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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: DTMNodeList.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.DTMIterator;
     25 import org.w3c.dom.Node;
     26 
     27 /**
     28  * <code>DTMNodeList</code> gives us an implementation of the DOM's
     29  * NodeList interface wrapped around a DTM Iterator. The author
     30  * considers this something of an abominations, since NodeList was not
     31  * intended to be a general purpose "list of nodes" API and is
     32  * generally considered by the DOM WG to have be a mistake... but I'm
     33  * told that some of the XPath/XSLT folks say they must have this
     34  * solution.
     35  *
     36  * Please note that this is not necessarily equivlaent to a DOM
     37  * NodeList operating over the same document. In particular:
     38  * <ul>
     39  *
     40  * <li>If there are several Text nodes in logical succession (ie,
     41  * across CDATASection and EntityReference boundaries), we will return
     42  * only the first; the caller is responsible for stepping through
     43  * them.
     44  * (%REVIEW% Provide a convenience routine here to assist, pending
     45  * proposed DOM Level 3 getAdjacentText() operation?) </li>
     46  *
     47  * <li>Since the whole XPath/XSLT architecture assumes that the source
     48  * document is not altered while we're working with it, we do not
     49  * promise to implement the DOM NodeList's "live view" response to
     50  * document mutation. </li>
     51  *
     52  * </ul>
     53  *
     54  * <p>State: In progress!!</p>
     55  * */
     56 public class DTMNodeList extends DTMNodeListBase {
     57     private DTMIterator m_iter;
     58 
     59     //================================================================
     60     // Methods unique to this class
     61     private DTMNodeList() {
     62     }
     63 
     64     /**
     65      * Public constructor: Wrap a DTMNodeList around an existing
     66      * and preconfigured DTMIterator
     67      *
     68      * WARNING: THIS HAS THE SIDE EFFECT OF ISSUING setShouldCacheNodes(true)
     69      * AGAINST THE DTMIterator.
     70      *
     71      */
     72     public DTMNodeList(DTMIterator dtmIterator) {
     73         if (dtmIterator != null) {
     74             int pos = dtmIterator.getCurrentPos();
     75             try {
     76                 m_iter=(DTMIterator)dtmIterator.cloneWithReset();
     77             } catch(CloneNotSupportedException cnse) {
     78                 m_iter = dtmIterator;
     79             }
     80             m_iter.setShouldCacheNodes(true);
     81             m_iter.runTo(-1);
     82             m_iter.setCurrentPos(pos);
     83         }
     84     }
     85 
     86     /**
     87      * Access the wrapped DTMIterator. I'm not sure whether anyone will
     88      * need this or not, but let's write it and think about it.
     89      *
     90      */
     91     public DTMIterator getDTMIterator() {
     92         return m_iter;
     93     }
     94 
     95     //================================================================
     96     // org.w3c.dom.NodeList API follows
     97 
     98     /**
     99      * Returns the <code>index</code>th item in the collection. If
    100      * <code>index</code> is greater than or equal to the number of nodes in
    101      * the list, this returns <code>null</code>.
    102      * @param index Index into the collection.
    103      * @return The node at the <code>index</code>th position in the
    104      *   <code>NodeList</code>, or <code>null</code> if that is not a valid
    105      *   index.
    106      */
    107     public Node item(int index)
    108     {
    109         if (m_iter != null) {
    110             int handle=m_iter.item(index);
    111             if (handle == DTM.NULL) {
    112                 return null;
    113             }
    114             return m_iter.getDTM(handle).getNode(handle);
    115         } else {
    116             return null;
    117         }
    118     }
    119 
    120     /**
    121      * The number of nodes in the list. The range of valid child node indices
    122      * is 0 to <code>length-1</code> inclusive.
    123      */
    124     public int getLength() {
    125         return (m_iter != null) ? m_iter.getLength() : 0;
    126     }
    127 }
    128