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      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_NACL_H_
      6 #define IPC_IPC_CHANNEL_NACL_H_
      7 
      8 #include <deque>
      9 #include <string>
     10 
     11 #include "base/memory/linked_ptr.h"
     12 #include "base/memory/scoped_ptr.h"
     13 #include "base/memory/weak_ptr.h"
     14 #include "base/process/process.h"
     15 #include "base/threading/simple_thread.h"
     16 #include "ipc/ipc_channel.h"
     17 #include "ipc/ipc_channel_reader.h"
     18 
     19 namespace IPC {
     20 
     21 // Contains the results from one call to imc_recvmsg (data and file
     22 // descriptors).
     23 struct MessageContents;
     24 
     25 // Similar to the Posix version of ChannelImpl but for Native Client code.
     26 // This is somewhat different because sendmsg/recvmsg here do not follow POSIX
     27 // semantics. Instead, they are implemented by a custom embedding of
     28 // NaClDescCustom. See NaClIPCAdapter for the trusted-side implementation.
     29 //
     30 // We don't need to worry about complicated set up and READWRITE mode for
     31 // sharing handles. We also currently do not support passing file descriptors or
     32 // named pipes, and we use background threads to emulate signaling when we can
     33 // read or write without blocking.
     34 class Channel::ChannelImpl : public internal::ChannelReader {
     35  public:
     36   // Mirror methods of Channel, see ipc_channel.h for description.
     37   ChannelImpl(const IPC::ChannelHandle& channel_handle,
     38               Mode mode,
     39               Listener* listener);
     40   virtual ~ChannelImpl();
     41 
     42   // Channel implementation.
     43   bool Connect();
     44   void Close();
     45   bool Send(Message* message);
     46 
     47   // Posted to the main thread by ReaderThreadRunner.
     48   void DidRecvMsg(scoped_ptr<MessageContents> contents);
     49   void ReadDidFail();
     50 
     51  private:
     52   class ReaderThreadRunner;
     53 
     54   bool CreatePipe(const IPC::ChannelHandle& channel_handle);
     55   bool ProcessOutgoingMessages();
     56 
     57   // ChannelReader implementation.
     58   virtual ReadState ReadData(char* buffer,
     59                              int buffer_len,
     60                              int* bytes_read) OVERRIDE;
     61   virtual bool WillDispatchInputMessage(Message* msg) OVERRIDE;
     62   virtual bool DidEmptyInputBuffers() OVERRIDE;
     63   virtual void HandleInternalMessage(const Message& msg) OVERRIDE;
     64 
     65   Mode mode_;
     66   bool waiting_connect_;
     67 
     68   // The pipe used for communication.
     69   int pipe_;
     70 
     71   // The "name" of our pipe.  On Windows this is the global identifier for
     72   // the pipe.  On POSIX it's used as a key in a local map of file descriptors.
     73   // For NaCl, we don't actually support looking up file descriptors by name,
     74   // and it's only used for debug information.
     75   std::string pipe_name_;
     76 
     77   // We use a thread for reading, so that we can simply block on reading and
     78   // post the received data back to the main thread to be properly interleaved
     79   // with other tasks in the MessagePump.
     80   //
     81   // imc_recvmsg supports non-blocking reads, but there's no easy way to be
     82   // informed when a write or read can be done without blocking (this is handled
     83   // by libevent in Posix).
     84   scoped_ptr<ReaderThreadRunner> reader_thread_runner_;
     85   scoped_ptr<base::DelegateSimpleThread> reader_thread_;
     86 
     87   // IPC::ChannelReader expects to be able to call ReadData on us to
     88   // synchronously read data waiting in the pipe's buffer without blocking.
     89   // Since we can't do that (see 1 and 2 above), the reader thread does blocking
     90   // reads and posts the data over to the main thread in MessageContents. Each
     91   // MessageContents object is the result of one call to "imc_recvmsg".
     92   // DidRecvMsg breaks the MessageContents out in to the data and the file
     93   // descriptors, and puts them on these two queues.
     94   // TODO(dmichael): There's probably a more efficient way to emulate this with
     95   //                 a circular buffer or something, so we don't have to do so
     96   //                 many heap allocations. But it maybe isn't worth
     97   //                 the trouble given that we probably want to implement 1 and
     98   //                 2 above in NaCl eventually.
     99   // When ReadData is called, it pulls the bytes out of this queue in order.
    100   std::deque<linked_ptr<std::vector<char> > > read_queue_;
    101   // Queue of file descriptors extracted from imc_recvmsg messages.
    102   // NOTE: The implementation assumes underlying storage here is contiguous, so
    103   // don't change to something like std::deque<> without changing the
    104   // implementation!
    105   std::vector<int> input_fds_;
    106 
    107   // This queue is used when a message is sent prior to Connect having been
    108   // called. Normally after we're connected, the queue is empty.
    109   std::deque<linked_ptr<Message> > output_queue_;
    110 
    111   base::WeakPtrFactory<ChannelImpl> weak_ptr_factory_;
    112 
    113   DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelImpl);
    114 };
    115 
    116 }  // namespace IPC
    117 
    118 #endif  // IPC_IPC_CHANNEL_NACL_H_
    119