Use CSTD and remove local CSTD settings which are no longer needed.
[dragonfly.git] / lib / libstand / random.c
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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. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)random.c 8.1 (Berkeley) 6/10/93
34 * $FreeBSD: src/lib/libstand/random.c,v 1.2.2.1 2000/09/10 01:25:52 ps Exp $
ff2aef30 35 * $DragonFly: src/lib/libstand/random.c,v 1.4 2005/12/11 02:27:26 swildner Exp $
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36 */
37
38#include <sys/types.h>
39
40static u_long randseed = 1;
41
42void
ff2aef30 43srandom(u_long seed)
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44{
45 randseed = seed;
46}
47
48/*
49 * Pseudo-random number generator for randomizing the profiling clock,
50 * and whatever else we might use it for. The result is uniform on
51 * [0, 2^31 - 1].
52 */
53u_long
ff2aef30 54random(void)
984263bc 55{
660c873b 56 long x, hi, lo, t;
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57
58 /*
59 * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
60 * From "Random number generators: good ones are hard to find",
61 * Park and Miller, Communications of the ACM, vol. 31, no. 10,
62 * October 1988, p. 1195.
63 */
64 x = randseed;
65 hi = x / 127773;
66 lo = x % 127773;
67 t = 16807 * lo - 2836 * hi;
68 if (t <= 0)
69 t += 0x7fffffff;
70 randseed = t;
71 return (t);
72}