maint: update copyright

[gnulib.git] / lib / timegm.c

diff --git a/lib/timegm.c b/lib/timegm.c
index a7b953d..e80a90a 100644 (file)
--- a/lib/timegm.c
+++ b/lib/timegm.c
@@ -1,6 +1,7 @@
-/* Convert calendar time to simple time, inverse of mktime.
-   Copyright (C) 1995, 1996, 1997, 1998, 2000, 2001, 2003
-   Free Software Foundation, Inc.
+/* Convert UTC calendar time to simple time.  Like mktime but assumes UTC.
+
+   Copyright (C) 1994, 1997, 2003-2004, 2006-2007, 2009-2014 Free Software
+   Foundation, Inc.  This file is part of the GNU C Library.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -13,84 +14,25 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software Foundation,
-   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+   along with this program; if not, see <http://www.gnu.org/licenses/>.  */
 
-#if HAVE_CONFIG_H
+#ifndef _LIBC
 # include <config.h>
 #endif
 
-/* Specification.  Get mktime and gmtime declarations.  */
-#include "timegm.h"
-
-/* Converts struct tm to time_t, assuming the data in tm is UTC rather
-   than local timezone.
-
-   mktime is similar but assumes struct tm, also known as the
-   "broken-down" form of time, is in local time zone.  mktime_from_utc
-   uses mktime to make the conversion understanding that an offset
-   will be introduced by the local time assumption.
-
-   mktime_from_utc then measures the introduced offset by applying
-   gmtime to the initial result and applying mktime to the resulting
-   "broken-down" form.  The difference between the two mktime results
-   is the measured offset which is then subtracted from the initial
-   mktime result to yield a calendar time which is the value returned.
-
-   tm_isdst in struct tm is set to 0 to force mktime to introduce a
-   consistent offset (the non DST offset) since tm and tm+o might be
-   on opposite sides of a DST change.
-
-   Some implementations of mktime return -1 for the nonexistent
-   localtime hour at the beginning of DST.  In this event, use
-   mktime(tm - 1hr) + 3600.
+#include <time.h>
 
-   Schematically
-   mktime(tm)   --> t+o
-   gmtime(t+o)  --> tm+o
-   mktime(tm+o) --> t+2o
-   t+o - (t+2o - t+o) = t
-
-   Note that glibc contains a function of the same purpose named
-   `timegm' (reverse of gmtime).  But obviously, it is not universally
-   available, and unfortunately it is not straightforwardly
-   extractable for use here.  Perhaps configure should detect timegm
-   and use it where available.
-
-   Contributed by Roger Beeman <beeman@cisco.com>, with the help of
-   Mark Baushke <mdb@cisco.com> and the rest of the Gurus at CISCO.
-   Further improved by Roger with assistance from Edward J. Sabol
-   based on input by Jamie Zawinski.  */
+#ifndef _LIBC
+# undef __gmtime_r
+# define __gmtime_r gmtime_r
+# define __mktime_internal mktime_internal
+# include "mktime-internal.h"
+#endif
 
 time_t
-timegm (struct tm *tm)
+timegm (struct tm *tmp)
 {
-  time_t tl, tb;
-  struct tm *tg;
-
-  tl = mktime (tm);
-  if (tl == (time_t) -1)
-    {
-      tm->tm_hour--;
-      tl = mktime (tm);
-      if (tl == (time_t) -1)
-       return (time_t) -1;
-      tl += 3600;
-    }
-#if HAVE_GMTIME_R && HAVE_DECL_GMTIME_R
-  tg = gmtime_r (&tl, tg);
-#else
-  tg = gmtime (&tl);
-#endif
-  tg->tm_isdst = 0;
-  tb = mktime (tg);
-  if (tb == (time_t) -1)
-    {
-      tg->tm_hour--;
-      tb = mktime (tg);
-      if (tb == (time_t) -1)
-       return (time_t) -1;
-      tb += 3600;
-    }
-  return (tl - (tb - tl));
+  static time_t gmtime_offset;
+  tmp->tm_isdst = 0;
+  return __mktime_internal (tmp, __gmtime_r, &gmtime_offset);
 }