dist/ntp/libntp/caljulian.c

   1 /*      $NetBSD: caljulian.c,v 1.2 2003/12/04 16:23:36 drochner Exp $   */
   2
   3 /*
   4  * caljulian - determine the Julian date from an NTP time.
   5  */
   6 #include <sys/types.h>
   7
   8 #include "ntp_types.h"
   9 #include "ntp_calendar.h"
  10 #include "ntp_stdlib.h"
  11 #include "ntp_fp.h"
  12
  13 #if 0
  14 /*
  15  * calmonthtab - days-in-the-month table
  16  */
  17 static u_short calmonthtab[11] = {
  18         JAN,
  19         FEB,
  20         MAR,
  21         APR,
  22         MAY,
  23         JUN,
  24         JUL,
  25         AUG,
  26         SEP,
  27         OCT,
  28         NOV
  29 };
  30
  31 void
  32 caljulian(
  33         u_long                          ntptime,
  34         register struct calendar        *jt
  35         )
  36 {
  37         u_long ntp_day;
  38         u_long minutes;
  39         /*
  40          * Absolute, zero-adjusted Christian era day, starting from the
  41          * mythical day 12/1/1 BC
  42          */
  43         u_long acez_day;
  44
  45         u_long d400;                             /* Days into a Gregorian cycle */
  46         u_long d100;                             /* Days into a normal century */
  47         u_long d4;                                       /* Days into a 4-year cycle */
  48         u_long n400;                             /* # of Gregorian cycles */
  49         u_long n100;                             /* # of normal centuries */
  50         u_long n4;                                       /* # of 4-year cycles */
  51         u_long n1;                                       /* # of years into a leap year */
  52                                                  /*   cycle */
  53
  54         /*
  55          * Do the easy stuff first: take care of hh:mm:ss, ignoring leap
  56          * seconds
  57          */
  58         jt->second = (u_char)(ntptime % SECSPERMIN);
  59         minutes    = ntptime / SECSPERMIN;
  60         jt->minute = (u_char)(minutes % MINSPERHR);
  61         jt->hour   = (u_char)((minutes / MINSPERHR) % HRSPERDAY);
  62
  63         /*
  64          * Find the day past 1900/01/01 00:00 UTC
  65          */
  66         ntp_day = ntptime / SECSPERDAY;
  67         acez_day = DAY_NTP_STARTS + ntp_day - 1;
  68         n400     = acez_day/GREGORIAN_CYCLE_DAYS;
  69         d400     = acez_day%GREGORIAN_CYCLE_DAYS;
  70         n100     = d400 / GREGORIAN_NORMAL_CENTURY_DAYS;
  71         d100     = d400 % GREGORIAN_NORMAL_CENTURY_DAYS;
  72         n4               = d100 / GREGORIAN_NORMAL_LEAP_CYCLE_DAYS;
  73         d4               = d100 % GREGORIAN_NORMAL_LEAP_CYCLE_DAYS;
  74         n1               = d4 / DAYSPERYEAR;
  75
  76         /*
  77          * Calculate the year and year-of-day
  78          */
  79         jt->yearday = (u_short)(1 + d4%DAYSPERYEAR);
  80         jt->year        = (u_short)(400*n400 + 100*n100 + n4*4 + n1);
  81
  82         if (n100 == 4 || n1 == 4)
  83         {
  84         /*
  85          * If the cycle year ever comes out to 4, it must be December 31st
  86          * of a leap year.
  87          */
  88         jt->month        = 12;
  89         jt->monthday = 31;
  90         jt->yearday  = 366;
  91         }
  92         else
  93         {
  94         /*
  95          * Else, search forwards through the months to get the right month
  96          * and date.
  97          */
  98         int monthday;
  99
 100         jt->year++;
 101         monthday = jt->yearday;
 102
 103         for (jt->month=0;jt->month<11; jt->month++)
 104         {
 105                 int t;
 106
 107                 t = monthday - calmonthtab[jt->month];
 108                 if (jt->month == 1 && is_leapyear(jt->year))
 109                 t--;
 110
 111                 if (t > 0)
 112                 monthday = t;
 113                 else
 114                 break;
 115         }
 116         jt->month++;
 117         jt->monthday = (u_char) monthday;
 118         }
 119 }
 120 #else
 121
 122 /* Updated 2003-12-30 TMa
 123
 124    Uses common code with the *prettydate functions to convert an ntp
 125    seconds count into a calendar date.
 126    Will handle ntp epoch wraparound as long as the underlying os/library
 127    does so for the unix epoch, i.e. works after 2038.
 128 */
 129
 130 void
 131 caljulian(
 132         u_long                          ntptime,
 133         register struct calendar        *jt
 134         )
 135 {
 136         struct tm *tm;
 137
 138         tm = ntp2unix_tm(ntptime, 0);
 139
 140         jt->hour = (u_char) tm->tm_hour;
 141         jt->minute = (u_char) tm->tm_min;
 142         jt->month = (u_char) (tm->tm_mon + 1);
 143         jt->monthday = (u_char) tm->tm_mday;
 144         jt->second = (u_char) tm->tm_sec;
 145         jt->year = (u_short) (tm->tm_year + 1900);
 146         jt->yearday = (u_short) (tm->tm_yday + 1);  /* Assumes tm_yday starts with day 0! */
 147 }
 148 #endif