131 lines
3.3 KiB
C
131 lines
3.3 KiB
C
/*
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* mktime - convert local time into calendar time
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*/
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/* $Header$ */
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#include <time.h>
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#include <limits.h>
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#include "loc_incl.h"
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/* The code assumes that unsigned long can be converted to time_t.
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* A time_t should not be wider than unsigned long, since this would mean
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* that the check for overflow at the end could fail.
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*/
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time_t
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mktime(register struct tm *timep)
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{
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register long day, year;
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register int tm_year;
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int yday, month;
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register unsigned long seconds;
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int overflow;
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unsigned dst;
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timep->tm_min += timep->tm_sec / 60;
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timep->tm_sec %= 60;
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if (timep->tm_sec < 0) {
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timep->tm_sec += 60;
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timep->tm_min--;
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}
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timep->tm_hour += timep->tm_min / 60;
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timep->tm_min = timep->tm_min % 60;
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if (timep->tm_min < 0) {
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timep->tm_min += 60;
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timep->tm_hour--;
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}
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day = timep->tm_hour / 24;
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timep->tm_hour= timep->tm_hour % 24;
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if (timep->tm_hour < 0) {
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timep->tm_hour += 24;
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day--;
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}
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timep->tm_year += timep->tm_mon / 12;
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timep->tm_mon %= 12;
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if (timep->tm_mon < 0) {
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timep->tm_mon += 12;
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timep->tm_year--;
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}
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day += (timep->tm_mday - 1);
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while (day < 0) {
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day += YEARSIZE(YEAR0 + timep->tm_year - 1);
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timep->tm_year--;
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}
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while (day >= YEARSIZE(YEAR0 + timep->tm_year)) {
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day -= YEARSIZE(YEAR0 + timep->tm_year);
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timep->tm_year++;
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}
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while (day >= _ytab[LEAPYEAR(YEAR0 + timep->tm_year)][timep->tm_mon]) {
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day -= _ytab[LEAPYEAR(YEAR0 + timep->tm_year)][timep->tm_mon];
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if (++(timep->tm_mon) == 12) {
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timep->tm_mon = 0;
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timep->tm_year++;
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}
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}
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timep->tm_mday = day + 1;
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_tzset(); /* set timezone and dst info */
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year = EPOCH_YR;
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if (timep->tm_year < year - YEAR0) return (time_t)-1;
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seconds = 0;
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day = 0; /* means days since day 0 now */
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overflow = 0;
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/* Assume that when day becomes negative, there will certainly
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* be overflow on seconds.
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* The check for overflow needs not to be done for leapyears
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* divisible by 400.
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* The code only works when year (1970) is not a leapyear.
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*/
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#if EPOCH_YR != 1970
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#error EPOCH_YR != 1970
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#endif
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tm_year = timep->tm_year + YEAR0;
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if (LONG_MAX / 365 < tm_year - year) overflow++;
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day = (tm_year - year) * 365;
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if (LONG_MAX - day < (tm_year - year) / 4 + 1) overflow++;
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day += (tm_year - year) / 4
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+ ((tm_year % 4) && tm_year % 4 < year % 4);
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day -= (tm_year - year) / 100
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+ ((tm_year % 100) && tm_year % 100 < year % 100);
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day += (tm_year - year) / 400
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+ ((tm_year % 400) && tm_year % 400 < year % 400);
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yday = month = 0;
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while (month < timep->tm_mon) {
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yday += _ytab[LEAPYEAR(tm_year)][month];
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month++;
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}
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yday += (timep->tm_mday - 1);
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if (day + yday < 0) overflow++;
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day += yday;
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timep->tm_yday = yday;
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timep->tm_wday = (day + 4) % 7; /* day 0 was thursday (4) */
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seconds = ((timep->tm_hour * 60L) + timep->tm_min) * 60L + timep->tm_sec;
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if ((TIME_MAX - seconds) / SECS_DAY < day) overflow++;
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seconds += day * SECS_DAY;
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/* Now adjust according to timezone and daylight saving time */
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if (((_timezone > 0) && (TIME_MAX - _timezone < seconds))
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|| ((_timezone < 0) && (seconds < -_timezone)))
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overflow++;
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seconds += _timezone;
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if (timep->tm_isdst < 0)
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dst = _dstget(timep);
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else if (timep->tm_isdst)
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dst = _dst_off;
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else dst = 0;
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if (dst > seconds) overflow++; /* dst is always non-negative */
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seconds -= dst;
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if (overflow) return (time_t)-1;
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if ((time_t)seconds != seconds) return (time_t)-1;
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return (time_t)seconds;
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}
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