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 */ 35 36 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD$"); 38 39 #include <sys/libkern.h> 40 41 #define NSHUFF 50 /* to drop some "seed -> 1st value" linearity */ 42 43 static u_long randseed = 937186357; /* after srandom(1), NSHUFF counted */ 44 45 void 46 srandom(seed) 47 u_long seed; 48 { 49 int i; 50 51 randseed = seed; 52 for (i = 0; i < NSHUFF; i++) 53 (void)random(); 54 } 55 56 /* 57 * Pseudo-random number generator for randomizing the profiling clock, 58 * and whatever else we might use it for. The result is uniform on 59 * [0, 2^31 - 1]. 60 */ 61 u_long 62 random() 63 { 64 register long x, hi, lo, t; 65 66 /* 67 * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1). 68 * From "Random number generators: good ones are hard to find", 69 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 70 * October 1988, p. 1195. 71 */ 72 /* Can't be initialized with 0, so use another value. */ 73 if ((x = randseed) == 0) 74 x = 123459876; 75 hi = x / 127773; 76 lo = x % 127773; 77 t = 16807 * lo - 2836 * hi; 78 if (t < 0) 79 t += 0x7fffffff; 80 randseed = t; 81 return (t); 82 } 83