procedure FastSetString(var s: RawUTF8; p: pointer; len: PtrInt);
var r: PAnsiChar;
    sr: PStrRec;
begin
  if len<=0 then
    r := nil else begin
    GetMem(r,len+(STRRECSIZE+4));
    sr := pointer(r);
    sr^.codePage := CP_UTF8;
    sr^.elemSize := 1;
    sr^.refCnt := 1;
    sr^.length := len;
    inc(PByte(sr),STRRECSIZE);
    PCardinal(PAnsiChar(sr)+len)^ := 0; // ensure ends with four #0
    r := pointer(sr);
    if p<>nil then
      {$ifdef FPC}Move{$else}MoveFast{$endif}(p^,sr^,len);
  end;
  {$ifdef FPC}Finalize(s){$else}s := ''{$endif};
  pointer(s) := r;
end;