EdgeConnectedTriangleTraversal.java

/*
 * The JTS Topology Suite is a collection of Java classes that
 * implement the fundamental operations required to validate a given
 * geo-spatial data set to a known topological specification.
 *
 * Copyright (C) 2001 Vivid Solutions
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * For more information, contact:
 *
 *     Vivid Solutions
 *     Suite #1A
 *     2328 Government Street
 *     Victoria BC  V8T 5G5
 *     Canada
 *
 *     (250)385-6040
 *     www.vividsolutions.com
 */

package com.vividsolutions.jts.triangulate.quadedge;

import java.util.Collection;
import java.util.LinkedList;

/**
 * A framework to visit sets of edge-connected {@link QuadEdgeTriangle}s in breadth-first order
 * 
 * @author Martin Davis
 * @version 1.0
 */
public class EdgeConnectedTriangleTraversal {
    private LinkedList triQueue = new LinkedList();

    public EdgeConnectedTriangleTraversal() {}

    public void init(QuadEdgeTriangle tri) {
        triQueue.addLast(tri);
    }

    /**
     * Called to initialize the traversal queue with a given set of {@link QuadEdgeTriangle}s
     * 
     * @param tris a collection of QuadEdgeTriangle
     */
    public void init(Collection tris) {
        triQueue.addAll(tris);
    }

    /**
     * Subclasses can call this method to add a triangle to the end of the queue. This is useful for
     * initializing the queue to a chosen set of triangles.
     * 
     * @param tri a triangle
     */
    /*
     * protected void addLast(QuadEdgeTriangle tri) { triQueue.addLast(tri); }
     */

    /**
     * Subclasses call this method to perform the visiting process.
     */
    public void visitAll(TraversalVisitor visitor) {
        while (!triQueue.isEmpty()) {
            QuadEdgeTriangle tri = (QuadEdgeTriangle) triQueue.removeFirst();
            process(tri, visitor);
        }
    }

    private void process(QuadEdgeTriangle currTri, TraversalVisitor visitor) {
        currTri.getNeighbours();
        for (int i = 0; i < 3; i++) {
            QuadEdgeTriangle neighTri = (QuadEdgeTriangle) currTri.getEdge(i).sym().getData();
            if (neighTri == null)
                continue;
            if (visitor.visit(currTri, i, neighTri))
                triQueue.addLast(neighTri);
        }
    }

}