time/localtime_r.c

   1 /*
   2  * (C)2012 Michael Duane Rice All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * Redistributions of source code must retain the above copyright notice, this
   9  * list of conditions and the following disclaimer. Redistributions in binary
  10  * form must reproduce the above copyright notice, this list of conditions
  11  * and the following disclaimer in the documentation and/or other materials
  12  * provided with the distribution. Neither the name of the copyright holders
  13  * nor the names of contributors may be used to endorse or promote products
  14  * derived from this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  17  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  20  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  26  * POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /* $Id: localtime_r.c 2318 2013-03-30 11:59:28Z swfltek $ */
  30
  31 /*
  32         Re entrant version of localtime(). Given a binary UTC time stamp, add the time
  33         zone and Daylight savings offset, then break it down into calendar time.
  34 */
  35
  36 #include <time.h>
  37
  38 extern long     __utc_offset;
  39
  40 extern int      (*__dst_ptr) (const time_t *, int32_t *);
  41
  42 void
  43 localtime_r(const time_t * timer, struct tm * timeptr)
  44 {
  45         time_t          lt;
  46         int16_t         dst;
  47
  48         dst = -1;
  49
  50         if (__dst_ptr)
  51                 dst = __dst_ptr(timer, &__utc_offset);
  52
  53         lt = *timer + __utc_offset;
  54
  55         if (dst > 0)
  56                 lt += dst;
  57
  58         gmtime_r(&lt, timeptr);
  59         timeptr->tm_isdst = dst;
  60 }