Pileus Git - lackey/blob - src/util.c

   1 /* Time Keeping Bugs Abound! */
   2
   3 #include <stdio.h>
   4 #include <time.h>
   5
   6 #include "util.h"
   7
   8 /* Time functions */
   9 int is_leap_year(year_t year)
  10 {
  11         return (year % 400 == 0) ? 1 :
  12                (year % 100 == 0) ? 0 :
  13                (year % 4   == 0) ? 1 : 0;
  14 }
  15
  16 int days_in_year(year_t year)
  17 {
  18         return 365 + is_leap_year(year);
  19 }
  20
  21 int days_in_month(year_t year, month_t month)
  22 {
  23         static int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
  24         int days = mdays[month];
  25         if (month == FEB)
  26                 days += is_leap_year(year);
  27         return days;
  28 }
  29
  30 int weeks_in_month(year_t year, month_t month)
  31 {
  32         int start = start_of_month(year, month);
  33         int days  = days_in_month(year, month);
  34         return ((start + days)-1) / 7 + 1;
  35 }
  36
  37 wday_t day_of_week(year_t year, month_t month, day_t day)
  38 {
  39         static int tmp[] = {0, 3, 2, 5, 0, 3,
  40                             5, 1, 4, 6, 2, 4};
  41         if (month < 3)
  42                 year--;
  43         int start = year + year / 4
  44                          - year / 100
  45                          + year / 400
  46                          + tmp[month];
  47         return (start + day) % 7;
  48 }
  49
  50 wday_t start_of_month(year_t year, month_t month)
  51 {
  52         return day_of_week(year, month, 1);
  53 }
  54
  55 void add_days(year_t *year, month_t *month, day_t *day, int days)
  56 {
  57         time_t time = mktime(&(struct tm){
  58                         .tm_year = *year-1900,
  59                         .tm_mon  = *month,
  60                         .tm_mday = *day+1,
  61                         .tm_hour = 12});
  62         time  += days*24*60*60;
  63         struct tm *tm = localtime(&time);
  64         *year  = tm->tm_year+1900;
  65         *month = tm->tm_mon;
  66         *day   = tm->tm_mday-1;
  67 }
  68
  69 /* Debug functions */
  70 const char *month_to_str(month_t month)
  71 {
  72         static const char *map[] =
  73                 { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  74                   "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", };
  75         return map[month%12];
  76 }
  77 const char *month_to_string(month_t month)
  78 {
  79         static const char *map[] =
  80                 { "January",   "February", "March",    "April",
  81                   "May",       "June",     "July",     "August",
  82                   "September", "October",  "November", "December" };
  83         return map[month%12];
  84 }
  85
  86 const char *day_to_st(wday_t day)
  87 {
  88         static const char *map[] =
  89                 { "Su","Mo", "Tu", "We", "Th", "Fr", "Sa" };
  90         return map[day%7];
  91 }
  92 const char *day_to_str(wday_t day)
  93 {
  94         static const char *map[] =
  95                 { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
  96         return map[day%7];
  97 }
  98 const char *day_to_string(wday_t day)
  99 {
 100         static const char *map[] =
 101                 { "Sunday",   "Monday", "Tuesday", "Wednesday",
 102                   "Thursday", "Friday", "Saturday" };
 103         return map[day%7];
 104 }
 105
 106 /* Test functions */
 107 void test_time(void)
 108 {
 109         printf("Year Month     Start Weeks Days\n");
 110         for (int y = 2012; y <= 2012; y++)
 111         for (int m = JAN;  m <= DEC;  m++) {
 112                 printf("%-5d",  y);
 113                 printf("%-10s", month_to_string(m));
 114                 printf("%-6s",  day_to_str(start_of_month(y,m)));
 115                 printf("%-6d",  weeks_in_month(y,m));
 116                 printf("%-2d",  days_in_month(y,m));
 117                 printf("\n");
 118         }
 119 }