95 lines
1.8 KiB
C
95 lines
1.8 KiB
C
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/*
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* Copyright (c) 1995 Wolfram Schneider. Public domain.
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*
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* $Id: ostern.c,v 1.2 1996/02/01 13:05:12 wosch Exp $
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*/
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#include <string.h>
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/* return year day for Easter */
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int easter (year)
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int year; /* 0 ... abcd, NOT since 1900 */
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{
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int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k,
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e_l, e_m, e_n, e_p, e_q;
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/* silly, but it works */
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e_a = year % 19;
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e_b = year / 100;
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e_c = year % 100;
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e_d = e_b / 4;
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e_e = e_b % 4;
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e_f = (e_b + 8) / 25;
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e_g = (e_b + 1 - e_f) / 3;
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e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30;
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e_i = e_c / 4;
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e_k = e_c % 4;
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e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7;
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e_m = (e_a + 11 * e_h + 22 * e_l) / 451;
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e_n = (e_h + e_l + 114 - (7 * e_m)) / 31;
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e_p = (e_h + e_l + 114 - (7 * e_m)) % 31;
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e_p = e_p + 1;
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e_q = 31 + 28;
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if (e_k == 0 && e_c != 0)
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e_q += 1;
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if (e_n == 4)
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e_q += 31;
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e_q += e_p;
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#if DEBUG
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printf("%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n", e_a , e_b , e_c , e_d , e_e , e_f , e_g , e_h , e_i , e_k , e_l , e_m , e_n , e_p , e_q);
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#endif
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return (e_q);
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}
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/* return year day for Easter or easter depending days
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* Match: Easter([+-][0-9]+)?
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* e.g: Easter-2 is Good Friday (2 days before Easter)
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*/
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int
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geteaster(s, year)
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char *s;
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int year;
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{
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register int offset = 0;
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#define EASTER "easter"
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#define EASTERNAMELEN (sizeof(EASTER) - 1)
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/* no easter */
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if (strncasecmp(s, EASTER, EASTERNAMELEN))
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return(0);
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#if DEBUG
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printf("%s %d %d\n", s, year, EASTERNAMELEN);
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#endif
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/* Easter+1 or Easter-2
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* ^ ^ */
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switch(*(s + EASTERNAMELEN)) {
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case '-':
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offset = -(atoi(s + EASTERNAMELEN + 1));
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break;
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case '+':
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offset = atoi(s + EASTERNAMELEN + 1);
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break;
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default:
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offset = 0;
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}
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return (easter(year) + offset);
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}
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