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 both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root 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 //@ThreadSafe
  16 public abstract class AbstractImmutableNativeReference
  17     extends AbstractNativeReference {
  18
  19   /**
  20    * A flag indicating whether the current {@code AbstractNativeReference} is
  21    * responsible to free the underlying C++ object
  22    */
  23   protected final AtomicBoolean owningHandle_;
  24
  25   protected AbstractImmutableNativeReference(final boolean owningHandle) {
  26     this.owningHandle_ = new AtomicBoolean(owningHandle);
  27   }
  28
  29   @Override
  30   public boolean isOwningHandle() {
  31     return owningHandle_.get();
  32   }
  33
  34   /**
  35    * Releases this {@code AbstractNativeReference} from  the responsibility of
  36    * freeing the underlying native C++ object
  37    * <p>
  38    * This will prevent the object from attempting to delete the underlying
  39    * native object in {@code close()}. This must be used when another object
  40    * takes over ownership of the native object or both will attempt to delete
  41    * the underlying object when closed.
  42    * <p>
  43    * When {@code disOwnNativeHandle()} is called, {@code close()} will
  44    * subsequently take no action. As a result, incorrect use of this function
  45    * may cause a memory leak.
  46    * </p>
  47    */
  48   protected final void disOwnNativeHandle() {
  49     owningHandle_.set(false);
  50   }
  51
  52   @Override
  53   public void close() {
  54     if (owningHandle_.compareAndSet(true, false)) {
  55       disposeInternal();
  56     }
  57   }
  58
  59   /**
  60    * The helper function of {@link AbstractImmutableNativeReference#close()}
  61    * which all subclasses of {@code AbstractImmutableNativeReference} must
  62    * implement to release their underlying native C++ objects.
  63    */
  64   protected abstract void disposeInternal();
  65 }