Allow MessageFilters to restrict listening to specific message classes

ipc/ipc_channel_proxy.h

 // Copyright (c) 2012 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 IPC_IPC_CHANNEL_PROXY_H_
 #define IPC_IPC_CHANNEL_PROXY_H_
 
 #include <vector>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/non_thread_safe.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_listener.h"
+#include "ipc/ipc_message_start.h"
 #include "ipc/ipc_sender.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace IPC {
 
 class SendCallbackHelper;
 
@@ skipping 54 matching lines @@
     virtual void OnChannelError();
 
     // Called to inform the filter that the IPC channel will be destroyed.
     // OnFilterRemoved is called immediately after this.
     virtual void OnChannelClosing();
 
     // Return true to indicate that the message was handled, or false to let
     // the message be handled in the default way.
     virtual bool OnMessageReceived(const Message& message);
 
+    // Called to query the Message classes supported by the filter.  Return
+    // false to indicate that all message types should reach the filter, or true
+    // if the resulting contents of |supported_message_classes| may be used to
+    // selectively offer messages of a particular class to the filter.
+    virtual bool GetSupportedMessageClasses(
+        std::vector<uint32>* supported_message_classes) const;
+
    protected:
     virtual ~MessageFilter();
 
    private:
     friend class base::RefCountedThreadSafe<MessageFilter>;
   };
 
   // Initializes a channel proxy.  The channel_handle and mode parameters are
   // passed directly to the underlying IPC::Channel.  The listener is called on
   // the thread that creates the ChannelProxy.  The filter's OnMessageReceived
@@ skipping 116 matching lines @@
 
     // Methods called on the listener thread.
     void AddFilter(MessageFilter* filter);
     void OnDispatchConnected();
     void OnDispatchError();
 
     scoped_refptr<base::SingleThreadTaskRunner> listener_task_runner_;
     Listener* listener_;
 
     // List of filters.  This is only accessed on the IPC thread.
-    std::vector<scoped_refptr<MessageFilter> > filters_;
+    std::vector<scoped_refptr<MessageFilter> > all_filters_;
     scoped_refptr<base::SingleThreadTaskRunner> ipc_task_runner_;
     scoped_ptr<Channel> channel_;
     std::string channel_id_;
     bool channel_connected_called_;
 
+    // List of global and selective filters; a given filter from |all_filters_|
+    // will exists in either |message_global_filters_| OR
+    // |message_class_filters_|, but not both.
+    // Note that |message_global_filters_| will be given first offering of any
+    // given message.  It's the filter implementer and installer's
+    // responsibility to ensure that a filter is either global or selective to
+    // ensure proper message filtering order.
+    std::vector<MessageFilter*> message_global_filters_;
+    std::vector<MessageFilter*> message_class_filters_[LastIPCMsgStart];
+
     // Holds filters between the AddFilter call on the listerner thread and the
     // IPC thread when they're added to filters_.
     std::vector<scoped_refptr<MessageFilter> > pending_filters_;
     // Lock for pending_filters_.
     base::Lock pending_filters_lock_;
 
     // Cached copy of the peer process ID. Set on IPC but read on both IPC and
     // listener threads.
     base::ProcessId peer_pid_;
   };
 
   Context* context() { return context_.get(); }
 
  private:
   friend class SendCallbackHelper;
 
   // By maintaining this indirection (ref-counted) to our internal state, we
   // can safely be destroyed while the background thread continues to do stuff
   // that involves this data.
   scoped_refptr<Context> context_;
 
   // Whether the channel has been initialized.
   bool did_init_;
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_PROXY_H_