/*
 * 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.flink.core.memory;

import org.apache.flink.annotation.Internal;

import java.lang.reflect.Field;
import java.nio.ByteOrder;

/**
 * Utility class for memory operations.
 */
@Internal
public class MemoryUtils {
	
	/** The "unsafe", which can be used to perform native memory accesses. */
	@SuppressWarnings("restriction")
	public static final sun.misc.Unsafe UNSAFE = getUnsafe();
	
	/** The native byte order of the platform on which the system currently runs. */
	public static final ByteOrder NATIVE_BYTE_ORDER = ByteOrder.nativeOrder();

	@SuppressWarnings("restriction")
	private static sun.misc.Unsafe getUnsafe() {
		try {
			Field unsafeField = sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
			unsafeField.setAccessible(true);
			return (sun.misc.Unsafe) unsafeField.get(null);
		} catch (SecurityException e) {
			throw new RuntimeException("Could not access the sun.misc.Unsafe handle, permission denied by security manager.", e);
		} catch (NoSuchFieldException e) {
			throw new RuntimeException("The static handle field in sun.misc.Unsafe was not found.");
		} catch (IllegalArgumentException e) {
			throw new RuntimeException("Bug: Illegal argument reflection access for static field.", e);
		} catch (IllegalAccessException e) {
			throw new RuntimeException("Access to sun.misc.Unsafe is forbidden by the runtime.", e);
		} catch (Throwable t) {
			throw new RuntimeException("Unclassified error while trying to access the sun.misc.Unsafe handle.", t);
		}
	}

	/** Should not be instantiated */
	private MemoryUtils() {}
}