1 /*-
2 * Portions Copyright (c) 2010, Intel Corporation. All rights reserved.<BR>
3 * Copyright (c) 1990, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 4. Neither the name of the University nor the names of its contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 *
30 */
31 //__FBSDID("$FreeBSD: src/lib/libc/stdlib/rand.c,v 1.17.2.1.2.1 2009/10/25 01:10:29 kensmith Exp $");
32 #include <LibConfig.h>
33
34 #include <stdlib.h>
35
36 static UINT32 next = 1;
37
38 /** Compute a pseudo-random number.
39 *
40 * Compute x = (7^5 * x) mod (2^31 - 1)
41 * without overflowing 31 bits:
42 * (2^31 - 1) = 127773 * (7^5) + 2836
43 * From "Random number generators: good ones are hard to find",
44 * Park and Miller, Communications of the ACM, vol. 31, no. 10,
45 * October 1988, p. 1195.
46 **/
47 int
rand()48 rand()
49 {
50 INT32 hi, lo, x;
51
52 /* Can't be initialized with 0, so use another value. */
53 if (next == 0)
54 next = 123459876;
55 hi = next / 127773;
56 lo = next % 127773;
57 x = 16807 * lo - 2836 * hi;
58 if (x < 0)
59 x += 0x7fffffff;
60 return ((next = x) % ((UINT32)RAND_MAX + 1));
61 }
62
63 void
srand(unsigned int seed)64 srand(unsigned int seed)
65 {
66 next = (UINT32)seed;
67 }
68