glibc/time/localtime.c

/* Copyright (C) 1991, 1992, 1993, 1995 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <errno.h>
#include <time.h>

/* The C Standard says that localtime and gmtime return the same pointer.  */
struct tm _tmbuf;

/* Return the `struct tm' representation of *TIMER in the local timezone.  */
struct tm *
localtime (timer)
     const time_t *timer;
{
  return __localtime_r (timer, &_tmbuf);
}

struct tm *
__localtime_r (timer, tp)
     const time_t *timer;
     struct tm *tp;
{
  extern int __use_tzfile;
  extern int __tz_compute __P ((time_t timer, struct tm *tp));
  extern int __tzfile_compute __P ((time_t timer,
				    long int *leap_correct, int *leap_hit));
  long int leap_correction;
  int leap_extra_secs;

  if (timer == NULL)
    {
      errno = EINVAL;
      return NULL;
    }

  {
    /* Make sure the database is initialized.  */
    extern int __tzset_run;
    if (! __tzset_run)
      __tzset ();
  }

  if (__use_tzfile)
    {
      if (! __tzfile_compute (*timer, &leap_correction, &leap_extra_secs))
	return NULL;
    }
  else
    {
      struct tm *gmtp = __gmtime_r (timer, tp);
      if (gmtp == NULL)
	return NULL;

      if (! __tz_compute (*timer, gmtp))
	return NULL;

      leap_correction = 0L;
      leap_extra_secs = 0;
    }

  __offtime (timer, __timezone - leap_correction, tp);
  tp->tm_sec += leap_extra_secs;
  tp->tm_isdst = __daylight;
  tp->tm_gmtoff = __timezone;
  tp->tm_zone = __tzname[__daylight];
  return tp;
}
weak_alias (__localtime_r, localtime_r)