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      1 /*
      2  * Licensed to the Apache Software Foundation (ASF) under one
      3  * or more contributor license agreements. See the NOTICE file
      4  * distributed with this work for additional information
      5  * regarding copyright ownership. The ASF licenses this file
      6  * to you under the Apache License, Version 2.0 (the  "License");
      7  * you may not use this file except in compliance with the License.
      8  * You may obtain a copy of the License at
      9  *
     10  *     http://www.apache.org/licenses/LICENSE-2.0
     11  *
     12  * Unless required by applicable law or agreed to in writing, software
     13  * distributed under the License is distributed on an "AS IS" BASIS,
     14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15  * See the License for the specific language governing permissions and
     16  * limitations under the License.
     17  */
     18 /*
     19  * $Id: DTMAxisIterNodeList.java 468653 2006-10-28 07:07:05Z minchau $
     20  */
     21 package org.apache.xml.dtm.ref;
     22 
     23 import org.apache.xml.dtm.DTM;
     24 import org.apache.xml.dtm.DTMAxisIterator;
     25 import org.apache.xml.utils.IntVector;
     26 
     27 import org.w3c.dom.Node;
     28 
     29 /**
     30  * <code>DTMAxisNodeList</code> gives us an implementation of the DOM's
     31  * NodeList interface wrapped around a DTM Iterator. The author
     32  * considers this something of an abominations, since NodeList was not
     33  * intended to be a general purpose "list of nodes" API and is
     34  * generally considered by the DOM WG to have be a mistake... but I'm
     35  * told that some of the XPath/XSLT folks say they must have this
     36  * solution.
     37  *
     38  * Please note that this is not necessarily equivlaent to a DOM
     39  * NodeList operating over the same document. In particular:
     40  * <ul>
     41  *
     42  * <li>If there are several Text nodes in logical succession (ie,
     43  * across CDATASection and EntityReference boundaries), we will return
     44  * only the first; the caller is responsible for stepping through
     45  * them.
     46  * (%REVIEW% Provide a convenience routine here to assist, pending
     47  * proposed DOM Level 3 getAdjacentText() operation?) </li>
     48  *
     49  * <li>Since the whole XPath/XSLT architecture assumes that the source
     50  * document is not altered while we're working with it, we do not
     51  * promise to implement the DOM NodeList's "live view" response to
     52  * document mutation. </li>
     53  *
     54  * </ul>
     55  *
     56  * <p>State: In progress!!</p>
     57  * */
     58 public class DTMAxisIterNodeList extends DTMNodeListBase {
     59     private DTM m_dtm;
     60     private DTMAxisIterator m_iter;
     61     private IntVector m_cachedNodes;
     62     private int m_last = -1;
     63     //================================================================
     64     // Methods unique to this class
     65     private DTMAxisIterNodeList() {
     66     }
     67 
     68     /**
     69      * Public constructor: Wrap a DTMNodeList around an existing
     70      * and preconfigured DTMAxisIterator
     71      */
     72     public DTMAxisIterNodeList(DTM dtm, DTMAxisIterator dtmAxisIterator) {
     73         if (dtmAxisIterator == null) {
     74             m_last = 0;
     75         } else {
     76             m_cachedNodes = new IntVector();
     77             m_dtm = dtm;
     78         }
     79         m_iter = dtmAxisIterator;
     80     }
     81 
     82     /**
     83      * Access the wrapped DTMIterator. I'm not sure whether anyone will
     84      * need this or not, but let's write it and think about it.
     85      *
     86      */
     87     public DTMAxisIterator getDTMAxisIterator() {
     88         return m_iter;
     89     }
     90 
     91 
     92     //================================================================
     93     // org.w3c.dom.NodeList API follows
     94 
     95     /**
     96      * Returns the <code>index</code>th item in the collection. If
     97      * <code>index</code> is greater than or equal to the number of nodes in
     98      * the list, this returns <code>null</code>.
     99      * @param index Index into the collection.
    100      * @return The node at the <code>index</code>th position in the
    101      *   <code>NodeList</code>, or <code>null</code> if that is not a valid
    102      *   index.
    103      */
    104     public Node item(int index) {
    105         if (m_iter != null) {
    106             int node;
    107             int count = m_cachedNodes.size();
    108 
    109             if (count > index) {
    110                 node = m_cachedNodes.elementAt(index);
    111                 return m_dtm.getNode(node);
    112             } else if (m_last == -1) {
    113                 while (((node = m_iter.next()) != DTMAxisIterator.END)
    114                            && count <= index) {
    115                     m_cachedNodes.addElement(node);
    116                     count++;
    117                 }
    118                 if (node == DTMAxisIterator.END) {
    119                     m_last = count;
    120                 } else {
    121                     return m_dtm.getNode(node);
    122                 }
    123             }
    124         }
    125         return null;
    126     }
    127 
    128     /**
    129      * The number of nodes in the list. The range of valid child node indices
    130      * is 0 to <code>length-1</code> inclusive.
    131      */
    132     public int getLength() {
    133         if (m_last == -1) {
    134             int node;
    135             while ((node = m_iter.next()) != DTMAxisIterator.END) {
    136                 m_cachedNodes.addElement(node);
    137             }
    138             m_last = m_cachedNodes.size();
    139         }
    140         return m_last;
    141     }
    142 }
    143