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1   package org.codehaus.plexus.digest;
2   
3   /*
4    * Copyright 2001-2006 The Codehaus.
5    *
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * 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, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  import java.io.InputStream;
20  
21  /**
22   * Gradually create a digest for a stream.
23   *
24   * @author <a href="mailto:brett@apache.org">Brett Porter</a>
25   */
26  public interface StreamingDigester
27  {
28      String ROLE = StreamingDigester.class.getName();
29  
30      /**
31       * Get the algorithm used for the checksum.
32       *
33       * @return the algorithm
34       */
35      String getAlgorithm();
36  
37      /**
38       * Reset the hashcode calculation algorithm.
39       * Only useful when performing incremental hashcodes based on repeated use of {@link #update(InputStream)}
40       *
41       * @throws DigesterException if there was a problem with the internal message digest
42       */
43      void reset()
44          throws DigesterException;
45  
46      /**
47       * Calculate the current checksum.
48       *
49       * @return the current checksum.
50       * @throws DigesterException if there was a problem computing the hashcode.
51       */
52      String calc()
53          throws DigesterException;
54  
55      /**
56       * Update the checksum with the content of the input stream.
57       *
58       * @param is the input stream
59       * @throws DigesterException if there was a problem computing the hashcode.
60       */
61      void update( InputStream is )
62          throws DigesterException;
63  
64  }