org.apache.hadoop.io.MD5Hash Maven / Gradle / Ivy
/**
* 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 java.io.IOException;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.InputStream;
import java.util.Arrays;
import java.security.*;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/** A Writable for MD5 hash values.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class MD5Hash implements WritableComparable {
public static final int MD5_LEN = 16;
private static ThreadLocal DIGESTER_FACTORY = new ThreadLocal() {
@Override
protected MessageDigest initialValue() {
try {
return MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
}
};
private byte[] digest;
/** Constructs an MD5Hash. */
public MD5Hash() {
this.digest = new byte[MD5_LEN];
}
/** Constructs an MD5Hash from a hex string. */
public MD5Hash(String hex) {
setDigest(hex);
}
/** Constructs an MD5Hash with a specified value. */
public MD5Hash(byte[] digest) {
if (digest.length != MD5_LEN)
throw new IllegalArgumentException("Wrong length: " + digest.length);
this.digest = digest;
}
// javadoc from Writable
@Override
public void readFields(DataInput in) throws IOException {
in.readFully(digest);
}
/** Constructs, reads and returns an instance. */
public static MD5Hash read(DataInput in) throws IOException {
MD5Hash result = new MD5Hash();
result.readFields(in);
return result;
}
// javadoc from Writable
@Override
public void write(DataOutput out) throws IOException {
out.write(digest);
}
/** Copy the contents of another instance into this instance. */
public void set(MD5Hash that) {
System.arraycopy(that.digest, 0, this.digest, 0, MD5_LEN);
}
/** Returns the digest bytes. */
public byte[] getDigest() { return digest; }
/** Construct a hash value for a byte array. */
public static MD5Hash digest(byte[] data) {
return digest(data, 0, data.length);
}
/**
* Create a thread local MD5 digester
*/
public static MessageDigest getDigester() {
MessageDigest digester = DIGESTER_FACTORY.get();
digester.reset();
return digester;
}
/** Construct a hash value for the content from the InputStream. */
public static MD5Hash digest(InputStream in) throws IOException {
final byte[] buffer = new byte[4*1024];
final MessageDigest digester = getDigester();
for(int n; (n = in.read(buffer)) != -1; ) {
digester.update(buffer, 0, n);
}
return new MD5Hash(digester.digest());
}
/** Construct a hash value for a byte array. */
public static MD5Hash digest(byte[] data, int start, int len) {
byte[] digest;
MessageDigest digester = getDigester();
digester.update(data, start, len);
digest = digester.digest();
return new MD5Hash(digest);
}
/** Construct a hash value for a String. */
public static MD5Hash digest(String string) {
return digest(UTF8.getBytes(string));
}
/** Construct a hash value for a String. */
public static MD5Hash digest(UTF8 utf8) {
return digest(utf8.getBytes(), 0, utf8.getLength());
}
/** Construct a half-sized version of this MD5. Fits in a long **/
public long halfDigest() {
long value = 0;
for (int i = 0; i < 8; i++)
value |= ((digest[i] & 0xffL) << (8*(7-i)));
return value;
}
/**
* Return a 32-bit digest of the MD5.
* @return the first 4 bytes of the md5
*/
public int quarterDigest() {
int value = 0;
for (int i = 0; i < 4; i++)
value |= ((digest[i] & 0xff) << (8*(3-i)));
return value;
}
/** Returns true iff o is an MD5Hash whose digest contains the
* same values. */
@Override
public boolean equals(Object o) {
if (!(o instanceof MD5Hash))
return false;
MD5Hash other = (MD5Hash)o;
return Arrays.equals(this.digest, other.digest);
}
/** Returns a hash code value for this object.
* Only uses the first 4 bytes, since md5s are evenly distributed.
*/
@Override
public int hashCode() {
return quarterDigest();
}
/** Compares this object with the specified object for order.*/
@Override
public int compareTo(MD5Hash that) {
return WritableComparator.compareBytes(this.digest, 0, MD5_LEN,
that.digest, 0, MD5_LEN);
}
/** A WritableComparator optimized for MD5Hash keys. */
public static class Comparator extends WritableComparator {
public Comparator() {
super(MD5Hash.class);
}
@Override
public int compare(byte[] b1, int s1, int l1,
byte[] b2, int s2, int l2) {
return compareBytes(b1, s1, MD5_LEN, b2, s2, MD5_LEN);
}
}
static { // register this comparator
WritableComparator.define(MD5Hash.class, new Comparator());
}
private static final char[] HEX_DIGITS =
{'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
/** Returns a string representation of this object. */
@Override
public String toString() {
StringBuilder buf = new StringBuilder(MD5_LEN*2);
for (int i = 0; i < MD5_LEN; i++) {
int b = digest[i];
buf.append(HEX_DIGITS[(b >> 4) & 0xf]);
buf.append(HEX_DIGITS[b & 0xf]);
}
return buf.toString();
}
/** Sets the digest value from a hex string. */
public void setDigest(String hex) {
if (hex.length() != MD5_LEN*2)
throw new IllegalArgumentException("Wrong length: " + hex.length());
byte[] digest = new byte[MD5_LEN];
for (int i = 0; i < MD5_LEN; i++) {
int j = i << 1;
digest[i] = (byte)(charToNibble(hex.charAt(j)) << 4 |
charToNibble(hex.charAt(j+1)));
}
this.digest = digest;
}
private static final int charToNibble(char c) {
if (c >= '0' && c <= '9') {
return c - '0';
} else if (c >= 'a' && c <= 'f') {
return 0xa + (c - 'a');
} else if (c >= 'A' && c <= 'F') {
return 0xA + (c - 'A');
} else {
throw new RuntimeException("Not a hex character: " + c);
}
}
}
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