mixer/Plugin: pass AudioOutput reference to init()

Passing a void pointer is unsafe.

src/mixer/MixerControl.cxx

@@ -26,7 +26,7 @@
 
 Mixer *
 mixer_new(EventLoop &event_loop,
-	  const MixerPlugin &plugin, void *ao,
+	  const MixerPlugin &plugin, AudioOutput &ao,
 	  const config_param &param,
 	  Error &error)
 {

src/mixer/MixerControl.hxx

@@ -28,11 +28,12 @@
 class Error;
 class Mixer;
 class EventLoop;
+struct AudioOutput;
 struct MixerPlugin;
 struct config_param;
 
 Mixer *
-mixer_new(EventLoop &event_loop, const MixerPlugin &plugin, void *ao,
+mixer_new(EventLoop &event_loop, const MixerPlugin &plugin, AudioOutput &ao,
 	  const config_param &param,
 	  Error &error);
 

src/mixer/MixerPlugin.hxx

@@ -28,6 +28,7 @@
 #define MPD_MIXER_PLUGIN_HXX
 
 struct config_param;
+struct AudioOutput;
 class Mixer;
 class EventLoop;
 class Error;
@@ -36,13 +37,13 @@ struct MixerPlugin {
 	/**
          * Alocates and configures a mixer device.
 	 *
-	 * @param ao the pointer returned by AudioOutputPlugin.init
+	 * @param ao the associated AudioOutput
 	 * @param param the configuration section
 	 * @param error_r location to store the error occurring, or
 	 * nullptr to ignore errors
 	 * @return a mixer object, or nullptr on error
 	 */
-	Mixer *(*init)(EventLoop &event_loop, void *ao,
+	Mixer *(*init)(EventLoop &event_loop, AudioOutput &ao,
 		       const config_param &param,
 		       Error &error);
 

src/mixer/plugins/AlsaMixerPlugin.cxx

@@ -167,7 +167,7 @@ AlsaMixer::Configure(const config_param &param)
 }
 
 static Mixer *
-alsa_mixer_init(EventLoop &event_loop, gcc_unused void *ao,
+alsa_mixer_init(EventLoop &event_loop, gcc_unused AudioOutput &ao,
 		const config_param &param,
 		gcc_unused Error &error)
 {

src/mixer/plugins/OssMixerPlugin.cxx

@@ -97,7 +97,7 @@ OssMixer::Configure(const config_param &param, Error &error)
 }
 
 static Mixer *
-oss_mixer_init(gcc_unused EventLoop &event_loop, gcc_unused void *ao,
+oss_mixer_init(gcc_unused EventLoop &event_loop, gcc_unused AudioOutput &ao,
 	       const config_param &param,
 	       Error &error)
 {

src/mixer/plugins/PulseMixerPlugin.cxx

@@ -35,13 +35,13 @@
 #include <assert.h>
 
 class PulseMixer final : public Mixer {
-	PulseOutput *output;
+	PulseOutput &output;
 
 	bool online;
 	struct pa_cvolume volume;
 
 public:
-	PulseMixer(PulseOutput *_output)
+	PulseMixer(PulseOutput &_output)
 		:Mixer(pulse_mixer_plugin),
 		output(_output), online(false)
 	{
@@ -130,7 +130,7 @@ PulseMixer::Update(pa_context *context, pa_stream *stream)
 }
 
 void
-pulse_mixer_on_connect(gcc_unused PulseMixer *pm,
+pulse_mixer_on_connect(gcc_unused PulseMixer &pm,
 		       struct pa_context *context)
 {
 	pa_operation *o;
@@ -151,41 +151,34 @@ pulse_mixer_on_connect(gcc_unused PulseMixer *pm,
 }
 
 void
-pulse_mixer_on_disconnect(PulseMixer *pm)
+pulse_mixer_on_disconnect(PulseMixer &pm)
 {
-	pm->Offline();
+	pm.Offline();
 }
 
 void
-pulse_mixer_on_change(PulseMixer *pm,
+pulse_mixer_on_change(PulseMixer &pm,
 		      struct pa_context *context, struct pa_stream *stream)
 {
-	pm->Update(context, stream);
+	pm.Update(context, stream);
 }
 
 static Mixer *
-pulse_mixer_init(gcc_unused EventLoop &event_loop, void *ao,
+pulse_mixer_init(gcc_unused EventLoop &event_loop, AudioOutput &ao,
 		 gcc_unused const config_param &param,
-		 Error &error)
+		 gcc_unused Error &error)
 {
-	PulseOutput *po = (PulseOutput *)ao;
-
-	if (ao == nullptr) {
-		error.Set(pulse_mixer_domain,
-			  "The pulse mixer cannot work without the audio output");
-		return nullptr;
-	}
-
+	PulseOutput &po = (PulseOutput &)ao;
 	PulseMixer *pm = new PulseMixer(po);
 
-	pulse_output_set_mixer(po, pm);
+	pulse_output_set_mixer(po, *pm);
 
 	return pm;
 }
 
 PulseMixer::~PulseMixer()
 {
-	pulse_output_clear_mixer(output, this);
+	pulse_output_clear_mixer(output, *this);
 }
 
 int

src/mixer/plugins/PulseMixerPlugin.hxx

@@ -25,12 +25,12 @@ struct pa_context;
 struct pa_stream;
 
 void
-pulse_mixer_on_connect(PulseMixer *pm, pa_context *context);
+pulse_mixer_on_connect(PulseMixer &pm, pa_context *context);
 
 void
-pulse_mixer_on_disconnect(PulseMixer *pm);
+pulse_mixer_on_disconnect(PulseMixer &pm);
 
 void
-pulse_mixer_on_change(PulseMixer *pm, pa_context *context, pa_stream *stream);
+pulse_mixer_on_change(PulseMixer &pm, pa_context *context, pa_stream *stream);
 
 #endif

src/mixer/plugins/RoarMixerPlugin.cxx

@@ -26,10 +26,10 @@
 
 class RoarMixer final : public Mixer {
 	/** the base mixer class */
-	RoarOutput *self;
+	RoarOutput &self;
 
 public:
-	RoarMixer(RoarOutput *_output)
+	RoarMixer(RoarOutput &_output)
 		:Mixer(roar_mixer_plugin),
 		self(_output) {}
 
@@ -46,11 +46,11 @@ public:
 };
 
 static Mixer *
-roar_mixer_init(gcc_unused EventLoop &event_loop, void *ao,
+roar_mixer_init(gcc_unused EventLoop &event_loop, AudioOutput &ao,
 		gcc_unused const config_param &param,
 		gcc_unused Error &error)
 {
-	return new RoarMixer((RoarOutput *)ao);
+	return new RoarMixer((RoarOutput &)ao);
 }
 
 int

src/mixer/plugins/SoftwareMixerPlugin.cxx

@@ -84,7 +84,8 @@ public:
 };
 
 static Mixer *
-software_mixer_init(gcc_unused EventLoop &event_loop, gcc_unused void *ao,
+software_mixer_init(gcc_unused EventLoop &event_loop,
+		    gcc_unused AudioOutput &ao,
 		    gcc_unused const config_param &param,
 		    gcc_unused Error &error)
 {

src/mixer/plugins/WinmmMixerPlugin.cxx

@@ -31,10 +31,10 @@
 #include <windows.h>
 
 class WinmmMixer final : public Mixer {
-	WinmmOutput *output;
+	WinmmOutput &output;
 
 public:
-	WinmmMixer(WinmmOutput *_output)
+	WinmmMixer(WinmmOutput &_output)
 		:Mixer(winmm_mixer_plugin),
 		output(_output) {
 	}
@@ -67,13 +67,11 @@ winmm_volume_encode(int volume)
 }
 
 static Mixer *
-winmm_mixer_init(gcc_unused EventLoop &event_loop, void *ao,
+winmm_mixer_init(gcc_unused EventLoop &event_loop, AudioOutput &ao,
 		 gcc_unused const config_param &param,
 		 gcc_unused Error &error)
 {
-	assert(ao != nullptr);
-
-	return new WinmmMixer((WinmmOutput *)ao);
+	return new WinmmMixer((WinmmOutput &)ao);
 }
 
 int