63 lines
1.9 KiB
C++
63 lines
1.9 KiB
C++
/**********************************************************************
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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) 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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*
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* Last port: index/quadtree/IntervalSize.java rev 1.7 (JTS-1.10)
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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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namespace geos {
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namespace index { // geos::index
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namespace quadtree { // geos::index::quadtree
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/**
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* \class IntervalSize
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*
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* \brief
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* Provides a test for whether an interval is
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* so small it should be considered as zero for the purposes of
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* inserting it into a binary tree.
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*
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* The reason this check is necessary is that round-off error can
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* cause the algorithm used to subdivide an interval to fail, by
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* computing a midpoint value which does not lie strictly between the
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* endpoints.
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*/
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class GEOS_DLL IntervalSize {
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public:
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/**
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* This value is chosen to be a few powers of 2 less than the
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* number of bits available in the double representation (i.e. 53).
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* This should allow enough extra precision for simple computations
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* to be correct, at least for comparison purposes.
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*/
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static const int MIN_BINARY_EXPONENT = -50;
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/**
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* Computes whether the interval [min, max] is effectively zero width.
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* I.e. the width of the interval is so much less than the
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* location of the interval that the midpoint of the interval
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* cannot be represented precisely.
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*/
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static bool isZeroWidth(double min, double max);
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};
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} // namespace geos::index::quadtree
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} // namespace geos::index
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} // namespace geos
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