lib/libc/stdlib/_rand48.c

   1 /*      $NetBSD: _rand48.c,v 1.7 2005/06/12 05:21:27 lukem Exp $        */
   2
   3 /*
   4  * Copyright (c) 1993 Martin Birgmeier
   5  * All rights reserved.
   6  *
   7  * You may redistribute unmodified or modified versions of this source
   8  * code provided that the above copyright notice and this and the
   9  * following conditions are retained.
  10  *
  11  * This software is provided ``as is'', and comes with no warranties
  12  * of any kind. I shall in no event be liable for anything that happens
  13  * to anyone/anything when using this software.
  14  */
  15
  16 #include <sys/cdefs.h>
  17 #if defined(LIBC_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: _rand48.c,v 1.7 2005/06/12 05:21:27 lukem Exp $");
  19 #endif /* LIBC_SCCS and not lint */
  20
  21 #include <assert.h>
  22
  23 #include "rand48.h"
  24
  25 unsigned short __rand48_seed[3] = {
  26         RAND48_SEED_0,
  27         RAND48_SEED_1,
  28         RAND48_SEED_2
  29 };
  30 unsigned short __rand48_mult[3] = {
  31         RAND48_MULT_0,
  32         RAND48_MULT_1,
  33         RAND48_MULT_2
  34 };
  35 unsigned short __rand48_add = RAND48_ADD;
  36
  37 void
  38 __dorand48(unsigned short xseed[3])
  39 {
  40         unsigned long accu;
  41         unsigned short temp[2];
  42
  43         _DIAGASSERT(xseed != NULL);
  44
  45         accu = (unsigned long) __rand48_mult[0] * (unsigned long) xseed[0] +
  46          (unsigned long) __rand48_add;
  47         temp[0] = (unsigned short) accu;        /* lower 16 bits */
  48         accu >>= sizeof(unsigned short) * 8;
  49         accu += (unsigned long) __rand48_mult[0] * (unsigned long) xseed[1] +
  50          (unsigned long) __rand48_mult[1] * (unsigned long) xseed[0];
  51         temp[1] = (unsigned short) accu;        /* middle 16 bits */
  52         accu >>= sizeof(unsigned short) * 8;
  53         accu += __rand48_mult[0] * xseed[2] + __rand48_mult[1] * xseed[1] + __rand48_mult[2] * xseed[0];
  54         xseed[0] = temp[0];
  55         xseed[1] = temp[1];
  56         xseed[2] = (unsigned short) accu;
  57 }