sys/sys/ieee754.h

   1 /*      $NetBSD: ieee754.h,v 1.3 2003/10/27 01:11:47 kleink 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 #ifndef _SYS_TYPES_H_
  49 #include <sys/types.h>
  50 #endif
  51 #include <machine/endian.h>
  52
  53
  54 /*
  55  * <sys/ieee754.h> defines the layout of IEEE 754 floating point types.
  56  * Only single-precision and double-precision types are defined here;
  57  * extended types, if available, are defined in the machine-dependent
  58  * header.
  59  */
  60
  61 /*
  62  * Define the number of bits in each fraction and exponent.
  63  *
  64  *                   k           k+1
  65  * Note that  1.0 x 2  == 0.1 x 2      and that denorms are represented
  66  *
  67  *                                        (-exp_bias+1)
  68  * as fractions that look like 0.fffff x 2             .  This means that
  69  *
  70  *                       -126
  71  * the number 0.10000 x 2    , for instance, is the same as the normalized
  72  *
  73  *              -127                       -128
  74  * float 1.0 x 2    .  Thus, to represent 2    , we need one leading zero
  75  *
  76  *                                -129
  77  * in the fraction; to represent 2    , we need two, and so on.  This
  78  *
  79  *                                                   (-exp_bias-fracbits+1)
  80  * implies that the smallest denormalized number is 2
  81  *
  82  * for whichever format we are talking about: for single precision, for
  83  *
  84  *                                              -126            -149
  85  * instance, we get .00000000000000000000001 x 2    , or 1.0 x 2    , and
  86  *
  87  * -149 == -127 - 23 + 1.
  88  */
  89 #define SNG_EXPBITS     8
  90 #define SNG_FRACBITS    23
  91
  92 #define DBL_EXPBITS     11
  93 #define DBL_FRACBITS    52
  94
  95 struct ieee_single {
  96 #if _BYTE_ORDER == _BIG_ENDIAN
  97         u_int   sng_sign:1;
  98         u_int   sng_exp:8;
  99         u_int   sng_frac:23;
 100 #else
 101         u_int   sng_frac:23;
 102         u_int   sng_exp:8;
 103         u_int   sng_sign:1;
 104 #endif
 105 };
 106
 107 struct ieee_double {
 108 #if _BYTE_ORDER == _BIG_ENDIAN
 109         u_int   dbl_sign:1;
 110         u_int   dbl_exp:11;
 111         u_int   dbl_frach:20;
 112         u_int   dbl_fracl;
 113 #else
 114         u_int   dbl_fracl;
 115         u_int   dbl_frach:20;
 116         u_int   dbl_exp:11;
 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  * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its
 128  * high fraction; if the bit is set, it is a `quiet NaN'.
 129  */
 130 #define SNG_EXP_INFNAN  255
 131 #define DBL_EXP_INFNAN  2047
 132
 133 #if 0
 134 #define SNG_QUIETNAN    (1 << 22)
 135 #define DBL_QUIETNAN    (1 << 19)
 136 #endif
 137
 138 /*
 139  * Exponent biases.
 140  */
 141 #define SNG_EXP_BIAS    127
 142 #define DBL_EXP_BIAS    1023
 143
 144 /*
 145  * Convenience data structures.
 146  */
 147 union ieee_single_u {
 148         float                   sngu_f;
 149         struct ieee_single      sngu_sng;
 150 };
 151
 152 union ieee_double_u {
 153         double                  dblu_d;
 154         struct ieee_double      dblu_dbl;
 155 };