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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();
int TakeClientFileDescriptor();
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_