/********************************************************************** * * GEOS - Geometry Engine Open Source * http://geos.osgeo.org * * Copyright (C) 2006 Refractions Research Inc. * * This is free software; you can redistribute and/or modify it under * the terms of the GNU Lesser General Public Licence as published * by the Free Software Foundation. * See the COPYING file for more information. * ********************************************************************** * * Last port: index/quadtree/DoubleBits.java rev. 1.7 (JTS-1.10) * **********************************************************************/ #ifndef GEOS_IDX_QUADTREE_DOUBLEBITS_H #define GEOS_IDX_QUADTREE_DOUBLEBITS_H #include #include // for int64 #include namespace geos { namespace index { // geos::index namespace quadtree { // geos::index::quadtree /** \brief * DoubleBits manipulates Double numbers * by using bit manipulation and bit-field extraction. * * For some operations (such as determining the exponent) * this is more accurate than using mathematical operations * (which suffer from round-off error). * * The algorithms and constants in this class * apply only to IEEE-754 double-precision floating point format. * */ class GEOS_DLL DoubleBits { public: static const int EXPONENT_BIAS = 1023; static double powerOf2(int exp); static int exponent(double d); static double truncateToPowerOfTwo(double d); static std::string toBinaryString(double d); static double maximumCommonMantissa(double d1, double d2); DoubleBits(double nx); double getDouble() const; /// Determines the exponent for the number int64 biasedExponent() const; /// Determines the exponent for the number int getExponent() const; void zeroLowerBits(int nBits); int getBit(int i) const; /** \brief * This computes the number of common most-significant bits in * the mantissa. * * It does not count the hidden bit, which is always 1. * It does not determine whether the numbers have the same exponent; * if they do not, the value computed by this function is meaningless. * * @param db * * @return the number of common most-significant mantissa bits */ int numCommonMantissaBits(const DoubleBits& db) const; /// A representation of the Double bits formatted for easy readability std::string toString() const; private: double x; int64 xBits; }; } // namespace geos::index::quadtree } // namespace geos::index } // namespace geos #endif // GEOS_IDX_QUADTREE_DOUBLEBITS_H