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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.axes;
17  
18  import java.util.Stack;
19  
20  import org.apache.commons.jxpath.Pointer;
21  import org.apache.commons.jxpath.ri.Compiler;
22  import org.apache.commons.jxpath.ri.EvalContext;
23  import org.apache.commons.jxpath.ri.compiler.NodeTest;
24  import org.apache.commons.jxpath.ri.compiler.NodeTypeTest;
25  import org.apache.commons.jxpath.ri.model.NodeIterator;
26  import org.apache.commons.jxpath.ri.model.NodePointer;
27  
28  /***
29   * An EvalContext that walks the "descendant::" and "descendant-or-self::"
30   * axes.
31   *
32   * @author Dmitri Plotnikov
33   * @version $Revision: 1.16 $ $Date: 2004/02/29 14:17:38 $
34   */
35  public class DescendantContext extends EvalContext {
36      private NodeTest nodeTest;
37      private boolean setStarted = false;
38      private Stack stack;
39      private NodePointer currentNodePointer;
40      private boolean includeSelf;
41      private static final NodeTest ELEMENT_NODE_TEST =
42              new NodeTypeTest(Compiler.NODE_TYPE_NODE);
43                          
44      public DescendantContext(
45              EvalContext parentContext,
46              boolean includeSelf,
47              NodeTest nodeTest) 
48      {
49          super(parentContext);
50          this.includeSelf = includeSelf;
51          this.nodeTest = nodeTest;
52      }
53  
54      public boolean isChildOrderingRequired() {
55          return true;
56      }
57  
58      public NodePointer getCurrentNodePointer() {
59          if (position == 0) {
60              if (!setPosition(1)) {
61                  return null;
62              }
63          }
64          return currentNodePointer;
65      }
66  
67      public void reset() {
68          super.reset();
69          setStarted = false;
70      }
71  
72      public boolean setPosition(int position) {
73          if (position < this.position) {
74              reset();
75          }
76  
77          while (this.position < position) {
78              if (!nextNode()) {
79                  return false;
80              }
81          }
82          return true;
83      }
84  
85      public boolean nextNode() {
86          if (!setStarted) {
87              setStarted = true;
88              stack = new Stack();
89              currentNodePointer = parentContext.getCurrentNodePointer();
90              if (currentNodePointer != null) {
91                  if (!currentNodePointer.isLeaf()) {
92                      stack.push(
93                          currentNodePointer.childIterator(
94                              ELEMENT_NODE_TEST,
95                              false,
96                              null));
97                  }
98                  if (includeSelf) {
99                      if (currentNodePointer.testNode(nodeTest)) {
100                         position++;
101                         return true;
102                     }
103                 }
104             }
105         }
106 
107         while (!stack.isEmpty()) {
108             NodeIterator it = (NodeIterator) stack.peek();
109             if (it.setPosition(it.getPosition() + 1)) {
110                 currentNodePointer = it.getNodePointer();
111                 if (!isRecursive()) {
112                     if (!currentNodePointer.isLeaf()) {
113                         stack.push(
114                             currentNodePointer.childIterator(
115                                 ELEMENT_NODE_TEST,
116                                 false,
117                                 null));
118                     }
119                     if (currentNodePointer.testNode(nodeTest)) {
120                         position++;
121                         return true;
122                     }
123                 }
124             }
125             else {
126                 // We get here only if the name test failed 
127                 // and the iterator ended
128                 stack.pop();
129             }
130         }
131         return false;
132     }
133 
134     /***
135      * Checks if we are reentering a bean we have already seen and if so
136      * returns true to prevent infinite recursion.
137      */
138     private boolean isRecursive() {
139         Object node = currentNodePointer.getNode();
140         for (int i = stack.size() - 1; --i >= 0;) {
141             NodeIterator it = (NodeIterator) stack.get(i);
142             Pointer pointer = it.getNodePointer();
143             if (pointer != null && pointer.getNode() == node) {
144                 return true;
145             }
146         }
147         return false;
148     }
149 }