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.internal.disposables.DisposableHelper;
  
  /**
   * Makes sure a dispose() call from downstream happens on the specified scheduler.
   * 
   * @param <T> the value type
   */
  public final class SingleUnsubscribeOn<T> extends Single<T> {
  
      final SingleSource<T> source;
  
      final Scheduler scheduler;
  
      public SingleUnsubscribeOn(SingleSource<T> source, Scheduler scheduler) {
          this.source = source;
          this.scheduler = scheduler;
      }
  
      @Override
      protected void subscribeActual(SingleObserver<? super T> observer) {
          source.subscribe(new UnsubscribeOnSingleObserver<>(observer, scheduler));
      }
  
      static final class UnsubscribeOnSingleObserver<T> extends AtomicReference<Disposable>
      implements SingleObserver<T>, Disposable, Runnable {
  
          private static final long serialVersionUID = 3256698449646456986L;
  
          final SingleObserver<? super T> downstream;
  
          final Scheduler scheduler;
  
          Disposable ds;
  
          UnsubscribeOnSingleObserver(SingleObserver<? super T> actual, Scheduler scheduler) {
              this.downstream = actual;
              this.scheduler = scheduler;
          }
  
          @Override
          public void dispose() {
              Disposable d = getAndSet(DisposableHelper.DISPOSED);
              if (d != DisposableHelper.DISPOSED) {
                  this.ds = d;
                  scheduler.scheduleDirect(this);
              }
          }
  
          @Override
          public void run() {
              ds.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return DisposableHelper.isDisposed(get());
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.setOnce(this, d)) {
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onSuccess(T value) {
              downstream.onSuccess(value);
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
      }
  }
  