time/localtime.c

   1 /* Convert `time_t' to `struct tm' in local time zone.
   2    Copyright (C) 1991, 92, 93, 95, 96, 97 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <time.h>
  22 #include <libc-lock.h>
  23
  24 /* The C Standard says that localtime and gmtime return the same pointer.  */
  25 struct tm _tmbuf;
  26
  27 /* Prototype for the internal function to get information based on TZ.  */
  28 extern void __tzset_internal __P ((int always));
  29 extern int __tz_compute __P ((time_t timer, struct tm *tp));
  30 extern int __tzfile_compute __P ((time_t timer,
  31                                   long int *leap_correct, int *leap_hit));
  32
  33 extern int __use_tzfile;
  34
  35 /* This lock is defined in tzset.c and locks all the data defined there
  36    and in tzfile.c; the internal functions do no locking themselves.
  37    This lock is only taken here and in `tzset'.  */
  38 __libc_lock_define (extern, __tzset_lock)
  39
  40
  41 /* Return the `struct tm' representation of *TIMER in the local timezone.  */
  42 static struct tm *
  43 localtime_internal (const time_t *timer, struct tm *tp)
  44 {
  45   long int leap_correction;
  46   int leap_extra_secs;
  47
  48   if (timer == NULL)
  49     {
  50       __set_errno (EINVAL);
  51       return NULL;
  52     }
  53
  54   if (__use_tzfile)
  55     {
  56       if (! __tzfile_compute (*timer, &leap_correction, &leap_extra_secs))
  57         tp = NULL;
  58     }
  59   else
  60     {
  61       tp = __gmtime_r (timer, tp);
  62       if (tp && ! __tz_compute (*timer, tp))
  63         tp = NULL;
  64       leap_correction = 0L;
  65       leap_extra_secs = 0;
  66     }
  67
  68   if (tp)
  69     {
  70       __offtime (timer, __timezone - leap_correction, tp);
  71       tp->tm_sec += leap_extra_secs;
  72       tp->tm_isdst = __daylight;
  73       tp->tm_gmtoff = __timezone;
  74       tp->tm_zone = __tzname[__daylight];
  75     }
  76
  77   return tp;
  78 }
  79
  80
  81 /* POSIX.1 8.3.7.2 says that localtime_r is not required to set
  82    tzname.  This is a good idea since this allows at least a bit more
  83    parallelism.  */
  84
  85 struct tm *
  86 localtime (timer)
  87      const time_t *timer;
  88 {
  89   struct tm *result;
  90
  91   __libc_lock_lock (__tzset_lock);
  92
  93   /* Update internal database according to current TZ setting.  */
  94   __tzset_internal (1);
  95
  96   result = localtime_internal (timer, &_tmbuf);
  97
  98   __libc_lock_unlock (__tzset_lock);
  99
 100   return result;
 101 }
 102
 103
 104 struct tm *
 105 __localtime_r (timer, tp)
 106      const time_t *timer;
 107      struct tm *tp;
 108 {
 109   struct tm *result;
 110
 111   __libc_lock_lock (__tzset_lock);
 112
 113   /* Make sure the database is initialized.  */
 114   __tzset_internal (0);
 115
 116   result = localtime_internal (timer, tp);
 117
 118   __libc_lock_unlock (__tzset_lock);
 119
 120   return result;
 121 }
 122 weak_alias (__localtime_r, localtime_r)