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 java.util.Iterator;
  import java.util.Objects;
  
  import org.reactivestreams.Subscriber;
  
  import io.reactivex.rxjava3.annotations.Nullable;
  import io.reactivex.rxjava3.core.Flowable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.subscriptions.*;
  import io.reactivex.rxjava3.internal.util.BackpressureHelper;
  import io.reactivex.rxjava3.operators.ConditionalSubscriber;
  
  public final class FlowableFromIterable<T> extends Flowable<T> {
  
      final Iterable<? extends T> source;
  
      public FlowableFromIterable(Iterable<? extends T> source) {
          this.source = source;
      }
  
      @Override
      public void subscribeActual(Subscriber<? super T> s) {
          Iterator<? extends T> it;
          try {
              it = source.iterator();
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              EmptySubscription.error(e, s);
              return;
          }
  
          subscribe(s, it);
      }
  
      public static <T> void subscribe(Subscriber<? super T> s, Iterator<? extends T> it) {
          boolean hasNext;
          try {
              hasNext = it.hasNext();
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              EmptySubscription.error(e, s);
              return;
          }
  
          if (!hasNext) {
              EmptySubscription.complete(s);
              return;
          }
  
          if (s instanceof ConditionalSubscriber) {
              s.onSubscribe(new IteratorConditionalSubscription<T>(
                      (ConditionalSubscriber<? super T>)s, it));
          } else {
              s.onSubscribe(new IteratorSubscription<T>(s, it));
          }
      }
  
      abstract static class BaseRangeSubscription<T> extends BasicQueueSubscription<T> {
          private static final long serialVersionUID = -2252972430506210021L;
  
          Iterator<? extends T> iterator;
  
          volatile boolean cancelled;
  
          boolean once;
  
          BaseRangeSubscription(Iterator<? extends T> it) {
              this.iterator = it;
          }
  
          @Override
          public final int requestFusion(int mode) {
              return mode & SYNC;
          }
  
          @Nullable
          @Override
          public final T poll() {
              if (iterator == null) {
                  return null;
              }
              if (!once) {
                  once = true;
              } else {
                  if (!iterator.hasNext()) {
                      return null;
                  }
              }
              return Objects.requireNonNull(iterator.next(), "Iterator.next() returned a null value");
          }
  
          @Override
          public final boolean isEmpty() {
              Iterator<? extends T> it = this.iterator;
              if (it != null) {
                  if (!once || it.hasNext()) {
                      return false;
                  }
                  clear();
              }
              return true;
          }
  
          @Override
          public final void clear() {
              iterator = null;
          }
  
          @Override
          public final void request(long n) {
              if (SubscriptionHelper.validate(n)) {
                  if (BackpressureHelper.add(this, n) == 0L) {
                      if (n == Long.MAX_VALUE) {
                          fastPath();
                      } else {
                          slowPath(n);
                      }
                  }
              }
          }
  
          @Override
          public final void cancel() {
              cancelled = true;
          }
  
          abstract void fastPath();
  
          abstract void slowPath(long r);
      }
  
      static final class IteratorSubscription<T> extends BaseRangeSubscription<T> {
  
          private static final long serialVersionUID = -6022804456014692607L;
  
          final Subscriber<? super T> downstream;
  
          IteratorSubscription(Subscriber<? super T> actual, Iterator<? extends T> it) {
              super(it);
              this.downstream = actual;
          }
  
          @Override
          void fastPath() {
              Iterator<? extends T> it = this.iterator;
              Subscriber<? super T> a = downstream;
              for (;;) {
                  if (cancelled) {
                      return;
                  }
  
                  T t;
  
                  try {
                      t = it.next();
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      a.onError(ex);
                      return;
                  }
  
                  if (cancelled) {
                      return;
                  }
  
                  if (t == null) {
                      a.onError(new NullPointerException("Iterator.next() returned a null value"));
                      return;
                  } else {
                      a.onNext(t);
                  }
  
                  if (cancelled) {
                      return;
                  }
  
                  boolean b;
  
                  try {
                      b = it.hasNext();
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      a.onError(ex);
                      return;
                  }
  
                  if (!b) {
                      if (!cancelled) {
                          a.onComplete();
                      }
                      return;
                  }
              }
          }
  
          @Override
          void slowPath(long r) {
              long e = 0L;
              Iterator<? extends T> it = this.iterator;
              Subscriber<? super T> a = downstream;
  
              for (;;) {
  
                  while (e != r) {
  
                      if (cancelled) {
                          return;
                      }
  
                      T t;
  
                      try {
                          t = it.next();
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          a.onError(ex);
                          return;
                      }
  
                      if (cancelled) {
                          return;
                      }
  
                      if (t == null) {
                          a.onError(new NullPointerException("Iterator.next() returned a null value"));
                          return;
                      } else {
                          a.onNext(t);
                      }
  
                      if (cancelled) {
                          return;
                      }
  
                      boolean b;
  
                      try {
                          b = it.hasNext();
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          a.onError(ex);
                          return;
                      }
  
                      if (!b) {
                          if (!cancelled) {
                              a.onComplete();
                          }
                          return;
                      }
  
                      e++;
                  }
  
                  r = get();
                  if (e == r) {
                      r = addAndGet(-e);
                      if (r == 0L) {
                          return;
                      }
                      e = 0L;
                  }
              }
          }
  
      }
  
      static final class IteratorConditionalSubscription<T> extends BaseRangeSubscription<T> {
  
          private static final long serialVersionUID = -6022804456014692607L;
  
          final ConditionalSubscriber<? super T> downstream;
  
          IteratorConditionalSubscription(ConditionalSubscriber<? super T> actual, Iterator<? extends T> it) {
              super(it);
              this.downstream = actual;
          }
  
          @Override
          void fastPath() {
              Iterator<? extends T> it = this.iterator;
              ConditionalSubscriber<? super T> a = downstream;
              for (;;) {
                  if (cancelled) {
                      return;
                  }
  
                  T t;
  
                  try {
                      t = it.next();
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      a.onError(ex);
                      return;
                  }
  
                  if (cancelled) {
                      return;
                  }
  
                  if (t == null) {
                      a.onError(new NullPointerException("Iterator.next() returned a null value"));
                      return;
                  } else {
                      a.tryOnNext(t);
                  }
  
                  if (cancelled) {
                      return;
                  }
  
                  boolean b;
  
                  try {
                      b = it.hasNext();
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      a.onError(ex);
                      return;
                  }
  
                  if (!b) {
                      if (!cancelled) {
                          a.onComplete();
                      }
                      return;
                  }
              }
          }
  
          @Override
          void slowPath(long r) {
              long e = 0L;
              Iterator<? extends T> it = this.iterator;
              ConditionalSubscriber<? super T> a = downstream;
  
              for (;;) {
  
                  while (e != r) {
  
                      if (cancelled) {
                          return;
                      }
  
                      T t;
  
                      try {
                          t = it.next();
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          a.onError(ex);
                          return;
                      }
  
                      if (cancelled) {
                          return;
                      }
  
                      boolean b;
                      if (t == null) {
                          a.onError(new NullPointerException("Iterator.next() returned a null value"));
                          return;
                      } else {
                          b = a.tryOnNext(t);
                      }
  
                      if (cancelled) {
                          return;
                      }
  
                      boolean hasNext;
  
                      try {
                          hasNext = it.hasNext();
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          a.onError(ex);
                          return;
                      }
  
                      if (!hasNext) {
                          if (!cancelled) {
                              a.onComplete();
                          }
                          return;
                      }
  
                      if (b) {
                          e++;
                      }
                  }
  
                  r = get();
                  if (e == r) {
                      r = addAndGet(-e);
                      if (r == 0L) {
                          return;
                      }
                      e = 0L;
                  }
              }
          }
  
      }
  }
  