code: /*
   * 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.datasketches.memory.internal;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  
  /**
   * Extracts a version-dependent reference to the `sun.misc.VM` into a standalone
   * class. The package name for VM has changed in later versions. The appropriate
   * class will be loaded by the class loader depending on the Java version that is used.
   * For more information, see: https://openjdk.java.net/jeps/238
   */
  public final class VirtualMachineMemory {
  
    private static final Class<?> VM_CLASS;
    private static final Method VM_IS_DIRECT_MEMORY_PAGE_ALIGNED_METHOD;
    private static final boolean isPageAligned;
  
    static {
      try {
        VM_CLASS = Class.forName("sun.misc.VM");
        VM_IS_DIRECT_MEMORY_PAGE_ALIGNED_METHOD = VM_CLASS.getDeclaredMethod("isDirectMemoryPageAligned");
        VM_IS_DIRECT_MEMORY_PAGE_ALIGNED_METHOD.setAccessible(true);
        isPageAligned = (boolean) VM_IS_DIRECT_MEMORY_PAGE_ALIGNED_METHOD.invoke(null); // static method
      } catch (final ClassNotFoundException | NoSuchMethodException |  IllegalAccessException
          | IllegalArgumentException | InvocationTargetException | SecurityException e) {
        throw new RuntimeException("Could not acquire sun.misc.VM class: " + e.getClass());
      }
    }
  
    /**
     * Returns true if the direct buffers should be page aligned.
     * @return flag that determines whether direct buffers should be page aligned.
     */
    public static boolean getIsPageAligned() {
      return isPageAligned;
    }
  }
  