev Retrieve the length of the rollback history for a function.
                          /// @param selector The function selector.
                          /// @return rollbackLength The number of items in the rollback history for
                          ///         the function.
                          function getRollbackLength(bytes4 selector)
                              external
                              view
                              returns (uint256 rollbackLength);
                          /// @dev Retrieve an entry in the rollback history for a function.
                          /// @param selector The function selector.
                          /// @param idx The index in the rollback history.
                          /// @return impl An implementation address for the function at
                          ///         index `idx`.
                          function getRollbackEntryAtIndex(bytes4 selector, uint256 idx)
                              external
                              view
                              returns (address impl);
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "./LibStorage.sol";
                      /// @dev Storage helpers for `NativeOrdersFeature`.
                      library LibNativeOrdersStorage {
                          /// @dev Storage bucket for this feature.
                          struct Storage {
                              // How much taker token has been filled in order.
                              // The lower `uint128` is the taker token fill amount.
                              // The high bit will be `1` if the order was directly cancelled.
                              mapping(bytes32 => uint256) orderHashToTakerTokenFilledAmount;
                              // The minimum valid order salt for a given maker and order pair (maker, taker)
                              // for limit orders.
                              mapping(address => mapping(address => mapping(address => uint256)))
                                  limitOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt;
                              // The minimum valid order salt for a given maker and order pair (maker, taker)
                              // for RFQ orders.
                              mapping(address => mapping(address => mapping(address => uint256)))
                                  rfqOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt;
                              // For a given order origin, which tx.origin addresses are allowed to
                              // fill the order.
                              mapping(address => mapping(address => bool)) originRegistry;
                              // For a given maker address, which addresses are allowed to
                              // sign on its behalf.
                              mapping(address => mapping(address => bool)) orderSignerRegistry;
                          }
                          /// @dev Get the storage bucket for this contract.
                          function getStorage() internal pure returns (Storage storage stor) {
                              uint256 storageSlot = LibStorage.getStorageSlot(
                                  LibStorage.StorageId.NativeOrders
                              );
                              // Dip into assembly to change the slot pointed to by the local
                              // variable `stor`.
                              // See https://solidity.readthedocs.io/en/v0.6.8/assembly.html?highlight=slot#access-to-external-variables-functions-and-libraries
                              assembly { stor_slot := storageSlot }
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Common storage helpers
                      library LibStorage {
                          /// @dev What to bit-shift a storage ID by to get its slot.
                          ///      This gives us a maximum of 2**128 inline fields in each bucket.
                          uint256 private constant STORAGE_SLOT_EXP = 128;
                          /// @dev Storage IDs for feature storage buckets.
                          ///      WARNING: APPEND-ONLY.
                          enum StorageId {
                              Proxy,
                              SimpleFunctionRegistry,
                              Ownable,
                              TokenSpender,
                              TransformERC20,
                              MetaTransactions,
                              ReentrancyGuard,
                              NativeOrders,
                              OtcOrders
                          }
                          /// @dev Get the storage slot given a storage ID. We assign unique, well-spaced
                          ///     slots to storage bucket variables to ensure they do not overlap.
                          ///     See: https://solidity.readthedocs.io/en/v0.6.6/assembly.html#access-to-external-variables-functions-and-libraries
                          /// @param storageId An entry in `StorageId`
                          /// @return slot The storage slot.
                          function getStorageSlot(StorageId storageId)
                              internal
                              pure
                              returns (uint256 slot)
                          {
                              // This should never overflow with a reasonable `STORAGE_SLOT_EXP`
                              // because Solidity will do a range check on `storageId` during the cast.
                              return (uint256(storageId) + 1) << STORAGE_SLOT_EXP;
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      interface IStaking {
                          function joinStakingPoolAsMaker(bytes32) external;
                          function payProtocolFee(address, address, uint256) external payable;
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2021 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../../errors/LibNativeOrdersRichErrors.sol";
                      import "../../storage/LibNativeOrdersStorage.sol";
                      import "../interfaces/INativeOrdersEvents.sol";
                      import "../libs/LibSignature.sol";
                      import "../libs/LibNativeOrder.sol";
                      import "./NativeOrdersInfo.sol";
                      /// @dev Feature for cancelling limit and RFQ orders.
                      abstract contract NativeOrdersCancellation is
                          INativeOrdersEvents,
                          NativeOrdersInfo
                      {
                          using LibRichErrorsV06 for bytes;
                          /// @dev Highest bit of a uint256, used to flag cancelled orders.
                          uint256 private constant HIGH_BIT = 1 << 255;
                          constructor(
                              address zeroExAddress
                          )
                              internal
                              NativeOrdersInfo(zeroExAddress)
                          {
                              // solhint-disable no-empty-blocks
                          }
                          /// @dev Cancel a single limit order. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param order The limit order.
                          function cancelLimitOrder(LibNativeOrder.LimitOrder memory order)
                              public
                          {
                              bytes32 orderHash = getLimitOrderHash(order);
                              if (msg.sender != order.maker && !isValidOrderSigner(order.maker, msg.sender)) {
                                  LibNativeOrdersRichErrors.OnlyOrderMakerAllowed(
                                      orderHash,
                                      msg.sender,
                                      order.maker
                                  ).rrevert();
                              }
                              _cancelOrderHash(orderHash, order.maker);
                          }
                          /// @dev Cancel a single RFQ order. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param order The RFQ order.
                          function cancelRfqOrder(LibNativeOrder.RfqOrder memory order)
                              public
                          {
                              bytes32 orderHash = getRfqOrderHash(order);
                              if (msg.sender != order.maker && !isValidOrderSigner(order.maker, msg.sender)) {
                                  LibNativeOrdersRichErrors.OnlyOrderMakerAllowed(
                                      orderHash,
                                      msg.sender,
                                      order.maker
                                  ).rrevert();
                              }
                              _cancelOrderHash(orderHash, order.maker);
                          }
                          /// @dev Cancel multiple limit orders. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param orders The limit orders.
                          function batchCancelLimitOrders(LibNativeOrder.LimitOrder[] memory orders)
                              public
                          {
                              for (uint256 i = 0; i < orders.length; ++i) {
                                  cancelLimitOrder(orders[i]);
                              }
                          }
                          /// @dev Cancel multiple RFQ orders. The caller must be the maker or a valid order signer.
                          ///      Silently succeeds if the order has already been cancelled.
                          /// @param orders The RFQ orders.
                          function batchCancelRfqOrders(LibNativeOrder.RfqOrder[] memory orders)
                              public
                          {
                              for (uint256 i = 0; i < orders.length; ++i) {
                                  cancelRfqOrder(orders[i]);
                              }
                          }
                          /// @dev Cancel all limit orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairLimitOrders(
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              public
                          {
                              _cancelPairLimitOrders(msg.sender, makerToken, takerToken, minValidSalt);
                          }
                          /// @dev Cancel all limit orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker the maker for whom the msg.sender is the signer.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairLimitOrdersWithSigner(
                              address maker,
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              public
                          {
                              // verify that the signer is authorized for the maker
                              if (!isValidOrderSigner(maker, msg.sender)) {
                                  LibNativeOrdersRichErrors.InvalidSignerError(
                                      maker,
                                      msg.sender
                                  ).rrevert();
                              }
                              _cancelPairLimitOrders(maker, makerToken, takerToken, minValidSalt);
                          }
                          /// @dev Cancel all limit orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairLimitOrders(
                              IERC20TokenV06[] memory makerTokens,
                              IERC20TokenV06[] memory takerTokens,
                              uint256[] memory minValidSalts
                          )
                              public
                          {
                              require(
                                  makerTokens.length == takerTokens.length &&
                                  makerTokens.length == minValidSalts.length,
                                  "NativeOrdersFeature/MISMATCHED_PAIR_ORDERS_ARRAY_LENGTHS"
                              );
                              for (uint256 i = 0; i < makerTokens.length; ++i) {
                                  _cancelPairLimitOrders(
                                      msg.sender,
                                      makerTokens[i],
                                      takerTokens[i],
                                      minValidSalts[i]
                                  );
                              }
                          }
                          /// @dev Cancel all limit orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker the maker for whom the msg.sender is the signer.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairLimitOrdersWithSigner(
                              address maker,
                              IERC20TokenV06[] memory makerTokens,
                              IERC20TokenV06[] memory takerTokens,
                              uint256[] memory minValidSalts
                          )
                              public
                          {
                              require(
                                  makerTokens.length == takerTokens.length &&
                                  makerTokens.length == minValidSalts.length,
                                  "NativeOrdersFeature/MISMATCHED_PAIR_ORDERS_ARRAY_LENGTHS"
                              );
                              if (!isValidOrderSigner(maker, msg.sender)) {
                                  LibNativeOrdersRichErrors.InvalidSignerError(
                                      maker,
                                      msg.sender
                                  ).rrevert();
                              }
                              for (uint256 i = 0; i < makerTokens.length; ++i) {
                                  _cancelPairLimitOrders(
                                      maker,
                                      makerTokens[i],
                                      takerTokens[i],
                                      minValidSalts[i]
                                  );
                              }
                          }
                          /// @dev Cancel all RFQ orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairRfqOrders(
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              public
                          {
                              _cancelPairRfqOrders(msg.sender, makerToken, takerToken, minValidSalt);
                          }
                          /// @dev Cancel all RFQ orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker the maker for whom the msg.sender is the signer.
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function cancelPairRfqOrdersWithSigner(
                              address maker,
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              public
                          {
                              if (!isValidOrderSigner(maker, msg.sender)) {
                                  LibNativeOrdersRichErrors.InvalidSignerError(
                                      maker,
                                      msg.sender
                                  ).rrevert();
                              }
                              _cancelPairRfqOrders(maker, makerToken, takerToken, minValidSalt);
                          }
                          /// @dev Cancel all RFQ orders for a given maker and pair with a salt less
                          ///      than the value provided. The caller must be the maker. Subsequent
                          ///      calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairRfqOrders(
                              IERC20TokenV06[] memory makerTokens,
                              IERC20TokenV06[] memory takerTokens,
                              uint256[] memory minValidSalts
                          )
                              public
                          {
                              require(
                                  makerTokens.length == takerTokens.length &&
                                  makerTokens.length == minValidSalts.length,
                                  "NativeOrdersFeature/MISMATCHED_PAIR_ORDERS_ARRAY_LENGTHS"
                              );
                              for (uint256 i = 0; i < makerTokens.length; ++i) {
                                  _cancelPairRfqOrders(
                                      msg.sender,
                                      makerTokens[i],
                                      takerTokens[i],
                                      minValidSalts[i]
                                  );
                              }
                          }
                          /// @dev Cancel all RFQ orders for a given maker and pairs with salts less
                          ///      than the values provided. The caller must be a signer registered to the maker.
                          ///      Subsequent calls to this function with the same caller and pair require the
                          ///      new salt to be >= the old salt.
                          /// @param maker the maker for whom the msg.sender is the signer.
                          /// @param makerTokens The maker tokens.
                          /// @param takerTokens The taker tokens.
                          /// @param minValidSalts The new minimum valid salts.
                          function batchCancelPairRfqOrdersWithSigner(
                              address maker,
                              IERC20TokenV06[] memory makerTokens,
                              IERC20TokenV06[] memory takerTokens,
                              uint256[] memory minValidSalts
                          )
                              public
                          {
                              require(
                                  makerTokens.length == takerTokens.length &&
                                  makerTokens.length == minValidSalts.length,
                                  "NativeOrdersFeature/MISMATCHED_PAIR_ORDERS_ARRAY_LENGTHS"
                              );
                              if (!isValidOrderSigner(maker, msg.sender)) {
                                  LibNativeOrdersRichErrors.InvalidSignerError(
                                      maker,
                                      msg.sender
                                  ).rrevert();
                              }
                              for (uint256 i = 0; i < makerTokens.length; ++i) {
                                  _cancelPairRfqOrders(
                                      maker,
                                      makerTokens[i],
                                      takerTokens[i],
                                      minValidSalts[i]
                                  );
                              }
                          }
                          /// @dev Cancel a limit or RFQ order directly by its order hash.
                          /// @param orderHash The order's order hash.
                          /// @param maker The order's maker.
                          function _cancelOrderHash(bytes32 orderHash, address maker)
                              private
                          {
                              LibNativeOrdersStorage.Storage storage stor =
                                  LibNativeOrdersStorage.getStorage();
                              // Set the high bit on the raw taker token fill amount to indicate
                              // a cancel. It's OK to cancel twice.
                              stor.orderHashToTakerTokenFilledAmount[orderHash] |= HIGH_BIT;
                              emit OrderCancelled(orderHash, maker);
                          }
                          /// @dev Cancel all RFQ orders for a given maker and pair with a salt less
                          ///      than the value provided.
                          /// @param maker The target maker address
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function _cancelPairRfqOrders(
                              address maker,
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              private
                          {
                              LibNativeOrdersStorage.Storage storage stor =
                                  LibNativeOrdersStorage.getStorage();
                              uint256 oldMinValidSalt =
                                  stor.rfqOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt
                                      [maker]
                                      [address(makerToken)]
                                      [address(takerToken)];
                              // New min salt must >= the old one.
                              if (oldMinValidSalt > minValidSalt) {
                                  LibNativeOrdersRichErrors.
                                      CancelSaltTooLowError(minValidSalt, oldMinValidSalt)
                                          .rrevert();
                              }
                              stor.rfqOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt
                                  [maker]
                                  [address(makerToken)]
                                  [address(takerToken)] = minValidSalt;
                              emit PairCancelledRfqOrders(
                                  maker,
                                  address(makerToken),
                                  address(takerToken),
                                  minValidSalt
                              );
                          }
                          /// @dev Cancel all limit orders for a given maker and pair with a salt less
                          ///      than the value provided.
                          /// @param maker The target maker address
                          /// @param makerToken The maker token.
                          /// @param takerToken The taker token.
                          /// @param minValidSalt The new minimum valid salt.
                          function _cancelPairLimitOrders(
                              address maker,
                              IERC20TokenV06 makerToken,
                              IERC20TokenV06 takerToken,
                              uint256 minValidSalt
                          )
                              private
                          {
                              LibNativeOrdersStorage.Storage storage stor =
                                  LibNativeOrdersStorage.getStorage();
                              uint256 oldMinValidSalt =
                                  stor.limitOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt
                                      [maker]
                                      [address(makerToken)]
                                      [address(takerToken)];
                              // New min salt must >= the old one.
                              if (oldMinValidSalt > minValidSalt) {
                                  LibNativeOrdersRichErrors.
                                      CancelSaltTooLowError(minValidSalt, oldMinValidSalt)
                                          .rrevert();
                              }
                              stor.limitOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt
                                  [maker]
                                  [address(makerToken)]
                                  [address(takerToken)] = minValidSalt;
                              emit PairCancelledLimitOrders(
                                  maker,
                                  address(makerToken),
                                  address(takerToken),
                                  minValidSalt
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2021 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IERC20TokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibMathV06.sol";
                      import "../../fixins/FixinEIP712.sol";
                      import "../../fixins/FixinTokenSpender.sol";
                      import "../../storage/LibNativeOrdersStorage.sol";
                      import "../libs/LibSignature.sol";
                      import "../libs/LibNativeOrder.sol";
                      /// @dev Feature for getting info about limit and RFQ orders.
                      abstract contract NativeOrdersInfo is
                          FixinEIP712,
                          FixinTokenSpender
                      {
                          using LibSafeMathV06 for uint256;
                          using LibRichErrorsV06 for bytes;
                          // @dev Params for `_getActualFillableTakerTokenAmount()`.
                          struct GetActualFillableTakerTokenAmountParams {
                              address maker;
                              IERC20TokenV06 makerToken;
                              uint128 orderMakerAmount;
                              uint128 orderTakerAmount;
                              LibNativeOrder.OrderInfo orderInfo;
                          }
                          /// @dev Highest bit of a uint256, used to flag cancelled orders.
                          uint256 private constant HIGH_BIT = 1 << 255;
                          constructor(
                              address zeroExAddress
                          )
                              internal
                              FixinEIP712(zeroExAddress)
                          {
                              // solhint-disable no-empty-blocks
                          }
                          /// @dev Get the order info for a limit order.
                          /// @param order The limit order.
                          /// @return orderInfo Info about the order.
                          function getLimitOrderInfo(LibNativeOrder.LimitOrder memory order)
                              public
                              view
                              returns (LibNativeOrder.OrderInfo memory orderInfo)
                          {
                              // Recover maker and compute order hash.
                              orderInfo.orderHash = getLimitOrderHash(order);
                              uint256 minValidSalt = LibNativeOrdersStorage.getStorage()
                                  .limitOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt
                                      [order.maker]
                                      [address(order.makerToken)]
                                      [address(order.takerToken)];
                              _populateCommonOrderInfoFields(
                                  orderInfo,
                                  order.takerAmount,
                                  order.expiry,
                                  order.salt,
                                  minValidSalt
                              );
                          }
                          /// @dev Get the order info for an RFQ order.
                          /// @param order The RFQ order.
                          /// @return orderInfo Info about the order.
                          function getRfqOrderInfo(LibNativeOrder.RfqOrder memory order)
                              public
                              view
                              returns (LibNativeOrder.OrderInfo memory orderInfo)
                          {
                              // Recover maker and compute order hash.
                              orderInfo.orderHash = getRfqOrderHash(order);
                              uint256 minValidSalt = LibNativeOrdersStorage.getStorage()
                                  .rfqOrdersMakerToMakerTokenToTakerTokenToMinValidOrderSalt
                                      [order.maker]
                                      [address(order.makerToken)]
                                      [address(order.takerToken)];
                              _populateCommonOrderInfoFields(
                                  orderInfo,
                                  order.takerAmount,
                                  order.expiry,
                                  order.salt,
                                  minValidSalt
                              );
                              // Check for missing txOrigin.
                              if (order.txOrigin == address(0)) {
                                  orderInfo.status = LibNativeOrder.OrderStatus.INVALID;
                              }
                          }
                          /// @dev Get the canonical hash of a limit order.
                          /// @param order The limit order.
                          /// @return orderHash The order hash.
                          function getLimitOrderHash(LibNativeOrder.LimitOrder memory order)
                              public
                              view
                              returns (bytes32 orderHash)
                          {
                              return _getEIP712Hash(
                                  LibNativeOrder.getLimitOrderStructHash(order)
                              );
                          }
                          /// @dev Get the canonical hash of an RFQ order.
                          /// @param order The RFQ order.
                          /// @return orderHash The order hash.
                          function getRfqOrderHash(LibNativeOrder.RfqOrder memory order)
                              public
                              view
                              returns (bytes32 orderHash)
                          {
                              return _getEIP712Hash(
                                  LibNativeOrder.getRfqOrderStructHash(order)
                              );
                          }
                          /// @dev Get order info, fillable amount, and signature validity for a limit order.
                          ///      Fillable amount is determined using balances and allowances of the maker.
                          /// @param order The limit order.
                          /// @param signature The order signature.
                          /// @return orderInfo Info about the order.
                          /// @return actualFillableTakerTokenAmount How much of the order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValid Whether the signature is valid.
                          function getLimitOrderRelevantState(
                              LibNativeOrder.LimitOrder memory order,
                              LibSignature.Signature calldata signature
                          )
                              public
                              view
                              returns (
                                  LibNativeOrder.OrderInfo memory orderInfo,
                                  uint128 actualFillableTakerTokenAmount,
                                  bool isSignatureValid
                              )
                          {
                              orderInfo = getLimitOrderInfo(order);
                              actualFillableTakerTokenAmount = _getActualFillableTakerTokenAmount(
                                  GetActualFillableTakerTokenAmountParams({
                                      maker: order.maker,
                                      makerToken: order.makerToken,
                                      orderMakerAmount: order.makerAmount,
                                      orderTakerAmount: order.takerAmount,
                                      orderInfo: orderInfo
                                  })
                              );
                              address signerOfHash = LibSignature.getSignerOfHash(orderInfo.orderHash, signature);
                              isSignatureValid =
                                  (order.maker == signerOfHash) ||
                                  isValidOrderSigner(order.maker, signerOfHash);
                          }
                          /// @dev Get order info, fillable amount, and signature validity for an RFQ order.
                          ///      Fillable amount is determined using balances and allowances of the maker.
                          /// @param order The RFQ order.
                          /// @param signature The order signature.
                          /// @return orderInfo Info about the order.
                          /// @return actualFillableTakerTokenAmount How much of the order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValid Whether the signature is valid.
                          function getRfqOrderRelevantState(
                              LibNativeOrder.RfqOrder memory order,
                              LibSignature.Signature memory signature
                          )
                              public
                              view
                              returns (
                                  LibNativeOrder.OrderInfo memory orderInfo,
                                  uint128 actualFillableTakerTokenAmount,
                                  bool isSignatureValid
                              )
                          {
                              orderInfo = getRfqOrderInfo(order);
                              actualFillableTakerTokenAmount = _getActualFillableTakerTokenAmount(
                                  GetActualFillableTakerTokenAmountParams({
                                      maker: order.maker,
                                      makerToken: order.makerToken,
                                      orderMakerAmount: order.makerAmount,
                                      orderTakerAmount: order.takerAmount,
                                      orderInfo: orderInfo
                                  })
                              );
                              address signerOfHash = LibSignature.getSignerOfHash(orderInfo.orderHash, signature);
                              isSignatureValid =
                                  (order.maker == signerOfHash) ||
                                  isValidOrderSigner(order.maker, signerOfHash);
                          }
                          /// @dev Batch version of `getLimitOrderRelevantState()`, without reverting.
                          ///      Orders that would normally cause `getLimitOrderRelevantState()`
                          ///      to revert will have empty results.
                          /// @param orders The limit orders.
                          /// @param signatures The order signatures.
                          /// @return orderInfos Info about the orders.
                          /// @return actualFillableTakerTokenAmounts How much of each order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValids Whether each signature is valid for the order.
                          function batchGetLimitOrderRelevantStates(
                              LibNativeOrder.LimitOrder[] calldata orders,
                              LibSignature.Signature[] calldata signatures
                          )
                              external
                              view
                              returns (
                                  LibNativeOrder.OrderInfo[] memory orderInfos,
                                  uint128[] memory actualFillableTakerTokenAmounts,
                                  bool[] memory isSignatureValids
                              )
                          {
                              require(
                                  orders.length == signatures.length,
                                  "NativeOrdersFeature/MISMATCHED_ARRAY_LENGTHS"
                              );
                              orderInfos = new LibNativeOrder.OrderInfo[](orders.length);
                              actualFillableTakerTokenAmounts = new uint128[](orders.length);
                              isSignatureValids = new bool[](orders.length);
                              for (uint256 i = 0; i < orders.length; ++i) {
                                  try
                                      this.getLimitOrderRelevantState(orders[i], signatures[i])
                                          returns (
                                              LibNativeOrder.OrderInfo memory orderInfo,
                                              uint128 actualFillableTakerTokenAmount,
                                              bool isSignatureValid
                                          )
                                  {
                                      orderInfos[i] = orderInfo;
                                      actualFillableTakerTokenAmounts[i] = actualFillableTakerTokenAmount;
                                      isSignatureValids[i] = isSignatureValid;
                                  }
                                  catch {}
                              }
                          }
                          /// @dev Batch version of `getRfqOrderRelevantState()`, without reverting.
                          ///      Orders that would normally cause `getRfqOrderRelevantState()`
                          ///      to revert will have empty results.
                          /// @param orders The RFQ orders.
                          /// @param signatures The order signatures.
                          /// @return orderInfos Info about the orders.
                          /// @return actualFillableTakerTokenAmounts How much of each order is fillable
                          ///         based on maker funds, in taker tokens.
                          /// @return isSignatureValids Whether each signature is valid for the order.
                          function batchGetRfqOrderRelevantStates(
                              LibNativeOrder.RfqOrder[] calldata orders,
                              LibSignature.Signature[] calldata signatures
                          )
                              external
                              view
                              returns (
                                  LibNativeOrder.OrderInfo[] memory orderInfos,
                                  uint128[] memory actualFillableTakerTokenAmounts,
                                  bool[] memory isSignatureValids
                              )
                          {
                              require(
                                  orders.length == signatures.length,
                                  "NativeOrdersFeature/MISMATCHED_ARRAY_LENGTHS"
                              );
                              orderInfos = new LibNativeOrder.OrderInfo[](orders.length);
                              actualFillableTakerTokenAmounts = new uint128[](orders.length);
                              isSignatureValids = new bool[](orders.length);
                              for (uint256 i = 0; i < orders.length; ++i) {
                                  try
                                      this.getRfqOrderRelevantState(orders[i], signatures[i])
                                          returns (
                                              LibNativeOrder.OrderInfo memory orderInfo,
                                              uint128 actualFillableTakerTokenAmount,
                                              bool isSignatureValid
                                          )
                                  {
                                      orderInfos[i] = orderInfo;
                                      actualFillableTakerTokenAmounts[i] = actualFillableTakerTokenAmount;
                                      isSignatureValids[i] = isSignatureValid;
                                  }
                                  catch {}
                              }
                          }
                          /// @dev Populate `status` and `takerTokenFilledAmount` fields in
                          ///      `orderInfo`, which use the same code path for both limit and
                          ///      RFQ orders.
                          /// @param orderInfo `OrderInfo` with `orderHash` and `maker` filled.
                          /// @param takerAmount The order's taker token amount..
                          /// @param expiry The order's expiry.
                          /// @param salt The order's salt.
                          /// @param salt The minimum valid salt for the maker and pair combination.
                          function _populateCommonOrderInfoFields(
                              LibNativeOrder.OrderInfo memory orderInfo,
                              uint128 takerAmount,
                              uint64 expiry,
                              uint256 salt,
                              uint256 minValidSalt
                          )
                              private
                              view
                          {
                              LibNativeOrdersStorage.Storage storage stor =
                                  LibNativeOrdersStorage.getStorage();
                              // Get the filled and direct cancel state.
                              {
                                  // The high bit of the raw taker token filled amount will be set
                                  // if the order was cancelled.
                                  uint256 rawTakerTokenFilledAmount =
                                      stor.orderHashToTakerTokenFilledAmount[orderInfo.orderHash];
                                  orderInfo.takerTokenFilledAmount = uint128(rawTakerTokenFilledAmount);
                                  if (orderInfo.takerTokenFilledAmount >= takerAmount) {
                                      orderInfo.status = LibNativeOrder.OrderStatus.FILLED;
                                      return;
                                  }
                                  if (rawTakerTokenFilledAmount & HIGH_BIT != 0) {
                                      orderInfo.status = LibNativeOrder.OrderStatus.CANCELLED;
                                      return;
                                  }
                              }
                              // Check for expiration.
                              if (expiry <= uint64(block.timestamp)) {
                                  orderInfo.status = LibNativeOrder.OrderStatus.EXPIRED;
                                  return;
                              }
                              // Check if the order was cancelled by salt.
                              if (minValidSalt > salt) {
                                  orderInfo.status = LibNativeOrder.OrderStatus.CANCELLED;
                                  return;
                              }
                              orderInfo.status = LibNativeOrder.OrderStatus.FILLABLE;
                          }
                          /// @dev Calculate the actual fillable taker token amount of an order
                          ///      based on maker allowance and balances.
                          function _getActualFillableTakerTokenAmount(
                              GetActualFillableTakerTokenAmountParams memory params
                          )
                              private
                              view
                              returns (uint128 actualFillableTakerTokenAmount)
                          {
                              if (params.orderMakerAmount == 0 || params.orderTakerAmount == 0) {
                                  // Empty order.
                                  return 0;
                              }
                              if (params.orderInfo.status != LibNativeOrder.OrderStatus.FILLABLE) {
                                  // Not fillable.
                                  return 0;
                              }
                              // Get the fillable maker amount based on the order quantities and
                              // previously filled amount
                              uint256 fillableMakerTokenAmount = LibMathV06.getPartialAmountFloor(
                                  uint256(
                                      params.orderTakerAmount
                                      - params.orderInfo.takerTokenFilledAmount
                                  ),
                                  uint256(params.orderTakerAmount),
                                  uint256(params.orderMakerAmount)
                              );
                              // Clamp it to the amount of maker tokens we can spend on behalf of the
                              // maker.
                              fillableMakerTokenAmount = LibSafeMathV06.min256(
                                  fillableMakerTokenAmount,
                                  _getSpendableERC20BalanceOf(params.makerToken, params.maker)
                              );
                              // Convert to taker token amount.
                              return LibMathV06.getPartialAmountCeil(
                                  fillableMakerTokenAmount,
                                  uint256(params.orderMakerAmount),
                                  uint256(params.orderTakerAmount)
                              ).safeDowncastToUint128();
                          }
                          /// @dev checks if a given address is registered to sign on behalf of a maker address
                          /// @param maker The maker address encoded in an order (can be a contract)
                          /// @param signer The address that is providing a signature
                          function isValidOrderSigner(
                              address maker,
                              address signer
                          )
                              public
                              view
                              returns (bool isValid)
                          {
                              // returns false if it the mapping doesn't exist
                              return LibNativeOrdersStorage.getStorage()
                                  .orderSignerRegistry
                                      [maker]
                                      [signer];
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "../errors/LibCommonRichErrors.sol";
                      import "../errors/LibOwnableRichErrors.sol";
                      /// @dev EIP712 helpers for features.
                      abstract contract FixinEIP712 {
                          /// @dev The domain hash separator for the entire exchange proxy.
                          bytes32 public immutable EIP712_DOMAIN_SEPARATOR;
                          constructor(address zeroExAddress) internal {
                              // Compute `EIP712_DOMAIN_SEPARATOR`
                              {
                                  uint256 chainId;
                                  assembly { chainId := chainid() }
                                  EIP712_DOMAIN_SEPARATOR = keccak256(
                                      abi.encode(
                                          keccak256(
                                              "EIP712Domain("
                                                  "string name,"
                                                  "string version,"
                                                  "uint256 chainId,"
                                                  "address verifyingContract"
                                              ")"
                                          ),
                                          keccak256("ZeroEx"),
                                          keccak256("1.0.0"),
                                          chainId,
                                          zeroExAddress
                                      )
                                  );
                              }
                          }
                          function _getEIP712Hash(bytes32 structHash)
                              internal
                              view
                              returns (bytes32 eip712Hash)
                          {
                              return keccak256(abi.encodePacked(
                                  hex"1901",
                                  EIP712_DOMAIN_SEPARATOR,
                                  structHash
                              ));
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      /// @dev Helpers for moving tokens around.
                      abstract contract FixinTokenSpender {
                          // Mask of the lower 20 bytes of a bytes32.
                          uint256 constant private ADDRESS_MASK = 0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff;
                          /// @dev Transfers ERC20 tokens from `owner` to `to`.
                          /// @param token The token to spend.
                          /// @param owner The owner of the tokens.
                          /// @param to The recipient of the tokens.
                          /// @param amount The amount of `token` to transfer.
                          function _transferERC20TokensFrom(
                              IERC20TokenV06 token,
                              address owner,
                              address to,
                              uint256 amount
                          )
                              internal
                          {
                              require(address(token) != address(this), "FixinTokenSpender/CANNOT_INVOKE_SELF");
                              assembly {
                                  let ptr := mload(0x40) // free memory pointer
                                  // selector for transferFrom(address,address,uint256)
                                  mstore(ptr, 0x23b872dd00000000000000000000000000000000000000000000000000000000)
                                  mstore(add(ptr, 0x04), and(owner, ADDRESS_MASK))
                                  mstore(add(ptr, 0x24), and(to, ADDRESS_MASK))
                                  mstore(add(ptr, 0x44), amount)
                                  let success := call(
                                      gas(),
                                      and(token, ADDRESS_MASK),
                                      0,
                                      ptr,
                                      0x64,
                                      ptr,
                                      32
                                  )
                                  let rdsize := returndatasize()
                                  // Check for ERC20 success. ERC20 tokens should return a boolean,
                                  // but some don't. We accept 0-length return data as success, or at
                                  // least 32 bytes that starts with a 32-byte boolean true.
                                  success := and(
                                      success,                             // call itself succeeded
                                      or(
                                          iszero(rdsize),                  // no return data, or
                                          and(
                                              iszero(lt(rdsize, 32)),      // at least 32 bytes
                                              eq(mload(ptr), 1)            // starts with uint256(1)
                                          )
                                      )
                                  )
                                  if iszero(success) {
                                      returndatacopy(ptr, 0, rdsize)
                                      revert(ptr, rdsize)
                                  }
                              }
                          }
                          /// @dev Transfers ERC20 tokens from ourselves to `to`.
                          /// @param token The token to spend.
                          /// @param to The recipient of the tokens.
                          /// @param amount The amount of `token` to transfer.
                          function _transferERC20Tokens(
                              IERC20TokenV06 token,
                              address to,
                              uint256 amount
                          )
                              internal
                          {
                              require(address(token) != address(this), "FixinTokenSpender/CANNOT_INVOKE_SELF");
                              assembly {
                                  let ptr := mload(0x40) // free memory pointer
                                  // selector for transfer(address,uint256)
                                  mstore(ptr, 0xa9059cbb00000000000000000000000000000000000000000000000000000000)
                                  mstore(add(ptr, 0x04), and(to, ADDRESS_MASK))
                                  mstore(add(ptr, 0x24), amount)
                                  let success := call(
                                      gas(),
                                      and(token, ADDRESS_MASK),
                                      0,
                                      ptr,
                                      0x44,
                                      ptr,
                                      32
                                  )
                                  let rdsize := returndatasize()
                                  // Check for ERC20 success. ERC20 tokens should return a boolean,
                                  // but some don't. We accept 0-length return data as success, or at
                                  // least 32 bytes that starts with a 32-byte boolean true.
                                  success := and(
                                      success,                             // call itself succeeded
                                      or(
                                          iszero(rdsize),                  // no return data, or
                                          and(
                                              iszero(lt(rdsize, 32)),      // at least 32 bytes
                                              eq(mload(ptr), 1)            // starts with uint256(1)
                                          )
                                      )
                                  )
                                  if iszero(success) {
                                      returndatacopy(ptr, 0, rdsize)
                                      revert(ptr, rdsize)
                                  }
                              }
                          }
                          /// @dev Gets the maximum amount of an ERC20 token `token` that can be
                          ///      pulled from `owner` by this address.
                          /// @param token The token to spend.
                          /// @param owner The owner of the tokens.
                          /// @return amount The amount of tokens that can be pulled.
                          function _getSpendableERC20BalanceOf(
                              IERC20TokenV06 token,
                              address owner
                          )
                              internal
                              view
                              returns (uint256)
                          {
                              return LibSafeMathV06.min256(
                                  token.allowance(owner, address(this)),
                                  token.balanceOf(owner)
                              );
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2021 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
                      import "../../fixins/FixinProtocolFees.sol";
                      import "../../errors/LibNativeOrdersRichErrors.sol";
                      import "../../vendor/v3/IStaking.sol";
                      /// @dev Mixin for protocol fee utility functions.
                      abstract contract NativeOrdersProtocolFees is
                          FixinProtocolFees
                      {
                          using LibSafeMathV06 for uint256;
                          using LibRichErrorsV06 for bytes;
                          constructor(
                              IEtherTokenV06 weth,
                              IStaking staking,
                              FeeCollectorController feeCollectorController,
                              uint32 protocolFeeMultiplier
                          )
                              internal
                              FixinProtocolFees(weth, staking, feeCollectorController, protocolFeeMultiplier)
                          {
                              // solhint-disable no-empty-blocks
                          }
                          /// @dev Transfers protocol fees from the `FeeCollector` pools into
                          ///      the staking contract.
                          /// @param poolIds Staking pool IDs
                          function transferProtocolFeesForPools(bytes32[] calldata poolIds)
                              external
                          {
                              for (uint256 i = 0; i < poolIds.length; ++i) {
                                  _transferFeesForPool(poolIds[i]);
                              }
                          }
                          /// @dev Get the protocol fee multiplier. This should be multiplied by the
                          ///      gas price to arrive at the required protocol fee to fill a native order.
                          /// @return multiplier The protocol fee multiplier.
                          function getProtocolFeeMultiplier()
                              external
                              view
                              returns (uint32 multiplier)
                          {
                              return PROTOCOL_FEE_MULTIPLIER;
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
                      import "../external/FeeCollector.sol";
                      import "../external/FeeCollectorController.sol";
                      import "../external/LibFeeCollector.sol";
                      import "../vendor/v3/IStaking.sol";
                      /// @dev Helpers for collecting protocol fees.
                      abstract contract FixinProtocolFees {
                          /// @dev The protocol fee multiplier.
                          uint32 public immutable PROTOCOL_FEE_MULTIPLIER;
                          /// @dev The `FeeCollectorController` contract.
                          FeeCollectorController private immutable FEE_COLLECTOR_CONTROLLER;
                          /// @dev Hash of the fee collector init code.
                          bytes32 private immutable FEE_COLLECTOR_INIT_CODE_HASH;
                          /// @dev The WETH token contract.
                          IEtherTokenV06 private immutable WETH;
                          /// @dev The staking contract.
                          IStaking private immutable STAKING;
                          constructor(
                              IEtherTokenV06 weth,
                              IStaking staking,
                              FeeCollectorController feeCollectorController,
                              uint32 protocolFeeMultiplier
                          )
                              internal
                          {
                              FEE_COLLECTOR_CONTROLLER = feeCollectorController;
                              FEE_COLLECTOR_INIT_CODE_HASH =
                                  feeCollectorController.FEE_COLLECTOR_INIT_CODE_HASH();
                              WETH = weth;
                              STAKING = staking;
                              PROTOCOL_FEE_MULTIPLIER = protocolFeeMultiplier;
                          }
                          /// @dev   Collect the specified protocol fee in ETH.
                          ///        The fee is stored in a per-pool fee collector contract.
                          /// @param poolId The pool ID for which a fee is being collected.
                          /// @return ethProtocolFeePaid How much protocol fee was collected in ETH.
                          function _collectProtocolFee(bytes32 poolId)
                              internal
                              returns (uint256 ethProtocolFeePaid)
                          {
                              uint256 protocolFeePaid = _getSingleProtocolFee();
                              if (protocolFeePaid == 0) {
                                  // Nothing to do.
                                  return 0;
                              }
                              FeeCollector feeCollector = _getFeeCollector(poolId);
                              (bool success,) = address(feeCollector).call{value: protocolFeePaid}("");
                              require(success, "FixinProtocolFees/ETHER_TRANSFER_FALIED");
                              return protocolFeePaid;
                          }
                          /// @dev Transfer fees for a given pool to the staking contract.
                          /// @param poolId Identifies the pool whose fees are being paid.
                          function _transferFeesForPool(bytes32 poolId)
                              internal
                          {
                              // This will create a FeeCollector contract (if necessary) and wrap
                              // fees for the pool ID.
                              FeeCollector feeCollector =
                                  FEE_COLLECTOR_CONTROLLER.prepareFeeCollectorToPayFees(poolId);
                              // All fees in the fee collector should be in WETH now.
                              uint256 bal = WETH.balanceOf(address(feeCollector));
                              if (bal > 1) {
                                  // Leave 1 wei behind to avoid high SSTORE cost of zero-->non-zero.
                                  STAKING.payProtocolFee(
                                      address(feeCollector),
                                      address(feeCollector),
                                      bal - 1);
                              }
                          }
                          /// @dev Compute the CREATE2 address for a fee collector.
                          /// @param poolId The fee collector's pool ID.
                          function _getFeeCollector(bytes32 poolId)
                              internal
                              view
                              returns (FeeCollector)
                          {
                              return FeeCollector(LibFeeCollector.getFeeCollectorAddress(
                                  address(FEE_COLLECTOR_CONTROLLER),
                                  FEE_COLLECTOR_INIT_CODE_HASH,
                                  poolId
                              ));
                          }
                          /// @dev Get the cost of a single protocol fee.
                          /// @return protocolFeeAmount The protocol fee amount, in ETH/WETH.
                          function _getSingleProtocolFee()
                              internal
                              view
                              returns (uint256 protocolFeeAmount)
                          {
                              return uint256(PROTOCOL_FEE_MULTIPLIER) * tx.gasprice;
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
                      import "@0x/contracts-utils/contracts/src/v06/AuthorizableV06.sol";
                      import "../vendor/v3/IStaking.sol";
                      /// @dev The collector contract for protocol fees
                      contract FeeCollector is AuthorizableV06 {
                          /// @dev Allow ether transfers to the collector.
                          receive() external payable { }
                          constructor() public {
                              _addAuthorizedAddress(msg.sender);
                          }
                          /// @dev   Approve the staking contract and join a pool. Only an authority
                          ///        can call this.
                          /// @param weth The WETH contract.
                          /// @param staking The staking contract.
                          /// @param poolId The pool ID this contract is collecting fees for.
                          function initialize(
                              IEtherTokenV06 weth,
                              IStaking staking,
                              bytes32 poolId
                          )
                              external
                              onlyAuthorized
                          {
                              weth.approve(address(staking), type(uint256).max);
                              staking.joinStakingPoolAsMaker(poolId);
                          }
                          /// @dev Convert all held ether to WETH. Only an authority can call this.
                          /// @param weth The WETH contract.
                          function convertToWeth(
                              IEtherTokenV06 weth
                          )
                              external
                              onlyAuthorized
                          {
                              if (address(this).balance > 0) {
                                  weth.deposit{value: address(this).balance}();
                              }
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./interfaces/IAuthorizableV06.sol";
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibAuthorizableRichErrorsV06.sol";
                      import "./OwnableV06.sol";
                      // solhint-disable no-empty-blocks
                      contract AuthorizableV06 is
                          OwnableV06,
                          IAuthorizableV06
                      {
                          /// @dev Only authorized addresses can invoke functions with this modifier.
                          modifier onlyAuthorized {
                              _assertSenderIsAuthorized();
                              _;
                          }
                          // @dev Whether an address is authorized to call privileged functions.
                          // @param 0 Address to query.
                          // @return 0 Whether the address is authorized.
                          mapping (address => bool) public override authorized;
                          // @dev Whether an address is authorized to call privileged functions.
                          // @param 0 Index of authorized address.
                          // @return 0 Authorized address.
                          address[] public override authorities;
                          /// @dev Initializes the `owner` address.
                          constructor()
                              public
                              OwnableV06()
                          {}
                          /// @dev Authorizes an address.
                          /// @param target Address to authorize.
                          function addAuthorizedAddress(address target)
                              external
                              override
                              onlyOwner
                          {
                              _addAuthorizedAddress(target);
                          }
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          function removeAuthorizedAddress(address target)
                              external
                              override
                              onlyOwner
                          {
                              if (!authorized[target]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetNotAuthorizedError(target));
                              }
                              for (uint256 i = 0; i < authorities.length; i++) {
                                  if (authorities[i] == target) {
                                      _removeAuthorizedAddressAtIndex(target, i);
                                      break;
                                  }
                              }
                          }
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          /// @param index Index of target in authorities array.
                          function removeAuthorizedAddressAtIndex(
                              address target,
                              uint256 index
                          )
                              external
                              override
                              onlyOwner
                          {
                              _removeAuthorizedAddressAtIndex(target, index);
                          }
                          /// @dev Gets all authorized addresses.
                          /// @return Array of authorized addresses.
                          function getAuthorizedAddresses()
                              external
                              override
                              view
                              returns (address[] memory)
                          {
                              return authorities;
                          }
                          /// @dev Reverts if msg.sender is not authorized.
                          function _assertSenderIsAuthorized()
                              internal
                              view
                          {
                              if (!authorized[msg.sender]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.SenderNotAuthorizedError(msg.sender));
                              }
                          }
                          /// @dev Authorizes an address.
                          /// @param target Address to authorize.
                          function _addAuthorizedAddress(address target)
                              internal
                          {
                              // Ensure that the target is not the zero address.
                              if (target == address(0)) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.ZeroCantBeAuthorizedError());
                              }
                              // Ensure that the target is not already authorized.
                              if (authorized[target]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetAlreadyAuthorizedError(target));
                              }
                              authorized[target] = true;
                              authorities.push(target);
                              emit AuthorizedAddressAdded(target, msg.sender);
                          }
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          /// @param index Index of target in authorities array.
                          function _removeAuthorizedAddressAtIndex(
                              address target,
                              uint256 index
                          )
                              internal
                          {
                              if (!authorized[target]) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.TargetNotAuthorizedError(target));
                              }
                              if (index >= authorities.length) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.IndexOutOfBoundsError(
                                      index,
                                      authorities.length
                                  ));
                              }
                              if (authorities[index] != target) {
                                  LibRichErrorsV06.rrevert(LibAuthorizableRichErrorsV06.AuthorizedAddressMismatchError(
                                      authorities[index],
                                      target
                                  ));
                              }
                              delete authorized[target];
                              authorities[index] = authorities[authorities.length - 1];
                              authorities.pop();
                              emit AuthorizedAddressRemoved(target, msg.sender);
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./IOwnableV06.sol";
                      interface IAuthorizableV06 is
                          IOwnableV06
                      {
                          // Event logged when a new address is authorized.
                          event AuthorizedAddressAdded(
                              address indexed target,
                              address indexed caller
                          );
                          // Event logged when a currently authorized address is unauthorized.
                          event AuthorizedAddressRemoved(
                              address indexed target,
                              address indexed caller
                          );
                          /// @dev Authorizes an address.
                          /// @param target Address to authorize.
                          function addAuthorizedAddress(address target)
                              external;
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          function removeAuthorizedAddress(address target)
                              external;
                          /// @dev Removes authorizion of an address.
                          /// @param target Address to remove authorization from.
                          /// @param index Index of target in authorities array.
                          function removeAuthorizedAddressAtIndex(
                              address target,
                              uint256 index
                          )
                              external;
                          /// @dev Gets all authorized addresses.
                          /// @return authorizedAddresses Array of authorized addresses.
                          function getAuthorizedAddresses()
                              external
                              view
                              returns (address[] memory authorizedAddresses);
                          /// @dev Whether an adderss is authorized to call privileged functions.
                          /// @param addr Address to query.
                          /// @return isAuthorized Whether the address is authorized.
                          function authorized(address addr) external view returns (bool isAuthorized);
                          /// @dev All addresseses authorized to call privileged functions.
                          /// @param idx Index of authorized address.
                          /// @return addr Authorized address.
                          function authorities(uint256 idx) external view returns (address addr);
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibAuthorizableRichErrorsV06 {
                          // bytes4(keccak256("AuthorizedAddressMismatchError(address,address)"))
                          bytes4 internal constant AUTHORIZED_ADDRESS_MISMATCH_ERROR_SELECTOR =
                              0x140a84db;
                          // bytes4(keccak256("IndexOutOfBoundsError(uint256,uint256)"))
                          bytes4 internal constant INDEX_OUT_OF_BOUNDS_ERROR_SELECTOR =
                              0xe9f83771;
                          // bytes4(keccak256("SenderNotAuthorizedError(address)"))
                          bytes4 internal constant SENDER_NOT_AUTHORIZED_ERROR_SELECTOR =
                              0xb65a25b9;
                          // bytes4(keccak256("TargetAlreadyAuthorizedError(address)"))
                          bytes4 internal constant TARGET_ALREADY_AUTHORIZED_ERROR_SELECTOR =
                              0xde16f1a0;
                          // bytes4(keccak256("TargetNotAuthorizedError(address)"))
                          bytes4 internal constant TARGET_NOT_AUTHORIZED_ERROR_SELECTOR =
                              0xeb5108a2;
                          // bytes4(keccak256("ZeroCantBeAuthorizedError()"))
                          bytes internal constant ZERO_CANT_BE_AUTHORIZED_ERROR_BYTES =
                              hex"57654fe4";
                          // solhint-disable func-name-mixedcase
                          function AuthorizedAddressMismatchError(
                              address authorized,
                              address target
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  AUTHORIZED_ADDRESS_MISMATCH_ERROR_SELECTOR,
                                  authorized,
                                  target
                              );
                          }
                          function IndexOutOfBoundsError(
                              uint256 index,
                              uint256 length
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  INDEX_OUT_OF_BOUNDS_ERROR_SELECTOR,
                                  index,
                                  length
                              );
                          }
                          function SenderNotAuthorizedError(address sender)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  SENDER_NOT_AUTHORIZED_ERROR_SELECTOR,
                                  sender
                              );
                          }
                          function TargetAlreadyAuthorizedError(address target)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  TARGET_ALREADY_AUTHORIZED_ERROR_SELECTOR,
                                  target
                              );
                          }
                          function TargetNotAuthorizedError(address target)
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  TARGET_NOT_AUTHORIZED_ERROR_SELECTOR,
                                  target
                              );
                          }
                          function ZeroCantBeAuthorizedError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return ZERO_CANT_BE_AUTHORIZED_ERROR_BYTES;
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2019 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      import "./interfaces/IOwnableV06.sol";
                      import "./errors/LibRichErrorsV06.sol";
                      import "./errors/LibOwnableRichErrorsV06.sol";
                      contract OwnableV06 is
                          IOwnableV06
                      {
                          /// @dev The owner of this contract.
                          /// @return 0 The owner address.
                          address public override owner;
                          constructor() public {
                              owner = msg.sender;
                          }
                          modifier onlyOwner() {
                              _assertSenderIsOwner();
                              _;
                          }
                          /// @dev Change the owner of this contract.
                          /// @param newOwner New owner address.
                          function transferOwnership(address newOwner)
                              public
                              override
                              onlyOwner
                          {
                              if (newOwner == address(0)) {
                                  LibRichErrorsV06.rrevert(LibOwnableRichErrorsV06.TransferOwnerToZeroError());
                              } else {
                                  owner = newOwner;
                                  emit OwnershipTransferred(msg.sender, newOwner);
                              }
                          }
                          function _assertSenderIsOwner()
                              internal
                              view
                          {
                              if (msg.sender != owner) {
                                  LibRichErrorsV06.rrevert(LibOwnableRichErrorsV06.OnlyOwnerError(
                                      msg.sender,
                                      owner
                                  ));
                              }
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      library LibOwnableRichErrorsV06 {
                          // bytes4(keccak256("OnlyOwnerError(address,address)"))
                          bytes4 internal constant ONLY_OWNER_ERROR_SELECTOR =
                              0x1de45ad1;
                          // bytes4(keccak256("TransferOwnerToZeroError()"))
                          bytes internal constant TRANSFER_OWNER_TO_ZERO_ERROR_BYTES =
                              hex"e69edc3e";
                          // solhint-disable func-name-mixedcase
                          function OnlyOwnerError(
                              address sender,
                              address owner
                          )
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return abi.encodeWithSelector(
                                  ONLY_OWNER_ERROR_SELECTOR,
                                  sender,
                                  owner
                              );
                          }
                          function TransferOwnerToZeroError()
                              internal
                              pure
                              returns (bytes memory)
                          {
                              return TRANSFER_OWNER_TO_ZERO_ERROR_BYTES;
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
                      import "../vendor/v3/IStaking.sol";
                      import "./FeeCollector.sol";
                      import "./LibFeeCollector.sol";
                      /// @dev A contract that manages `FeeCollector` contracts.
                      contract FeeCollectorController {
                          /// @dev Hash of the fee collector init code.
                          bytes32 public immutable FEE_COLLECTOR_INIT_CODE_HASH;
                          /// @dev The WETH contract.
                          IEtherTokenV06 private immutable WETH;
                          /// @dev The staking contract.
                          IStaking private immutable STAKING;
                          constructor(
                              IEtherTokenV06 weth,
                              IStaking staking
                          )
                              public
                          {
                              FEE_COLLECTOR_INIT_CODE_HASH = keccak256(type(FeeCollector).creationCode);
                              WETH = weth;
                              STAKING = staking;
                          }
                          /// @dev Deploy (if needed) a `FeeCollector` contract for `poolId`
                          ///      and wrap its ETH into WETH. Anyone may call this.
                          /// @param poolId The pool ID associated with the staking pool.
                          /// @return feeCollector The `FeeCollector` contract instance.
                          function prepareFeeCollectorToPayFees(bytes32 poolId)
                              external
                              returns (FeeCollector feeCollector)
                          {
                              feeCollector = getFeeCollector(poolId);
                              uint256 codeSize;
                              assembly {
                                  codeSize := extcodesize(feeCollector)
                              }
                              if (codeSize == 0) {
                                  // Create and initialize the contract if necessary.
                                  new FeeCollector{salt: bytes32(poolId)}();
                                  feeCollector.initialize(WETH, STAKING, poolId);
                              }
                              if (address(feeCollector).balance > 1) {
                                  feeCollector.convertToWeth(WETH);
                              }
                              return feeCollector;
                          }
                          /// @dev Get the `FeeCollector` contract for a given pool ID. The contract
                          ///      will not actually exist until `prepareFeeCollectorToPayFees()`
                          ///      has been called once.
                          /// @param poolId The pool ID associated with the staking pool.
                          /// @return feeCollector The `FeeCollector` contract instance.
                          function getFeeCollector(bytes32 poolId)
                              public
                              view
                              returns (FeeCollector feeCollector)
                          {
                              return FeeCollector(LibFeeCollector.getFeeCollectorAddress(
                                  address(this),
                                  FEE_COLLECTOR_INIT_CODE_HASH,
                                  poolId
                              ));
                          }
                      }
                      // SPDX-License-Identifier: Apache-2.0
                      /*
                        Copyright 2020 ZeroEx Intl.
                        Licensed under the Apache License, Version 2.0 (the "License");
                        you may not use this file except in compliance with the License.
                        You may obtain a copy of the License at
                          http://www.apache.org/licenses/LICENSE-2.0
                        Unless required by applicable law or agreed to in writing, software
                        distributed under the License is distributed on an "AS IS" BASIS,
                        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                        See the License for the specific language governing permissions and
                        limitations under the License.
                      */
                      pragma solidity ^0.6.5;
                      pragma experimental ABIEncoderV2;
                      /// @dev Helpers for computing `FeeCollector` contract addresses.
                      library LibFeeCollector {
                          /// @dev Compute the CREATE2 address for a fee collector.
                          /// @param controller The address of the `FeeCollectorController` contract.
                          /// @param initCodeHash The init code hash of the `FeeCollector` contract.
                          /// @param poolId The fee collector's pool ID.
                          function getFeeCollectorAddress(address controller, bytes32 initCodeHash, bytes32 poolId)
                              internal
                              pure
                              returns (address payable feeCollectorAddress)
                          {
                              // Compute the CREATE2 address for the fee collector.
                              return address(uint256(keccak256(abi.encodePacked(
                                  byte(0xff),
                                  controller,
                                  poolId, // pool ID is salt
                                  initCodeHash
                              ))));
                          }
                      }