FreeBSD/Linux Kernel Cross Reference
sys/sys/ieee754.h

     /*      $NetBSD: ieee754.h,v 1.3 2003/10/27 01:11:47 kleink Exp $       */
     
     /*
      * Copyright (c) 1992, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This software was developed by the Computer Systems Engineering group
      * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
      * contributed to Berkeley.
     *
     * All advertising materials mentioning features or use of this software
     * must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Lawrence Berkeley Laboratory.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)ieee.h      8.1 (Berkeley) 6/11/93
     */
    
    /*
     * NOTICE: This is not a standalone file.  To use it, #include it in
     * your port's ieee.h header.
     */
    
    #ifndef _SYS_TYPES_H_
    #include <sys/types.h>
    #endif
    #include <machine/endian.h>
    
    
    /*
     * <sys/ieee754.h> defines the layout of IEEE 754 floating point types.
     * Only single-precision and double-precision types are defined here;
     * extended types, if available, are defined in the machine-dependent
     * header.
     */
    
    /*
     * Define the number of bits in each fraction and exponent.
     *
     *                   k           k+1
     * Note that  1.0 x 2  == 0.1 x 2      and that denorms are represented
     *
     *                                        (-exp_bias+1)
     * as fractions that look like 0.fffff x 2             .  This means that
     *
     *                       -126
     * the number 0.10000 x 2    , for instance, is the same as the normalized
     *
     *              -127                       -128
     * float 1.0 x 2    .  Thus, to represent 2    , we need one leading zero
     *
     *                                -129
     * in the fraction; to represent 2    , we need two, and so on.  This
     *
     *                                                   (-exp_bias-fracbits+1)
     * implies that the smallest denormalized number is 2
     *
     * for whichever format we are talking about: for single precision, for
     *
     *                                              -126            -149
     * instance, we get .00000000000000000000001 x 2    , or 1.0 x 2    , and
     *
     * -149 == -127 - 23 + 1.
     */
    #define SNG_EXPBITS     8
    #define SNG_FRACBITS    23
    
    #define DBL_EXPBITS     11
    #define DBL_FRACBITS    52
    
    struct ieee_single {
    #if _BYTE_ORDER == _BIG_ENDIAN
            u_int   sng_sign:1;
            u_int   sng_exp:8;
            u_int   sng_frac:23;
   #else
           u_int   sng_frac:23;
           u_int   sng_exp:8;
           u_int   sng_sign:1;
   #endif
   };
   
   struct ieee_double {
   #if _BYTE_ORDER == _BIG_ENDIAN
           u_int   dbl_sign:1;
           u_int   dbl_exp:11;
           u_int   dbl_frach:20;
           u_int   dbl_fracl;
   #else
           u_int   dbl_fracl;
           u_int   dbl_frach:20;
           u_int   dbl_exp:11;
           u_int   dbl_sign:1;
   #endif
   };
   
   /*
    * Floats whose exponent is in [1..INFNAN) (of whatever type) are
    * `normal'.  Floats whose exponent is INFNAN are either Inf or NaN.
    * Floats whose exponent is zero are either zero (iff all fraction
    * bits are zero) or subnormal values.
    *
    * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its
    * high fraction; if the bit is set, it is a `quiet NaN'.
    */
   #define SNG_EXP_INFNAN  255
   #define DBL_EXP_INFNAN  2047
   
   #if 0
   #define SNG_QUIETNAN    (1 << 22)
   #define DBL_QUIETNAN    (1 << 19)
   #endif
   
   /*
    * Exponent biases.
    */
   #define SNG_EXP_BIAS    127
   #define DBL_EXP_BIAS    1023
   
   /*
    * Convenience data structures.
    */
   union ieee_single_u {
           float                   sngu_f;
           struct ieee_single      sngu_sng;
   };
   
   union ieee_double_u {
           double                  dblu_d;
           struct ieee_double      dblu_dbl;
   };

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