text: //
  // detail/deadline_timer_service.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2011 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_DEADLINE_TIMER_SERVICE_HPP
  #define BOOST_ASIO_DETAIL_DEADLINE_TIMER_SERVICE_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/config.hpp>
  #include <cstddef>
  #include <boost/asio/error.hpp>
  #include <boost/asio/io_service.hpp>
  #include <boost/asio/detail/bind_handler.hpp>
  #include <boost/asio/detail/fenced_block.hpp>
  #include <boost/asio/detail/noncopyable.hpp>
  #include <boost/asio/detail/socket_ops.hpp>
  #include <boost/asio/detail/socket_types.hpp>
  #include <boost/asio/detail/timer_op.hpp>
  #include <boost/asio/detail/timer_queue.hpp>
  #include <boost/asio/detail/timer_scheduler.hpp>
  #include <boost/asio/detail/wait_handler.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  #include <boost/date_time/posix_time/posix_time_types.hpp>
  #include <boost/asio/detail/pop_options.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace detail {
  
  template <typename Time_Traits>
  class deadline_timer_service
  {
  public:
    // The time type.
    typedef typename Time_Traits::time_type time_type;
  
    // The duration type.
    typedef typename Time_Traits::duration_type duration_type;
  
    // The implementation type of the timer. This type is dependent on the
    // underlying implementation of the timer service.
    struct implementation_type
      : private boost::asio::detail::noncopyable
    {
      time_type expiry;
      bool might_have_pending_waits;
      typename timer_queue<Time_Traits>::per_timer_data timer_data;
    };
  
    // Constructor.
    deadline_timer_service(boost::asio::io_service& io_service)
      : scheduler_(boost::asio::use_service<timer_scheduler>(io_service))
    {
      scheduler_.init_task();
      scheduler_.add_timer_queue(timer_queue_);
    }
  
    // Destructor.
    ~deadline_timer_service()
    {
      scheduler_.remove_timer_queue(timer_queue_);
    }
  
    // Destroy all user-defined handler objects owned by the service.
    void shutdown_service()
    {
    }
  
    // Construct a new timer implementation.
    void construct(implementation_type& impl)
    {
      impl.expiry = time_type();
      impl.might_have_pending_waits = false;
    }
  
    // Destroy a timer implementation.
    void destroy(implementation_type& impl)
    {
      boost::system::error_code ec;
      cancel(impl, ec);
    }
  
    // Cancel any asynchronous wait operations associated with the timer.
    std::size_t cancel(implementation_type& impl, boost::system::error_code& ec)
    {
      if (!impl.might_have_pending_waits)
      {
        ec = boost::system::error_code();
        return 0;
      }
      std::size_t count = scheduler_.cancel_timer(timer_queue_, impl.timer_data);
      impl.might_have_pending_waits = false;
      ec = boost::system::error_code();
      return count;
    }
  
    // Get the expiry time for the timer as an absolute time.
    time_type expires_at(const implementation_type& impl) const
    {
      return impl.expiry;
    }
  
    // Set the expiry time for the timer as an absolute time.
    std::size_t expires_at(implementation_type& impl,
        const time_type& expiry_time, boost::system::error_code& ec)
    {
      std::size_t count = cancel(impl, ec);
      impl.expiry = expiry_time;
      ec = boost::system::error_code();
      return count;
    }
  
    // Get the expiry time for the timer relative to now.
    duration_type expires_from_now(const implementation_type& impl) const
    {
      return Time_Traits::subtract(expires_at(impl), Time_Traits::now());
    }
  
    // Set the expiry time for the timer relative to now.
    std::size_t expires_from_now(implementation_type& impl,
        const duration_type& expiry_time, boost::system::error_code& ec)
    {
      return expires_at(impl,
          Time_Traits::add(Time_Traits::now(), expiry_time), ec);
    }
  
    // Perform a blocking wait on the timer.
    void wait(implementation_type& impl, boost::system::error_code& ec)
    {
      time_type now = Time_Traits::now();
      while (Time_Traits::less_than(now, impl.expiry))
      {
        boost::posix_time::time_duration timeout =
          Time_Traits::to_posix_duration(Time_Traits::subtract(impl.expiry, now));
        ::timeval tv;
        tv.tv_sec = timeout.total_seconds();
        tv.tv_usec = timeout.total_microseconds() % 1000000;
        boost::system::error_code ec;
        socket_ops::select(0, 0, 0, 0, &tv, ec);
        now = Time_Traits::now();
      }
      ec = boost::system::error_code();
    }
  
    // Start an asynchronous wait on the timer.
    template <typename Handler>
    void async_wait(implementation_type& impl, Handler handler)
    {
      // Allocate and construct an operation to wrap the handler.
      typedef wait_handler<Handler> op;
      typename op::ptr p = { boost::addressof(handler),
        boost_asio_handler_alloc_helpers::allocate(
          sizeof(op), handler), 0 };
      p.p = new (p.v) op(handler);
  
      impl.might_have_pending_waits = true;
  
      scheduler_.schedule_timer(timer_queue_, impl.expiry, impl.timer_data, p.p);
      p.v = p.p = 0;
    }
  
  private:
    // The queue of timers.
    timer_queue<Time_Traits> timer_queue_;
  
    // The object that schedules and executes timers. Usually a reactor.
    timer_scheduler& scheduler_;
  };
  
  } // namespace detail
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // BOOST_ASIO_DETAIL_DEADLINE_TIMER_SERVICE_HPP
  