#ifndef DATE_TIME_C_LOCAL_TIME_ADJUSTOR_HPP__

#define DATE_TIME_C_LOCAL_TIME_ADJUSTOR_HPP__

/* Copyright (c) 2002,2003,2005 CrystalClear Software, Inc.

 * Use, modification and distribution is subject to the 

 * Boost Software License, Version 1.0. (See accompanying

 * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)

 * Author: Jeff Garland, Bart Garst

 * $Date: 2008-11-12 14:37:53 -0500 (Wed, 12 Nov 2008) $

 */

/*! @file c_local_time_adjustor.hpp

  Time adjustment calculations based on machine

*/

#include <stdexcept>

#include <boost/throw_exception.hpp>

#include <boost/date_time/compiler_config.hpp>

#include <boost/date_time/c_time.hpp>

namespace boost {

namespace date_time {

  //! Adjust to / from utc using the C API

  /*! Warning!!! This class assumes that timezone settings of the

   *  machine are correct.  This can be a very dangerous assumption.

   */

  template<class time_type>

  class c_local_adjustor {

  public:

    typedef typename time_type::time_duration_type time_duration_type;

    typedef typename time_type::date_type date_type;

    typedef typename date_type::duration_type date_duration_type;

    //! Convert a utc time to local time

    static time_type utc_to_local(const time_type& t)

    {

      date_type time_t_start_day(1970,1,1);

      time_type time_t_start_time(time_t_start_day,time_duration_type(0,0,0));

      if (t < time_t_start_time) {

        boost::throw_exception(std::out_of_range("Cannot convert dates prior to Jan 1, 1970"));

        BOOST_DATE_TIME_UNREACHABLE_EXPRESSION(return time_t_start_time); // should never reach

      }

      date_duration_type dd = t.date() - time_t_start_day;

      time_duration_type td = t.time_of_day();

      std::time_t t2 = dd.days()*86400 + td.hours()*3600 + td.minutes()*60 + td.seconds();

      std::tm tms, *tms_ptr;

      tms_ptr = c_time::localtime(&t2, &tms);

      date_type d(static_cast<unsigned short>(tms_ptr->tm_year + 1900),

                  static_cast<unsigned short>(tms_ptr->tm_mon + 1),

                  static_cast<unsigned short>(tms_ptr->tm_mday));

      time_duration_type td2(tms_ptr->tm_hour,

                             tms_ptr->tm_min,

                             tms_ptr->tm_sec,

                             t.time_of_day().fractional_seconds());

      return time_type(d,td2);

    }

  };

} } //namespace date_time

#endif