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.tck;
  
  import java.util.concurrent.atomic.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.FlowableSubscriber;
  import io.reactivex.rxjava3.internal.subscriptions.*;
  import io.reactivex.rxjava3.processors.FlowableProcessor;
  
  /**
   * A FlowableProcessor wrapper that disposes the Subscription set via
   * onSubscribe if the number of subscribers reaches zero.
   *
   * @param <T> the upstream and downstream value type
   * @since 2.1.8
   */
  /* public */final class RefCountProcessor<T> extends FlowableProcessor<T> implements Subscription {
  
      final FlowableProcessor<T> actual;
  
      final AtomicReference<Subscription> upstream;
  
      final AtomicReference<RefCountSubscriber<T>[]> subscribers;
  
      @SuppressWarnings("rawtypes")
      static final RefCountSubscriber[] EMPTY = new RefCountSubscriber[0];
  
      @SuppressWarnings("rawtypes")
      static final RefCountSubscriber[] TERMINATED = new RefCountSubscriber[0];
  
      @SuppressWarnings("unchecked")
      RefCountProcessor(FlowableProcessor<T> actual) {
          this.actual = actual;
          this.upstream = new AtomicReference<>();
          this.subscribers = new AtomicReference<>(EMPTY);
      }
  
      @Override
      public void onSubscribe(Subscription s) {
          if (SubscriptionHelper.setOnce(upstream, s)) {
              actual.onSubscribe(this);
          }
      }
  
      @Override
      public void onNext(T t) {
          actual.onNext(t);
      }
  
      @Override
      public void onError(Throwable t) {
          upstream.lazySet(SubscriptionHelper.CANCELLED);
          actual.onError(t);
      }
  
      @Override
      public void onComplete() {
          upstream.lazySet(SubscriptionHelper.CANCELLED);
          actual.onComplete();
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> s) {
          RefCountSubscriber<T> rcs = new RefCountSubscriber<>(s, this);
          if (!add(rcs)) {
              EmptySubscription.error(new IllegalStateException("RefCountProcessor terminated"), s);
              return;
          }
          actual.subscribe(rcs);
      }
  
      @Override
      public boolean hasComplete() {
          return actual.hasComplete();
      }
  
      @Override
      public boolean hasThrowable() {
          return actual.hasThrowable();
      }
  
      @Override
      public Throwable getThrowable() {
          return actual.getThrowable();
      }
  
      @Override
      public boolean hasSubscribers() {
          return actual.hasSubscribers();
      }
  
      @Override
      public void cancel() {
          SubscriptionHelper.cancel(upstream);
      }
  
      @Override
      public void request(long n) {
          upstream.get().request(n);
      }
  
      boolean add(RefCountSubscriber<T> rcs) {
          for (;;) {
              RefCountSubscriber<T>[] a = subscribers.get();
              if (a == TERMINATED) {
                  return false;
              }
              int n = a.length;
              @SuppressWarnings("unchecked")
              RefCountSubscriber<T>[] b = new RefCountSubscriber[n + 1];
              System.arraycopy(a, 0, b, 0, n);
              b[n] = rcs;
              if (subscribers.compareAndSet(a, b)) {
                  return true;
              }
          }
      }
  
      @SuppressWarnings("unchecked")
      void remove(RefCountSubscriber<T> rcs) {
          for (;;) {
              RefCountSubscriber<T>[] a = subscribers.get();
              int n = a.length;
              if (n == 0) {
                  break;
              }
              int j = -1;
  
              for (int i = 0; i < n; i++) {
                  if (rcs == a[i]) {
                      j = i;
                      break;
                  }
              }
  
              if (j < 0) {
                  break;
              }
  
              RefCountSubscriber<T>[] b;
              if (n == 1) {
                  b = TERMINATED;
              } else {
                  b = new RefCountSubscriber[n - 1];
                  System.arraycopy(a, 0, b, 0, j);
                  System.arraycopy(a, j + 1, b, j, n - j - 1);
              }
              if (subscribers.compareAndSet(a, b)) {
                  if (b == TERMINATED) {
                      cancel();
                  }
                  break;
              }
          }
      }
  
      static final class RefCountSubscriber<T> extends AtomicBoolean implements FlowableSubscriber<T>, Subscription {
  
          private static final long serialVersionUID = -4317488092687530631L;
  
          final Subscriber<? super T> downstream;
  
          final RefCountProcessor<T> parent;
  
          Subscription upstream;
  
          RefCountSubscriber(Subscriber<? super T> actual, RefCountProcessor<T> parent) {
              this.downstream = actual;
              this.parent = parent;
          }
  
          @Override
          public void request(long n) {
              upstream.request(n);
          }
  
          @Override
          public void cancel() {
              lazySet(true);
              upstream.cancel();
              parent.remove(this);
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              this.upstream = s;
              downstream.onSubscribe(this);
          }
  
          @Override
          public void onNext(T t) {
              downstream.onNext(t);
          }
  
          @Override
          public void onError(Throwable t) {
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              downstream.onComplete();
          }
      }
  }
  