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package org.multiverse.performancetool;

import sun.misc.Unsafe;

import java.lang.reflect.Field;

/**
 * Simple class to obtain access to the {@link Unsafe} object.  {@link Unsafe}
 * is required to allow efficient CAS operations on arrays.  Note that the
 * versions in {@link java.util.concurrent.atomic}, such as {@link
 * java.util.concurrent.atomic.AtomicLongArray}, require extra memory ordering
 * guarantees which are generally not needed in these algorithms and are also
 * expensive on most processors.
 */
class UtilUnsafe {
    private UtilUnsafe() {
    } // dummy private constructor

    /**
     * Fetch the Unsafe.  Use With Caution.
     */
    public static Unsafe getUnsafe() {
        // Not on bootclasspath
        if (UtilUnsafe.class.getClassLoader() == null)
            return Unsafe.getUnsafe();
        try {
            final Field fld = Unsafe.class.getDeclaredField("theUnsafe");
            fld.setAccessible(true);
            return (Unsafe) fld.get(UtilUnsafe.class);
        } catch (Exception e) {
            throw new RuntimeException("Could not obtain access to sun.misc.Unsafe", e);
        }
    }
}