Add a base class for objects that want to filter messages on the UI thread. ...

ipc/ipc_channel_proxy.h

 // Copyright (c) 2006-2008 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__
 #pragma once
 
 #include <vector>
 
+#include "base/lock.h"
 #include "base/ref_counted.h"
 #include "ipc/ipc_channel.h"
 
 class MessageLoop;
 
 namespace IPC {
 
 class SendTask;
 
 //-----------------------------------------------------------------------------
@@ skipping 76 matching lines @@
   };
 
   // Initializes a channel proxy.  The channel_id 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
   // method is called on the thread where the IPC::Channel is running.  The
   // filter may be null if the consumer is not interested in handling messages
   // on the background thread.  Any message not handled by the filter will be
   // dispatched to the listener.  The given message loop indicates where the
   // IPC::Channel should be created.
-  ChannelProxy(const std::string& channel_id, Channel::Mode mode,
-               Channel::Listener* listener, MessageFilter* filter,
+  ChannelProxy(const std::string& channel_id,
+               Channel::Mode mode,
+               Channel::Listener* listener,
                MessageLoop* ipc_thread_loop);
 
   virtual ~ChannelProxy();
 
   // Close the IPC::Channel.  This operation completes asynchronously, once the
   // background thread processes the command to close the channel.  It is ok to
   // call this method multiple times.  Redundant calls are ignored.
   //
   // WARNING: The MessageFilter object held by the ChannelProxy is also
   // released asynchronously, and it may in fact have its final reference
   // released on the background thread.  The caller should be careful to deal
   // with / allow for this possibility.
   void Close();
 
   // Send a message asynchronously.  The message is routed to the background
   // thread where it is passed to the IPC::Channel's Send method.
   virtual bool Send(Message* message);
 
   // Used to intercept messages as they are received on the background thread.
   //
   // Ordinarily, messages sent to the ChannelProxy are routed to the matching
   // listener on the worker thread.  This API allows code to intercept messages
   // before they are sent to the worker thread.
+  // If you call this before the target process is launched, then you're
+  // guaranteed to not miss any messages.  But if you call this anytime after,
+  // then some messages might be missed since the filter is added internally on
+  // internally on the IO thread.
   void AddFilter(MessageFilter* filter);
   void RemoveFilter(MessageFilter* filter);
 
   // Called to clear the pointer to the IPC message loop when it's going away.
   void ClearIPCMessageLoop();
 
 #if defined(OS_POSIX)
   // Calls through to the underlying channel's methods.
   // TODO(playmobil): For now this is only implemented in the case of
   // create_pipe_now = true, we need to figure this out for the latter case.
   int GetClientFileDescriptor() const;
 #endif  // defined(OS_POSIX)
 
  protected:
   class Context;
   // A subclass uses this constructor if it needs to add more information
   // to the internal state.  If create_pipe_now is true, the pipe is created
   // immediately.  Otherwise it's created on the IO thread.
-  ChannelProxy(const std::string& channel_id, Channel::Mode mode,
-               MessageLoop* ipc_thread_loop, Context* context,
+  ChannelProxy(const std::string& channel_id,
+               Channel::Mode mode,
+               MessageLoop* ipc_thread_loop,
+               Context* context,
                bool create_pipe_now);
 
   // Used internally to hold state that is referenced on the IPC thread.
   class Context : public base::RefCountedThreadSafe<Context>,
                   public Channel::Listener {
    public:
-    Context(Channel::Listener* listener, MessageFilter* filter,
-            MessageLoop* ipc_thread);
+    Context(Channel::Listener* listener, MessageLoop* ipc_thread);
     void ClearIPCMessageLoop() { ipc_message_loop_ = NULL; }
     MessageLoop* ipc_message_loop() const { return ipc_message_loop_; }
     const std::string& channel_id() const { return channel_id_; }
 
     // Dispatches a message on the listener thread.
     void OnDispatchMessage(const Message& message);
 
    protected:
     friend class base::RefCountedThreadSafe<Context>;
     virtual ~Context() { }
@@ skipping 19 matching lines @@
     // more messages, so we honor that wish by forgetting them!
     virtual void Clear() { listener_ = NULL; }
 
    private:
     friend class ChannelProxy;
     friend class SendTask;
 
     // Create the Channel
     void CreateChannel(const std::string& id, const Channel::Mode& mode);
 
-    // Methods called via InvokeLater:
+    // Methods called on the IO thread.
     void OnSendMessage(Message* message_ptr);
-    void OnAddFilter(MessageFilter* filter);
+    void OnAddFilter();
     void OnRemoveFilter(MessageFilter* filter);
+
+    // Methods called on the listener thread.
+    void AddFilter(MessageFilter* filter);
     void OnDispatchConnected();
     void OnDispatchError();
 
     MessageLoop* listener_message_loop_;
     Channel::Listener* listener_;
 
     // List of filters.  This is only accessed on the IPC thread.
     std::vector<scoped_refptr<MessageFilter> > filters_;
     MessageLoop* ipc_message_loop_;
     Channel* channel_;
     std::string channel_id_;
     int peer_pid_;
     bool channel_connected_called_;
+
+    // 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_.
+    Lock pending_filters_lock_;
   };
 
   Context* context() { return context_; }
 
  private:
   friend class SendTask;
 
   void Init(const std::string& channel_id, Channel::Mode mode,
             MessageLoop* ipc_thread_loop, bool create_pipe_now);
 
   // 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_;
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_PROXY_H__