Question

Is it possible to pass a Delphi stream (TStream descendant) to a DLL written in c/c++? DLL will be written in Microsoft c/c++. If that is not possible, how about if we use C++ Builder to create the DLL? Alternatively, are there any Stream (FIFO) classes which can be shared between Microsoft C/C++ and Delphi?

Thanks!

Answer 1

You can do this using IStream and TStreamAdapter. Here’s a quick example (tested in D2007 and XE2):

uses
  ActiveX;

procedure TForm1.DoSomething;
var
  MemStream: TMemoryStream;
  ExchangeStream: IStream;
begin
  MemStream := TMemoryFile.Create;
  try
    MemStream.LoadFromFile('C:\Test\SomeFile.txt');
    MemStream.Position := 0;
    ExchangeStream := TStreamAdapter.Create(MemStream) as IStream;
    // Pass ExchangeStream to C++ DLL here, and do whatever else
  finally
    MemStream.Free;
  end;
end;

Just in case, if you need to go the other way (receiving an IStream from C/C++), you can use TOleStream to get from that IStream to a Delphi TStream.