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+// Copyright (c) 2011 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/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop_proxy.h"
+#include "base/synchronization/lock.h"
+#include "ipc/ipc_channel.h"
+#include "ipc/ipc_channel_handle.h"
+
+namespace IPC {
+
+class SendTask;
+
+//-----------------------------------------------------------------------------
+// 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 IPC_EXPORT ChannelProxy : public Message::Sender {
+ public:
+
+ struct MessageFilterTraits;
+
+ // 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 IPC_EXPORT MessageFilter
+ : public base::RefCountedThreadSafe<MessageFilter, MessageFilterTraits> {
+ public:
+ MessageFilter();
+ 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);
+
+ // Called when the message filter is about to be deleted. This gives
+ // derived classes the option of controlling which thread they're deleted
+ // on etc.
+ virtual void OnDestruct() const;
+ };
+
+ struct MessageFilterTraits {
+ static void Destruct(const MessageFilter* filter) {
+ filter->OnDestruct();
+ }
+ };
+
+ // Interface for a filter to be imposed on outgoing messages which can
+ // re-write the message. Used mainly for testing.
+ class OutgoingMessageFilter {
+ public:
+ // Returns a re-written message, freeing the original, or simply the
+ // original unchanged if no rewrite indicated.
+ virtual Message *Rewrite(Message *message) = 0;
+ };
+
+ // 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
+ // 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 IPC::ChannelHandle& channel_handle,
+ Channel::Mode mode,
+ Channel::Listener* listener,
+ base::MessageLoopProxy* 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
+ // the IO thread.
+ void AddFilter(MessageFilter* filter);
+ void RemoveFilter(MessageFilter* filter);
+
+ void set_outgoing_message_filter(OutgoingMessageFilter* filter) {
+ outgoing_message_filter_ = 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.
+ int GetClientFileDescriptor() const;
+ bool GetClientEuid(uid_t* client_euid) 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 IPC::ChannelHandle& channel_handle,
+ Channel::Mode mode,
+ base::MessageLoopProxy* 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, base::MessageLoopProxy* ipc_thread);
+ void ClearIPCMessageLoop() { ipc_message_loop_ = NULL; }
+ base::MessageLoopProxy* ipc_message_loop() const {
+ return ipc_message_loop_.get();
+ }
+ 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();
+
+ // IPC::Channel::Listener methods:
+ virtual bool OnMessageReceived(const Message& message) OVERRIDE;
+ virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;
+ virtual void OnChannelError() OVERRIDE;
+
+ // Like OnMessageReceived but doesn't try the filters.
+ bool 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;
+ friend class SendTask;
+
+ // Create the Channel
+ void CreateChannel(const IPC::ChannelHandle& channel_handle,
+ const Channel::Mode& mode);
+
+ // Methods called on the IO thread.
+ void OnSendMessage(Message* message_ptr);
+ void OnAddFilter();
+ void OnRemoveFilter(MessageFilter* filter);
+
+ // Methods called on the listener thread.
+ void AddFilter(MessageFilter* filter);
+ void OnDispatchConnected();
+ void OnDispatchError();
+
+ scoped_refptr<base::MessageLoopProxy> listener_message_loop_;
+ Channel::Listener* listener_;
+
+ // List of filters. This is only accessed on the IPC thread.
+ std::vector<scoped_refptr<MessageFilter> > filters_;
+ scoped_refptr<base::MessageLoopProxy> ipc_message_loop_;
+ scoped_ptr<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_.
+ base::Lock pending_filters_lock_;
+ };
+
+ Context* context() { return context_; }
+
+ OutgoingMessageFilter* outgoing_message_filter() {
+ return outgoing_message_filter_;
+ }
+
+ private:
+ friend class SendTask;
+
+ void Init(const IPC::ChannelHandle& channel_handle, Channel::Mode mode,
+ base::MessageLoopProxy* 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_;
+
+ OutgoingMessageFilter* outgoing_message_filter_;
+};
+
+} // namespace IPC
+
+#endif // IPC_IPC_CHANNEL_PROXY_H_