dist/ntp/libntp/caltontp.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * caltontp - convert a date to 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
  12 u_long
  13 caltontp(
  14         register const struct calendar *jt
  15         )
  16 {
  17     u_long ace_days;                         /* absolute Christian Era days */
  18     u_long ntp_days;
  19     int    prior_years;
  20     u_long ntp_time;
  21
  22     /*
  23      * First convert today's date to absolute days past 12/1/1 BC
  24      */
  25     prior_years = jt->year-1;
  26     ace_days = jt->yearday                   /* days this year */
  27         +(DAYSPERYEAR*prior_years)           /* plus days in previous years */
  28         +(prior_years/4)                     /* plus prior years's leap days */
  29         -(prior_years/100)                   /* minus leapless century years */
  30         +(prior_years/400);                  /* plus leapful Gregorian yrs */
  31
  32     /*
  33      * Subtract out 1/1/1900, the beginning of the NTP epoch
  34      */
  35     ntp_days = ace_days - DAY_NTP_STARTS;
  36
  37     /*
  38      * Do the obvious:
  39      */
  40     ntp_time =
  41         ntp_days*SECSPERDAY+SECSPERMIN*(MINSPERHR*jt->hour + jt->minute);
  42
  43     return ntp_time;
  44 }