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 io.reactivex.rxjava3.core.Flowable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Consumer;
  import org.reactivestreams.Subscriber;
  
  public final class FlowableOnBackpressureLatest<T> extends AbstractFlowableWithUpstream<T, T> {
  
      final Consumer<? super T> onDropped;
  
      public FlowableOnBackpressureLatest(Flowable<T> source, Consumer<? super T> onDropped) {
          super(source);
          this.onDropped = onDropped;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> s) {
          source.subscribe(new BackpressureLatestSubscriber<>(s, onDropped));
      }
  
      static final class BackpressureLatestSubscriber<T> extends AbstractBackpressureThrottlingSubscriber<T, T> {
  
          private static final long serialVersionUID = 163080509307634843L;
  
          final Consumer<? super T> onDropped;
  
          BackpressureLatestSubscriber(Subscriber<? super T> downstream,
                                       Consumer<? super T> onDropped) {
              super(downstream);
              this.onDropped = onDropped;
          }
  
          @Override
          public void onNext(T t) {
              T oldValue = current.getAndSet(t);
              if (onDropped != null && oldValue != null) {
                  try {
                      onDropped.accept(oldValue);
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      upstream.cancel();
                      downstream.onError(ex);
                  }
              }
              drain();
          }
      }
  }
  