/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
*
* 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;
* version 2.1 of the License.
*
* 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.
*/
package org.geotools.graph.traverse.standard;
import java.util.Iterator;
import org.geotools.graph.structure.Graph;
import org.geotools.graph.structure.Graphable;
import org.geotools.graph.structure.Node;
import org.geotools.graph.traverse.GraphIterator;
import org.geotools.graph.traverse.GraphTraversal;
import org.geotools.graph.traverse.basic.SourceGraphIterator;
/**
* Iterates over the nodes of a graph starting from a specified node, stopping
* at a bifurcation. A <B>bifurcation</B> is defined as a node of degree > 2.
* The following figures illustrate examples of the iterator.<BR>
* <BR>
* <IMG src="doc-files/nobif_0.gif"/><BR>
* <BR>
* <BR>
* <BR>
* <IMG src="doc-files/nobif_1.gif"/><BR>
* <BR>
*
* @author Justin Deoliveira, Refractions Research Inc, jdeolive@refractions.net
*
*
* @source $URL$
*/
public class NoBifurcationIterator extends SourceGraphIterator {
/** the next node to be returned by the iterator **/
private Node m_next;
/**
* Does nothing.
*
* @see GraphIterator#init(Graph)
*/
public void init(Graph graph, GraphTraversal traversal) {
//do nothing
}
/**
* Sets the source of the traversal. This must be a node of degree less than
* or equal to 2.
*
* @param source node of degree less than or equal 2
*
* @see SourceGraphIterator#setSource(Graphable)
* @throws IllegalStateException
*/
public void setSource(Graphable source) {
//check that source node if of degree <= 2
if (((Node)source).getDegree() > 2) {
throw new IllegalStateException(
"Cannot start a no bifurcation traversal on a node that " +
"bifurcates."
);
}
super.setSource(source);
m_next = (Node)getSource();
}
/**
* The next node in the iteration is the first node found adjacent to the
* current node that is non visited and of degree less than 2.
*
* @see org.geotools.graph.traverse.GraphIterator#next()
*/
public Graphable next(GraphTraversal traversal) {
return(m_next);
}
/**
* Searches for the next node to be returned in the iteration. The next node
* is the first node (of two) related to the current node that is non visited
* and of degree <= 2.
*
* @see org.geotools.graph.traverse.GraphIterator#cont(Graphable)
*/
public void cont(Graphable current, GraphTraversal traversal) {
//find a related node that is non visited and degree <= 2
Iterator itr = current.getRelated();
m_next = (Node)itr.next();
if (itr.hasNext() && (traversal.isVisited(m_next) || m_next.getDegree() > 2))
m_next = (Node)itr.next();
if (traversal.isVisited(m_next) || m_next.getDegree() > 2) m_next = null;
}
/**
* Kills the current branch of the iteration by explicitly setting the next
* node to be returned to null. This call always ends the traversal.
*
* @see org.geotools.graph.traverse.GraphIterator#killBranch(Graphable)
*/
public void killBranch(Graphable current, GraphTraversal traversal) {
m_next = null;
}
}