The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/mips/include/ieee.h

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    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: releng/8.0/sys/mips/include/ieee.h 178172 2008-04-13 07:27:37Z imp $
   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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