WASAPI_Notification_Interfaces/IAudioSessionNotification.c

#include "IAudioSessionNotification.h"

 HRESULT InitializeAudioSessionNotification(IAudioSessionNotification** this, IAudioSessionControl *** pppAudioSessionControlInterfaces, int* pNumberSessionControls)
{
	// Initializes the IAudioSessionNotification struct, this involves creating it, allocating memory, setting initial vaules and assigning the functions to be used
	//Allocate memory for the vtable
	IAudioSessionNotificationVtbl* pvtbl = malloc(sizeof(IAudioSessionNotificationVtbl));

	if (!pvtbl)
	{
		// If the vtable memory cannot be assigned
		return E_OUTOFMEMORY;
	}

	// Asign all the functions
	pvtbl->AddRef = (*IAudioSessionNotificationAddRef);
	pvtbl->OnSessionCreated = (*IAudioSessionNotificationOnSessionCreated);
	pvtbl->QueryInterface = (*IAudioSessionNotificationQueryInterface);
	pvtbl->Release = (*IAudioSessionNotificationRelease);

	//Assign memory for the notifications struct. Cast the pointer returned from malloc to the correct type
	myIAudioSessionNotification * AudioSessionNotification;
	AudioSessionNotification = (myIAudioSessionNotification*) malloc(sizeof(myIAudioSessionNotification));
	if (!AudioSessionNotification)
	{
		// If the struct memory cannot be assigned free the memory previously assigned to the vtable and return
		free(pvtbl);

		return E_OUTOFMEMORY;
	}
	
	// Add the virtual table to the strut
	AudioSessionNotification->lpVtbl = pvtbl;
	AudioSessionNotification->cRef = 0;
	// pppAudioSessionControlInterfaces is a pointer to an array of control interface pointers
	AudioSessionNotification->pppAudioSessionControlInterfaces = pppAudioSessionControlInterfaces;
	AudioSessionNotification->pNumberAudioSessionControls = pNumberSessionControls;

	// Update the pointer address passed into the function
	*this = (IAudioSessionNotification*) AudioSessionNotification;

	return S_OK;
}

 HRESULT STDMETHODCALLTYPE IAudioSessionNotificationQueryInterface(IAudioSessionNotification* this, REFIID riid, void** ppvoid) 
 {
	 //printf("\nQuery interface audio session notification\n");
	 // Validate the object pointer.
	 if (!this) 
	 {
		 return E_INVALIDARG;
	 }

	 // Validate other parameters.
	 if (!ppvoid)
	 {
		 return E_INVALIDARG;
	 }

	 // Set the output pointer to NULL.
	 *ppvoid = NULL;
	 // Check the interface identifier. memcmp() returns 0 if they are equal.
	 if (memcmp(riid, &IID_IUnknown, sizeof(IID)) && memcmp(riid, &IID_IAudioSessionNotification, sizeof(IID))) 
	 {
		 return E_NOINTERFACE;
	 }

	 // The interface is supported. Increment the reference count and return.
	 this->lpVtbl->AddRef(this);
	 *ppvoid = this;

	 return S_OK;
 }

ULONG STDMETHODCALLTYPE IAudioSessionNotificationRelease(IAudioSessionNotification* this)
{
	// Cast the standard interface to my interface to allow access to cRef
	myIAudioSessionNotification* castInterface = (myIAudioSessionNotification*) this;

	ULONG cRef = InterlockedDecrement(&castInterface->cRef);
	
	if (cRef == 0)
	{
		free(castInterface->lpVtbl);
		free(castInterface);
		//printf("\nAudio session notification memory freed");
	}

	//printf("\nNotification release, ref count : %ld\n", cRef);
	return cRef;
}

ULONG STDMETHODCALLTYPE IAudioSessionNotificationAddRef(IAudioSessionNotification* this)
{
	// Cast the standard interface to my interface to allow access to cRef
	myIAudioSessionNotification* castInterface = (myIAudioSessionNotification*)this;
	return InterlockedIncrement(&castInterface->cRef);
}

HRESULT IAudioSessionNotificationOnSessionCreated(IAudioSessionNotification* this, IAudioSessionControl* pNewSessionControl)
{
	printf("\nNew session created");

	// First thing is to add a ref to the control interface so it isn't released by the system
	pNewSessionControl->lpVtbl->AddRef(pNewSessionControl);

	// Add the new session to the array of IAudioSessionControl interfaces
	// A pointer to pointer to the array is stored in the interface, along with a pointer to the number of current interfaces
	// Cast IAudioSessionNotification to my implementation to access those variables
	myIAudioSessionNotification* pCastInterface = (myIAudioSessionNotification*)this;
	// ppCurrentInterfacesAddress is a pointer to the array of interface pointers
	IAudioSessionControl ** ppCurrentInterfacesAddress = *(pCastInterface->pppAudioSessionControlInterfaces);
	// The number of currently stored IAudioSessionControl interfaces
	int numberOfInterfaces = *pCastInterface->pNumberAudioSessionControls;

	// This is a pointer to the first element of the array of pointers to session control objects
	IAudioSessionControl** pNewArray = NULL;

	// Realloc memory for the new pointer
	if (numberOfInterfaces)
	{
		pNewArray = (IAudioSessionControl**)realloc(ppCurrentInterfacesAddress, sizeof(IAudioSessionControl*) * (numberOfInterfaces + 1));
	}

	if (!pNewArray)
	{
		// Realloc has failed, have to use malloc and memcpy
		pNewArray = (IAudioSessionControl **) malloc(sizeof(IAudioSessionControl*) * (numberOfInterfaces + 1));

		if (!pNewArray)
		{
			printf("\nNot able to allocate new memory for array of control interfaces.");
			return E_OUTOFMEMORY;
		}

		// Copy the contents of the array (pointers to control interfaces) to the new memory location
		memcpy(pNewArray, ppCurrentInterfacesAddress, sizeof(IAudioSessionControl*) * numberOfInterfaces);
	}

	// At this point the memory has been allocated through realloc or malloc and the last pointer needs to be added to the array at the final location
	*(pNewArray + numberOfInterfaces) = pNewSessionControl;

	// Send the pointer to the new array back up the chain so it is seen by the main program thread
	*(pCastInterface->pppAudioSessionControlInterfaces) = pNewArray;

	// Increment the number of interfaces and send it back up the chain ready for the next one.
	*(pCastInterface->pNumberAudioSessionControls) =  numberOfInterfaces + 1;

	// The new IAudioSessionControl interface should now have been appended to the array
	// Final step is to register the sesssion events
	IAudioSessionEvents AudioSessionEvents;
	//InitializeAudioSessionEvents(&AudioSessionEvents, pNewSessionControl, pSessionInformation->AudioSessionControlsCollection);
	
	return S_OK;
}