/*

* mktime - convert local time into calendar time

*/

/* $Header$ */

/* Michael A. Temari <temari@ix.netcom.com> 03/01/96 */

/* - fixed bug is structure fixup code */

#include <time.h>

#include <limits.h>

#include "loc_time.h"

/* The code assumes that unsigned long can be converted to time_t.

* A time_t should not be wider than unsigned long, since this would mean

* that the check for overflow at the end could fail.

*/

time_t

mktime(register struct tm *timep)

{

register long day, year;

register int tm_year;

int yday, month;

register unsigned long seconds;

int overflow;

unsigned dst;

timep->tm_min += timep->tm_sec / 60;

timep->tm_sec %= 60;

if (timep->tm_sec < 0) {

timep->tm_sec += 60;

timep->tm_min--;

}

timep->tm_hour += timep->tm_min / 60;

timep->tm_min = timep->tm_min % 60;

if (timep->tm_min < 0) {

timep->tm_min += 60;

timep->tm_hour--;

}

day = timep->tm_hour / 24;

timep->tm_hour= timep->tm_hour % 24;

if (timep->tm_hour < 0) {

timep->tm_hour += 24;

day--;

}

timep->tm_year += timep->tm_mon / 12;

timep->tm_mon %= 12;

if (timep->tm_mon < 0) {

timep->tm_mon += 12;

timep->tm_year--;

}

day += (timep->tm_mday - 1);

while (day < 0) {

if(--timep->tm_mon < 0) {

timep->tm_year--;

timep->tm_mon = 11;

}

day += _ytab[LEAPYEAR(YEAR0 + timep->tm_year)][timep->tm_mon];

}

while (day >= _ytab[LEAPYEAR(YEAR0 + timep->tm_year)][timep->tm_mon]) {

day -= _ytab[LEAPYEAR(YEAR0 + timep->tm_year)][timep->tm_mon];

if (++(timep->tm_mon) == 12) {

timep->tm_mon = 0;

timep->tm_year++;

}

}

timep->tm_mday = day + 1;

_tzset(); /* set timezone and dst info */

year = EPOCH_YR;

if (timep->tm_year < year - YEAR0) return (time_t)-1;

seconds = 0;

day = 0; /* means days since day 0 now */

overflow = 0;

/* Assume that when day becomes negative, there will certainly

* be overflow on seconds.

* The check for overflow needs not to be done for leapyears

* divisible by 400.

* The code only works when year (1970) is not a leapyear.

*/

#if EPOCH_YR != 1970

#error EPOCH_YR != 1970

#endif

tm_year = timep->tm_year + YEAR0;

if (LONG_MAX / 365 < tm_year - year) overflow++;

day = (tm_year - year) * 365;

if (LONG_MAX - day < (tm_year - year) / 4 + 1) overflow++;

day += (tm_year - year) / 4

+ ((tm_year % 4) && tm_year % 4 < year % 4);

day -= (tm_year - year) / 100

+ ((tm_year % 100) && tm_year % 100 < year % 100);

day += (tm_year - year) / 400

+ ((tm_year % 400) && tm_year % 400 < year % 400);

yday = month = 0;

while (month < timep->tm_mon) {

yday += _ytab[LEAPYEAR(tm_year)][month];

month++;

}

yday += (timep->tm_mday - 1);

if (day + yday < 0) overflow++;

day += yday;

timep->tm_yday = yday;

timep->tm_wday = (day + 4) % 7; /* day 0 was thursday (4) */

seconds = ((timep->tm_hour * 60L) + timep->tm_min) * 60L + timep->tm_sec;

if ((TIME_MAX - seconds) / SECS_DAY < day) overflow++;

seconds += day * SECS_DAY;

/* Now adjust according to timezone and daylight saving time */

if (((_timezone > 0) && (TIME_MAX - _timezone < seconds))

|| ((_timezone < 0) && (seconds < -_timezone)))

overflow++;

seconds += _timezone;

if (timep->tm_isdst < 0)

dst = _dstget(timep);

else if (timep->tm_isdst)

dst = _dst_off;

else dst = 0;

if (dst > seconds) overflow++; /* dst is always non-negative */

seconds -= dst;

if (overflow) return (time_t)-1;

if ((time_t)seconds != seconds) return (time_t)-1;

return (time_t)seconds;

}