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/*
* caljulian - determine the Julian date from an NTP time.
*/
#include <sys/types.h>
#include "ntp_types.h"
#include "ntp_calendar.h"
#include "ntp_stdlib.h"
/*
* calmonthtab - month start offsets from the beginning of a cycle.
*/
static u_short calmonthtab[12] = {
0, /* March */
MAR, /* April */
(MAR+APR), /* May */
(MAR+APR+MAY), /* June */
(MAR+APR+MAY+JUN), /* July */
(MAR+APR+MAY+JUN+JUL), /* August */
(MAR+APR+MAY+JUN+JUL+AUG), /* September */
(MAR+APR+MAY+JUN+JUL+AUG+SEP), /* October */
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT), /* November */
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV), /* December */
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC), /* January */
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC+JAN), /* February */
};
/*
* caldaytab - calendar year start day offsets
*/
static u_short caldaytab[YEARSPERCYCLE] = {
(DAYSPERYEAR - (JAN + FEB)),
((DAYSPERYEAR * 2) - (JAN + FEB)),
((DAYSPERYEAR * 3) - (JAN + FEB)),
((DAYSPERYEAR * 4) - (JAN + FEB)),
};
void
caljulian(ntptime, jt)
u_long ntptime;
register struct calendar *jt;
{
register int i;
register u_long nt;
register u_short snt;
register int cyear;
/*
* Find the start of the cycle this is in.
*/
nt = ntptime;
if (nt >= MAR1988) {
cyear = CYCLE22;
nt -= MAR1988;
} else {
cyear = 0;
nt -= MAR1900;
}
while (nt >= SECSPERCYCLE) {
nt -= SECSPERCYCLE;
cyear++;
}
/*
* Seconds, minutes and hours are too hard to do without
* divides, so we don't.
*/
jt->second = nt % SECSPERMIN;
nt /= SECSPERMIN; /* nt in minutes */
jt->minute = nt % MINSPERHR;
snt = nt / MINSPERHR; /* snt in hours */
jt->hour = snt % HRSPERDAY;
snt /= HRSPERDAY; /* nt in days */
/*
* snt is now the number of days into the cycle, from 0 to 1460.
*/
cyear <<= 2;
if (snt < caldaytab[0]) {
jt->yearday = snt + JAN + FEBLEAP + 1; /* first year is leap */
} else {
for (i = 1; i < YEARSPERCYCLE; i++)
if (snt < caldaytab[i])
break;
jt->yearday = snt - caldaytab[i-1] + 1;
cyear += i;
}
jt->year = cyear + 1900;
/*
* One last task, to compute the month and day. Normalize snt to
* a day within a cycle year.
*/
while (snt >= DAYSPERYEAR)
snt -= DAYSPERYEAR;
for (i = 0; i < 11; i++)
if (snt < calmonthtab[i+1])
break;
if (i > 9)
jt->month = i - 9; /* January or February */
else
jt->month = i + 3; /* March through December */
jt->monthday = snt - calmonthtab[i] + 1;
}
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