timegm.c

Linux下头文件time.h的实现源码

/* Convert UTC calendar time to simple time.  Like mktime but assumes UTC.

   Copyright (C) 1994, 1997, 2003 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 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.

   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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#ifdef _LIBC
# include <time.h>
#else
# include "timegm.h"

/* Portable standalone applications should supply a "time_r.h" that
   declares a POSIX-compliant gmtime_r, for the benefit of older
   implementations that lack gmtime_r or have a nonstandard one.
   See the gnulib time_r module for one way to implement this.  */
# include <time_r.h>
# undef __gmtime_r
# define __gmtime_r gmtime_r
time_t __mktime_internal (struct tm *,
			  struct tm * (*) (time_t const *, struct tm *),
			  time_t *);
#endif

time_t
timegm (struct tm *tmp)
{
  static time_t gmtime_offset;
  tmp->tm_isdst = 0;
  return __mktime_internal (tmp, __gmtime_r, &gmtime_offset);
}