78 lines
2.8 KiB
C
78 lines
2.8 KiB
C
/* $NetBSD: frexp_ieee754.c,v 1.4 2003/10/27 00:05:46 kleink Exp $ */
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/*
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This software was developed by the Computer Systems Engineering group
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* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
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* contributed to Berkeley.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: Header: frexp.c,v 1.1 91/07/07 04:45:01 torek Exp
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*/
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#include <sys/cdefs.h>
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#if defined(LIBC_SCCS) && !defined(lint)
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#if 0
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static char sccsid[] = "@(#)frexp.c 8.1 (Berkeley) 6/4/93";
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#else
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__RCSID("$NetBSD: frexp_ieee754.c,v 1.4 2003/10/27 00:05:46 kleink Exp $");
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#endif
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#endif /* LIBC_SCCS and not lint */
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#include <sys/types.h>
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#include <machine/ieee.h>
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#include <math.h>
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/*
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* Split the given value into a fraction in the range [0.5, 1.0) and
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* an exponent, such that frac * (2^exp) == value. If value is 0,
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* return 0.
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*/
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double
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frexp(double value, int *eptr)
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{
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union ieee_double_u u;
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if (value) {
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/*
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* Fractions in [0.5..1.0) have an exponent of 2^-1.
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* Leave Inf and NaN alone, however.
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* WHAT ABOUT DENORMS?
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*/
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u.dblu_d = value;
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if (u.dblu_dbl.dbl_exp != DBL_EXP_INFNAN) {
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*eptr = u.dblu_dbl.dbl_exp - (DBL_EXP_BIAS - 1);
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u.dblu_dbl.dbl_exp = DBL_EXP_BIAS - 1;
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}
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return (u.dblu_d);
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} else {
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*eptr = 0;
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return (0.0);
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}
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}
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