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random.c revision 1.4 
      1 /*	$NetBSD: random.c,v 1.4 1997/10/12 11:45:43 lukem Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1988, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Timothy C. Stoehr.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #ifndef lint
     41 #if 0
     42 static char sccsid[] = "@(#)random.c	8.1 (Berkeley) 5/31/93";
     43 #else
     44 __RCSID("$NetBSD: random.c,v 1.4 1997/10/12 11:45:43 lukem Exp $");
     45 #endif
     46 #endif /* not lint */
     47 
     48 #include "rogue.h"
     49 
     50 /*
     51  * random.c
     52  *
     53  * This source herein may be modified and/or distributed by anybody who
     54  * so desires, with the following restrictions:
     55  *    1.)  No portion of this notice shall be removed.
     56  *    2.)  Credit shall not be taken for the creation of this source.
     57  *    3.)  This code is not to be traded, sold, or used for personal
     58  *         gain or profit.
     59  *
     60  */
     61 
     62 static long rntb[32] = {
     63 	         3, 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342,
     64 	0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb, 0x7449e56b,
     65 	0xbeb1dbb0, 0xab5c5918, 0x946554fd, 0x8c2e680f, 0xeb3d799f,
     66 	0xb11ee0b7, 0x2d436b86, 0xda672e2a, 0x1588ca88, 0xe369735d,
     67 	0x904f35f7, 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc,
     68 	0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, 0xf5ad9d0e,
     69 	0x8999220b, 0x27fb47b9
     70 };
     71 
     72 static long *fptr = &rntb[4];
     73 static long *rptr = &rntb[1];
     74 static long *state = &rntb[1];
     75 static int rand_type = 3;
     76 static int rand_deg = 31;
     77 static int rand_sep = 3;
     78 static long *end_ptr = &rntb[32];
     79 
     80 void
     81 srrandom(x)
     82 	int x;
     83 {
     84 	int i;
     85 
     86 	state[0] = (long) x;
     87 	if (rand_type != 0) {
     88 		for (i = 1; i < rand_deg; i++) {
     89 			state[i] = 1103515245 * state[i - 1] + 12345;
     90 		}
     91 		fptr = &state[rand_sep];
     92 		rptr = &state[0];
     93 		for (i = 0; i < 10 * rand_deg; i++) {
     94 			(void) rrandom();
     95 		}
     96 	}
     97 }
     98 
     99 long
    100 rrandom()
    101 {
    102 	long i;
    103 
    104 	if (rand_type == 0) {
    105 		i = state[0] = (state[0]*1103515245 + 12345) & 0x7fffffff;
    106 	} else {
    107 		*fptr += *rptr;
    108 		i = (*fptr >> 1) & 0x7fffffff;
    109 		if (++fptr >= end_ptr) {
    110 			fptr = state;
    111 			++rptr;
    112 		} else {
    113 			if (++rptr >= end_ptr) {
    114 				rptr = state;
    115 			}
    116 		}
    117 	}
    118 	return(i);
    119 }
    120 
    121 int
    122 get_rand(x, y)
    123 	int x, y;
    124 {
    125 	int r, t;
    126 	long lr;
    127 
    128 	if (x > y) {
    129 		t = y;
    130 		y = x;
    131 		x = t;
    132 	}
    133 	lr = rrandom();
    134 	lr &= (long) 0x00003fff;
    135 	r = (int) lr;
    136 	r = (r % ((y - x) + 1)) + x;
    137 	return(r);
    138 }
    139 
    140 int
    141 rand_percent(percentage)
    142 	int percentage;
    143 {
    144 	return(get_rand(1, 100) <= percentage);
    145 }
    146 
    147 int
    148 coin_toss()
    149 {
    150 	return(((rrandom() & 01) ? 1 : 0));
    151 }
    152