138451Smsmith/*- 238451Smsmith * Copyright (c) 1992, 1993 338451Smsmith * The Regents of the University of California. All rights reserved. 438451Smsmith * 538451Smsmith * Redistribution and use in source and binary forms, with or without 638451Smsmith * modification, are permitted provided that the following conditions 738451Smsmith * are met: 838451Smsmith * 1. Redistributions of source code must retain the above copyright 938451Smsmith * notice, this list of conditions and the following disclaimer. 1038451Smsmith * 2. Redistributions in binary form must reproduce the above copyright 1138451Smsmith * notice, this list of conditions and the following disclaimer in the 1238451Smsmith * documentation and/or other materials provided with the distribution. 1338451Smsmith * 4. Neither the name of the University nor the names of its contributors 1438451Smsmith * may be used to endorse or promote products derived from this software 1538451Smsmith * without specific prior written permission. 1638451Smsmith * 1738451Smsmith * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 1838451Smsmith * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 1938451Smsmith * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 2038451Smsmith * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 2138451Smsmith * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 2238451Smsmith * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 2338451Smsmith * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 2438451Smsmith * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 2538451Smsmith * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 2638451Smsmith * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 2738451Smsmith * SUCH DAMAGE. 2838451Smsmith * 2938451Smsmith * @(#)random.c 8.1 (Berkeley) 6/10/93 3038451Smsmith */ 3138451Smsmith 3284221Sdillon#include <sys/cdefs.h> 3384221Sdillon__FBSDID("$FreeBSD$"); 3484221Sdillon 3565400Speter#include <sys/types.h> 3638451Smsmith 3738451Smsmithstatic u_long randseed = 1; 3838451Smsmith 3938451Smsmithvoid 4038451Smsmithsrandom(seed) 4138451Smsmith u_long seed; 4238451Smsmith{ 4338451Smsmith randseed = seed; 4438451Smsmith} 4538451Smsmith 4638451Smsmith/* 4738451Smsmith * Pseudo-random number generator for randomizing the profiling clock, 4838451Smsmith * and whatever else we might use it for. The result is uniform on 4938451Smsmith * [0, 2^31 - 1]. 5038451Smsmith */ 5138451Smsmithu_long 5238451Smsmithrandom() 5338451Smsmith{ 5492913Sobrien long x, hi, lo, t; 5538451Smsmith 5638451Smsmith /* 5738451Smsmith * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1). 5838451Smsmith * From "Random number generators: good ones are hard to find", 5938451Smsmith * Park and Miller, Communications of the ACM, vol. 31, no. 10, 6038451Smsmith * October 1988, p. 1195. 6138451Smsmith */ 6238451Smsmith x = randseed; 6338451Smsmith hi = x / 127773; 6438451Smsmith lo = x % 127773; 6538451Smsmith t = 16807 * lo - 2836 * hi; 6638451Smsmith if (t <= 0) 6738451Smsmith t += 0x7fffffff; 6838451Smsmith randseed = t; 6938451Smsmith return (t); 7038451Smsmith} 71