dist/ntp/libntp/ymd2yd.c

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * ymd2yd - compute the date in the year from y/m/d
   5  */
   6
   7 #include "ntp_fp.h"
   8 #include "ntp_unixtime.h"
   9 #include "ntp_stdlib.h"
  10
  11 /*
  12  * Tables to compute the day of year from yyyymmdd timecode.
  13  * Viva la leap.
  14  */
  15 static int day1tab[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  16 static int day2tab[] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  17
  18 int
  19 ymd2yd(
  20         int y,
  21         int m,
  22         int d
  23         )
  24 {
  25         int i, *t;
  26
  27         if (m < 1 || m > 12 || d < 1)
  28                 return (-1);
  29
  30         if (((y%4 == 0) && (y%100 != 0)) || (y%400 == 0))
  31                 t = day2tab;    /* leap year */
  32         else
  33                 t = day1tab;    /* not a leap year */
  34         if (d > t[m - 1])
  35                 return (-1);
  36         for (i = 0; i < m - 1; i++)
  37                 d += t[i];
  38         return d;
  39 }