Developers

Omnichain Smart Contracts

Examples

Smart contract helpers

In this tutorial we use several helpers to common tasks. Here you can find a link to those helpers:

Swap Helper Lib

SwapHelperLib.sol

library SwapHelperLib {
    uint16 internal constant MAX_DEADLINE = 200;
    //...
    error WrongGasContract();
    error NotEnoughToPayGasFee();
    error CantBeIdenticalAddresses();
    error CantBeZeroAddress();
    //...
    // returns sorted token addresses, used to handle return values from pairs sorted in this order
    function sortTokens(address tokenA, address tokenB) internal pure returns (address token0, address token1) {
        if (tokenA == tokenB) revert CantBeIdenticalAddresses();
        (token0, token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
        if (token0 == address(0)) revert CantBeZeroAddress();
    }
    //...
    // calculates the CREATE2 address for a pair without making any external calls
    function uniswapv2PairFor(address factory, address tokenA, address tokenB) public pure returns (address pair) {
        (address token0, address token1) = sortTokens(tokenA, tokenB);
        pair = address(
            uint160(
                uint256(
                    keccak256(
                        abi.encodePacked(
                            hex"ff",
                            factory,
                            keccak256(abi.encodePacked(token0, token1)),
                            hex"96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f" // init code hash
                        )
                    )
                )
            )
        );
    }
    //...
    function _doWithdrawal(address targetZRC20, uint256 amount, bytes32 receipient) internal {
        (address gasZRC20, uint256 gasFee) = IZRC20(targetZRC20).withdrawGasFee();
        if (gasZRC20 != targetZRC20) revert WrongGasContract();
        if (gasFee >= amount) revert NotEnoughToPayGasFee();
        IZRC20(targetZRC20).approve(targetZRC20, gasFee);
        IZRC20(targetZRC20).withdraw(abi.encodePacked(receipient), amount - gasFee);
    }
    //...
    function _existsPairPool(address uniswapV2Factory, address zrc20A, address zrc20B) internal view returns (bool) {
        address uniswapPool = uniswapv2PairFor(uniswapV2Factory, zrc20A, zrc20B);
        return IZRC20(zrc20A).balanceOf(uniswapPool) > 0 && IZRC20(zrc20B).balanceOf(uniswapPool) > 0;
    }
    //...
    function _doSwap(
        address zetaToken,
        address uniswapV2Factory,
        address uniswapV2Router,
        address zrc20,
        uint256 amount,
        address targetZRC20,
        uint256 minAmountOut
    ) internal returns (uint256) {
        bool existsPairPool = _existsPairPool(uniswapV2Factory, zrc20, targetZRC20);
        address[] memory path;
        if (existsPairPool) {
            path = new address[](2);
            path[0] = zrc20;
            path[1] = targetZRC20;
        } else {
            path = new address[](3);
            path[0] = zrc20;
            path[1] = zetaToken;
            path[2] = targetZRC20;
        }
        IZRC20(zrc20).approve(address(uniswapV2Router), amount);
        uint256[] memory amounts = IUniswapV2Router01(uniswapV2Router).swapExactTokensForTokens(
            amount,
            minAmountOut,
            path,
            address(this),
            block.timestamp + MAX_DEADLINE
        );
        return amounts[path.length - 1];
    }
}

Bytes Helper Lib

BytesHelperLib.sol

library BytesHelperLib {
    function bytesToAddress(bytes calldata data, uint256 offset) internal pure returns (address output) {
        bytes memory b = data[offset:offset + 20];
        assembly {
            output := mload(add(b, 20))
        }
    }
    //...
    function bytesToUint32(bytes calldata data, uint256 offset) internal pure returns (uint32 output) {
        bytes memory b = data[offset:offset + 4];
        assembly {
            output := mload(add(b, 4))
        }
    }
    //...
    function addressToBytes(address someAddress) internal pure returns (bytes32) {
        return bytes32(uint256(uint160(someAddress)));
    }
}