paskha.c revision 87235 
1/*
2 * Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28
29__FBSDID("$FreeBSD: head/usr.bin/calendar/paskha.c 87235 2001-12-02 22:44:14Z markm $");
30
31#include <stdio.h>
32#include <stdlib.h>
33#include <string.h>
34#include <time.h>
35
36#include "calendar.h"
37
38#define PASKHA "paskha"
39#define PASKHALEN (sizeof(PASKHA) - 1)
40
41static int paskha (int);
42
43/* return year day for Orthodox Easter using Gauss formula */
44/* (old style result) */
45
46static int
47paskha (R)
48int R;  /*year*/
49{
50	int a, b, c, d, e;
51	static int x = 15;
52	static int y = 6;
53	extern int *cumdays;
54
55	a = R % 19;
56	b = R % 4;
57	c = R % 7;
58	d = (19*a + x) % 30;
59	e = (2*b + 4*c + 6*d + y) % 7;
60	return (((cumdays[3] + 1) + 22) + (d + e));
61}
62
63/* return year day for Orthodox Easter depending days */
64
65int
66getpaskha(s, year)
67	char *s;
68        int year;
69{
70	int offset;
71	extern struct fixs npaskha;
72
73	if (strncasecmp(s, PASKHA, PASKHALEN) == 0)
74	    s += PASKHALEN;
75	else if (   npaskha.name != NULL
76		 && strncasecmp(s, npaskha.name, npaskha.len) == 0
77		)
78	    s += npaskha.len;
79	else
80	    return 0;
81
82
83	/* Paskha+1  or Paskha-2
84	 *       ^            ^   */
85
86	switch(*s) {
87
88	case '-':
89	case '+':
90	    offset = atoi(s);
91	    break;
92
93	default:
94	    offset = 0;
95	    break;
96	}
97
98	return (paskha(year) + offset + 13/* new style */);
99}
100