Refactor : Better segregation and modularization of the audio backend functions

src/audio/mockingboard.c

@@ -1377,7 +1377,7 @@ static bool MB_DSInit()
 	unsigned long dwDSLockedBufferSize = 0;    // Size of the locked DirectSound buffer
 	int16_t* pDSLockedBuffer;
 
-	if(!soundcore_isAvailable)
+	if(!audio_isAvailable)
 		return false;
 
 	int hr = DSGetSoundBuffer(&MockingboardVoice, DSBCAPS_CTRLVOLUME, g_dwDSBufferSize, SAMPLE_RATE, 2);
@@ -1763,7 +1763,7 @@ static void ResetState()
 
 void MB_Reset()
 {
-	if(!soundcore_isAvailable)
+	if(!audio_isAvailable)
 		return;
 
 	for(int i=0; i<NUM_AY8910; i++)

src/audio/soundcore-openal.c

@@ -70,6 +70,8 @@ typedef struct ALVoices {
 
 static ALVoices *voices = NULL;
 
+static audio_backend_s openal_audio_backend = { 0 };
+
 static long OpenALCreateSoundBuffer(AudioParams_s *params, ALSoundBufferStruct **soundbuf_struct, void *extra_data);
 static long OpenALDestroySoundBuffer(ALSoundBufferStruct **soundbuf_struct);
 
@@ -151,7 +153,7 @@ static void PlaylistDequeue(ALVoice *voice, ALPlayBuf *node)
 
 // ----------------------------------------------------------------------------
 
-long SoundSystemCreate(const char *sound_device, SoundSystemStruct **sound_struct)
+static long openal_systemInit(const char *sound_device, SoundSystemStruct **sound_struct)
 {
     assert(*sound_struct == NULL);
     assert(voices == NULL);
@@ -197,9 +199,8 @@ long SoundSystemCreate(const char *sound_device, SoundSystemStruct **sound_struc
     return -1;
 }
 
-long SoundSystemDestroy(SoundSystemStruct **sound_struct)
+static long openal_systemShutdown(SoundSystemStruct **sound_struct)
 {
-    // ugly assumption : this sets the extern g_lpDS ...
     assert(*sound_struct != NULL);
 
     ALCcontext *ctx = (ALCcontext*) (*sound_struct)->implementation_specific;
@@ -212,7 +213,7 @@ long SoundSystemDestroy(SoundSystemStruct **sound_struct)
     return 0;
 }
 
-long SoundSystemEnumerate(char ***device_list, const int limit)
+static long openal_systemEnumerate(char ***device_list, const int limit)
 {
     assert(*device_list == NULL);
     *device_list = malloc(sizeof(char*)*2);
@@ -223,7 +224,7 @@ long SoundSystemEnumerate(char ***device_list, const int limit)
 }
 
 // pause all audio
-long SoundSystemPause()
+static long openal_systemPause(void)
 {
     ALVoices *vnode = NULL;
     ALVoices *tmp = NULL;
@@ -241,7 +242,7 @@ long SoundSystemPause()
     return 0;
 }
 
-long SoundSystemUnpause()
+static long openal_systemResume(void)
 {
     ALVoices *vnode = NULL;
     ALVoices *tmp = NULL;
@@ -820,3 +821,16 @@ static long OpenALDestroySoundBuffer(ALSoundBufferStruct **soundbuf_struct)
     return 0;
 }
 
+__attribute__((constructor(CTOR_PRIORITY_EARLY)))
+static void _init_openal(void) {
+    LOG("Initializing OpenAL sound system");
+
+    openal_audio_backend.init             = &openal_systemInit;
+    openal_audio_backend.shutdown         = &openal_systemShutdown;
+    openal_audio_backend.pause            = &openal_systemPause;
+    openal_audio_backend.resume           = &openal_systemResume;
+    openal_audio_backend.enumerateDevices = &openal_systemEnumerate;
+
+    audio_backend = &openal_audio_backend;
+}
+

src/audio/soundcore.c

@@ -50,7 +50,9 @@ static VOICE* g_pSpeakerVoice = NULL;
 
 //-------------------------------------
 
-bool soundcore_isAvailable = false;
+bool audio_isAvailable = false;
+
+audio_backend_s *audio_backend = NULL;
 
 //-----------------------------------------------------------------------------
 
@@ -239,14 +241,14 @@ static void _destroy_enumerated_sound_devices(void) {
 
 bool DSInit()
 {
-    if(soundcore_isAvailable)
+    if(audio_isAvailable)
     {
         g_uDSInitRefCount++;
         return true;        // Already initialised successfully
     }
 
     _destroy_enumerated_sound_devices();
-    num_sound_devices = SoundSystemEnumerate(&sound_devices, MAX_SOUND_DEVICES);
+    num_sound_devices = audio_backend->enumerateDevices(&sound_devices, MAX_SOUND_DEVICES);
         int hr = (num_sound_devices <= 0);
     if(hr)
     {
@@ -261,9 +263,9 @@ bool DSInit()
     {
                 if (g_lpDS)
                 {
-                    SoundSystemDestroy((SoundSystemStruct**)&g_lpDS);
+                    audio_backend->shutdown((SoundSystemStruct**)&g_lpDS);
                 }
-                hr = (int)SoundSystemCreate(sound_devices[x], (SoundSystemStruct**)&g_lpDS);
+                hr = (int)audio_backend->init(sound_devices[x], (SoundSystemStruct**)&g_lpDS);
         if(hr == 0)
         {
             bCreatedOK = true;
@@ -278,7 +280,7 @@ bool DSInit()
         return false;
     }
 
-    soundcore_isAvailable = true;
+    audio_isAvailable = true;
 
     g_uDSInitRefCount = 1;
 
@@ -291,7 +293,7 @@ void DSUninit()
 {
     _destroy_enumerated_sound_devices();
 
-    if(!soundcore_isAvailable)
+    if(!audio_isAvailable)
         return;
 
     assert(g_uDSInitRefCount);
@@ -308,8 +310,8 @@ void DSUninit()
 
     assert(g_uNumVoices == 0);
 
-        SoundSystemDestroy((SoundSystemStruct**)&g_lpDS);
-    soundcore_isAvailable = false;
+        audio_backend->shutdown((SoundSystemStruct**)&g_lpDS);
+    audio_isAvailable = false;
 }
 
 //=============================================================================

src/audio/soundcore.h

@@ -66,6 +66,7 @@ typedef struct IDirectSound {
     int (*CreateSoundBuffer)(AudioParams_s *pcDSBufferDesc, LPDIRECTSOUNDBUFFER * ppDSBuffer, void *pUnkOuter);
     int (*DestroySoundBuffer)(LPDIRECTSOUNDBUFFER * ppDSBuffer);
 } IDirectSound, *LPDIRECTSOUND;
+typedef struct IDirectSound SoundSystemStruct;
 
 typedef struct
 {
@@ -101,13 +102,22 @@ void SoundCore_SetErrorMax(const int nErrorMax);
 bool DSInit();
 void DSUninit();
 
-extern bool soundcore_isAvailable;
+extern bool audio_isAvailable;
 
-typedef struct IDirectSound SoundSystemStruct;
-long SoundSystemCreate(const char *sound_device, SoundSystemStruct **sound_struct);
-long SoundSystemDestroy(SoundSystemStruct **sound_struct);
-long SoundSystemPause();
-long SoundSystemUnpause();
-long SoundSystemEnumerate(char ***sound_devices, const int maxcount);
+typedef struct audio_backend_s {
+
+    // mandatory audio backend functions
+    long (*init)(const char *sound_device, SoundSystemStruct **sound_struct);
+    long (*shutdown)(SoundSystemStruct **sound_struct);
+    long (*pause)(void);
+    long (*resume)(void);
+    long (*enumerateDevices)(char ***sound_devices, const int maxcount);
+
+} audio_backend_s;
+
+/*
+ * The registered audio backend (renderer).
+ */
+extern audio_backend_s *audio_backend;
 
 #endif /* whole file */

src/interface.c

@@ -1549,7 +1549,7 @@ static void *interface_thread(void *current_key)
 {
     pthread_mutex_lock(&interface_mutex);
 #ifdef AUDIO_ENABLED
-    SoundSystemPause();
+    audio_backend->pause();
 #endif
     in_interface = true;
 
@@ -1593,7 +1593,7 @@ static void *interface_thread(void *current_key)
     }
 
 #ifdef AUDIO_ENABLED
-    SoundSystemUnpause();
+    audio_backend->resume();
 #endif
     pthread_mutex_unlock(&interface_mutex);
     in_interface = false;