/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.common;
import java.io.IOException;
import java.util.Base64;
import java.util.Random;
class RandomBasedUUIDGenerator implements UUIDGenerator {
/**
* Returns a Base64 encoded version of a Version 4.0 compatible UUID
* as defined here: http://www.ietf.org/rfc/rfc4122.txt
*/
@Override
public String getBase64UUID() {
return getBase64UUID(SecureRandomHolder.INSTANCE);
}
/**
* Returns a Base64 encoded version of a Version 4.0 compatible UUID
* randomly initialized by the given {@link java.util.Random} instance
* as defined here: http://www.ietf.org/rfc/rfc4122.txt
*/
public String getBase64UUID(Random random) {
final byte[] randomBytes = new byte[16];
random.nextBytes(randomBytes);
/* Set the version to version 4 (see http://www.ietf.org/rfc/rfc4122.txt)
* The randomly or pseudo-randomly generated version.
* The version number is in the most significant 4 bits of the time
* stamp (bits 4 through 7 of the time_hi_and_version field).*/
randomBytes[6] &= 0x0f; /* clear the 4 most significant bits for the version */
randomBytes[6] |= 0x40; /* set the version to 0100 / 0x40 */
/* Set the variant:
* The high field of th clock sequence multiplexed with the variant.
* We set only the MSB of the variant*/
randomBytes[8] &= 0x3f; /* clear the 2 most significant bits */
randomBytes[8] |= 0x80; /* set the variant (MSB is set)*/
return Base64.getUrlEncoder().withoutPadding().encodeToString(randomBytes);
}
}