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/*
* localtime_r.c
* Original Author: Adapted from tzcode maintained by Arthur David Olson.
*
* Converts the calendar time pointed to by tim_p into a broken-down time
* expressed as local time. Returns a pointer to a structure containing the
* broken-down time.
*/
#include <stdlib.h>
#include <time.h>
#define SECSPERMIN 60L
#define MINSPERHOUR 60L
#define HOURSPERDAY 24L
#define SECSPERHOUR (SECSPERMIN * MINSPERHOUR)
#define SECSPERDAY (SECSPERHOUR * HOURSPERDAY)
#define DAYSPERWEEK 7
#define MONSPERYEAR 12
#define YEAR_BASE 1900
#define EPOCH_YEAR 1970
#define EPOCH_WDAY 4
#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
static _CONST int mon_lengths[2][MONSPERYEAR] = {
{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
} ;
static _CONST int year_lengths[2] = {
365,
366
} ;
struct tm *
_DEFUN (localtime_r, (tim_p, res),
_CONST time_t * tim_p _AND
struct tm *res)
{
long days, rem;
int y;
int yleap;
_CONST int *ip;
days = ((long) *tim_p) / SECSPERDAY;
rem = ((long) *tim_p) % SECSPERDAY;
while (rem < 0)
{
rem += SECSPERDAY;
--days;
}
while (rem >= SECSPERDAY)
{
rem -= SECSPERDAY;
++days;
}
/* compute hour, min, and sec */
res->tm_hour = (int) (rem / SECSPERHOUR);
rem %= SECSPERHOUR;
res->tm_min = (int) (rem / SECSPERMIN);
res->tm_sec = (int) (rem % SECSPERMIN);
/* compute day of week */
if ((res->tm_wday = ((EPOCH_WDAY + days) % DAYSPERWEEK)) < 0)
res->tm_wday += DAYSPERWEEK;
/* compute year & day of year */
y = EPOCH_YEAR;
if (days >= 0)
{
for (;;)
{
yleap = isleap(y);
if (days < year_lengths[yleap])
break;
y++;
days -= year_lengths[yleap];
}
}
else
{
do
{
--y;
yleap = isleap(y);
days += year_lengths[yleap];
} while (days < 0);
}
res->tm_year = y - YEAR_BASE;
res->tm_yday = days;
ip = mon_lengths[yleap];
for (res->tm_mon = 0; days >= ip[res->tm_mon]; ++res->tm_mon)
days -= ip[res->tm_mon];
res->tm_mday = days + 1;
/* set daylight saving time flag */
res->tm_isdst = -1;
return (res);
}
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