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 io.reactivex.rxjava3.annotations.Nullable;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.functions.Predicate;
  import io.reactivex.rxjava3.internal.observers.BasicFuseableObserver;
  
  public final class ObservableFilter<T> extends AbstractObservableWithUpstream<T, T> {
      final Predicate<? super T> predicate;
      public ObservableFilter(ObservableSource<T> source, Predicate<? super T> predicate) {
          super(source);
          this.predicate = predicate;
      }
  
      @Override
      public void subscribeActual(Observer<? super T> observer) {
          source.subscribe(new FilterObserver<>(observer, predicate));
      }
  
      static final class FilterObserver<T> extends BasicFuseableObserver<T, T> {
          final Predicate<? super T> filter;
  
          FilterObserver(Observer<? super T> actual, Predicate<? super T> filter) {
              super(actual);
              this.filter = filter;
          }
  
          @Override
          public void onNext(T t) {
              if (sourceMode == NONE) {
                  boolean b;
                  try {
                      b = filter.test(t);
                  } catch (Throwable e) {
                      fail(e);
                      return;
                  }
                  if (b) {
                      downstream.onNext(t);
                  }
              } else {
                  downstream.onNext(null);
              }
          }
  
          @Override
          public int requestFusion(int mode) {
              return transitiveBoundaryFusion(mode);
          }
  
          @Nullable
          @Override
          public T poll() throws Throwable {
              for (;;) {
                  T v = qd.poll();
                  if (v == null || filter.test(v)) {
                      return v;
                  }
              }
          }
      }
  }
  