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 org.reactivestreams.Subscriber;
  
  import io.reactivex.rxjava3.annotations.Nullable;
  import io.reactivex.rxjava3.core.Flowable;
  import io.reactivex.rxjava3.internal.subscriptions.*;
  import io.reactivex.rxjava3.internal.util.BackpressureHelper;
  import io.reactivex.rxjava3.operators.ConditionalSubscriber;
  
  /**
   * Emits a range of integer values.
   */
  public final class FlowableRange extends Flowable<Integer> {
      final int start;
      final int end;
      public FlowableRange(int start, int count) {
          this.start = start;
          this.end = start + count;
      }
  
      @Override
      public void subscribeActual(Subscriber<? super Integer> s) {
          if (s instanceof ConditionalSubscriber) {
              s.onSubscribe(new RangeConditionalSubscription(
                      (ConditionalSubscriber<? super Integer>)s, start, end));
          } else {
              s.onSubscribe(new RangeSubscription(s, start, end));
          }
      }
  
      abstract static class BaseRangeSubscription extends BasicQueueSubscription<Integer> {
          private static final long serialVersionUID = -2252972430506210021L;
  
          final int end;
  
          int index;
  
          volatile boolean cancelled;
  
          BaseRangeSubscription(int index, int end) {
              this.index = index;
              this.end = end;
          }
  
          @Override
          public final int requestFusion(int mode) {
              return mode & SYNC;
          }
  
          @Nullable
          @Override
          public final Integer poll() {
              int i = index;
              if (i == end) {
                  return null;
              }
              index = i + 1;
              return i;
          }
  
          @Override
          public final boolean isEmpty() {
              return index == end;
          }
  
          @Override
          public final void clear() {
              index = end;
          }
  
          @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 RangeSubscription extends BaseRangeSubscription {
  
          private static final long serialVersionUID = 2587302975077663557L;
  
          final Subscriber<? super Integer> downstream;
  
          RangeSubscription(Subscriber<? super Integer> actual, int index, int end) {
              super(index, end);
              this.downstream = actual;
          }
  
          @Override
          void fastPath() {
              int f = end;
              Subscriber<? super Integer> a = downstream;
  
              for (int i = index; i != f; i++) {
                  if (cancelled) {
                      return;
                  }
                  a.onNext(i);
              }
              if (cancelled) {
                  return;
              }
              a.onComplete();
          }
  
          @Override
          void slowPath(long r) {
              long e = 0;
              int f = end;
              int i = index;
              Subscriber<? super Integer> a = downstream;
  
              for (;;) {
  
                  while (e != r && i != f) {
                      if (cancelled) {
                          return;
                      }
  
                      a.onNext(i);
  
                      e++;
                      i++;
                  }
  
                  if (i == f) {
                      if (!cancelled) {
                          a.onComplete();
                      }
                      return;
                  }
  
                  r = get();
                  if (e == r) {
                      index = i;
                      r = addAndGet(-e);
                      if (r == 0L) {
                          return;
                      }
                      e = 0L;
                  }
              }
          }
      }
  
      static final class RangeConditionalSubscription extends BaseRangeSubscription {
  
          private static final long serialVersionUID = 2587302975077663557L;
  
          final ConditionalSubscriber<? super Integer> downstream;
  
          RangeConditionalSubscription(ConditionalSubscriber<? super Integer> actual, int index, int end) {
              super(index, end);
              this.downstream = actual;
          }
  
          @Override
          void fastPath() {
              int f = end;
              ConditionalSubscriber<? super Integer> a = downstream;
  
              for (int i = index; i != f; i++) {
                  if (cancelled) {
                      return;
                  }
                  a.tryOnNext(i);
              }
              if (cancelled) {
                  return;
              }
              a.onComplete();
          }
  
          @Override
          void slowPath(long r) {
              long e = 0;
              int f = end;
              int i = index;
              ConditionalSubscriber<? super Integer> a = downstream;
  
              for (;;) {
  
                  while (e != r && i != f) {
                      if (cancelled) {
                          return;
                      }
  
                      if (a.tryOnNext(i)) {
                          e++;
                      }
  
                      i++;
                  }
  
                  if (i == f) {
                      if (!cancelled) {
                          a.onComplete();
                      }
                      return;
                  }
  
                  r = get();
                  if (e == r) {
                      index = i;
                      r = addAndGet(-e);
                      if (r == 0) {
                          return;
                      }
                      e = 0;
                  }
              }
          }
      }
  }
  