com.sun.tools.xjc.reader.gbind.Graph Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2022 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
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 {
private final Element source = new SourceNode();
private final Element sink = new SinkNode();
/**
* Strongly connected components of this graph.
*/
private final List ccs = new ArrayList<>();
/**
* Builds a from an {@link Expression} tree.
*
* {@link Expression} given to the graph will be modified forever,
* and it will not be able to create another .
*/
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 visited = new HashSet<>();
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.
*/
@Override
public Iterator iterator() {
return ccs.iterator();
}
@Override
public String toString() {
return ccs.toString();
}
}