/*
* 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.basic;
import org.geotools.graph.structure.Graph;
import org.geotools.graph.structure.GraphVisitor;
import org.geotools.graph.structure.Graphable;
import org.geotools.graph.traverse.GraphIterator;
import org.geotools.graph.traverse.GraphTraversal;
import org.geotools.graph.traverse.GraphWalker;
/**
* A basic implementation of GraphTraversal.
*
* @author Justin Deoliveira, Refractions Research Inc, jdeolive@refractions.net
*
*
*
* @source $URL$
*/
public class BasicGraphTraversal implements GraphTraversal {
/** the graph being iterated over **/
private Graph m_graph;
/** the walker being iterated over the graph **/
private GraphWalker m_walker;
/** the iterator specifying the order in which to visit components of
the graph during the traversal **/
private GraphIterator m_iterator;
/**
* Constructs a new graph traversal.
*
* @param graph The graph being traversed.
* @param walker The walker being traversed over the components of the graph.
* @param iterator The iterator specifying the order in which to visit
* components of the graph.
*/
public BasicGraphTraversal(
Graph graph, GraphWalker walker, GraphIterator iterator
) {
m_graph = graph;
m_walker = walker;
setIterator(iterator);
}
/**
* @see GraphTraversal#setGraph(Graph)
*/
public void setGraph(Graph graph) {
m_graph = graph;
}
/**
* @see GraphTraversal#getGraph()
*/
public Graph getGraph() {
return(m_graph);
}
/**
* Sets the iterator and intializes it.
*
* @see GraphIterator#init(Graph)
* @see GraphTraversal#setIterator(GraphIterator)
*/
public void setIterator(GraphIterator iterator) {
m_iterator = iterator;
m_iterator.setTraversal(this);
m_iterator.init(m_graph, this);
}
/**
* @see GraphTraversal#getIterator()
*/
public GraphIterator getIterator() {
return(m_iterator);
}
/**
* @see GraphTraversal#setWalker(GraphWalker)
*/
public void setWalker(GraphWalker walker) {
m_walker = walker;
}
/**
* @see GraphTraversal#getWalker()
*/
public GraphWalker getWalker() {
return(m_walker);
}
/**
* Resets the visited flag and counts of all nodes of the graph.
*
* @see GraphTraversal#init()
*/
public void init() {
//initialize the nodes of the graph
m_graph.visitNodes(
new GraphVisitor() {
public int visit(Graphable component) {
component.setVisited(false);
component.setCount(0);
return(0);
}
}
);
}
/**
* Upon each iteration of the traversal, a component is returned from the
* iterator and passed to the visitor. The traversal interprets the return
* codes from the walker and performs the following actions. <BR>
* <BR>
* <TABLE border="1" width="60%" style="font-family:Arial;font-size=10pt">
* <TH width="20%">Code</TH>
* <TH width="40%">Action Performed</TH>
* <TR>
* <TD align="center">CONTINUE</TD>
* <TD>The traversal instructs the iterator to continue and starts the
* next stage of iteration.</TD>
* </TR>
* <TR>
* <TD align="center">SUSPEND</TD>
* <TD>The traversal instructs the iterator to continue but does not start
* the next stage of iteration, returning from traverse().</TD>
* </TR>
* <TR>
* <TD align="center">KILL_BRANCH</TD>
* <TD>The traversal instructs the iterator to kill the current branch
* and starts the next stage of iteration.</TD>
* </TR>
* <TR>
* <TD align="center">STOP</TD>
* <TD>The traversal does not instruct the iterator to continue and
* does not start the next of iteration, returning from traverse()
* </TD>
* </TR>
* </TABLE>
*
* @see GraphTraversal#traverse()
*/
public void traverse() {
Graphable current;
//get next component from iterator, null means stop
O: while((current = m_iterator.next(this)) != null) {
setVisited(current, true);
//pass the component to the visitor
switch(m_walker.visit(current, null)) {
case CONTINUE:
//signal iterator to continue from this point and start next
// iteration of traversal
m_iterator.cont(current,this);
continue;
case SUSPEND:
//signal iterator to continue from this point, but do not start
// next iteration
m_iterator.cont(current,this);
return;
case KILL_BRANCH:
//signal iterator to kill branch at this point and start next
//iteration
m_iterator.killBranch(current,this);
continue;
case STOP:
//stop traversal
break O;
default:
//illegal return value from walker
throw new IllegalStateException(
"Unrecognized return value from GraphWalker"
);
}
}
//traversal complete, signal to walker
m_walker.finish();
}
public void setVisited(Graphable g, boolean visited) {
g.setVisited(visited);
}
public boolean isVisited(Graphable g) {
return(g.isVisited());
}
}