paskha.c revision 15714
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 <stdlib.h> 28#include <string.h> 29 30#define PASKHA "paskha" 31#define PASKHALEN (sizeof(PASKHA) - 1) 32 33/* KOI8-R encoding, needed to fully handle Russian case */ 34#define PASKHA1 "�����" 35#define PASKHALEN1 (sizeof(PASKHA1) - 1) 36 37extern int *cumdays; 38 39/* return year day for Orthodox Easter using Gauss formula */ 40/* (old style result) */ 41 42static int 43paskha (R) 44int R; /*year*/ 45{ 46 int a, b, c, d, e; 47 static int x = 15; 48 static int y = 6; 49 50 a = R % 19; 51 b = R % 4; 52 c = R % 7; 53 d = (19*a + x) % 30; 54 e = (2*b + 4*c + 6*d + y) % 7; 55 return ((cumdays[2/*feb*/] + 22/*mar*/) + (d + e)); 56} 57 58/* return year day for Orthodox Easter depending days */ 59 60int 61getpaskha(s, year) 62 char *s; 63 int year; 64{ 65 int offset; 66 67 if (strncasecmp(s, PASKHA, PASKHALEN) == 0) 68 s += PASKHALEN; 69 else if (strncasecmp(s, PASKHA1, PASKHALEN1) == 0) 70 s += PASKHALEN1; 71 else 72 return 0; 73 74 75 /* Paskha+1 or Paskha-2 76 * ^ ^ */ 77 78 switch(*s) { 79 80 case '-': 81 case '+': 82 offset = atoi(s); 83 break; 84 85 default: 86 offset = 0; 87 break; 88 } 89 90 return (paskha(year) + offset + 13/* new style */); 91} 92