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.activemq.artemis.cli.commands.messages.perf;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.concurrent.TimeUnit;
  
  public class MicrosClock {
  
     // no need for volatile here
     private static long offset = -1;
     private static long NANOS_PER_SECOND = TimeUnit.SECONDS.toNanos(1);
     private static Class vm;
     private static Method getNanoTimeAdjustment;
  
     private static final boolean AVAILABLE = checkAvailable();
  
     private static boolean checkAvailable() {
        try {
           final long now = now();
           if (now < 0) {
              return false;
           }
           return true;
        } catch (Throwable t) {
           return false;
        }
     }
  
     public static boolean isAvailable() {
        return AVAILABLE;
     }
  
     public static long now() {
        try {
           long epochSecond = offset;
           if (vm == null) {
              vm = Class.forName("jdk.internal.misc.VM");
           }
           if (getNanoTimeAdjustment == null) {
              getNanoTimeAdjustment = vm.getMethod("getNanoTimeAdjustment", long.class);
           }
           long nanoAdjustment = (long) getNanoTimeAdjustment.invoke(getNanoTimeAdjustment, epochSecond);
  
           if (nanoAdjustment == -1) {
              epochSecond = System.currentTimeMillis() / 1000 - 1024;
              nanoAdjustment = (long) getNanoTimeAdjustment.invoke(getNanoTimeAdjustment, epochSecond);
              if (nanoAdjustment == -1) {
                 throw new InternalError("Offset " + epochSecond + " is not in range");
              } else {
                 offset = epochSecond;
              }
           }
           final long secs = Math.addExact(epochSecond, Math.floorDiv(nanoAdjustment, NANOS_PER_SECOND));
           final long secsInUs = TimeUnit.SECONDS.toMicros(secs);
           final long nsOffset = (int) Math.floorMod(nanoAdjustment, NANOS_PER_SECOND);
           final long usOffset = TimeUnit.NANOSECONDS.toMicros(nsOffset);
           return secsInUs + usOffset;
        } catch (ClassNotFoundException | NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
           throw new IllegalStateException(e);
        }
     }
  }