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.
   */
  
  /*
   * The code was inspired by the similarly named JCTools class:
   * https://github.com/JCTools/JCTools/blob/master/jctools-core/src/main/java/org/jctools/queues/atomic
   */
  
  package io.reactivex.rxjava3.operators;
  
  import static org.junit.Assert.*;
  
  import java.util.concurrent.atomic.*;
  
  import org.junit.Test;
  
  import io.reactivex.rxjava3.core.RxJavaTest;
  import io.reactivex.rxjava3.internal.queue.MpscLinkedQueue;
  
  public class SimpleQueueTest extends RxJavaTest {
  
      @Test(expected = NullPointerException.class)
      public void spscArrayQueueNull() {
          SpscArrayQueue<Object> q = new SpscArrayQueue<>(16);
          q.offer(null);
      }
  
      @Test(expected = NullPointerException.class)
      public void spscLinkedArrayQueueNull() {
          SpscLinkedArrayQueue<Object> q = new SpscLinkedArrayQueue<>(16);
          q.offer(null);
      }
  
      @Test(expected = NullPointerException.class)
      public void mpscLinkedQueueNull() {
          MpscLinkedQueue<Object> q = new MpscLinkedQueue<>();
          q.offer(null);
      }
  
      @Test
      public void spscArrayQueueBiOffer() {
          SpscArrayQueue<Object> q = new SpscArrayQueue<>(16);
          q.offer(1, 2);
  
          assertEquals(1, q.poll());
          assertEquals(2, q.poll());
          assertNull(q.poll());
      }
  
      @Test
      public void spscLinkedArrayQueueBiOffer() {
          SpscLinkedArrayQueue<Object> q = new SpscLinkedArrayQueue<>(16);
          q.offer(1, 2);
  
          assertEquals(1, q.poll());
          assertEquals(2, q.poll());
          assertNull(q.poll());
      }
  
      @Test
      public void mpscLinkedQueueBiOffer() {
          MpscLinkedQueue<Object> q = new MpscLinkedQueue<>();
          q.offer(1, 2);
  
          assertEquals(1, q.poll());
          assertEquals(2, q.poll());
          assertNull(q.poll());
      }
  
      @Test
      public void spscBiOfferCapacity() {
          SpscArrayQueue<Integer> q = new SpscArrayQueue<>(8);
          assertTrue(q.offer(1, 2));
          assertTrue(q.offer(3, 4));
          assertTrue(q.offer(5, 6));
          assertTrue(q.offer(7));
  
          assertFalse(q.offer(8, 9));
          assertFalse(q.offer(9, 10));
      }
  
      @Test
      public void spscLinkedNewBufferPeek() {
          SpscLinkedArrayQueue<Integer> q = new SpscLinkedArrayQueue<>(8);
          assertTrue(q.offer(1, 2));
          assertTrue(q.offer(3, 4));
          assertTrue(q.offer(5, 6));
          assertTrue(q.offer(7, 8)); // this should trigger a new buffer
  
          for (int i = 0; i < 8; i++) {
              assertEquals(i + 1, q.peek().intValue());
              assertEquals(i + 1, q.poll().intValue());
          }
  
          assertNull(q.peek());
          assertNull(q.poll());
      }
  
      @Test
      public void mpscOfferPollRace() throws Exception {
          final MpscLinkedQueue<Integer> q = new MpscLinkedQueue<>();
  
          final AtomicInteger c = new AtomicInteger(3);
  
          Thread t1 = new Thread(new Runnable() {
              int i;
              @Override
              public void run() {
                  c.decrementAndGet();
                  while (c.get() != 0) { }
  
                  while (i++ < 10000) {
                      q.offer(i);
                  }
              }
          });
          t1.start();
  
          Thread t2 = new Thread(new Runnable() {
              int i = 10000;
              @Override
              public void run() {
                  c.decrementAndGet();
                  while (c.get() != 0) { }
  
                  while (i++ < 10000) {
                      q.offer(i);
                  }
              }
          });
          t2.start();
  
          Runnable r3 = new Runnable() {
              int i = 20000;
              @Override
              public void run() {
                  c.decrementAndGet();
                  while (c.get() != 0) { }
  
                  while (--i > 0) {
                      q.poll();
                  }
              }
          };
  
          r3.run();
  
          t1.join();
          t2.join();
      }
  
      @Test
      public void spscLinkedArrayQueueNoNepotism() {
          SpscLinkedArrayQueue<Integer> q = new SpscLinkedArrayQueue<>(16);
  
          AtomicReferenceArray<Object> ara = q.producerBuffer;
  
          for (int i = 0; i < 20; i++) {
              q.offer(i);
          }
  
          assertNotNull(ara.get(16));
  
          for (int i = 0; i < 20; i++) {
              assertEquals(i, q.poll().intValue());
          }
  
          assertNull(ara.get(16));
      }
  }
  