HostMessageDispatcher to parse control messages

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 "google/protobuf/message_lite.h"
+
+namespace net {
+class DrainableIOBuffer;
+class IOBuffer;
+}  // namespace net
+
+namespace remoting {
+
+class ChromotingClientMessage;
+class ChromotingHostMessage;
+class ClientControlMessage;
+class ClientEventMessage;
+class HostControlMessage;
+class HostEventMessage;
+class MultipleArrayInputStream;
+
+// MessageDecoder uses MultipleArrayInputStream to decode bytes into
+// protocol buffer messages. This can be used to decode bytes received from
+// the network.
+//
+// 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.
+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.
+
+  // 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);
+
+    // Then try to parse the next message until we can't parse anymore.
+    MessageType* message;
+    while (ParseOneMessage<MessageType>(&message)) {
+      messages->push_back(message);
+    }
+  }
+
+  private:
+  // TODO(sergeyu): It might be more efficient to memcopy data to one big buffer
+  // instead of storing chunks in dqueue.
+  typedef std::deque<scoped_refptr<net::DrainableIOBuffer> > BufferList;
+
+  // Parse one message from |buffer_list_|. Return true if sucessful.
+  template <class MessageType>
+  bool ParseOneMessage(MessageType** message) {
+    scoped_ptr<MultipleArrayInputStream> stream(CreateInputStreamFromData());
+    if (!stream.get())
+      return false;
+
+    *message = new MessageType();
+    bool ret = (*message)->ParseFromZeroCopyStream(stream.get());
+    if (!ret) {
+      delete *message;
+    }
+    return ret;
+  }
+
+  void AddBuffer(scoped_refptr<net::IOBuffer> data, int data_size);
+
+  MultipleArrayInputStream* CreateInputStreamFromData();
+
+  // 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);
+
+  BufferList buffer_list_;
+
+  // The number of bytes in |buffer_list_| not consumed.
+  int available_bytes_;
+
+  // |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 remoting
+
+#endif  // REMOTING_PROTOCOL_MESSAGES_DECODER_H_