NetBSD/dist/ntp/libntp/calleapwhen.c

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2000-03-29 16:38:44 +04:00
/* $NetBSD: calleapwhen.c,v 1.1.1.1 2000/03/29 12:38:49 simonb Exp $ */
/*
* calleapwhen - determine the number of seconds to the next possible
* leap occurance.
*/
#include <sys/types.h>
#include "ntp_types.h"
#include "ntp_calendar.h"
#include "ntp_stdlib.h"
/*
* calleaptab - leaps occur at the end of December and June
*/
long calleaptab[10] = {
-(JAN+FEBLEAP)*SECSPERDAY, /* leap previous to cycle */
(MAR+APR+MAY+JUN)*SECSPERDAY, /* end of June */
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY, /* end of Dec */
(MAR+APR+MAY+JUN)*SECSPERDAY + SECSPERYEAR,
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY + SECSPERYEAR,
(MAR+APR+MAY+JUN)*SECSPERDAY + 2*SECSPERYEAR,
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY + 2*SECSPERYEAR,
(MAR+APR+MAY+JUN)*SECSPERDAY + 3*SECSPERYEAR,
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY + 3*SECSPERYEAR,
(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC+JAN+FEBLEAP+MAR+APR+MAY+JUN)
*SECSPERDAY + 3*SECSPERYEAR, /* next after current cycle */
};
u_long
calleapwhen(
u_long ntpdate
)
{
register u_long dateincycle;
register int i;
/*
* Find the offset from the start of the cycle
*/
dateincycle = ntpdate;
if (dateincycle >= MAR1988)
dateincycle -= MAR1988;
else
dateincycle -= MAR1900;
while (dateincycle >= SECSPERCYCLE)
dateincycle -= SECSPERCYCLE;
/*
* Find where we are with respect to the leap events.
*/
for (i = 1; i < 9; i++)
if (dateincycle < (u_long)calleaptab[i])
break;
/*
* i points at the next leap. Compute the last and the next.
*/
return (u_long)(calleaptab[i] - (long)dateincycle);
}