Searching a binary file for an hex pattern

Greetings,

One of the applications I'm currently trying to integrate with uses a thing called Btrieve, for which almost no support is left. I decided then to read the (if we may call it so) database BTR files into a memory stream and perform a manual search for what I need (there's an index-like structure inside and I have all the info I need to start with).

My approach is to read this binary file into a TMemoryStream (no problem here) and perform a search into it using StrPos. What happens is that if my search string has a #0, StrPos always returns nil... Any hints how to get this done ?!?! Should I search by chars or bytes ? Is this approach the best one ? Thank you for any help on this ! Using D7.

type
  TFormMain = class(TForm)
...
  private
      { Private declarations }
      Ms1, Ms2: TMemoryStream;
...
end;
...

const
  search_arg: const = #0#0#0#128#0#5;

procedure TFormMain.Ms1LoadFromFileClick(Sender: TObject);
begin
  try
    Ms1.LoadFromFile(my_file[0].name);
    HowToReturnOffsetFromStreamHere(Ms1, search_arg);  <---  ? ? ?
  except
    Showmessage('Couldn''t read the file !' + #13 + SysErrorMessage(GetLastError));
  end;
end;