Changing UpdateStreamPacket protobuf definition for chromoting

remoting/client/decoder.h

 // Copyright (c) 2010 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 REMOTING_CLIENT_DECODER_H_
 #define REMOTING_CLIENT_DECODER_H_
 
 #include <vector>
 
 #include "base/task.h"
@@ skipping 39 matching lines @@
   // the codec format.
   // TODO(hclam): Provide more information when calling this function.
   virtual bool BeginDecode(scoped_refptr<media::VideoFrame> frame,
                            UpdatedRects* updated_rects,
                            Task* partial_decode_done,
                            Task* decode_done) = 0;
 
   // Give a HostMessage that contains the update stream packet that contains
   // the encoded data to the decoder.
   // The decoder will own |message| and is responsible for deleting it.
+  //
   // If the decoder has written something into |frame|,
   // |partial_decode_done_| is called with |frame| and updated regions.
   // Return true if the decoder can accept |message| and decode it.
+  //
+  // HostMessage returned by this method will contain a
+  // UpdateStreamPacketMessage.
+  // This message will contain either:
+  // 1. UpdateStreamBeginRect
+  // 2. UpdateStreamRectData
+  // 3. UpdateStreamEndRect
+  //
+  // See remoting/base/protocol/chromotocol.proto for more information about
+  // these messages.
   virtual bool PartialDecode(HostMessage* message) = 0;
 
   // Notify the decoder that we have received the last update stream packet.
   // If the decoding of the update stream has completed |decode_done_| is
   // called with |frame|.
   // If the update stream is not received fully and this method is called the
   // decoder should also call |decode_done_| as soon as possible.
   virtual void EndDecode() = 0;
+
+ protected:
+  // Every decoder will have two internal states because there are three
+  // kinds of messages send to PartialDecode().
+  //
+  // Here's a state diagram:
+  //
+  //                UpdateStreamBeginRect       UpdateStreamRectData
+  //                    ..............              ............
+  //                   .              .            .            .
+  //                  .                v          .              .
+  // kWaitingForBeginRect         kWaitingForRectData            .
+  //                  ^                .          ^              .
+  //                   .              .            .            .
+  //                    ..............              ............
+  //                    UpdateStreaEndRect
+  enum State {
+    // In this state the decoder is waiting for UpdateStreamBeginRect.
+    // After receiving UpdateStreaBeginRect, the encoder will transit to
+    // to kWaitingForRectData state.
+    kWaitingForBeginRect,
+
+    // In this state the decoder is waiting for UpdateStreamRectData.
+    // The decode remains in this state if UpdateStreamRectData is received.
+    // The decoder will transit to kWaitingForBeginRect if UpdateStreamEndRect
+    // is received.
+    kWaitingForRectData,
+  };
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CLIENT_DECODER_H_