function Hex2Int64(st:string):int64;
var
   i,ln:word;
begin
   st := LowerCase(st);
   Result := 0;
   ln := Length(st);
   if ln > 0 then
    for i := 1 to ln do
     case st[i] of
      '0'..'9': Result := Result shl 4 + ord(st[i]) - 48;
      'a'..'f': Result := Result shl 4 + ord(st[i]) - 87;
      else break;
     end;
end;