PacketBuffer is now ref counted.

webrtc/modules/video_coding/packet_buffer.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/modules/video_coding/packet_buffer.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/video_coding/frame_object.h"
 #include "webrtc/system_wrappers/include/clock.h"
 
 namespace webrtc {
 namespace video_coding {
 
+rtc::scoped_refptr<PacketBuffer> PacketBuffer::Create(
+     Clock* clock,
+     size_t start_buffer_size,
+     size_t max_buffer_size,
+     OnCompleteFrameCallback* frame_callback) {
+    return rtc::scoped_refptr<PacketBuffer>(new PacketBuffer(clock,
+      start_buffer_size, max_buffer_size, frame_callback));
+}
+
 PacketBuffer::PacketBuffer(Clock* clock,
                            size_t start_buffer_size,
                            size_t max_buffer_size,
                            OnCompleteFrameCallback* frame_callback)
     : clock_(clock),
       size_(start_buffer_size),
       max_size_(max_buffer_size),
       first_seq_num_(0),
       last_seq_num_(0),
       first_packet_received_(false),
@@ skipping 128 matching lines @@
         if (sequence_buffer_[start_index].frame_begin)
           break;
 
         start_index = start_index > 0 ? start_index - 1 : size_ - 1;
         start_seq_num--;
       }
 
       std::unique_ptr<RtpFrameObject> frame(
           new RtpFrameObject(this, start_seq_num, seq_num, frame_size,
                              max_nack_count, clock_->TimeInMilliseconds()));
       reference_finder_.ManageFrame(std::move(frame));

[danilchap, 2016/08/02 14:04:45]

this look like a circular dependency:
{
  auto buffer = PacketBuffer::Create(); // 1 reference.
  buffer->findFrames(...); // create a frame, store it in reference_finder_
stashed_frames_ queue, now PacketBuffer has 2 references.
} // destroy buffer scoped_refptr, reducing PacketBuffer reference counter to 1.
// Now there is an unreachable PacketBuffer that contain refernce_finder_ with 1
RtpFrameObject that holds that single reference to PacketBuffer.

[philipel, 2016/08/02 14:39:59]

You are right, the risk of having a stashed frame is significant. I have added a
Stop function to PacketBuffer/RtpFrameReferenceFinder which clears all stashed
frames.

     }
 
     index = (index + 1) % size_;
     ++seq_num;
   }
 }
 
 void PacketBuffer::ReturnFrame(RtpFrameObject* frame) {
   rtc::CritScope lock(&crit_);
   size_t index = frame->first_seq_num() % size_;
@@ skipping 49 matching lines @@
 }
 
 void PacketBuffer::Clear() {
   rtc::CritScope lock(&crit_);
   for (size_t i = 0; i < size_; ++i)
     sequence_buffer_[i].used = false;
 
   first_packet_received_ = false;
 }
 
+int PacketBuffer::AddRef() const {
+  return rtc::AtomicOps::Increment(&ref_count_);
+}
+
+int PacketBuffer::Release() const {
+  int count = rtc::AtomicOps::Decrement(&ref_count_);
+  if (!count) {
+    delete this;
+  }
+  return count;
+}
+
 }  // namespace video_coding
 }  // namespace webrtc