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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.configuration.tree.xpath;
18  
19  import java.util.List;
20  
21  import org.apache.commons.configuration.tree.ConfigurationNode;
22  import org.apache.commons.jxpath.ri.model.NodeIterator;
23  import org.apache.commons.jxpath.ri.model.NodePointer;
24  
25  /***
26   * <p>
27   * A base class for implementing iterators over configuration nodes.
28   * </p>
29   * <p>
30   * This class already provides common functionality for implementing the
31   * iteration process. Derived classes will implement specific behavior based on
32   * the concrete node type (child node or attribute node).
33   * </p>
34   *
35   * @since 1.3
36   * @author Oliver Heger
37   * @version $Id: ConfigurationNodeIteratorBase.java 439648 2006-09-02 20:42:10Z oheger $
38   */
39  abstract class ConfigurationNodeIteratorBase implements NodeIterator
40  {
41      /*** Stores the parent node pointer. */
42      private NodePointer parent;
43  
44      /*** Stores the list with the sub nodes. */
45      private List subNodes;
46  
47      /*** Stores the current position. */
48      private int position;
49  
50      /*** Stores the start offset of the iterator. */
51      private int startOffset;
52  
53      /*** Stores the reverse flag. */
54      private boolean reverse;
55  
56      /***
57       * Creates a new instance of <code>ConfigurationNodeIteratorBase</code>
58       * and initializes it.
59       *
60       * @param parent the parent pointer
61       * @param reverse the reverse flag
62       */
63      protected ConfigurationNodeIteratorBase(NodePointer parent, boolean reverse)
64      {
65          this.parent = parent;
66          this.reverse = reverse;
67      }
68  
69      /***
70       * Returns the position of the iteration.
71       *
72       * @return the position
73       */
74      public int getPosition()
75      {
76          return position;
77      }
78  
79      /***
80       * Sets the position of the iteration.
81       *
82       * @param pos the new position
83       * @return a flag if this is a valid position
84       */
85      public boolean setPosition(int pos)
86      {
87          position = pos;
88          return pos >= 1 && pos <= getMaxPosition();
89      }
90  
91      /***
92       * Returns the current node pointer.
93       *
94       * @return the current pointer in this iteration
95       */
96      public NodePointer getNodePointer()
97      {
98          if (getPosition() < 1 && !setPosition(1))
99          {
100             return null;
101         }
102 
103         return createNodePointer((ConfigurationNode) subNodes
104                 .get(positionToIndex(getPosition())));
105     }
106 
107     /***
108      * Returns the parent node pointer.
109      *
110      * @return the parent node pointer
111      */
112     protected NodePointer getParent()
113     {
114         return parent;
115     }
116 
117     /***
118      * Returns the start offset of the iteration.
119      *
120      * @return the start offset
121      */
122     protected int getStartOffset()
123     {
124         return startOffset;
125     }
126 
127     /***
128      * Sets the start offset of the iteration. This is used when a start element
129      * was set.
130      *
131      * @param startOffset the start offset
132      */
133     protected void setStartOffset(int startOffset)
134     {
135         this.startOffset = startOffset;
136         if (reverse)
137         {
138             this.startOffset--;
139         }
140         else
141         {
142             this.startOffset++;
143         }
144     }
145 
146     /***
147      * Initializes the list of sub nodes for the iteration. This method must be
148      * called during initialization phase.
149      *
150      * @param nodes the list with the sub nodes
151      */
152     protected void initSubNodeList(List nodes)
153     {
154         subNodes = nodes;
155         if (reverse)
156         {
157             setStartOffset(subNodes.size());
158         }
159     }
160 
161     /***
162      * Returns the maximum position for this iterator.
163      *
164      * @return the maximum allowed position
165      */
166     protected int getMaxPosition()
167     {
168         return reverse ? getStartOffset() + 1 : subNodes.size()
169                 - getStartOffset();
170     }
171 
172     /***
173      * Creates the configuration node pointer for the current position. This
174      * method is called by <code>getNodePointer()</code>. Derived classes
175      * must create the correct pointer object.
176      *
177      * @param node the current configuration node
178      * @return the node pointer
179      */
180     protected NodePointer createNodePointer(ConfigurationNode node)
181     {
182         return new ConfigurationNodePointer(getParent(), node);
183     }
184 
185     /***
186      * Returns the index in the data list for the given position. This method
187      * also checks the reverse flag.
188      *
189      * @param pos the position (1-based)
190      * @return the corresponding list index
191      */
192     protected int positionToIndex(int pos)
193     {
194         return (reverse ? 1 - pos : pos - 1) + getStartOffset();
195     }
196 }