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105 lines
3.4 KiB
C
105 lines
3.4 KiB
C
/*
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* $Id: math_trunc.c,v 1.3 2006-01-08 12:04:24 obarthel Exp $
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*
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* :ts=4
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*
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* Portable ISO 'C' (1994) runtime library for the Amiga computer
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* Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
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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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*
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* - 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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*
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* - Neither the name of Olaf Barthel nor the names of contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND 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 COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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*
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* PowerPC math library based in part on work by Sun Microsystems
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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*/
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#ifndef _MATH_HEADERS_H
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#include "math_headers.h"
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#endif /* _MATH_HEADERS_H */
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/****************************************************************************/
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#if defined(FLOATING_POINT_SUPPORT)
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/****************************************************************************/
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double
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trunc(double x)
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{
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int signbit;
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/* Most significant word, least significant word. */
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int msw;
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unsigned int lsw;
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int exponent_less_1023;
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EXTRACT_WORDS(msw, lsw, x);
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/* Extract sign bit. */
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signbit = msw & 0x80000000;
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/* Extract exponent field. */
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exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;
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if (exponent_less_1023 < 20)
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{
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/* All significant digits are in msw. */
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if (exponent_less_1023 < 0)
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{
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/* -1 < x < 1, so result is +0 or -0. */
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INSERT_WORDS(x, signbit, 0);
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}
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else
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{
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/* All relevant fraction bits are in msw, so lsw of the result is 0. */
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INSERT_WORDS(x, signbit | (msw & ~(0x000fffff >> exponent_less_1023)), 0);
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}
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}
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else if (exponent_less_1023 > 51)
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{
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if (exponent_less_1023 == 1024)
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{
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/* x is infinite, or not a number, so trigger an exception. */
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return x + x;
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}
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/* All bits in the fraction fields of the msw and lsw are needed in the result. */
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}
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else
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{
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/* All fraction bits in msw are relevant. Truncate irrelevant
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bits from lsw. */
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INSERT_WORDS(x, msw, lsw & ~(0xffffffffu >> (exponent_less_1023 - 20)));
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}
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return x;
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}
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/****************************************************************************/
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#endif /* FLOATING_POINT_SUPPORT */
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