/*****************************************************************************
* gmtime_r.c: POSIX gmtime_r() replacement
*****************************************************************************
- * Copyright © 1998-2008 the VideoLAN project
+ * Copyright © 2011-2012 Rémi Denis-Courmont
*
- * 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
+ * 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 General Public License for more details.
+ * 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 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.
+ * 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
#endif
#include <time.h>
+#include <stdio.h>
+#include <stdlib.h>
-struct tm *gmtime_r (const time_t *timep, struct tm *result)
+struct tm *gmtime_r (const time_t *timep, struct tm *tm)
{
- struct tm *s = gmtime (timep);
- if (s == NULL)
- return NULL;
+ static const unsigned short normal[12] =
+ { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+ static const unsigned short leap[12] =
+ { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+ lldiv_t d;
+ const unsigned short *months;
- *result = *s;
- return result;
+ /* Rebase from 1970 Unix epoch to fictitious year 0 (i.e. would-be
+ * year 1 BC had the Gregorian calendar already existed then) */
+ d.quot = 60LL * 60 * 24 * (4 * 146097 + 135140) + *timep;
+
+ d = lldiv (d.quot, 60); /* 60 seconds per minute */
+ if (*timep < 0)
+ {
+ d.rem += 60;
+ d.quot--;
+ }
+ tm->tm_sec = d.rem;
+
+ d = lldiv (d.quot, 60); /* 60 minutes per hour */
+ tm->tm_min = d.rem;
+
+ d = lldiv (d.quot, 24); /* 24 hours per day */
+ tm->tm_hour = d.rem;
+
+ tm->tm_wday = (d.quot + 6) % 7; /* 7 days per week */
+
+ d = lldiv (d.quot, 146097); /* 146097 days per 4 centuries */
+ tm->tm_year = 400 * d.quot;
+
+ if (d.rem >= 36525)
+ { /* Century with 24 leap years */
+ d.rem -= 36525;
+ tm->tm_year += 100;
+
+ d = lldiv (d.rem, 36524); /* 36524 days per normal century */
+ tm->tm_year += d.quot * 100;
+ if (d.rem >= 59) /* not in January or February of year 00 */
+ d.rem++; /* insert missing February 29th 00*/
+ }
+ tm->tm_year -= 1900; /* Rebase to 1900 for struct tm */
+
+ d = lldiv (d.rem, 1461); /* 1461 days per 4 years */
+ tm->tm_year += 4 * d.quot;
+
+ if (d.rem >= 366)
+ { /* Non-leap year */
+ d.rem -= 366;
+ tm->tm_year++;
+
+ d = lldiv (d.rem, 365); /* 365 days per normal year */
+ tm->tm_year += d.quot;
+ months = normal;
+ }
+ else
+ months = leap;
+ tm->tm_yday = d.rem;
+
+ for (tm->tm_mon = 0; d.rem >= months[tm->tm_mon]; tm->tm_mon++)
+ d.rem -= months[tm->tm_mon]; /* 28 to 31 days in a month */
+ tm->tm_mday = d.rem + 1;
+
+ tm->tm_isdst = 0; /* UTC time */
+ return tm;
}