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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: DTMChildIterNodeList.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.w3c.dom.Node;
     25 
     26 /**
     27  * <code>DTMNodeList</code> gives us an implementation of the DOM's
     28  * NodeList interface wrapped around a DTM Iterator. The author
     29  * considers this something of an abominations, since NodeList was not
     30  * intended to be a general purpose "list of nodes" API and is
     31  * generally considered by the DOM WG to have be a mistake... but I'm
     32  * told that some of the XPath/XSLT folks say they must have this
     33  * solution.
     34  *
     35  * Please note that this is not necessarily equivlaent to a DOM
     36  * NodeList operating over the same document. In particular:
     37  * <ul>
     38  *
     39  * <li>If there are several Text nodes in logical succession (ie,
     40  * across CDATASection and EntityReference boundaries), we will return
     41  * only the first; the caller is responsible for stepping through
     42  * them.
     43  * (%REVIEW% Provide a convenience routine here to assist, pending
     44  * proposed DOM Level 3 getAdjacentText() operation?) </li>
     45  *
     46  * <li>Since the whole XPath/XSLT architecture assumes that the source
     47  * document is not altered while we're working with it, we do not
     48  * promise to implement the DOM NodeList's "live view" response to
     49  * document mutation. </li>
     50  *
     51  * </ul>
     52  *
     53  * <p>State: In progress!!</p>
     54  * */
     55 public class DTMChildIterNodeList extends DTMNodeListBase {
     56     private int m_firstChild;
     57     private DTM m_parentDTM;
     58 
     59     //================================================================
     60     // Methods unique to this class
     61     private DTMChildIterNodeList() {
     62     }
     63 
     64     /**
     65      * Public constructor: Create a NodeList to support
     66      * DTMNodeProxy.getChildren().
     67      *
     68      * Unfortunately AxisIterators and DTMIterators don't share an API,
     69      * so I can't use the existing Axis.CHILD iterator. Rather than
     70      * create Yet Another Class, let's set up a special case of this
     71      * one.
     72      *
     73      * @param parentDTM The DTM containing this node
     74      * @param parentHandle DTM node-handle integer
     75      *
     76      */
     77     public DTMChildIterNodeList(DTM parentDTM,int parentHandle) {
     78         m_parentDTM=parentDTM;
     79         m_firstChild=parentDTM.getFirstChild(parentHandle);
     80     }
     81 
     82 
     83     //================================================================
     84     // org.w3c.dom.NodeList API follows
     85 
     86     /**
     87      * Returns the <code>index</code>th item in the collection. If
     88      * <code>index</code> is greater than or equal to the number of nodes in
     89      * the list, this returns <code>null</code>.
     90      * @param index Index into the collection.
     91      * @return The node at the <code>index</code>th position in the
     92      *   <code>NodeList</code>, or <code>null</code> if that is not a valid
     93      *   index.
     94      */
     95     public Node item(int index) {
     96         int handle=m_firstChild;
     97         while(--index>=0 && handle!=DTM.NULL) {
     98             handle=m_parentDTM.getNextSibling(handle);
     99         }
    100         if (handle == DTM.NULL) {
    101             return null;
    102         }
    103         return m_parentDTM.getNode(handle);
    104     }
    105 
    106     /**
    107      * The number of nodes in the list. The range of valid child node indices
    108      * is 0 to <code>length-1</code> inclusive.
    109      */
    110     public int getLength() {
    111         int count=0;
    112         for (int handle=m_firstChild;
    113              handle!=DTM.NULL;
    114              handle=m_parentDTM.getNextSibling(handle)) {
    115             ++count;
    116         }
    117         return count;
    118     }
    119 }
    120