~drizzle-trunk/drizzle/development

/* - mode: c; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2008 Sun Microsystems, Inc.

 * 

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; either version 2 of the License, or

 *  (at your option) any later version.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 */

/**

 * @file 

 *

 * Structures and functions for:

 *

 * Calculating day number in Gregorian and Julian proleptic calendars.

 * Converting between day numbers and dates in the calendars.

 * Converting between different calendars.

 * Calculating differences between dates.

 *

 * Works used in research:

 *

 * @cite "Calendrical Calculations", Dershowitz and Reingold

 * @cite ISO 8601 http://en.wikipedia.org/wiki/ISO_8601

 * @cite http://www.ddj.com/hpc-high-performance-computing/197006254 

 * @cite http://en.wikipedia.org/wiki/Julian_day#Calculation

 */

#ifndef DRIZZLED_CALENDAR_H

#define DRIZZLED_CALENDAR_H

#define JULIAN_DAY_NUMBER_AT_ABSOLUTE_DAY_ONE INT64_C(1721425)

#define DAYS_IN_NORMAL_YEAR INT32_C(365)

#define DAYS_IN_LEAP_YEAR INT32_C(366)

#define GREGORIAN_START_YEAR 1582

#define GREGORIAN_START_MONTH 10

#define GREGORIAN_START_DAY 15

#define UNIX_EPOCH_MAX_YEARS 2038

#define UNIX_EPOCH_MIN_YEARS 1970

#define CALENDAR_YY_PART_YEAR 70

/**

 * The following constants define the system of calculating the number

 * of days in various periods of time in the Gregorian calendar.

 *

 * Leap years (years containing 366 days) occur:

 *

 * - When the year is evenly divisible by 4

 * - If the year is evenly divisible by 100, it must also

 *   be evenly divisible by 400.

 */

#define GREGORIAN_DAYS_IN_400_YEARS UINT32_C(146097)

#define GREGORIAN_DAYS_IN_100_YEARS UINT32_C(36524)

#define GREGORIAN_DAYS_IN_4_YEARS   UINT32_C(1461)

namespace drizzled

{

/**

 * Different calendars supported by the temporal library

 */

enum calendar

{

  GREGORIAN= 1, 

  JULIAN= 2, 

  HEBREW= 3, 

  ISLAM= 4

};

/**

 * Calculates the Julian Day Number from the year, month 

 * and day supplied for a Gregorian Proleptic calendar date.

 *

 * @note

 *

 * Year month and day values are assumed to be valid.  This 

 * method does no bounds checking or validation.

 *

 * @param Year of date

 * @param Month of date

 * @param Day of date

 */

int64_t julian_day_number_from_gregorian_date(uint32_t year, uint32_t month, uint32_t day);

/**

 * Translates an absolute day number to a 

 * Julian day number.

 *

 * @param The absolute day number

 */

int64_t absolute_day_number_to_julian_day_number(int64_t absolute_day);

/**

 * Translates a Julian day number to an 

 * absolute day number.  

 *

 * @param The Julian day number

 */

int64_t julian_day_number_to_absolute_day_number(int64_t julian_day);

/**

 * Given a supplied Julian Day Number, populates a year, month, and day

 * with the date in the Gregorian Proleptic calendar which corresponds to

 * the given Julian Day Number.

 *

 * @param Julian Day Number

 * @param Pointer to year to populate

 * @param Pointer to month to populate

 * @param Pointer to the day to populate

 */

void gregorian_date_from_julian_day_number(int64_t julian_day

                                         , uint32_t *year_out

                                         , uint32_t *month_out

                                         , uint32_t *day_out);

/**

 * Given a supplied Absolute Day Number, populates a year, month, and day

 * with the date in the Gregorian Proleptic calendar which corresponds to

 * the given Absolute Day Number.

 *

 * @param Absolute Day Number

 * @param Pointer to year to populate

 * @param Pointer to month to populate

 * @param Pointer to the day to populate

 */

void gregorian_date_from_absolute_day_number(int64_t absolute_day

                                           , uint32_t *year_out

                                           , uint32_t *month_out

                                           , uint32_t *day_out);

/**

 * Returns the number of days in a particular year.

 *

 * @param year to evaluate

 * @param calendar to use

 */

uint32_t days_in_year(uint32_t year, enum calendar calendar);

/**

 * Returns the number of days in a particular Gregorian Proleptic calendar year.

 *

 * @param year to evaluate

 */

uint32_t days_in_year_gregorian(uint32_t year);

/**

 * Returns the number of days in a particular Julian Proleptic calendar year.

 *

 * @param year to evaluate

 */

uint32_t days_in_year_julian(uint32_t year);

/**

 * Returns the number of leap years that have

 * occurred in the Julian Proleptic calendar

 * up to the supplied year.

 *

 * @param year to evaluate (1 - 9999)

 */

int32_t number_of_leap_years_julian(uint32_t year);

/**

 * Returns the number of leap years that have

 * occurred in the Gregorian Proleptic calendar

 * up to the supplied year.

 *

 * @param year to evaluate (1 - 9999)

 */

int32_t number_of_leap_years_gregorian(uint32_t year);

/**

 * Returns the number of days in a month, given

 * a year and a month in the Gregorian calendar.

 *

 * @param Year in Gregorian Proleptic calendar

 * @param Month in date

 */

uint32_t days_in_gregorian_year_month(uint32_t year, uint32_t month);

inline static bool num_leap_years(uint32_t y, enum calendar c) 

{

  return (c == GREGORIAN                

          ? number_of_leap_years_gregorian(y) 

          : number_of_leap_years_julian(y));

}

/**

 * Returns the number of the day in a week.

 *

 * @see temporal_to_number_days()

 *

 * Return values:

 *

 * Day            Day Number  Sunday first day?

 * -------------- ----------- -----------------

 * Sunday         0           true

 * Monday         1           true

 * Tuesday        2           true

 * Wednesday      3           true

 * Thursday       4           true

 * Friday         5           true

 * Saturday       6           true

 * Sunday         6           false

 * Monday         0           false

 * Tuesday        1           false

 * Wednesday      2           false

 * Thursday       3           false

 * Friday         4           false

 * Saturday       5           false

 *

 * @param Number of days since start of Gregorian calendar.

 * @param Consider Sunday the first day of the week?

 */

uint32_t day_of_week(int64_t day_number, bool sunday_is_first_day_of_week);

/**

 * Given a year, month, and day, returns whether the date is 

 * valid for the Gregorian proleptic calendar.

 *

 * @param The year

 * @param The month

 * @param The day

 */

bool is_valid_gregorian_date(uint32_t year, uint32_t month, uint32_t day);

/**

 * Returns whether the supplied date components are within the 

 * range of the UNIX epoch.

 *

 * Times in the range of 1970-01-01T00:00:00 to 2038-01-19T03:14:07

 *

 * @param Year

 * @param Month

 * @param Day

 * @param Hour

 * @param Minute

 * @param Second

 */

bool in_unix_epoch_range(uint32_t year

                       , uint32_t month

                       , uint32_t day

                       , uint32_t hour

                       , uint32_t minute

                       , uint32_t second);

/**

 * Returns the number of the week from a supplied year, month, and

 * date in the Gregorian proleptic calendar.  We use strftime() and

 * the %U, %W, and %V format specifiers depending on the value

 * of the sunday_is_first_day_of_week parameter.

 *

 * @param Subject year

 * @param Subject month

 * @param Subject day

 * @param Is sunday the first day of the week?

 * @param Pointer to a uint32_t to hold the resulting year, which 

 *        may be incremented or decremented depending on flags

 */

uint32_t week_number_from_gregorian_date(uint32_t year

                                       , uint32_t month

                                       , uint32_t day

                                       , bool sunday_is_first_day_of_week);

/**

 * Returns the ISO week number of a supplied year, month, and

 * date in the Gregorian proleptic calendar.  We use strftime() and

 * the %V format specifier to do the calculation, which yields a

 * correct ISO 8601:1988 week number.

 *

 * The final year_out parameter is a pointer to an integer which will

 * be set to the year in which the week belongs, according to ISO8601:1988, 

 * which may be different from the Gregorian calendar year.

 *

 * @see http://en.wikipedia.org/wiki/ISO_8601

 *

 * @param Subject year

 * @param Subject month

 * @param Subject day

 */

uint32_t iso_week_number_from_gregorian_date(uint32_t year

                                           , uint32_t month

                                           , uint32_t day);

/**

 * Takes a number in the form [YY]YYMM and converts it into

 * a number of months.

 *

 * @param Period in the form [YY]YYMM

 */

uint32_t year_month_to_months(uint32_t year_month);

/**

 * Takes a number of months and converts it to

 * a period in the form YYYYMM.

 *

 * @param Number of months

 */

uint32_t months_to_year_month(uint32_t months);

/**

 * Simple function returning whether the supplied year

 * is a leap year in the supplied calendar.

 *

 * @param Year to evaluate

 * @param Calendar to use

 */

inline static bool is_leap_year(uint32_t y, enum calendar c)

{

  return (days_in_year(y, c) == 366);

}

/**

 * Simple function returning whether the supplied year

 * is a leap year in the Gregorian proleptic calendar.

 */

inline static bool is_gregorian_leap_year(uint32_t y)

{

  return (days_in_year_gregorian(y) == 366);

}

/**

 * Simple function returning whether the supplied year

 * is a leap year in the Julian proleptic calendar.

 */

inline static bool is_julian_leap_year(uint32_t y) 

{

  return (days_in_year_julian(y) == 366);

}

} /* namespace drizzled */

#endif /* DRIZZLED_CALENDAR_H */