The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/libkern/random.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    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: releng/5.1/sys/libkern/random.c 110422 2003-02-05 21:28:52Z ache $
   35  */
   36 
   37 #include <sys/libkern.h>
   38 
   39 #define NSHUFF 100      /* to drop part of seed -> 1st value correlation */
   40 
   41 static u_long randseed = 892053144; /* after srandom(1), NSHUFF counted */
   42 
   43 void
   44 srandom(seed)
   45         u_long seed;
   46 {
   47         int i;
   48 
   49         randseed = seed;
   50         for (i = 0; i < NSHUFF; i++)
   51                 (void)random();
   52 }
   53 
   54 /*
   55  * Pseudo-random number generator for randomizing the profiling clock,
   56  * and whatever else we might use it for.  The result is uniform on
   57  * [0, 2^31 - 1].
   58  */
   59 u_long
   60 random()
   61 {
   62         register long x, hi, lo, t;
   63 
   64         /*
   65          * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
   66          * From "Random number generators: good ones are hard to find",
   67          * Park and Miller, Communications of the ACM, vol. 31, no. 10,
   68          * October 1988, p. 1195.
   69          */
   70         /* Can't be initialized with 0, so use another value. */
   71         if ((x = randseed) == 0)
   72                 x = 123459876;
   73         hi = x / 127773;
   74         lo = x % 127773;
   75         t = 16807 * lo - 2836 * hi;
   76         if (t < 0)
   77                 t += 0x7fffffff;
   78         randseed = t;
   79         return (t);
   80 }

Cache object: 38e8f3c980068af6ca516226f64adc38


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.