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.concurrent.atomic.AtomicLong;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.internal.subscriptions.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  public final class FlowableTake<T> extends AbstractFlowableWithUpstream<T, T> {
  
      final long n;
  
      public FlowableTake(Flowable<T> source, long n) {
          super(source);
          this.n = n;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> s) {
          source.subscribe(new TakeSubscriber<>(s, n));
      }
  
      static final class TakeSubscriber<T>
      extends AtomicLong
      implements FlowableSubscriber<T>, Subscription {
  
          private static final long serialVersionUID = 2288246011222124525L;
  
          final Subscriber<? super T> downstream;
  
          long remaining;
  
          Subscription upstream;
  
          TakeSubscriber(Subscriber<? super T> actual, long remaining) {
              this.downstream = actual;
              this.remaining = remaining;
              lazySet(remaining);
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(this.upstream, s)) {
                  if (remaining == 0L) {
                      s.cancel();
                      EmptySubscription.complete(downstream);
                  } else {
                      this.upstream = s;
                      downstream.onSubscribe(this);
                  }
              }
          }
  
          @Override
          public void onNext(T t) {
              long r = remaining;
              if (r > 0L) {
                  remaining = --r;
                  downstream.onNext(t);
                  if (r == 0L) {
                      upstream.cancel();
                      downstream.onComplete();
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (remaining > 0L) {
                  remaining = 0L;
                  downstream.onError(t);
              } else {
                  RxJavaPlugins.onError(t);
              }
          }
  
          @Override
          public void onComplete() {
              if (remaining > 0L) {
                  remaining = 0L;
                  downstream.onComplete();
              }
          }
  
          @Override
          public void request(long n) {
              if (SubscriptionHelper.validate(n)) {
                  for (;;) {
                      long r = get();
                      if (r == 0L) {
                          break;
                      }
                      long toRequest = Math.min(r, n);
                      long u = r - toRequest;
                      if (compareAndSet(r, u)) {
                          upstream.request(toRequest);
                          break;
                      }
                  }
              }
          }
  
          @Override
          public void cancel() {
              upstream.cancel();
          }
  
      }
  }
  