solidity 字符串合并，长度

pragma solidity ^0.8.0;

contract My {

    event log(uint256 a);

    event log(string a);

    string name = unicode"小米";

    string name_b = "bbbb";

    function forTest(uint256 b) public returns (uint256) {

        require(b == 100);

        uint256 a = 0;

        emit log(a);

        for (uint256 x = 1; x <= b; x++) {

            a = a + x;

        }

        emit log(a);

        return a;

    }

    function StrTest() public view returns (string memory,uint256) {

        return (string(abi.encodePacked(name, "+", name_b)), bytes(name_b).length);

    }

}