function _verifySig(
    ForwardRequest memory req,
    bytes32 domainSeparator,
    bytes32 requestTypeHash,
    bytes memory suffixData,
    bytes memory sig
) internal view {
    require(typeHashes[requestTypeHash], "NGEUR Forwarder: invalid request typehash");
    bytes32 digest = keccak256(
        abi.encodePacked("\x19\x01", domainSeparator, keccak256(_getEncoded(req, requestTypeHash, suffixData)))
    );
    require(digest.recover(sig) == req.from, "NGEUR Forwarder: signature mismatch");
}
function _getEncoded(
    ForwardRequest memory req,
    bytes32 requestTypeHash,
    bytes memory suffixData
) public pure returns (bytes memory) {
    return abi.encodePacked(
        requestTypeHash,
        abi.encode(req.from, req.to, req.value, req.gas, req.nonce, keccak256(req.data)),
        suffixData
    );
}
function execute(
    ForwardRequest calldata req,
    bytes32 domainSeparator,
    bytes32 requestTypeHash,
    bytes calldata suffixData,
    bytes calldata sig
) external payable returns (bool success, bytes memory ret) { 
    _verifyNonce(req);
    _verifySig(req, domainSeparator, requestTypeHash, suffixData, sig);
    _updateNonce(req);

    require(req.to == _eurfAddress, "NGEUR Forwarder: can only forward NGEUR transactions");

    bytes4 transferSelector = bytes4(keccak256("transfer(address,uint256)"));
    bytes4 reqTransferSelector = bytes4(req.data[:4]);

    require(reqTransferSelector == transferSelector, "NGEUR Forwarder: can only forward transfer transactions");

    (success, ret) = req.to.call{gas: req.gas, value: req.value}(abi.encodePacked(req.data, req.from));
    require(success, "NGEUR Forwarder: failed tx execution");

    _eurf.payGaslessBasefee(req.from, _msgSender());

    return (success, ret);
}
