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.Arrays;
  import java.util.Objects;
  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.functions.Function;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.operators.SpscLinkedArrayQueue;
  
  public final class ObservableZip<T, R> extends Observable<R> {
  
      final ObservableSource<? extends T>[] sources;
      final Iterable<? extends ObservableSource<? extends T>> sourcesIterable;
      final Function<? super Object[], ? extends R> zipper;
      final int bufferSize;
      final boolean delayError;
  
      public ObservableZip(ObservableSource<? extends T>[] sources,
              Iterable<? extends ObservableSource<? extends T>> sourcesIterable,
              Function<? super Object[], ? extends R> zipper,
              int bufferSize,
              boolean delayError) {
          this.sources = sources;
          this.sourcesIterable = sourcesIterable;
          this.zipper = zipper;
          this.bufferSize = bufferSize;
          this.delayError = delayError;
      }
  
      @Override
      @SuppressWarnings("unchecked")
      public void subscribeActual(Observer<? super R> observer) {
          ObservableSource<? extends T>[] sources = this.sources;
          int count = 0;
          if (sources == null) {
              sources = new ObservableSource[8];
              for (ObservableSource<? extends T> p : sourcesIterable) {
                  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;
              }
          } else {
              count = sources.length;
          }
  
          if (count == 0) {
              EmptyDisposable.complete(observer);
              return;
          }
  
          ZipCoordinator<T, R> zc = new ZipCoordinator<>(observer, zipper, count, delayError);
          zc.subscribe(sources, bufferSize);
      }
  
      static final class ZipCoordinator<T, R> extends AtomicInteger implements Disposable {
  
          private static final long serialVersionUID = 2983708048395377667L;
          final Observer<? super R> downstream;
          final Function<? super Object[], ? extends R> zipper;
          final ZipObserver<T, R>[] observers;
          final T[] row;
          final boolean delayError;
  
          volatile boolean cancelled;
  
          @SuppressWarnings("unchecked")
          ZipCoordinator(Observer<? super R> actual,
                  Function<? super Object[], ? extends R> zipper,
                  int count, boolean delayError) {
              this.downstream = actual;
              this.zipper = zipper;
              this.observers = new ZipObserver[count];
              this.row = (T[])new Object[count];
              this.delayError = delayError;
          }
  
          public void subscribe(ObservableSource<? extends T>[] sources, int bufferSize) {
              ZipObserver<T, R>[] s = observers;
              int len = s.length;
              for (int i = 0; i < len; i++) {
                  s[i] = new ZipObserver<>(this, bufferSize);
              }
              // this makes sure the contents of the observers array is visible
              this.lazySet(0);
              downstream.onSubscribe(this);
              for (int i = 0; i < len; i++) {
                  if (cancelled) {
                      return;
                  }
                  sources[i].subscribe(s[i]);
              }
          }
  
          @Override
          public void dispose() {
              if (!cancelled) {
                  cancelled = true;
                  cancelSources();
                  if (getAndIncrement() == 0) {
                      clear();
                  }
              }
          }
  
          @Override
          public boolean isDisposed() {
              return cancelled;
          }
  
          void cancel() {
              clear();
              cancelSources();
          }
  
          void cancelSources() {
              for (ZipObserver<?, ?> zs : observers) {
                  zs.dispose();
              }
          }
  
          void clear() {
              for (ZipObserver<?, ?> zs : observers) {
                  zs.queue.clear();
              }
          }
  
          public void drain() {
              if (getAndIncrement() != 0) {
                  return;
              }
  
              int missing = 1;
  
              final ZipObserver<T, R>[] zs = observers;
              final Observer<? super R> a = downstream;
              final T[] os = row;
              final boolean delayError = this.delayError;
  
              for (;;) {
  
                  for (;;) {
                      int i = 0;
                      int emptyCount = 0;
                      for (ZipObserver<T, R> z : zs) {
                          if (os[i] == null) {
                              boolean d = z.done;
                              T v = z.queue.poll();
                              boolean empty = v == null;
  
                              if (checkTerminated(d, empty, a, delayError, z)) {
                                  return;
                              }
                              if (!empty) {
                                  os[i] = v;
                              } else {
                                  emptyCount++;
                              }
                          } else {
                              if (z.done && !delayError) {
                                  Throwable ex = z.error;
                                  if (ex != null) {
                                      cancelled = true;
                                      cancel();
                                      a.onError(ex);
                                      return;
                                  }
                              }
                          }
                          i++;
                      }
  
                      if (emptyCount != 0) {
                          break;
                      }
  
                      R v;
                      try {
                          v = Objects.requireNonNull(zipper.apply(os.clone()), "The zipper returned a null value");
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          cancel();
                          a.onError(ex);
                          return;
                      }
  
                      a.onNext(v);
  
                      Arrays.fill(os, null);
                  }
  
                  missing = addAndGet(-missing);
                  if (missing == 0) {
                      return;
                  }
              }
          }
  
          boolean checkTerminated(boolean d, boolean empty, Observer<? super R> a, boolean delayError, ZipObserver<?, ?> source) {
              if (cancelled) {
                  cancel();
                  return true;
              }
  
              if (d) {
                  if (delayError) {
                      if (empty) {
                          Throwable e = source.error;
                          cancelled = true;
                          cancel();
                          if (e != null) {
                              a.onError(e);
                          } else {
                              a.onComplete();
                          }
                          return true;
                      }
                  } else {
                      Throwable e = source.error;
                      if (e != null) {
                          cancelled = true;
                          cancel();
                          a.onError(e);
                          return true;
                      } else
                      if (empty) {
                          cancelled = true;
                          cancel();
                          a.onComplete();
                          return true;
                      }
                  }
              }
  
              return false;
          }
      }
  
      static final class ZipObserver<T, R> implements Observer<T> {
  
          final ZipCoordinator<T, R> parent;
          final SpscLinkedArrayQueue<T> queue;
  
          volatile boolean done;
          Throwable error;
  
          final AtomicReference<Disposable> upstream = new AtomicReference<>();
  
          ZipObserver(ZipCoordinator<T, R> parent, int bufferSize) {
              this.parent = parent;
              this.queue = new SpscLinkedArrayQueue<>(bufferSize);
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              DisposableHelper.setOnce(this.upstream, d);
          }
  
          @Override
          public void onNext(T t) {
              queue.offer(t);
              parent.drain();
          }
  
          @Override
          public void onError(Throwable t) {
              error = t;
              done = true;
              parent.drain();
          }
  
          @Override
          public void onComplete() {
              done = true;
              parent.drain();
          }
  
          public void dispose() {
              DisposableHelper.dispose(upstream);
          }
      }
  }
  