MultiFileChecksumHelper xref

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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.jetspeed.util;
18  
19  import java.io.File;
20  import java.io.FileInputStream;
21  import java.io.IOException;
22  import java.util.zip.Adler32;
23  import java.util.zip.CheckedInputStream;
24  import java.util.zip.Checksum;
25  
26  /***
27   * Perform a single checksum calculation for multiple files
28   *
29   * @author <a href="mailto:ate@douma.nu">Ate Douma</a>
30   * @author <a href="mailto:taylor@apache.org">David Sean Taylor </a>
31   * @version $Id$
32   */
33  public class MultiFileChecksumHelper
34  {
35      public static long getChecksum(File[] files)
36      {
37          CheckedInputStream cis = null;
38          FileInputStream is = null;
39          Checksum checksum = new Adler32();
40          byte[] tempBuf = new byte[128];
41          
42          for ( int i = 0; i < files.length && files[i] != null && files[i].exists() && files[i].isFile(); i++ )
43          {
44              try 
45              {
46                  is = new FileInputStream(files[i]);
47                  cis = new CheckedInputStream(is, checksum);
48                  while (cis.read(tempBuf) >= 0) {}                
49              }
50              catch (Exception e)
51              {
52                  throw new RuntimeException(e);
53              }
54              finally
55              {
56                  if (cis != null)
57                  {
58                      try
59                      {
60                          cis.close();
61                      }
62                      catch (IOException ioe) {}
63                      cis = null;
64                  }
65                  if (is != null)
66                  {
67                      try
68                      {
69                          is.close();
70                      }
71                      catch (IOException ioe) {}
72                      is = null;
73                  }
74              }
75          }
76          return checksum.getValue();
77      }
78  }