contrib/ntp/libntp/calyearstart.c

   1 /*
   2  * calyearstart - determine the NTP time at midnight of January 1 in
   3  *                the year of the given date.
   4  */
   5 #include <config.h>
   6 #include <sys/types.h>
   7
   8 #include "ntp_types.h"
   9 #include "ntp_calendar.h"
  10 #include "ntp_stdlib.h"
  11 #include "ntp_assert.h"
  12
  13 /*
  14  * Juergen Perlinger, 2010-05-02
  15  *
  16  * Redone in terms of the calendar functions. It's rather simple:
  17  * - expand the NTP time stamp
  18  * - split into days and seconds since midnight, dropping the partial day
  19  * - get full number of days before year start in NTP epoch
  20  * - convert to seconds, truncated to 32 bits.
  21  */
  22 u_int32
  23 calyearstart(u_int32 ntptime, const time_t *pivot)
  24 {
  25         u_int32      ndays; /* elapsed days since NTP starts */
  26         vint64       vlong;
  27         ntpcal_split split;
  28
  29         vlong = ntpcal_ntp_to_ntp(ntptime, pivot);
  30         split = ntpcal_daysplit(&vlong);
  31         ndays = ntpcal_rd_to_ystart(split.hi + DAY_NTP_STARTS)
  32               - DAY_NTP_STARTS;
  33
  34         return (u_int32)(ndays * SECSPERDAY);
  35 }
  36
  37 /*
  38  * calmonthstart - get NTP time at midnight of the first day of the
  39  * current month.
  40  */
  41 u_int32
  42 calmonthstart(u_int32 ntptime, const time_t *pivot)
  43 {
  44         u_int32      ndays; /* elapsed days since NTP starts */
  45         vint64       vlong;
  46         ntpcal_split split;
  47
  48         vlong = ntpcal_ntp_to_ntp(ntptime, pivot);
  49         split = ntpcal_daysplit(&vlong);
  50         ndays = ntpcal_rd_to_mstart(split.hi + DAY_NTP_STARTS)
  51               - DAY_NTP_STARTS;
  52
  53         return (u_int32)(ndays * SECSPERDAY);
  54 }
  55
  56 /*
  57  * calweekstart - get NTP time at midnight of the last monday on or
  58  * before the current date.
  59  */
  60 u_int32
  61 calweekstart(u_int32 ntptime, const time_t *pivot)
  62 {
  63         u_int32      ndays; /* elapsed days since NTP starts */
  64         vint64       vlong;
  65         ntpcal_split split;
  66
  67         vlong = ntpcal_ntp_to_ntp(ntptime, pivot);
  68         split = ntpcal_daysplit(&vlong);
  69         ndays = ntpcal_weekday_le(split.hi + DAY_NTP_STARTS, CAL_MONDAY)
  70               - DAY_NTP_STARTS;
  71
  72         return (u_int32)(ndays * SECSPERDAY);
  73 }
  74
  75 /*
  76  * caldaystart - get NTP time at midnight of the current day.
  77  */
  78 u_int32
  79 caldaystart(u_int32 ntptime, const time_t *pivot)
  80 {
  81         vint64       vlong;
  82         ntpcal_split split;
  83
  84         vlong = ntpcal_ntp_to_ntp(ntptime, pivot);
  85         split = ntpcal_daysplit(&vlong);
  86
  87         return ntptime - split.lo;
  88 }