lib/libc/stdlib/erand48_ieee754.c

   1 /*      $NetBSD: erand48_ieee754.c,v 1.2 2006/03/31 11:42:31 drochner 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: erand48_ieee754.c,v 1.2 2006/03/31 11:42:31 drochner Exp $");
  19 #endif /* LIBC_SCCS and not lint */
  20
  21 #include "namespace.h"
  22
  23 #include <assert.h>
  24 #include <machine/ieee.h>
  25
  26 #include "rand48.h"
  27
  28 #ifdef __weak_alias
  29 __weak_alias(erand48,_erand48)
  30 #endif
  31
  32 double
  33 erand48(unsigned short xseed[3])
  34 {
  35         union ieee_double_u u;
  36
  37         _DIAGASSERT(xseed != NULL);
  38
  39         __dorand48(xseed);
  40         u.dblu_dbl.dbl_sign = 0;
  41         u.dblu_dbl.dbl_exp = DBL_EXP_BIAS; /* so we get [1,2) */
  42         u.dblu_dbl.dbl_frach = ((unsigned int)xseed[2] << 4)
  43                                 | ((unsigned int)xseed[1] >> 12);
  44         u.dblu_dbl.dbl_fracl = (((unsigned int)xseed[1] & 0x0fff) << 20)
  45                                 | ((unsigned int)xseed[0] << 4);
  46         return (u.dblu_d - 1);
  47 }