/*
* SonarQube
* Copyright (C) 2009-2017 SonarSource SA
* mailto:info AT sonarsource DOT com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 3 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.sonar.core.util;
/**
* A generator of UUID as a byte array which is made of two parts:
* <ul>
* <li>a base, which is machine and time dependant and therefor will change with time</li>
* <li>an increment</li>
* </ul>
*
* <p>
* This generator can be used in two ways:
* <ul>
* <li>either the base and the increment are changed for each UUID (with time for the base, with each call to
* {@link #generate()} for the increment) and {@link #generate()} should be used</li>
* <li>or the increment can be the only changing part (for performance boost and less concurrency) and
* {@link #withFixedBase()} should be used.</li>
* </ul>
* </p>
*
* <p>
* <strong>Warning:</strong> {@link WithFixedBase#generate(int)} can be considerably faster than {@link #generate()} but
* is limited to generate only 2^23-1 unique values.
* </p>
*
* <p>
* Heavily inspired from Elasticsearch {@code TimeBasedUUIDGenerator}, which could be directly
* used the day {@code UuidFactoryImpl} is moved outside module sonar-core.
* See https://github.com/elastic/elasticsearch/blob/master/core/src/main/java/org/elasticsearch/common/TimeBasedUUIDGenerator.java
* </p>
*/
public interface UuidGenerator {
/**
* Generates a UUID which base and increment are always different from any other value provided by this method.
*/
byte[] generate();
/**
* Provide a new UUID generating instance which will allow generation of UUIDs which base is constant and can
* vary according to a provided increment value (see {@link WithFixedBase#generate(int)}).
*/
WithFixedBase withFixedBase();
@FunctionalInterface
interface WithFixedBase {
/**
* Generate a new unique universal identifier using the last 3 bytes of the specified int.
* <p>
* <strong>This implies that this method of a given {@link WithFixedBase} instance can only generate up to
* 2^23-1 unique values if provided with unique int arguments.</strong>
* </p>
* <p>
* This is up to the caller to ensure that unique int values are provided to a given instance's {@link #generate(int)}
* method.
* </p>
* <p>
* This method is faster than {@link UuidGenerator#generate()} due to less computation and less internal concurrency.
* </p>
*/
byte[] generate(int increment);
}
}