1*4a5d661aSToomas Soome /*- 2*4a5d661aSToomas Soome * Copyright (c) 1992, 1993 3*4a5d661aSToomas Soome * The Regents of the University of California. All rights reserved. 4*4a5d661aSToomas Soome * 5*4a5d661aSToomas Soome * Redistribution and use in source and binary forms, with or without 6*4a5d661aSToomas Soome * modification, are permitted provided that the following conditions 7*4a5d661aSToomas Soome * are met: 8*4a5d661aSToomas Soome * 1. Redistributions of source code must retain the above copyright 9*4a5d661aSToomas Soome * notice, this list of conditions and the following disclaimer. 10*4a5d661aSToomas Soome * 2. Redistributions in binary form must reproduce the above copyright 11*4a5d661aSToomas Soome * notice, this list of conditions and the following disclaimer in the 12*4a5d661aSToomas Soome * documentation and/or other materials provided with the distribution. 13*4a5d661aSToomas Soome * 4. Neither the name of the University nor the names of its contributors 14*4a5d661aSToomas Soome * may be used to endorse or promote products derived from this software 15*4a5d661aSToomas Soome * without specific prior written permission. 16*4a5d661aSToomas Soome * 17*4a5d661aSToomas Soome * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18*4a5d661aSToomas Soome * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19*4a5d661aSToomas Soome * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20*4a5d661aSToomas Soome * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21*4a5d661aSToomas Soome * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22*4a5d661aSToomas Soome * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23*4a5d661aSToomas Soome * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24*4a5d661aSToomas Soome * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25*4a5d661aSToomas Soome * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26*4a5d661aSToomas Soome * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27*4a5d661aSToomas Soome * SUCH DAMAGE. 28*4a5d661aSToomas Soome * 29*4a5d661aSToomas Soome * @(#)random.c 8.1 (Berkeley) 6/10/93 30*4a5d661aSToomas Soome */ 31*4a5d661aSToomas Soome 32*4a5d661aSToomas Soome #include <sys/cdefs.h> 33*4a5d661aSToomas Soome __FBSDID("$FreeBSD$"); 34*4a5d661aSToomas Soome 35*4a5d661aSToomas Soome #include <sys/types.h> 36*4a5d661aSToomas Soome 37*4a5d661aSToomas Soome static u_long randseed = 1; 38*4a5d661aSToomas Soome 39*4a5d661aSToomas Soome void 40*4a5d661aSToomas Soome srandom(seed) 41*4a5d661aSToomas Soome u_long seed; 42*4a5d661aSToomas Soome { 43*4a5d661aSToomas Soome randseed = seed; 44*4a5d661aSToomas Soome } 45*4a5d661aSToomas Soome 46*4a5d661aSToomas Soome /* 47*4a5d661aSToomas Soome * Pseudo-random number generator for randomizing the profiling clock, 48*4a5d661aSToomas Soome * and whatever else we might use it for. The result is uniform on 49*4a5d661aSToomas Soome * [0, 2^31 - 1]. 50*4a5d661aSToomas Soome */ 51*4a5d661aSToomas Soome u_long 52*4a5d661aSToomas Soome random() 53*4a5d661aSToomas Soome { 54*4a5d661aSToomas Soome long x, hi, lo, t; 55*4a5d661aSToomas Soome 56*4a5d661aSToomas Soome /* 57*4a5d661aSToomas Soome * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1). 58*4a5d661aSToomas Soome * From "Random number generators: good ones are hard to find", 59*4a5d661aSToomas Soome * Park and Miller, Communications of the ACM, vol. 31, no. 10, 60*4a5d661aSToomas Soome * October 1988, p. 1195. 61*4a5d661aSToomas Soome */ 62*4a5d661aSToomas Soome x = randseed; 63*4a5d661aSToomas Soome hi = x / 127773; 64*4a5d661aSToomas Soome lo = x % 127773; 65*4a5d661aSToomas Soome t = 16807 * lo - 2836 * hi; 66*4a5d661aSToomas Soome if (t <= 0) 67*4a5d661aSToomas Soome t += 0x7fffffff; 68*4a5d661aSToomas Soome randseed = t; 69*4a5d661aSToomas Soome return (t); 70*4a5d661aSToomas Soome } 71