src/runtime/time.c

   1 /*
   2  * time support routines that are easier to do in C than in Lisp
   3  */
   4
   5 /*
   6  * This software is part of the SBCL system. See the README file for
   7  * more information.
   8  *
   9  * This software is derived from the CMU CL system, which was
  10  * written at Carnegie Mellon University and released into the
  11  * public domain. The software is in the public domain and is
  12  * provided with absolutely no warranty. See the COPYING and CREDITS
  13  * files for more information.
  14  */
  15
  16 #include <stdio.h>
  17 #include <time.h>
  18 #include "sbcl.h"
  19 #include "runtime.h"
  20
  21 #ifdef LISP_FEATURE_HPUX
  22 struct tm *gmtime_r(const time_t *timer, struct tm *result);
  23 struct tm *localtime_r(const time_t *timer, struct tm *result);
  24 #endif
  25
  26 int get_timezone(time_t when, boolean *dst)
  27 {
  28     struct tm ltm, gtm;
  29     int sw;
  30
  31 #ifdef LISP_FEATURE_WIN32
  32     /* No _r versions on Windows, but the API documentation also
  33      * doesn't warn them about being non-reentrant... So here's
  34      * hoping they actually are -- once Windows grows threads
  35      * this better be checked, though.
  36      *
  37      * The Windows versions also don't support times before the
  38      * epoch, so we kludge it. */
  39     if (when < 0)
  40         when = 0;
  41     ltm = *localtime(&when);
  42     gtm = *gmtime(&when);
  43 #else
  44     ltm = *localtime_r(&when, &ltm);
  45     gtm = *gmtime_r(&when, &gtm);
  46 #endif
  47
  48     sw = (((gtm.tm_hour*60)+gtm.tm_min)*60+gtm.tm_sec) - (((ltm.tm_hour*60)+ltm.tm_min)*60+ltm.tm_sec);
  49     if ((gtm.tm_wday + 1) % 7 == ltm.tm_wday)
  50         sw -= 24*3600;
  51     else if (gtm.tm_wday == (ltm.tm_wday + 1) % 7)
  52         sw += 24*3600;
  53     *dst = ltm.tm_isdst;
  54     return sw;
  55 }