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.observable;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.core.Scheduler.Worker;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.internal.schedulers.TrampolineScheduler;
  
  public final class ObservableInterval extends Observable<Long> {
      final Scheduler scheduler;
      final long initialDelay;
      final long period;
      final TimeUnit unit;
  
      public ObservableInterval(long initialDelay, long period, TimeUnit unit, Scheduler scheduler) {
          this.initialDelay = initialDelay;
          this.period = period;
          this.unit = unit;
          this.scheduler = scheduler;
      }
  
      @Override
      public void subscribeActual(Observer<? super Long> observer) {
          IntervalObserver is = new IntervalObserver(observer);
          observer.onSubscribe(is);
  
          Scheduler sch = scheduler;
  
          if (sch instanceof TrampolineScheduler) {
              Worker worker = sch.createWorker();
              is.setResource(worker);
              worker.schedulePeriodically(is, initialDelay, period, unit);
          } else {
              Disposable d = sch.schedulePeriodicallyDirect(is, initialDelay, period, unit);
              is.setResource(d);
          }
      }
  
      static final class IntervalObserver
      extends AtomicReference<Disposable>
      implements Disposable, Runnable {
  
          private static final long serialVersionUID = 346773832286157679L;
  
          final Observer<? super Long> downstream;
  
          long count;
  
          IntervalObserver(Observer<? super Long> downstream) {
              this.downstream = downstream;
          }
  
          @Override
          public void dispose() {
              DisposableHelper.dispose(this);
          }
  
          @Override
          public boolean isDisposed() {
              return get() == DisposableHelper.DISPOSED;
          }
  
          @Override
          public void run() {
              if (get() != DisposableHelper.DISPOSED) {
                  downstream.onNext(count++);
              }
          }
  
          public void setResource(Disposable d) {
              DisposableHelper.setOnce(this, d);
          }
      }
  }
  