src/test/org/apache/hadoop/io/TestMD5Hash.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.io;

import org.apache.hadoop.io.TestWritable;
import junit.framework.TestCase;
import java.security.MessageDigest;
import java.util.Random;

/** Unit tests for MD5Hash. */
public class TestMD5Hash extends TestCase {
  public TestMD5Hash(String name) { super(name); }

  private static final Random RANDOM = new Random();

  public static MD5Hash getTestHash() throws Exception {
    MessageDigest digest = MessageDigest.getInstance("MD5");
    byte[] buffer = new byte[1024];
    RANDOM.nextBytes(buffer);
    digest.update(buffer);
    return new MD5Hash(digest.digest());
  }

  public void testMD5Hash() throws Exception {
    MD5Hash md5Hash = getTestHash();

    MD5Hash md5Hash00
      = new MD5Hash(new byte[] {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0});

    MD5Hash md5HashFF
      = new MD5Hash(new byte[] {-1, -1, -1, -1, -1, -1, -1, -1,
                                -1, -1, -1, -1, -1, -1, -1, -1});
    
    MD5Hash orderedHash = new MD5Hash(new byte[]{1,2,3,4,5,6,7,8,9,10,11,12,
                                                 13,14,15,16});
    MD5Hash backwardHash = new MD5Hash(new byte[]{-1,-2,-3,-4,-5,-6,-7,-8,
                                                  -9,-10,-11,-12, -13, -14,
                                                  -15,-16});
    MD5Hash closeHash1 = new MD5Hash(new byte[]{-1,0,0,0,0,0,0,0,
                                                0,0,0,0,0,0,0,0});
    MD5Hash closeHash2 = new MD5Hash(new byte[]{-1,1,0,0,0,0,0,0,
                                                0,0,0,0,0,0,0,0});

    // test i/o
    TestWritable.testWritable(md5Hash);
    TestWritable.testWritable(md5Hash00);
    TestWritable.testWritable(md5HashFF);

    // test equals()
    assertEquals(md5Hash, md5Hash);
    assertEquals(md5Hash00, md5Hash00);
    assertEquals(md5HashFF, md5HashFF);

    // test compareTo()
    assertTrue(md5Hash.compareTo(md5Hash) == 0);
    assertTrue(md5Hash00.compareTo(md5Hash) < 0);
    assertTrue(md5HashFF.compareTo(md5Hash) > 0);

    // test toString and string ctor
    assertEquals(md5Hash, new MD5Hash(md5Hash.toString()));
    assertEquals(md5Hash00, new MD5Hash(md5Hash00.toString()));
    assertEquals(md5HashFF, new MD5Hash(md5HashFF.toString()));

    assertEquals(0x01020304, orderedHash.quarterDigest());
    assertEquals(0xfffefdfc, backwardHash.quarterDigest());
    
    assertEquals(0x0102030405060708L, orderedHash.halfDigest());
    assertEquals(0xfffefdfcfbfaf9f8L, backwardHash.halfDigest());
    assertTrue("hash collision", 
               closeHash1.hashCode() != closeHash2.hashCode());
  }
	
}