1*479ab7f0SSascha Wildner /*-
2*479ab7f0SSascha Wildner * Copyright (c) 1992, 1993
3*479ab7f0SSascha Wildner * The Regents of the University of California. All rights reserved.
4*479ab7f0SSascha Wildner *
5*479ab7f0SSascha Wildner * Redistribution and use in source and binary forms, with or without
6*479ab7f0SSascha Wildner * modification, are permitted provided that the following conditions
7*479ab7f0SSascha Wildner * are met:
8*479ab7f0SSascha Wildner * 1. Redistributions of source code must retain the above copyright
9*479ab7f0SSascha Wildner * notice, this list of conditions and the following disclaimer.
10*479ab7f0SSascha Wildner * 2. Redistributions in binary form must reproduce the above copyright
11*479ab7f0SSascha Wildner * notice, this list of conditions and the following disclaimer in the
12*479ab7f0SSascha Wildner * documentation and/or other materials provided with the distribution.
13*479ab7f0SSascha Wildner * 3. Neither the name of the University nor the names of its contributors
14*479ab7f0SSascha Wildner * may be used to endorse or promote products derived from this software
15*479ab7f0SSascha Wildner * without specific prior written permission.
16*479ab7f0SSascha Wildner *
17*479ab7f0SSascha Wildner * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18*479ab7f0SSascha Wildner * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19*479ab7f0SSascha Wildner * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20*479ab7f0SSascha Wildner * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21*479ab7f0SSascha Wildner * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22*479ab7f0SSascha Wildner * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23*479ab7f0SSascha Wildner * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24*479ab7f0SSascha Wildner * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25*479ab7f0SSascha Wildner * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26*479ab7f0SSascha Wildner * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27*479ab7f0SSascha Wildner * SUCH DAMAGE.
28*479ab7f0SSascha Wildner *
29*479ab7f0SSascha Wildner * @(#)random.c 8.1 (Berkeley) 6/10/93
30*479ab7f0SSascha Wildner * $FreeBSD: src/lib/libstand/random.c,v 1.2.2.1 2000/09/10 01:25:52 ps Exp $
31*479ab7f0SSascha Wildner * $DragonFly: src/lib/libstand/random.c,v 1.4 2005/12/11 02:27:26 swildner Exp $
32*479ab7f0SSascha Wildner */
33*479ab7f0SSascha Wildner
34*479ab7f0SSascha Wildner #include <sys/types.h>
35*479ab7f0SSascha Wildner
36*479ab7f0SSascha Wildner static u_long randseed = 1;
37*479ab7f0SSascha Wildner
38*479ab7f0SSascha Wildner void
srandom(u_long seed)39*479ab7f0SSascha Wildner srandom(u_long seed)
40*479ab7f0SSascha Wildner {
41*479ab7f0SSascha Wildner randseed = seed;
42*479ab7f0SSascha Wildner }
43*479ab7f0SSascha Wildner
44*479ab7f0SSascha Wildner /*
45*479ab7f0SSascha Wildner * Pseudo-random number generator for randomizing the profiling clock,
46*479ab7f0SSascha Wildner * and whatever else we might use it for. The result is uniform on
47*479ab7f0SSascha Wildner * [0, 2^31 - 1].
48*479ab7f0SSascha Wildner */
49*479ab7f0SSascha Wildner u_long
random(void)50*479ab7f0SSascha Wildner random(void)
51*479ab7f0SSascha Wildner {
52*479ab7f0SSascha Wildner long x, hi, lo, t;
53*479ab7f0SSascha Wildner
54*479ab7f0SSascha Wildner /*
55*479ab7f0SSascha Wildner * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
56*479ab7f0SSascha Wildner * From "Random number generators: good ones are hard to find",
57*479ab7f0SSascha Wildner * Park and Miller, Communications of the ACM, vol. 31, no. 10,
58*479ab7f0SSascha Wildner * October 1988, p. 1195.
59*479ab7f0SSascha Wildner */
60*479ab7f0SSascha Wildner x = randseed;
61*479ab7f0SSascha Wildner hi = x / 127773;
62*479ab7f0SSascha Wildner lo = x % 127773;
63*479ab7f0SSascha Wildner t = 16807 * lo - 2836 * hi;
64*479ab7f0SSascha Wildner if (t <= 0)
65*479ab7f0SSascha Wildner t += 0x7fffffff;
66*479ab7f0SSascha Wildner randseed = t;
67*479ab7f0SSascha Wildner return (t);
68*479ab7f0SSascha Wildner }
69