code: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements. See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership. The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the  "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /*
   * $Id$
   */
  
  package org.apache.xalan.xsltc.dom;
  
  import org.apache.xalan.xsltc.DOM;
  import org.apache.xalan.xsltc.runtime.BasisLibrary;
  import org.apache.xml.dtm.DTMAxisIterator;
  import org.apache.xml.dtm.ref.DTMAxisIteratorBase;
  
  /**
   * UnionIterator takes a set of NodeIterators and produces
   * a merged NodeSet in document order with duplicates removed
   * The individual iterators are supposed to generate nodes
   * in document order
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   */
  public final class UnionIterator extends MultiValuedNodeHeapIterator {
      /** wrapper for NodeIterators to support iterator
  	comparison on the value of their next() method
      */
      final private DOM _dom;
  
      private final class LookAheadIterator
              extends MultiValuedNodeHeapIterator.HeapNode
      {
  	public DTMAxisIterator iterator;
  		
  	public LookAheadIterator(DTMAxisIterator iterator) {
              super();
  	    this.iterator = iterator;
  	}
  		
  	public int step() {
  	    _node = iterator.next();
  	    return _node;
  	}
  
  	public HeapNode cloneHeapNode() {
              LookAheadIterator clone = (LookAheadIterator) super.cloneHeapNode();
              clone.iterator = iterator.cloneIterator();
  	    return clone;
  	}
  
  	public void setMark() {
              super.setMark();
  	    iterator.setMark();
  	}
  
  	public void gotoMark() {
              super.gotoMark();
  	    iterator.gotoMark();
  	}
  
          public boolean isLessThan(HeapNode heapNode) {
              LookAheadIterator comparand = (LookAheadIterator) heapNode;
              return _dom.lessThan(_node, heapNode._node);
          }
  
          public HeapNode setStartNode(int node) {
              iterator.setStartNode(node);
              return this;
          }
  
          public HeapNode reset() {
              iterator.reset();
              return this;
          }
      } // end of LookAheadIterator
  
      public UnionIterator(DOM dom) {
  	_dom = dom;
      }
  
      public UnionIterator addIterator(DTMAxisIterator iterator) {
          addHeapNode(new LookAheadIterator(iterator));
          return this;
      }
  }
  