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      1 // Copyright 2013 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_CHILD_CROSS_MESSAGE_FILTER_H_
      6 #define CONTENT_CHILD_CROSS_MESSAGE_FILTER_H_
      7 
      8 #include "base/memory/ref_counted.h"
      9 #include "ipc/ipc_sender.h"
     10 
     11 namespace base {
     12 class TaskRunner;
     13 }
     14 
     15 namespace IPC {
     16 class MessageFilter;
     17 }
     18 
     19 namespace content {
     20 
     21 class ThreadSafeSender;
     22 
     23 // A base class for implementing IPC MessageFilter's that run on a different
     24 // thread or TaskRunner than the main thread.
     25 class ChildMessageFilter
     26     : public base::RefCountedThreadSafe<ChildMessageFilter>,
     27       public IPC::Sender {
     28  public:
     29   // IPC::Sender implementation. Can be called on any threads.
     30   virtual bool Send(IPC::Message* message) OVERRIDE;
     31 
     32   // If implementers want to run OnMessageReceived on a different task
     33   // runner it should override this and return the TaskRunner for the message.
     34   // Returning NULL runs OnMessageReceived() on the current IPC thread.
     35   virtual base::TaskRunner* OverrideTaskRunnerForMessage(
     36       const IPC::Message& msg) = 0;
     37 
     38   // If OverrideTaskRunnerForMessage is overriden and returns non-null
     39   // this will be called on the returned TaskRunner.
     40   virtual bool OnMessageReceived(const IPC::Message& msg) = 0;
     41 
     42   // This method is called when WorkerTaskRunner::PostTask() returned false
     43   // for the target thread.  Note that there's still a little chance that
     44   // PostTask() returns true but OnMessageReceived() is never called on the
     45   // target thread.  By default this does nothing.
     46   virtual void OnStaleMessageReceived(const IPC::Message& msg) {}
     47 
     48  protected:
     49   ChildMessageFilter();
     50   virtual ~ChildMessageFilter();
     51 
     52  private:
     53   class Internal;
     54   friend class ChildThread;
     55   friend class RenderThreadImpl;
     56   friend class WorkerThread;
     57 
     58   friend class base::RefCountedThreadSafe<ChildMessageFilter>;
     59 
     60   IPC::MessageFilter* GetFilter();
     61 
     62   // This implements IPC::MessageFilter to hide the actual filter methods from
     63   // child classes.
     64   Internal* internal_;
     65 
     66   scoped_refptr<ThreadSafeSender> thread_safe_sender_;
     67 
     68   DISALLOW_COPY_AND_ASSIGN(ChildMessageFilter);
     69 };
     70 
     71 }  // namespace content
     72 
     73 #endif  // CONTENT_CHILD_CROSS_MESSAGE_FILTER_H_
     74