392 lines
16 KiB
C++
392 lines
16 KiB
C++
#ifndef DATE_TIME_DST_RULES_HPP__
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#define DATE_TIME_DST_RULES_HPP__
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/* Copyright (c) 2002,2003, 2007 CrystalClear Software, Inc.
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* Use, modification and distribution is subject to the
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* Boost Software License, Version 1.0. (See accompanying
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* file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
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* Author: Jeff Garland, Bart Garst
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* $Date$
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*/
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/*! @file dst_rules.hpp
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Contains template class to provide static dst rule calculations
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*/
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#include "boost/date_time/date_generators.hpp"
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#include "boost/date_time/period.hpp"
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#include "boost/date_time/date_defs.hpp"
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#include <stdexcept>
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namespace boost {
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namespace date_time {
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enum time_is_dst_result {is_not_in_dst, is_in_dst,
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ambiguous, invalid_time_label};
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//! Dynamic class used to caluclate dst transition information
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template<class date_type_,
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class time_duration_type_>
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class dst_calculator
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{
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public:
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typedef time_duration_type_ time_duration_type;
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typedef date_type_ date_type;
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//! Check the local time offset when on dst start day
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/*! On this dst transition, the time label between
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* the transition boundary and the boudary + the offset
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* are invalid times. If before the boundary then still
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* not in dst.
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*@param time_of_day Time offset in the day for the local time
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*@param dst_start_offset_minutes Local day offset for start of dst
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*@param dst_length_minutes Number of minutes to adjust clock forward
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*@retval status of time label w.r.t. dst
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*/
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static time_is_dst_result
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process_local_dst_start_day(const time_duration_type& time_of_day,
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unsigned int dst_start_offset_minutes,
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long dst_length_minutes)
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{
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//std::cout << "here" << std::endl;
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if (time_of_day < time_duration_type(0,dst_start_offset_minutes,0)) {
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return is_not_in_dst;
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}
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long offset = dst_start_offset_minutes + dst_length_minutes;
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if (time_of_day >= time_duration_type(0,offset,0)) {
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return is_in_dst;
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}
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return invalid_time_label;
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}
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//! Check the local time offset when on the last day of dst
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/*! This is the calculation for the DST end day. On that day times
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* prior to the conversion time - dst_length (1 am in US) are still
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* in dst. Times between the above and the switch time are
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* ambiguous. Times after the start_offset are not in dst.
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*@param time_of_day Time offset in the day for the local time
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*@param dst_end_offset_minutes Local time of day for end of dst
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*@retval status of time label w.r.t. dst
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*/
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static time_is_dst_result
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process_local_dst_end_day(const time_duration_type& time_of_day,
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unsigned int dst_end_offset_minutes,
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long dst_length_minutes)
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{
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//in US this will be 60 so offset in day is 1,0,0
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int offset = dst_end_offset_minutes-dst_length_minutes;
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if (time_of_day < time_duration_type(0,offset,0)) {
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return is_in_dst;
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}
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if (time_of_day >= time_duration_type(0,dst_end_offset_minutes,0)) {
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return is_not_in_dst;
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}
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return ambiguous;
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}
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//! Calculates if the given local time is dst or not
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/*! Determines if the time is really in DST or not. Also checks for
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* invalid and ambiguous.
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* @param current_day The day to check for dst
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* @param time_of_day Time offset within the day to check
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* @param dst_start_day Starting day of dst for the given locality
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* @param dst_start_offset Time offset within day for dst boundary
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* @param dst_end_day Ending day of dst for the given locality
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* @param dst_end_offset Time offset within day given in dst for dst boundary
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* @param dst_length lenght of dst adjusment
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* @retval The time is either ambiguous, invalid, in dst, or not in dst
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*/
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static time_is_dst_result
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local_is_dst(const date_type& current_day,
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const time_duration_type& time_of_day,
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const date_type& dst_start_day,
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const time_duration_type& dst_start_offset,
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const date_type& dst_end_day,
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const time_duration_type& dst_end_offset,
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const time_duration_type& dst_length_minutes)
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{
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unsigned int start_minutes =
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dst_start_offset.hours() * 60 + dst_start_offset.minutes();
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unsigned int end_minutes =
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dst_end_offset.hours() * 60 + dst_end_offset.minutes();
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long length_minutes =
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dst_length_minutes.hours() * 60 + dst_length_minutes.minutes();
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return local_is_dst(current_day, time_of_day,
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dst_start_day, start_minutes,
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dst_end_day, end_minutes,
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length_minutes);
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}
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//! Calculates if the given local time is dst or not
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/*! Determines if the time is really in DST or not. Also checks for
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* invalid and ambiguous.
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* @param current_day The day to check for dst
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* @param time_of_day Time offset within the day to check
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* @param dst_start_day Starting day of dst for the given locality
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* @param dst_start_offset_minutes Offset within day for dst
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* boundary (eg 120 for US which is 02:00:00)
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* @param dst_end_day Ending day of dst for the given locality
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* @param dst_end_offset_minutes Offset within day given in dst for dst
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* boundary (eg 120 for US which is 02:00:00)
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* @param dst_length_minutes Length of dst adjusment (eg: 60 for US)
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* @retval The time is either ambiguous, invalid, in dst, or not in dst
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*/
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static time_is_dst_result
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local_is_dst(const date_type& current_day,
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const time_duration_type& time_of_day,
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const date_type& dst_start_day,
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unsigned int dst_start_offset_minutes,
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const date_type& dst_end_day,
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unsigned int dst_end_offset_minutes,
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long dst_length_minutes)
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{
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//in northern hemisphere dst is in the middle of the year
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if (dst_start_day < dst_end_day) {
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if ((current_day > dst_start_day) && (current_day < dst_end_day)) {
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return is_in_dst;
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}
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if ((current_day < dst_start_day) || (current_day > dst_end_day)) {
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return is_not_in_dst;
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}
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}
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else {//southern hemisphere dst is at begining /end of year
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if ((current_day < dst_start_day) && (current_day > dst_end_day)) {
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return is_not_in_dst;
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}
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if ((current_day > dst_start_day) || (current_day < dst_end_day)) {
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return is_in_dst;
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}
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}
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if (current_day == dst_start_day) {
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return process_local_dst_start_day(time_of_day,
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dst_start_offset_minutes,
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dst_length_minutes);
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}
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if (current_day == dst_end_day) {
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return process_local_dst_end_day(time_of_day,
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dst_end_offset_minutes,
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dst_length_minutes);
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}
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//you should never reach this statement
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return invalid_time_label;
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}
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};
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//! Compile-time configurable daylight savings time calculation engine
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/* This template provides the ability to configure a daylight savings
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* calculation at compile time covering all the cases. Unfortunately
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* because of the number of dimensions related to daylight savings
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* calculation the number of parameters is high. In addition, the
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* start and end transition rules are complex types that specify
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* an algorithm for calculation of the starting day and ending
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* day of daylight savings time including the month and day
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* specifications (eg: last sunday in October).
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*
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* @param date_type A type that represents dates, typically gregorian::date
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* @param time_duration_type Used for the offset in the day calculations
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* @param dst_traits A set of traits that define the rules of dst
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* calculation. The dst_trait must include the following:
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* start_rule_functor - Rule to calculate the starting date of a
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* dst transition (eg: last_kday_of_month).
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* start_day - static function that returns month of dst start for
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* start_rule_functor
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* start_month -static function that returns day or day of week for
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* dst start of dst
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* end_rule_functor - Rule to calculate the end of dst day.
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* end_day - static fucntion that returns end day for end_rule_functor
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* end_month - static function that returns end month for end_rule_functor
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* 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.
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* 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.
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* dst_length_minutes - number of minutes that dst shifts clock
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*/
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template<class date_type,
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class time_duration_type,
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class dst_traits>
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class dst_calc_engine
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{
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public:
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typedef typename date_type::year_type year_type;
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typedef typename date_type::calendar_type calendar_type;
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typedef dst_calculator<date_type, time_duration_type> dstcalc;
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//! Calculates if the given local time is dst or not
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/*! Determines if the time is really in DST or not. Also checks for
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* invalid and ambiguous.
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* @retval The time is either ambiguous, invalid, in dst, or not in dst
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*/
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static time_is_dst_result local_is_dst(const date_type& d,
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const time_duration_type& td)
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{
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year_type y = d.year();
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date_type dst_start = local_dst_start_day(y);
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date_type dst_end = local_dst_end_day(y);
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return dstcalc::local_is_dst(d,td,
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dst_start,
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dst_traits::dst_start_offset_minutes(),
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dst_end,
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dst_traits::dst_end_offset_minutes(),
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dst_traits::dst_shift_length_minutes());
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}
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static bool is_dst_boundary_day(date_type d)
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{
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year_type y = d.year();
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return ((d == local_dst_start_day(y)) ||
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(d == local_dst_end_day(y)));
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}
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//! The time of day for the dst transition (eg: typically 01:00:00 or 02:00:00)
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static time_duration_type dst_offset()
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{
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return time_duration_type(0,dst_traits::dst_shift_length_minutes(),0);
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}
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static date_type local_dst_start_day(year_type year)
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{
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return dst_traits::local_dst_start_day(year);
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}
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static date_type local_dst_end_day(year_type year)
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{
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return dst_traits::local_dst_end_day(year);
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}
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};
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//! Depricated: Class to calculate dst boundaries for US time zones
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/* Use dst_calc_engine instead.
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* In 2007 US/Canada DST rules changed
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* (http://en.wikipedia.org/wiki/Energy_Policy_Act_of_2005#Change_to_daylight_saving_time).
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*/
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template<class date_type_,
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class time_duration_type_,
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unsigned int dst_start_offset_minutes=120, //from start of day
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short dst_length_minutes=60> //1 hour == 60 min in US
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class us_dst_rules
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{
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public:
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typedef time_duration_type_ time_duration_type;
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typedef date_type_ date_type;
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typedef typename date_type::year_type year_type;
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typedef typename date_type::calendar_type calendar_type;
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typedef date_time::last_kday_of_month<date_type> lkday;
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typedef date_time::first_kday_of_month<date_type> fkday;
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typedef date_time::nth_kday_of_month<date_type> nkday;
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typedef dst_calculator<date_type, time_duration_type> dstcalc;
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//! Calculates if the given local time is dst or not
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/*! Determines if the time is really in DST or not. Also checks for
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* invalid and ambiguous.
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* @retval The time is either ambiguous, invalid, in dst, or not in dst
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*/
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static time_is_dst_result local_is_dst(const date_type& d,
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const time_duration_type& td)
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{
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year_type y = d.year();
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date_type dst_start = local_dst_start_day(y);
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date_type dst_end = local_dst_end_day(y);
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return dstcalc::local_is_dst(d,td,
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dst_start,dst_start_offset_minutes,
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dst_end, dst_start_offset_minutes,
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dst_length_minutes);
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}
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static bool is_dst_boundary_day(date_type d)
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{
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year_type y = d.year();
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return ((d == local_dst_start_day(y)) ||
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(d == local_dst_end_day(y)));
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}
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static date_type local_dst_start_day(year_type year)
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{
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if (year >= year_type(2007)) {
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//second sunday in march
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nkday ssim(nkday::second, Sunday, gregorian::Mar);
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return ssim.get_date(year);
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} else {
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//first sunday in april
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fkday fsia(Sunday, gregorian::Apr);
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return fsia.get_date(year);
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}
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}
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static date_type local_dst_end_day(year_type year)
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{
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if (year >= year_type(2007)) {
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//first sunday in november
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fkday fsin(Sunday, gregorian::Nov);
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return fsin.get_date(year);
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} else {
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//last sunday in october
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lkday lsio(Sunday, gregorian::Oct);
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return lsio.get_date(year);
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}
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}
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static time_duration_type dst_offset()
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{
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return time_duration_type(0,dst_length_minutes,0);
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}
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private:
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};
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//! Used for local time adjustments in places that don't use dst
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template<class date_type_, class time_duration_type_>
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class null_dst_rules
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{
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public:
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typedef time_duration_type_ time_duration_type;
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typedef date_type_ date_type;
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//! Calculates if the given local time is dst or not
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/*! @retval Always is_not_in_dst since this is for zones without dst
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*/
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static time_is_dst_result local_is_dst(const date_type&,
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const time_duration_type&)
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{
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return is_not_in_dst;
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}
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//! Calculates if the given utc time is in dst
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static time_is_dst_result utc_is_dst(const date_type&,
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const time_duration_type&)
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{
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return is_not_in_dst;
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}
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static bool is_dst_boundary_day(date_type /*d*/)
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{
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return false;
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}
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static time_duration_type dst_offset()
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{
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return time_duration_type(0,0,0);
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}
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};
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} } //namespace date_time
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#endif
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