ceph/src/boost/boost/date_time/gregorian_calendar.ipp

   1 /* Copyright (c) 2002,2003 CrystalClear Software, Inc.
   2  * Use, modification and distribution is subject to the
   3  * Boost Software License, Version 1.0. (See accompanying
   4  * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
   5  * Author: Jeff Garland, Bart Garst
   6  * $Date$
   7  */
   8
   9
  10 namespace boost {
  11 namespace date_time {
  12   //! Return the day of the week (0==Sunday, 1==Monday, etc)
  13   /*! Converts a year-month-day into a day of the week number
  14    */
  15   template<typename ymd_type_, typename date_int_type_>
  16   BOOST_CXX14_CONSTEXPR
  17   inline
  18   unsigned short
  19   gregorian_calendar_base<ymd_type_,date_int_type_>::day_of_week(const ymd_type& ymd) {
  20     unsigned short a = static_cast<unsigned short>((14-ymd.month)/12);
  21     unsigned short y = static_cast<unsigned short>(ymd.year - a);
  22     unsigned short m = static_cast<unsigned short>(ymd.month + 12*a - 2);
  23     unsigned short d = static_cast<unsigned short>((ymd.day + y + (y/4) - (y/100) + (y/400) + (31*m)/12) % 7);
  24     //std::cout << year << "-" << month << "-" << day << " is day: " << d << "\n";
  25     return d;
  26   }
  27
  28   //!Return the iso week number for the date
  29   /*!Implements the rules associated with the iso 8601 week number.
  30     Basically the rule is that Week 1 of the year is the week that contains
  31     January 4th or the week that contains the first Thursday in January.
  32     Reference for this algorithm is the Calendar FAQ by Claus Tondering, April 2000.
  33   */
  34   template<typename ymd_type_, typename date_int_type_>
  35   BOOST_CXX14_CONSTEXPR
  36   inline
  37   int
  38   gregorian_calendar_base<ymd_type_,date_int_type_>::week_number(const ymd_type& ymd) {
  39     unsigned long julianbegin = julian_day_number(ymd_type(ymd.year,1,1));
  40     unsigned long juliantoday = julian_day_number(ymd);
  41     unsigned long day = (julianbegin + 3) % 7;
  42     unsigned long week = (juliantoday + day - julianbegin + 4)/7;
  43
  44     if ((week >= 1) && (week <= 52)) {
  45       return static_cast<int>(week);
  46     }
  47
  48     if (week == 53) {
  49       if((day==6) ||(day == 5 && is_leap_year(ymd.year))) {
  50         return static_cast<int>(week); //under these circumstances week == 53.
  51       } else {
  52         return 1; //monday - wednesday is in week 1 of next year
  53       }
  54     }
  55     //if the week is not in current year recalculate using the previous year as the beginning year
  56     else if (week == 0) {
  57       julianbegin = julian_day_number(ymd_type(static_cast<unsigned short>(ymd.year-1),1,1));
  58       juliantoday = julian_day_number(ymd);
  59       day = (julianbegin + 3) % 7;
  60       week = (juliantoday + day - julianbegin + 4)/7;
  61       return static_cast<int>(week);
  62     }
  63
  64     return static_cast<int>(week);  //not reachable -- well except if day == 5 and is_leap_year != true
  65
  66   }
  67
  68   //! Convert a ymd_type into a day number
  69   /*! The day number is an absolute number of days since the start of count
  70    */
  71   template<typename ymd_type_, typename date_int_type_>
  72   BOOST_CXX14_CONSTEXPR
  73   inline
  74   date_int_type_
  75   gregorian_calendar_base<ymd_type_,date_int_type_>::day_number(const ymd_type& ymd)
  76   {
  77     unsigned short a = static_cast<unsigned short>((14-ymd.month)/12);
  78     unsigned short y = static_cast<unsigned short>(ymd.year + 4800 - a);
  79     unsigned short m = static_cast<unsigned short>(ymd.month + 12*a - 3);
  80     unsigned long  d = static_cast<unsigned long>(ymd.day) + ((153*m + 2)/5) + 365*y + (y/4) - (y/100) + (y/400) - 32045;
  81     return static_cast<date_int_type>(d);
  82   }
  83
  84   //! Convert a year-month-day into the julian day number
  85   /*! Since this implementation uses julian day internally, this is the same as the day_number.
  86    */
  87   template<typename ymd_type_, typename date_int_type_>
  88   BOOST_CXX14_CONSTEXPR
  89   inline
  90   date_int_type_
  91   gregorian_calendar_base<ymd_type_,date_int_type_>::julian_day_number(const ymd_type& ymd)
  92   {
  93     return day_number(ymd);
  94   }
  95
  96   //! Convert year-month-day into a modified julian day number
  97   /*! The day number is an absolute number of days.
  98    *  MJD 0 thus started on 17 Nov 1858(Gregorian) at 00:00:00 UTC
  99    */
 100   template<typename ymd_type_, typename date_int_type_>
 101   BOOST_CXX14_CONSTEXPR
 102   inline
 103   date_int_type_
 104   gregorian_calendar_base<ymd_type_,date_int_type_>::modjulian_day_number(const ymd_type& ymd)
 105   {
 106     return julian_day_number(ymd)-2400001; //prerounded
 107   }
 108
 109   //! Change a day number into a year-month-day
 110   template<typename ymd_type_, typename date_int_type_>
 111   BOOST_CXX14_CONSTEXPR
 112   inline
 113   ymd_type_
 114   gregorian_calendar_base<ymd_type_,date_int_type_>::from_day_number(date_int_type dayNumber)
 115   {
 116     date_int_type a = dayNumber + 32044;
 117     date_int_type b = (4*a + 3)/146097;
 118     date_int_type c = a-((146097*b)/4);
 119     date_int_type d = (4*c + 3)/1461;
 120     date_int_type e = c - (1461*d)/4;
 121     date_int_type m = (5*e + 2)/153;
 122     unsigned short day = static_cast<unsigned short>(e - ((153*m + 2)/5) + 1);
 123     unsigned short month = static_cast<unsigned short>(m + 3 - 12 * (m/10));
 124     year_type year = static_cast<unsigned short>(100*b + d - 4800 + (m/10));
 125     //std::cout << year << "-" << month << "-" << day << "\n";
 126
 127     return ymd_type(static_cast<unsigned short>(year),month,day);
 128   }
 129
 130   //! Change a day number into a year-month-day
 131   template<typename ymd_type_, typename date_int_type_>
 132   BOOST_CXX14_CONSTEXPR
 133   inline
 134   ymd_type_
 135   gregorian_calendar_base<ymd_type_,date_int_type_>::from_julian_day_number(date_int_type dayNumber)
 136   {
 137     date_int_type a = dayNumber + 32044;
 138     date_int_type b = (4*a+3)/146097;
 139     date_int_type c = a - ((146097*b)/4);
 140     date_int_type d = (4*c + 3)/1461;
 141     date_int_type e = c - ((1461*d)/4);
 142     date_int_type m = (5*e + 2)/153;
 143     unsigned short day = static_cast<unsigned short>(e - ((153*m + 2)/5) + 1);
 144     unsigned short month = static_cast<unsigned short>(m + 3 - 12 * (m/10));
 145     year_type year = static_cast<year_type>(100*b + d - 4800 + (m/10));
 146     //std::cout << year << "-" << month << "-" << day << "\n";
 147
 148     return ymd_type(year,month,day);
 149   }
 150
 151   //! Change a modified julian day number into a year-month-day
 152   template<typename ymd_type_, typename date_int_type_>
 153   BOOST_CXX14_CONSTEXPR
 154   inline
 155   ymd_type_
 156   gregorian_calendar_base<ymd_type_,date_int_type_>::from_modjulian_day_number(date_int_type dayNumber) {
 157     date_int_type jd = dayNumber + 2400001; //is 2400000.5 prerounded
 158     return from_julian_day_number(jd);
 159   }
 160
 161   //! Determine if the provided year is a leap year
 162   /*!
 163    *@return true if year is a leap year, false otherwise
 164    */
 165   template<typename ymd_type_, typename date_int_type_>
 166   BOOST_CXX14_CONSTEXPR
 167   inline
 168   bool
 169   gregorian_calendar_base<ymd_type_,date_int_type_>::is_leap_year(year_type year)
 170   {
 171     //divisible by 4, not if divisible by 100, but true if divisible by 400
 172     return (!(year % 4))  && ((year % 100) || (!(year % 400)));
 173   }
 174
 175   //! Calculate the last day of the month
 176   /*! Find the day which is the end of the month given year and month
 177    *  No error checking is performed.
 178    */
 179   template<typename ymd_type_, typename date_int_type_>
 180   BOOST_CXX14_CONSTEXPR
 181   inline
 182   unsigned short
 183   gregorian_calendar_base<ymd_type_,date_int_type_>::end_of_month_day(year_type year,
 184                                                                       month_type month)
 185   {
 186     switch (month) {
 187     case 2:
 188       if (is_leap_year(year)) {
 189         return 29;
 190       } else {
 191         return 28;
 192       }
 193     case 4:
 194     case 6:
 195     case 9:
 196     case 11:
 197       return 30;
 198     default:
 199       return 31;
 200     }
 201   }
 202
 203   //! Provide the ymd_type specification for the calendar start
 204   template<typename ymd_type_, typename date_int_type_>
 205   BOOST_CXX14_CONSTEXPR
 206   inline
 207   ymd_type_
 208   gregorian_calendar_base<ymd_type_,date_int_type_>::epoch()
 209   {
 210     return ymd_type(1400,1,1);
 211   }
 212
 213   //! Defines length of a week for week calculations
 214   template<typename ymd_type_, typename date_int_type_>
 215   BOOST_CXX14_CONSTEXPR
 216   inline
 217   unsigned short
 218   gregorian_calendar_base<ymd_type_,date_int_type_>::days_in_week()
 219   {
 220     return 7;
 221   }
 222
 223
 224 } } //namespace gregorian