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.atomic.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  public final class ObservableAmb<T> extends Observable<T> {
      final ObservableSource<? extends T>[] sources;
      final Iterable<? extends ObservableSource<? extends T>> sourcesIterable;
  
      public ObservableAmb(ObservableSource<? extends T>[] sources, Iterable<? extends ObservableSource<? extends T>> sourcesIterable) {
          this.sources = sources;
          this.sourcesIterable = sourcesIterable;
      }
  
      @Override
      @SuppressWarnings("unchecked")
      public void subscribeActual(Observer<? super T> observer) {
          ObservableSource<? extends T>[] sources = this.sources;
          int count = 0;
          if (sources == null) {
              sources = new ObservableSource[8];
              try {
                  for (ObservableSource<? extends T> p : sourcesIterable) {
                      if (p == null) {
                          EmptyDisposable.error(new NullPointerException("One of the sources is null"), observer);
                          return;
                      }
                      if (count == sources.length) {
                          ObservableSource<? extends T>[] b = new ObservableSource[count + (count >> 2)];
                          System.arraycopy(sources, 0, b, 0, count);
                          sources = b;
                      }
                      sources[count++] = p;
                  }
              } catch (Throwable e) {
                  Exceptions.throwIfFatal(e);
                  EmptyDisposable.error(e, observer);
                  return;
              }
          } else {
              count = sources.length;
          }
  
          if (count == 0) {
              EmptyDisposable.complete(observer);
              return;
          } else
          if (count == 1) {
              sources[0].subscribe(observer);
              return;
          }
  
          AmbCoordinator<T> ac = new AmbCoordinator<>(observer, count);
          ac.subscribe(sources);
      }
  
      static final class AmbCoordinator<T> implements Disposable {
          final Observer<? super T> downstream;
          final AmbInnerObserver<T>[] observers;
  
          final AtomicInteger winner = new AtomicInteger();
  
          @SuppressWarnings("unchecked")
          AmbCoordinator(Observer<? super T> actual, int count) {
              this.downstream = actual;
              this.observers = new AmbInnerObserver[count];
          }
  
          public void subscribe(ObservableSource<? extends T>[] sources) {
              AmbInnerObserver<T>[] as = observers;
              int len = as.length;
              for (int i = 0; i < len; i++) {
                  as[i] = new AmbInnerObserver<>(this, i + 1, downstream);
              }
              winner.lazySet(0); // release the contents of 'as'
              downstream.onSubscribe(this);
  
              for (int i = 0; i < len; i++) {
                  if (winner.get() != 0) {
                      return;
                  }
  
                  sources[i].subscribe(as[i]);
              }
          }
  
          public boolean win(int index) {
              int w = winner.get();
              if (w == 0) {
                  if (winner.compareAndSet(0, index)) {
                      AmbInnerObserver<T>[] a = observers;
                      int n = a.length;
                      for (int i = 0; i < n; i++) {
                          if (i + 1 != index) {
                              a[i].dispose();
                          }
                      }
                      return true;
                  }
              }
              return false;
          }
  
          @Override
          public void dispose() {
              if (winner.get() != -1) {
                  winner.lazySet(-1);
  
                  for (AmbInnerObserver<T> a : observers) {
                      a.dispose();
                  }
              }
          }
  
          @Override
          public boolean isDisposed() {
              return winner.get() == -1;
          }
      }
  
      static final class AmbInnerObserver<T> extends AtomicReference<Disposable> implements Observer<T> {
  
          private static final long serialVersionUID = -1185974347409665484L;
          final AmbCoordinator<T> parent;
          final int index;
          final Observer<? super T> downstream;
  
          boolean won;
  
          AmbInnerObserver(AmbCoordinator<T> parent, int index, Observer<? super T> downstream) {
              this.parent = parent;
              this.index = index;
              this.downstream = downstream;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              DisposableHelper.setOnce(this, d);
          }
  
          @Override
          public void onNext(T t) {
              if (won) {
                  downstream.onNext(t);
              } else {
                  if (parent.win(index)) {
                      won = true;
                      downstream.onNext(t);
                  } else {
                      get().dispose();
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (won) {
                  downstream.onError(t);
              } else {
                  if (parent.win(index)) {
                      won = true;
                      downstream.onError(t);
                  } else {
                      RxJavaPlugins.onError(t);
                  }
              }
          }
  
          @Override
          public void onComplete() {
              if (won) {
                  downstream.onComplete();
              } else {
                  if (parent.win(index)) {
                      won = true;
                      downstream.onComplete();
                  }
              }
          }
  
          public void dispose() {
              DisposableHelper.dispose(this);
          }
      }
  }
  