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      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 }
     48