code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * 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.reactivex.rxjava3.internal.subscribers;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.reactivestreams.Subscription;
  
  import io.reactivex.rxjava3.core.FlowableSubscriber;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.rxjava3.internal.util.QueueDrainHelper;
  import io.reactivex.rxjava3.operators.QueueSubscription;
  import io.reactivex.rxjava3.operators.SimpleQueue;
  
  /**
   * Subscriber that can fuse with the upstream and calls a support interface
   * whenever an event is available.
   *
   * @param <T> the value type
   */
  public final class InnerQueuedSubscriber<T>
  extends AtomicReference<Subscription>
  implements FlowableSubscriber<T>, Subscription {
  
      private static final long serialVersionUID = 22876611072430776L;
  
      final InnerQueuedSubscriberSupport<T> parent;
  
      final int prefetch;
  
      final int limit;
  
      volatile SimpleQueue<T> queue;
  
      volatile boolean done;
  
      long produced;
  
      int fusionMode;
  
      public InnerQueuedSubscriber(InnerQueuedSubscriberSupport<T> parent, int prefetch) {
          this.parent = parent;
          this.prefetch = prefetch;
          this.limit = prefetch - (prefetch >> 2);
      }
  
      @Override
      public void onSubscribe(Subscription s) {
          if (SubscriptionHelper.setOnce(this, s)) {
              if (s instanceof QueueSubscription) {
                  @SuppressWarnings("unchecked")
                  QueueSubscription<T> qs = (QueueSubscription<T>) s;
  
                  int m = qs.requestFusion(QueueSubscription.ANY);
                  if (m == QueueSubscription.SYNC) {
                      fusionMode = m;
                      queue = qs;
                      done = true;
                      parent.innerComplete(this);
                      return;
                  }
                  if (m == QueueSubscription.ASYNC) {
                      fusionMode = m;
                      queue = qs;
                      QueueDrainHelper.request(s, prefetch);
                      return;
                  }
              }
  
              queue = QueueDrainHelper.createQueue(prefetch);
  
              QueueDrainHelper.request(s, prefetch);
          }
      }
  
      @Override
      public void onNext(T t) {
          if (fusionMode == QueueSubscription.NONE) {
              parent.innerNext(this, t);
          } else {
              parent.drain();
          }
      }
  
      @Override
      public void onError(Throwable t) {
          parent.innerError(this, t);
      }
  
      @Override
      public void onComplete() {
          parent.innerComplete(this);
      }
  
      @Override
      public void request(long n) {
          if (fusionMode != QueueSubscription.SYNC) {
              long p = produced + n;
              if (p >= limit) {
                  produced = 0L;
                  get().request(p);
              } else {
                  produced = p;
              }
          }
      }
  
      @Override
      public void cancel() {
          SubscriptionHelper.cancel(this);
      }
  
      public boolean isDone() {
          return done;
      }
  
      public void setDone() {
          this.done = true;
      }
  
      public SimpleQueue<T> queue() {
          return queue;
      }
  }
  