1 files changed, 63 insertions, 0 deletions
diff --git a/content/common/message_router.h b/content/common/message_router.h
new file mode 100644
index 0000000..cb97f3f
--- /dev/null
+++ b/content/common/message_router.h
@@ -0,0 +1,63 @@
+// Copyright (c) 2011 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 CONTENT_COMMON_MESSAGE_ROUTER_H_
+#define CONTENT_COMMON_MESSAGE_ROUTER_H_
+#pragma once
+
+#include "base/id_map.h"
+#include "ipc/ipc_channel.h"
+
+// The MessageRouter handles all incoming messages sent to it by routing them
+// to the correct listener.  Routing is based on the Message's routing ID.
+// Since routing IDs are typically assigned asynchronously by the browser
+// process, the MessageRouter has the notion of pending IDs for listeners that
+// have not yet been assigned a routing ID.
+//
+// When a message arrives, the routing ID is used to index the set of routes to
+// find a listener.  If a listener is found, then the message is passed to it.
+// Otherwise, the message is ignored if its routing ID is not equal to
+// MSG_ROUTING_CONTROL.
+//
+// The MessageRouter supports the IPC::Message::Sender interface for outgoing
+// messages, but does not define a meaningful implementation of it.  The
+// subclass of MessageRouter is intended to provide that if appropriate.
+//
+// The MessageRouter can be used as a concrete class provided its Send method
+// is not called and it does not receive any control messages.
+
+class MessageRouter : public IPC::Channel::Listener,
+                      public IPC::Message::Sender {
+ public:
+  MessageRouter();
+  virtual ~MessageRouter();
+
+  // Implemented by subclasses to handle control messages
+  virtual bool OnControlMessageReceived(const IPC::Message& msg);
+
+  // IPC::Channel::Listener implementation:
+  virtual bool OnMessageReceived(const IPC::Message& msg);
+
+  // Like OnMessageReceived, except it only handles routed messages.  Returns
+  // true if the message was dispatched, or false if there was no listener for
+  // that route id.
+  virtual bool RouteMessage(const IPC::Message& msg);
+
+  // IPC::Message::Sender implementation:
+  virtual bool Send(IPC::Message* msg);
+
+  // Called to add/remove a listener for a particular message routing ID.
+  void AddRoute(int32 routing_id, IPC::Channel::Listener* listener);
+  void RemoveRoute(int32 routing_id);
+
+  IPC::Channel::Listener* ResolveRoute(int32 routing_id);
+
+ private:
+  // A list of all listeners with assigned routing IDs.
+  IDMap<IPC::Channel::Listener> routes_;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageRouter);
+};
+
+#endif  // CONTENT_COMMON_MESSAGE_ROUTER_H_