tm2time.c

一款类linux的操作系统源码

#include <stdlib.h>
#include <sys/time.h>

static void
validate_structure(struct tm *tm)
{
    div_t res;

    /* Calculate time & date to account for out of range values */
    if (tm->tm_sec < 0 || tm->tm_sec > 59) {
	res = div(tm->tm_sec, 60);
	tm->tm_min += res.quot;
	if ((tm->tm_sec = res.rem) < 0)
	    tm->tm_sec += 60;
    }
    if (tm->tm_min < 0 || tm->tm_min > 59) {
	res = div(tm->tm_min, 60);
	tm->tm_hour += res.quot;
	if ((tm->tm_min = res.rem) < 0)
	    tm->tm_min += 60;
    }
    if (tm->tm_hour < 0 || tm->tm_hour > 23) {
	res = div(tm->tm_hour, 24);
	tm->tm_mday += res.quot;
	if ((tm->tm_hour = res.rem) < 0)
	    tm->tm_hour += 24;
    }
    if (tm->tm_mon > 11) {
	res = div(tm->tm_mon, 12);
	tm->tm_year += res.quot;
	if ((tm->tm_mon = res.rem) < 0)
	    tm->tm_mon += 12;
    }
    if (_DAYS_IN_YEAR(tm->tm_year) == 366)
	days_in_feb = 29;

    if (tm->tm_mday < 0) {
	while (tm->tm_mday < 0) {
	    tm->tm_mday += _DAYS_IN_MONTH(tm->tm_mon);
	    if (--tm->tm_mon == -1) {
		tm->tm_year--;
		tm->tm_mon = 12;
		days_in_feb = ((_DAYS_IN_YEAR(tm->tm_year) == 366) ? 29 : 28);
	    }
	}
    } else {
	while (tm->tm_mday > _DAYS_IN_MONTH(tm->tm_mon)) {
	    tm->tm_mday -= _DAYS_IN_MONTH(tm->tm_mon);
	    if (++tm->tm_mon == 12) {
		tm->tm_year++;
		tm->tm_mon = 0;
		days_in_feb = ((_DAYS_IN_YEAR(tm->tm_year) == 366) ? 29 : 28);
	    }
	}
    }
}

time_t
tm2time(struct tm *tm)
{
    time_t tim = 0;
    long days = 0;
    int year;

    /* Validate structure */
    validate_structure(tm);

    /* Compute hours, minutes, seconds */
    tim += tm->tm_sec + (tm->tm_min * _SEC_IN_MINUTE) +
	(tm->tm_hour * _SEC_IN_HOUR);

    /* Compute days in year */
    days += tm->tm_mday - 1;
    days += _DAYS_BEFORE_MONTH[tm->tm_mon];
    if (tm->tm_mon > 1 && _DAYS_IN_YEAR(tm->tm_year) == 366)
	days++;

    /* Compute day of the year */
    tm->tm_yday = days;

    if (tm->tm_year > 10000 || tm->tm_year < -10000) {
	return (time_t) - 1;
    }
    /* Compute days in other years */
    if (tm->tm_year > 1970) {
	for (year = 1970; year < tm->tm_year; year++)
	    days += _DAYS_IN_YEAR(year);
    } else if (tm->tm_year < 1970) {
	for (year = 1969; year > tm->tm_year; year--)
	    days -= _DAYS_IN_YEAR(year);
	days -= _DAYS_IN_YEAR(year);
    }
    /* Compute day of the week */
    if ((tm->tm_wday = (days + 4) % 7) < 0)
	tm->tm_wday += 7;

    /* Compute total seconds */
    tim += (days * _SEC_IN_DAY);

    return tim;
}