259 lines
6.5 KiB
C
259 lines
6.5 KiB
C
/*
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* mktime.c
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* Original Author: G. Haley
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*
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* Converts the broken-down time, expressed as local time, in the structure
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* pointed to by tim_p into a calendar time value. The original values of the
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* tm_wday and tm_yday fields of the structure are ignored, and the original
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* values of the other fields have no restrictions. On successful completion
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* the fields of the structure are set to represent the specified calendar
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* time. Returns the specified calendar time. If the calendar time can not be
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* represented, returns the value (time_t) -1.
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*/
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/*
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FUNCTION
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<<mktime>>---convert time to arithmetic representation
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INDEX
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mktime
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ANSI_SYNOPSIS
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#include <time.h>
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time_t mktime(struct tm *<[timp]>);
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TRAD_SYNOPSIS
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#include <time.h>
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time_t mktime(<[timp]>)
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struct tm *<[timp]>;
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DESCRIPTION
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<<mktime>> assumes the time at <[timp]> is a local time, and converts
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its representation from the traditional representation defined by
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<<struct tm>> into a representation suitable for arithmetic.
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<<localtime>> is the inverse of <<mktime>>.
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RETURNS
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If the contents of the structure at <[timp]> do not form a valid
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calendar time representation, the result is <<-1>>. Otherwise, the
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result is the time, converted to a <<time_t>> value.
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PORTABILITY
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ANSI C requires <<mktime>>.
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<<mktime>> requires no supporting OS subroutines.
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*/
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#include <stdlib.h>
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#include <time.h>
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#include "local.h"
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#define _SEC_IN_MINUTE 60L
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#define _SEC_IN_HOUR 3600L
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#define _SEC_IN_DAY 86400L
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static _CONST int DAYS_IN_MONTH[12] =
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{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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#define _DAYS_IN_MONTH(x) ((x == 1) ? days_in_feb : DAYS_IN_MONTH[x])
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static _CONST int _DAYS_BEFORE_MONTH[12] =
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{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
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#define _ISLEAP(y) (((y) % 4) == 0 && (((y) % 100) != 0 || (((y)+1900) % 400) == 0))
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#define _DAYS_IN_YEAR(year) (_ISLEAP(year) ? 366 : 365)
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static void
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validate_structure (tim_p)
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struct tm *tim_p;
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{
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div_t res;
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int days_in_feb = 28;
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/* calculate time & date to account for out of range values */
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if (tim_p->tm_sec < 0 || tim_p->tm_sec > 59)
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{
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res = div (tim_p->tm_sec, 60);
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tim_p->tm_min += res.quot;
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if ((tim_p->tm_sec = res.rem) < 0)
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{
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tim_p->tm_sec += 60;
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--tim_p->tm_min;
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}
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}
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if (tim_p->tm_min < 0 || tim_p->tm_min > 59)
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{
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res = div (tim_p->tm_min, 60);
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tim_p->tm_hour += res.quot;
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if ((tim_p->tm_min = res.rem) < 0)
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{
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tim_p->tm_min += 60;
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--tim_p->tm_hour;
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}
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}
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if (tim_p->tm_hour < 0 || tim_p->tm_hour > 23)
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{
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res = div (tim_p->tm_hour, 24);
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tim_p->tm_mday += res.quot;
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if ((tim_p->tm_hour = res.rem) < 0)
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{
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tim_p->tm_hour += 24;
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--tim_p->tm_mday;
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}
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}
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if (tim_p->tm_mon > 11)
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{
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res = div (tim_p->tm_mon, 12);
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tim_p->tm_year += res.quot;
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if ((tim_p->tm_mon = res.rem) < 0)
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{
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tim_p->tm_mon += 12;
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--tim_p->tm_year;
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}
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}
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if (_DAYS_IN_YEAR (tim_p->tm_year) == 366)
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days_in_feb = 29;
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if (tim_p->tm_mday <= 0)
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{
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while (tim_p->tm_mday <= 0)
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{
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if (--tim_p->tm_mon == -1)
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{
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tim_p->tm_year--;
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tim_p->tm_mon = 11;
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days_in_feb =
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((_DAYS_IN_YEAR (tim_p->tm_year) == 366) ?
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29 : 28);
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}
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tim_p->tm_mday += _DAYS_IN_MONTH (tim_p->tm_mon);
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}
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}
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else
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{
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while (tim_p->tm_mday > _DAYS_IN_MONTH (tim_p->tm_mon))
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{
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tim_p->tm_mday -= _DAYS_IN_MONTH (tim_p->tm_mon);
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if (++tim_p->tm_mon == 12)
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{
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tim_p->tm_year++;
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tim_p->tm_mon = 0;
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days_in_feb =
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((_DAYS_IN_YEAR (tim_p->tm_year) == 366) ?
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29 : 28);
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}
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}
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}
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}
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time_t
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mktime (tim_p)
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struct tm *tim_p;
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{
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time_t tim = 0;
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long days = 0;
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int year, isdst;
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__tzinfo_type *tz = __gettzinfo ();
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/* validate structure */
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validate_structure (tim_p);
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/* compute hours, minutes, seconds */
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tim += tim_p->tm_sec + (tim_p->tm_min * _SEC_IN_MINUTE) +
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(tim_p->tm_hour * _SEC_IN_HOUR);
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/* compute days in year */
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days += tim_p->tm_mday - 1;
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days += _DAYS_BEFORE_MONTH[tim_p->tm_mon];
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if (tim_p->tm_mon > 1 && _DAYS_IN_YEAR (tim_p->tm_year) == 366)
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days++;
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/* compute day of the year */
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tim_p->tm_yday = days;
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if (tim_p->tm_year > 10000
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|| tim_p->tm_year < -10000)
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{
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return (time_t) -1;
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}
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/* compute days in other years */
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if (tim_p->tm_year > 70)
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{
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for (year = 70; year < tim_p->tm_year; year++)
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days += _DAYS_IN_YEAR (year);
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}
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else if (tim_p->tm_year < 70)
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{
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for (year = 69; year > tim_p->tm_year; year--)
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days -= _DAYS_IN_YEAR (year);
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days -= _DAYS_IN_YEAR (year);
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}
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/* compute day of the week */
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if ((tim_p->tm_wday = (days + 4) % 7) < 0)
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tim_p->tm_wday += 7;
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/* compute total seconds */
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tim += (days * _SEC_IN_DAY);
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isdst = tim_p->tm_isdst;
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if (_daylight)
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{
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int y = tim_p->tm_year + YEAR_BASE;
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if (y == tz->__tzyear || __tzcalc_limits (y))
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{
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/* calculate start of dst in dst local time and
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start of std in both std local time and dst local time */
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time_t startdst_dst = tz->__tzrule[0].change
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- (time_t) tz->__tzrule[1].offset;
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time_t startstd_dst = tz->__tzrule[1].change
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- (time_t) tz->__tzrule[1].offset;
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time_t startstd_std = tz->__tzrule[1].change
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- (time_t) tz->__tzrule[0].offset;
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/* if the time is in the overlap between dst and std local times */
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if (tim >= startstd_std && tim < startstd_dst)
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; /* we let user decide or leave as -1 */
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else
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{
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isdst = (tz->__tznorth
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? (tim >= startdst_dst && tim < startstd_std)
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: (tim >= startdst_dst || tim < startstd_std));
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/* if user committed and was wrong, perform correction */
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if ((isdst ^ tim_p->tm_isdst) == 1)
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{
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/* we either subtract or add the difference between
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time zone offsets, depending on which way the user got it
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wrong. The diff is typically one hour, or 3600 seconds,
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and should fit in a 16-bit int, even though offset
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is a long to accomodate 12 hours. */
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int diff = (int) (tz->__tzrule[0].offset
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- tz->__tzrule[1].offset);
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if (!isdst)
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diff = -diff;
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tim_p->tm_sec += diff;
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validate_structure (tim_p);
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tim += diff; /* we also need to correct our current time calculation */
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}
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}
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}
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}
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/* add appropriate offset to put time in gmt format */
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if (isdst == 1)
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tim += (time_t) tz->__tzrule[1].offset;
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else /* otherwise assume std time */
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tim += (time_t) tz->__tzrule[0].offset;
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/* reset isdst flag to what we have calculated */
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tim_p->tm_isdst = isdst;
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return tim;
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}
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