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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.utils;
import java.nio.ByteBuffer;
import java.security.SecureRandom;
import java.util.Random;
import static org.apache.cassandra.config.CassandraRelevantProperties.JAVA_SECURITY_EGD;
import static org.apache.cassandra.utils.Clock.Global.currentTimeMillis;
public class GuidGenerator
{
private static final Random myRand;
private static final SecureRandom mySecureRand;
private static final String s_id;
static
{
if (!JAVA_SECURITY_EGD.isPresent())
{
JAVA_SECURITY_EGD.setString("file:/dev/urandom");
}
mySecureRand = new SecureRandom();
long secureInitializer = mySecureRand.nextLong();
myRand = new Random(secureInitializer);
try {
s_id = FBUtilities.getLocalAddressAndPort().toString();
}
catch (RuntimeException e) {
throw new AssertionError(e);
}
}
public static String guid()
{
ByteBuffer array = guidAsBytes();
StringBuilder sb = new StringBuilder();
for (int j = array.position(); j < array.limit(); ++j)
{
int b = array.get(j) & 0xFF;
if (b < 0x10) sb.append('0');
sb.append(Integer.toHexString(b));
}
return convertToStandardFormat( sb.toString() );
}
public static String guidToString(byte[] bytes)
{
StringBuilder sb = new StringBuilder();
for (int j = 0; j < bytes.length; ++j)
{
int b = bytes[j] & 0xFF;
if (b < 0x10) sb.append('0');
sb.append(Integer.toHexString(b));
}
return convertToStandardFormat( sb.toString() );
}
public static ByteBuffer guidAsBytes(Random random, String hostId, long time)
{
StringBuilder sbValueBeforeMD5 = new StringBuilder();
long rand = random.nextLong();
sbValueBeforeMD5.append(hostId)
.append(":")
.append(Long.toString(time))
.append(":")
.append(Long.toString(rand));
String valueBeforeMD5 = sbValueBeforeMD5.toString();
return ByteBuffer.wrap(MD5Digest.threadLocalMD5Digest().digest(valueBeforeMD5.getBytes()));
}
public static ByteBuffer guidAsBytes()
{
return guidAsBytes(myRand, s_id, currentTimeMillis());
}
/*
* Convert to the standard format for GUID
* Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6
*/
private static String convertToStandardFormat(String valueAfterMD5)
{
String raw = valueAfterMD5.toUpperCase();
StringBuilder sb = new StringBuilder();
sb.append(raw.substring(0, 8))
.append("-")
.append(raw.substring(8, 12))
.append("-")
.append(raw.substring(12, 16))
.append("-")
.append(raw.substring(16, 20))
.append("-")
.append(raw.substring(20));
return sb.toString();
}
}