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);
begin
  Dest := PByte( NativeUInt(Dest) + Size - 1);
  while (Size > 0) do 
  begin
    PByte(Dest)^ := PByte(Source)^;
    Inc(PByte(Source));
    Dec(PByte(Dest));
    Dec(Size);
  end;
end;