Class LastFoundQuadEdgeLocator

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.triangulate.quadedge;
14
15	import java.util.Collection;
16
17	/**
18	* Locates {@link QuadEdge}s in a {@link QuadEdgeSubdivision},
19	* optimizing the search by starting in the
20	* locality of the last edge found.
21	*
22	* @author Martin Davis
23	*/
24	public class LastFoundQuadEdgeLocator implements QuadEdgeLocator {
25	private QuadEdgeSubdivision subdiv;
26	private QuadEdge lastEdge = null;
27
28	public LastFoundQuadEdgeLocator(QuadEdgeSubdivision subdiv) {
29	this.subdiv = subdiv;
30	init();
31	}
32
33	private void init() {
34	lastEdge = findEdge();
35	}
36
37	private QuadEdge findEdge() {
38	Collection edges = subdiv.getEdges();
39	// assume there is an edge - otherwise will get an exception
40	return (QuadEdge) edges.iterator().next();
41	}
42
43	/**
44	* Locates an edge e, such that either v is on e, or e is an edge of a triangle containing v.
45	* The search starts from the last located edge and proceeds on the general direction of v.
46	*/
47	public QuadEdge locate(Vertex v) {
48	if (! lastEdge.isLive()) {
49	init();
50	}
51
52	QuadEdge e = subdiv.locateFromEdge(v, lastEdge);
53	lastEdge = e;
54	return e;
55	}
56	}
57