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Fork of Esoteric Software's Kryo built by Nathan Sweet that replaces Minlog with slf4j as the logging facade. This contains the shaded reflectasm jar to prevent conflicts with other versions of asm.
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/* Copyright (c) 2008, Nathan Sweet
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
 * conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
 * disclaimer in the documentation and/or other materials provided with the distribution.
 * - Neither the name of Esoteric Software nor the names of its contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */

package com.esotericsoftware.kryo.util;

import static com.esotericsoftware.kryo.util.UnsafeUtil.unsafe;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import sun.misc.Cleaner;
import sun.misc.Unsafe;
import sun.nio.ch.DirectBuffer;

/**
 * A few utility methods for using @link{sun.misc.Unsafe}, mostly for private
 * use.
 * 
 * Use of Unsafe on Android is forbidden, as Android provides only a very limited
 * functionality for this class compared to the JDK version.
 * 
 * @author Roman Levenstein 
 */

public class UnsafeUtil {
	private static final Logger LOGGER = LoggerFactory.getLogger(UnsafeUtil.class);
	
	final static private Unsafe _unsafe;
	final static public long byteArrayBaseOffset;
	final static public long floatArrayBaseOffset;
	final static public long doubleArrayBaseOffset;
	final static public long intArrayBaseOffset;
	final static public long longArrayBaseOffset;
	final static public long shortArrayBaseOffset;
	final static public long charArrayBaseOffset;

	// Constructor to be used for creation of ByteBuffers that use preallocated memory regions 
	static Constructor directByteBufferConstr;
	
	
	static {
		Unsafe tmpUnsafe = null;
		long tmpByteArrayBaseOffset = 0;
		long tmpFloatArrayBaseOffset = 0;
		long tmpDoubleArrayBaseOffset = 0;
		long tmpIntArrayBaseOffset = 0;
		long tmpLongArrayBaseOffset = 0;
		long tmpShortArrayBaseOffset = 0;
		long tmpCharArrayBaseOffset = 0;

		try {
			if (!Util.isAndroid) {
				java.lang.reflect.Field field = sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
				field.setAccessible(true);
				tmpUnsafe = (sun.misc.Unsafe)field.get(null);
				tmpByteArrayBaseOffset = tmpUnsafe.arrayBaseOffset(byte[].class);
				tmpCharArrayBaseOffset = tmpUnsafe.arrayBaseOffset(char[].class);
				tmpShortArrayBaseOffset = tmpUnsafe.arrayBaseOffset(short[].class);
				tmpIntArrayBaseOffset = tmpUnsafe.arrayBaseOffset(int[].class);
				tmpFloatArrayBaseOffset = tmpUnsafe.arrayBaseOffset(float[].class);
				tmpLongArrayBaseOffset = tmpUnsafe.arrayBaseOffset(long[].class);
				tmpDoubleArrayBaseOffset = tmpUnsafe.arrayBaseOffset(double[].class);
			} else {
				LOGGER.trace("static : Running on Android platform. Use of sun.misc.Unsafe should be disabled");
			}
		} catch (java.lang.Exception e) {
			LOGGER.trace("static : sun.misc.Unsafe is not accessible or not available. Use of sun.misc.Unsafe should be disabled");	
		}

		byteArrayBaseOffset = tmpByteArrayBaseOffset;
		charArrayBaseOffset = tmpCharArrayBaseOffset;
		shortArrayBaseOffset = tmpShortArrayBaseOffset;
		intArrayBaseOffset = tmpIntArrayBaseOffset;
		floatArrayBaseOffset = tmpFloatArrayBaseOffset;
		longArrayBaseOffset = tmpLongArrayBaseOffset;
		doubleArrayBaseOffset = tmpDoubleArrayBaseOffset;
		_unsafe = tmpUnsafe;
	}
	
	static {
		ByteBuffer buf = ByteBuffer.allocateDirect(1);
		try {
			directByteBufferConstr = buf.getClass().getDeclaredConstructor(long.class, int.class, Object.class);
			directByteBufferConstr.setAccessible(true);
		} catch (Exception e) {
			directByteBufferConstr = null;
		}		
	}
	
	/***
	 * Return the sun.misc.Unsafe object. If null is returned,
	 * no further Unsafe-related methods are allowed to be invoked from UnsafeUtil.
	 *  
	 * @return instance of sun.misc.Unsafe or null, if this class is not available or not accessible
	 */
	final static public Unsafe unsafe() {
		return _unsafe;
	}
	
	/***
	 * Sort the set of lists by their offsets from the object start address.
	 * 
	 * @param allFields set of fields to be sorted by their offsets
	 */
	public static Field[] sortFieldsByOffset (List allFields) {
		Field[] allFieldsArray = allFields.toArray(new Field[] {});

		Comparator fieldOffsetComparator = new Comparator() {
			@Override
			public int compare (Field f1, Field f2) {
				long offset1 = unsafe().objectFieldOffset(f1);
				long offset2 = unsafe().objectFieldOffset(f2);
				if (offset1 < offset2) return -1;
				if (offset1 == offset2) return 0;
				return 1;
			}
		};

		Arrays.sort(allFieldsArray, fieldOffsetComparator);

		for (Field f : allFields) {
			LOGGER.trace("sortFieldsByOffset : Field '{}' at offset {}", f.getName(), unsafe().objectFieldOffset(f));
		}
		
		return allFieldsArray;
	}
	
	/***
	 * Create a ByteBuffer that uses a provided (off-heap) memory region instead of allocating a new one.
	 * 
	 * @param address address of the memory region to be used for a ByteBuffer
	 * @param size size of the memory region
	 * @return a new ByteBuffer that uses a provided memory region instead of allocating a new one 
	 */
	final static public ByteBuffer getDirectBufferAt(long address, int size) {
		if(directByteBufferConstr == null)
			return null;
		try {
			return directByteBufferConstr.newInstance(address, size, null);
		} catch (Exception e) {
			throw new RuntimeException("Cannot allocate ByteBuffer at a given address: " + address, e);
		}		
	}

	/***
	 * Release a direct buffer.  
	 * 
	 * NOTE: If Cleaner is not accessible due to SecurityManager restrictions, reflection could be used
	 * to obtain the "clean" method and then invoke it.
	 */
	static public void releaseBuffer(ByteBuffer niobuffer) {
		if(niobuffer != null && niobuffer.isDirect()) {
			Object cleaner = ((DirectBuffer) niobuffer).cleaner();
			if(cleaner != null)
				((Cleaner)cleaner).clean();
			niobuffer = null;
		}		
	}
}