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.kafka.common.utils;
  
  import java.io.IOException;
  import java.lang.invoke.MethodHandle;
  import java.lang.invoke.MethodHandles;
  import java.lang.reflect.Field;
  import java.nio.ByteBuffer;
  
  import static java.lang.invoke.MethodHandles.lookup;
  import static java.lang.invoke.MethodType.methodType;
  
  /**
   * Provides a mechanism to unmap mapped and direct byte buffers.
   *
   * The implementation was inspired by the one in Lucene's MMapDirectory.
   */
  public final class ByteBufferUnmapper {
  
      // null if unmap is not supported
      private static final MethodHandle UNMAP;
  
      // null if unmap is supported
      private static final RuntimeException UNMAP_NOT_SUPPORTED_EXCEPTION;
  
      static {
          Object unmap = null;
          RuntimeException exception = null;
          try {
              unmap = lookupUnmapMethodHandle();
          } catch (RuntimeException e) {
              exception = e;
          }
          if (unmap != null) {
              UNMAP = (MethodHandle) unmap;
              UNMAP_NOT_SUPPORTED_EXCEPTION = null;
          } else {
              UNMAP = null;
              UNMAP_NOT_SUPPORTED_EXCEPTION = exception;
          }
      }
  
      private ByteBufferUnmapper() {}
  
      /**
       * Unmap the provided mapped or direct byte buffer.
       *
       * This buffer cannot be referenced after this call, so it's highly recommended that any fields referencing it
       * should be set to null.
       *
       * @throws IllegalArgumentException if buffer is not mapped or direct.
       */
      public static void unmap(String resourceDescription, ByteBuffer buffer) throws IOException {
          if (!buffer.isDirect())
              throw new IllegalArgumentException("Unmapping only works with direct buffers");
          if (UNMAP == null)
              throw UNMAP_NOT_SUPPORTED_EXCEPTION;
  
          try {
              UNMAP.invokeExact(buffer);
          } catch (Throwable throwable) {
              throw new IOException("Unable to unmap the mapped buffer: " + resourceDescription, throwable);
          }
      }
  
      private static MethodHandle lookupUnmapMethodHandle() {
          final MethodHandles.Lookup lookup = lookup();
          try {
              Class<?> unsafeClass = Class.forName("sun.misc.Unsafe");
              MethodHandle unmapper = lookup.findVirtual(unsafeClass, "invokeCleaner",
                      methodType(void.class, ByteBuffer.class));
              Field f = unsafeClass.getDeclaredField("theUnsafe");
              f.setAccessible(true);
              Object theUnsafe = f.get(null);
              return unmapper.bindTo(theUnsafe);
          } catch (ReflectiveOperationException | RuntimeException e1) {
              throw new UnsupportedOperationException("Unmapping is not supported on this platform, because internal " +
                  "Java APIs are not compatible with this Kafka version", e1);
          }
      }
  }
  