*: use nullptr instead of NULL

src/filter/ChainFilterPlugin.cxx

@@ -152,8 +152,8 @@ ChainFilter::FilterPCM(const void *src, size_t src_size,
 		   into the current one */
 		src = child.filter->FilterPCM(src, src_size, &src_size,
 					      error);
-		if (src == NULL)
-			return NULL;
+		if (src == nullptr)
+			return nullptr;
 	}
 
 	/* return the output of the last filter */

src/filter/ReplayGainFilterPlugin.cxx

@@ -80,7 +80,7 @@ public:
 	}
 
 	void SetMixer(Mixer *_mixer, unsigned _base) {
-		assert(_mixer == NULL || (_base > 0 && _base <= 100));
+		assert(_mixer == nullptr || (_base > 0 && _base <= 100));
 
 		mixer = _mixer;
 		base = _base;
@@ -89,7 +89,7 @@ public:
 	}
 
 	void SetInfo(const ReplayGainInfo *_info) {
-		if (_info != NULL) {
+		if (_info != nullptr) {
 			info = *_info;
 			info.Complete();
 		} else
@@ -137,7 +137,7 @@ ReplayGainFilter::Update()
 	} else
 		volume = PCM_VOLUME_1;
 
-	if (mixer != NULL) {
+	if (mixer != nullptr) {
 		/* update the hardware mixer volume */
 
 		unsigned _volume = (volume * base) / PCM_VOLUME_1;
@@ -198,7 +198,7 @@ ReplayGainFilter::FilterPCM(const void *src, size_t src_size,
 				  volume);
 	if (!success) {
 		error.Set(replay_gain_domain, "pcm_volume() has failed");
-		return NULL;
+		return nullptr;
 	}
 
 	return dest;

src/filter/ReplayGainFilterPlugin.hxx

@@ -28,7 +28,7 @@ class Mixer;
 /**
  * Enables or disables the hardware mixer for applying replay gain.
  *
- * @param mixer the hardware mixer, or NULL to fall back to software
+ * @param mixer the hardware mixer, or nullptr to fall back to software
  * volume
  * @param base the base volume level for scale=1.0, between 1 and 100
  * (including).
@@ -40,7 +40,7 @@ replay_gain_filter_set_mixer(Filter *_filter, Mixer *mixer,
 /**
  * Sets a new #replay_gain_info at the beginning of a new song.
  *
- * @param info the new #replay_gain_info value, or NULL if no replay
+ * @param info the new #replay_gain_info value, or nullptr if no replay
  * gain data is available for the current song
  */
 void