001: /*
002: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
003: *
004: * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
005: *
006: * The contents of this file are subject to the terms of either the GNU
007: * General Public License Version 2 only ("GPL") or the Common Development
008: * and Distribution License("CDDL") (collectively, the "License"). You
009: * may not use this file except in compliance with the License. You can obtain
010: * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
011: * or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
012: * language governing permissions and limitations under the License.
013: *
014: * When distributing the software, include this License Header Notice in each
015: * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
016: * Sun designates this particular file as subject to the "Classpath" exception
017: * as provided by Sun in the GPL Version 2 section of the License file that
018: * accompanied this code. If applicable, add the following below the License
019: * Header, with the fields enclosed by brackets [] replaced by your own
020: * identifying information: "Portions Copyrighted [year]
021: * [name of copyright owner]"
022: *
023: * Contributor(s):
024: *
025: * If you wish your version of this file to be governed by only the CDDL or
026: * only the GPL Version 2, indicate your decision by adding "[Contributor]
027: * elects to include this software in this distribution under the [CDDL or GPL
028: * Version 2] license." If you don't indicate a single choice of license, a
029: * recipient has the option to distribute your version of this file under
030: * either the CDDL, the GPL Version 2 or to extend the choice of license to
031: * its licensees as provided above. However, if you add GPL Version 2 code
032: * and therefore, elected the GPL Version 2 license, then the option applies
033: * only if the new code is made subject to such option by the copyright
034: * holder.
035: */
036:
037: package com.sun.tools.xjc.reader.gbind;
038:
039: import java.util.ArrayList;
040: import java.util.HashSet;
041: import java.util.Iterator;
042: import java.util.List;
043: import java.util.Set;
044:
045: /**
046: * Graph of {@link Element}s.
047: *
048: * @author Kohsuke Kawaguchi
049: */
050: public final class Graph implements Iterable<ConnectedComponent> {
051: private final Element source = new SourceNode();
052: private final Element sink = new SinkNode();
053:
054: /**
055: * Strongly connected components of this graph.
056: */
057: private final List<ConnectedComponent> ccs = new ArrayList<ConnectedComponent>();
058:
059: /**
060: * Builds a {@link Graph} from an {@link Expression} tree.
061: *
062: * {@link Expression} given to the graph will be modified forever,
063: * and it will not be able to create another {@link Graph}.
064: */
065: public Graph(Expression body) {
066: // attach source and sink
067: Expression whole = new Sequence(new Sequence(source, body),
068: sink);
069:
070: // build up a graph
071: whole.buildDAG(ElementSet.EMPTY_SET);
072:
073: // decompose into strongly connected components.
074: // the algorithm is standard DFS-based algorithm,
075: // one illustration of this algorithm is available at
076: // http://www.personal.kent.edu/~rmuhamma/Algorithms/MyAlgorithms/GraphAlgor/strongComponent.htm
077: source.assignDfsPostOrder(sink);
078: source.buildStronglyConnectedComponents(ccs);
079:
080: // cut-set check
081: Set<Element> visited = new HashSet<Element>();
082: for (ConnectedComponent cc : ccs) {
083: visited.clear();
084: if (source.checkCutSet(cc, visited)) {
085: cc.isRequired = true;
086: }
087: }
088: }
089:
090: /**
091: * List up {@link ConnectedComponent}s of this graph in an order.
092: */
093: public Iterator<ConnectedComponent> iterator() {
094: return ccs.iterator();
095: }
096:
097: public String toString() {
098: return ccs.toString();
099: }
100: }
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