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/*
* 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.opendal;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* NativeObject is the base-class of all OpenDAL classes that have
* a pointer to a native object.
*
*
* NativeObject has the {@link NativeObject#close()} method, which frees its associated
* native object.
*
*
* This function should be called manually, or even better, called implicitly using a
* try-with-resources
* statement, when you are finished with the object. It is no longer called automatically
* during the regular Java GC process via {@link NativeObject#finalize()}.
*
*
* Explanatory note
*
*
* When or if the Garbage Collector calls {@link Object#finalize()}
* depends on the JVM implementation and system conditions, which the programmer
* cannot control. In addition, the GC cannot see through the native reference
* long member variable (which is the pointer value to the native object),
* and cannot know what other resources depend on it.
*
*
* Finalization is deprecated and subject to removal in a future release.
* The use of finalization can lead to problems with security, performance,
* and reliability. See JEP 421
* for discussion and alternatives.
*/
public abstract class NativeObject implements AutoCloseable {
static {
NativeLibrary.loadLibrary();
}
private final AtomicBoolean disposed = new AtomicBoolean(false);
/**
* An immutable reference to the value of the underneath pointer pointing
* to some underlying native OpenDAL object.
*/
protected final long nativeHandle;
protected NativeObject(long nativeHandle) {
this.nativeHandle = nativeHandle;
}
@Override
public void close() {
if (disposed.compareAndSet(false, true)) {
disposeInternal(nativeHandle);
}
}
/**
* Check if the object has been disposed. Useful for defensive programming.
*
* @return if the object has been disposed.
*/
public boolean isDisposed() {
return disposed.get();
}
/**
* Deletes underlying native object pointer.
*
* @param handle to the native object pointer
*/
protected abstract void disposeInternal(long handle);
}