content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.bookkeeper.common.collections;
  
  import java.lang.invoke.MethodHandle;
  import java.lang.invoke.MethodHandles;
  import java.lang.invoke.MethodType;
  import lombok.experimental.UtilityClass;
  import lombok.extern.slf4j.Slf4j;
  
  /**
   * Utility class to use "Thread.onSpinWait()" when available.
   */
  @UtilityClass
  @Slf4j
  public class BusyWait {
  
      /**
       * If available (Java 9+), use intrinsic {@link Thread#onSpinWait} which will
       * reduce CPU consumption during the wait, otherwise fallback to regular
       * spinning.
       */
      public static void onSpinWait() {
          if (ON_SPIN_WAIT != null) {
              try {
                  ON_SPIN_WAIT.invokeExact();
              } catch (Throwable t) {
                  // Ignore
              }
          }
      }
  
      private static final MethodHandle ON_SPIN_WAIT;
  
      static {
          MethodHandle handle = null;
          try {
              handle = MethodHandles.lookup().findStatic(Thread.class, "onSpinWait", MethodType.methodType(void.class));
          } catch (Throwable t) {
              // Ignore
              if (log.isDebugEnabled()) {
                  log.debug("Unable to use 'onSpinWait' from JVM", t);
              }
          }
  
          ON_SPIN_WAIT = handle;
      }
  }
  