RawMemoryCopy.java

public class MemoryCopy {
    private static final Unsafe UNSAFE;

    static {
        Unsafe unsafe = null;
        try {
            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
            theUnsafe.setAccessible(true);
            unsafe = (Unsafe) theUnsafe.get(null);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        UNSAFE = unsafe;
    }

    public static void write(ByteBuffer dest, long[] src) {
        if (UNSAFE != null && dest instanceof DirectBuffer) {
            if (dest.capacity() < src.length * 8)
                throw new IllegalArgumentException();
            long address = ((DirectBuffer) dest).address();
            int i = 0;
            for (i = 0; i < src.length; i += 2) {
                UNSAFE.putLong(address, Long.reverseBytes(src[i])); // Big endian
                UNSAFE.putLong(address + 8, Long.reverseBytes(src[i + 1]));// Big endian
                address += Long.BYTES * 2;
            }
            if (i < src.length) {
                UNSAFE.putLong(address, Long.reverseBytes(src[i]));// Big endian
            }
        }
    }
}