content/common/message_router.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 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
  30 namespace content {
  31
  32 class MessageRouter : public IPC::Listener, public IPC::Sender {
  33  public:
  34   MessageRouter();
  35   ~MessageRouter() override;
  36
  37   // Implemented by subclasses to handle control messages
  38   virtual bool OnControlMessageReceived(const IPC::Message& msg);
  39
  40   // IPC::Listener implementation:
  41   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   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_