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/*****************************************************************************
* timegm.c: BSD/GNU timegm() replacement
*****************************************************************************
* Copyright © 2007 Laurent Aimar
* Copyright © 2015 Rémi Denis-Courmont
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
*****************************************************************************/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdbool.h>
#include <time.h>
static bool is_leap_year(unsigned y)
{
if (y % 4)
return false;
if (y % 100)
return true;
if (y % 400)
return false;
return true;
}
time_t timegm(struct tm *tm)
{
static const unsigned ydays[12 + 1] = {
0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
};
if (tm->tm_year < 70 /* FIXME: (negative) dates before Epoch */
|| tm->tm_mon < 0 || tm->tm_mon > 11
|| tm->tm_mday < 1 || tm->tm_mday > 31
|| tm->tm_hour < 0 || tm->tm_hour > 23
|| tm->tm_min < 0 || tm->tm_min > 59
|| tm->tm_sec < 0 || tm->tm_sec > 60 /* mind the leap second */)
return -1;
/* Count the number of days */
unsigned t = 365 * (tm->tm_year - 70)
+ ydays[tm->tm_mon] + (tm->tm_mday - 1);
/* TODO: unroll */
for (int i = 70; i < tm->tm_year; i++)
t += is_leap_year(1900 + i);
if (tm->tm_mon > 1)
t += is_leap_year(1900 + tm->tm_year);
t *= 24;
t += tm->tm_hour;
t *= 60;
t += tm->tm_min;
t *= 60;
t += tm->tm_sec;
return t;
}
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