src/usr.bin/calendar/ostern.c - view

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File: [local] / src / usr.bin / calendar / ostern.c (download)

Revision 1.7, Tue Oct 27 23:59:36 2009 UTC (14 years, 6 months ago) by deraadt
Branch: MAIN
CVS Tags: OPENBSD_5_7_BASE, OPENBSD_5_7, OPENBSD_5_6_BASE, OPENBSD_5_6, OPENBSD_5_5_BASE, OPENBSD_5_5, OPENBSD_5_4_BASE, OPENBSD_5_4, OPENBSD_5_3_BASE, OPENBSD_5_3, OPENBSD_5_2_BASE, OPENBSD_5_2, OPENBSD_5_1_BASE, OPENBSD_5_1, OPENBSD_5_0_BASE, OPENBSD_5_0, OPENBSD_4_9_BASE, OPENBSD_4_9, OPENBSD_4_8_BASE, OPENBSD_4_8, OPENBSD_4_7_BASE, OPENBSD_4_7
Changes since 1.6: +2 -6 lines

rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: ostern.c,v 1.7 2009/10/27 23:59:36 deraadt Exp $	*/

/*
 * Copyright (c) 1996 Wolfram Schneider <wosch@FreeBSD.org>. Berlin.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * 	$Id: ostern.c,v 1.7 2009/10/27 23:59:36 deraadt Exp $
 */

#include <stdio.h>
#include <time.h>
#include <tzfile.h>

#include "calendar.h"

/* return year day for Easter */

int
easter(int year)	/* 0 ... abcd, NOT since 1900 */
{
	int	e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k;
	int	e_l, e_m, e_n, e_p, e_q;

	/* silly, but it works */
	e_a = year % 19;
	e_b = year / 100;
	e_c = year % 100;

	e_d = e_b / 4;
	e_e = e_b % 4;
	e_f = (e_b + 8) / 25;
	e_g = (e_b + 1 - e_f) / 3;
	e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30;
	e_i = e_c / 4;
	e_k = e_c % 4;
	e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7;
	e_m = (e_a + 11 * e_h + 22 * e_l) / 451;
	e_n = (e_h + e_l + 114 - (7 * e_m)) / 31;
	e_p = (e_h + e_l + 114 - (7 * e_m)) % 31;
	e_p = e_p + 1;

	e_q = 31 + 28 + e_p;
	if (isleap(year))
		e_q++;

	if (e_n == 4)
	e_q += 31;

#if DEBUG
	printf("%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n",
	    e_a, e_b, e_c, e_d, e_e, e_f, e_g, e_h,
	    e_i, e_k, e_l, e_m, e_n, e_p, e_q);
#endif

	return (e_q);
}