Broken TBytes

[Der schöne Günther]

Just use the debugger to inspect your b: TBytes after you've done your b := Stream.Bytes; .

It already contains more bytes than your original file. Since the Bytes property just reads out an ordinary field, something must have gone wrong in LoadFromFile .

The root cause is the protected method Realloc of TMemoryStream , the parent of your TBytesStream . It makes sure the internal byte array is always aligned to a multiple of 8KB.

This way, the Byte property is garbage, you will have to truncate it afterwards, just as Klaus already said:

Delphi-Quellcode:

procedure WhyIsItNotWorking();
const
   path = 'x:\cake.pdf';
var
   Stream : TBytesStream;
   b : TBytes ;
begin
   Stream := TBytesStream.Create();
   Stream.LoadFromFile(path);

   b := Stream.Bytes;
   SetLength(b, Stream.Size); // This is new

   Stream := TBytesStream.Create(b);
   Stream.SaveToFile( path.Replace('cake', 'cake2') );

   FreeAndNil(Stream); // You know that you did not destroy the first TStream instance?
end;

I would have made the same mistake. I don't think this was to be expected.