1ca987d46SWarner Losh /*-
2ca987d46SWarner Losh * Copyright (c) 1992, 1993
3ca987d46SWarner Losh * The Regents of the University of California. All rights reserved.
4ca987d46SWarner Losh *
5ca987d46SWarner Losh * Redistribution and use in source and binary forms, with or without
6ca987d46SWarner Losh * modification, are permitted provided that the following conditions
7ca987d46SWarner Losh * are met:
8ca987d46SWarner Losh * 1. Redistributions of source code must retain the above copyright
9ca987d46SWarner Losh * notice, this list of conditions and the following disclaimer.
10ca987d46SWarner Losh * 2. Redistributions in binary form must reproduce the above copyright
11ca987d46SWarner Losh * notice, this list of conditions and the following disclaimer in the
12ca987d46SWarner Losh * documentation and/or other materials provided with the distribution.
13ca987d46SWarner Losh * 3. Neither the name of the University nor the names of its contributors
14ca987d46SWarner Losh * may be used to endorse or promote products derived from this software
15ca987d46SWarner Losh * without specific prior written permission.
16ca987d46SWarner Losh *
17ca987d46SWarner Losh * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18ca987d46SWarner Losh * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19ca987d46SWarner Losh * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20ca987d46SWarner Losh * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21ca987d46SWarner Losh * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22ca987d46SWarner Losh * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23ca987d46SWarner Losh * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24ca987d46SWarner Losh * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25ca987d46SWarner Losh * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26ca987d46SWarner Losh * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27ca987d46SWarner Losh * SUCH DAMAGE.
28ca987d46SWarner Losh */
29ca987d46SWarner Losh
30ca987d46SWarner Losh #include <sys/types.h>
31ca987d46SWarner Losh
32*dcaa2d76SWarner Losh static long randseed = 1;
33ca987d46SWarner Losh
34ca987d46SWarner Losh void
srandom(unsigned int seed)35*dcaa2d76SWarner Losh srandom(unsigned int seed)
36ca987d46SWarner Losh {
37*dcaa2d76SWarner Losh
38ca987d46SWarner Losh randseed = seed;
39ca987d46SWarner Losh }
40ca987d46SWarner Losh
41ca987d46SWarner Losh /*
42ca987d46SWarner Losh * Pseudo-random number generator for randomizing the profiling clock,
43ca987d46SWarner Losh * and whatever else we might use it for. The result is uniform on
44ca987d46SWarner Losh * [0, 2^31 - 1].
45ca987d46SWarner Losh */
46*dcaa2d76SWarner Losh long
random(void)47*dcaa2d76SWarner Losh random(void)
48ca987d46SWarner Losh {
49ca987d46SWarner Losh long x, hi, lo, t;
50ca987d46SWarner Losh
51ca987d46SWarner Losh /*
52ca987d46SWarner Losh * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
53ca987d46SWarner Losh * From "Random number generators: good ones are hard to find",
54ca987d46SWarner Losh * Park and Miller, Communications of the ACM, vol. 31, no. 10,
55ca987d46SWarner Losh * October 1988, p. 1195.
56ca987d46SWarner Losh */
57ca987d46SWarner Losh x = randseed;
58ca987d46SWarner Losh hi = x / 127773;
59ca987d46SWarner Losh lo = x % 127773;
60ca987d46SWarner Losh t = 16807 * lo - 2836 * hi;
61ca987d46SWarner Losh if (t <= 0)
62ca987d46SWarner Losh t += 0x7fffffff;
63ca987d46SWarner Losh randseed = t;
64ca987d46SWarner Losh return (t);
65ca987d46SWarner Losh }
66