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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * 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.activemq.artemis.utils;

import java.util.concurrent.atomic.AtomicLong;

/**
 * A TimeAndCounterIDGenerator
 * 
 * This IDGenerator doesn't support more than 16777215 IDs per 16 millisecond. It would throw an exception if this happens.
 * 
 */
public class TimeAndCounterIDGenerator implements IDGenerator {


   /**
    * Bits to move the date accordingly to MASK_TIME
    */
   private static final int BITS_TO_MOVE = 20;

   public static final long MASK_TIME = 0x7fffffffff0L;

   // 44 bits of time and 20 bits of counter

   public static final long ID_MASK = 0xffffffL;

   private static final long TIME_ID_MASK = 0x7fffffffff000000L;


   private final AtomicLong counter = new AtomicLong(0);

   private volatile boolean wrapped = false;

   private volatile long tmMark;


   public TimeAndCounterIDGenerator() {
      refresh();
   }



   @Override
   public long generateID() {
      long idReturn = counter.incrementAndGet();

      if ((idReturn & TimeAndCounterIDGenerator.ID_MASK) == 0) {
         final long timePortion = idReturn & TimeAndCounterIDGenerator.TIME_ID_MASK;

         // Wrapping ID logic

         if (timePortion >= newTM()) {
            // Unlikely to happen

            wrapped = true;

         } else {
            // Else.. no worry... we will just accept the new time portion being added
            // This time-mark would have been generated some time ago, so this is ok.
            // tmMark is just a cache to validate the MaxIDs, so there is no need to make it atomic (synchronized)
            tmMark = timePortion;
         }
      }

      if (wrapped) {
         // This will only happen if a computer can generate more than ID_MASK ids (16 million IDs per 16
         // milliseconds)
         // If this wrapping code starts to happen, it needs revision
         throw new IllegalStateException("The IDGenerator is being overlapped, and it needs revision as the system generated more than " + TimeAndCounterIDGenerator.ID_MASK +
                                            " ids per 16 milliseconds which exceeded the IDgenerator limit");
      }

      return idReturn;
   }

   @Override
   public long getCurrentID() {
      return counter.get();
   }

   // for use in testcases
   public long getInternalTimeMark() {
      return tmMark;
   }

   // for use in testcases
   public void setInternalID(final long id) {
      counter.set(tmMark | id);
   }

   // for use in testcases
   public void setInternalDate(final long date) {
      tmMark = (date & TimeAndCounterIDGenerator.MASK_TIME) << TimeAndCounterIDGenerator.BITS_TO_MOVE;
      counter.set(tmMark);
   }

   public synchronized void refresh() {
      long oldTm = tmMark;
      long newTm = newTM();

      while (newTm <= oldTm) {
         newTm = newTM();
      }
      tmMark = newTm;
      counter.set(tmMark);
   }

   @Override
   public String toString() {
      long currentCounter = counter.get();
      return "SequenceGenerator(tmMark=" + hex(tmMark) +
         ", CurrentCounter = " +
         currentCounter +
         ", HexCurrentCounter = " +
         hex(currentCounter) +
         ")";
   }

   private long newTM() {
      return (System.currentTimeMillis() & TimeAndCounterIDGenerator.MASK_TIME) << TimeAndCounterIDGenerator.BITS_TO_MOVE;
   }

   private String hex(final long x) {
      return String.format("%1$X", x);
   }

}