library LibPermit {
    struct Permit {
        address spender; // Spender
        uint256 value; // Value
        uint256 nonce; // Nonce
        uint256 expiry; // Expiry
    }

    // Hash for the EIP712 LibPermit Schema
    //    bytes32 constant internal EIP712_PERMIT_SCHEMA_HASH = keccak256(abi.encodePacked(
    //        "Permit(",
    //        "address spender,",
    //        "uint256 value,",
    //        "uint256 nonce,",
    //        "uint256 expiry",
    //        ")"
    //    ));
    bytes32 internal constant EIP712_PERMIT_SCHEMA_HASH =
        0x58e19c95adc541dea238d3211d11e11e7def7d0c7fda4e10e0c45eb224ef2fb7;

    /// @dev Calculates Keccak-256 hash of the permit.
    /// @param permit The permit structure.
    /// @return permitHash Keccak-256 EIP712 hash of the permit.
    function getPermitHash(Permit memory permit, bytes32 eip712ExchangeDomainHash)
        internal
        pure
        returns (bytes32 permitHash)
    {
        permitHash = LibEIP712.hashEIP712Message(eip712ExchangeDomainHash, hashPermit(permit));
        return permitHash;
    }

    /// @dev Calculates EIP712 hash of the permit.
    /// @param permit The permit structure.
    /// @return result EIP712 hash of the permit.
    function hashPermit(Permit memory permit) internal pure returns (bytes32 result) {
        // Assembly for more efficiently computing:
        bytes32 schemaHash = EIP712_PERMIT_SCHEMA_HASH;

        assembly {
            // Assert permit offset (this is an internal error that should never be triggered)
            if lt(permit, 32) {
                invalid()
            }

            // Calculate memory addresses that will be swapped out before hashing
            let pos1 := sub(permit, 32)

            // Backup
            let temp1 := mload(pos1)

            // Hash in place
            mstore(pos1, schemaHash)
            result := keccak256(pos1, 160)

            // Restore
            mstore(pos1, temp1)
        }
        return result;
    }
}
function getPermitHash(Permit memory permit, bytes32 eip712ExchangeDomainHash)
        internal
        pure
        returns (bytes32 permitHash)
    {
        permitHash = LibEIP712.hashEIP712Message(eip712ExchangeDomainHash, hashPermit(permit));
        return permitHash;
    }
/// @dev Calculates Keccak-256 hash of the permit.
/// @param permit The permit structure.
/// @return permitHash Keccak-256 EIP712 hash of the permit.