FromContext


1   /*
2    * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
3    *
4    * This file is part of Resin(R) Open Source
5    *
6    * Each copy or derived work must preserve the copyright notice and this
7    * notice unmodified.
8    *
9    * Resin Open Source is free software; you can redistribute it and/or modify
10   * it under the terms of the GNU General Public License as published by
11   * the Free Software Foundation; either version 2 of the License, or
12   * (at your option) any later version.
13   *
14   * Resin Open Source is distributed in the hope that it will be useful,
15   * but WITHOUT ANY WARRANTY; without even the implied warranty of
16   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17   * of NON-INFRINGEMENT.  See the GNU General Public License for more
18   * details.
19   *
20   * You should have received a copy of the GNU General Public License
21   * along with Resin Open Source; if not, write to the
22   *   Free SoftwareFoundation, Inc.
23   *   59 Temple Place, Suite 330
24   *   Boston, MA 02111-1307  USA
25   *
26   * @author Scott Ferguson
27   */
28  
29  package com.caucho.xpath.pattern;
30  
31  import com.caucho.util.CharBuffer;
32  import com.caucho.xpath.Env;
33  import com.caucho.xpath.ExprEnvironment;
34  
35  import org.w3c.dom.Node  ;
36  
37  /**
38   * Matches the node context.
39   */
40  public class FromContext extends Axis {
41    // ancestor count from the specified context where this virtual context is
42    int _ancestorCount;
43    
44    public FromContext()
45    {
46      super(null);
47    }
48  
49    /**
50     * Creates a new context pattern.  Using the ancestorCount,
51     * FromContext collapses parent patterns into a single FromContext
52     * pattern.  For example, context()/../.. is collapsed to FromContext(2).
53     *
54     * @param ancestorCount number of parents where the real context starts
55     */
56    public FromContext(int ancestorCount)
57    {
58      super(null);
59  
60      _ancestorCount = ancestorCount;
61    }
62  
63    public int getCount()
64    {
65      return _ancestorCount;
66    }
67  
68    /**
69     * Matches the node context
70     *
71     * @param node the current node
72     * @param env the variable environment
73     *
74     * @return true if the node is the context node.
75     */
76    public boolean match(Node   node, ExprEnvironment env)
77    {
78      Node   context = env.getContextNode();
79  
80      for (int i = 0; i < _ancestorCount && context != null; i++)
81        context = context.getParentNode();
82      
83      return (node == context);
84    }
85  
86    /**
87     * The context is strictly ascending.
88     */
89    public boolean isStrictlyAscending()
90    {
91      return true;
92    }
93    
94    /**
95     * Returns true if the pattern selects a single node
96     */
97    boolean isSingleSelect()
98    {
99      return true;
100   }
101   
102   /**
103    * There is only a single node in the context axis.
104    *
105    * @param node the current node
106    * @param env the variable environment
107    * @param pattern the position pattern
108    *
109    * @return 1
110    */
111   public int position(Node   node, Env env, AbstractPattern pattern)
112   {
113     return 1;
114   }
115   
116   /**
117    * There is only a single node in the context axis.
118    *
119    * @param node the current node
120    * @param env the variable environment
121    * @param pattern the position pattern
122    *
123    * @return 1
124    */
125   public int count(Node   node, Env env, AbstractPattern pattern)
126   {
127     return 1;
128   }
129 
130   /**
131    * Returns the first node in the selection order.
132    *
133    * @param node the current node
134    * @param env the current environment
135    *
136    * @return the first node
137    */
138   public Node   firstNode(Node   node, ExprEnvironment env)
139   {
140     for (int i = 0; node != null && i < _ancestorCount; i++)
141       node = node.getParentNode();
142 
143     return node;
144   }
145 
146   /**
147    * Returns the next node in the selection order.
148    *
149    * @param node the current node
150    * @param lastNode the last node
151    *
152    * @return the next node
153    */
154   public Node   nextNode(Node   node, Node   lastNode)
155   {
156     return null;
157   }
158 
159   /**
160    * Returns true if the two patterns are equal.
161    */
162   public boolean equals(Object   b)
163   {
164     return (b instanceof FromContext &&
165             _ancestorCount == ((FromContext) b)._ancestorCount);
166   }
167 
168   /**
169    * Prints the pattern representing the context.
170    */
171   public String   toString()
172   {
173     if (_ancestorCount == 0)
174       return "context()";
175     
176     CharBuffer cb = CharBuffer.allocate();
177 
178     cb.append("..");
179 
180     for (int i = 1; i < _ancestorCount; i++) {
181       cb.append("/..");
182     }
183 
184     return cb.close();
185   }
186 }
187
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