select_reactor.hpp

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  // Remove a timer queue from the reactor.
  template <typename Time_Traits>
  void remove_timer_queue(timer_queue<Time_Traits>& timer_queue)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    for (std::size_t i = 0; i < timer_queues_.size(); ++i)
    {
      if (timer_queues_[i] == &timer_queue)
      {
        timer_queues_.erase(timer_queues_.begin() + i);
        return;
      }
    }
  }

  // Schedule a timer in the given timer queue to expire at the specified
  // absolute time. The handler object will be invoked when the timer expires.
  template <typename Time_Traits, typename Handler>
  void schedule_timer(timer_queue<Time_Traits>& timer_queue,
      const typename Time_Traits::time_type& time, Handler handler, void* token)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    if (!shutdown_)
      if (timer_queue.enqueue_timer(time, handler, token))
        interrupter_.interrupt();
  }

  // Cancel the timer associated with the given token. Returns the number of
  // handlers that have been posted or dispatched.
  template <typename Time_Traits>
  std::size_t cancel_timer(timer_queue<Time_Traits>& timer_queue, void* token)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    std::size_t n = timer_queue.cancel_timer(token);
    if (n > 0)
      interrupter_.interrupt();
    return n;
  }

private:
  friend class task_io_service<select_reactor<Own_Thread> >;

  // Run select once until interrupted or events are ready to be dispatched.
  void run(bool block)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    // Dispatch any operation cancellations that were made while the select
    // loop was not running.
    read_op_queue_.perform_cancellations();
    write_op_queue_.perform_cancellations();
    except_op_queue_.perform_cancellations();
    for (std::size_t i = 0; i < timer_queues_.size(); ++i)
      timer_queues_[i]->dispatch_cancellations();

    // Check if the thread is supposed to stop.
    if (stop_thread_)
    {
      complete_operations_and_timers(lock);
      return;
    }

    // We can return immediately if there's no work to do and the reactor is
    // not supposed to block.
    if (!block && read_op_queue_.empty() && write_op_queue_.empty()
        && except_op_queue_.empty() && all_timer_queues_are_empty())
    {
      complete_operations_and_timers(lock);
      return;
    }

    // Set up the descriptor sets.
    fd_set_adapter read_fds;
    read_fds.set(interrupter_.read_descriptor());
    read_op_queue_.get_descriptors(read_fds);
    fd_set_adapter write_fds;
    write_op_queue_.get_descriptors(write_fds);
    fd_set_adapter except_fds;
    except_op_queue_.get_descriptors(except_fds);
    socket_type max_fd = read_fds.max_descriptor();
    if (write_fds.max_descriptor() > max_fd)
      max_fd = write_fds.max_descriptor();
    if (except_fds.max_descriptor() > max_fd)
      max_fd = except_fds.max_descriptor();

    // Block on the select call without holding the lock so that new
    // operations can be started while the call is executing.
    timeval tv_buf = { 0, 0 };
    timeval* tv = block ? get_timeout(tv_buf) : &tv_buf;
    select_in_progress_ = true;
    lock.unlock();
    boost::system::error_code ec;
    int retval = socket_ops::select(static_cast<int>(max_fd + 1),
        read_fds, write_fds, except_fds, tv, ec);
    lock.lock();
    select_in_progress_ = false;

    // Block signals while dispatching operations.
    boost::asio::detail::signal_blocker sb;

    // Reset the interrupter.
    if (retval > 0 && read_fds.is_set(interrupter_.read_descriptor()))
      interrupter_.reset();

    // Dispatch all ready operations.
    if (retval > 0)
    {
      // Exception operations must be processed first to ensure that any
      // out-of-band data is read before normal data.
      except_op_queue_.perform_operations_for_descriptors(
          except_fds, boost::system::error_code());
      read_op_queue_.perform_operations_for_descriptors(
          read_fds, boost::system::error_code());
      write_op_queue_.perform_operations_for_descriptors(
          write_fds, boost::system::error_code());
      except_op_queue_.perform_cancellations();
      read_op_queue_.perform_cancellations();
      write_op_queue_.perform_cancellations();
    }
    for (std::size_t i = 0; i < timer_queues_.size(); ++i)
    {
      timer_queues_[i]->dispatch_timers();
      timer_queues_[i]->dispatch_cancellations();
    }

    // Issue any pending cancellations.
    for (size_t i = 0; i < pending_cancellations_.size(); ++i)
      cancel_ops_unlocked(pending_cancellations_[i]);
    pending_cancellations_.clear();

    complete_operations_and_timers(lock);
  }

  // Run the select loop in the thread.
  void run_thread()
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    while (!stop_thread_)
    {
      lock.unlock();
      run(true);
      lock.lock();
    }
  }

  // Entry point for the select loop thread.
  static void call_run_thread(select_reactor* reactor)
  {
    reactor->run_thread();
  }

  // Interrupt the select loop.
  void interrupt()
  {
    interrupter_.interrupt();
  }

  // Check if all timer queues are empty.
  bool all_timer_queues_are_empty() const
  {
    for (std::size_t i = 0; i < timer_queues_.size(); ++i)
      if (!timer_queues_[i]->empty())
        return false;
    return true;
  }

  // Get the timeout value for the select call.
  timeval* get_timeout(timeval& tv)
  {
    if (all_timer_queues_are_empty())
      return 0;

    // By default we will wait no longer than 5 minutes. This will ensure that
    // any changes to the system clock are detected after no longer than this.
    boost::posix_time::time_duration minimum_wait_duration
      = boost::posix_time::minutes(5);

    for (std::size_t i = 0; i < timer_queues_.size(); ++i)
    {
      boost::posix_time::time_duration wait_duration
        = timer_queues_[i]->wait_duration();
      if (wait_duration < minimum_wait_duration)
        minimum_wait_duration = wait_duration;
    }

    if (minimum_wait_duration > boost::posix_time::time_duration())
    {
      tv.tv_sec = minimum_wait_duration.total_seconds();
      tv.tv_usec = minimum_wait_duration.total_microseconds() % 1000000;
    }
    else
    {
      tv.tv_sec = 0;
      tv.tv_usec = 0;
    }

    return &tv;
  }

  // Cancel all operations associated with the given descriptor. The do_cancel
  // function of the handler objects will be invoked. This function does not
  // acquire the select_reactor's mutex.
  void cancel_ops_unlocked(socket_type descriptor)
  {
    bool interrupt = read_op_queue_.cancel_operations(descriptor);
    interrupt = write_op_queue_.cancel_operations(descriptor) || interrupt;
    interrupt = except_op_queue_.cancel_operations(descriptor) || interrupt;
    if (interrupt)
      interrupter_.interrupt();
  }

  // Clean up operations and timers. We must not hold the lock since the
  // destructors may make calls back into this reactor. We make a copy of the
  // vector of timer queues since the original may be modified while the lock
  // is not held.
  void complete_operations_and_timers(
      boost::asio::detail::mutex::scoped_lock& lock)
  {
    timer_queues_for_cleanup_ = timer_queues_;
    lock.unlock();
    read_op_queue_.complete_operations();
    write_op_queue_.complete_operations();
    except_op_queue_.complete_operations();
    for (std::size_t i = 0; i < timer_queues_for_cleanup_.size(); ++i)
      timer_queues_for_cleanup_[i]->complete_timers();
  }

  // Mutex to protect access to internal data.
  boost::asio::detail::mutex mutex_;

  // Whether the select loop is currently running or not.
  bool select_in_progress_;

  // The interrupter is used to break a blocking select call.
  select_interrupter interrupter_;

  // The queue of read operations.
  reactor_op_queue<socket_type> read_op_queue_;

  // The queue of write operations.
  reactor_op_queue<socket_type> write_op_queue_;

  // The queue of exception operations.
  reactor_op_queue<socket_type> except_op_queue_;

  // The timer queues.
  std::vector<timer_queue_base*> timer_queues_;

  // A copy of the timer queues, used when cleaning up timers. The copy is
  // stored as a class data member to avoid unnecessary memory allocation.
  std::vector<timer_queue_base*> timer_queues_for_cleanup_;

  // The descriptors that are pending cancellation.
  std::vector<socket_type> pending_cancellations_;

  // Does the reactor loop thread need to stop.
  bool stop_thread_;

  // The thread that is running the reactor loop.
  boost::asio::detail::thread* thread_;

  // Whether the service has been shut down.
  bool shutdown_;
};

} // namespace detail
} // namespace asio
} // namespace boost

#include <boost/asio/detail/pop_options.hpp>

#endif // BOOST_ASIO_DETAIL_SELECT_REACTOR_HPP