CurrencyLibrary.sol

// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity ^0.8.19;

import {IERC20Minimal} from "../interfaces/external/IERC20Minimal.sol";

type Currency is address;

/// @title CurrencyLibrary
/// @dev This library allows for transferring and holding native tokens and ERC20 tokens
library CurrencyLibrary {
    using CurrencyLibrary for Currency;

    /// @notice Thrown when a native transfer fails
    error NativeTransferFailed();

    /// @notice Thrown when an ERC20 transfer fails
    error ERC20TransferFailed();

    Currency public constant NATIVE = Currency.wrap(address(0));

    function transfer(Currency currency, address to, uint256 amount) internal {
        // implementation from
        // https://github.com/transmissions11/solmate/blob/3c738133a0c1697096d63d28ef7a8ef298f9af6b/src/utils/SafeTransferLib.sol

        bool success;
        if (currency.isNative()) {
            assembly {
                // Transfer the ETH and store if it succeeded or not.
                success := call(gas(), to, amount, 0, 0, 0, 0)
            }

            if (!success) revert NativeTransferFailed();
        } else {
            assembly {
                // Get a pointer to some free memory.
                let freeMemoryPointer := mload(0x40)

                // Write the abi-encoded calldata into memory, beginning with the function selector.
                mstore(freeMemoryPointer, 0xa9059cbb00000000000000000000000000000000000000000000000000000000)
                mstore(add(freeMemoryPointer, 4), to) // Append the "to" argument.
                mstore(add(freeMemoryPointer, 36), amount) // Append the "amount" argument.

                success :=
                    and(
                        // Set success to whether the call reverted, if not we check it either
                        // returned exactly 1 (can't just be non-zero data), or had no return data.
                        or(and(eq(mload(0), 1), gt(returndatasize(), 31)), iszero(returndatasize())),
                        // We use 68 because the length of our calldata totals up like so: 4 + 32 * 2.
                        // We use 0 and 32 to copy up to 32 bytes of return data into the scratch space.
                        // Counterintuitively, this call must be positioned second to the or() call in the
                        // surrounding and() call or else returndatasize() will be zero during the computation.
                        call(gas(), currency, 0, freeMemoryPointer, 68, 0, 32)
                    )
            }

            if (!success) revert ERC20TransferFailed();
        }
    }

    function balanceOfSelf(Currency currency) internal view returns (uint256) {
        if (currency.isNative()) {
            return address(this).balance;
        } else {
            return IERC20Minimal(Currency.unwrap(currency)).balanceOf(address(this));
        }
    }

    function equals(Currency currency, Currency other) internal pure returns (bool) {
        return Currency.unwrap(currency) == Currency.unwrap(other);
    }

    function isNative(Currency currency) internal pure returns (bool) {
        return Currency.unwrap(currency) == Currency.unwrap(NATIVE);
    }

    function toId(Currency currency) internal pure returns (uint256) {
        return uint160(Currency.unwrap(currency));
    }

    function fromId(uint256 id) internal pure returns (Currency) {
        return Currency.wrap(address(uint160(id)));
    }
}