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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  
20  package org.apache.maven.plugins.shade.mojo;
21  
22  import java.io.File;
23  import java.util.ArrayList;
24  import java.util.Collections;
25  import java.util.List;
26  
27  /**
28   *
29   */
30  public final class RelativizePath
31  {
32      private RelativizePath() {
33          //
34      }
35  
36      /**
37       * relativize a pathname. 
38       * @param thing Absolute File of something. (e.g., a parent pom)
39       * @param relativeTo base to relativize it do. (e.g., a pom into which a relative pathname to the 'thing' is to be installed).
40       * @return
41       */
42      static String convertToRelativePath(File thing, File relativeTo) {
43          StringBuilder relativePath = null;
44          
45          if ( thing.getParentFile().equals( relativeTo.getParentFile() ))
46          {
47              return thing.getName(); // a very simple relative path.
48          }
49          
50          List<String> thingDirectories = RelativizePath.parentDirs( thing );
51          List<String> relativeToDirectories = RelativizePath.parentDirs( relativeTo );
52      
53          //Get the shortest of the two paths
54          int length = thingDirectories.size() < relativeToDirectories.size() ? thingDirectories.size() : relativeToDirectories.size();
55      
56          int lastCommonRoot = -1; // index of the lowest directory down from the root that the two have in common.
57          int index;
58      
59          //Find common root
60          for ( index = 0; index < length; index++ ) 
61          {
62              if ( thingDirectories.get( index ).equals(relativeToDirectories.get( index )))
63              {
64                  lastCommonRoot = index;
65              } else {
66                  break;
67              }
68          }
69          if (lastCommonRoot != -1) { // possible on Windows or other multi-root cases.
70              //Build up the relative path
71              relativePath = new StringBuilder();
72              // add ..'s to get from the base up to the common point
73              for ( index = lastCommonRoot + 1; index < relativeToDirectories.size(); index++ ) 
74              {
75                  relativePath.append( "../" );
76              }
77              
78              // now add down from the common point to the actual 'thing' item. 
79              for ( index = lastCommonRoot + 1; index < thingDirectories.size(); index++ ) 
80              {
81                  relativePath.append( thingDirectories.get( index ) + "/" );
82              }
83              relativePath.append( thing.getName() );
84              return relativePath.toString();
85          }
86          return null;
87      }
88  
89      static List<String> parentDirs( File of )
90      {
91          List<String> results = new ArrayList<String>();
92          for ( File p = of.getParentFile() ; p != null ; p = p.getParentFile() )
93          {
94              if ( !"".equals(p.getName()) )
95              {
96                  results.add( p.getName() );
97              }
98          }
99          
100         Collections.reverse( results );
101         return results;
102     }
103     
104     
105 
106 }