AddressString.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

library StringToAddress {
    error InvalidAddressString();

    function toAddress(string memory addressString) internal pure returns (address) {
        bytes memory stringBytes = bytes(addressString);
        uint160 addressNumber = 0;
        uint8 stringByte;

        if (stringBytes.length != 42 || stringBytes[0] != '0' || stringBytes[1] != 'x') revert InvalidAddressString();

        for (uint256 i = 2; i < 42; ++i) {
            stringByte = uint8(stringBytes[i]);

            if ((stringByte >= 97) && (stringByte <= 102)) stringByte -= 87;
            else if ((stringByte >= 65) && (stringByte <= 70)) stringByte -= 55;
            else if ((stringByte >= 48) && (stringByte <= 57)) stringByte -= 48;
            else revert InvalidAddressString();

            addressNumber |= uint160(uint256(stringByte) << ((41 - i) << 2));
        }
        return address(addressNumber);
    }
}

library AddressToString {
    function toString(address addr) internal pure returns (string memory) {
        bytes memory addressBytes = abi.encodePacked(addr);
        uint256 length = addressBytes.length;
        bytes memory characters = '0123456789abcdef';
        bytes memory stringBytes = new bytes(2 + addressBytes.length * 2);

        stringBytes[0] = '0';
        stringBytes[1] = 'x';

        for (uint256 i; i < length; ++i) {
            stringBytes[2 + i * 2] = characters[uint8(addressBytes[i] >> 4)];
            stringBytes[3 + i * 2] = characters[uint8(addressBytes[i] & 0x0f)];
        }
        return string(stringBytes);
    }
}