MixStream: Add a function to atomically soundtouchify a stream when n…

…eeded.

src/MixStreamCore.c

@@ -42,11 +42,14 @@ struct _MixStream {
   int out_sample_size;
   gboolean out_samples_signed;
   gboolean byteswap_needed;
+  GMutex* st_mutex;
 };
 
 static GHashTable* chan_table = NULL;
 static GStaticMutex chan_table_mutex = G_STATIC_MUTEX_INIT;
 
+static void _mix_stream_soundtouchify(MixStream* stream);
+
 
 /* Create a stream that will play data returned by read_cb.
  *   - samprate and channels specify the format returned by read_cb
@@ -93,10 +96,10 @@ MixStream* mix_stream_new(int samprate, int channels, mix_stream_read_cb read_cb
     default: g_assert_not_reached(); break;
   }
 
+  stream->st_mutex = g_mutex_new();
+
   if (stream->samprate != stream->out_freq) {
-    stream->soundtouch = soundtouch_new();
-    soundtouch_set_sample_rate(stream->soundtouch, stream->samprate);
-    soundtouch_set_channels(stream->soundtouch, stream->channels);
+    _mix_stream_soundtouchify(stream);
     soundtouch_set_rate(stream->soundtouch, (float)stream->samprate/(float)stream->out_freq);
   }
 
@@ -109,13 +112,27 @@ void mix_stream_destroy(MixStream* stream)
 {
   if (stream->channel != -1)
     mix_stream_stop(stream);
+  g_mutex_free(stream->st_mutex);
   if (stream->soundtouch != NULL)
     soundtouch_delete(stream->soundtouch);
   stream->free_cb(stream->cb_data);
   g_free(stream);
 }
 
 
+/* Ensure the stream is using a soundtouch object. */
+static void _mix_stream_soundtouchify(MixStream* stream)
+{
+  g_mutex_lock(stream->st_mutex);
+  if (stream->soundtouch == NULL) {
+    stream->soundtouch = soundtouch_new();
+    soundtouch_set_sample_rate(stream->soundtouch, stream->samprate);
+    soundtouch_set_channels(stream->soundtouch, stream->channels);
+  }
+  g_mutex_unlock(stream->st_mutex);
+}
+
+
 /* Fill a float buffer using a read callback and possibly a SoundTouch object. */
 static gsize _mix_stream_fill_floatbuf(MixStream* stream, float* buf, gsize numframes, guint channels)
 {
@@ -124,6 +141,7 @@ static gsize _mix_stream_fill_floatbuf(MixStream* stream, float* buf, gsize numf
   gsize frames_read;
   while (numframes > 0) {
 
+    g_mutex_lock(stream->st_mutex);
     if (stream->soundtouch == NULL) {
       frames_read = stream->read_cb(buf, numframes * frame_size, stream->cb_data) / frame_size;
     } else {
@@ -138,6 +156,7 @@ static gsize _mix_stream_fill_floatbuf(MixStream* stream, float* buf, gsize numf
       }
       frames_read = soundtouch_receive_samples(stream->soundtouch, buf, numframes);
     }
+    g_mutex_unlock(stream->st_mutex);
 
     if (frames_read == 0) {
       if (frames_obtained != 0) {