remoting/protocol/message_decoder.h

   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 nullptr 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_