CGAlgorithmsDD.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2014 Mateusz Loskot <mateusz@loskot.net>
 *
 * 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: algorithm/CGAlgorithmsDD.java r789 (JTS-1.14)
 *
 **********************************************************************/
 
#pragma once
 
#include <geos/export.h>
#include <geos/math/DD.h>
 
// Forward declarations
namespace geos {
namespace geom {
class Coordinate;
class CoordinateSequence;
}
}
 
using namespace geos::math;
 
namespace geos {
namespace algorithm { // geos::algorithm
 
class GEOS_DLL CGAlgorithmsDD {
 
public:
 
    enum {
        CLOCKWISE = -1,
        COLLINEAR = 0,
        COUNTERCLOCKWISE = 1
    };
 
    enum {
        RIGHT = -1,
        LEFT = 1,
        STRAIGHT = 0,
        FAILURE = 2
    };
 
    static int orientationIndex(const geom::Coordinate& p1,
                                const geom::Coordinate& p2,
                                const geom::Coordinate& q);
 
 
    static int orientationIndex(double p1x, double p1y,
                                double p2x, double p2y,
                                double qx,  double qy);
 
    static int orientationIndexFilter(
        double pax, double pay,
        double pbx, double pby,
        double pcx, double pcy)
    {
        double constexpr DP_SAFE_EPSILON =  1e-15;
 
        double detsum;
        double const detleft = (pax - pcx) * (pby - pcy);
        double const detright = (pay - pcy) * (pbx - pcx);
        double const det = detleft - detright;
 
        if(detleft > 0.0) {
            if(detright <= 0.0) {
                return orientation(det);
            }
            else {
                detsum = detleft + detright;
            }
        }
        else if(detleft < 0.0) {
            if(detright >= 0.0) {
                return orientation(det);
            }
            else {
                detsum = -detleft - detright;
            }
        }
        else {
            return orientation(det);
        }
 
        double const errbound = DP_SAFE_EPSILON * detsum;
        if((det >= errbound) || (-det >= errbound)) {
            return orientation(det);
        }
        return CGAlgorithmsDD::FAILURE;
    };
 
    static int
    orientation(double x)
    {
        if(x < 0) {
            return CGAlgorithmsDD::RIGHT;
        }
        if(x > 0) {
            return CGAlgorithmsDD::LEFT;
        }
        return CGAlgorithmsDD::STRAIGHT;
    };
 
    static geom::Coordinate intersection(const geom::Coordinate& p1, const geom::Coordinate& p2,
                             const geom::Coordinate& q1, const geom::Coordinate& q2);
 
    static int signOfDet2x2(double dx1, double dy1, double dx2, double dy2);
 
    static DD detDD(double x1, double y1, double x2, double y2);
    static DD detDD(const DD& x1, const DD& y1, const DD& x2, const DD& y2);
 
    static geom::Coordinate circumcentreDD(const geom::Coordinate& a, const geom::Coordinate& b, const geom::Coordinate& c);
 
protected:
 
    static int signOfDet2x2(const DD& x1, const DD& y1, const DD& x2, const DD& y2);
 
};
 
} // namespace geos::algorithm
} // namespace geos