Class SegmentPointComparator

1	/*
2	* Copyright (c) 2016 Vivid Solutions.
3	*
4	* All rights reserved. This program and the accompanying materials
5	* are made available under the terms of the Eclipse Public License 2.0
6	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
7	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
8	* and the Eclipse Distribution License is available at
9	*
10	* http://www.eclipse.org/org/documents/edl-v10.php.
11	*/
12
13	package org.locationtech.jts.noding;
14
15	import org.locationtech.jts.geom.Coordinate;
16	import org.locationtech.jts.util.Assert;
17
18	/**
19	* Implements a robust method of comparing the relative position of two
20	* points along the same segment.
21	* The coordinates are assumed to lie "near" the segment.
22	* This means that this algorithm will only return correct results
23	* if the input coordinates
24	* have the same precision and correspond to rounded values
25	* of exact coordinates lying on the segment.
26	*
27	* @version 1.7
28	*/
29	public class SegmentPointComparator {
30
31	/**
32	* Compares two {@link Coordinate}s for their relative position along a segment
33	* lying in the specified {@link Octant}.
34	*
35	* @return -1 node0 occurs first;
36	* 0 the two nodes are equal;
37	* 1 node1 occurs first
38	*/
39	public static int compare(int octant, Coordinate p0, Coordinate p1)
40	{
41	// nodes can only be equal if their coordinates are equal
42	if (p0.equals2D(p1)) return 0;
43
44	int xSign = relativeSign(p0.x, p1.x);
45	int ySign = relativeSign(p0.y, p1.y);
46
47	switch (octant) {
48	case 0: return compareValue(xSign, ySign);
49	case 1: return compareValue(ySign, xSign);
50	case 2: return compareValue(ySign, -xSign);
51	case 3: return compareValue(-xSign, ySign);
52	case 4: return compareValue(-xSign, -ySign);
53	case 5: return compareValue(-ySign, -xSign);
54	case 6: return compareValue(-ySign, xSign);
55	case 7: return compareValue(xSign, -ySign);
56	}
57	Assert.shouldNeverReachHere("invalid octant value");
58	return 0;
59	}
60
61	public static int relativeSign(double x0, double x1)
62	{
63	if (x0 < x1) return -1;
64	if (x0 > x1) return 1;
65	return 0;
66	}
67
68	private static int compareValue(int compareSign0, int compareSign1)
69	{
70	if (compareSign0 < 0) return -1;
71	if (compareSign0 > 0) return 1;
72	if (compareSign1 < 0) return -1;
73	if (compareSign1 > 0) return 1;
74	return 0;
75
76	}
77	}
78