Simplified MessageReader and MessageDecoder classes.

remoting/protocol/message_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_PROTOCOL_MESSAGES_DECODER_H_
 #define REMOTING_PROTOCOL_MESSAGES_DECODER_H_
 
 #include <deque>
 #include <list>
 
 #include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
 #include "net/base/io_buffer.h"
 #include "remoting/base/compound_buffer.h"
 #include "third_party/protobuf/src/google/protobuf/message_lite.h"
 
 namespace remoting {
 namespace protocol {
 
-// MessageDecoder uses CompoundBuffer to decode bytes into protocol
-// buffer messages. This can be used to decode bytes received from the
-// network.
+// MessageDecoder uses CompoundBuffer to split the data received from
+// the network into separate messages. Each message is expected to be
+// decoded in the stream as follows:
+//   +--------------+--------------+
+//   | message_size | message_data |
+//   +--------------+--------------+
 //
-// It provides ParseMessages() which accepts an IOBuffer. If enough bytes
-// are collected to produce protocol buffer messages then the bytes will be
-// consumed and the generated protocol buffer messages are added to the output
-// list.
-//
-// It retains ownership of IOBuffer given to this object and keeps it alive
-// until it is full consumed.
+// 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();
 
-  // Parses the bytes in |data| into a protobuf of type MessageType.  The bytes
-  // in |data| are conceptually a stream of bytes to be parsed into a series of
-  // protobufs. Each parsed protouf is appended into the |messages|. All calls
-  // to ParseMessages should use same MessageType for any single instace of
-  // MessageDecoder.
+  // Add next chunk of data. MessageDecoder retains |data| until all
+  // its bytes are consumed.
+  void AddData(scoped_refptr<net::IOBuffer> data, int data_size);
 
-  // This function retains |data| until all its bytes are consumed.
-  // Ownership of the produced protobufs is passed to the caller via the
-  // |messages| list.
-  template <class MessageType>
-  void ParseMessages(scoped_refptr<net::IOBuffer> data,
-                     int data_size, std::list<MessageType*>* messages) {
-    AddBuffer(data, data_size);
+  // Get next message from the stream and puts it in
+  // |message_buffer|. Returns false if there are no complete messages
+  // yet.
+  bool GetNextMessage(CompoundBuffer* message_buffer);
 
-    // Then try to parse the next message until we can't parse anymore.
-    MessageType* message;
-    while (ParseOneMessage<MessageType>(&message)) {
-      messages->push_back(message);
-    }
-  }
-
-  private:
-  // Parse one message from |buffer_list_|. Return true if sucessful.
-  template <class MessageType>
-  bool ParseOneMessage(MessageType** message) {
-    CompoundBuffer buffer;
-    if (!GetNextMessageData(&buffer))
-      return false;
-
-    CompoundBufferInputStream stream(&buffer);
-    *message = new MessageType();
-    bool ret = (*message)->ParseFromZeroCopyStream(&stream);
-    if (!ret)
-      delete *message;
-    return ret;
-  }
-
-  void AddBuffer(scoped_refptr<net::IOBuffer> data, int data_size);
-
-  bool GetNextMessageData(CompoundBuffer* message_buffer);
-
+ 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_MESSAGES_DECODER_H_