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