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diff --git a/chrome/nacl/nacl_ipc_adapter.h b/chrome/nacl/nacl_ipc_adapter.h
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+// Copyright (c) 2012 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 CHROME_NACL_NACL_IPC_ADAPTER_H_
+#define CHROME_NACL_NACL_IPC_ADAPTER_H_
+#pragma once
+
+#include <queue>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/condition_variable.h"
+#include "base/synchronization/lock.h"
+#include "base/task_runner.h"
+#include "ipc/ipc_channel.h"
+
+// Adapts a Chrome IPC channel to an IPC channel that we expose to Native
+// Client. This provides a mapping in both directions, so when IPC messages
+// come in from another process, we rewrite them and allow them to be received
+// via a recvmsg-like interface in the NaCl code. When NaCl code calls sendmsg,
+// we implement that as sending IPC messages on the channel.
+//
+// This object also provides the necessary logic for rewriting IPC messages.
+// NaCl code is platform-independent and runs in a Posix-like enviroment, but
+// some formatting in the message and the way handles are transferred varies
+// by platform. This class bridges that gap to provide what looks like a
+// normal platform-specific IPC implementation to Chrome, and a Posix-like
+// version on every platform to NaCl.
+//
+// This object must be threadsafe since the nacl environment determines which
+// thread every function is called on.
+class NaClIPCAdapter : public base::RefCountedThreadSafe<NaClIPCAdapter>,
+                       public IPC::Channel::Listener {
+ public:
+  // Chrome's IPC message format varies by platform, NaCl's does not. In
+  // particular, the header has some extra fields on Posix platforms. Since
+  // NaCl is a Posix environment, it gets that version of the header. This
+  // header is duplicated here so we have a cross-platform definition of the
+  // header we're exposing to NaCl.
+#pragma pack(push, 4)
+  struct NaClMessageHeader : public Pickle::Header {
+    int32 routing;
+    uint32 type;
+    uint32 flags;
+    uint16 num_fds;
+    uint16 pad;
+  };
+#pragma pack(pop)
+
+  // Creates an adapter, using the thread associated with the given task
+  // runner for posting messages. In normal use, the task runner will post to
+  // the I/O thread of the process.
+  NaClIPCAdapter(const IPC::ChannelHandle& handle, base::TaskRunner* runner);
+
+  // Initializes with a given channel that's already created for testing
+  // purposes. This function will take ownership of the given channel.
+  NaClIPCAdapter(scoped_ptr<IPC::Channel> channel, base::TaskRunner* runner);
+
+  virtual ~NaClIPCAdapter();
+
+  // Implementation of sendmsg. Returns the number of bytes written or -1 on
+  // failure.
+  int Send(const char* input_data, size_t input_data_len);
+
+  // Implementation of recvmsg. Returns the number of bytes read or -1 on
+  // failure. This will block until there's an error or there is data to
+  // read.
+  int BlockingReceive(char* output_buffer, int output_buffer_size);
+
+  // Closes the IPC channel.
+  void CloseChannel();
+
+  // Listener implementation.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+  virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;
+  virtual void OnChannelError() OVERRIDE;
+
+ private:
+  class RewrittenMessage;
+
+  // This is the data that must only be accessed inside the lock. This struct
+  // just separates it so it's easier to see.
+  struct LockedData {
+    LockedData();
+    ~LockedData();
+
+    // Messages that we have read off of the Chrome IPC channel that are waiting
+    // to be received by the plugin.
+    std::queue< scoped_refptr<RewrittenMessage> > to_be_received_;
+
+    // Data that we've queued from the plugin to send, but doesn't consist of a
+    // full message yet. The calling code can break apart the message into
+    // smaller pieces, and we need to send the message to the other process in
+    // one chunk.
+    //
+    // The IPC channel always starts a new send() at the beginning of each
+    // message, so we don't need to worry about arbitrary message boundaries.
+    std::string to_be_sent_;
+
+    bool channel_closed_;
+  };
+
+  // This is the data that must only be accessed on the I/O thread (as defined
+  // by TaskRunner). This struct just separates it so it's easier to see.
+  struct IOThreadData {
+    IOThreadData();
+    ~IOThreadData();
+
+    scoped_ptr<IPC::Channel> channel_;
+  };
+
+  // Reads up to the given amount of data. Returns 0 if nothing is waiting.
+  int LockedReceive(char* output_buffer, int output_buffer_size);
+
+  // Sends a message that we know has been completed to the Chrome process.
+  bool SendCompleteMessage(const char* buffer, size_t buffer_len);
+
+  // Clears the LockedData.to_be_sent_ structure in a way to make sure that
+  // the memory is deleted. std::string can sometimes hold onto the buffer
+  // for future use which we don't want.
+  void ClearToBeSent();
+
+  void CloseChannelOnIOThread();
+  void SendMessageOnIOThread(scoped_ptr<IPC::Message> message);
+
+  base::Lock lock_;
+  base::ConditionVariable cond_var_;
+
+  scoped_refptr<base::TaskRunner> task_runner_;
+
+  // To be accessed inside of lock_ only.
+  LockedData locked_data_;
+
+  // To be accessed on the I/O thread (via task runner) only.
+  IOThreadData io_thread_data_;
+
+  DISALLOW_COPY_AND_ASSIGN(NaClIPCAdapter);
+};
+
+#endif  // CHROME_NACL_NACL_IPC_ADAPTER_H_