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Advanced Bloom Filter Based Algorithms for Efficient Approximate Data De-Duplication in Streams
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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.
 */

// @formatter:off
package com.github.jparkie.deduplicator;

import java.lang.reflect.Field;

import sun.misc.Unsafe;

/**
 * Copied From https://github.com/apache/spark/blob/branch-2.0/common/sketch/src/main/java/org/apache/spark/util/sketch/Platform.java
 */
public final class Platform {

    private static final Unsafe _UNSAFE;

    public static final int BYTE_ARRAY_OFFSET;

    public static final int INT_ARRAY_OFFSET;

    public static final int LONG_ARRAY_OFFSET;

    public static final int DOUBLE_ARRAY_OFFSET;

    public static int getInt(Object object, long offset) {
        return _UNSAFE.getInt(object, offset);
    }

    public static void putInt(Object object, long offset, int value) {
        _UNSAFE.putInt(object, offset, value);
    }

    public static boolean getBoolean(Object object, long offset) {
        return _UNSAFE.getBoolean(object, offset);
    }

    public static void putBoolean(Object object, long offset, boolean value) {
        _UNSAFE.putBoolean(object, offset, value);
    }

    public static byte getByte(Object object, long offset) {
        return _UNSAFE.getByte(object, offset);
    }

    public static void putByte(Object object, long offset, byte value) {
        _UNSAFE.putByte(object, offset, value);
    }

    public static short getShort(Object object, long offset) {
        return _UNSAFE.getShort(object, offset);
    }

    public static void putShort(Object object, long offset, short value) {
        _UNSAFE.putShort(object, offset, value);
    }

    public static long getLong(Object object, long offset) {
        return _UNSAFE.getLong(object, offset);
    }

    public static void putLong(Object object, long offset, long value) {
        _UNSAFE.putLong(object, offset, value);
    }

    public static float getFloat(Object object, long offset) {
        return _UNSAFE.getFloat(object, offset);
    }

    public static void putFloat(Object object, long offset, float value) {
        _UNSAFE.putFloat(object, offset, value);
    }

    public static double getDouble(Object object, long offset) {
        return _UNSAFE.getDouble(object, offset);
    }

    public static void putDouble(Object object, long offset, double value) {
        _UNSAFE.putDouble(object, offset, value);
    }

    public static Object getObjectVolatile(Object object, long offset) {
        return _UNSAFE.getObjectVolatile(object, offset);
    }

    public static void putObjectVolatile(Object object, long offset, Object value) {
        _UNSAFE.putObjectVolatile(object, offset, value);
    }

    public static long allocateMemory(long size) {
        return _UNSAFE.allocateMemory(size);
    }

    public static void freeMemory(long address) {
        _UNSAFE.freeMemory(address);
    }

    public static void copyMemory(
            Object src, long srcOffset, Object dst, long dstOffset, long length) {
        // Check if dstOffset is before or after srcOffset to determine if we should copy
        // forward or backwards. This is necessary in case src and dst overlap.
        if (dstOffset < srcOffset) {
            while (length > 0) {
                long size = Math.min(length, UNSAFE_COPY_THRESHOLD);
                _UNSAFE.copyMemory(src, srcOffset, dst, dstOffset, size);
                length -= size;
                srcOffset += size;
                dstOffset += size;
            }
        } else {
            srcOffset += length;
            dstOffset += length;
            while (length > 0) {
                long size = Math.min(length, UNSAFE_COPY_THRESHOLD);
                srcOffset -= size;
                dstOffset -= size;
                _UNSAFE.copyMemory(src, srcOffset, dst, dstOffset, size);
                length -= size;
            }

        }
    }

    /**
     * Raises an exception bypassing compiler checks for checked exceptions.
     */
    public static void throwException(Throwable t) {
        _UNSAFE.throwException(t);
    }

    /**
     * Limits the number of bytes to copy per {@link Unsafe#copyMemory(long, long, long)} to
     * allow safepoint polling during a large copy.
     */
    private static final long UNSAFE_COPY_THRESHOLD = 1024L * 1024L;

    static {
        sun.misc.Unsafe unsafe;
        try {
            Field unsafeField = Unsafe.class.getDeclaredField("theUnsafe");
            unsafeField.setAccessible(true);
            unsafe = (sun.misc.Unsafe) unsafeField.get(null);
        } catch (Throwable cause) {
            unsafe = null;
        }
        _UNSAFE = unsafe;

        if (_UNSAFE != null) {
            BYTE_ARRAY_OFFSET = _UNSAFE.arrayBaseOffset(byte[].class);
            INT_ARRAY_OFFSET = _UNSAFE.arrayBaseOffset(int[].class);
            LONG_ARRAY_OFFSET = _UNSAFE.arrayBaseOffset(long[].class);
            DOUBLE_ARRAY_OFFSET = _UNSAFE.arrayBaseOffset(double[].class);
        } else {
            BYTE_ARRAY_OFFSET = 0;
            INT_ARRAY_OFFSET = 0;
            LONG_ARRAY_OFFSET = 0;
            DOUBLE_ARRAY_OFFSET = 0;
        }
    }
}
// @formatter:on