[fpc-devel] Read from memory stream with position before start of file

[Paul Ishenin]

Michael Van Canneyt wrote:
>> If you do an exception or silent change of position it can cause
>> incompatibilities. Maybe read operation must be fixed to ignore positions out
>> of the range 0..Size -1?
>>     
>
> What does Delphi do in such a case ?
>   
Tested so:

procedure TForm1.Button1Click(Sender: TObject);
var
  S: TMemoryStream;
  B: Byte;
  Count: Integer;
begin
  S := TMemoryStream.Create;
  B := 1;
  S.Write(B, SizeOf(B));
  S.Position := -1;
  Count := S.Read(B, SizeOf(B));
  ShowMessage(IntToStr(Count));
  S.Free;
end;

Count = 0. IOW, delphi does not read if position < 0

Best regards,
Paul Ishenin.