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/sys/libkern/random.c,v 1.7 1999/08/28 00:46:36 peter Exp $ 35 * $DragonFly: src/sys/libkern/random.c,v 1.5 2004/01/28 14:36:00 joerg Exp $ 36 */ 37 38 #include <sys/libkern.h> 39 40 static u_long randseed = 1; 41 42 void 43 srandom(u_long seed) 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 */ 53 u_long 54 random(void) 55 { 56 long x, hi, lo, t; 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 } 73