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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 <a
37   * href="http://commons.apache.org/configuration/team-list.html">Commons
38   * Configuration team</a>
39   * @version $Id: ConfigurationNodeIteratorBase.java 1206491 2011-11-26 16:51:50Z oheger $
40   */
41  abstract class ConfigurationNodeIteratorBase implements NodeIterator
42  {
43      /** Stores the parent node pointer. */
44      private NodePointer parent;
45  
46      /** Stores the list with the sub nodes. */
47      private List<ConfigurationNode> subNodes;
48  
49      /** Stores the current position. */
50      private int position;
51  
52      /** Stores the start offset of the iterator. */
53      private int startOffset;
54  
55      /** Stores the reverse flag. */
56      private boolean reverse;
57  
58      /**
59       * Creates a new instance of {@code ConfigurationNodeIteratorBase}
60       * and initializes it.
61       *
62       * @param parent the parent pointer
63       * @param reverse the reverse flag
64       */
65      protected ConfigurationNodeIteratorBase(NodePointer parent, boolean reverse)
66      {
67          this.parent = parent;
68          this.reverse = reverse;
69      }
70  
71      /**
72       * Returns the position of the iteration.
73       *
74       * @return the position
75       */
76      public int getPosition()
77      {
78          return position;
79      }
80  
81      /**
82       * Sets the position of the iteration.
83       *
84       * @param pos the new position
85       * @return a flag if this is a valid position
86       */
87      public boolean setPosition(int pos)
88      {
89          position = pos;
90          return pos >= 1 && pos <= getMaxPosition();
91      }
92  
93      /**
94       * Returns the current node pointer.
95       *
96       * @return the current pointer in this iteration
97       */
98      public NodePointer getNodePointer()
99      {
100         if (getPosition() < 1 && !setPosition(1))
101         {
102             return null;
103         }
104 
105         return createNodePointer(subNodes.get(positionToIndex(getPosition())));
106     }
107 
108     /**
109      * Returns the parent node pointer.
110      *
111      * @return the parent node pointer
112      */
113     protected NodePointer getParent()
114     {
115         return parent;
116     }
117 
118     /**
119      * Returns the start offset of the iteration.
120      *
121      * @return the start offset
122      */
123     protected int getStartOffset()
124     {
125         return startOffset;
126     }
127 
128     /**
129      * Sets the start offset of the iteration. This is used when a start element
130      * was set.
131      *
132      * @param startOffset the start offset
133      */
134     protected void setStartOffset(int startOffset)
135     {
136         this.startOffset = startOffset;
137         if (reverse)
138         {
139             this.startOffset--;
140         }
141         else
142         {
143             this.startOffset++;
144         }
145     }
146 
147     /**
148      * Initializes the list of sub nodes for the iteration. This method must be
149      * called during initialization phase.
150      *
151      * @param nodes the list with the sub nodes
152      */
153     protected void initSubNodeList(List<ConfigurationNode> nodes)
154     {
155         subNodes = nodes;
156         if (reverse)
157         {
158             setStartOffset(subNodes.size());
159         }
160     }
161 
162     /**
163      * Returns the maximum position for this iterator.
164      *
165      * @return the maximum allowed position
166      */
167     protected int getMaxPosition()
168     {
169         return reverse ? getStartOffset() + 1 : subNodes.size()
170                 - getStartOffset();
171     }
172 
173     /**
174      * Creates the configuration node pointer for the current position. This
175      * method is called by {@code getNodePointer()}. Derived classes
176      * must create the correct pointer object.
177      *
178      * @param node the current configuration node
179      * @return the node pointer
180      */
181     protected NodePointer createNodePointer(ConfigurationNode node)
182     {
183         return new ConfigurationNodePointer(getParent(), node);
184     }
185 
186     /**
187      * Returns the index in the data list for the given position. This method
188      * also checks the reverse flag.
189      *
190      * @param pos the position (1-based)
191      * @return the corresponding list index
192      */
193     protected int positionToIndex(int pos)
194     {
195         return (reverse ? 1 - pos : pos - 1) + getStartOffset();
196     }
197 }