WASAPI_Notification_Interfaces/AudioSessions_framework.c

#include "AudioSesssions_framework.h"

static inline HRESULT getDefaultAudioEndpoint(AudioSessionsInformation*);
static inline HRESULT refreshIMMEnumerator(AudioSessionsInformation*);
static HRESULT releaseControlInterfaces(AudioSessionsInformation*);

/*
 * \brief Initilises Co in multithreaded and gets IMM devices & default device interfaces.
 */
HRESULT initialiseSessionsFramework(AudioSessionsInformation * pSessionInformation)
{
	CoInitializeEx(NULL, COINIT_MULTITHREADED);

	// Gets a new enumerator of all the multimedia devices
	refreshIMMEnumerator(pSessionInformation);
	// Gets the device interface for the default audio endpoint
	getDefaultAudioEndpoint(pSessionInformation);
	
	InitializeAudioSessionNotification(&pSessionInformation->AudioSessionNotification,
		&pSessionInformation->AudioSessionControlsCollection,
		&pSessionInformation->NumberAudioSessionsActive);

	refreshOpenSessions(pSessionInformation);

	
	return S_OK;
}

HRESULT refreshOpenSessions(AudioSessionsInformation* pSessionInformation)
{
	// Throw an error if the IMMDevice pointer has not been initialised
	if (!pSessionInformation->IMMDevice) return CO_E_NOTINITIALIZED;

	// Get a session manager 2 interface and use it to get a session enumerator
	IAudioSessionManager2* myAudioSessionManager2 = NULL;
	pSessionInformation->IMMDevice->lpVtbl->Activate(pSessionInformation->IMMDevice,
													&IID_IAudioSessionManager2, 
													CLSCTX_ALL, 
													NULL, 
													&myAudioSessionManager2);
	IAudioSessionEnumerator* myAudioSessionEnumerator;
	myAudioSessionManager2->lpVtbl->GetSessionEnumerator(myAudioSessionManager2, 
															&myAudioSessionEnumerator);

	// Then release the notifications interface
	pSessionInformation->AudioSessionNotification->lpVtbl->Release(pSessionInformation->AudioSessionNotification);
	// And register a new one, I think this may be necessary if the endpoint has changed
	myAudioSessionManager2->lpVtbl->RegisterSessionNotification(myAudioSessionManager2, pSessionInformation->AudioSessionNotification);

	// Once we have the number of open sessions memory can be allocated for the control interfaces
	// First; release any control interfaces left over and free the memory
	releaseControlInterfaces(pSessionInformation);

	// Then get the number of sessions active and save it in the session information stuct
	myAudioSessionEnumerator->lpVtbl->GetCount(myAudioSessionEnumerator, 
												&pSessionInformation->NumberAudioSessionsActive);
	// Allocate memory
	pSessionInformation->AudioSessionControlsCollection = malloc(sizeof(IAudioSessionControl) * pSessionInformation->NumberAudioSessionsActive);

	// Print to console if the memory cannot be allocated
	if (!pSessionInformation->AudioSessionControlsCollection) printf("\nMemory allocation error.");

	// Put all the sessions into the array along with an index for each, also register the events
	for (int i = 0; i < pSessionInformation->NumberAudioSessionsActive; i++)
	{
		//TODO: This should really be a simple audio interface rather then an audio session control interface
		IAudioSessionControl* sessionControl;
		// Get the session control interface from the enumerator
		myAudioSessionEnumerator->lpVtbl->GetSession(myAudioSessionEnumerator, i, &sessionControl);
		pSessionInformation->AudioSessionControlsCollection[i] = sessionControl;
		// Register the events interface for the session
		// This is complicated slightly because I want to be able to identify the disconnected session in the disconnection handler
		// This requires putting the address of the control interface into the events interface
		// The problem with this is that there is an events interface created for each control session
		// Although they all share a virtual table
		myIAudioSessionEvents* AudioSessionEvents;
		// The virtual table will be created on the first call to this function and then used for all future calls
		// Also takes the address of the pointer to the array of control interface pointers
		// This address should be constant whereas the pointer to the array of interface pointers will change every time an interface is add/destroyed and new memory is allocated
		InitializeAudioSessionEvents(&AudioSessionEvents, sessionControl, pSessionInformation->AudioSessionControlsCollection);

		// Now the events interface has been setup, register it
		// This requires casting my session events interface to the interface expected by the api
		sessionControl->lpVtbl->RegisterAudioSessionNotification(sessionControl, AudioSessionEvents);
		AudioSessionState sessionState = 3;
		sessionControl->lpVtbl->GetState(sessionControl, &sessionState);
		printf("\nRegistered session %d with control iterface at %p and events interface at %p", i, sessionControl, &AudioSessionEvents);
		printf("with state ");
		switch (sessionState)
		{
		case(2):
			printf("Expired");
			break;
		case(1):
			printf("Active");
			break;
		case(0):
			printf("Inactive");
			break;
		default:
			printf("Unknown");
			break;
		}
	}

	// Release the session manager and enumerator
	myAudioSessionManager2->lpVtbl->Release(myAudioSessionManager2);
	myAudioSessionEnumerator->lpVtbl->Release(myAudioSessionEnumerator);

	return S_OK;
}

// Releases the audio control interfaces in the session information structure.
// Also releases the memory allocated to the array of pointers to the control interfaces
HRESULT releaseControlInterfaces(AudioSessionsInformation * pSessionInformation)
{
	// Goes through and releases all the control interfaces left over.
	for (int i = 0; i < pSessionInformation->NumberAudioSessionsActive; i++)
	{
		//ControlInterfaces[i]->lpVtbl->Release(ControlInterfaces[i]);
		IAudioSessionControl* nextInterface = (pSessionInformation->AudioSessionControlsCollection[i]);
		nextInterface->lpVtbl->Release(nextInterface);
	}

	if (!pSessionInformation->AudioSessionControlsCollection) free(pSessionInformation->AudioSessionControlsCollection);

	return S_OK;
}

// Updates the IMM Device default audio endpoint in the session information structure
HRESULT getDefaultAudioEndpoint(AudioSessionsInformation* pSessionInformation)
{
	return pSessionInformation->IMMEnumerator->lpVtbl->GetDefaultAudioEndpoint(pSessionInformation->IMMEnumerator,
																				eRender,
																				eMultimedia,
																				&(pSessionInformation->IMMDevice));
}

// Refreshes the list of IMM devices
HRESULT refreshIMMEnumerator(AudioSessionsInformation* pSessionInformation)
{
	return CoCreateInstance(&CLSID_MMDeviceEnumerator, NULL, CLSCTX_ALL, &IID_IMMDeviceEnumerator, &(pSessionInformation->IMMEnumerator));
	
}