/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2006-2008 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_COMMON_IPC_CHANNEL_H_
#define CHROME_COMMON_IPC_CHANNEL_H_

#include <cstdint>
#include <queue>
#include "base/basictypes.h"
#include "build/build_config.h"
#include "mozilla/UniquePtr.h"

#ifdef OS_WIN
#  include <string>
#endif

namespace IPC {

class Message;

//------------------------------------------------------------------------------

class Channel {
  // Security tests need access to the pipe handle.
  friend class ChannelTest;

 public:
  // Windows channels use named objects and connect to them by name,
  // but on Unix we use unnamed socketpairs and pass capabilities
  // directly using SCM_RIGHTS messages.  This type abstracts away
  // that difference.
#ifdef OS_WIN
  typedef std::wstring ChannelId;
#else
  struct ChannelId {};
#endif

  // Implemented by consumers of a Channel to receive messages.
  class Listener {
   public:
    virtual ~Listener() {}

    // Called when a message is received.
    virtual void OnMessageReceived(Message&& message) = 0;

    // Called when the channel is connected and we have received the internal
    // Hello message from the peer.
    virtual void OnChannelConnected(int32_t peer_pid) {}

    // Called when an error is detected that causes the channel to close.
    // This method is not called when a channel is closed normally.
    virtual void OnChannelError() {}

    // If the listener has queued messages, swap them for |queue| like so
    //   swap(impl->my_queued_messages, queue);
    virtual void GetQueuedMessages(std::queue<Message>& queue) {}
  };

  enum Mode { MODE_SERVER, MODE_CLIENT };

  enum {
    // The maximum message size in bytes. Attempting to receive a
    // message of this size or bigger results in a channel error.
    kMaximumMessageSize = 256 * 1024 * 1024,

    // Ammount of data to read at once from the pipe.
    kReadBufferSize = 4 * 1024,

    // Maximum size of a message that we allow to be copied (rather than moved).
    kMaxCopySize = 32 * 1024,
  };

  // Initialize a Channel.
  //
  // |channel_id| identifies the communication Channel.
  // |mode| specifies whether this Channel is to operate in server mode or
  // client mode.  In server mode, the Channel is responsible for setting up the
  // IPC object, whereas in client mode, the Channel merely connects to the
  // already established IPC object.
  // |listener| receives a callback on the current thread for each newly
  // received message.
  //
  Channel(const ChannelId& channel_id, Mode mode, Listener* listener);

  // XXX it would nice not to have yet more platform-specific code in
  // here but it's just not worth the trouble.
#if defined(OS_POSIX)
  // Connect to a pre-created channel |fd| as |mode|.
  Channel(int fd, Mode mode, Listener* listener);
#elif defined(OS_WIN)
  // Connect to a pre-created channel as |mode|.  Clients connect to
  // the pre-existing server pipe, and servers take over |server_pipe|.
  Channel(const ChannelId& channel_id, void* server_pipe, Mode mode,
          Listener* listener);
#endif

  ~Channel();

  // Connect the pipe.  On the server side, this will initiate
  // waiting for connections.  On the client, it attempts to
  // connect to a pre-existing pipe.  Note, calling Connect()
  // will not block the calling thread and may complete
  // asynchronously.
  bool Connect();

  // Close this Channel explicitly.  May be called multiple times.
  void Close();

  // Modify the Channel's listener.
  Listener* set_listener(Listener* listener);

  // Send a message over the Channel to the listener on the other end.
  //
  // |message| must be allocated using operator new.  This object will be
  // deleted once the contents of the Message have been sent.
  //
  // If you Send() a message on a Close()'d channel, we delete the message
  // immediately.
  bool Send(mozilla::UniquePtr<Message> message);

  // Unsound_IsClosed() and Unsound_NumQueuedMessages() are safe to call from
  // any thread, but the value returned may be out of date, because we don't
  // use any synchronization when reading or writing it.
  bool Unsound_IsClosed() const;
  uint32_t Unsound_NumQueuedMessages() const;

#if defined(OS_POSIX)
  // On POSIX an IPC::Channel wraps a socketpair(), this method returns the
  // FD # for the client end of the socket and the equivalent FD# to use for
  // mapping it into the Child process.
  // This method may only be called on the server side of a channel.
  //
  // If the kTestingChannelID flag is specified on the command line then
  // a named FIFO is used as the channel transport mechanism rather than a
  // socketpair() in which case this method returns -1 for both parameters.
  void GetClientFileDescriptorMapping(int* src_fd, int* dest_fd) const;

  // Return the file descriptor for communication with the peer.
  int GetFileDescriptor() const;

  // Reset the file descriptor for communication with the peer.
  void ResetFileDescriptor(int fd);

  // Close the client side of the socketpair.
  void CloseClientFileDescriptor();

#elif defined(OS_WIN)
  // Return the server pipe handle.
  void* GetServerPipeHandle() const;
#endif  // defined(OS_POSIX)

  // On Windows: Generates a channel ID that, if passed to the client
  // as a shared secret, will validate the client's authenticity.
  // Other platforms don't use channel IDs, so this returns the dummy
  // ChannelId value.
  static ChannelId GenerateVerifiedChannelID();

  // On Windows: Retrieves the initial channel ID passed to the
  // current process by its parent.  Other platforms don't do this;
  // the dummy ChannelId value is returned instead.
  static ChannelId ChannelIDForCurrentProcess();

#if defined(MOZ_WIDGET_ANDROID)
  // Used to set the first IPC file descriptor in the child process on Android.
  // See ipc_channel_posix.cc for further details on how this is used.
  static void SetClientChannelFd(int fd);
#endif  // defined(MOZ_WIDGET_ANDROID)

 private:
  // PIMPL to which all channel calls are delegated.
  class ChannelImpl;
  ChannelImpl* channel_impl_;

  enum {
#if defined(OS_MACOSX)
    // If the channel receives a message that contains file descriptors, then
    // it will reply back with this message, indicating that the message has
    // been received. The sending channel can then close any descriptors that
    // had been marked as auto_close. This works around a sendmsg() bug on BSD
    // where the kernel can eagerly close file descriptors that are in message
    // queues but not yet delivered.
    RECEIVED_FDS_MESSAGE_TYPE = kuint16max - 1,
#endif

    // The Hello message is internal to the Channel class.  It is sent
    // by the peer when the channel is connected.  The message contains
    // just the process id (pid).  The message has a special routing_id
    // (MSG_ROUTING_NONE) and type (HELLO_MESSAGE_TYPE).
    HELLO_MESSAGE_TYPE = kuint16max  // Maximum value of message type
                                     // (uint16_t), to avoid conflicting with
                                     // normal message types, which are
                                     // enumeration constants starting from 0.
  };
};

}  // namespace IPC

#endif  // CHROME_COMMON_IPC_CHANNEL_H_