10384eafeSToomas Soome /*
2199767f8SToomas Soome * Copyright (c) 1992, 1993
3199767f8SToomas Soome * The Regents of the University of California. All rights reserved.
4199767f8SToomas Soome *
5199767f8SToomas Soome * Redistribution and use in source and binary forms, with or without
6199767f8SToomas Soome * modification, are permitted provided that the following conditions
7199767f8SToomas Soome * are met:
8199767f8SToomas Soome * 1. Redistributions of source code must retain the above copyright
9199767f8SToomas Soome * notice, this list of conditions and the following disclaimer.
10199767f8SToomas Soome * 2. Redistributions in binary form must reproduce the above copyright
11199767f8SToomas Soome * notice, this list of conditions and the following disclaimer in the
12199767f8SToomas Soome * documentation and/or other materials provided with the distribution.
131974da4bSToomas Soome * 3. Neither the name of the University nor the names of its contributors
14199767f8SToomas Soome * may be used to endorse or promote products derived from this software
15199767f8SToomas Soome * without specific prior written permission.
16199767f8SToomas Soome *
17199767f8SToomas Soome * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18199767f8SToomas Soome * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19199767f8SToomas Soome * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20199767f8SToomas Soome * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21199767f8SToomas Soome * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22199767f8SToomas Soome * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23199767f8SToomas Soome * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24199767f8SToomas Soome * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25199767f8SToomas Soome * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26199767f8SToomas Soome * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27199767f8SToomas Soome * SUCH DAMAGE.
28199767f8SToomas Soome *
29199767f8SToomas Soome * @(#)random.c 8.1 (Berkeley) 6/10/93
30199767f8SToomas Soome */
31199767f8SToomas Soome
32199767f8SToomas Soome #include <sys/cdefs.h>
33199767f8SToomas Soome
34199767f8SToomas Soome #include <sys/types.h>
35199767f8SToomas Soome
360384eafeSToomas Soome static ulong_t randseed = 1;
37199767f8SToomas Soome
38199767f8SToomas Soome void
srandom(ulong_t seed)390384eafeSToomas Soome srandom(ulong_t seed)
40199767f8SToomas Soome {
41199767f8SToomas Soome randseed = seed;
42199767f8SToomas Soome }
43199767f8SToomas Soome
44199767f8SToomas Soome /*
45199767f8SToomas Soome * Pseudo-random number generator for randomizing the profiling clock,
46199767f8SToomas Soome * and whatever else we might use it for. The result is uniform on
47199767f8SToomas Soome * [0, 2^31 - 1].
48199767f8SToomas Soome */
490384eafeSToomas Soome ulong_t
random(void)500384eafeSToomas Soome random(void)
51199767f8SToomas Soome {
52199767f8SToomas Soome long x, hi, lo, t;
53199767f8SToomas Soome
54199767f8SToomas Soome /*
55199767f8SToomas Soome * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
56199767f8SToomas Soome * From "Random number generators: good ones are hard to find",
57199767f8SToomas Soome * Park and Miller, Communications of the ACM, vol. 31, no. 10,
58199767f8SToomas Soome * October 1988, p. 1195.
59199767f8SToomas Soome */
60199767f8SToomas Soome x = randseed;
61199767f8SToomas Soome hi = x / 127773;
62199767f8SToomas Soome lo = x % 127773;
63199767f8SToomas Soome t = 16807 * lo - 2836 * hi;
64199767f8SToomas Soome if (t <= 0)
65199767f8SToomas Soome t += 0x7fffffff;
66199767f8SToomas Soome randseed = t;
67199767f8SToomas Soome return (t);
68199767f8SToomas Soome }
69