content: /*
   * NodeExtractor.java January 2010
   *
   * Copyright (C) 2010, Niall Gallagher <niallg@users.sf.net>
   *
   * Licensed 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
   * 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.
   */
  
  package com.aliyun.odps.simpleframework.xml.stream;
  
  import static org.w3c.dom.Node.COMMENT_NODE;
  
  import java.util.LinkedList;
  
  import org.w3c.dom.Document;
  import org.w3c.dom.Node;
  import org.w3c.dom.NodeList;
  
  /**
   * The <code>NodeExtractor</code> object is used to extract nodes 
   * from a provided DOM document. This is used so that the nodes of
   * a given document can be read with queue like semantics, such 
   * that the first node encountered is the first node taken from 
   * the queue. Queue semantics help transform DOM documents to an
   * event stream much like the StAX framework.
   *  
   * @author Niall Gallagher
   */
  class NodeExtractor extends LinkedList<Node> {
  
     /**
      * Constructor for the <code>NodeExtractor</code> object. This
      * is used to instantiate an object that flattens a document
      * in to a queue so that the nodes can be used for streaming.
      * 
      * @param source this is the source document to be flattened
      */
     public NodeExtractor(Document source) {
        this.extract(source);
     }
     
     /**
      * This is used to extract the nodes of the document in such a
      * way that it can be navigated as a queue. In order to do this
      * each node encountered is pushed in to the queue so that
      * when finished the nodes can be dealt with as a stream.
      * 
      * @param source this is the source document to be flattened
      */
     private void extract(Document source) {
        Node node = source.getDocumentElement();
        
        if(node != null) {
           offer(node);
           extract(node);
        }
     }
  
     /**
      * This is used to extract the nodes of the element in such a
      * way that it can be navigated as a queue. In order to do this
      * each node encountered is pushed in to the queue so that
      * when finished the nodes can be dealt with as a stream.
      * 
      * @param source this is the source element to be flattened
      */
     private void extract(Node source) {
        NodeList list = source.getChildNodes();
        int length = list.getLength();
        
        for(int i = 0; i < length; i++) {
           Node node = list.item(i);
           short type = node.getNodeType();
           
           if(type != COMMENT_NODE) {
              offer(node);
              extract(node);
           }
        }
     }
  }