Home | History | Annotate | Download | only in sys 
      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_ */
    153