dow.c   [plain text]

/*
   +----------------------------------------------------------------------+
   | PHP Version 5                                                        |
   +----------------------------------------------------------------------+
   | Copyright (c) 1997-2007 The PHP Group                                |
   +----------------------------------------------------------------------+
   | This source file is subject to version 3.01 of the PHP license,      |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | http://www.php.net/license/3_01.txt                                  |
   | If you did not receive a copy of the PHP license and are unable to   |
   | obtain it through the world-wide-web, please send a note to          |
   | license@php.net so we can mail you a copy immediately.               |
   +----------------------------------------------------------------------+
   | Authors: Derick Rethans <derick@derickrethans.nl>                    |
   +----------------------------------------------------------------------+
 */

/* $Id: dow.c,v 1.8.2.3.2.3 2007/01/01 09:35:48 sebastian Exp $ */

#include "timelib.h"

static int m_table_common[13] = { -1, 0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5 }; /* 1 = jan */
static int m_table_leap[13] =   { -1, 6, 2, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5 }; /* 1 = jan */

static timelib_sll century_value(timelib_sll j)
{
	timelib_sll i = j - 17;
	timelib_sll c = (4 - i * 2 + (i + 1) / 4) % 7;

	return c < 0 ? c + 7 : c;
}

static timelib_sll timelib_day_of_week_ex(timelib_sll y, timelib_sll m, timelib_sll d, int iso)
{
	timelib_sll c1, y1, m1, dow;

	/* Only valid for Gregorian calendar */
	if (y < 1753) {
		return -1;
	}
	c1 = century_value(y / 100);
	y1 = (y % 100);
	m1 = timelib_is_leap(y) ? m_table_leap[m] : m_table_common[m];
	dow = (c1 + y1 + m1 + (y1 / 4) + d) % 7;
	if (iso) {
		if (dow == 0) {
			dow = 7;
		}
	}
	return dow;
}

timelib_sll timelib_day_of_week(timelib_sll y, timelib_sll m, timelib_sll d)
{
	return timelib_day_of_week_ex(y, m, d, 0);
}

timelib_sll timelib_iso_day_of_week(timelib_sll y, timelib_sll m, timelib_sll d)
{
	return timelib_day_of_week_ex(y, m, d, 1);
}

                                /*     jan  feb  mar  apr  may  jun  jul  aug  sep  oct  nov  dec */
static int d_table_common[13]  = {  0,   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334 };
static int d_table_leap[13]    = {  0,   0,  31,  60,  91, 121, 152, 182, 213, 244, 274, 305, 335 };
static int ml_table_common[13] = {  0,  31,  28,  31,  30,  31,  30,  31,  31,  30,  31,  30,  31 };
static int ml_table_leap[13]   = {  0,  31,  29,  31,  30,  31,  30,  31,  31,  30,  31,  30,  31 };

timelib_sll timelib_day_of_year(timelib_sll y, timelib_sll m, timelib_sll d)
{
	return (timelib_is_leap(y) ? d_table_leap[m] : d_table_common[m]) + d - 1;
}

timelib_sll timelib_days_in_month(timelib_sll y, timelib_sll m)
{
	return timelib_is_leap(y) ? ml_table_leap[m] : ml_table_common[m];
}

void timelib_isoweek_from_date(timelib_sll y, timelib_sll m, timelib_sll d, timelib_sll *iw, timelib_sll *iy)
{
	int y_leap, prev_y_leap, doy, jan1weekday, weekday;

	y_leap = timelib_is_leap(y);
	prev_y_leap = timelib_is_leap(y-1);
	doy = timelib_day_of_year(y, m, d) + 1;
	if (y_leap && m > 2) {
		doy++;
	}
	jan1weekday = timelib_day_of_week(y, 1, 1);
	weekday = timelib_day_of_week(y, m, d);
	if (weekday == 0) weekday = 7;
	if (jan1weekday == 0) jan1weekday = 7;
	/* Find if Y M D falls in YearNumber Y-1, WeekNumber 52 or 53 */
	if (doy <= (8 - jan1weekday) && jan1weekday > 4) {
		*iy = y - 1;
		if (jan1weekday == 5 || (jan1weekday == 6 && prev_y_leap)) {
			*iw = 53;
		} else {
			*iw = 52;
		}
	} else {
		*iy = y;
	}
	/* 8. Find if Y M D falls in YearNumber Y+1, WeekNumber 1 */
	if (*iy == y) {
		int i;

		i = y_leap ? 366 : 365;
		if ((i - (doy - y_leap)) < (4 - weekday)) {
			*iy = y + 1;
			*iw = 1;
			return;
		}
	}
	/* 9. Find if Y M D falls in YearNumber Y, WeekNumber 1 through 53 */
	if (*iy == y) {
		int j;

		j = doy + (7 - weekday) + (jan1weekday - 1);
		*iw = j / 7;
		if (jan1weekday > 4) {
			*iw -= 1;
		}
	}
}

timelib_sll timelib_daynr_from_weeknr(timelib_sll y, timelib_sll w, timelib_sll d)
{
	timelib_sll dow, day;
	
	/* Figure out the dayofweek for y-1-1 */
	dow = timelib_day_of_week(y, 1, 1);
	/* then use that to figure out the offset for day 1 of week 1 */
	day = 0 - (dow > 4 ? dow - 7 : dow);

	/* Add weeks and days */
	return day + ((w - 1) * 7) + d;
}

#if 0
int main(void)
{
	printf("dow = %d\n", timelib_day_of_week(1978, 12, 22)); /* 5 */
	printf("dow = %d\n", timelib_day_of_week(2005,  2, 19)); /* 6 */
}
#endif