gen/FreeBSD/_rand48.c

   1 /*
   2  * Copyright (c) 1993 Martin Birgmeier
   3  * All rights reserved.
   4  *
   5  * You may redistribute unmodified or modified versions of this source
   6  * code provided that the above copyright notice and this and the
   7  * following conditions are retained.
   8  *
   9  * This software is provided ``as is'', and comes with no warranties
  10  * of any kind. I shall in no event be liable for anything that happens
  11  * to anyone/anything when using this software.
  12  */
  13
  14 #include <sys/cdefs.h>
  15 __FBSDID("$FreeBSD: src/lib/libc/gen/_rand48.c,v 1.2 2002/03/22 21:52:05 obrien Exp $");
  16
  17 #include "rand48.h"
  18
  19 unsigned short _rand48_seed[3] = {
  20         RAND48_SEED_0,
  21         RAND48_SEED_1,
  22         RAND48_SEED_2
  23 };
  24 unsigned short _rand48_mult[3] = {
  25         RAND48_MULT_0,
  26         RAND48_MULT_1,
  27         RAND48_MULT_2
  28 };
  29 unsigned short _rand48_add = RAND48_ADD;
  30
  31 void
  32 _dorand48(unsigned short xseed[3])
  33 {
  34         unsigned long accu;
  35         unsigned short temp[2];
  36
  37         accu = (unsigned long) _rand48_mult[0] * (unsigned long) xseed[0] +
  38          (unsigned long) _rand48_add;
  39         temp[0] = (unsigned short) accu;        /* lower 16 bits */
  40         accu >>= sizeof(unsigned short) * 8;
  41         accu += (unsigned long) _rand48_mult[0] * (unsigned long) xseed[1] +
  42          (unsigned long) _rand48_mult[1] * (unsigned long) xseed[0];
  43         temp[1] = (unsigned short) accu;        /* middle 16 bits */
  44         accu >>= sizeof(unsigned short) * 8;
  45         accu += _rand48_mult[0] * xseed[2] + _rand48_mult[1] * xseed[1] + _rand48_mult[2] * xseed[0];
  46         xseed[0] = temp[0];
  47         xseed[1] = temp[1];
  48         xseed[2] = (unsigned short) accu;
  49 }