Separates ipc code from common (http://crbug.com/16829)

chrome/common/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 CHROME_COMMON_IPC_CHANNEL_PROXY_H__
-#define CHROME_COMMON_IPC_CHANNEL_PROXY_H__
-
-#include <vector>
-
-#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 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::string& 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.
-  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,
-               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::string& 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 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::string& 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::string channel_id_;
-    int peer_pid_;
-    bool channel_connected_called_;
-  };
-
-  Context* context() { return context_; }
-
- private:
-  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  // CHROME_COMMON_IPC_CHANNEL_PROXY_H__