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