paskha.c revision 200470
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 200470 2009-12-13 04:50:11Z delphij $"); 29 30#include <stdio.h> 31#include <stdlib.h> 32#include <string.h> 33 34#include "calendar.h" 35 36#define PASKHA "paskha" 37#define PASKHALEN (sizeof(PASKHA) - 1) 38 39static int paskha(int); 40 41/* return year day for Orthodox Easter using Gauss formula */ 42/* (old style result) */ 43 44static int 45paskha(int R) /*year*/ 46{ 47 int a, b, c, d, e; 48 static int x = 15; 49 static int y = 6; 50 51 a = R % 19; 52 b = R % 4; 53 c = R % 7; 54 d = (19 * a + x) % 30; 55 e = (2 * b + 4 * c + 6 * d + y) % 7; 56 return (((cumdays[3] + 1) + 22) + (d + e)); 57} 58 59/* return year day for Orthodox Easter depending days */ 60 61int 62getpaskha(char *s, int year) 63{ 64 int offset; 65 66 if (strncasecmp(s, PASKHA, PASKHALEN) == 0) 67 s += PASKHALEN; 68 else if (npaskha.name != NULL 69 && strncasecmp(s, npaskha.name, npaskha.len) == 0) 70 s += npaskha.len; 71 else 72 return 0; 73 74 /* Paskha+1 or Paskha-2 75 * ^ ^ */ 76 77 switch (*s) { 78 79 case '-': 80 case '+': 81 offset = atoi(s); 82 break; 83 84 default: 85 offset = 0; 86 break; 87 } 88 89 return (paskha(year) + offset + 13 /* new style */); 90} 91