mirror of https://gitlab.com/rnger/amath
131 lines
3.9 KiB
C
131 lines
3.9 KiB
C
/*-
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* Copyright (c) 2014-2017 Carsten Sonne Larsen <cs@innolan.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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* 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 ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Project homepage:
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* https://amath.innolan.net
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*
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* The original source code can be obtained from:
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* http://www.netlib.org/fdlibm/s_floor.c
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*
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* =================================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, 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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*/
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/**
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* @file floor.c
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* @brief Floor function
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*/
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#include "prim.h"
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static const double huge = 1.0e300;
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/**
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* @brief Floor function
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* @return x rounded toward -inf to integral value
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* @details
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* <pre>
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* Method:
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* Bit twiddling
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*
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* Exception:
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* Inexact flag raised if x not equal to floor(x)
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* </pre>
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*/
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double floor(double x)
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{
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int32_t i0, i1, j0;
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uint32_t i, j;
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EXTRACT_WORDS(i0, i1, x);
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j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
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if (j0 < 20)
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{
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if (j0 < 0)
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{ /* raise inexact if x != 0 */
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if (huge + x > 0.0)
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{ /* return 0*sign(x) if |x|<1 */
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if (i0 >= 0)
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{
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i0 = i1 = 0;
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}
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else if (((i0 & 0x7fffffff) | i1) != 0)
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{
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i0 = 0xbff00000;
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i1 = 0;
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}
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}
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}
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else
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{
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i = (0x000fffff) >> j0;
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if (((i0 & i) | i1) == 0)
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return x; /* x is integral */
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if (huge + x > 0.0)
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{ /* raise inexact flag */
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if (i0 < 0)
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i0 += (0x00100000) >> j0;
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i0 &= (~i);
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i1 = 0;
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}
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}
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}
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else if (j0 > 51)
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{
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if (j0 == 0x400)
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return x + x; /* inf or NaN */
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else
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return x; /* x is integral */
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}
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else
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{
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i = ((uint32_t)(0xffffffff)) >> (j0 - 20);
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if ((i1 & i) == 0)
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return x; /* x is integral */
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if (huge + x > 0.0)
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{ /* raise inexact flag */
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if (i0 < 0)
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{
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if (j0 == 20)
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i0 += 1;
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else
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{
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j = i1 + (1 << (52 - j0));
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if (j < (uint32_t)i1)
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i0 += 1; /* got a carry */
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i1 = j;
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}
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}
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i1 &= (~i);
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}
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}
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INSERT_WORDS(x, i0, i1);
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return x;
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}
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