Loading an Object from a Resource

Objects stored as resources or at some other location in memory are loaded in much the same way as file objects. See Loading an Object from a File.

With memory objects, however, the wszName, guidObject, and wszFileName members of the DMUS_OBJECTDESC structure are irrelevant. Instead, you must obtain a pointer to the block of memory occupied by the object, and its size, and put these in the pbMemData and llMemLength members respectively. You must also set the DMUS_OBJ_MEMORY flag in the dwFlags member.

The memory cannot be released once IDirectMusicLoader8::GetObject has been called, because the loader keeps an internal pointer to the memory to facilitate caching data. If you want to clear it out, call IDirectMusicLoader8::SetObject with the same DMUS_OBJECTDESC descriptor, but with NULL in pbMemData. This is not an issue when loading from a resource, because resource memory is not freed.

The following function, where g_pLoader is a valid IDirectMusicLoader8 pointer, loads a MIDI file from a resource into a segment:

IDirectMusicSegment8* g_pSegment; 
 
HRESULT LoadMidi(HMODULE hMod, WORD ResourceID)
{
  HRESULT      hr;
  DMUS_OBJECTDESC  ObjDesc;
 
  HRSRC hFound = FindResource(hMod, 
    MAKEINTRESOURCE(ResourceID), RT_RCDATA);
  HGLOBAL hRes = LoadResource(hMod, hFound);
 
  ObjDesc.dwSize = sizeof(DMUS_OBJECTDESC);
  ObjDesc.guidClass = CLSID_DirectMusicSegment;
  ObjDesc.dwValidData = DMUS_OBJ_CLASS | DMUS_OBJ_MEMORY;
  ObjDesc.pbMemData = (BYTE *) LockResource(hRes);
  ObjDesc.llMemLength = SizeofResource(hMod, hFound);
 
  hr = g_pLoader->GetObject(
    &ObjDesc, IID_IDirectMusicSegment8, 
    (void**) &g_pSegment );
 
  return hr;
}

Objects referenced by other objects must be loaded first. For example, if you load a segment that contains a reference to a style, the style must already be loaded in order for the segment to play correctly. Alternatively, you can call IDirectMusicLoader8::SetObject on the style so that the segment can find it.