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1   /**
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  
20  package org.apache.hadoop.hbase.util;
21  
22  import java.security.MessageDigest;
23  import java.security.NoSuchAlgorithmException;
24  
25  import org.apache.commons.codec.binary.Hex;
26  import org.apache.commons.logging.Log;
27  import org.apache.commons.logging.LogFactory;
28  import org.apache.hadoop.classification.InterfaceAudience;
29  import org.apache.hadoop.classification.InterfaceStability;
30  
31  /**
32   * Utility class for MD5
33   * MD5 hash produces a 128-bit digest.
34   */
35  @InterfaceAudience.Public
36  @InterfaceStability.Stable
37  public class MD5Hash {
38    private static final Log LOG = LogFactory.getLog(MD5Hash.class);
39  
40    /**
41     * Given a byte array, returns in MD5 hash as a hex string.
42     * @param key
43     * @return SHA1 hash as a 32 character hex string.
44     */
45    public static String getMD5AsHex(byte[] key) {
46      return getMD5AsHex(key, 0, key.length);
47    }
48    
49    /**
50     * Given a byte array, returns its MD5 hash as a hex string.
51     * Only "length" number of bytes starting at "offset" within the
52     * byte array are used.
53     *
54     * @param key the key to hash (variable length byte array)
55     * @param offset
56     * @param length 
57     * @return MD5 hash as a 32 character hex string.
58     */
59    public static String getMD5AsHex(byte[] key, int offset, int length) {
60      try {
61        MessageDigest md = MessageDigest.getInstance("MD5");
62        md.update(key, offset, length);
63        byte[] digest = md.digest();
64        return new String(Hex.encodeHex(digest));
65      } catch (NoSuchAlgorithmException e) {
66        // this should never happen unless the JDK is messed up.
67        throw new RuntimeException("Error computing MD5 hash", e);
68      }
69    }
70  }