time/localtime.c

   1 /* Copyright (C) 1991, 1992, 1993, 1995 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <errno.h>
  20 #include <time.h>
  21
  22 /* The C Standard says that localtime and gmtime return the same pointer.  */
  23 struct tm _tmbuf;
  24
  25 /* Return the `struct tm' representation of *TIMER in the local timezone.  */
  26 struct tm *
  27 localtime (timer)
  28      const time_t *timer;
  29 {
  30   return __localtime_r (timer, &_tmbuf);
  31 }
  32
  33 struct tm *
  34 __localtime_r (timer, tp)
  35      const time_t *timer;
  36      struct tm *tp;
  37 {
  38   extern int __use_tzfile;
  39   extern int __tz_compute __P ((time_t timer, struct tm *tp));
  40   extern int __tzfile_compute __P ((time_t timer,
  41                                     long int *leap_correct, int *leap_hit));
  42   long int leap_correction;
  43   int leap_extra_secs;
  44
  45   if (timer == NULL)
  46     {
  47       errno = EINVAL;
  48       return NULL;
  49     }
  50
  51   {
  52     /* Make sure the database is initialized.  */
  53     extern int __tzset_run;
  54     if (! __tzset_run)
  55       __tzset ();
  56   }
  57
  58   if (__use_tzfile)
  59     {
  60       if (! __tzfile_compute (*timer, &leap_correction, &leap_extra_secs))
  61         return NULL;
  62     }
  63   else
  64     {
  65       struct tm *gmtp = __gmtime_r (timer, tp);
  66       if (gmtp == NULL)
  67         return NULL;
  68
  69       if (! __tz_compute (*timer, gmtp))
  70         return NULL;
  71
  72       leap_correction = 0L;
  73       leap_extra_secs = 0;
  74     }
  75
  76   __offtime (timer, __timezone - leap_correction, tp);
  77   tp->tm_sec += leap_extra_secs;
  78   tp->tm_isdst = __daylight;
  79   tp->tm_gmtoff = __timezone;
  80   tp->tm_zone = __tzname[__daylight];
  81   return tp;
  82 }
  83 weak_alias (__localtime_r, localtime_r)