import sun.misc.Unsafe;

/**
 * Smallest possible Unsafe memory access: allocate 8 bytes off-heap, write a long, read it back, free it.
 * Run it under each value of --sun-misc-unsafe-memory-access to see what the JVM does.
 */
public class Probe {
    public static void main(String[] args) {
        Unsafe u = UnsafeAccess.get();
        System.out.println("got Unsafe instance");
        try {
            long addr = u.allocateMemory(8);
            u.putLong(addr, 42L);
            System.out.println("read back " + u.getLong(addr));
            u.freeMemory(addr);
            System.out.println("allocate/put/get/free all succeeded");
        } catch (Throwable t) {
            System.out.println("FAILED: " + t);
        }
        try {
            long addr2 = u.allocateMemory(8);
            u.putLong(addr2, 7L);
            System.out.println("second use read " + u.getLong(addr2));
            u.freeMemory(addr2);
        } catch (Throwable t) {
            System.out.println("second use FAILED: " + t);
        }
    }
}