Subversion Repositories Kolibri OS

 * Original Author: Adapted from tzcode maintained by Arthur David Olson.

 * Modifications:

 * - Changed to mktm_r and added __tzcalc_limits - 04/10/02, Jeff Johnston

 * - Fixed bug in mday computations - 08/12/04, Alex Mogilnikov 

 * - Fixed bug in __tzcalc_limits - 08/12/04, Alex Mogilnikov 

 * - Move code from _mktm_r() to gmtime_r() - 05/09/14, Freddie Chopin 

 * - Fixed bug in calculations for dates after year 2069 or before year 1901. Ideas for

 *   solution taken from musl's __secs_to_tm() - 07/12/2014, Freddie Chopin

 *   

 * - Use faster algorithm from civil_from_days() by Howard Hinnant - 12/06/2014,

 * Freddie Chopin 

 *

 * Converts the calendar time pointed to by tim_p into a broken-down time

 * expressed as local time. Returns a pointer to a structure containing the

 * broken-down time.

#include "local.h"

/* Move epoch from 01.01.1970 to 01.03.0000 (yes, Year 0) - this is the first

 * day of a 400-year long "era", right after additional day of leap year.

 * This adjustment is required only for date calculation, so instead of

 * modifying time_t value (which would require 64-bit operations to work

 * correctly) it's enough to adjust the calculated number of days since epoch.

 */

#define EPOCH_ADJUSTMENT_DAYS	719468L

/* year to which the adjustment was made */

#define ADJUSTED_EPOCH_YEAR	0

/* 1st March of year 0 is Wednesday */

#define ADJUSTED_EPOCH_WDAY	3

/* there are 97 leap years in 400-year periods. ((400 - 97) * 365 + 97 * 366) */

#define DAYS_PER_ERA		146097L

/* there are 24 leap years in 100-year periods. ((100 - 24) * 365 + 24 * 366) */

#define DAYS_PER_CENTURY	36524L

/* there is one leap year every 4 years */

#define DAYS_PER_4_YEARS	(3 * 365 + 366)

/* number of days in a non-leap year */

#define DAYS_PER_YEAR		365

/* number of days in January */

#define DAYS_IN_JANUARY		31

/* number of days in non-leap February */

#define DAYS_IN_FEBRUARY	28

/* number of years per era */

	struct tm *__restrict res)

{

  long days, rem;

  _CONST time_t lcltime = *tim_p;

  int era, weekday, year;

  unsigned erayear, yearday, month, day;

  unsigned long eraday;

  days = ((long)lcltime) / SECSPERDAY + EPOCH_ADJUSTMENT_DAYS;

  rem = ((long)lcltime) % SECSPERDAY;

  if (rem < 0)

    {

      rem += SECSPERDAY;

      --days;

    }

  /* compute hour, min, and sec */

  res->tm_hour = (int) (rem / SECSPERHOUR);

  rem %= SECSPERHOUR;

  res->tm_min = (int) (rem / SECSPERMIN);

  res->tm_sec = (int) (rem % SECSPERMIN);

  /* compute day of week */

  if ((weekday = ((ADJUSTED_EPOCH_WDAY + days) % DAYSPERWEEK)) < 0)

    weekday += DAYSPERWEEK;

  res->tm_wday = weekday;

  /* compute year, month, day & day of year */

  /* for description of this algorithm see

   * http://howardhinnant.github.io/date_algorithms.html#civil_from_days */

  era = (days >= 0 ? days : days - (DAYS_PER_ERA - 1)) / DAYS_PER_ERA;

  eraday = days - era * DAYS_PER_ERA;	/* [0, 146096] */

  erayear = (eraday - eraday / (DAYS_PER_4_YEARS - 1) + eraday / DAYS_PER_CENTURY -

      eraday / (DAYS_PER_ERA - 1)) / 365;	/* [0, 399] */

  yearday = eraday - (DAYS_PER_YEAR * erayear + erayear / 4 - erayear / 100);	/* [0, 365] */

  month = (5 * yearday + 2) / 153;	/* [0, 11] */

  day = yearday - (153 * month + 2) / 5 + 1;	/* [1, 31] */

  month += month < 10 ? 2 : -10;

  year = ADJUSTED_EPOCH_YEAR + erayear + era * YEARS_PER_ERA + (month <= 1);

  res->tm_yday = yearday >= DAYS_PER_YEAR - DAYS_IN_JANUARY - DAYS_IN_FEBRUARY ?

      yearday - (DAYS_PER_YEAR - DAYS_IN_JANUARY - DAYS_IN_FEBRUARY) :

      yearday + DAYS_IN_JANUARY + DAYS_IN_FEBRUARY + isleap(erayear);

  res->tm_year = year - YEAR_BASE;

  res->tm_mon = month;

  res->tm_mday = day;

  res->tm_isdst = 0;