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 CONTENT_COMMON_MESSAGE_ROUTER_H_
6#define CONTENT_COMMON_MESSAGE_ROUTER_H_
7
8#include "base/id_map.h"
9#include "ipc/ipc_listener.h"
10#include "ipc/ipc_sender.h"
11
12// The MessageRouter handles all incoming messages sent to it by routing them
13// to the correct listener.  Routing is based on the Message's routing ID.
14// Since routing IDs are typically assigned asynchronously by the browser
15// process, the MessageRouter has the notion of pending IDs for listeners that
16// have not yet been assigned a routing ID.
17//
18// When a message arrives, the routing ID is used to index the set of routes to
19// find a listener.  If a listener is found, then the message is passed to it.
20// Otherwise, the message is ignored if its routing ID is not equal to
21// MSG_ROUTING_CONTROL.
22//
23// The MessageRouter supports the IPC::Sender interface for outgoing messages,
24// but does not define a meaningful implementation of it.  The subclass of
25// MessageRouter is intended to provide that if appropriate.
26//
27// The MessageRouter can be used as a concrete class provided its Send method
28// is not called and it does not receive any control messages.
29
30namespace content {
31
32class MessageRouter : public IPC::Listener, public IPC::Sender {
33 public:
34  MessageRouter();
35  virtual ~MessageRouter();
36
37  // Implemented by subclasses to handle control messages
38  virtual bool OnControlMessageReceived(const IPC::Message& msg);
39
40  // IPC::Listener implementation:
41  virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
42
43  // Like OnMessageReceived, except it only handles routed messages.  Returns
44  // true if the message was dispatched, or false if there was no listener for
45  // that route id.
46  virtual bool RouteMessage(const IPC::Message& msg);
47
48  // IPC::Sender implementation:
49  virtual bool Send(IPC::Message* msg) OVERRIDE;
50
51  // Called to add a listener for a particular message routing ID.
52  // Returns true if succeeded.
53  bool AddRoute(int32 routing_id, IPC::Listener* listener);
54
55  // Called to remove a listener for a particular message routing ID.
56  void RemoveRoute(int32 routing_id);
57
58 private:
59  // A list of all listeners with assigned routing IDs.
60  IDMap<IPC::Listener> routes_;
61
62  DISALLOW_COPY_AND_ASSIGN(MessageRouter);
63};
64
65}  // namespace content
66
67#endif  // CONTENT_COMMON_MESSAGE_ROUTER_H_
68