libc/time/localtime.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2008  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   4  *  Copyright (C) 2009  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   5  *
   6  *  This program is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20
  21 #include <time.h>
  22
  23 #define MINUTE          60
  24 #define HOUR            (60 * MINUTE)
  25 #define DAY             (24 * HOUR)
  26 #define YEAR            (365 * DAY)
  27
  28 struct tm tmbuf;
  29
  30 /*
  31         The localtime function converts the simple time pointed to by time to broken-down time representation,
  32         expressed relative to the user's specified time zone.
  33         The return value is a pointer to a static broken-down time structure,
  34         which might be overwritten by subsequent calls to ctime, gmtime, or localtime.
  35         (But no other library function overwrites the contents of this object.)
  36 */
  37
  38 struct tm *localtime_r (const time_t *time, struct tm *resultp)
  39 {
  40         if (!resultp || !time)
  41                 return 0;
  42
  43         time_t c = *time;
  44
  45         resultp->tm_year = c/YEAR;
  46
  47         c -= resultp->tm_year * YEAR;
  48         resultp->tm_mday = c / DAY;
  49
  50         c -= resultp->tm_mday * DAY;
  51         resultp->tm_hour = c / HOUR;
  52
  53         c -= resultp->tm_hour * HOUR;
  54         resultp->tm_min = c / MINUTE;
  55
  56         c -= resultp->tm_min * MINUTE;
  57         resultp->tm_sec = c;
  58
  59         resultp->tm_year += EPOCH_YEAR;
  60         resultp->tm_mday -= 8;  // FIXME: hack
  61
  62         resultp->tm_wday = resultp->tm_mday;
  63
  64         while (resultp->tm_wday > 6)
  65                 resultp->tm_wday -= 7;
  66
  67         resultp->tm_isdst = 0;
  68
  69         return resultp;
  70 }
  71
  72 /*      NOTE: There is problem in multi-threaded application, because tmpbuf can be rewrited whenever */
  73 struct tm *localtime (const time_t *time)
  74 {
  75         return localtime_r (time, &tmbuf);
  76 }