Solidity Mapping use string to find struct? - solidity

Question

I want to use the mapping find the struct but the mapping just can use the bytes and I need to use the string.
pragma solidity >=0.4.22 <0.6.0;
pragma experimental ABIEncoderV2;
contract land{
address public owner;
constructor() public{
owner = msg.sender;
}
struct Landpaper{
string number;
string landaddress;
string landnumber;
string landpurpose;
uint landgrades;
uint256 landarea;
string holdpoints;
}
mapping(bytes8 => Landpaper) public lp;
modifier Permission(){
require(msg.sender == owner);
_;
}
function set(string memory rfidnumber, Landpaper memory _landpaperRecord) public Permission{
lp[rfidnumber]=_landpaperRecord;
}
function get(string memory rfidnumber) view public returns(Landpaper memory){
return lp[rfidnumber];
}
}
because I have to read the rfid UID and I will translate the UID to string, so I need to use the string set my data. I use the bytes8 and I input string type, I need to change my string to bytes8, plz told me how to do.

Answer 1

You can write a function to convert string to bytes8
function stringToBytes8(string memory sourceStr) private pure returns(bytes8) {
bytes8 temp = 0x0;
assembly {
temp := mload(add(sourceStr, 32))
}
return temp;
}
And call it from set and get functions
function set(string memory rfidnumber, Landpaper memory _landpaperRecord) public Permission {
bytes8 rfidb8 = stringToByte8(rfidnumber);
lp[rfidb8]=_landpaperRecord;
}
function get(string memory rfidnumber) public view returns(Landpaper memory) {
bytes8 rfidb8 = stringToByte8(rfidnumber);
return lp[rfidb8];
}
Though I would suggest to avoid performing conversion process in contract as it would consume unnecessary gas. Instead perform the conversion on client side and pass bytes8 as parameter
function set(bytes8 rfidnumber, Landpaper memory _landpaperRecord) public Permission {
lp[rfidnumber]=_landpaperRecord;
}
function get(bytes8 rfidnumber) public view returns(Landpaper memory) {
return lp[rfidnumber];
}