[GCM] Add basic collapse key support for upstream

google_apis/gcm/engine/mcs_client.h

 // Copyright 2013 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.
 
 #ifndef GOOGLE_APIS_GCM_ENGINE_MCS_CLIENT_H_
 #define GOOGLE_APIS_GCM_ENGINE_MCS_CLIENT_H_
 
 #include <deque>
 #include <map>
 #include <string>
@@ skipping 18 matching lines @@
 }  // namespace protobuf
 }  // namespace google
 
 namespace mcs_proto {
 class LoginRequest;
 }
 
 namespace gcm {
 
 class ConnectionFactory;
+class CollapseKey;

[jianli, 2014/02/04 22:55:14]

nit: sort

[Nicolas Zea, 2014/02/12 23:35:46]

Done.

 struct ReliablePacketInfo;
 
 // An MCS client. This client is in charge of all communications with an
 // MCS endpoint, and is capable of reliably sending/receiving GCM messages.
 // NOTE: Not thread safe. This class should live on the same thread as that
 // network requests are performed on.
 class GCM_EXPORT MCSClient {
  public:
   enum State {
     UNINITIALIZED,  // Uninitialized.
@@ skipping 162 matching lines @@
   ConnectionHandler* connection_handler_;
 
   // -----  Reliablie Message Queue section -----
   // Note: all queues/maps are ordered from oldest (front/begin) message to
   // most recent (back/end).
 
   // Send/acknowledge queues.
   std::deque<MCSPacketInternal> to_send_;
   std::deque<MCSPacketInternal> to_resend_;
 
+  // Map of collapse keys to their pending messages.
+  std::map<CollapseKey, ReliablePacketInfo*> collapse_key_map_;

[jianli, 2014/02/04 22:55:14]

It seems that the value "ReliablePacketInfo*" is owned by to_send_ and
to_resend_. If the packet is removed from to_send_ and we forget to update
collapse_key_map_, we will get the crash. This might happen when we call
SendMessage and then ResetStateAndBuildLoginRequest.

[Nicolas Zea, 2014/02/12 23:35:46]

Good catch. Note that to_resend_ will never share packets with the
collapse_key_map_, only to_send_. I've gone ahead and added the
PopMessageForSend helper to ensure the collapse key map is always updated if
necessary. 

+
   // Last device_to_server stream id acknowledged by the server.
   StreamId last_device_to_server_stream_id_received_;
   // Last server_to_device stream id acknowledged by this device.
   StreamId last_server_to_device_stream_id_received_;
   // The stream id for the last sent message. A new message should consume
   // stream_id_out_ + 1.
   StreamId stream_id_out_;
   // The stream id of the last received message. The LoginResponse will always
   // have a stream id of 1, and stream ids increment by 1 for each received
   // message.
@@ skipping 21 matching lines @@
   HeartbeatManager heartbeat_manager_;
 
   base::WeakPtrFactory<MCSClient> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MCSClient);
 };
 
 } // namespace gcm
 
 #endif  // GOOGLE_APIS_GCM_ENGINE_MCS_CLIENT_H_