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1  /*	$NetBSD: ieee754.h,v 1.6.24.1 2007/05/07 19:49:10 pavel Exp $	*/
2  
3  /*
4   * Copyright (c) 1992, 1993
5   *	The Regents of the University of California.  All rights reserved.
6   *
7   * This software was developed by the Computer Systems Engineering group
8   * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9   * contributed to Berkeley.
10   *
11   * All advertising materials mentioning features or use of this software
12   * must display the following acknowledgement:
13   *	This product includes software developed by the University of
14   *	California, Lawrence Berkeley Laboratory.
15   *
16   * Redistribution and use in source and binary forms, with or without
17   * modification, are permitted provided that the following conditions
18   * are met:
19   * 1. Redistributions of source code must retain the above copyright
20   *    notice, this list of conditions and the following disclaimer.
21   * 2. Redistributions in binary form must reproduce the above copyright
22   *    notice, this list of conditions and the following disclaimer in the
23   *    documentation and/or other materials provided with the distribution.
24   * 3. Neither the name of the University nor the names of its contributors
25   *    may be used to endorse or promote products derived from this software
26   *    without specific prior written permission.
27   *
28   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38   * SUCH DAMAGE.
39   *
40   *	@(#)ieee.h	8.1 (Berkeley) 6/11/93
41   */
42  #ifndef _SYS_IEEE754_H_
43  #define _SYS_IEEE754_H_
44  
45  /*
46   * NOTICE: This is not a standalone file.  To use it, #include it in
47   * your port's ieee.h header.
48   */
49  
50  #include <machine/endian.h>
51  
52  /*
53   * <sys/ieee754.h> defines the layout of IEEE 754 floating point types.
54   * Only single-precision and double-precision types are defined here;
55   * extended types, if available, are defined in the machine-dependent
56   * header.
57   */
58  
59  /*
60   * Define the number of bits in each fraction and exponent.
61   *
62   *		     k	         k+1
63   * Note that  1.0 x 2  == 0.1 x 2      and that denorms are represented
64   *
65   *					  (-exp_bias+1)
66   * as fractions that look like 0.fffff x 2             .  This means that
67   *
68   *			 -126
69   * the number 0.10000 x 2    , for instance, is the same as the normalized
70   *
71   *		-127			   -128
72   * float 1.0 x 2    .  Thus, to represent 2    , we need one leading zero
73   *
74   *				  -129
75   * in the fraction; to represent 2    , we need two, and so on.  This
76   *
77   *						     (-exp_bias-fracbits+1)
78   * implies that the smallest denormalized number is 2
79   *
80   * for whichever format we are talking about: for single precision, for
81   *
82   *						-126		-149
83   * instance, we get .00000000000000000000001 x 2    , or 1.0 x 2    , and
84   *
85   * -149 == -127 - 23 + 1.
86   */
87  #define	SNG_EXPBITS	8
88  #define	SNG_FRACBITS	23
89  
90  struct ieee_single {
91  #if _BYTE_ORDER == _BIG_ENDIAN
92  	u_int	sng_sign:1;
93  	u_int	sng_exp:SNG_EXPBITS;
94  	u_int	sng_frac:SNG_FRACBITS;
95  #else
96  	u_int	sng_frac:SNG_FRACBITS;
97  	u_int	sng_exp:SNG_EXPBITS;
98  	u_int	sng_sign:1;
99  #endif
100  };
101  
102  #define	DBL_EXPBITS	11
103  #define	DBL_FRACHBITS	20
104  #define	DBL_FRACLBITS	32
105  #define	DBL_FRACBITS	(DBL_FRACHBITS + DBL_FRACLBITS)
106  
107  struct ieee_double {
108  #if _BYTE_ORDER == _BIG_ENDIAN
109  	u_int	dbl_sign:1;
110  	u_int	dbl_exp:DBL_EXPBITS;
111  	u_int	dbl_frach:DBL_FRACHBITS;
112  	u_int	dbl_fracl:DBL_FRACLBITS;
113  #else
114  	u_int	dbl_fracl:DBL_FRACLBITS;
115  	u_int	dbl_frach:DBL_FRACHBITS;
116  	u_int	dbl_exp:DBL_EXPBITS;
117  	u_int	dbl_sign:1;
118  #endif
119  };
120  
121  /*
122   * Floats whose exponent is in [1..INFNAN) (of whatever type) are
123   * `normal'.  Floats whose exponent is INFNAN are either Inf or NaN.
124   * Floats whose exponent is zero are either zero (iff all fraction
125   * bits are zero) or subnormal values.
126   *
127   * At least one `signalling NaN' and one `quiet NaN' value must be
128   * implemented.  It is left to the architecture to specify how to
129   * distinguish between these.
130   */
131  #define	SNG_EXP_INFNAN	255
132  #define	DBL_EXP_INFNAN	2047
133  
134  /*
135   * Exponent biases.
136   */
137  #define	SNG_EXP_BIAS	127
138  #define	DBL_EXP_BIAS	1023
139  
140  /*
141   * Convenience data structures.
142   */
143  union ieee_single_u {
144  	float			sngu_f;
145  	struct ieee_single	sngu_sng;
146  };
147  
148  union ieee_double_u {
149  	double			dblu_d;
150  	struct ieee_double	dblu_dbl;
151  };
152  #endif /* _SYS_IEEE754_H_ */
153