dev_poll_reactor.hpp

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      cleanup_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())
    {
      cleanup_operations_and_timers(lock);
      return;
    }

    // Write the pending event registration changes to the /dev/poll descriptor.
    std::size_t events_size = sizeof(::pollfd) * pending_event_changes_.size();
    errno = 0;
    int result = ::write(dev_poll_fd_,
        &pending_event_changes_[0], events_size);
    if (result != static_cast<int>(events_size))
    {
      for (std::size_t i = 0; i < pending_event_changes_.size(); ++i)
      {
        int descriptor = pending_event_changes_[i].fd;
        asio::error_code ec = asio::error_code(
            errno, asio::error::get_system_category());
        read_op_queue_.dispatch_all_operations(descriptor, ec);
        write_op_queue_.dispatch_all_operations(descriptor, ec);
        except_op_queue_.dispatch_all_operations(descriptor, ec);
      }
    }
    pending_event_changes_.clear();
    pending_event_change_index_.clear();

    int timeout = block ? get_timeout() : 0;
    wait_in_progress_ = true;
    lock.unlock();

    // Block on the /dev/poll descriptor.
    ::pollfd events[128] = { { 0 } };
    ::dvpoll dp = { 0 };
    dp.dp_fds = events;
    dp.dp_nfds = 128;
    dp.dp_timeout = timeout;
    int num_events = ::ioctl(dev_poll_fd_, DP_POLL, &dp);

    lock.lock();
    wait_in_progress_ = false;

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

    // Dispatch the waiting events.
    for (int i = 0; i < num_events; ++i)
    {
      int descriptor = events[i].fd;
      if (descriptor == interrupter_.read_descriptor())
      {
        interrupter_.reset();
      }
      else
      {
        bool more_reads = false;
        bool more_writes = false;
        bool more_except = false;
        asio::error_code ec;

        // Exception operations must be processed first to ensure that any
        // out-of-band data is read before normal data.
        if (events[i].events & (POLLPRI | POLLERR | POLLHUP))
          more_except = except_op_queue_.dispatch_operation(descriptor, ec);
        else
          more_except = except_op_queue_.has_operation(descriptor);

        if (events[i].events & (POLLIN | POLLERR | POLLHUP))
          more_reads = read_op_queue_.dispatch_operation(descriptor, ec);
        else
          more_reads = read_op_queue_.has_operation(descriptor);

        if (events[i].events & (POLLOUT | POLLERR | POLLHUP))
          more_writes = write_op_queue_.dispatch_operation(descriptor, ec);
        else
          more_writes = write_op_queue_.has_operation(descriptor);

        if ((events[i].events == POLLHUP)
            && !more_except && !more_reads && !more_writes)
        {
          // If we have only an POLLHUP event and no operations associated
          // with the descriptor then we need to delete the descriptor from
          // /dev/poll. The poll operation might produce POLLHUP events even
          // if they are not specifically requested, so if we do not remove the
          // descriptor we can end up in a tight polling loop.
          ::pollfd ev = { 0 };
          ev.fd = descriptor;
          ev.events = POLLREMOVE;
          ev.revents = 0;
          ::write(dev_poll_fd_, &ev, sizeof(ev));
        }
        else
        {
          ::pollfd ev = { 0 };
          ev.fd = descriptor;
          ev.events = POLLERR | POLLHUP;
          if (more_reads)
            ev.events |= POLLIN;
          if (more_writes)
            ev.events |= POLLOUT;
          if (more_except)
            ev.events |= POLLPRI;
          ev.revents = 0;
          int result = ::write(dev_poll_fd_, &ev, sizeof(ev));
          if (result != sizeof(ev))
          {
            ec = asio::error_code(errno,
                asio::error::get_system_category());
            read_op_queue_.dispatch_all_operations(descriptor, ec);
            write_op_queue_.dispatch_all_operations(descriptor, ec);
            except_op_queue_.dispatch_all_operations(descriptor, ec);
          }
        }
      }
    }
    read_op_queue_.dispatch_cancellations();
    write_op_queue_.dispatch_cancellations();
    except_op_queue_.dispatch_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();

    cleanup_operations_and_timers(lock);
  }

  // Run the select loop in the thread.
  void run_thread()
  {
    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(dev_poll_reactor* reactor)
  {
    reactor->run_thread();
  }

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

  // Create the /dev/poll file descriptor. Throws an exception if the descriptor
  // cannot be created.
  static int do_dev_poll_create()
  {
    int fd = ::open("/dev/poll", O_RDWR);
    if (fd == -1)
    {
      boost::throw_exception(
          asio::system_error(
            asio::error_code(errno,
              asio::error::get_system_category()),
            "/dev/poll"));
    }
    return fd;
  }

  // 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 /dev/poll DP_POLL operation. The timeout
  // value is returned as a number of milliseconds. A return value of -1
  // indicates that the poll should block indefinitely.
  int get_timeout()
  {
    if (all_timer_queues_are_empty())
      return -1;

    // 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())
    {
      int milliseconds = minimum_wait_duration.total_milliseconds();
      return milliseconds > 0 ? milliseconds : 1;
    }
    else
    {
      return 0;
    }
  }

  // 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 dev_poll_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 cleanup_operations_and_timers(
      asio::detail::mutex::scoped_lock& lock)
  {
    timer_queues_for_cleanup_ = timer_queues_;
    lock.unlock();
    read_op_queue_.cleanup_operations();
    write_op_queue_.cleanup_operations();
    except_op_queue_.cleanup_operations();
    for (std::size_t i = 0; i < timer_queues_for_cleanup_.size(); ++i)
      timer_queues_for_cleanup_[i]->cleanup_timers();
  }

  // Add a pending event entry for the given descriptor.
  ::pollfd& add_pending_event_change(int descriptor)
  {
    hash_map<int, std::size_t>::iterator iter
      = pending_event_change_index_.find(descriptor);
    if (iter == pending_event_change_index_.end())
    {
      std::size_t index = pending_event_changes_.size();
      pending_event_changes_.reserve(pending_event_changes_.size() + 1);
      pending_event_change_index_.insert(std::make_pair(descriptor, index));
      pending_event_changes_.push_back(::pollfd());
      pending_event_changes_[index].fd = descriptor;
      pending_event_changes_[index].revents = 0;
      return pending_event_changes_[index];
    }
    else
    {
      return pending_event_changes_[iter->second];
    }
  }

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

  // The /dev/poll file descriptor.
  int dev_poll_fd_;

  // Vector of /dev/poll events waiting to be written to the descriptor.
  std::vector< ::pollfd> pending_event_changes_;

  // Hash map to associate a descriptor with a pending event change index.
  hash_map<int, std::size_t> pending_event_change_index_;

  // Whether the DP_POLL operation is currently in progress
  bool wait_in_progress_;

  // The interrupter is used to break a blocking DP_POLL operation.
  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 except 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.
  asio::detail::thread* thread_;

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

} // namespace detail
} // namespace asio

#endif // defined(ASIO_HAS_DEV_POLL)

#include "asio/detail/pop_options.hpp"

#endif // ASIO_DETAIL_DEV_POLL_REACTOR_HPP