ipc/ipc_channel_proxy.h

   1 // Copyright (c) 2012 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 IPC_IPC_CHANNEL_PROXY_H_
   6 #define IPC_IPC_CHANNEL_PROXY_H_
   7
   8 #include <vector>
   9
  10 #include "base/memory/ref_counted.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/synchronization/lock.h"
  13 #include "base/threading/non_thread_safe.h"
  14 #include "ipc/ipc_channel.h"
  15 #include "ipc/ipc_channel_handle.h"
  16 #include "ipc/ipc_listener.h"
  17 #include "ipc/ipc_sender.h"
  18
  19 namespace base {
  20 class SingleThreadTaskRunner;
  21 }
  22
  23 namespace IPC {
  24
  25 class ChannelFactory;
  26 class MessageFilter;
  27 class MessageFilterRouter;
  28 class SendCallbackHelper;
  29
  30 //-----------------------------------------------------------------------------
  31 // IPC::ChannelProxy
  32 //
  33 // This class is a helper class that is useful when you wish to run an IPC
  34 // channel on a background thread.  It provides you with the option of either
  35 // handling IPC messages on that background thread or having them dispatched to
  36 // your main thread (the thread on which the IPC::ChannelProxy is created).
  37 //
  38 // The API for an IPC::ChannelProxy is very similar to that of an IPC::Channel.
  39 // When you send a message to an IPC::ChannelProxy, the message is routed to
  40 // the background thread, where it is then passed to the IPC::Channel's Send
  41 // method.  This means that you can send a message from your thread and your
  42 // message will be sent over the IPC channel when possible instead of being
  43 // delayed until your thread returns to its message loop.  (Often IPC messages
  44 // will queue up on the IPC::Channel when there is a lot of traffic, and the
  45 // channel will not get cycles to flush its message queue until the thread, on
  46 // which it is running, returns to its message loop.)
  47 //
  48 // An IPC::ChannelProxy can have a MessageFilter associated with it, which will
  49 // be notified of incoming messages on the IPC::Channel's thread.  This gives
  50 // the consumer of IPC::ChannelProxy the ability to respond to incoming
  51 // messages on this background thread instead of on their own thread, which may
  52 // be bogged down with other processing.  The result can be greatly improved
  53 // latency for messages that can be handled on a background thread.
  54 //
  55 // The consumer of IPC::ChannelProxy is responsible for allocating the Thread
  56 // instance where the IPC::Channel will be created and operated.
  57 //
  58 class IPC_EXPORT ChannelProxy : public Sender, public base::NonThreadSafe {
  59  public:
  60   // Initializes a channel proxy.  The channel_handle and mode parameters are
  61   // passed directly to the underlying IPC::Channel.  The listener is called on
  62   // the thread that creates the ChannelProxy.  The filter's OnMessageReceived
  63   // method is called on the thread where the IPC::Channel is running.  The
  64   // filter may be null if the consumer is not interested in handling messages
  65   // on the background thread.  Any message not handled by the filter will be
  66   // dispatched to the listener.  The given task runner correspond to a thread
  67   // on which IPC::Channel is created and used (e.g. IO thread).
  68   static scoped_ptr<ChannelProxy> Create(
  69       const IPC::ChannelHandle& channel_handle,
  70       Channel::Mode mode,
  71       Listener* listener,
  72       base::SingleThreadTaskRunner* ipc_task_runner);
  73
  74   static scoped_ptr<ChannelProxy> Create(
  75       scoped_ptr<ChannelFactory> factory,
  76       Listener* listener,
  77       base::SingleThreadTaskRunner* ipc_task_runner);
  78
  79   virtual ~ChannelProxy();
  80
  81   // Initializes the channel proxy. Only call this once to initialize a channel
  82   // proxy that was not initialized in its constructor. If create_pipe_now is
  83   // true, the pipe is created synchronously. Otherwise it's created on the IO
  84   // thread.
  85   void Init(const IPC::ChannelHandle& channel_handle, Channel::Mode mode,
  86             bool create_pipe_now);
  87   void Init(scoped_ptr<ChannelFactory> factory, bool create_pipe_now);
  88
  89   // Close the IPC::Channel.  This operation completes asynchronously, once the
  90   // background thread processes the command to close the channel.  It is ok to
  91   // call this method multiple times.  Redundant calls are ignored.
  92   //
  93   // WARNING: MessageFilter objects held by the ChannelProxy is also
  94   // released asynchronously, and it may in fact have its final reference
  95   // released on the background thread.  The caller should be careful to deal
  96   // with / allow for this possibility.
  97   void Close();
  98
  99   // Send a message asynchronously.  The message is routed to the background
 100   // thread where it is passed to the IPC::Channel's Send method.
 101   virtual bool Send(Message* message) OVERRIDE;
 102
 103   // Used to intercept messages as they are received on the background thread.
 104   //
 105   // Ordinarily, messages sent to the ChannelProxy are routed to the matching
 106   // listener on the worker thread.  This API allows code to intercept messages
 107   // before they are sent to the worker thread.
 108   // If you call this before the target process is launched, then you're
 109   // guaranteed to not miss any messages.  But if you call this anytime after,
 110   // then some messages might be missed since the filter is added internally on
 111   // the IO thread.
 112   void AddFilter(MessageFilter* filter);
 113   void RemoveFilter(MessageFilter* filter);
 114
 115   // Called to clear the pointer to the IPC task runner when it's going away.
 116   void ClearIPCTaskRunner();
 117
 118   // Get the process ID for the connected peer.
 119   // Returns base::kNullProcessId if the peer is not connected yet.
 120   base::ProcessId GetPeerPID() const { return context_->peer_pid_; }
 121
 122 #if defined(OS_POSIX) && !defined(OS_NACL)
 123   // Calls through to the underlying channel's methods.
 124   int GetClientFileDescriptor();
 125   int TakeClientFileDescriptor();
 126 #endif  // defined(OS_POSIX)
 127
 128  protected:
 129   class Context;
 130   // A subclass uses this constructor if it needs to add more information
 131   // to the internal state.
 132   ChannelProxy(Context* context);
 133
 134   ChannelProxy(Listener* listener,
 135                base::SingleThreadTaskRunner* ipc_task_runner);
 136
 137   // Used internally to hold state that is referenced on the IPC thread.
 138   class Context : public base::RefCountedThreadSafe<Context>,
 139                   public Listener {
 140    public:
 141     Context(Listener* listener, base::SingleThreadTaskRunner* ipc_thread);
 142     void ClearIPCTaskRunner();
 143     base::SingleThreadTaskRunner* ipc_task_runner() const {
 144       return ipc_task_runner_.get();
 145     }
 146     const std::string& channel_id() const { return channel_id_; }
 147
 148     // Dispatches a message on the listener thread.
 149     void OnDispatchMessage(const Message& message);
 150
 151    protected:
 152     friend class base::RefCountedThreadSafe<Context>;
 153     virtual ~Context();
 154
 155     // IPC::Listener methods:
 156     virtual bool OnMessageReceived(const Message& message) OVERRIDE;
 157     virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;
 158     virtual void OnChannelError() OVERRIDE;
 159
 160     // Like OnMessageReceived but doesn't try the filters.
 161     bool OnMessageReceivedNoFilter(const Message& message);
 162
 163     // Gives the filters a chance at processing |message|.
 164     // Returns true if the message was processed, false otherwise.
 165     bool TryFilters(const Message& message);
 166
 167     // Like Open and Close, but called on the IPC thread.
 168     virtual void OnChannelOpened();
 169     virtual void OnChannelClosed();
 170
 171     // Called on the consumers thread when the ChannelProxy is closed.  At that
 172     // point the consumer is telling us that they don't want to receive any
 173     // more messages, so we honor that wish by forgetting them!
 174     virtual void Clear();
 175
 176    private:
 177     friend class ChannelProxy;
 178     friend class SendCallbackHelper;
 179
 180     // Create the Channel
 181     void CreateChannel(scoped_ptr<ChannelFactory> factory);
 182
 183     // Methods called on the IO thread.
 184     void OnSendMessage(scoped_ptr<Message> message_ptr);
 185     void OnAddFilter();
 186     void OnRemoveFilter(MessageFilter* filter);
 187
 188     // Methods called on the listener thread.
 189     void AddFilter(MessageFilter* filter);
 190     void OnDispatchConnected();
 191     void OnDispatchError();
 192     void OnDispatchBadMessage(const Message& message);
 193
 194     scoped_refptr<base::SingleThreadTaskRunner> listener_task_runner_;
 195     Listener* listener_;
 196
 197     // List of filters.  This is only accessed on the IPC thread.
 198     std::vector<scoped_refptr<MessageFilter> > filters_;
 199     scoped_refptr<base::SingleThreadTaskRunner> ipc_task_runner_;
 200
 201     // Note, channel_ may be set on the Listener thread or the IPC thread.
 202     // But once it has been set, it must only be read or cleared on the IPC
 203     // thread.
 204     scoped_ptr<Channel> channel_;
 205     std::string channel_id_;
 206     bool channel_connected_called_;
 207
 208     // Routes a given message to a proper subset of |filters_|, depending
 209     // on which message classes a filter might support.
 210     scoped_ptr<MessageFilterRouter> message_filter_router_;
 211
 212     // Holds filters between the AddFilter call on the listerner thread and the
 213     // IPC thread when they're added to filters_.
 214     std::vector<scoped_refptr<MessageFilter> > pending_filters_;
 215     // Lock for pending_filters_.
 216     base::Lock pending_filters_lock_;
 217
 218     // Cached copy of the peer process ID. Set on IPC but read on both IPC and
 219     // listener threads.
 220     base::ProcessId peer_pid_;
 221   };
 222
 223   Context* context() { return context_.get(); }
 224
 225  private:
 226   friend class SendCallbackHelper;
 227
 228   // By maintaining this indirection (ref-counted) to our internal state, we
 229   // can safely be destroyed while the background thread continues to do stuff
 230   // that involves this data.
 231   scoped_refptr<Context> context_;
 232
 233   // Whether the channel has been initialized.
 234   bool did_init_;
 235 };
 236
 237 }  // namespace IPC
 238
 239 #endif  // IPC_IPC_CHANNEL_PROXY_H_