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.Iterator;
  import java.util.Objects;
  
  import io.reactivex.rxjava3.annotations.Nullable;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.disposables.EmptyDisposable;
  import io.reactivex.rxjava3.internal.observers.BasicQueueDisposable;
  
  public final class ObservableFromIterable<T> extends Observable<T> {
      final Iterable<? extends T> source;
      public ObservableFromIterable(Iterable<? extends T> source) {
          this.source = source;
      }
  
      @Override
      public void subscribeActual(Observer<? super T> observer) {
          Iterator<? extends T> it;
          try {
              it = source.iterator();
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              EmptyDisposable.error(e, observer);
              return;
          }
          boolean hasNext;
          try {
              hasNext = it.hasNext();
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              EmptyDisposable.error(e, observer);
              return;
          }
          if (!hasNext) {
              EmptyDisposable.complete(observer);
              return;
          }
  
          FromIterableDisposable<T> d = new FromIterableDisposable<>(observer, it);
          observer.onSubscribe(d);
  
          if (!d.fusionMode) {
              d.run();
          }
      }
  
      static final class FromIterableDisposable<T> extends BasicQueueDisposable<T> {
  
          final Observer<? super T> downstream;
  
          final Iterator<? extends T> it;
  
          volatile boolean disposed;
  
          boolean fusionMode;
  
          boolean done;
  
          boolean checkNext;
  
          FromIterableDisposable(Observer<? super T> actual, Iterator<? extends T> it) {
              this.downstream = actual;
              this.it = it;
          }
  
          void run() {
              boolean hasNext;
  
              do {
                  if (isDisposed()) {
                      return;
                  }
                  T v;
  
                  try {
                      v = Objects.requireNonNull(it.next(), "The iterator returned a null value");
                  } catch (Throwable e) {
                      Exceptions.throwIfFatal(e);
                      downstream.onError(e);
                      return;
                  }
  
                  downstream.onNext(v);
  
                  if (isDisposed()) {
                      return;
                  }
                  try {
                      hasNext = it.hasNext();
                  } catch (Throwable e) {
                      Exceptions.throwIfFatal(e);
                      downstream.onError(e);
                      return;
                  }
              } while (hasNext);
  
              if (!isDisposed()) {
                  downstream.onComplete();
              }
          }
  
          @Override
          public int requestFusion(int mode) {
              if ((mode & SYNC) != 0) {
                  fusionMode = true;
                  return SYNC;
              }
              return NONE;
          }
  
          @Nullable
          @Override
          public T poll() {
              if (done) {
                  return null;
              }
              if (checkNext) {
                  if (!it.hasNext()) {
                      done = true;
                      return null;
                  }
              } else {
                  checkNext = true;
              }
  
              return Objects.requireNonNull(it.next(), "The iterator returned a null value");
          }
  
          @Override
          public boolean isEmpty() {
              return done;
          }
  
          @Override
          public void clear() {
              done = true;
          }
  
          @Override
          public void dispose() {
              disposed = true;
          }
  
          @Override
          public boolean isDisposed() {
              return disposed;
          }
      }
  }
  