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