121 lines
3.0 KiB
C
121 lines
3.0 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) 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: noding/SegmentPointComparator.java r320 (JTS-1.12)
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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 <geos/geom/Coordinate.h>
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#include <cassert>
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namespace geos {
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namespace noding { // geos.noding
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/** \brief
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* Implements a robust method of comparing the relative position of two
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* points along the same segment.
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*
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* The coordinates are assumed to lie "near" the segment.
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* This means that this algorithm will only return correct results
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* if the input coordinates
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* have the same precision and correspond to rounded values
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* of exact coordinates lying on the segment.
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*
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*/
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class GEOS_DLL SegmentPointComparator {
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public:
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/** \brief
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* Compares two Coordinates for their relative position along a
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* segment lying in the specified Octant.
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*
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* @return -1 node0 occurs first
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* @return 0 the two nodes are equal
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* @return 1 node1 occurs first
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*/
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static int
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compare(int octant, const geom::Coordinate& p0,
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const geom::Coordinate& p1)
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{
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// nodes can only be equal if their coordinates are equal
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if(p0.equals2D(p1)) {
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return 0;
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}
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int xSign = relativeSign(p0.x, p1.x);
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int ySign = relativeSign(p0.y, p1.y);
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switch(octant) {
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case 0:
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return compareValue(xSign, ySign);
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case 1:
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return compareValue(ySign, xSign);
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case 2:
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return compareValue(ySign, -xSign);
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case 3:
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return compareValue(-xSign, ySign);
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case 4:
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return compareValue(-xSign, -ySign);
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case 5:
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return compareValue(-ySign, -xSign);
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case 6:
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return compareValue(-ySign, xSign);
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case 7:
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return compareValue(xSign, -ySign);
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}
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assert(0); // invalid octant value
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return 0;
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}
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static int
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relativeSign(double x0, double x1)
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{
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if(x0 < x1) {
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return -1;
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}
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if(x0 > x1) {
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return 1;
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}
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return 0;
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}
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static int
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compareValue(int compareSign0, int compareSign1)
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{
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if(compareSign0 < 0) {
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return -1;
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}
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if(compareSign0 > 0) {
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return 1;
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}
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if(compareSign1 < 0) {
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return -1;
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}
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if(compareSign1 > 0) {
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return 1;
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}
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return 0;
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}
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};
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} // namespace geos.noding
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} // namespace geos
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