Implement video frame acknowledgements in the chromoting protocol.

remoting/protocol/host_video_dispatcher.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "remoting/protocol/host_video_dispatcher.h"
 
 #include "base/bind.h"
+#include "base/callback_helpers.h"
 #include "net/socket/stream_socket.h"
 #include "remoting/base/constants.h"
-#include "remoting/proto/video.pb.h"
+#include "remoting/protocol/errors.h"
 #include "remoting/protocol/message_serialization.h"
 
 namespace remoting {
 namespace protocol {
 
+HostVideoDispatcher::PendingFrame::PendingFrame(int frame_id,
+                                                const base::Closure& done)
+    : frame_id(frame_id), done(done) {
+}
+
 HostVideoDispatcher::HostVideoDispatcher()
-    : ChannelDispatcherBase(kVideoChannelName) {
+    : ChannelDispatcherBase(kVideoChannelName),
+      frame_id_(0),
+      parser_(
+          base::Bind(&HostVideoDispatcher::OnVideoAck, base::Unretained(this)),
+          reader()) {
 }
 
 HostVideoDispatcher::~HostVideoDispatcher() {
 }
 
 void HostVideoDispatcher::ProcessVideoPacket(scoped_ptr<VideoPacket> packet,
                                              const base::Closure& done) {
-  writer()->Write(SerializeAndFrameMessage(*packet), done);
+  // For older clients that don't send explicit video Ack message call |done| as
+  // soon as the frame is pushed to the channel.
+  if (channel_config().version < kVideoWithAckStreamVersion) {
+    writer()->Write(SerializeAndFrameMessage(*packet), done);
+    return;
+  }
+
+  pending_frames_.push_back(PendingFrame(frame_id_, done));
+  packet->set_frame_id(frame_id_);
+  frame_id_++;
+  writer()->Write(SerializeAndFrameMessage(*packet), base::Closure());
+}
+
+bool HostVideoDispatcher::SupportsAcks() {
+  return channel_config().version >= kVideoWithAckStreamVersion;
+}
+
+void HostVideoDispatcher::OnVideoAck(scoped_ptr<VideoAck> ack,
+                                     const base::Closure& done) {

[Wez, 2015/01/21 01:35:40]

Need some kind of comment and bug # reference in here to explain that we'll have
some flow-control logic in here eventually.

[Sergey Ulanov, 2015/01/29 01:33:29]

Done.

+  base::ScopedClosureRunner done_runner(done);
+
+  if (pending_frames_.empty() ||
+      pending_frames_.front().frame_id != ack->frame_id()) {
+    NotifyError(INCOMPATIBLE_PROTOCOL);
+    return;
+  }
+
+  pending_frames_.front().done.Run();

[Wez, 2015/01/21 01:35:40]

Are you guaranteed that the callback won't delete |this|? If not then copy the
callback and pop_front() before you Run() it.

[Sergey Ulanov, 2015/01/29 01:33:29]

Done.

+  pending_frames_.pop_front();
 }
 
 }  // namespace protocol
 }  // namespace remoting