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.Queue;
  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.NotificationLite;
  
  public final class BlockingSubscriber<T> extends AtomicReference<Subscription> implements FlowableSubscriber<T>, Subscription {
  
      private static final long serialVersionUID = -4875965440900746268L;
  
      public static final Object TERMINATED = new Object();
  
      final Queue<Object> queue;
  
      public BlockingSubscriber(Queue<Object> queue) {
          this.queue = queue;
      }
  
      @Override
      public void onSubscribe(Subscription s) {
          if (SubscriptionHelper.setOnce(this, s)) {
              queue.offer(NotificationLite.subscription(this));
          }
      }
  
      @Override
      public void onNext(T t) {
          queue.offer(NotificationLite.next(t));
      }
  
      @Override
      public void onError(Throwable t) {
          queue.offer(NotificationLite.error(t));
      }
  
      @Override
      public void onComplete() {
          queue.offer(NotificationLite.complete());
      }
  
      @Override
      public void request(long n) {
          get().request(n);
      }
  
      @Override
      public void cancel() {
          if (SubscriptionHelper.cancel(this)) {
              queue.offer(TERMINATED);
          }
      }
  
      public boolean isCancelled() {
          return get() == SubscriptionHelper.CANCELLED;
      }
  }
  