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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 ChannelPosix 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 ChannelNacl : public Channel,
     35                     public internal::ChannelReader {
     36  public:
     37   // Mirror methods of Channel, see ipc_channel.h for description.
     38   ChannelNacl(const IPC::ChannelHandle& channel_handle,
     39               Mode mode,
     40               Listener* listener);
     41   virtual ~ChannelNacl();
     42 
     43   // Channel implementation.
     44   virtual base::ProcessId GetPeerPID() const OVERRIDE;
     45   virtual base::ProcessId GetSelfPID() const OVERRIDE;
     46   virtual bool Connect() OVERRIDE;
     47   virtual void Close() OVERRIDE;
     48   virtual bool Send(Message* message) OVERRIDE;
     49 
     50   // Posted to the main thread by ReaderThreadRunner.
     51   void DidRecvMsg(scoped_ptr<MessageContents> contents);
     52   void ReadDidFail();
     53 
     54  private:
     55   class ReaderThreadRunner;
     56 
     57   bool CreatePipe(const IPC::ChannelHandle& channel_handle);
     58   bool ProcessOutgoingMessages();
     59   void CallOnChannelConnected();
     60 
     61   // ChannelReader implementation.
     62   virtual ReadState ReadData(char* buffer,
     63                              int buffer_len,
     64                              int* bytes_read) OVERRIDE;
     65   virtual bool WillDispatchInputMessage(Message* msg) OVERRIDE;
     66   virtual bool DidEmptyInputBuffers() OVERRIDE;
     67   virtual void HandleInternalMessage(const Message& msg) OVERRIDE;
     68 
     69   Mode mode_;
     70   bool waiting_connect_;
     71 
     72   // The pipe used for communication.
     73   int pipe_;
     74 
     75   // The "name" of our pipe.  On Windows this is the global identifier for
     76   // the pipe.  On POSIX it's used as a key in a local map of file descriptors.
     77   // For NaCl, we don't actually support looking up file descriptors by name,
     78   // and it's only used for debug information.
     79   std::string pipe_name_;
     80 
     81   // We use a thread for reading, so that we can simply block on reading and
     82   // post the received data back to the main thread to be properly interleaved
     83   // with other tasks in the MessagePump.
     84   //
     85   // imc_recvmsg supports non-blocking reads, but there's no easy way to be
     86   // informed when a write or read can be done without blocking (this is handled
     87   // by libevent in Posix).
     88   scoped_ptr<ReaderThreadRunner> reader_thread_runner_;
     89   scoped_ptr<base::DelegateSimpleThread> reader_thread_;
     90 
     91   // IPC::ChannelReader expects to be able to call ReadData on us to
     92   // synchronously read data waiting in the pipe's buffer without blocking.
     93   // Since we can't do that (see 1 and 2 above), the reader thread does blocking
     94   // reads and posts the data over to the main thread in MessageContents. Each
     95   // MessageContents object is the result of one call to "imc_recvmsg".
     96   // DidRecvMsg breaks the MessageContents out in to the data and the file
     97   // descriptors, and puts them on these two queues.
     98   // TODO(dmichael): There's probably a more efficient way to emulate this with
     99   //                 a circular buffer or something, so we don't have to do so
    100   //                 many heap allocations. But it maybe isn't worth
    101   //                 the trouble given that we probably want to implement 1 and
    102   //                 2 above in NaCl eventually.
    103   // When ReadData is called, it pulls the bytes out of this queue in order.
    104   std::deque<linked_ptr<std::vector<char> > > read_queue_;
    105   // Queue of file descriptors extracted from imc_recvmsg messages.
    106   // NOTE: The implementation assumes underlying storage here is contiguous, so
    107   // don't change to something like std::deque<> without changing the
    108   // implementation!
    109   std::vector<int> input_fds_;
    110 
    111   // This queue is used when a message is sent prior to Connect having been
    112   // called. Normally after we're connected, the queue is empty.
    113   std::deque<linked_ptr<Message> > output_queue_;
    114 
    115   base::WeakPtrFactory<ChannelNacl> weak_ptr_factory_;
    116 
    117   DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelNacl);
    118 };
    119 
    120 }  // namespace IPC
    121 
    122 #endif  // IPC_IPC_CHANNEL_NACL_H_
    123