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.operators.flowable;
  
  import java.util.Objects;
  import java.util.concurrent.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.internal.functions.*;
  import io.reactivex.rxjava3.internal.subscribers.*;
  import io.reactivex.rxjava3.internal.util.*;
  
  /**
   * Utility methods to consume a Publisher in a blocking manner with callbacks or Subscriber.
   */
  public final class FlowableBlockingSubscribe {
  
      /** Utility class. */
      private FlowableBlockingSubscribe() {
          throw new IllegalStateException("No instances!");
      }
  
      /**
       * Subscribes to the source and calls the Subscriber methods on the current thread.
       * <p>
       * @param source the source publisher
       * The cancellation and backpressure is composed through.
       * @param subscriber the subscriber to forward events and calls to in the current thread
       * @param <T> the value type
       */
      public static <T> void subscribe(Publisher<? extends T> source, Subscriber<? super T> subscriber) {
          final BlockingQueue<Object> queue = new LinkedBlockingQueue<>();
  
          BlockingSubscriber<T> bs = new BlockingSubscriber<>(queue);
  
          source.subscribe(bs);
  
          try {
              for (;;) {
                  if (bs.isCancelled()) {
                      break;
                  }
                  Object v = queue.poll();
                  if (v == null) {
                      if (bs.isCancelled()) {
                          break;
                      }
                      BlockingHelper.verifyNonBlocking();
                      v = queue.take();
                  }
                  if (bs.isCancelled()) {
                      break;
                  }
                  if (v == BlockingSubscriber.TERMINATED
                          || NotificationLite.acceptFull(v, subscriber)) {
                      break;
                  }
              }
          } catch (InterruptedException e) {
              bs.cancel();
              subscriber.onError(e);
          }
      }
  
      /**
       * Runs the source observable to a terminal event, ignoring any values and rethrowing any exception.
       * @param source the source to await
       * @param <T> the value type
       */
      public static <T> void subscribe(Publisher<? extends T> source) {
          BlockingIgnoringReceiver callback = new BlockingIgnoringReceiver();
          LambdaSubscriber<T> ls = new LambdaSubscriber<>(Functions.emptyConsumer(),
          callback, callback, Functions.REQUEST_MAX);
  
          source.subscribe(ls);
  
          BlockingHelper.awaitForComplete(callback, ls);
          Throwable e = callback.error;
          if (e != null) {
              throw ExceptionHelper.wrapOrThrow(e);
          }
      }
  
      /**
       * Subscribes to the source and calls the given actions on the current thread.
       * @param o the source publisher
       * @param onNext the callback action for each source value
       * @param onError the callback action for an error event
       * @param onComplete the callback action for the completion event.
       * @param <T> the value type
       */
      public static <T> void subscribe(Publisher<? extends T> o, final Consumer<? super T> onNext,
              final Consumer<? super Throwable> onError, final Action onComplete) {
          Objects.requireNonNull(onNext, "onNext is null");
          Objects.requireNonNull(onError, "onError is null");
          Objects.requireNonNull(onComplete, "onComplete is null");
          subscribe(o, new LambdaSubscriber<T>(onNext, onError, onComplete, Functions.REQUEST_MAX));
      }
  
      /**
       * Subscribes to the source and calls the given actions on the current thread.
       * @param o the source publisher
       * @param onNext the callback action for each source value
       * @param onError the callback action for an error event
       * @param onComplete the callback action for the completion event.
       * @param bufferSize the number of elements to prefetch from the source Publisher
       * @param <T> the value type
       */
      public static <T> void subscribe(Publisher<? extends T> o, final Consumer<? super T> onNext,
          final Consumer<? super Throwable> onError, final Action onComplete, int bufferSize) {
          Objects.requireNonNull(onNext, "onNext is null");
          Objects.requireNonNull(onError, "onError is null");
          Objects.requireNonNull(onComplete, "onComplete is null");
          ObjectHelper.verifyPositive(bufferSize, "number > 0 required");
          subscribe(o, new BoundedSubscriber<T>(onNext, onError, onComplete, Functions.boundedConsumer(bufferSize),
                  bufferSize));
      }
  }
  