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104 lines
3.3 KiB
C
104 lines
3.3 KiB
C
/*****************************************************************************
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* gmtime_r.c: POSIX gmtime_r() replacement
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*****************************************************************************
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* Copyright © 2011-2012 Rémi Denis-Courmont
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
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*****************************************************************************/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <time.h>
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#include <stdio.h>
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#include <stdlib.h>
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struct tm *gmtime_r (const time_t *timep, struct tm *tm)
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{
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#if defined (_WIN32)
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errno_t ret = gmtime_s(tm, timep);
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if (ret == 0)
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return tm;
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errno = ret;
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return NULL;
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#else // !_WIN32
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static const unsigned short normal[12] =
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{ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
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static const unsigned short leap[12] =
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{ 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
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lldiv_t d;
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const unsigned short *months;
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/* Rebase from 1970 Unix epoch to fictitious year 0 (i.e. would-be
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* year 1 BC had the Gregorian calendar already existed then) */
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d.quot = 60LL * 60 * 24 * (4 * 146097 + 135140) + *timep;
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d = lldiv (d.quot, 60); /* 60 seconds per minute */
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if (*timep < 0)
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{
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d.rem += 60;
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d.quot--;
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}
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tm->tm_sec = d.rem;
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d = lldiv (d.quot, 60); /* 60 minutes per hour */
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tm->tm_min = d.rem;
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d = lldiv (d.quot, 24); /* 24 hours per day */
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tm->tm_hour = d.rem;
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tm->tm_wday = (d.quot + 6) % 7; /* 7 days per week */
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d = lldiv (d.quot, 146097); /* 146097 days per 4 centuries */
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tm->tm_year = 400 * d.quot;
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if (d.rem >= 36525)
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{ /* Century with 24 leap years */
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d.rem -= 36525;
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tm->tm_year += 100;
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d = lldiv (d.rem, 36524); /* 36524 days per normal century */
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tm->tm_year += d.quot * 100;
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if (d.rem >= 59) /* not in January or February of year 00 */
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d.rem++; /* insert missing February 29th 00*/
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}
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tm->tm_year -= 1900; /* Rebase to 1900 for struct tm */
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d = lldiv (d.rem, 1461); /* 1461 days per 4 years */
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tm->tm_year += 4 * d.quot;
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if (d.rem >= 366)
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{ /* Non-leap year */
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d.rem -= 366;
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tm->tm_year++;
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d = lldiv (d.rem, 365); /* 365 days per normal year */
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tm->tm_year += d.quot;
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months = normal;
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}
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else
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months = leap;
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tm->tm_yday = d.rem;
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for (tm->tm_mon = 0; d.rem >= months[tm->tm_mon]; tm->tm_mon++)
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d.rem -= months[tm->tm_mon]; /* 28 to 31 days in a month */
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tm->tm_mday = d.rem + 1;
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tm->tm_isdst = 0; /* UTC time */
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return tm;
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#endif // !_WIN32
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}
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