>I'm using delphi functions in my dll, which is dynamically loaded into someone else's host program. The C++ SDK for the host has been translated to Delphi by someone else. The host calls getChunk() and setChunk() at particular times, and I must supply or receive an amount of data, respectively. The data is meaningful to me but an opaque chunk to the host.
>
>These are the functions:
>
>

//C++
>virtual long getChunk (void** data, bool isPreset = false) { return 0; }
>virtual long setChunk (void* data, long byteSize, bool isPreset = false) { return 0; }
>
>//Delphi
>function getChunk(var data: pointer; isPreset: Boolean): longint; virtual;
>function setChunk(data: pointer; byteSize: longint; isPreset: Boolean): longint; virtual;

>
>I'm noting that data in getChunk is a pointer to a pointer, so has been declared in Delphi as a variable parameter so it is passed by reference. I thought this meant that I didn't need to allocate a variable of type ^pointer and fill it with @programs and set data to it's address. But I'm not sure. Anyway, this (edited down) is what I have tried to write. But I'm finding that the messagebox in setChunk() is displaying 'cleared', where it should be displaying 'saved'. Now I'm wondering if I should be allocating memory outside these functions and filling the memory and passing pointers to that inside the functions.
>
>Where am I going wrong, please?
>
>

//Interface
>
>type
>
> kNumPrograms  = 16;
>
> APluginProgram=class
> private
>    fpar: Tfpar;
>    name: array[0..50] of char;
>    expression: array[0..254] of char;
>    ...
>
> Tprograms = array[0..kNumPrograms-1] of APluginProgram;
>
> APlugin=class(AudioEffectX)
> public
>   function getChunk(var data: pointer; isPreset: Boolean): longint; override;
>   function setChunk(data: pointer; byteSize: longint; isPreset: Boolean): longint; override;
>   ...
>
>
>//Implementation
>...
>
>function APlugin.getChunk(var data: pointer; isPreset: Boolean): longint;
>begin
> inherited getChunk(data, isPreset);
> programs[curprogram].expression := 'saved';
> data := @programs;
> Result := SizeOf(programs);
>end;
>
>function APlugin.setChunk(data: pointer; byteSize: longint; isPreset: Boolean): longint;
>begin
> inherited setChunk(data, byteSize, isPreset);
> if byteSize <> SizeOf(programs) then begin Result := 1; exit; end;
> programs[curprogram].expression := 'cleared';
> programs := Tprograms(data^);
> MessageBox(0, PChar('programs[curprogram].expression = '
>   + programs[curprogram].expression), Nil, MB_OK);
> Result := 1;
>end;

Well actually poitner to pointer declaration in C is pointer to interface. However you cannot instantiate interface directly, so pointer to pointer is reference (pointer) to typecasted instance of a class that supports the specified interface.
Hope it makes sense to you.