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 // 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 CHROME_COMMON_IPC_CHANNEL_PROXY_H__

 #define CHROME_COMMON_IPC_CHANNEL_PROXY_H__

 #include <vector>

 #include "base/lock.h"

 #include "base/ref_counted.h"

 #include "chrome/common/ipc_channel.h"

 class MessageLoop;

 namespace IPC {

 //-----------------------------------------------------------------------------

 // IPC::ChannelProxy

 //

 // This class is a helper class that is useful when you wish to run an IPC

 // channel on a background thread.  It provides you with the option of either

 // handling IPC messages on that background thread or having them dispatched to

 // your main thread (the thread on which the IPC::ChannelProxy is created).

 //

 // The API for an IPC::ChannelProxy is very similar to that of an IPC::Channel.

 // When you send a message to an IPC::ChannelProxy, the message is routed to

 // the background thread, where it is then passed to the IPC::Channel's Send

 // method.  This means that you can send a message from your thread and your

 // message will be sent over the IPC channel when possible instead of being

 // delayed until your thread returns to its message loop.  (Often IPC messages

 // will queue up on the IPC::Channel when there is a lot of traffic, and the

 // channel will not get cycles to flush its message queue until the thread, on

 // which it is running, returns to its message loop.)

 //

 // An IPC::ChannelProxy can have a MessageFilter associated with it, which will

 // be notified of incoming messages on the IPC::Channel's thread.  This gives

 // the consumer of IPC::ChannelProxy the ability to respond to incoming

 // messages on this background thread instead of on their own thread, which may

 // be bogged down with other processing.  The result can be greatly improved

 // latency for messages that can be handled on a background thread.

 //

 // The consumer of IPC::ChannelProxy is responsible for allocating the Thread

 // instance where the IPC::Channel will be created and operated.

 //

 class ChannelProxy : public Message::Sender {

  public:

   // A class that receives messages on the thread where the IPC channel is

   // running.  It can choose to prevent the default action for an IPC message.

   class MessageFilter : public base::RefCountedThreadSafe<MessageFilter> {

    public:

     virtual ~MessageFilter() {}

     // Called on the background thread to provide the filter with access to the

     // channel.  Called when the IPC channel is initialized or when AddFilter

     // is called if the channel is already initialized.

     virtual void OnFilterAdded(Channel* channel) {}

     // Called on the background thread when the filter has been removed from

     // the ChannelProxy and when the Channel is closing.  After a filter is

     // removed, it will not be called again.

     virtual void OnFilterRemoved() {}

     // Called to inform the filter that the IPC channel is connected and we

     // have received the internal Hello message from the peer.

     virtual void OnChannelConnected(int32_t peer_pid) {}

     // Called when there is an error on the channel, typically that the channel

     // has been closed.

     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) {

       return false;

     }

   };

   // 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::wstring& channel_id, Channel::Mode mode,

                Channel::Listener* listener, MessageFilter* filter,

                MessageLoop* ipc_thread_loop);

   ~ChannelProxy() {

     Close();

   }

   // 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.

   void AddFilter(MessageFilter* filter);

   void RemoveFilter(MessageFilter* filter);

 #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.

   void GetClientFileDescriptorMapping(int *src_fd, int *dest_fd) 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::wstring& 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);

     virtual ~Context() { }

     MessageLoop* ipc_message_loop() const { return ipc_message_loop_; }

     const std::wstring& channel_id() const { return channel_id_; }

     // Dispatches a message on the listener thread.

     void OnDispatchMessage(const Message& message);

    protected:

     // IPC::Channel::Listener methods:

     virtual void OnMessageReceived(const Message& message);

     virtual void OnChannelConnected(int32_t peer_pid);

     virtual void OnChannelError();

     // Like OnMessageReceived but doesn't try the filters.

     void OnMessageReceivedNoFilter(const Message& message);

     // Gives the filters a chance at processing |message|.

     // Returns true if the message was processed, false otherwise.

     bool TryFilters(const Message& message);

     // Like Open and Close, but called on the IPC thread.

     virtual void OnChannelOpened();

     virtual void OnChannelClosed();

     // Called on the consumers thread when the ChannelProxy is closed.  At that

     // point the consumer is telling us that they don't want to receive any

     // more messages, so we honor that wish by forgetting them!

     virtual void Clear() { listener_ = NULL; }

    private:

     friend class ChannelProxy;

     // Create the Channel

     void CreateChannel(const std::wstring& id, const Channel::Mode& mode);

     // Methods called via InvokeLater:

     void OnSendMessage(Message* message_ptr);

     void OnAddFilter(MessageFilter* filter);

     void OnRemoveFilter(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::wstring channel_id_;

     int peer_pid_;

     bool channel_connected_called_;

   };

   Context* context() { return context_; }

  private:

   void Init(const std::wstring& 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  // CHROME_COMMON_IPC_CHANNEL_PROXY_H__