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