include/babeltrace/compat/utc.h

   1 #ifndef _BABELTRACE_UTC_H
   2 #define _BABELTRACE_UTC_H
   3
   4 /*
   5  * Copyright (C) 2011-2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE.
  24  */
  25
  26 #include <time.h>
  27
  28 /* If set, use GNU or BSD timegm(3) */
  29 #if defined(_BSD_SOURCE) || defined(_SVID_SOURCE)
  30
  31 static inline
  32 time_t bt_timegm(struct tm *tm)
  33 {
  34         return timegm(tm);
  35 }
  36
  37 #else
  38
  39 #include <string.h>
  40 #include <stdlib.h>
  41
  42 /*
  43  * Note: Below implementation of timegm() is not thread safe
  44  * as it changes the environment
  45  * variable TZ. It is OK as long as it is kept in self-contained program,
  46  * but should not be used within thread-safe library code.
  47  */
  48
  49 static inline
  50 time_t bt_timegm(struct tm *tm)
  51 {
  52         time_t ret;
  53         char *tz;
  54
  55         tz = getenv("TZ");
  56         /*
  57          * Make a temporary copy, as the environment variable will be
  58          * modified.
  59          */
  60         if (tz) {
  61                 tz = strdup(tz);
  62                 if (!tz) {
  63                         /*
  64                          * Memory allocation error.
  65                          */
  66                         return (time_t) -1;
  67                 }
  68         }
  69
  70         /* Temporarily setting TZ to 1 for UTC */
  71         setenv("TZ", "", 1);
  72         tzset();
  73         ret = mktime(tm);
  74         if (tz) {
  75                 setenv("TZ", tz, 1);
  76                 free(tz);
  77         } else {
  78                 unsetenv("TZ");
  79         }
  80         tzset();
  81         return ret;
  82 }
  83
  84 #endif
  85
  86 #endif /* _BABELTRACE_UTC_H */