001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.io;
020
021import java.io.IOException;
022import java.io.DataInput;
023import java.io.DataOutput;
024import java.io.InputStream;
025import java.util.Arrays;
026import java.security.*;
027
028import org.apache.hadoop.classification.InterfaceAudience;
029import org.apache.hadoop.classification.InterfaceStability;
030
031/** A Writable for MD5 hash values.
032 */
033@InterfaceAudience.Public
034@InterfaceStability.Stable
035public class MD5Hash implements WritableComparable<MD5Hash> {
036  public static final int MD5_LEN = 16;
037
038  private static ThreadLocal<MessageDigest> DIGESTER_FACTORY = new ThreadLocal<MessageDigest>() {
039    @Override
040    protected MessageDigest initialValue() {
041      try {
042        return MessageDigest.getInstance("MD5");
043      } catch (NoSuchAlgorithmException e) {
044        throw new RuntimeException(e);
045      }
046    }
047  };
048
049  private byte[] digest;
050
051  /** Constructs an MD5Hash. */
052  public MD5Hash() {
053    this.digest = new byte[MD5_LEN];
054  }
055
056  /** Constructs an MD5Hash from a hex string. */
057  public MD5Hash(String hex) {
058    setDigest(hex);
059  }
060  
061  /** Constructs an MD5Hash with a specified value. */
062  public MD5Hash(byte[] digest) {
063    if (digest.length != MD5_LEN)
064      throw new IllegalArgumentException("Wrong length: " + digest.length);
065    this.digest = digest;
066  }
067  
068  // javadoc from Writable
069  @Override
070  public void readFields(DataInput in) throws IOException {
071    in.readFully(digest);
072  }
073
074  /** Constructs, reads and returns an instance. */
075  public static MD5Hash read(DataInput in) throws IOException {
076    MD5Hash result = new MD5Hash();
077    result.readFields(in);
078    return result;
079  }
080
081  // javadoc from Writable
082  @Override
083  public void write(DataOutput out) throws IOException {
084    out.write(digest);
085  }
086
087  /** Copy the contents of another instance into this instance. */
088  public void set(MD5Hash that) {
089    System.arraycopy(that.digest, 0, this.digest, 0, MD5_LEN);
090  }
091
092  /** Returns the digest bytes. */
093  public byte[] getDigest() { return digest; }
094
095  /** Construct a hash value for a byte array. */
096  public static MD5Hash digest(byte[] data) {
097    return digest(data, 0, data.length);
098  }
099
100  /**
101   * Create a thread local MD5 digester
102   */
103  public static MessageDigest getDigester() {
104    MessageDigest digester = DIGESTER_FACTORY.get();
105    digester.reset();
106    return digester;
107  }
108
109  /** Construct a hash value for the content from the InputStream. */
110  public static MD5Hash digest(InputStream in) throws IOException {
111    final byte[] buffer = new byte[4*1024]; 
112
113    final MessageDigest digester = getDigester();
114    for(int n; (n = in.read(buffer)) != -1; ) {
115      digester.update(buffer, 0, n);
116    }
117
118    return new MD5Hash(digester.digest());
119  }
120
121  /** Construct a hash value for a byte array. */
122  public static MD5Hash digest(byte[] data, int start, int len) {
123    byte[] digest;
124    MessageDigest digester = getDigester();
125    digester.update(data, start, len);
126    digest = digester.digest();
127    return new MD5Hash(digest);
128  }
129
130  /** Construct a hash value for a String. */
131  public static MD5Hash digest(String string) {
132    return digest(UTF8.getBytes(string));
133  }
134
135  /** Construct a hash value for a String. */
136  public static MD5Hash digest(UTF8 utf8) {
137    return digest(utf8.getBytes(), 0, utf8.getLength());
138  }
139
140  /** Construct a half-sized version of this MD5.  Fits in a long **/
141  public long halfDigest() {
142    long value = 0;
143    for (int i = 0; i < 8; i++)
144      value |= ((digest[i] & 0xffL) << (8*(7-i)));
145    return value;
146  }
147
148  /**
149   * Return a 32-bit digest of the MD5.
150   * @return the first 4 bytes of the md5
151   */
152  public int quarterDigest() {
153    int value = 0;
154    for (int i = 0; i < 4; i++)
155      value |= ((digest[i] & 0xff) << (8*(3-i)));
156    return value;    
157  }
158
159  /** Returns true iff <code>o</code> is an MD5Hash whose digest contains the
160   * same values.  */
161  @Override
162  public boolean equals(Object o) {
163    if (!(o instanceof MD5Hash))
164      return false;
165    MD5Hash other = (MD5Hash)o;
166    return Arrays.equals(this.digest, other.digest);
167  }
168
169  /** Returns a hash code value for this object.
170   * Only uses the first 4 bytes, since md5s are evenly distributed.
171   */
172  @Override
173  public int hashCode() {
174    return quarterDigest();
175  }
176
177
178  /** Compares this object with the specified object for order.*/
179  @Override
180  public int compareTo(MD5Hash that) {
181    return WritableComparator.compareBytes(this.digest, 0, MD5_LEN,
182                                           that.digest, 0, MD5_LEN);
183  }
184
185  /** A WritableComparator optimized for MD5Hash keys. */
186  public static class Comparator extends WritableComparator {
187    public Comparator() {
188      super(MD5Hash.class);
189    }
190
191    @Override
192    public int compare(byte[] b1, int s1, int l1,
193                       byte[] b2, int s2, int l2) {
194      return compareBytes(b1, s1, MD5_LEN, b2, s2, MD5_LEN);
195    }
196  }
197
198  static {                                        // register this comparator
199    WritableComparator.define(MD5Hash.class, new Comparator());
200  }
201
202  private static final char[] HEX_DIGITS =
203  {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
204
205  /** Returns a string representation of this object. */
206  @Override
207  public String toString() {
208    StringBuilder buf = new StringBuilder(MD5_LEN*2);
209    for (int i = 0; i < MD5_LEN; i++) {
210      int b = digest[i];
211      buf.append(HEX_DIGITS[(b >> 4) & 0xf]);
212      buf.append(HEX_DIGITS[b & 0xf]);
213    }
214    return buf.toString();
215  }
216
217  /** Sets the digest value from a hex string. */
218  public void setDigest(String hex) {
219    if (hex.length() != MD5_LEN*2)
220      throw new IllegalArgumentException("Wrong length: " + hex.length());
221    byte[] digest = new byte[MD5_LEN];
222    for (int i = 0; i < MD5_LEN; i++) {
223      int j = i << 1;
224      digest[i] = (byte)(charToNibble(hex.charAt(j)) << 4 |
225                         charToNibble(hex.charAt(j+1)));
226    }
227    this.digest = digest;
228  }
229
230  private static final int charToNibble(char c) {
231    if (c >= '0' && c <= '9') {
232      return c - '0';
233    } else if (c >= 'a' && c <= 'f') {
234      return 0xa + (c - 'a');
235    } else if (c >= 'A' && c <= 'F') {
236      return 0xA + (c - 'A');
237    } else {
238      throw new RuntimeException("Not a hex character: " + c);
239    }
240  }
241
242
243}