output: semi-asynchronous playback

Send an output buffer to all output plugins at the same time, instead
of waiting for each of them separately.  Make several functions
non-blocking, and introduce the new function audio_output_wait_all()
to synchronize with all audio output threads.

src/audio.c

@@ -213,6 +213,31 @@ int isCurrentAudioFormat(const struct audio_format *audioFormat)
 	return audio_format_equals(audioFormat, &audio_buffer.format);
 }
 
+static void audio_output_wait(struct audio_output *ao)
+{
+	while (!audio_output_command_is_finished(ao))
+		notify_wait(&audio_output_client_notify);
+}
+
+static void audio_output_wait_all(void)
+{
+	unsigned i;
+
+	while (1) {
+		int finished = 1;
+
+		for (i = 0; i < audioOutputArraySize; ++i)
+			if (audioDeviceStates[i] == DEVICE_ON &&
+			    !audio_output_command_is_finished(&audioOutputArray[i]))
+				finished = 0;
+
+		if (finished)
+			break;
+
+		notify_wait(&audio_output_client_notify);
+	};
+}
+
 static void syncAudioDeviceStates(void)
 {
 	struct audio_output *audioOutput;
@@ -239,6 +264,7 @@ static void syncAudioDeviceStates(void)
 			break;
 		case DEVICE_DISABLE:
 			audio_output_cancel(audioOutput);
+			audio_output_wait(audioOutput);
 			audio_output_close(audioOutput);
 			audioDeviceStates[i] = DEVICE_OFF;
 		}
@@ -255,19 +281,39 @@ static int flushAudioBuffer(void)
 
 	syncAudioDeviceStates();
 
-	for (i = 0; i < audioOutputArraySize; ++i) {
-		if (audioDeviceStates[i] != DEVICE_ON)
-			continue;
-		err = audio_output_play(&audioOutputArray[i],
-					audio_buffer.buffer,
-					audio_buffer.position);
-		if (!err)
-			ret = 0;
-		else if (err < 0)
-			/* device should already be closed if the play
-			 * func returned an error */
-			audioDeviceStates[i] = DEVICE_ENABLE;
-	}
+	for (i = 0; i < audioOutputArraySize; ++i)
+		if (audioDeviceStates[i] == DEVICE_ON)
+			audio_output_play(&audioOutputArray[i],
+					  audio_buffer.buffer,
+					  audio_buffer.position);
+
+	while (1) {
+		int finished = 1;
+
+		for (i = 0; i < audioOutputArraySize; ++i) {
+			const struct audio_output *ao = &audioOutputArray[i];
+
+			if (audioDeviceStates[i] != DEVICE_ON)
+				continue;
+
+			if (audio_output_command_is_finished(ao)) {
+				err = audio_output_get_result(ao);
+				if (!err)
+					ret = 0;
+				else if (err < 0)
+					/* device should already be
+					   closed if the play func
+					   returned an error */
+					audioDeviceStates[i] = DEVICE_ENABLE;
+			} else
+				finished = 0;
+		}
+
+		if (finished)
+			break;
+
+		notify_wait(&audio_output_client_notify);
+	};
 
 	audio_buffer.position = 0;
 
@@ -370,6 +416,8 @@ void dropBufferedAudio(void)
 		if (audioDeviceStates[i] == DEVICE_ON)
 			audio_output_cancel(&audioOutputArray[i]);
 	}
+
+	audio_output_wait_all();
 }
 
 void closeAudioDevice(void)
@@ -399,6 +447,8 @@ void sendMetadataToAudioDevice(const struct tag *tag)
 	for (i = 0; i < audioOutputArraySize; ++i)
 		if (audioDeviceStates[i] == DEVICE_ON)
 			audio_output_send_tag(&audioOutputArray[i], tag);
+
+	audio_output_wait_all();
 }
 
 int enableAudioDevice(unsigned int device)

src/output_control.c

@@ -41,6 +41,14 @@ static void ao_command(struct audio_output *ao, enum audio_output_command cmd)
 	ao_command_wait(ao);
 }
 
+static void ao_command_async(struct audio_output *ao,
+			     enum audio_output_command cmd)
+{
+	assert(ao->command == AO_COMMAND_NONE);
+	ao->command = cmd;
+	notify_signal(&ao->notify);
+}
+
 int audio_output_open(struct audio_output *audioOutput,
 		      const struct audio_format *audioFormat)
 {
@@ -78,22 +86,20 @@ int audio_output_open(struct audio_output *audioOutput,
 	return ret;
 }
 
-int audio_output_play(struct audio_output *audioOutput,
-		      const char *playChunk, size_t size)
+void audio_output_play(struct audio_output *audioOutput,
+		       const char *playChunk, size_t size)
 {
 	if (!audioOutput->open)
-		return -1;
+		return;
 
 	audioOutput->args.play.data = playChunk;
 	audioOutput->args.play.size = size;
-	ao_command(audioOutput, AO_COMMAND_PLAY);
-
-	return audioOutput->result;
+	ao_command_async(audioOutput, AO_COMMAND_PLAY);
 }
 
 void audio_output_cancel(struct audio_output *audioOutput)
 {
-	ao_command(audioOutput, AO_COMMAND_CANCEL);
+	ao_command_async(audioOutput, AO_COMMAND_CANCEL);
 }
 
 void audio_output_close(struct audio_output *audioOutput)
@@ -120,5 +126,5 @@ void audio_output_send_tag(struct audio_output *audioOutput,
 		return;
 
 	audioOutput->args.tag = tag;
-	ao_command(audioOutput, AO_COMMAND_SEND_TAG);
+	ao_command_async(audioOutput, AO_COMMAND_SEND_TAG);
 }

src/output_control.h

@@ -30,8 +30,8 @@ struct tag;
 int audio_output_init(struct audio_output *, ConfigParam * param);
 int audio_output_open(struct audio_output *audioOutput,
 		      const struct audio_format *audioFormat);
-int audio_output_play(struct audio_output *audioOutput,
-		      const char *playChunk, size_t size);
+void audio_output_play(struct audio_output *audioOutput,
+		       const char *playChunk, size_t size);
 void audio_output_cancel(struct audio_output *audioOutput);
 void audio_output_close(struct audio_output *audioOutput);
 void audio_output_finish(struct audio_output *audioOutput);

src/output_internal.h

@@ -109,4 +109,16 @@ struct audio_output {
  */
 extern struct notify audio_output_client_notify;
 
+static inline int
+audio_output_command_is_finished(const struct audio_output *ao)
+{
+	return ao->command == AO_COMMAND_NONE;
+}
+
+static inline int
+audio_output_get_result(const struct audio_output *ao)
+{
+	return ao->result;
+}
+
 #endif