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package com.sun.tools.xjc.reader.gbind;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
/**
* Graph of {@link Element}s.
*
* @author Kohsuke Kawaguchi
*/
public final class Graph implements Iterable<ConnectedComponent> {
private final Element source = new SourceNode();
private final Element sink = new SinkNode();
/**
* Strongly connected components of this graph.
*/
private final List<ConnectedComponent> ccs = new ArrayList<ConnectedComponent>();
/**
* Builds a {@link Graph} from an {@link Expression} tree.
*
* {@link Expression} given to the graph will be modified forever,
* and it will not be able to create another {@link Graph}.
*/
public Graph(Expression body) {
// attach source and sink
Expression whole = new Sequence(new Sequence(source,body),sink);
// build up a graph
whole.buildDAG(ElementSet.EMPTY_SET);
// decompose into strongly connected components.
// the algorithm is standard DFS-based algorithm,
// one illustration of this algorithm is available at
// http://www.personal.kent.edu/~rmuhamma/Algorithms/MyAlgorithms/GraphAlgor/strongComponent.htm
source.assignDfsPostOrder(sink);
source.buildStronglyConnectedComponents(ccs);
// cut-set check
Set<Element> visited = new HashSet<Element>();
for (ConnectedComponent cc : ccs) {
visited.clear();
if(source.checkCutSet(cc,visited)) {
cc.isRequired = true;
}
}
}
/**
* List up {@link ConnectedComponent}s of this graph in an order.
*/
public Iterator<ConnectedComponent> iterator() {
return ccs.iterator();
}
public String toString() {
return ccs.toString();
}
}