src/compat/utc.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2011-2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  */
   6
   7 #ifndef _BABELTRACE_UTC_H
   8 #define _BABELTRACE_UTC_H
   9
  10 #include <time.h>
  11
  12 /* If set, use GNU or BSD timegm(3) */
  13 #if defined(_BSD_SOURCE) || defined(_SVID_SOURCE)
  14
  15 static inline
  16 time_t bt_timegm(struct tm *tm)
  17 {
  18         return timegm(tm);
  19 }
  20
  21 #elif defined(__MINGW32__)
  22
  23 static inline
  24 time_t bt_timegm(struct tm *tm)
  25 {
  26         return _mkgmtime(tm);
  27 }
  28
  29 #else
  30
  31 #include <errno.h>
  32
  33 /*
  34  * This is a simple implementation of timegm() it just turns the "struct tm" into
  35  * a GMT time_t. It does not normalize any of the fields of the "struct tm", nor
  36  * does it set tm_wday or tm_yday.
  37  */
  38
  39 static inline
  40 int bt_leapyear(int year)
  41 {
  42     return ((year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0));
  43 }
  44
  45 static inline
  46 time_t bt_timegm(struct tm *tm)
  47 {
  48         int year, month, total_days;
  49
  50         int monthlen[2][12] = {
  51                 /* Days per month for a regular year */
  52                 { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
  53                 /* Days per month for a leap year */
  54                 { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
  55         };
  56
  57         if ((tm->tm_mon >= 12) ||
  58                         (tm->tm_mday >= 32) ||
  59                         (tm->tm_hour >= 24) ||
  60                         (tm->tm_min >= 60) ||
  61                         (tm->tm_sec >= 61)) {
  62                 errno = EOVERFLOW;
  63                 return (time_t) -1;
  64         }
  65
  66         /* Add 365 days for each year since 1970 */
  67         total_days = 365 * (tm->tm_year - 70);
  68
  69         /* Add one day for each leap year since 1970 */
  70         for (year = 70; year < tm->tm_year; year++) {
  71                 if (bt_leapyear(1900 + year)) {
  72                         total_days++;
  73                 }
  74         }
  75
  76         /* Add days for each remaining month */
  77         for (month = 0; month < tm->tm_mon; month++) {
  78                 total_days += monthlen[bt_leapyear(1900 + year)][month];
  79         }
  80
  81         /* Add remaining days */
  82         total_days += tm->tm_mday - 1;
  83
  84         return ((((total_days * 24) + tm->tm_hour) * 60 + tm->tm_min) * 60 + tm->tm_sec);
  85 }
  86
  87 #endif
  88
  89 #endif /* _BABELTRACE_UTC_H */