workbench/network/stacks/AROSTCP/netlib/random.c

   1 /*-
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 2005 Pavel Fedin
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 4. Neither the name of the University nor the names of its contributors
  15  *    may be used to endorse or promote products derived from this software
  16  *    without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  *
  30  *      @(#)random.c    8.1 (Berkeley) 6/10/93
  31  */
  32
  33 #include <sys/cdefs.h>
  34 #include <sys/types.h>
  35 #include <stdlib.h>
  36
  37 #define NSHUFF 50       /* to drop some "seed -> 1st value" linearity */
  38
  39 static u_long randseed = 937186357; /* after srandom(1), NSHUFF counted */
  40
  41 void
  42 srandom(seed)
  43         unsigned seed;
  44 {
  45         int i;
  46
  47         randseed = seed;
  48         for (i = 0; i < NSHUFF; i++)
  49                 (void)random();
  50 }
  51
  52 /*
  53  * Pseudo-random number generator for randomizing the profiling clock,
  54  * and whatever else we might use it for.  The result is uniform on
  55  * [0, 2^31 - 1].
  56  */
  57 long
  58 random()
  59 {
  60         register long x, hi, lo, t;
  61
  62         /*
  63          * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
  64          * From "Random number generators: good ones are hard to find",
  65          * Park and Miller, Communications of the ACM, vol. 31, no. 10,
  66          * October 1988, p. 1195.
  67          */
  68         /* Can't be initialized with 0, so use another value. */
  69         if ((x = randseed) == 0)
  70                 x = 123459876;
  71         hi = x / 127773;
  72         lo = x % 127773;
  73         t = 16807 * lo - 2836 * hi;
  74         if (t < 0)
  75                 t += 0x7fffffff;
  76         randseed = t;
  77         return (t);
  78 }