64 lines
1.7 KiB
C
64 lines
1.7 KiB
C
/* $NetBSD: calleapwhen.c,v 1.4 1999/07/03 12:30:29 simonb Exp $ */
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/*
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* calleapwhen - determine the number of seconds to the next possible
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* leap occurance and the last one.
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*/
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#include <sys/types.h>
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#include "ntp_types.h"
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#include "ntp_calendar.h"
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#include "ntp_stdlib.h"
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/*
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* calleaptab - leaps occur at the end of December and June
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*/
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long calleaptab[10] = {
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-(JAN+FEBLEAP)*SECSPERDAY, /* leap previous to cycle */
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(MAR+APR+MAY+JUN)*SECSPERDAY, /* end of June */
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(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY, /* end of Dec */
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(MAR+APR+MAY+JUN)*SECSPERDAY + SECSPERYEAR,
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(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY + SECSPERYEAR,
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(MAR+APR+MAY+JUN)*SECSPERDAY + 2*SECSPERYEAR,
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(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY + 2*SECSPERYEAR,
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(MAR+APR+MAY+JUN)*SECSPERDAY + 3*SECSPERYEAR,
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(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC)*SECSPERDAY + 3*SECSPERYEAR,
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(MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC+JAN+FEBLEAP+MAR+APR+MAY+JUN)
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*SECSPERDAY + 3*SECSPERYEAR, /* next after current cycle */
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};
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void
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calleapwhen(ntpdate, leaplast, leapnext)
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u_long ntpdate;
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u_long *leaplast;
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u_long *leapnext;
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{
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register u_long dateincycle;
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register int i;
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/*
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* Find the offset from the start of the cycle
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*/
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dateincycle = ntpdate;
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if (dateincycle >= MAR1988)
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dateincycle -= MAR1988;
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else
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dateincycle -= MAR1900;
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while (dateincycle >= SECSPERCYCLE)
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dateincycle -= SECSPERCYCLE;
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/*
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* Find where we are with respect to the leap events.
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*/
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for (i = 1; i < 9; i++)
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if (dateincycle < (u_long)calleaptab[i])
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break;
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/*
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* i points at the next leap. Compute the last and the next.
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*/
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*leaplast = (u_long)((long)dateincycle - calleaptab[i-1]);
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*leapnext = (u_long)(calleaptab[i] - (long)dateincycle);
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}
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