1 /* $NetBSD: ieee754.h,v 1.4 2003/10/27 02:30:26 simonb 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 * $FreeBSD$
43 *
44 */
45
46 /*
47 * NOTICE: This is not a standalone file. To use it, #include it in
48 * your port's ieee.h header.
49 */
50
51 #include <machine/endian.h>
52
53 /*
54 * <sys/ieee754.h> defines the layout of IEEE 754 floating point types.
55 * Only single-precision and double-precision types are defined here;
56 * extended types, if available, are defined in the machine-dependent
57 * header.
58 */
59
60 /*
61 * Define the number of bits in each fraction and exponent.
62 *
63 * k k+1
64 * Note that 1.0 x 2 == 0.1 x 2 and that denorms are represented
65 *
66 * (-exp_bias+1)
67 * as fractions that look like 0.fffff x 2 . This means that
68 *
69 * -126
70 * the number 0.10000 x 2 , for instance, is the same as the normalized
71 *
72 * -127 -128
73 * float 1.0 x 2 . Thus, to represent 2 , we need one leading zero
74 *
75 * -129
76 * in the fraction; to represent 2 , we need two, and so on. This
77 *
78 * (-exp_bias-fracbits+1)
79 * implies that the smallest denormalized number is 2
80 *
81 * for whichever format we are talking about: for single precision, for
82 *
83 * -126 -149
84 * instance, we get .00000000000000000000001 x 2 , or 1.0 x 2 , and
85 *
86 * -149 == -127 - 23 + 1.
87 */
88 #define SNG_EXPBITS 8
89 #define SNG_FRACBITS 23
90
91 #define DBL_EXPBITS 11
92 #define DBL_FRACBITS 52
93
94 struct ieee_single {
95 #if _BYTE_ORDER == _BIG_ENDIAN
96 u_int sng_sign:1;
97 u_int sng_exp:8;
98 u_int sng_frac:23;
99 #else
100 u_int sng_frac:23;
101 u_int sng_exp:8;
102 u_int sng_sign:1;
103 #endif
104 };
105
106 struct ieee_double {
107 #if _BYTE_ORDER == _BIG_ENDIAN
108 u_int dbl_sign:1;
109 u_int dbl_exp:11;
110 u_int dbl_frach:20;
111 u_int dbl_fracl;
112 #else
113 u_int dbl_fracl;
114 u_int dbl_frach:20;
115 u_int dbl_exp:11;
116 u_int dbl_sign:1;
117 #endif
118 };
119
120 /*
121 * Floats whose exponent is in [1..INFNAN) (of whatever type) are
122 * `normal'. Floats whose exponent is INFNAN are either Inf or NaN.
123 * Floats whose exponent is zero are either zero (iff all fraction
124 * bits are zero) or subnormal values.
125 *
126 * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its
127 * high fraction; if the bit is set, it is a `quiet NaN'.
128 */
129 #define SNG_EXP_INFNAN 255
130 #define DBL_EXP_INFNAN 2047
131
132 #if 0
133 #define SNG_QUIETNAN (1 << 22)
134 #define DBL_QUIETNAN (1 << 19)
135 #endif
136
137 /*
138 * Exponent biases.
139 */
140 #define SNG_EXP_BIAS 127
141 #define DBL_EXP_BIAS 1023
142
143 /*
144 * Convenience data structures.
145 */
146 union ieee_single_u {
147 float sngu_f;
148 struct ieee_single sngu_sng;
149 };
150
151 union ieee_double_u {
152 double dblu_d;
153 struct ieee_double dblu_dbl;
154 };
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