contrib/ntp/libntp/caljulian.c

   1 /*
   2  * caljulian - determine the Julian date from an NTP time.
   3  */
   4 #include <sys/types.h>
   5
   6 #include "ntp_types.h"
   7 #include "ntp_calendar.h"
   8 #include "ntp_stdlib.h"
   9 #include "ntp_fp.h"
  10
  11 #if 0
  12 /*
  13  * calmonthtab - days-in-the-month table
  14  */
  15 static u_short calmonthtab[11] = {
  16         JAN,
  17         FEB,
  18         MAR,
  19         APR,
  20         MAY,
  21         JUN,
  22         JUL,
  23         AUG,
  24         SEP,
  25         OCT,
  26         NOV
  27 };
  28
  29 void
  30 caljulian(
  31         u_long                          ntptime,
  32         register struct calendar        *jt
  33         )
  34 {
  35         u_long ntp_day;
  36         u_long minutes;
  37         /*
  38          * Absolute, zero-adjusted Christian era day, starting from the
  39          * mythical day 12/1/1 BC
  40          */
  41         u_long acez_day;
  42
  43         u_long d400;                             /* Days into a Gregorian cycle */
  44         u_long d100;                             /* Days into a normal century */
  45         u_long d4;                                       /* Days into a 4-year cycle */
  46         u_long n400;                             /* # of Gregorian cycles */
  47         u_long n100;                             /* # of normal centuries */
  48         u_long n4;                                       /* # of 4-year cycles */
  49         u_long n1;                                       /* # of years into a leap year */
  50                                                  /*   cycle */
  51
  52         /*
  53          * Do the easy stuff first: take care of hh:mm:ss, ignoring leap
  54          * seconds
  55          */
  56         jt->second = (u_char)(ntptime % SECSPERMIN);
  57         minutes    = ntptime / SECSPERMIN;
  58         jt->minute = (u_char)(minutes % MINSPERHR);
  59         jt->hour   = (u_char)((minutes / MINSPERHR) % HRSPERDAY);
  60
  61         /*
  62          * Find the day past 1900/01/01 00:00 UTC
  63          */
  64         ntp_day = ntptime / SECSPERDAY;
  65         acez_day = DAY_NTP_STARTS + ntp_day - 1;
  66         n400     = acez_day/GREGORIAN_CYCLE_DAYS;
  67         d400     = acez_day%GREGORIAN_CYCLE_DAYS;
  68         n100     = d400 / GREGORIAN_NORMAL_CENTURY_DAYS;
  69         d100     = d400 % GREGORIAN_NORMAL_CENTURY_DAYS;
  70         n4               = d100 / GREGORIAN_NORMAL_LEAP_CYCLE_DAYS;
  71         d4               = d100 % GREGORIAN_NORMAL_LEAP_CYCLE_DAYS;
  72         n1               = d4 / DAYSPERYEAR;
  73
  74         /*
  75          * Calculate the year and year-of-day
  76          */
  77         jt->yearday = (u_short)(1 + d4%DAYSPERYEAR);
  78         jt->year        = (u_short)(400*n400 + 100*n100 + n4*4 + n1);
  79
  80         if (n100 == 4 || n1 == 4)
  81         {
  82         /*
  83          * If the cycle year ever comes out to 4, it must be December 31st
  84          * of a leap year.
  85          */
  86         jt->month        = 12;
  87         jt->monthday = 31;
  88         jt->yearday  = 366;
  89         }
  90         else
  91         {
  92         /*
  93          * Else, search forwards through the months to get the right month
  94          * and date.
  95          */
  96         int monthday;
  97
  98         jt->year++;
  99         monthday = jt->yearday;
 100
 101         for (jt->month=0;jt->month<11; jt->month++)
 102         {
 103                 int t;
 104
 105                 t = monthday - calmonthtab[jt->month];
 106                 if (jt->month == 1 && is_leapyear(jt->year))
 107                 t--;
 108
 109                 if (t > 0)
 110                 monthday = t;
 111                 else
 112                 break;
 113         }
 114         jt->month++;
 115         jt->monthday = (u_char) monthday;
 116         }
 117 }
 118 #else
 119
 120 /* Updated 2003-12-30 TMa
 121
 122    Uses common code with the *prettydate functions to convert an ntp
 123    seconds count into a calendar date.
 124    Will handle ntp epoch wraparound as long as the underlying os/library
 125    does so for the unix epoch, i.e. works after 2038.
 126 */
 127
 128 void
 129 caljulian(
 130         u_long                          ntptime,
 131         register struct calendar        *jt
 132         )
 133 {
 134         struct tm *tm;
 135
 136         tm = ntp2unix_tm(ntptime, 0);
 137
 138         jt->hour = (u_char) tm->tm_hour;
 139         jt->minute = (u_char) tm->tm_min;
 140         jt->month = (u_char) (tm->tm_mon + 1);
 141         jt->monthday = (u_char) tm->tm_mday;
 142         jt->second = (u_char) tm->tm_sec;
 143         jt->year = (u_short) (tm->tm_year + 1900);
 144         jt->yearday = (u_short) (tm->tm_yday + 1);  /* Assumes tm_yday starts with day 0! */
 145 }
 146 #endif