001    /*
002     *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003     *
004     *  This file is licensed to You under the Eclipse Public License (EPL);
005     *  You may not use this file except in compliance with the License. You
006     *  may obtain a copy of the License at
007     *
008     *      http://www.opensource.org/licenses/eclipse-1.0.php
009     *
010     *  See the COPYRIGHT.txt file distributed with this work for information
011     *  regarding copyright ownership.
012     */
013    package org.jikesrvm.compilers.opt.util;
014    
015    import java.util.Enumeration;
016    import java.util.NoSuchElementException;
017    
018    
019    public final class DepthFirstEnumerator implements Enumeration<GraphNode> {
020      Stack<GraphNode> stack;
021      int mark;
022    
023      public DepthFirstEnumerator(GraphNode start, int markNumber) {
024        stack = new Stack<GraphNode>();
025        stack.push(start);
026        mark = markNumber;
027      }
028    
029      public boolean hasMoreElements() {
030        if (stack == null) {
031          return false;
032        }
033    
034        for (GraphNode node : stack) {
035          if (node.getScratch() != mark) {
036            return true;
037          }
038        }
039        return false;
040      }
041    
042      public GraphNode nextElement() {
043        return next();
044      }
045    
046      public GraphNode next() {
047        if (stack == null) {
048          throw new NoSuchElementException("DepthFirstEnumerator");
049        }
050        while (!stack.isEmpty()) {
051          GraphNode node = stack.pop();
052          if (node.getScratch() != mark) {
053            for (Enumeration<GraphNode> e = node.outNodes(); e.hasMoreElements();) {
054              GraphNode n = e.nextElement();
055              if (n != null) {
056                stack.push(n);
057              }
058            }
059            node.setScratch(mark);
060            return node;
061          }
062        }
063        throw new NoSuchElementException("DepthFirstEnumerator");
064      }
065    }