1*4a5d661aSToomas Soome /*-
2*4a5d661aSToomas Soome * Copyright (c) 1992, 1993
3*4a5d661aSToomas Soome * The Regents of the University of California. All rights reserved.
4*4a5d661aSToomas Soome *
5*4a5d661aSToomas Soome * Redistribution and use in source and binary forms, with or without
6*4a5d661aSToomas Soome * modification, are permitted provided that the following conditions
7*4a5d661aSToomas Soome * are met:
8*4a5d661aSToomas Soome * 1. Redistributions of source code must retain the above copyright
9*4a5d661aSToomas Soome * notice, this list of conditions and the following disclaimer.
10*4a5d661aSToomas Soome * 2. Redistributions in binary form must reproduce the above copyright
11*4a5d661aSToomas Soome * notice, this list of conditions and the following disclaimer in the
12*4a5d661aSToomas Soome * documentation and/or other materials provided with the distribution.
13*4a5d661aSToomas Soome * 4. Neither the name of the University nor the names of its contributors
14*4a5d661aSToomas Soome * may be used to endorse or promote products derived from this software
15*4a5d661aSToomas Soome * without specific prior written permission.
16*4a5d661aSToomas Soome *
17*4a5d661aSToomas Soome * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18*4a5d661aSToomas Soome * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19*4a5d661aSToomas Soome * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20*4a5d661aSToomas Soome * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21*4a5d661aSToomas Soome * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22*4a5d661aSToomas Soome * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23*4a5d661aSToomas Soome * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24*4a5d661aSToomas Soome * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25*4a5d661aSToomas Soome * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26*4a5d661aSToomas Soome * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27*4a5d661aSToomas Soome * SUCH DAMAGE.
28*4a5d661aSToomas Soome *
29*4a5d661aSToomas Soome * @(#)random.c 8.1 (Berkeley) 6/10/93
30*4a5d661aSToomas Soome */
31*4a5d661aSToomas Soome
32*4a5d661aSToomas Soome #include <sys/cdefs.h>
33*4a5d661aSToomas Soome __FBSDID("$FreeBSD$");
34*4a5d661aSToomas Soome
35*4a5d661aSToomas Soome #include <sys/types.h>
36*4a5d661aSToomas Soome
37*4a5d661aSToomas Soome static u_long randseed = 1;
38*4a5d661aSToomas Soome
39*4a5d661aSToomas Soome void
srandom(seed)40*4a5d661aSToomas Soome srandom(seed)
41*4a5d661aSToomas Soome u_long seed;
42*4a5d661aSToomas Soome {
43*4a5d661aSToomas Soome randseed = seed;
44*4a5d661aSToomas Soome }
45*4a5d661aSToomas Soome
46*4a5d661aSToomas Soome /*
47*4a5d661aSToomas Soome * Pseudo-random number generator for randomizing the profiling clock,
48*4a5d661aSToomas Soome * and whatever else we might use it for. The result is uniform on
49*4a5d661aSToomas Soome * [0, 2^31 - 1].
50*4a5d661aSToomas Soome */
51*4a5d661aSToomas Soome u_long
random()52*4a5d661aSToomas Soome random()
53*4a5d661aSToomas Soome {
54*4a5d661aSToomas Soome long x, hi, lo, t;
55*4a5d661aSToomas Soome
56*4a5d661aSToomas Soome /*
57*4a5d661aSToomas Soome * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
58*4a5d661aSToomas Soome * From "Random number generators: good ones are hard to find",
59*4a5d661aSToomas Soome * Park and Miller, Communications of the ACM, vol. 31, no. 10,
60*4a5d661aSToomas Soome * October 1988, p. 1195.
61*4a5d661aSToomas Soome */
62*4a5d661aSToomas Soome x = randseed;
63*4a5d661aSToomas Soome hi = x / 127773;
64*4a5d661aSToomas Soome lo = x % 127773;
65*4a5d661aSToomas Soome t = 16807 * lo - 2836 * hi;
66*4a5d661aSToomas Soome if (t <= 0)
67*4a5d661aSToomas Soome t += 0x7fffffff;
68*4a5d661aSToomas Soome randseed = t;
69*4a5d661aSToomas Soome return (t);
70*4a5d661aSToomas Soome }
71