69 lines
1.9 KiB
C
69 lines
1.9 KiB
C
#include <time.h>
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#include <internals/time.h>
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/*
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mktime()
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Converts broken-down time to calendar time. Computes structure fields
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tm_wday and tm_yday using the other fields. Member structures outside
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their range are normalized (e.g. 40 October becomes 9 November) and
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tm_isdst is set.
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*/
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time_t mktime(struct tm *time)
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{
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int leaps, yr;
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int days, i;
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// Normalizing time.
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time->tm_min += (time->tm_sec / 60);
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time->tm_hour += (time->tm_min / 60);
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time->tm_mday += (time->tm_hour / 24);
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time->tm_sec %= 60;
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time->tm_min %= 60;
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time->tm_hour %= 24;
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// Normalizing date.
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days = daysInMonth(time->tm_mon, time->tm_year + 1900);
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while(time->tm_mday >= days)
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{
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time->tm_mday -= days;
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if(++time->tm_mon == 12)
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{
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time->tm_mon = 0;
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time->tm_year++;
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}
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days = daysInMonth(time->tm_mon, time->tm_year + 1900);
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}
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// Setting the year day.
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days = 0;
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for(i = 0; i < time->tm_mon; i++)
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days += daysInMonth(i, time->tm_year + 1900);
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time->tm_yday = days + time->tm_mday;
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// Setting the week day. The calendar is periodic over 400 years and
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// 1601-01-01 was a Monday.
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// Years completely elapsed since last 400n + 1 year (1601-2001-etc).
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yr = (time->tm_year + 1900 - 1) % 400;
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// Leap years in these yr years.
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leaps = (yr / 4) - (yr >= 100) - (yr >= 200) - (yr >= 300);
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// Days completely elapsed since last 400n + 1 year, 01-01.
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days = 365 * yr + leaps + time->tm_yday;
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// Current day of week (1 means Monday 1601-01-01).
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time->tm_wday = (1 + days) % 7;
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// This RTC does not seem to have any DST feature.
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time->tm_isdst = 0;
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if(time->tm_year + 1900 < 1970) return (time_t)-1;
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// 134774 is the number of days between 1601-01-01 and 1970-01-01. Thus
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// days become the number of days elapsed since 1970-01-01.
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days -= 134774;
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// days may become negative, so add the calendar period.
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if(days < 0) days += 146097;
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return (time_t)((24 * 3600) * days + 3600 * time->tm_hour +
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60 * time->tm_min + time->tm_sec);
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}
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