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# SegmentPointComparator.h

    00001 /**********************************************************************
    00002  *
    00003  * GEOS - Geometry Engine Open Source
    00004  * http://geos.refractions.net
    00005  *
    00006  * Copyright (C) 2006      Refractions Research Inc.
    00007  *
    00008  * This is free software; you can redistribute and/or modify it under
    00009  * the terms of the GNU Lesser General Public Licence as published
    00010  * by the Free Software Foundation.
    00011  * See the COPYING file for more information.
    00012  *
    00013  **********************************************************************
    00014  *
    00015  *  Last port: noding/SegmentPointComparator.java r320 (JTS-1.12)
    00016  *
    00017  **********************************************************************/
    00018
    00019 #ifndef GEOS_NODING_SEGMENTPOINTCOMPARATOR_H
    00020 #define GEOS_NODING_SEGMENTPOINTCOMPARATOR_H
    00021
    00022 #include <geos/export.h>
    00023 #include <geos/geom/Coordinate.h>
    00024 #include <cassert>
    00025
    00026 namespace geos {
    00027 namespace noding { // geos.noding
    00028
    00039 class GEOS_DLL SegmentPointComparator {
    00040
    00041 public:
    00042
    00051         static int compare(int octant, const geom::Coordinate& p0,
    00052                         const geom::Coordinate& p1)
    00053         {
    00054                 // nodes can only be equal if their coordinates are equal
    00055                 if (p0.equals2D(p1)) return 0;
    00056
    00057                 int xSign = relativeSign(p0.x, p1.x);
    00058                 int ySign = relativeSign(p0.y, p1.y);
    00059
    00060                 switch (octant) {
    00061                         case 0: return compareValue(xSign, ySign);
    00062                         case 1: return compareValue(ySign, xSign);
    00063                         case 2: return compareValue(ySign, -xSign);
    00064                         case 3: return compareValue(-xSign, ySign);
    00065                         case 4: return compareValue(-xSign, -ySign);
    00066                         case 5: return compareValue(-ySign, -xSign);
    00067                         case 6: return compareValue(-ySign, xSign);
    00068                         case 7: return compareValue(xSign, -ySign);
    00069                 }
    00070                 assert(0); // invalid octant value
    00071                 return 0;
    00072
    00073         }
    00074
    00075         static int relativeSign(double x0, double x1)
    00076         {
    00077                 if (x0 < x1) return -1;
    00078                 if (x0 > x1) return 1;
    00079                 return 0;
    00080         }
    00081
    00082         static int compareValue(int compareSign0, int compareSign1)
    00083         {
    00084                 if (compareSign0 < 0) return -1;
    00085                 if (compareSign0 > 0) return 1;
    00086                 if (compareSign1 < 0) return -1;
    00087                 if (compareSign1 > 0) return 1;
    00088                 return 0;
    00089         }
    00090
    00091 };
    00092
    00093 } // namespace geos.noding
    00094 } // namespace geos
    00095
    00096 #endif // GEOS_NODING_SEGMENTPOINTCOMPARATOR_H