StdLib/Include/sys/ieee754.h

   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_ */