library GsnUtils {
    /**
     * extract error string from revert bytes
     */
    function getError(bytes memory err) internal pure returns (string memory ret) {
        if (err.length < 4 + 32) {
            //not a valid revert with error. return as-is.
            return string(err);
        }
        (ret) = abi.decode(LibBytesV06.slice(err, 4, err.length), (string));
    }

    /**
     * extract method sig from encoded function call
     */
    function getMethodSig(bytes memory msgData) internal pure returns (bytes4) {
        return LibBytesV06.readBytes4(msgData, 0);
    }

    /**
     * extract parameter from encoded-function block.
     * see: https://solidity.readthedocs.io/en/develop/abi-spec.html#formal-specification-of-the-encoding
     * note that the type of the parameter must be static.
     * the return value should be casted to the right type.
     */
    function getParam(bytes memory msgData, uint index) internal pure returns (uint) {
        return LibBytesV06.readUint256(msgData, 4 + index * 32);
    }
}
function getMethodSig(bytes memory msgData) internal pure returns (bytes4) {
    return LibBytesV06.readBytes4(msgData, 0);
}

/**
 * extract method sig from encoded function call
 */