1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>.
30 */
31
32#if defined(LIBC_SCCS) && !defined(lint)
33static char sccsid[] = "@(#)rand.c	8.1 (Berkeley) 6/14/93";
34#endif /* LIBC_SCCS and not lint */
35#include <sys/cdefs.h>
36__FBSDID("$FreeBSD$");
37
38#include "namespace.h"
39#include <sys/param.h>
40#include <sys/sysctl.h>
41#include <sys/types.h>
42#include <stdlib.h>
43#include "un-namespace.h"
44
45#ifdef TEST
46#include <stdio.h>
47#endif /* TEST */
48
49static int
50do_rand(unsigned long *ctx)
51{
52#ifdef  USE_WEAK_SEEDING
53/*
54 * Historic implementation compatibility.
55 * The random sequences do not vary much with the seed,
56 * even with overflowing.
57 */
58	return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1));
59#else   /* !USE_WEAK_SEEDING */
60/*
61 * Compute x = (7^5 * x) mod (2^31 - 1)
62 * without overflowing 31 bits:
63 *      (2^31 - 1) = 127773 * (7^5) + 2836
64 * From "Random number generators: good ones are hard to find",
65 * Park and Miller, Communications of the ACM, vol. 31, no. 10,
66 * October 1988, p. 1195.
67 */
68	long hi, lo, x;
69
70	/* Must be in [1, 0x7ffffffe] range at this point. */
71	hi = *ctx / 127773;
72	lo = *ctx % 127773;
73	x = 16807 * lo - 2836 * hi;
74	if (x < 0)
75		x += 0x7fffffff;
76	*ctx = x;
77	/* Transform to [0, 0x7ffffffd] range. */
78	return (x - 1);
79#endif  /* !USE_WEAK_SEEDING */
80}
81
82
83int
84rand_r(unsigned int *ctx)
85{
86	u_long val;
87	int r;
88
89#ifdef  USE_WEAK_SEEDING
90	val = *ctx;
91#else
92	/* Transform to [1, 0x7ffffffe] range. */
93	val = (*ctx % 0x7ffffffe) + 1;
94#endif
95	r = do_rand(&val);
96
97#ifdef  USE_WEAK_SEEDING
98	*ctx = (unsigned int)val;
99#else
100	*ctx = (unsigned int)(val - 1);
101#endif
102	return (r);
103}
104
105
106static u_long next =
107#ifdef  USE_WEAK_SEEDING
108    1;
109#else
110    2;
111#endif
112
113int
114rand()
115{
116	return (do_rand(&next));
117}
118
119void
120srand(seed)
121u_int seed;
122{
123	next = seed;
124#ifndef USE_WEAK_SEEDING
125	/* Transform to [1, 0x7ffffffe] range. */
126	next = (next % 0x7ffffffe) + 1;
127#endif
128}
129
130
131/*
132 * sranddev:
133 *
134 * Many programs choose the seed value in a totally predictable manner.
135 * This often causes problems.  We seed the generator using pseudo-random
136 * data from the kernel.
137 */
138void
139sranddev()
140{
141	int mib[2];
142	size_t len;
143
144	len = sizeof(next);
145
146	mib[0] = CTL_KERN;
147	mib[1] = KERN_ARND;
148	sysctl(mib, 2, (void *)&next, &len, NULL, 0);
149#ifndef USE_WEAK_SEEDING
150	/* Transform to [1, 0x7ffffffe] range. */
151	next = (next % 0x7ffffffe) + 1;
152#endif
153}
154
155
156#ifdef TEST
157
158main()
159{
160    int i;
161    unsigned myseed;
162
163    printf("seeding rand with 0x19610910: \n");
164    srand(0x19610910);
165
166    printf("generating three pseudo-random numbers:\n");
167    for (i = 0; i < 3; i++)
168    {
169	printf("next random number = %d\n", rand());
170    }
171
172    printf("generating the same sequence with rand_r:\n");
173    myseed = 0x19610910;
174    for (i = 0; i < 3; i++)
175    {
176	printf("next random number = %d\n", rand_r(&myseed));
177    }
178
179    return 0;
180}
181
182#endif /* TEST */
183
184