text: //
  // time_traits.hpp
  // ~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2015 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_TIME_TRAITS_HPP
  #define BOOST_ASIO_TIME_TRAITS_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/socket_types.hpp> // Must come before posix_time.
  
  #if defined(BOOST_ASIO_HAS_BOOST_DATE_TIME) \
    || defined(GENERATING_DOCUMENTATION)
  
  #include <boost/date_time/posix_time/posix_time_types.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  
  /// Time traits suitable for use with the deadline timer.
  template <typename Time>
  struct time_traits;
  
  /// Time traits specialised for posix_time.
  template <>
  struct time_traits<boost::posix_time::ptime>
  {
    /// The time type.
    typedef boost::posix_time::ptime time_type;
  
    /// The duration type.
    typedef boost::posix_time::time_duration duration_type;
  
    /// Get the current time.
    static time_type now()
    {
  #if defined(BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK)
      return boost::posix_time::microsec_clock::universal_time();
  #else // defined(BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK)
      return boost::posix_time::second_clock::universal_time();
  #endif // defined(BOOST_DATE_TIME_HAS_HIGH_PRECISION_CLOCK)
    }
  
    /// Add a duration to a time.
    static time_type add(const time_type& t, const duration_type& d)
    {
      return t + d;
    }
  
    /// Subtract one time from another.
    static duration_type subtract(const time_type& t1, const time_type& t2)
    {
      return t1 - t2;
    }
  
    /// Test whether one time is less than another.
    static bool less_than(const time_type& t1, const time_type& t2)
    {
      return t1 < t2;
    }
  
    /// Convert to POSIX duration type.
    static boost::posix_time::time_duration to_posix_duration(
        const duration_type& d)
    {
      return d;
    }
  };
  
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
         // || defined(GENERATING_DOCUMENTATION)
  
  #endif // BOOST_ASIO_TIME_TRAITS_HPP
  