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Annotation of src/usr.bin/calendar/ostern.c, Revision 1.2

1.2     ! pjanzen     1: /*     $OpenBSD: ostern.c,v 1.1 1996/12/05 06:04:40 millert Exp $      */
1.1       millert     2:
                      3: /*
                      4:  * Copyright (c) 1996 Wolfram Schneider <wosch@FreeBSD.org>. Berlin.
                      5:  * All rights reserved.
                      6:  *
                      7:  * Redistribution and use in source and binary forms, with or without
                      8:  * modification, are permitted provided that the following conditions
                      9:  * are met:
                     10:  * 1. Redistributions of source code must retain the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer.
                     12:  * 2. Redistributions in binary form must reproduce the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer in the
                     14:  *    documentation and/or other materials provided with the distribution.
                     15:  *
                     16:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
                     17:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     18:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     19:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
                     20:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     21:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     22:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     23:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     24:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     25:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     26:  * SUCH DAMAGE.
                     27:  *
1.2     ! pjanzen    28:  *     $Id: ostern.c,v 1.1 1996/12/05 06:04:40 millert Exp $
1.1       millert    29:  */
                     30:
                     31: #ifndef lint
1.2     ! pjanzen    32: static char rcsid[] = "$OpenBSD: ostern.c,v 1.1 1996/12/05 06:04:40 millert Exp $";
1.1       millert    33: #endif /* not lint */
                     34:
                     35: #include <stdio.h>
                     36: #include <stdlib.h>
                     37: #include <string.h>
                     38: #include <time.h>
                     39:
                     40: #include "calendar.h"
                     41:
                     42: /* return year day for Easter */
                     43:
                     44: int easter (year)
                     45:     int year;            /* 0 ... abcd, NOT since 1900 */
                     46: {
                     47:
                     48:     int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k,
                     49:         e_l, e_m, e_n, e_p, e_q;
1.2     ! pjanzen    50:     extern int *cumdays;
1.1       millert    51:
                     52:     /* silly, but it works */
                     53:     e_a = year % 19;
                     54:     e_b = year / 100;
                     55:     e_c = year % 100;
                     56:
                     57:     e_d = e_b / 4;
                     58:     e_e = e_b % 4;
                     59:     e_f = (e_b + 8) / 25;
                     60:     e_g = (e_b + 1 - e_f) / 3;
                     61:     e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30;
                     62:     e_i = e_c / 4;
                     63:     e_k = e_c % 4;
                     64:     e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7;
                     65:     e_m = (e_a + 11 * e_h + 22 * e_l) / 451;
                     66:     e_n = (e_h + e_l + 114 - (7 * e_m)) / 31;
                     67:     e_p = (e_h + e_l + 114 - (7 * e_m)) % 31;
                     68:     e_p = e_p + 1;
                     69:
1.2     ! pjanzen    70:     e_q = cumdays[3] + 1 + e_p;
1.1       millert    71:
                     72:     if (e_n == 4)
                     73:        e_q += 31;
                     74:
                     75: #if DEBUG
                     76:     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);
                     77: #endif
                     78:
                     79:     return (e_q);
                     80: }
                     81:
                     82: /* return year day for  Easter or easter depending days
                     83:  * Match: Easter([+-][0-9]+)?
                     84:  * e.g: Easter-2 is  Good Friday (2 days before Easter)
                     85:  */
                     86:
                     87: int
                     88: geteaster(s, year)
                     89:        char *s;
                     90:         int year;
                     91: {
                     92:        register int offset = 0;
                     93:        extern struct fixs neaster;
                     94:
                     95: #define EASTER "easter"
                     96: #define EASTERNAMELEN (sizeof(EASTER) - 1)
                     97:
                     98:        if (strncasecmp(s, EASTER, EASTERNAMELEN) == 0)
                     99:            s += EASTERNAMELEN;
                    100:        else if (   neaster.name != NULL
                    101:                 && strncasecmp(s, neaster.name, neaster.len) == 0
                    102:                )
                    103:            s += neaster.len;
                    104:        else
                    105:            return(0);
                    106:
                    107: #if DEBUG
                    108:        printf("%s %d %d\n", s, year, EASTERNAMELEN);
                    109: #endif
                    110:
                    111:        /* Easter+1  or Easter-2
                    112:         *       ^            ^   */
                    113:
                    114:        switch(*s) {
                    115:
                    116:        case '-':
                    117:        case '+':
                    118:            offset = atoi(s);
                    119:            break;
                    120:
                    121:        default:
                    122:            offset = 0;
                    123:        }
                    124:
                    125:        return (easter(year) + offset);
                    126: }