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random.c revision 1.3 
      1 /*	$NetBSD: random.c,v 1.3 1995/04/22 10:28:06 cgd 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 #ifndef lint
     40 #if 0
     41 static char sccsid[] = "@(#)random.c	8.1 (Berkeley) 5/31/93";
     42 #else
     43 static char rcsid[] = "$NetBSD: random.c,v 1.3 1995/04/22 10:28:06 cgd Exp $";
     44 #endif
     45 #endif /* not lint */
     46 
     47 /*
     48  * random.c
     49  *
     50  * This source herein may be modified and/or distributed by anybody who
     51  * so desires, with the following restrictions:
     52  *    1.)  No portion of this notice shall be removed.
     53  *    2.)  Credit shall not be taken for the creation of this source.
     54  *    3.)  This code is not to be traded, sold, or used for personal
     55  *         gain or profit.
     56  *
     57  */
     58 
     59 static long rntb[32] = {
     60 	         3, 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342,
     61 	0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb, 0x7449e56b,
     62 	0xbeb1dbb0, 0xab5c5918, 0x946554fd, 0x8c2e680f, 0xeb3d799f,
     63 	0xb11ee0b7, 0x2d436b86, 0xda672e2a, 0x1588ca88, 0xe369735d,
     64 	0x904f35f7, 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc,
     65 	0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, 0xf5ad9d0e,
     66 	0x8999220b, 0x27fb47b9
     67 };
     68 
     69 static long *fptr = &rntb[4];
     70 static long *rptr = &rntb[1];
     71 static long *state = &rntb[1];
     72 static int rand_type = 3;
     73 static int rand_deg = 31;
     74 static int rand_sep = 3;
     75 static long *end_ptr = &rntb[32];
     76 
     77 srrandom(x)
     78 int x;
     79 {
     80 	register int i;
     81 	long rrandom();
     82 
     83 	state[0] = (long) x;
     84 	if (rand_type != 0) {
     85 		for (i = 1; i < rand_deg; i++) {
     86 			state[i] = 1103515245 * state[i - 1] + 12345;
     87 		}
     88 		fptr = &state[rand_sep];
     89 		rptr = &state[0];
     90 		for (i = 0; i < 10 * rand_deg; i++) {
     91 			(void) rrandom();
     92 		}
     93 	}
     94 }
     95 
     96 long
     97 rrandom()
     98 {
     99 	long i;
    100 
    101 	if (rand_type == 0) {
    102 		i = state[0] = (state[0]*1103515245 + 12345) & 0x7fffffff;
    103 	} else {
    104 		*fptr += *rptr;
    105 		i = (*fptr >> 1) & 0x7fffffff;
    106 		if (++fptr >= end_ptr) {
    107 			fptr = state;
    108 			++rptr;
    109 		} else {
    110 			if (++rptr >= end_ptr) {
    111 				rptr = state;
    112 			}
    113 		}
    114 	}
    115 	return(i);
    116 }
    117 
    118 get_rand(x, y)
    119 register int x, y;
    120 {
    121 	register int r, t;
    122 	long lr;
    123 
    124 	if (x > y) {
    125 		t = y;
    126 		y = x;
    127 		x = t;
    128 	}
    129 	lr = rrandom();
    130 	lr &= (long) 0x00003fff;
    131 	r = (int) lr;
    132 	r = (r % ((y - x) + 1)) + x;
    133 	return(r);
    134 }
    135 
    136 rand_percent(percentage)
    137 register int percentage;
    138 {
    139 	return(get_rand(1, 100) <= percentage);
    140 }
    141 
    142 coin_toss()
    143 {
    144 
    145 	return(((rrandom() & 01) ? 1 : 0));
    146 }
    147