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/time.h>          /* for sranddev() */
40#include <sys/types.h>
41#include <fcntl.h>             /* for sranddev() */
42#include <stdlib.h>
43#include <unistd.h>            /* for sranddev() */
44#include "un-namespace.h"
45
46#ifdef TEST
47#include <stdio.h>
48#endif /* TEST */
49
50static int
51do_rand(unsigned long *ctx)
52{
53#ifdef  USE_WEAK_SEEDING
54/*
55 * Historic implementation compatibility.
56 * The random sequences do not vary much with the seed,
57 * even with overflowing.
58 */
59	return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1));
60#else   /* !USE_WEAK_SEEDING */
61/*
62 * Compute x = (7^5 * x) mod (2^31 - 1)
63 * without overflowing 31 bits:
64 *      (2^31 - 1) = 127773 * (7^5) + 2836
65 * From "Random number generators: good ones are hard to find",
66 * Park and Miller, Communications of the ACM, vol. 31, no. 10,
67 * October 1988, p. 1195.
68 */
69	long hi, lo, x;
70
71	/* Can't be initialized with 0, so use another value. */
72	if (*ctx == 0)
73		*ctx = 123459876;
74	hi = *ctx / 127773;
75	lo = *ctx % 127773;
76	x = 16807 * lo - 2836 * hi;
77	if (x < 0)
78		x += 0x7fffffff;
79	return ((*ctx = x) % ((u_long)RAND_MAX + 1));
80#endif  /* !USE_WEAK_SEEDING */
81}
82
83
84int
85rand_r(unsigned int *ctx)
86{
87	u_long val = (u_long) *ctx;
88	int r = do_rand(&val);
89
90	*ctx = (unsigned int) val;
91	return (r);
92}
93
94
95static u_long next = 1;
96
97int
98rand()
99{
100	return (do_rand(&next));
101}
102
103void
104srand(seed)
105u_int seed;
106{
107	next = seed;
108}
109
110
111/*
112 * sranddev:
113 *
114 * Many programs choose the seed value in a totally predictable manner.
115 * This often causes problems.  We seed the generator using the much more
116 * secure random(4) interface.
117 */
118void
119sranddev(void)
120{
121	int fd, done;
122
123	done = 0;
124	fd = _open("/dev/random", O_RDONLY | O_CLOEXEC, 0);
125	if (fd >= 0) {
126		if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next))
127			done = 1;
128		_close(fd);
129	}
130
131	if (!done) {
132		struct timeval tv;
133
134		gettimeofday(&tv, NULL);
135		srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec);
136	}
137}
138
139
140#ifdef TEST
141
142main()
143{
144    int i;
145    unsigned myseed;
146
147    printf("seeding rand with 0x19610910: \n");
148    srand(0x19610910);
149
150    printf("generating three pseudo-random numbers:\n");
151    for (i = 0; i < 3; i++)
152    {
153	printf("next random number = %d\n", rand());
154    }
155
156    printf("generating the same sequence with rand_r:\n");
157    myseed = 0x19610910;
158    for (i = 0; i < 3; i++)
159    {
160	printf("next random number = %d\n", rand_r(&myseed));
161    }
162
163    return 0;
164}
165
166#endif /* TEST */
167
168