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   /*
    * Licensed 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 io.netty.util.internal.shaded.org.jctools.queues;
  
  import io.netty.util.internal.shaded.org.jctools.util.InternalAPI;
  
  @InternalAPI
  public final class IndexedQueueSizeUtil
  {
      public static int size(IndexedQueue iq)
      {
          /*
           * It is possible for a thread to be interrupted or reschedule between the read of the producer and
           * consumer indices, therefore protection is required to ensure size is within valid range. In the
           * event of concurrent polls/offers to this method the size is OVER estimated as we read consumer
           * index BEFORE the producer index.
           */
          long after = iq.lvConsumerIndex();
          long size;
          while (true)
          {
              final long before = after;
              final long currentProducerIndex = iq.lvProducerIndex();
              after = iq.lvConsumerIndex();
              if (before == after)
              {
                  size = (currentProducerIndex - after);
                  break;
              }
          }
          // Long overflow is impossible (), so size is always positive. Integer overflow is possible for the unbounded
          // indexed queues.
          if (size > Integer.MAX_VALUE)
          {
              return Integer.MAX_VALUE;
          }
          else
          {
              return (int) size;
          }
      }
  
      public static boolean isEmpty(IndexedQueue iq)
      {
          // Order matters!
          // Loading consumer before producer allows for producer increments after consumer index is read.
          // This ensures this method is conservative in it's estimate. Note that as this is an MPMC there is
          // nothing we can do to make this an exact method.
          return (iq.lvConsumerIndex() == iq.lvProducerIndex());
      }
  
      @InternalAPI
      public interface IndexedQueue
      {
          long lvConsumerIndex();
  
          long lvProducerIndex();
      }
  }