code: /*
   * Copyright (c) 2019 the Eclipse Milo Authors
   *
   * This program and the accompanying materials are made
   * available under the terms of the Eclipse Public License 2.0
   * which is available at https://www.eclipse.org/legal/epl-2.0/
   *
   * SPDX-License-Identifier: EPL-2.0
   */
  
  package org.eclipse.milo.opcua.stack.core.util;
  
  import java.util.concurrent.atomic.AtomicLong;
  
  public class LongSequence {
  
      private final AtomicLong atomic;
  
      private final long low;
      private final long high;
  
      public LongSequence(long low, long high) {
          this.low = low;
          this.high = high;
  
          atomic = new AtomicLong(low);
      }
  
      /**
       * @return the current value in the sequence, followed by an increment.
       */
      public long getAndIncrement() {
          while (true) {
              long current = atomic.get();
              long next = (current >= high ? low : current + 1);
              if (atomic.compareAndSet(current, next)) {
                  return current;
              }
          }
      }
  
      /**
       * @return the current value in the sequence, without incrementing.
       */
      public long get() {
          return atomic.get();
      }
  
  }
  