audio_format: added audio_format_clear() and audio_format_defined()

audio_format_clear() sets an audio_format struct to an cleared
(undefined) state, which is both faster and smaller than memset(0).
audio_format_defined() checks if the audio_format struct actually has
a defined value (i.e. non-zero).  Both can be used to avoid pointers
to audio_format, replacing the "NULL" value with an "undefined"
audio_format.

2 files changed, 13 insertions, 1 deletions

diff --git a/src/audio.c b/src/audio.c
index 839052dc2..dead45991 100644
--- a/src/audio.c
+++ b/src/audio.c
@@ -231,7 +231,7 @@ static void syncAudioDeviceStates(void)
 	struct audio_output *audioOutput;
 	unsigned int i;
 
-	if (!audio_format.channels)
+	if (!audio_format_defined(&audio_format))
 		return;
 
 	for (i = 0; i < audioOutputArraySize; ++i) {
diff --git a/src/audio_format.h b/src/audio_format.h
index 1cfb258ae..d2461a338 100644
--- a/src/audio_format.h
+++ b/src/audio_format.h
@@ -27,6 +27,18 @@ struct audio_format {
 	mpd_sint8 channels;
 };
 
+static inline void audio_format_clear(struct audio_format *af)
+{
+	af->sampleRate = 0;
+	af->bits = 0;
+	af->channels = 0;
+}
+
+static inline int audio_format_defined(const struct audio_format *af)
+{
+	return af->sampleRate != 0;
+}
+
 static inline int audio_format_equals(const struct audio_format *a,
 				      const struct audio_format *b)
 {