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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef REMOTING_PROTOCOL_MESSAGE_DECODER_H_
      6 #define REMOTING_PROTOCOL_MESSAGE_DECODER_H_
      7 
      8 #include <deque>
      9 #include <list>
     10 
     11 #include "base/memory/ref_counted.h"
     12 #include "net/base/io_buffer.h"
     13 #include "remoting/base/compound_buffer.h"
     14 
     15 #if defined(USE_SYSTEM_PROTOBUF)
     16 #include <google/protobuf/message_lite.h>
     17 #else
     18 #include "third_party/protobuf/src/google/protobuf/message_lite.h"
     19 #endif
     20 
     21 namespace remoting {
     22 namespace protocol {
     23 
     24 // MessageDecoder uses CompoundBuffer to split the data received from
     25 // the network into separate messages. Each message is expected to be
     26 // decoded in the stream as follows:
     27 //   +--------------+--------------+
     28 //   | message_size | message_data |
     29 //   +--------------+--------------+
     30 //
     31 // Here, message_size is 4-byte integer that represents size of
     32 // message_data in bytes. message_data - content of the message.
     33 class MessageDecoder {
     34  public:
     35   MessageDecoder();
     36   virtual ~MessageDecoder();
     37 
     38   // Add next chunk of data. MessageDecoder retains |data| until all
     39   // its bytes are consumed.
     40   void AddData(scoped_refptr<net::IOBuffer> data, int data_size);
     41 
     42   // Returns next message from the stream. Ownership of the result is
     43   // passed to the caller. Returns NULL if there are no complete
     44   // messages yet, otherwise returns a buffer that contains one
     45   // message.
     46   CompoundBuffer* GetNextMessage();
     47 
     48  private:
     49   // Retrieves the read payload size of the current protocol buffer via |size|.
     50   // Returns false and leaves |size| unmodified, if we do not have enough data
     51   // to retrieve the current size.
     52   bool GetPayloadSize(int* size);
     53 
     54   CompoundBuffer buffer_;
     55 
     56   // |next_payload_| stores the size of the next payload if known.
     57   // |next_payload_known_| is true if the size of the next payload is known.
     58   // After one payload is read this is reset to false.
     59   int next_payload_;
     60   bool next_payload_known_;
     61 };
     62 
     63 }  // namespace protocol
     64 }  // namespace remoting
     65 
     66 #endif  // REMOTING_PROTOCOL_MESSAGE_DECODER_H_
     67