openzeppelin-contracts/contracts/metatx/ERC2771Context.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/*
 * @dev Context variant with ERC2771 support.
 */
abstract contract ERC2771Context is Context {
    address immutable _trustedForwarder;

    constructor(address trustedForwarder) {
        _trustedForwarder = trustedForwarder;
    }

    function isTrustedForwarder(address forwarder) public view virtual returns(bool) {
        return forwarder == _trustedForwarder;
    }

    function _msgSender() internal view virtual override returns (address sender) {
        if (isTrustedForwarder(msg.sender)) {
            // The assembly code is more direct than the Solidity version using `abi.decode`.
            assembly { sender := shr(96, calldataload(sub(calldatasize(), 20))) }
        } else {
            return super._msgSender();
        }
    }

    function _msgData() internal view virtual override returns (bytes calldata) {
        if (isTrustedForwarder(msg.sender)) {
            return msg.data[:msg.data.length-20];
        } else {
            return super._msgData();
        }
    }
}