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freebsd/usr.bin/calendar/paskha.c

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/*
* Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia.
* 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 ``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 REGENTS 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.
*/
#include <stdlib.h>
#include <string.h>
#define PASKHA "paskha"
#define PASKHALEN (sizeof(PASKHA) - 1)
/* KOI8-R encoding, needed to fully handle Russian case */
#define PASKHA1 "<22><><EFBFBD><EFBFBD><EFBFBD>"
#define PASKHALEN1 (sizeof(PASKHA1) - 1)
extern int *cumdays;
/* return year day for Orthodox Easter using Gauss formula */
/* (old style result) */
static int
paskha (R)
int R; /*year*/
{
int a, b, c, d, e;
static int x = 15;
static int y = 6;
a = R % 19;
b = R % 4;
c = R % 7;
d = (19*a + x) % 30;
e = (2*b + 4*c + 6*d + y) % 7;
return ((cumdays[2/*feb*/] + 22/*mar*/) + (d + e));
}
/* return year day for Orthodox Easter depending days */
int
getpaskha(s, year)
char *s;
int year;
{
int offset;
if (strncasecmp(s, PASKHA, PASKHALEN) == 0)
s += PASKHALEN;
else if (strncasecmp(s, PASKHA1, PASKHALEN1) == 0)
s += PASKHALEN1;
else
return 0;
/* Paskha+1 or Paskha-2
* ^ ^ */
switch(*s) {
case '-':
case '+':
offset = atoi(s);
break;
default:
offset = 0;
break;
}
return (paskha(year) + offset + 13/* new style */);
}