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Java > Open Source Codes > org > apache > commons > jxpath > ri > model > jdom > JDOMNodeIterator


1 /*
2  * Copyright 1999-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.jxpath.ri.model.jdom;
17
18 import java.util.Collections JavaDoc;
19 import java.util.List JavaDoc;
20
21 import org.apache.commons.jxpath.ri.compiler.NodeTest;
22 import org.apache.commons.jxpath.ri.model.NodeIterator;
23 import org.apache.commons.jxpath.ri.model.NodePointer;
24 import org.jdom.Document;
25 import org.jdom.Element;
26
27 /**
28  * An iterator of children of a JDOM Node.
29  *
30  * @author Dmitri Plotnikov
31  * @version $Revision: 1.6 $ $Date: 2004/02/29 14:17:40 $
32  */
33 public class JDOMNodeIterator implements NodeIterator {
34     private NodePointer parent;
35     private NodeTest nodeTest;
36
37     private boolean reverse;
38     private int position = 0;
39     private int index = 0;
40     private List JavaDoc children;
41     private Object JavaDoc child;
42
43     public JDOMNodeIterator(
44             NodePointer parent, NodeTest nodeTest,
45             boolean reverse, NodePointer startWith)
46     {
47         this.parent = parent;
48         if (startWith != null) {
49             this.child = startWith.getNode();
50         }
51         // TBD: optimize me for different node tests
52 Object JavaDoc node = parent.getNode();
53         if (node instanceof Document) {
54             this.children = ((Document) node).getContent();
55         }
56         else if (node instanceof Element) {
57             this.children = ((Element) node).getContent();
58         }
59         else {
60             this.children = Collections.EMPTY_LIST;
61         }
62         this.nodeTest = nodeTest;
63         this.reverse = reverse;
64     }
65
66     public NodePointer getNodePointer() {
67         if (child == null) {
68             if (!setPosition(1)) {
69                 return null;
70             }
71             position = 0;
72         }
73
74         return new JDOMNodePointer(parent, child);
75     }
76
77     public int getPosition() {
78         return position;
79     }
80
81     public boolean setPosition(int position) {
82         while (this.position < position) {
83             if (!next()) {
84                 return false;
85             }
86         }
87         while (this.position > position) {
88             if (!previous()) {
89                 return false;
90             }
91         }
92         return true;
93     }
94
95     /**
96      * This is actually never invoked during the normal evaluation
97      * of xpaths - an iterator is always going forward, never backwards.
98      * So, this is implemented only for completeness and perhaps for
99      * those who use these iterators outside of XPath evaluation.
100      */
101     private boolean previous() {
102         position--;
103         if (!reverse) {
104             while (--index >= 0) {
105                 child = children.get(index);
106                 if (testChild()) {
107                     return true;
108                 }
109             }
110         }
111         else {
112             for (; index < children.size(); index++) {
113                 child = children.get(index);
114                 if (testChild()) {
115                     return true;
116                 }
117             }
118         }
119         return false;
120     }
121
122     private boolean next() {
123         position++;
124         if (!reverse) {
125             if (position == 1) {
126                 index = 0;
127                 if (child != null) {
128                     index = children.indexOf(child) + 1;
129                 }
130             }
131             else {
132                 index++;
133             }
134             for (; index < children.size(); index++) {
135                 child = children.get(index);
136                 if (testChild()) {
137                     return true;
138                 }
139             }
140             return false;
141         }
142         else {
143             if (position == 1) {
144                 index = children.size() - 1;
145                 if (child != null) {
146                     index = children.indexOf(child) - 1;
147                 }
148             }
149             else {
150                 index--;
151             }
152             for (; index >= 0; index--) {
153                 child = children.get(index);
154                 if (testChild()) {
155                     return true;
156                 }
157             }
158             return false;
159         }
160     }
161
162     private boolean testChild() {
163         return JDOMNodePointer.testNode(parent, child, nodeTest);
164     }
165 }
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