paskha.c revision 87628 
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__FBSDID("$FreeBSD: head/usr.bin/calendar/paskha.c 87628 2001-12-10 21:13:08Z dwmalone $");
29
30#include <stdio.h>
31#include <stdlib.h>
32#include <string.h>
33#include <time.h>
34
35#include "calendar.h"
36
37#define PASKHA "paskha"
38#define PASKHALEN (sizeof(PASKHA) - 1)
39
40static int paskha (int);
41
42/* return year day for Orthodox Easter using Gauss formula */
43/* (old style result) */
44
45static int
46paskha (R)
47int R;  /*year*/
48{
49	int a, b, c, d, e;
50	static int x = 15;
51	static int y = 6;
52	extern int *cumdays;
53
54	a = R % 19;
55	b = R % 4;
56	c = R % 7;
57	d = (19*a + x) % 30;
58	e = (2*b + 4*c + 6*d + y) % 7;
59	return (((cumdays[3] + 1) + 22) + (d + e));
60}
61
62/* return year day for Orthodox Easter depending days */
63
64int
65getpaskha(s, year)
66	char *s;
67        int year;
68{
69	int offset;
70	extern struct fixs npaskha;
71
72	if (strncasecmp(s, PASKHA, PASKHALEN) == 0)
73	    s += PASKHALEN;
74	else if (   npaskha.name != NULL
75		 && strncasecmp(s, npaskha.name, npaskha.len) == 0
76		)
77	    s += npaskha.len;
78	else
79	    return 0;
80
81
82	/* Paskha+1  or Paskha-2
83	 *       ^            ^   */
84
85	switch(*s) {
86
87	case '-':
88	case '+':
89	    offset = atoi(s);
90	    break;
91
92	default:
93	    offset = 0;
94	    break;
95	}
96
97	return (paskha(year) + offset + 13/* new style */);
98}
99