72 lines
2.3 KiB
C
72 lines
2.3 KiB
C
/* $OpenBSD: frexp.c,v 1.10 2013/07/03 04:46:36 espie Exp $ */
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/*-
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* Copyright (c) 2004 David Schultz <das@FreeBSD.ORG>
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* All rights reserved.
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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* $FreeBSD: frexp.c,v 1.1 2004/07/18 21:23:39 das Exp $
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*/
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#include <sys/types.h>
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#include <machine/ieee.h>
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#include <float.h>
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#include <math.h>
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double
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frexp(double v, int *ex)
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{
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union {
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double v;
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struct ieee_double s;
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} u;
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u.v = v;
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switch (u.s.dbl_exp) {
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case 0: /* 0 or subnormal */
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if ((u.s.dbl_fracl | u.s.dbl_frach) == 0) {
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*ex = 0;
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} else {
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/*
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* The power of 2 is arbitrary, any value from 54 to
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* 1024 will do.
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*/
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u.v *= 0x1.0p514;
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*ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1 + 514);
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u.s.dbl_exp = DBL_EXP_BIAS - 1;
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}
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break;
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case DBL_EXP_INFNAN: /* Inf or NaN; value of *ex is unspecified */
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break;
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default: /* normal */
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*ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1);
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u.s.dbl_exp = DBL_EXP_BIAS - 1;
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break;
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}
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return (u.v);
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}
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#if LDBL_MANT_DIG == DBL_MANT_DIG
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__strong_alias(frexpl, frexp);
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#endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
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