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Localtime: basics initial calculations. Year missing.

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This commit is contained in:
antirez 2018-07-04 13:16:53 +02:00
parent 6a52906758
commit 06ca400f95
1 changed files with 30 additions and 2 deletions
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32
src/localtime.c
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@ -39,6 +39,34 @@
* This function takes the timezone 'tz' as argument, and the 'dst' flag is
* used to check if daylight saving time is currently in effect. The caller
* of this function should obtain such information calling tzset() ASAP in the
* main() function, and later accessing the globals 'timezone' and 'daylight'. */
void nolocks_localtime(struct tm *tmptr, time_t t, time_t tz, int dst) {
* main() function, and later accessing the globals 'timezone' and 'daylight'.
*
* Note that this function does not work for dates < 1/1/1970, it is solely
* designed to work with what time(NULL) may return, and to support Redis
* logging of the dates, it's not really a complete implementation. */
static int is_leap_year(time_t year) {
if (year % 4) return 0;
else if (year % 100) return 1;
else if (year % 400) return 0;
else return 1;
}
void nolocks_localtime(struct tm *tmp, time_t t, time_t tz, int dst) {
const time_t secs_min = 60;
const time_t secs_hour = 3600;
const time_t secs_day = 3600*24;
t += tz; /* Adjust for timezone. */
time_t days = t / secs_day; /* Days passed since epoch. */
time_t seconds = t % secs_day; /* Remaining seconds. */
tmp->tm_isdst = dst;
tmp->tm_hour = seconds / secs_hour;
tmp->tm_min = (seconds % secs_hour) / secs_min;
tmp->tm_sec = (seconds % secs_hour) % secs_min;
/* 1/1/1970 was a Thursday, that is, day 4 from the POV of the tm structure
* where sunday = 0, so to calculate the day of the week we have to add 4
* and take the modulo by 7. */
tmp->tm_wday = (days+4)%7;
}