pipe: add helper function music_pipe_empty()

src/output_all.c

@@ -266,7 +266,7 @@ audio_output_all_open(const struct audio_format *audio_format,
 	else
 		/* if the pipe hasn't been cleared, the the audio
 		   format must not have changed */
-		assert(music_pipe_size(g_mp) == 0 ||
+		assert(music_pipe_empty(g_mp) ||
 		       audio_format_equals(audio_format,
 					   &input_audio_format));
 
@@ -378,7 +378,7 @@ audio_output_all_check(void)
 	assert(g_mp != NULL);
 
 	while ((chunk = music_pipe_peek(g_mp)) != NULL) {
-		assert(music_pipe_size(g_mp) > 0);
+		assert(!music_pipe_empty(g_mp));
 
 		if (!chunk_is_consumed(chunk))
 			/* at least one output is not finished playing

src/pipe.h

@@ -99,4 +99,10 @@ music_pipe_push(struct music_pipe *mp, struct music_chunk *chunk);
 unsigned
 music_pipe_size(const struct music_pipe *mp);
 
+static inline bool
+music_pipe_empty(const struct music_pipe *mp)
+{
+	return music_pipe_size(mp) == 0;
+}
+
 #endif

src/player_thread.c

@@ -736,7 +736,7 @@ static void do_play(void)
 
 		if (player.paused)
 			notify_wait(&pc.notify);
-		else if (music_pipe_size(player.pipe) > 0) {
+		else if (!music_pipe_empty(player.pipe)) {
 			/* at least one music chunk is ready - send it
 			   to the audio output */
 
@@ -757,7 +757,7 @@ static void do_play(void)
 			/* check the size of the pipe again, because
 			   the decoder thread may have added something
 			   since we last checked */
-			if (music_pipe_size(player.pipe) == 0)
+			if (music_pipe_empty(player.pipe))
 				break;
 		} else {
 			/* the decoder is too busy and hasn't provided