sys/sys/ieee754.h

   1 /*      $NetBSD: ieee754.h,v 1.3 2003/10/27 01:11:47 kleink Exp $       */
   2 /* $DragonFly: src/sys/sys/ieee754.h,v 1.3 2006/05/20 02:42:13 dillon Exp $ */
   3
   4 /*
   5  * Copyright (c) 1992, 1993
   6  *      The Regents of the University of California.  All rights reserved.
   7  *
   8  * This software was developed by the Computer Systems Engineering group
   9  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
  10  * contributed to Berkeley.
  11  *
  12  * All advertising materials mentioning features or use of this software
  13  * must display the following acknowledgement:
  14  *      This product includes software developed by the University of
  15  *      California, Lawrence Berkeley Laboratory.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  * 3. Neither the name of the University nor the names of its contributors
  26  *    may be used to endorse or promote products derived from this software
  27  *    without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  39  * SUCH DAMAGE.
  40  *
  41  *      @(#)ieee.h      8.1 (Berkeley) 6/11/93
  42  */
  43
  44 /*
  45  * NOTICE: This is not a standalone file.  To use it, #include it in
  46  * your port's ieee.h header.
  47  */
  48
  49 #ifndef _SYS_TYPES_H_
  50 #include <sys/types.h>
  51 #endif
  52 #ifndef _MACHINE_ENDIAN_H_
  53 #include <machine/endian.h>
  54 #endif
  55
  56
  57 /*
  58  * <sys/ieee754.h> defines the layout of IEEE 754 floating point types.
  59  * Only single-precision and double-precision types are defined here;
  60  * extended types, if available, are defined in the machine-dependent
  61  * header.
  62  */
  63
  64 /*
  65  * Define the number of bits in each fraction and exponent.
  66  *
  67  *                   k           k+1
  68  * Note that  1.0 x 2  == 0.1 x 2      and that denorms are represented
  69  *
  70  *                                        (-exp_bias+1)
  71  * as fractions that look like 0.fffff x 2             .  This means that
  72  *
  73  *                       -126
  74  * the number 0.10000 x 2    , for instance, is the same as the normalized
  75  *
  76  *              -127                       -128
  77  * float 1.0 x 2    .  Thus, to represent 2    , we need one leading zero
  78  *
  79  *                                -129
  80  * in the fraction; to represent 2    , we need two, and so on.  This
  81  *
  82  *                                                   (-exp_bias-fracbits+1)
  83  * implies that the smallest denormalized number is 2
  84  *
  85  * for whichever format we are talking about: for single precision, for
  86  *
  87  *                                              -126            -149
  88  * instance, we get .00000000000000000000001 x 2    , or 1.0 x 2    , and
  89  *
  90  * -149 == -127 - 23 + 1.
  91  */
  92 #define SNG_EXPBITS     8
  93 #define SNG_FRACBITS    23
  94
  95 #define DBL_EXPBITS     11
  96 #define DBL_FRACBITS    52
  97
  98 struct ieee_single {
  99 #if _BYTE_ORDER == _BIG_ENDIAN
 100         u_int   sng_sign:1;
 101         u_int   sng_exp:8;
 102         u_int   sng_frac:23;
 103 #else
 104         u_int   sng_frac:23;
 105         u_int   sng_exp:8;
 106         u_int   sng_sign:1;
 107 #endif
 108 };
 109
 110 struct ieee_double {
 111 #if _BYTE_ORDER == _BIG_ENDIAN
 112         u_int   dbl_sign:1;
 113         u_int   dbl_exp:11;
 114         u_int   dbl_frach:20;
 115         u_int   dbl_fracl;
 116 #else
 117         u_int   dbl_fracl;
 118         u_int   dbl_frach:20;
 119         u_int   dbl_exp:11;
 120         u_int   dbl_sign:1;
 121 #endif
 122 };
 123
 124 /*
 125  * Floats whose exponent is in [1..INFNAN) (of whatever type) are
 126  * `normal'.  Floats whose exponent is INFNAN are either Inf or NaN.
 127  * Floats whose exponent is zero are either zero (iff all fraction
 128  * bits are zero) or subnormal values.
 129  *
 130  * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its
 131  * high fraction; if the bit is set, it is a `quiet NaN'.
 132  */
 133 #define SNG_EXP_INFNAN  255
 134 #define DBL_EXP_INFNAN  2047
 135
 136 #if 0
 137 #define SNG_QUIETNAN    (1 << 22)
 138 #define DBL_QUIETNAN    (1 << 19)
 139 #endif
 140
 141 /*
 142  * Exponent biases.
 143  */
 144 #define SNG_EXP_BIAS    127
 145 #define DBL_EXP_BIAS    1023
 146
 147 /*
 148  * Convenience data structures.
 149  */
 150 union ieee_single_u {
 151         float                   sngu_f;
 152         struct ieee_single      sngu_sng;
 153 };
 154
 155 union ieee_double_u {
 156         double                  dblu_d;
 157         struct ieee_double      dblu_dbl;
 158 };