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 */
21package org.apache.xml.dtm.ref;
22
23import org.apache.xml.dtm.DTM;
24import org.apache.xml.dtm.DTMAxisIterator;
25import org.apache.xml.utils.IntVector;
26
27import 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 * */
58public 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