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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.jxpath.ri.axes;
18  
19  import java.util.Stack;
20  
21  import org.apache.commons.jxpath.Pointer;
22  import org.apache.commons.jxpath.ri.Compiler;
23  import org.apache.commons.jxpath.ri.EvalContext;
24  import org.apache.commons.jxpath.ri.compiler.NodeTest;
25  import org.apache.commons.jxpath.ri.compiler.NodeTypeTest;
26  import org.apache.commons.jxpath.ri.model.NodeIterator;
27  import org.apache.commons.jxpath.ri.model.NodePointer;
28  
29  /**
30   * An EvalContext that walks the "descendant::" and "descendant-or-self::"
31   * axes.
32   *
33   * @author Dmitri Plotnikov
34   * @version $Revision: 670727 $ $Date: 2008-06-23 16:10:38 -0400 (Mon, 23 Jun 2008) $
35   */
36  public class DescendantContext extends EvalContext {
37      private NodeTest nodeTest;
38      private boolean setStarted = false;
39      private Stack stack = null;
40      private NodePointer currentNodePointer = null;
41      private boolean includeSelf;
42      private static final NodeTest ELEMENT_NODE_TEST =
43              new NodeTypeTest(Compiler.NODE_TYPE_NODE);
44  
45      /**
46       * Create a new DescendantContext.
47       * @param parentContext parent context
48       * @param includeSelf whether to include this node
49       * @param nodeTest test
50       */
51      public DescendantContext(EvalContext parentContext, boolean includeSelf,
52              NodeTest nodeTest) {
53          super(parentContext);
54          this.includeSelf = includeSelf;
55          this.nodeTest = nodeTest;
56      }
57  
58      public boolean isChildOrderingRequired() {
59          return true;
60      }
61  
62      public NodePointer getCurrentNodePointer() {
63          if (position == 0 && !setPosition(1)) {
64              return null;
65          }
66          return currentNodePointer;
67      }
68  
69      public void reset() {
70          super.reset();
71          setStarted = false;
72      }
73  
74      public boolean setPosition(int position) {
75          if (position < this.position) {
76              reset();
77          }
78  
79          while (this.position < position) {
80              if (!nextNode()) {
81                  return false;
82              }
83          }
84          return true;
85      }
86  
87      public boolean nextNode() {
88          if (!setStarted) {
89              setStarted = true;
90              if (stack == null) {
91                  stack = new Stack();
92              }
93              else {
94                  stack.clear();
95              }
96              currentNodePointer = parentContext.getCurrentNodePointer();
97              if (currentNodePointer != null) {
98                  if (!currentNodePointer.isLeaf()) {
99                      stack.push(
100                         currentNodePointer.childIterator(
101                             ELEMENT_NODE_TEST,
102                             false,
103                             null));
104                 }
105                 if (includeSelf && currentNodePointer.testNode(nodeTest)) {
106                     position++;
107                     return true;
108                 }
109             }
110         }
111 
112         while (!stack.isEmpty()) {
113             NodeIterator it = (NodeIterator) stack.peek();
114             if (it.setPosition(it.getPosition() + 1)) {
115                 currentNodePointer = it.getNodePointer();
116                 if (!isRecursive()) {
117                     if (!currentNodePointer.isLeaf()) {
118                         stack.push(
119                             currentNodePointer.childIterator(
120                                 ELEMENT_NODE_TEST,
121                                 false,
122                                 null));
123                     }
124                     if (currentNodePointer.testNode(nodeTest)) {
125                         position++;
126                         return true;
127                     }
128                 }
129             }
130             else {
131                 // We get here only if the name test failed
132                 // and the iterator ended
133                 stack.pop();
134             }
135         }
136         return false;
137     }
138 
139     /**
140      * Checks if we are reentering a bean we have already seen and if so
141      * returns true to prevent infinite recursion.
142      * @return boolean
143      */
144     private boolean isRecursive() {
145         Object node = currentNodePointer.getNode();
146         for (int i = stack.size() - 1; --i >= 0;) {
147             NodeIterator it = (NodeIterator) stack.get(i);
148             Pointer pointer = it.getNodePointer();
149             if (pointer != null && pointer.getNode() == node) {
150                 return true;
151             }
152         }
153         return false;
154     }
155 }