text: //
  // detail/impl/select_reactor.ipp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  
  #ifndef BOOST_ASIO_DETAIL_IMPL_SELECT_REACTOR_IPP
  #define BOOST_ASIO_DETAIL_IMPL_SELECT_REACTOR_IPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/config.hpp>
  
  #if defined(BOOST_ASIO_HAS_IOCP) \
    || (!defined(BOOST_ASIO_HAS_DEV_POLL) \
        && !defined(BOOST_ASIO_HAS_EPOLL) \
        && !defined(BOOST_ASIO_HAS_KQUEUE) \
        && !defined(BOOST_ASIO_WINDOWS_RUNTIME))
  
  #include <boost/asio/detail/bind_handler.hpp>
  #include <boost/asio/detail/fd_set_adapter.hpp>
  #include <boost/asio/detail/select_reactor.hpp>
  #include <boost/asio/detail/signal_blocker.hpp>
  #include <boost/asio/detail/socket_ops.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace detail {
  
  select_reactor::select_reactor(boost::asio::io_service& io_service)
    : boost::asio::detail::service_base<select_reactor>(io_service),
      io_service_(use_service<io_service_impl>(io_service)),
      mutex_(),
      interrupter_(),
  #if defined(BOOST_ASIO_HAS_IOCP)
      stop_thread_(false),
      thread_(0),
  #endif // defined(BOOST_ASIO_HAS_IOCP)
      shutdown_(false)
  {
  #if defined(BOOST_ASIO_HAS_IOCP)
    boost::asio::detail::signal_blocker sb;
    thread_ = new boost::asio::detail::thread(
        bind_handler(&select_reactor::call_run_thread, this));
  #endif // defined(BOOST_ASIO_HAS_IOCP)
  }
  
  select_reactor::~select_reactor()
  {
    shutdown_service();
  }
  
  void select_reactor::shutdown_service()
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    shutdown_ = true;
  #if defined(BOOST_ASIO_HAS_IOCP)
    stop_thread_ = true;
  #endif // defined(BOOST_ASIO_HAS_IOCP)
    lock.unlock();
  
  #if defined(BOOST_ASIO_HAS_IOCP)
    if (thread_)
    {
      interrupter_.interrupt();
      thread_->join();
      delete thread_;
      thread_ = 0;
    }
  #endif // defined(BOOST_ASIO_HAS_IOCP)
  
    op_queue<operation> ops;
  
    for (int i = 0; i < max_ops; ++i)
      op_queue_[i].get_all_operations(ops);
  
    timer_queues_.get_all_timers(ops);
  
    io_service_.abandon_operations(ops);
  }
  
  void select_reactor::fork_service(boost::asio::io_service::fork_event fork_ev)
  {
    if (fork_ev == boost::asio::io_service::fork_child)
      interrupter_.recreate();
  }
  
  void select_reactor::init_task()
  {
    io_service_.init_task();
  }
  
  int select_reactor::register_descriptor(socket_type,
      select_reactor::per_descriptor_data&)
  {
    return 0;
  }
  
  int select_reactor::register_internal_descriptor(
      int op_type, socket_type descriptor,
      select_reactor::per_descriptor_data&, reactor_op* op)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
  
    op_queue_[op_type].enqueue_operation(descriptor, op);
    interrupter_.interrupt();
  
    return 0;
  }
  
  void select_reactor::move_descriptor(socket_type,
      select_reactor::per_descriptor_data&,
      select_reactor::per_descriptor_data&)
  {
  }
  
  void select_reactor::start_op(int op_type, socket_type descriptor,
      select_reactor::per_descriptor_data&, reactor_op* op,
      bool is_continuation, bool)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
  
    if (shutdown_)
    {
      post_immediate_completion(op, is_continuation);
      return;
    }
  
    bool first = op_queue_[op_type].enqueue_operation(descriptor, op);
    io_service_.work_started();
    if (first)
      interrupter_.interrupt();
  }
  
  void select_reactor::cancel_ops(socket_type descriptor,
      select_reactor::per_descriptor_data&)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    cancel_ops_unlocked(descriptor, boost::asio::error::operation_aborted);
  }
  
  void select_reactor::deregister_descriptor(socket_type descriptor,
      select_reactor::per_descriptor_data&, bool)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    cancel_ops_unlocked(descriptor, boost::asio::error::operation_aborted);
  }
  
  void select_reactor::deregister_internal_descriptor(
      socket_type descriptor, select_reactor::per_descriptor_data&)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    op_queue<operation> ops;
    for (int i = 0; i < max_ops; ++i)
      op_queue_[i].cancel_operations(descriptor, ops);
  }
  
  void select_reactor::run(bool block, op_queue<operation>& ops)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
  
  #if defined(BOOST_ASIO_HAS_IOCP)
    // Check if the thread is supposed to stop.
    if (stop_thread_)
      return;
  #endif // defined(BOOST_ASIO_HAS_IOCP)
  
    // Set up the descriptor sets.
    for (int i = 0; i < max_select_ops; ++i)
      fd_sets_[i].reset();
    fd_sets_[read_op].set(interrupter_.read_descriptor());
    socket_type max_fd = 0;
    bool have_work_to_do = !timer_queues_.all_empty();
    for (int i = 0; i < max_select_ops; ++i)
    {
      have_work_to_do = have_work_to_do || !op_queue_[i].empty();
      fd_sets_[i].set(op_queue_[i], ops);
      if (fd_sets_[i].max_descriptor() > max_fd)
        max_fd = fd_sets_[i].max_descriptor();
    }
  
  #if defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
    // Connection operations on Windows use both except and write fd_sets.
    have_work_to_do = have_work_to_do || !op_queue_[connect_op].empty();
    fd_sets_[write_op].set(op_queue_[connect_op], ops);
    if (fd_sets_[write_op].max_descriptor() > max_fd)
      max_fd = fd_sets_[write_op].max_descriptor();
    fd_sets_[except_op].set(op_queue_[connect_op], ops);
    if (fd_sets_[except_op].max_descriptor() > max_fd)
      max_fd = fd_sets_[except_op].max_descriptor();
  #endif // defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
  
    // We can return immediately if there's no work to do and the reactor is
    // not supposed to block.
    if (!block && !have_work_to_do)
      return;
  
    // Determine how long to block while waiting for events.
    timeval tv_buf = { 0, 0 };
    timeval* tv = block ? get_timeout(tv_buf) : &tv_buf;
  
    lock.unlock();
  
    // Block on the select call until descriptors become ready.
    boost::system::error_code ec;
    int retval = socket_ops::select(static_cast<int>(max_fd + 1),
        fd_sets_[read_op], fd_sets_[write_op], fd_sets_[except_op], tv, ec);
  
    // Reset the interrupter.
    if (retval > 0 && fd_sets_[read_op].is_set(interrupter_.read_descriptor()))
    {
      interrupter_.reset();
      --retval;
    }
  
    lock.lock();
  
    // Dispatch all ready operations.
    if (retval > 0)
    {
  #if defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
      // Connection operations on Windows use both except and write fd_sets.
      fd_sets_[except_op].perform(op_queue_[connect_op], ops);
      fd_sets_[write_op].perform(op_queue_[connect_op], ops);
  #endif // defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
  
      // Exception operations must be processed first to ensure that any
      // out-of-band data is read before normal data.
      for (int i = max_select_ops - 1; i >= 0; --i)
        fd_sets_[i].perform(op_queue_[i], ops);
    }
    timer_queues_.get_ready_timers(ops);
  }
  
  void select_reactor::interrupt()
  {
    interrupter_.interrupt();
  }
  
  #if defined(BOOST_ASIO_HAS_IOCP)
  void select_reactor::run_thread()
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    while (!stop_thread_)
    {
      lock.unlock();
      op_queue<operation> ops;
      run(true, ops);
      io_service_.post_deferred_completions(ops);
      lock.lock();
    }
  }
  
  void select_reactor::call_run_thread(select_reactor* reactor)
  {
    reactor->run_thread();
  }
  #endif // defined(BOOST_ASIO_HAS_IOCP)
  
  void select_reactor::do_add_timer_queue(timer_queue_base& queue)
  {
    mutex::scoped_lock lock(mutex_);
    timer_queues_.insert(&queue);
  }
  
  void select_reactor::do_remove_timer_queue(timer_queue_base& queue)
  {
    mutex::scoped_lock lock(mutex_);
    timer_queues_.erase(&queue);
  }
  
  timeval* select_reactor::get_timeout(timeval& tv)
  {
    // 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.
    long usec = timer_queues_.wait_duration_usec(5 * 60 * 1000 * 1000);
    tv.tv_sec = usec / 1000000;
    tv.tv_usec = usec % 1000000;
    return &tv;
  }
  
  void select_reactor::cancel_ops_unlocked(socket_type descriptor,
      const boost::system::error_code& ec)
  {
    bool need_interrupt = false;
    op_queue<operation> ops;
    for (int i = 0; i < max_ops; ++i)
      need_interrupt = op_queue_[i].cancel_operations(
          descriptor, ops, ec) || need_interrupt;
    io_service_.post_deferred_completions(ops);
    if (need_interrupt)
      interrupter_.interrupt();
  }
  
  } // namespace detail
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // defined(BOOST_ASIO_HAS_IOCP)
         //   || (!defined(BOOST_ASIO_HAS_DEV_POLL)
         //       && !defined(BOOST_ASIO_HAS_EPOLL)
         //       && !defined(BOOST_ASIO_HAS_KQUEUE))
         //       && !defined(BOOST_ASIO_WINDOWS_RUNTIME))
  
  #endif // BOOST_ASIO_DETAIL_IMPL_SELECT_REACTOR_IPP
  