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include/boost/date_time/dst_rules.hpp  view on Meta::CPAN

          if ((current_day < dst_start_day) && (current_day > dst_end_day)) {
            return is_not_in_dst;
          }
          if ((current_day > dst_start_day) || (current_day < dst_end_day)) {
            return is_in_dst;
          }
        }

        if (current_day == dst_start_day) {
          return process_local_dst_start_day(time_of_day,
                                             dst_start_offset_minutes,
                                             dst_length_minutes);
        }
      
        if (current_day == dst_end_day) {
          return process_local_dst_end_day(time_of_day,
                                           dst_end_offset_minutes,
                                           dst_length_minutes);
        }
        //you should never reach this statement
        return invalid_time_label;
      }

    };


    //! Compile-time configurable daylight savings time calculation engine
    /* This template provides the ability to configure a daylight savings
     * calculation at compile time covering all the cases.  Unfortunately
     * because of the number of dimensions related to daylight savings
     * calculation the number of parameters is high.  In addition, the
     * start and end transition rules are complex types that specify 
     * an algorithm for calculation of the starting day and ending
     * day of daylight savings time including the month and day 
     * specifications (eg: last sunday in October).
     *
     * @param date_type A type that represents dates, typically gregorian::date
     * @param time_duration_type Used for the offset in the day calculations
     * @param dst_traits A set of traits that define the rules of dst 
     *        calculation.  The dst_trait must include the following:
     * start_rule_functor - Rule to calculate the starting date of a
     *                      dst transition (eg: last_kday_of_month).
     * start_day - static function that returns month of dst start for 
     *             start_rule_functor
     * start_month -static function that returns day or day of week for 
     *              dst start of dst
     * end_rule_functor - Rule to calculate the end of dst day.
     * end_day - static fucntion that returns end day for end_rule_functor
     * end_month - static function that returns end month for end_rule_functor
     * dst_start_offset_minutes - number of minutes from start of day to transition to dst -- 120 (or 2:00 am) is typical for the U.S. and E.U.
     * dst_start_offset_minutes - number of minutes from start of day to transition off of dst -- 180 (or 3:00 am) is typical for E.U. 
     * dst_length_minutes - number of minutes that dst shifts clock
     */
    template<class date_type, 
             class time_duration_type,
             class dst_traits>
    class dst_calc_engine
    {
    public:
      typedef typename date_type::year_type year_type;
      typedef typename date_type::calendar_type calendar_type;
      typedef dst_calculator<date_type, time_duration_type> dstcalc;

      //! Calculates if the given local time is dst or not
      /*! Determines if the time is really in DST or not.  Also checks for 
       *  invalid and ambiguous.
       *  @retval The time is either ambiguous, invalid, in dst, or not in dst
       */
      static time_is_dst_result local_is_dst(const date_type& d,
                                             const time_duration_type& td) 
      {

        year_type y = d.year();
        date_type dst_start = local_dst_start_day(y);
        date_type dst_end   = local_dst_end_day(y);
        return dstcalc::local_is_dst(d,td,
                                     dst_start,
                                     dst_traits::dst_start_offset_minutes(),
                                     dst_end, 
                                     dst_traits::dst_end_offset_minutes(), 
                                     dst_traits::dst_shift_length_minutes());
      
      }

      static bool is_dst_boundary_day(date_type d)
      {
        year_type y = d.year();
        return ((d == local_dst_start_day(y)) ||
                (d == local_dst_end_day(y)));
      }

      //! The time of day for the dst transition (eg: typically 01:00:00 or 02:00:00)
      static time_duration_type dst_offset() 
      {
        return time_duration_type(0,dst_traits::dst_shift_length_minutes(),0);
      }

      static date_type local_dst_start_day(year_type year)
      {
        typedef typename dst_traits::start_rule_functor start_rule;
        start_rule start(dst_traits::start_day(), 
                         dst_traits::start_month());
        return start.get_date(year);      
      }

      static date_type local_dst_end_day(year_type year)
      {
        typedef typename dst_traits::end_rule_functor end_rule;
        end_rule end(dst_traits::end_day(), 
                     dst_traits::end_month());
        return end.get_date(year);      
      }


    };

    //! Depricated: Class to calculate dst boundaries for US time zones
    /* Use dst_calc_engine instead.
     */
    template<class date_type_, 
             class time_duration_type_,
             unsigned int dst_start_offset_minutes=120, //from start of day 
             short dst_length_minutes=60>  //1 hour == 60 min in US
    class us_dst_rules 
    {
    public:
      typedef time_duration_type_ time_duration_type;
      typedef date_type_ date_type;
      typedef typename date_type::year_type year_type;
      typedef typename date_type::calendar_type calendar_type;
      typedef date_time::last_kday_of_month<date_type> lkday;
      typedef date_time::first_kday_of_month<date_type> fkday;
      typedef dst_calculator<date_type, time_duration_type> dstcalc;

      //! Calculates if the given local time is dst or not
      /*! Determines if the time is really in DST or not.  Also checks for 
       *  invalid and ambiguous.
       *  @retval The time is either ambiguous, invalid, in dst, or not in dst
       */
      static time_is_dst_result local_is_dst(const date_type& d,
                                             const time_duration_type& td) 
      {

        year_type y = d.year();
        date_type dst_start = local_dst_start_day(y);
        date_type dst_end   = local_dst_end_day(y);
        return dstcalc::local_is_dst(d,td,
                                     dst_start,dst_start_offset_minutes,
                                     dst_end, dst_start_offset_minutes, 
                                     dst_length_minutes);
      
      }


      static bool is_dst_boundary_day(date_type d)
      {
        year_type y = d.year();
        return ((d == local_dst_start_day(y)) ||
                (d == local_dst_end_day(y)));
      }

      static date_type local_dst_start_day(year_type year)
      {
        //first sunday in april
        fkday fsia(Sunday, gregorian::Apr);
        return fsia.get_date(year);      
      }

      static date_type local_dst_end_day(year_type year)
      {
        //last sunday in october
        lkday lsio(Sunday, gregorian::Oct);
        return lsio.get_date(year);
      }

      static time_duration_type dst_offset()
      {
        return time_duration_type(0,dst_length_minutes,0);
      }


    };

    //! Used for local time adjustments in places that don't use dst
    template<class date_type_, class time_duration_type_>
    class null_dst_rules
    {
    public:
      typedef time_duration_type_ time_duration_type;
      typedef date_type_ date_type;