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/*
* mktime.c
* Original Author: G. Haley
*
* Converts the broken-down time, expressed as local time, in the structure
* pointed to by tim_p into a calendar time value. The original values of the
* tm_wday and tm_yday fields of the structure are ignored, and the original
* values of the other fields have no restrictions. On successful completion
* the fields of the structure are set to represent the specified calendar
* time. Returns the specified calendar time. If the calendar time can not be
* represented, returns the value (time_t) -1.
*/
/*
FUNCTION
<<mktime>>---convert time to arithmetic representation
INDEX
mktime
ANSI_SYNOPSIS
#include <time.h>
time_t mktime(struct tm *<[timp]>);
TRAD_SYNOPSIS
#include <time.h>
time_t mktime(<[timp]>)
struct tm *<[timp]>;
DESCRIPTION
<<mktime>> assumes the time at <[timp]> is a local time, and converts
its representation from the traditional representation defined by
<<struct tm>> into a representation suitable for arithmetic.
<<localtime>> is the inverse of <<mktime>>.
RETURNS
If the contents of the structure at <[timp]> do not form a valid
calendar time representation, the result is <<-1>>. Otherwise, the
result is the time, converted to a <<time_t>> value.
PORTABILITY
ANSI C requires <<mktime>>.
<<mktime>> requires no supporting OS subroutines.
*/
#include <stdlib.h>
#include <time.h>
#define _SEC_IN_MINUTE 60
#define _SEC_IN_HOUR 3600
#define _SEC_IN_DAY 86400
static _CONST int DAYS_IN_MONTH[12] =
{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
#define _DAYS_IN_MONTH(x) ((x == 1) ? days_in_feb : DAYS_IN_MONTH[x])
static _CONST int _DAYS_BEFORE_MONTH[12] =
{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
#define _ISLEAP(y) (((y) % 4) == 0 && (((y) % 100) != 0 || (((y)+1900) % 400) == 0))
#define _DAYS_IN_YEAR(year) (_ISLEAP(year) ? 366 : 365)
static void
validate_structure (tim_p)
struct tm *tim_p;
{
div_t res;
int days_in_feb = 28;
/* calculate time & date to account for out of range values */
if (tim_p->tm_sec < 0 || tim_p->tm_sec > 59)
{
res = div (tim_p->tm_sec, 60);
tim_p->tm_min += res.quot;
if ((tim_p->tm_sec = res.rem) < 0)
{
tim_p->tm_sec += 60;
--tim_p->tm_min;
}
}
if (tim_p->tm_min < 0 || tim_p->tm_min > 59)
{
res = div (tim_p->tm_min, 60);
tim_p->tm_hour += res.quot;
if ((tim_p->tm_min = res.rem) < 0)
{
tim_p->tm_min += 60;
--tim_p->tm_hour;
}
}
if (tim_p->tm_hour < 0 || tim_p->tm_hour > 23)
{
res = div (tim_p->tm_hour, 24);
tim_p->tm_mday += res.quot;
if ((tim_p->tm_hour = res.rem) < 0)
{
tim_p->tm_hour += 24;
--tim_p->tm_mday;
}
}
if (tim_p->tm_mon > 11)
{
res = div (tim_p->tm_mon, 12);
tim_p->tm_year += res.quot;
if ((tim_p->tm_mon = res.rem) < 0)
{
tim_p->tm_mon += 12;
--tim_p->tm_year;
}
}
if (_DAYS_IN_YEAR (tim_p->tm_year) == 366)
days_in_feb = 29;
if (tim_p->tm_mday <= 0)
{
while (tim_p->tm_mday <= 0)
{
if (--tim_p->tm_mon == -1)
{
tim_p->tm_year--;
tim_p->tm_mon = 11;
days_in_feb =
((_DAYS_IN_YEAR (tim_p->tm_year) == 366) ?
29 : 28);
}
tim_p->tm_mday += _DAYS_IN_MONTH (tim_p->tm_mon);
}
}
else
{
while (tim_p->tm_mday > _DAYS_IN_MONTH (tim_p->tm_mon))
{
tim_p->tm_mday -= _DAYS_IN_MONTH (tim_p->tm_mon);
if (++tim_p->tm_mon == 12)
{
tim_p->tm_year++;
tim_p->tm_mon = 0;
days_in_feb =
((_DAYS_IN_YEAR (tim_p->tm_year) == 366) ?
29 : 28);
}
}
}
}
time_t
mktime (tim_p)
struct tm *tim_p;
{
time_t tim = 0;
long days = 0;
int year;
/* validate structure */
validate_structure (tim_p);
/* compute hours, minutes, seconds */
tim += tim_p->tm_sec + (tim_p->tm_min * _SEC_IN_MINUTE) +
(tim_p->tm_hour * _SEC_IN_HOUR);
/* compute days in year */
days += tim_p->tm_mday - 1;
days += _DAYS_BEFORE_MONTH[tim_p->tm_mon];
if (tim_p->tm_mon > 1 && _DAYS_IN_YEAR (tim_p->tm_year) == 366)
days++;
/* compute day of the year */
tim_p->tm_yday = days;
if (tim_p->tm_year > 10000
|| tim_p->tm_year < -10000)
{
return (time_t) -1;
}
/* compute days in other years */
if (tim_p->tm_year > 70)
{
for (year = 70; year < tim_p->tm_year; year++)
days += _DAYS_IN_YEAR (year);
}
else if (tim_p->tm_year < 70)
{
for (year = 69; year > tim_p->tm_year; year--)
days -= _DAYS_IN_YEAR (year);
days -= _DAYS_IN_YEAR (year);
}
/* compute day of the week */
if ((tim_p->tm_wday = (days + 4) % 7) < 0)
tim_p->tm_wday += 7;
/* compute total seconds */
tim += (days * _SEC_IN_DAY);
return tim;
}
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