rtprtxsend: use a GSequence to implement the buffer queue

This has the advantage that searching the queue to find the
buffer with the requested seqnum is done with binary search.

gst/rtpmanager/gstrtprtxsend.c

@@ -165,8 +165,8 @@ static void
 gst_rtp_rtx_send_reset (GstRtpRtxSend * rtx, gboolean full)
 {
   g_mutex_lock (&rtx->lock);
-  g_queue_foreach (rtx->queue, (GFunc) buffer_queue_item_free, NULL);
+  g_sequence_remove_range (g_sequence_get_begin_iter (rtx->queue),
-  g_queue_clear (rtx->queue);
+      g_sequence_get_end_iter (rtx->queue));
   g_queue_foreach (rtx->pending, (GFunc) gst_buffer_unref, NULL);
   g_queue_clear (rtx->pending);
   rtx->master_ssrc = 0;
@@ -183,7 +183,7 @@ gst_rtp_rtx_send_finalize (GObject * object)
   GstRtpRtxSend *rtx = GST_RTP_RTX_SEND (object);
 
   gst_rtp_rtx_send_reset (rtx, TRUE);
-  g_queue_free (rtx->queue);
+  g_sequence_free (rtx->queue);
   g_queue_free (rtx->pending);
   g_mutex_clear (&rtx->lock);
 
@@ -215,7 +215,7 @@ gst_rtp_rtx_send_init (GstRtpRtxSend * rtx)
       GST_DEBUG_FUNCPTR (gst_rtp_rtx_send_chain));
   gst_element_add_pad (GST_ELEMENT (rtx), rtx->sinkpad);
 
-  rtx->queue = g_queue_new ();
+  rtx->queue = g_sequence_new ((GDestroyNotify) buffer_queue_item_free);
   rtx->pending = g_queue_new ();
   g_mutex_init (&rtx->lock);
 
@@ -241,29 +241,14 @@ choose_ssrc (GstRtpRtxSend * rtx)
   return ssrc;
 }
 
-typedef struct
+static gint
+buffer_queue_items_cmp (BufferQueueItem * a, BufferQueueItem * b,
+    gpointer user_data)
 {
-  GstRtpRtxSend *rtx;
+  /* gst_rtp_buffer_compare_seqnum returns the opposite of what we want,
-  guint seqnum;
+   * it returns negative when seqnum1 > seqnum2 and we want negative
-  gboolean found;
+   * when b > a, i.e. a is smaller, so it comes first in the sequence */
-} RTXData;
+  return gst_rtp_buffer_compare_seqnum (b->seqnum, a->seqnum);
-
-/* traverse queue history and try to find the buffer that the
- * requested seqnum */
-static void
-push_seqnum (BufferQueueItem * item, RTXData * data)
-{
-  GstRtpRtxSend *rtx = data->rtx;
-
-  if (data->found)
-    return;
-
-  /* data->seqnum comes from the request */
-  if (item->seqnum == data->seqnum) {
-    data->found = TRUE;
-    GST_DEBUG_OBJECT (rtx, "found %" G_GUINT16_FORMAT, item->seqnum);
-    g_queue_push_tail (rtx->pending, gst_buffer_ref (item->buffer));
-  }
 }
 
 static gboolean
@@ -281,7 +266,6 @@ gst_rtp_rtx_send_src_event (GstPad * pad, GstObject * parent, GstEvent * event)
       if (gst_structure_has_name (s, "GstRTPRetransmissionRequest")) {
         guint32 seqnum = 0;
         guint ssrc = 0;
-        RTXData data;
 
         /* retrieve seqnum of the packet that need to be restransmisted */
         if (!gst_structure_get_uint (s, "seqnum", &seqnum))
@@ -298,12 +282,20 @@ gst_rtp_rtx_send_src_event (GstPad * pad, GstObject * parent, GstEvent * event)
         g_mutex_lock (&rtx->lock);
         /* check if request is for us */
         if (rtx->master_ssrc == ssrc) {
+          GSequenceIter *iter;
+          BufferQueueItem search_item;
+
+          /* update statistics */
           ++rtx->num_rtx_requests;
-          data.rtx = rtx;
+
-          data.seqnum = seqnum;
+          search_item.seqnum = seqnum;
-          data.found = FALSE;
+          iter = g_sequence_lookup (rtx->queue, &search_item,
-          /* TODO do a binary search because rtx->queue is sorted by seq num */
+              (GCompareDataFunc) buffer_queue_items_cmp, NULL);
-          g_queue_foreach (rtx->queue, (GFunc) push_seqnum, &data);
+          if (iter) {
+            BufferQueueItem *item = g_sequence_get (iter);
+            GST_DEBUG_OBJECT (rtx, "found %" G_GUINT16_FORMAT, item->seqnum);
+            g_queue_push_tail (rtx->pending, gst_buffer_ref (item->buffer));
+          }
         }
         g_mutex_unlock (&rtx->lock);
 
@@ -326,8 +318,8 @@ gst_rtp_rtx_send_src_event (GstPad * pad, GstObject * parent, GstEvent * event)
           rtx->rtx_ssrc = choose_ssrc (rtx);
 
           /* clear buffers we already saved */
-          g_queue_foreach (rtx->queue, (GFunc) gst_buffer_unref, NULL);
+          g_sequence_remove_range (g_sequence_get_begin_iter (rtx->queue),
-          g_queue_clear (rtx->queue);
+              g_sequence_get_end_iter (rtx->queue));
 
           /* clear buffers that are about to be retransmited */
           g_queue_foreach (rtx->pending, (GFunc) gst_buffer_unref, NULL);
@@ -394,8 +386,10 @@ gst_rtp_rtx_send_get_ts_diff (GstRtpRtxSend * self)
   BufferQueueItem *high_buf, *low_buf;
   guint32 result;
 
-  high_buf = g_queue_peek_head (self->queue);
+  high_buf =
-  low_buf = g_queue_peek_tail (self->queue);
+      g_sequence_get (g_sequence_iter_prev (g_sequence_get_end_iter
+          (self->queue)));
+  low_buf = g_sequence_get (g_sequence_get_begin_iter (self->queue));
 
   if (!high_buf || !low_buf || high_buf == low_buf)
     return 0;
@@ -521,16 +515,16 @@ gst_rtp_rtx_send_chain (GstPad * pad, GstObject * parent, GstBuffer * buffer)
   item->seqnum = seqnum;
   item->timestamp = rtptime;
   item->buffer = gst_buffer_ref (buffer);
-  g_queue_push_head (rtx->queue, item);
+  g_sequence_append (rtx->queue, item);
 
   /* remove oldest packets from history if they are too many */
   if (rtx->max_size_packets) {
-    while (g_queue_get_length (rtx->queue) > rtx->max_size_packets)
+    while (g_sequence_get_length (rtx->queue) > rtx->max_size_packets)
-      buffer_queue_item_free (g_queue_pop_tail (rtx->queue));
+      g_sequence_remove (g_sequence_get_begin_iter (rtx->queue));
   }
   if (rtx->max_size_time) {
     while (gst_rtp_rtx_send_get_ts_diff (rtx) > rtx->max_size_time)
-      buffer_queue_item_free (g_queue_pop_tail (rtx->queue));
+      g_sequence_remove (g_sequence_get_begin_iter (rtx->queue));
   }
 
   /* within lock, get packets that have to be retransmited */

gst/rtpmanager/gstrtprtxsend.h

@@ -48,7 +48,7 @@ struct _GstRtpRtxSend
   GMutex lock;
 
   /* history of rtp packets */
-  GQueue *queue;
+  GSequence *queue;
   /* rtp packets that will be pushed upon next buffer */
   GQueue *pending;