Implement video frame acknowledgements in the chromoting protocol.

remoting/protocol/message_decoder.h

 // Copyright (c) 2012 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_PROTOCOL_MESSAGE_DECODER_H_
 #define REMOTING_PROTOCOL_MESSAGE_DECODER_H_
 
 #include <deque>
 #include <list>
 
@@ skipping 17 matching lines @@
 //   | message_size | message_data |
 //   +--------------+--------------+
 //
 // Here, message_size is 4-byte integer that represents size of
 // message_data in bytes. message_data - content of the message.
 class MessageDecoder {
  public:
   MessageDecoder();
   virtual ~MessageDecoder();
 
+  // True if the buffer is empty. If the buffer is empty and GetNextMessage()
+  // returns nullptr it means that the buffer contains incomplete messages.
+  bool is_buffer_empty() { return buffer_.total_bytes() == 0; }
+
   // Add next chunk of data. MessageDecoder retains |data| until all
   // its bytes are consumed.
   void AddData(scoped_refptr<net::IOBuffer> data, int data_size);
 
   // Returns next message from the stream. Ownership of the result is
   // passed to the caller. Returns nullptr if there are no complete
   // messages yet, otherwise returns a buffer that contains one
   // message.
   CompoundBuffer* GetNextMessage();
 
  private:
   // Retrieves the read payload size of the current protocol buffer via |size|.
   // Returns false and leaves |size| unmodified, if we do not have enough data
   // to retrieve the current size.
   bool GetPayloadSize(int* size);
 
   CompoundBuffer buffer_;
 
   // |next_payload_| stores the size of the next payload if known.
   // |next_payload_known_| is true if the size of the next payload is known.
   // After one payload is read this is reset to false.
   int next_payload_;
   bool next_payload_known_;
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_MESSAGE_DECODER_H_