diff options
Diffstat (limited to 'usr.sbin/xntpd/lib/caljulian.c')
| -rw-r--r-- | usr.sbin/xntpd/lib/caljulian.c | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/usr.sbin/xntpd/lib/caljulian.c b/usr.sbin/xntpd/lib/caljulian.c new file mode 100644 index 0000000..92d6d74 --- /dev/null +++ b/usr.sbin/xntpd/lib/caljulian.c @@ -0,0 +1,105 @@ +/* caljulian.c,v 3.1 1993/07/06 01:08:00 jbj Exp + * 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; +} |
