/contrib/ntp/libntp/caljulian.c
https://bitbucket.org/freebsd/freebsd-head/ · C · 146 lines · 94 code · 16 blank · 36 comment · 9 complexity · 4309566f8d6b855fd131435c0cb38bbf MD5 · raw file
- /*
- * 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"
- #include "ntp_fp.h"
- #if 0
- /*
- * calmonthtab - days-in-the-month table
- */
- static u_short calmonthtab[11] = {
- JAN,
- FEB,
- MAR,
- APR,
- MAY,
- JUN,
- JUL,
- AUG,
- SEP,
- OCT,
- NOV
- };
- void
- caljulian(
- u_long ntptime,
- register struct calendar *jt
- )
- {
- u_long ntp_day;
- u_long minutes;
- /*
- * Absolute, zero-adjusted Christian era day, starting from the
- * mythical day 12/1/1 BC
- */
- u_long acez_day;
- u_long d400; /* Days into a Gregorian cycle */
- u_long d100; /* Days into a normal century */
- u_long d4; /* Days into a 4-year cycle */
- u_long n400; /* # of Gregorian cycles */
- u_long n100; /* # of normal centuries */
- u_long n4; /* # of 4-year cycles */
- u_long n1; /* # of years into a leap year */
- /* cycle */
- /*
- * Do the easy stuff first: take care of hh:mm:ss, ignoring leap
- * seconds
- */
- jt->second = (u_char)(ntptime % SECSPERMIN);
- minutes = ntptime / SECSPERMIN;
- jt->minute = (u_char)(minutes % MINSPERHR);
- jt->hour = (u_char)((minutes / MINSPERHR) % HRSPERDAY);
- /*
- * Find the day past 1900/01/01 00:00 UTC
- */
- ntp_day = ntptime / SECSPERDAY;
- acez_day = DAY_NTP_STARTS + ntp_day - 1;
- n400 = acez_day/GREGORIAN_CYCLE_DAYS;
- d400 = acez_day%GREGORIAN_CYCLE_DAYS;
- n100 = d400 / GREGORIAN_NORMAL_CENTURY_DAYS;
- d100 = d400 % GREGORIAN_NORMAL_CENTURY_DAYS;
- n4 = d100 / GREGORIAN_NORMAL_LEAP_CYCLE_DAYS;
- d4 = d100 % GREGORIAN_NORMAL_LEAP_CYCLE_DAYS;
- n1 = d4 / DAYSPERYEAR;
- /*
- * Calculate the year and year-of-day
- */
- jt->yearday = (u_short)(1 + d4%DAYSPERYEAR);
- jt->year = (u_short)(400*n400 + 100*n100 + n4*4 + n1);
- if (n100 == 4 || n1 == 4)
- {
- /*
- * If the cycle year ever comes out to 4, it must be December 31st
- * of a leap year.
- */
- jt->month = 12;
- jt->monthday = 31;
- jt->yearday = 366;
- }
- else
- {
- /*
- * Else, search forwards through the months to get the right month
- * and date.
- */
- int monthday;
- jt->year++;
- monthday = jt->yearday;
- for (jt->month=0;jt->month<11; jt->month++)
- {
- int t;
- t = monthday - calmonthtab[jt->month];
- if (jt->month == 1 && is_leapyear(jt->year))
- t--;
- if (t > 0)
- monthday = t;
- else
- break;
- }
- jt->month++;
- jt->monthday = (u_char) monthday;
- }
- }
- #else
- /* Updated 2003-12-30 TMa
- Uses common code with the *prettydate functions to convert an ntp
- seconds count into a calendar date.
- Will handle ntp epoch wraparound as long as the underlying os/library
- does so for the unix epoch, i.e. works after 2038.
- */
- void
- caljulian(
- u_long ntptime,
- register struct calendar *jt
- )
- {
- struct tm *tm;
- tm = ntp2unix_tm(ntptime, 0);
- jt->hour = (u_char) tm->tm_hour;
- jt->minute = (u_char) tm->tm_min;
- jt->month = (u_char) (tm->tm_mon + 1);
- jt->monthday = (u_char) tm->tm_mday;
- jt->second = (u_char) tm->tm_sec;
- jt->year = (u_short) (tm->tm_year + 1900);
- jt->yearday = (u_short) (tm->tm_yday + 1); /* Assumes tm_yday starts with day 0! */
- }
- #endif