StdLib/LibC/Time/timegm.c

   1 /** @file
   2   timegm implementation
   3
   4   Copyright (c) 2011, Intel Corporation. All rights reserved.<BR>
   5   This program and the accompanying materials are licensed and made available under
   6   the terms and conditions of the BSD License that accompanies this distribution.
   7   The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php.
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13   * Copyright (c) 1987, 1989 Regents of the University of California.
  14  * All rights reserved.
  15  *
  16  * This code is derived from software contributed to Berkeley by
  17  * Arthur David Olson of the National Cancer Institute.
  18  *
  19  * Redistribution and use in source and binary forms, with or without
  20  * modification, are permitted provided that the following conditions
  21  * are met:
  22  * 1. Redistributions of source code must retain the above copyright
  23  *    notice, this list of conditions and the following disclaimer.
  24  * 2. Redistributions in binary form must reproduce the above copyright
  25  *    notice, this list of conditions and the following disclaimer in the
  26  *    documentation and/or other materials provided with the distribution.
  27  * 3. All advertising materials mentioning features or use of this software
  28  *    must display the following acknowledgement:
  29  *      This product includes software developed by the University of
  30  *      California, Berkeley and its contributors.
  31  * 4. Neither the name of the University nor the names of its contributors
  32  *    may be used to endorse or promote products derived from this software
  33  *    without specific prior written permission.
  34  *
  35  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  36  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  38  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  39  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  40  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  41  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  42  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  43  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  44  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  45  * SUCH DAMAGE.
  46
  47 static char *sccsid = "from: @(#)ctime.c        5.26 (Berkeley) 2/23/91";
  48
  49
  50  * This implementation of mktime is lifted straight from the NetBSD (BSD 4.4)
  51  * version.  I modified it slightly to divorce it from the internals of the
  52  * ctime library.  Thus this version can't use details of the internal
  53  * timezone state file to figure out strange unnormalized struct tm values,
  54  * as might result from someone doing date math on the tm struct then passing
  55  * it to mktime.
  56  *
  57  * It just does as well as it can at normalizing the tm input, then does a
  58  * binary search of the time space using the system's localtime() function.
  59  *
  60  * The original binary search was defective in that it didn't consider the
  61  * setting of tm_isdst when comparing tm values, causing the search to be
  62  * flubbed for times near the dst/standard time changeover.  The original
  63  * code seems to make up for this by grubbing through the timezone info
  64  * whenever the binary search barfed.  Since I don't have that luxury in
  65  * portable code, I have to take care of tm_isdst in the comparison routine.
  66  * This requires knowing how many minutes offset dst is from standard time.
  67  *
  68  * So, if you live somewhere in the world where dst is not 60 minutes offset,
  69  * and your vendor doesn't supply mktime(), you'll have to edit this variable
  70  * by hand.  Sorry about that.
  71
  72         $NetBSD: mktime.c,v 1.4 2006/06/11 19:34:10 kardel Exp $
  73 **/
  74
  75 #include  <LibConfig.h>
  76 #include  <time.h>
  77
  78 /*
  79   This funciton is in Time.c, which has a different license than timegm.
  80 */
  81 time_t
  82 time2(struct tm * const tmp, void (* const funcp)(const time_t*, long, struct tm*),
  83       const long offset, int * const okayp);
  84
  85 /*
  86   This funciton is in Time.c, which has a different license than timegm.
  87 */
  88 void
  89 gmtsub(
  90   const time_t * const  timep,
  91   const long            offset,
  92   struct tm    * const  tmp
  93   );
  94
  95 #ifndef WRONG
  96 #define WRONG (-1)
  97 #endif /* !defined WRONG */
  98
  99 /*
 100   Convert a tm structure to a GMT based time_t.
 101 */
 102 time_t timegm( struct tm * tmp )
 103 {
 104         register time_t                 t;
 105         int                             okay;
 106
 107         tmp->tm_isdst = 0;
 108         t = time2(tmp, gmtsub, 0, &okay);
 109         if (okay || tmp->tm_isdst < 0)
 110                 return t;
 111
 112         return WRONG;
 113 }