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.single;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Action;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  public final class SingleDoOnDispose<T> extends Single<T> {
      final SingleSource<T> source;
  
      final Action onDispose;
  
      public SingleDoOnDispose(SingleSource<T> source, Action onDispose) {
          this.source = source;
          this.onDispose = onDispose;
      }
  
      @Override
      protected void subscribeActual(final SingleObserver<? super T> observer) {
  
          source.subscribe(new DoOnDisposeObserver<>(observer, onDispose));
      }
  
      static final class DoOnDisposeObserver<T>
      extends AtomicReference<Action>
      implements SingleObserver<T>, Disposable {
          private static final long serialVersionUID = -8583764624474935784L;
  
          final SingleObserver<? super T> downstream;
  
          Disposable upstream;
  
          DoOnDisposeObserver(SingleObserver<? super T> actual, Action onDispose) {
              this.downstream = actual;
              this.lazySet(onDispose);
          }
  
          @Override
          public void dispose() {
              Action a = getAndSet(null);
              if (a != null) {
                  try {
                      a.run();
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      RxJavaPlugins.onError(ex);
                  }
                  upstream.dispose();
              }
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onSuccess(T value) {
              downstream.onSuccess(value);
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
      }
  
  }
  