Why do you need "buffer" having ".size". Cant you pack both variables
into class instance that do "anything" you want buffer to do?
You know Ruby FFI to extract data, Ruby Class to encapsulate it and
add
custom behavior.

On 20 Sie, 06:57, cfis <c...@savagexi.com> wrote:

> I'm trying to wrap FreeImage (http://freeimage.sourceforge.net/) and
> it has this function:
>
> DLL_API BOOL DLL_CALLCONV FreeImage_AcquireMemory(FIMEMORY *stream,
> BYTE **data, DWORD *size_in_bytes);
>
> The way this works is you hand FreeImage a pointer (data) which it
> then allocates memory for and returns the size in the size_in_bytes
> out parameter.  I've attached example C code from the FreeImage docs
> in case it helps.
>
> So I'm not sure how to wrap this function.  So far I have this:
>
> FreeImage.attach_function('FreeImage_AcquireMemory',
> [:pointer, :pointer, :uint], :bool)
>
> buffer = MemoryPointer.new(:pointer)
> size_ptr = MemoryPointer.new(:uint)
> FreeImage.FreeImage_AcquireMemory(self, buffer, size);
>
> What I would then like to do is something like:
>
> buffer.size = size_ptr.read_pointer()
>
> But buffer doesn't have any such API.
>
> Any help appreciated.
>
> Thanks,
>
> Charlie
> ------------
> void testAcquireMemIO(const char *lpszPathName) {
>   FIMEMORY *hmem = NULL;
>   // load a regular file
>   FREE_IMAGE_FORMAT fif = FreeImage_GetFileType(lpszPathName);
>   FIBITMAP *dib = FreeImage_Load(fif, lpszPathName, 0);
>
>   // open and allocate a memory stream
>   hmem = FreeImage_OpenMemory();
>
>   // save the image to a memory stream
>   FreeImage_SaveToMemory(FIF_PNG, dib, hmem, PNG_DEFAULT);
>   FreeImage_Unload(dib);
>
>   // get the buffer from the memory stream
>   BYTE *mem_buffer = NULL;
>   DWORD size_in_bytes = 0;
>   FreeImage_AcquireMemory(hmem, &mem_buffer, &size_in_bytes);
>
>   // save the buffer to a file stream
>   FILE *stream = fopen("buffer.png", "wb");
>   if(stream) {
>     fwrite(mem_buffer, sizeof(BYTE), size_in_bytes, stream);
>     fclose(stream);
>   }
>   // close and free the memory stream
>   FreeImage_CloseMemory(hmem);
>
>
>
>
>
>
>
> }