Delphi Reverse order of bytes

Question

I have been trying to write a function that takes two pointers (an input and an output) and writes the bytes from the input into the output in reverse order. So far I have

Answer 1

procedure ReverseBytes(Source, Dest: Pointer; Size: Integer);
var
  Index: Integer;
begin
  for Index := 0 to Size - 1 do
    Move(Pointer(LongInt(Source) + Index)^, 
        Pointer(LongInt(Dest) + (Size - Index - 1))^ , 1);
end;

procedure TForm2.Button2Click(Sender: TObject);
var
  s: AnsiString;
  P: Pointer;
begin
  s := #0'testreverse';
  GetMem(P, Length(s));
  ReverseBytes(Pointer(s), P, Length(s));

  ShowMessage(PAnsiChar(P));   // esrevertset
  FreeMem(P);
end;