Generators.java

April 17, 2024
Generators.java
/* JUG Java Uuid Generator * * Copyright (c) 2002- Tatu Saloranta, tatu.saloranta@iki.fi * * Licensed under the License specified in the file LICENSE which is * included with the source code. * You may not use this file except in compliance with the License. * * 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. */ /* * Portions Copyright (c) Microsoft Corporation */ package com.azure.cosmos.implementation.uuid; import com.azure.cosmos.implementation.uuid.ext.FileBasedTimestampSynchronizer; import com.azure.cosmos.implementation.uuid.impl.NameBasedGenerator; import com.azure.cosmos.implementation.uuid.impl.RandomBasedGenerator; import com.azure.cosmos.implementation.uuid.impl.TimeBasedGenerator; import java.io.IOException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.Random; import java.util.UUID; /** * Root factory class for constructing UUID generators. * * @author tatu * * @since 3.0 */ public class Generators { /** * If no explicit timer (and synchronizer it implicitly uses) is specified, * we will create and use a single lazily-constructed timer, which uses in-JVM * synchronization but no external file-based syncing. */ protected static UUIDTimer _sharedTimer; // // Random-based generation /** * Factory method for constructing UUID generator that uses default (shared) * random number generator for constructing UUIDs according to standard * method number 4. */ public static RandomBasedGenerator randomBasedGenerator() {  return randomBasedGenerator(null); } /** * Factory method for constructing UUID generator that uses specified * random number generator for constructing UUIDs according to standard * method number 4. */ public static RandomBasedGenerator randomBasedGenerator(Random rnd) {  return new RandomBasedGenerator(rnd); } // // Name-based generation /** * Factory method for constructing UUID generator that uses specified * random number generator for constructing UUIDs according to standard * method number 5, but without using a namespace. * Digester to use will be SHA-1 as recommened by UUID spec. */ public static NameBasedGenerator nameBasedGenerator() {  return nameBasedGenerator(null); } /** * Factory method for constructing UUID generator that uses specified * random number generator for constructing UUIDs according to standard * method number 5, with specified namespace (or without one if null * is specified). * Digester to use will be SHA-1 as recommened by UUID spec. * * @param namespace UUID that represents namespace to use; see * {@link NameBasedGenerator} for 'standard' namespaces specified by * UUID specs */ public static NameBasedGenerator nameBasedGenerator(UUID namespace) {  return nameBasedGenerator(namespace, null); } /** * Factory method for constructing UUID generator that uses specified * random number generator for constructing UUIDs according to standard * method number 3 or 5, with specified namespace (or without one if null * is specified), using specified digester. * If digester is passed as null, a SHA-1 digester will be constructed. * * @param namespace UUID that represents namespace to use; see * {@link NameBasedGenerator} for 'standard' namespaces specified by * UUID specs * @param digester Digester to use; should be a MD5 or SHA-1 digester. */ public static NameBasedGenerator nameBasedGenerator(UUID namespace, MessageDigest digester) {  UUIDType type = null;  if (digester == null) { try {  digester = MessageDigest.getInstance("SHA-1");  type = UUIDType.NAME_BASED_SHA1;  } catch (NoSuchAlgorithmException nex) {  throw new IllegalArgumentException("Couldn't instantiate SHA-1 MessageDigest instance: "+nex.toString());  } }  return new NameBasedGenerator(namespace, digester, type); } // // Time+location-based generation /** * Factory method for constructing UUID generator that generates UUID using * variant 1 (time+location based). * Since no Ethernet address is passed, a bogus broadcast address will be * constructed for purpose of UUID generation; usually it is better to * instead access one of host's NIC addresses using * {@link EthernetAddress#fromInterface} which will use one of available * MAC (Ethernet) addresses available. */ public static TimeBasedGenerator timeBasedGenerator() {  return timeBasedGenerator(null); } /** * Factory method for constructing UUID generator that generates UUID using * variant 1 (time+location based), using specified Ethernet address * as the location part of UUID. * No additional external synchronization is used. */ public static TimeBasedGenerator timeBasedGenerator(EthernetAddress ethernetAddress) {  return timeBasedGenerator(ethernetAddress, (UUIDTimer) null); } /** * Factory method for constructing UUID generator that generates UUID using * variant 1 (time+location based), using specified Ethernet address * as the location part of UUID, and specified synchronizer (which may add * additional restrictions to guarantee system-wide uniqueness). * * @param ethernetAddress (optional) MAC address to use; if null, a transient * random address is generated. * * @see FileBasedTimestampSynchronizer */ public static TimeBasedGenerator timeBasedGenerator(EthernetAddress ethernetAddress, TimestampSynchronizer sync) { UUIDTimer timer; try {  timer = new UUIDTimer(new Random(System.currentTimeMillis()), sync);  } catch (IOException e) {  throw new IllegalArgumentException("Failed to create UUIDTimer with specified synchronizer: "+e.getMessage(), e);  }  return timeBasedGenerator(ethernetAddress, timer); } /** * Factory method for constructing UUID generator that generates UUID using * variant 1 (time+location based), using specified Ethernet address * as the location part of UUID, and specified {@link UUIDTimer} instance * (which includes embedded synchronizer that defines synchronization behavior). */ public static TimeBasedGenerator timeBasedGenerator(EthernetAddress ethernetAddress, UUIDTimer timer) {  if (timer == null) {  timer = sharedTimer(); }  return new TimeBasedGenerator(ethernetAddress, timer); } /* /********************************************************************** /* Internal methods /********************************************************************** */ private static synchronized UUIDTimer sharedTimer() {  if (_sharedTimer == null) { try {  _sharedTimer = new UUIDTimer(new Random(System.currentTimeMillis()), null);  } catch (IOException e) {  throw new IllegalArgumentException("Failed to create UUIDTimer with specified synchronizer: "+e.getMessage(), e);  } }  return _sharedTimer; } }
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