FillArrayWithUnsafe.java

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/**
 * @test
 * @bug 8283408
 * @summary Fill a byte array with Java Unsafe API
 * @run main/othervm -XX:+OptimizeFill compiler.loopopts.FillArrayWithUnsafe
 */

package compiler.loopopts;

import java.lang.reflect.Field;

import sun.misc.Unsafe;

public class FillArrayWithUnsafe {

    private static Unsafe unsafe;

    public static void main(String[] args) throws Exception {
        Class klass = Unsafe.class;
        Field field = klass.getDeclaredField("theUnsafe");
        field.setAccessible(true);
        unsafe = (Unsafe) field.get(null);

        byte[] buffer;
        // Make sure method newByteArray is compiled by C2
        for (int i = 0; i < 50000; i++) {
            buffer = newByteArray(100, (byte) 0x80);
        }
    }

    public static byte[] newByteArray(int size, byte val) {
        byte[] arr = new byte[size];
        int offset = unsafe.arrayBaseOffset(byte[].class);
        for (int i = offset; i < offset + size; i++) {
             unsafe.putByte(arr, i, val);
        }
        return arr;
    }
}