compiler/posixc/__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 "rand48.h"
  15
  16 unsigned short _rand48_seed[3] = {
  17         RAND48_SEED_0,
  18         RAND48_SEED_1,
  19         RAND48_SEED_2
  20 };
  21 unsigned short _rand48_mult[3] = {
  22         RAND48_MULT_0,
  23         RAND48_MULT_1,
  24         RAND48_MULT_2
  25 };
  26 unsigned short _rand48_add = RAND48_ADD;
  27
  28 void
  29 _dorand48(unsigned short xseed[3])
  30 {
  31         unsigned long accu;
  32         unsigned short temp[2];
  33
  34         accu = (unsigned long) _rand48_mult[0] * (unsigned long) xseed[0] +
  35          (unsigned long) _rand48_add;
  36         temp[0] = (unsigned short) accu;        /* lower 16 bits */
  37         accu >>= sizeof(unsigned short) * 8;
  38         accu += (unsigned long) _rand48_mult[0] * (unsigned long) xseed[1] +
  39          (unsigned long) _rand48_mult[1] * (unsigned long) xseed[0];
  40         temp[1] = (unsigned short) accu;        /* middle 16 bits */
  41         accu >>= sizeof(unsigned short) * 8;
  42         accu += _rand48_mult[0] * xseed[2] + _rand48_mult[1] * xseed[1] + _rand48_mult[2] * xseed[0];
  43         xseed[0] = temp[0];
  44         xseed[1] = temp[1];
  45         xseed[2] = (unsigned short) accu;
  46 }