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1   /*
2    * $Header$
3    * $Revision$
4    * $Date$
5    *
6    * ====================================================================
7    *
8    * Copyright (C) 2005 Elliotte Rusty Harold.
9    * All rights reserved.
10   *
11   * Redistribution and use in source and binary forms, with or without
12   * modification, are permitted provided that the following conditions
13   * are met:
14   * 
15   * 1. Redistributions of source code must retain the above copyright
16   *    notice, this list of conditions, and the following disclaimer.
17   *
18   * 2. Redistributions in binary form must reproduce the above copyright
19   *    notice, this list of conditions, and the disclaimer that follows 
20   *    these conditions in the documentation and/or other materials 
21   *    provided with the distribution.
22   *
23   * 3. The name "Jaxen" must not be used to endorse or promote products
24   *    derived from this software without prior written permission.  For
25   *    written permission, please contact license@jaxen.org.
26   * 
27   * 4. Products derived from this software may not be called "Jaxen", nor
28   *    may "Jaxen" appear in their name, without prior written permission
29   *    from the Jaxen Project Management (pm@jaxen.org).
30   * 
31   * In addition, we request (but do not require) that you include in the 
32   * end-user documentation provided with the redistribution and/or in the 
33   * software itself an acknowledgement equivalent to the following:
34   *     "This product includes software developed by the
35   *      Jaxen Project (http://www.jaxen.org/)."
36   * Alternatively, the acknowledgment may be graphical using the logos 
37   * available at http://www.jaxen.org/
38   *
39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50   * SUCH DAMAGE.
51   *
52   * ====================================================================
53   * This software consists of voluntary contributions made by many 
54   * individuals on behalf of the Jaxen Project and was originally 
55   * created by bob mcwhirter <bob@werken.com> and 
56   * James Strachan <jstrachan@apache.org>.  For more information on the 
57   * Jaxen Project, please see <http://www.jaxen.org/>.
58   * 
59   * $Id$
60   */
61  package org.jaxen.expr;
62  
63  import java.util.Comparator;
64  import java.util.Iterator;
65  
66  import org.jaxen.Navigator;
67  import org.jaxen.UnsupportedAxisException;
68  
69  
70  class NodeComparator implements Comparator {
71      
72      private Navigator navigator;
73  
74  
75      NodeComparator(Navigator navigator) {
76          this.navigator = navigator;
77      }
78      
79      public int compare(Object o1, Object o2) {
80          
81          if (navigator == null) return 0;
82          
83          if (isNonChild(o1) && isNonChild(o2)) {
84              try {
85                  return compare(navigator.getParentNode(o1), navigator.getParentNode(o2));
86              }
87              catch (UnsupportedAxisException ex) {
88                  return 0;
89              }
90          }
91  
92          try {
93              int depth1 = getDepth(o1);
94              int depth2 = getDepth(o2);
95              
96              Object a1 = o1;
97              Object a2 = o2;
98                          
99              while (depth1 > depth2) {
100                 a1 = navigator.getParentNode(a1);
101                 depth1--;
102             }
103             if (a1 == o2) return 1;
104             
105             while (depth2 > depth1) {
106                 a2 = navigator.getParentNode(a2);
107                 depth2--;
108             }
109             if (a2 == o1) return -1;
110             
111             // a1 and a2 are now at same depth; and are not the same
112             while (true) {
113                 Object p1 = navigator.getParentNode(a1);
114                 Object p2 = navigator.getParentNode(a2);
115                 if (p1 == p2) {
116                     return compareSiblings(a1, a2);
117                 }
118                 a1 = p1;
119                 a2 = p2;
120             }
121             
122         }
123         catch (UnsupportedAxisException ex) {
124             return 0; // ???? should I throw an exception instead?
125         }
126     }
127     
128 
129     private boolean isNonChild(Object o) {
130         return navigator.isAttribute(o) || navigator.isNamespace(o);
131     }
132 
133     private int compareSiblings(Object sib1, Object sib2) 
134       throws UnsupportedAxisException {
135 
136         Iterator following = navigator.getFollowingSiblingAxisIterator(sib1);
137         while (following.hasNext()) {
138             Object next = following.next();
139             if (next.equals(sib2)) return -1;
140         }
141         return 1;
142         
143     }
144 
145     private int getDepth(Object o) throws UnsupportedAxisException {
146 
147         int depth = 0;
148         Object parent = o;
149         
150         while ((parent = navigator.getParentNode(parent)) != null) {
151             depth++;
152         }
153         return depth;
154         
155     }
156     
157 }