98 lines
2.4 KiB
C
98 lines
2.4 KiB
C
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/**********************************************************************
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*
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* GEOS - Geometry Engine Open Source
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* http://geos.osgeo.org
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*
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* Copyright (C) 2005-2006 Refractions Research Inc.
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*
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* This is free software; you can redistribute and/or modify it under
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* the terms of the GNU Lesser General Public Licence as published
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* by the Free Software Foundation.
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* See the COPYING file for more information.
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*
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**********************************************************************/
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#pragma once
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#include <geos/export.h>
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#include <cstdint>
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namespace geos {
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namespace precision { // geos.precision
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/** \brief
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* Determines the maximum number of common most-significant
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* bits in the mantissa of one or numbers.
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*
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* Can be used to compute the double-precision number which
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* is represented by the common bits.
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* If there are no common bits, the number computed is 0.0.
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*
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*/
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class GEOS_DLL CommonBits {
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private:
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bool isFirst;
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int commonMantissaBitsCount;
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int64_t commonBits;
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int64_t commonSignExp;
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public:
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/** \brief
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* Computes the bit pattern for the sign and exponent of a
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* double-precision number.
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*
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* @param num
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* @return the bit pattern for the sign and exponent
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*/
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static int64_t signExpBits(int64_t num);
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/** \brief
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* This computes the number of common most-significant
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* bits in the mantissas of two double-precision numbers.
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*
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* It does not count the hidden bit, which is always 1.
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* It does not determine whether the numbers have the same
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* exponent - if they do not, the value computed by this
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* function is meaningless.
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* @param num1
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* @param num2
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* @return the number of common most-significant mantissa bits
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*/
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static int numCommonMostSigMantissaBits(int64_t num1, int64_t num2);
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/** \brief
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* Zeroes the lower n bits of a bitstring.
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*
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* @param bits the bitstring to alter
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* @param nBits the number of bits to zero
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* @return the zeroed bitstring
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*/
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static int64_t zeroLowerBits(int64_t bits, int nBits);
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/** \brief
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* Extracts the i'th bit of a bitstring.
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*
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* @param bits the bitstring to extract from
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* @param i the bit to extract
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* @return the value of the extracted bit
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*/
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static int getBit(int64_t bits, int i);
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CommonBits();
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void add(double num);
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double getCommon();
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};
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} // namespace geos.precision
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} // namespace geos
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