ceph/src/rocksdb/java/src/main/java/org/rocksdb/AbstractImmutableNativeReference.java

   1 // Copyright (c) 2016, Facebook, Inc.  All rights reserved.
   2 // This source code is licensed under the BSD-style license found in the
   3 // LICENSE file in the root directory of this source tree. An additional grant
   4 // of patent rights can be found in the PATENTS file in the same directory.
   5
   6 package org.rocksdb;
   7
   8 import java.util.concurrent.atomic.AtomicBoolean;
   9
  10 /**
  11  * Offers functionality for implementations of
  12  * {@link AbstractNativeReference} which have an immutable reference to the
  13  * underlying native C++ object
  14  */
  15 public abstract class AbstractImmutableNativeReference
  16     extends AbstractNativeReference {
  17
  18   /**
  19    * A flag indicating whether the current {@code AbstractNativeReference} is
  20    * responsible to free the underlying C++ object
  21    */
  22   private final AtomicBoolean owningHandle_;
  23
  24   protected AbstractImmutableNativeReference(final boolean owningHandle) {
  25     this.owningHandle_ = new AtomicBoolean(owningHandle);
  26   }
  27
  28   @Override
  29   public boolean isOwningHandle() {
  30     return owningHandle_.get();
  31   }
  32
  33   /**
  34    * Releases this {@code AbstractNativeReference} from  the responsibility of
  35    * freeing the underlying native C++ object
  36    * <p>
  37    * This will prevent the object from attempting to delete the underlying
  38    * native object in its finalizer. This must be used when another object
  39    * takes over ownership of the native object or both will attempt to delete
  40    * the underlying object when garbage collected.
  41    * <p>
  42    * When {@code disOwnNativeHandle()} is called, {@code dispose()} will
  43    * subsequently take no action. As a result, incorrect use of this function
  44    * may cause a memory leak.
  45    * </p>
  46    *
  47    * @see #dispose()
  48    */
  49   protected final void disOwnNativeHandle() {
  50     owningHandle_.set(false);
  51   }
  52
  53   @Override
  54   public void close() {
  55     if (owningHandle_.compareAndSet(true, false)) {
  56       disposeInternal();
  57     }
  58   }
  59
  60   /**
  61    * The helper function of {@link AbstractImmutableNativeReference#dispose()}
  62    * which all subclasses of {@code AbstractImmutableNativeReference} must
  63    * implement to release their underlying native C++ objects.
  64    */
  65   protected abstract void disposeInternal();
  66 }