root/ext/date/lib/dow.c

DEFINITIONS

1. positive_mod
2. century_value
3. timelib_day_of_week_ex
4. timelib_day_of_week
5. timelib_iso_day_of_week
6. timelib_day_of_year
7. timelib_days_in_month
8. timelib_isoweek_from_date
9. timelib_daynr_from_weeknr
10. timelib_valid_time
11. timelib_valid_date
12. main

   1 /*
   2  * The MIT License (MIT)
   3  *
   4  * Copyright (c) 2015 Derick Rethans
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24 
  25 #include "timelib.h"
  26 
  27 static int m_table_common[13] = { -1, 0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5 }; /* 1 = jan */
  28 static int m_table_leap[13] =   { -1, 6, 2, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5 }; /* 1 = jan */
  29 
  30 static timelib_sll positive_mod(timelib_sll x, timelib_sll y)
  31 {
  32         timelib_sll tmp;
  33 
  34         tmp = x % y;
  35         if (tmp < 0) {
  36                 tmp += y;
  37         }
  38 
  39         return tmp;
  40 }
  41 
  42 static timelib_sll century_value(timelib_sll j)
  43 {
  44         return 6 - positive_mod(j, 4) * 2;
  45 }
  46 
  47 static timelib_sll timelib_day_of_week_ex(timelib_sll y, timelib_sll m, timelib_sll d, int iso)
  48 {
  49         timelib_sll c1, y1, m1, dow;
  50 
  51         /* Only valid for Gregorian calendar, commented out as we don't handle
  52          * Julian calendar. We just return the 'wrong' day of week to be
  53          * consistent. */
  54         c1 = century_value(y / 100);
  55         y1 = positive_mod(y, 100);
  56         m1 = timelib_is_leap(y) ? m_table_leap[m] : m_table_common[m];
  57         dow = positive_mod((c1 + y1 + m1 + (y1 / 4) + d), 7);
  58         if (iso) {
  59                 if (dow == 0) {
  60                         dow = 7;
  61                 }
  62         }
  63         return dow;
  64 }
  65 
  66 timelib_sll timelib_day_of_week(timelib_sll y, timelib_sll m, timelib_sll d)
  67 {
  68         return timelib_day_of_week_ex(y, m, d, 0);
  69 }
  70 
  71 timelib_sll timelib_iso_day_of_week(timelib_sll y, timelib_sll m, timelib_sll d)
  72 {
  73         return timelib_day_of_week_ex(y, m, d, 1);
  74 }
  75 
  76                                 /*     jan  feb  mar  apr  may  jun  jul  aug  sep  oct  nov  dec */
  77 static int d_table_common[13]  = {  0,   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334 };
  78 static int d_table_leap[13]    = {  0,   0,  31,  60,  91, 121, 152, 182, 213, 244, 274, 305, 335 };
  79 static int ml_table_common[13] = {  0,  31,  28,  31,  30,  31,  30,  31,  31,  30,  31,  30,  31 };
  80 static int ml_table_leap[13]   = {  0,  31,  29,  31,  30,  31,  30,  31,  31,  30,  31,  30,  31 };
  81 
  82 timelib_sll timelib_day_of_year(timelib_sll y, timelib_sll m, timelib_sll d)
  83 {
  84         return (timelib_is_leap(y) ? d_table_leap[m] : d_table_common[m]) + d - 1;
  85 }
  86 
  87 timelib_sll timelib_days_in_month(timelib_sll y, timelib_sll m)
  88 {
  89         return timelib_is_leap(y) ? ml_table_leap[m] : ml_table_common[m];
  90 }
  91 
  92 void timelib_isoweek_from_date(timelib_sll y, timelib_sll m, timelib_sll d, timelib_sll *iw, timelib_sll *iy)
  93 {
  94         int y_leap, prev_y_leap, doy, jan1weekday, weekday;
  95 
  96         y_leap = timelib_is_leap(y);
  97         prev_y_leap = timelib_is_leap(y-1);
  98         doy = timelib_day_of_year(y, m, d) + 1;
  99         if (y_leap && m > 2) {
 100                 doy++;
 101         }
 102         jan1weekday = timelib_day_of_week(y, 1, 1);
 103         weekday = timelib_day_of_week(y, m, d);
 104         if (weekday == 0) weekday = 7;
 105         if (jan1weekday == 0) jan1weekday = 7;
 106         /* Find if Y M D falls in YearNumber Y-1, WeekNumber 52 or 53 */
 107         if (doy <= (8 - jan1weekday) && jan1weekday > 4) {
 108                 *iy = y - 1;
 109                 if (jan1weekday == 5 || (jan1weekday == 6 && prev_y_leap)) {
 110                         *iw = 53;
 111                 } else {
 112                         *iw = 52;
 113                 }
 114         } else {
 115                 *iy = y;
 116         }
 117         /* 8. Find if Y M D falls in YearNumber Y+1, WeekNumber 1 */
 118         if (*iy == y) {
 119                 int i;
 120 
 121                 i = y_leap ? 366 : 365;
 122                 if ((i - (doy - y_leap)) < (4 - weekday)) {
 123                         *iy = y + 1;
 124                         *iw = 1;
 125                         return;
 126                 }
 127         }
 128         /* 9. Find if Y M D falls in YearNumber Y, WeekNumber 1 through 53 */
 129         if (*iy == y) {
 130                 int j;
 131 
 132                 j = doy + (7 - weekday) + (jan1weekday - 1);
 133                 *iw = j / 7;
 134                 if (jan1weekday > 4) {
 135                         *iw -= 1;
 136                 }
 137         }
 138 }
 139 
 140 timelib_sll timelib_daynr_from_weeknr(timelib_sll y, timelib_sll w, timelib_sll d)
 141 {
 142         timelib_sll dow, day;
 143 
 144         /* Figure out the dayofweek for y-1-1 */
 145         dow = timelib_day_of_week(y, 1, 1);
 146         /* then use that to figure out the offset for day 1 of week 1 */
 147         day = 0 - (dow > 4 ? dow - 7 : dow);
 148 
 149         /* Add weeks and days */
 150         return day + ((w - 1) * 7) + d;
 151 }
 152 
 153 int timelib_valid_time(timelib_sll h, timelib_sll i, timelib_sll s)
 154 {
 155         if (h < 0 || h > 23 || i < 0 || i > 59 || s < 0 || s > 59) {
 156                 return 0;
 157         }
 158         return 1;
 159 }
 160 
 161 int timelib_valid_date(timelib_sll y, timelib_sll m, timelib_sll d)
 162 {
 163         if (m < 1 || m > 12 || d < 1 || d > timelib_days_in_month(y, m)) {
 164                 return 0;
 165         }
 166         return 1;
 167 }
 168 #if 0
 169 int main(void)
 170 {
 171         printf("dow = %d\n", timelib_day_of_week(1978, 12, 22)); /* 5 */
 172         printf("dow = %d\n", timelib_day_of_week(2005,  2, 19)); /* 6 */
 173 }
 174 #endif