package acc04j;

import java.lang.reflect.Field;

import java.nio.ByteBuffer;

import java.lang.Object;

import sun.misc.Unsafe;

public class NotSafe {

public static Unsafe getUnsafeObject() throws ClassNotFoundException, NoSuchFieldException, SecurityException,

IllegalArgumentException, IllegalAccessException {

Class<?> u = Class.forName("sun.misc.Unsafe");

Field f = u.getDeclaredField("theUnsafe");

f.setAccessible(true);

return (Unsafe) f.get(null);

}

public static Class<? extends Object> getUnsafeObjectTheHardWay()

throws IllegalAccessException, SecurityException, NoSuchFieldException {

ByteBuffer bb = ByteBuffer.allocateDirect(8192);

bb.putInt(0x41414141);

bb.putInt(0x42424242);

Class<? extends ByteBuffer> c = bb.getClass();

System.out.println(c);

// class java.nio.DirectByteBuffer caches an unsafe-access object in

// field:

// protected static final Unsafe unsafe = Bits.unsafe();

Field unsafe_field = bb.getClass().getDeclaredField("unsafe");

System.out.println(unsafe_field);

unsafe_field.setAccessible(true);

// Reading the value of the unsafe field to get the unsafe object handle

Object unsafe = unsafe_field.get(null);

System.out.println(unsafe);

Class<? extends Object> unsafeClass = unsafe.getClass();

return unsafeClass;

}

public static void main(String[] argv) throws NoSuchFieldException, SecurityException, ClassNotFoundException,

IllegalArgumentException, IllegalAccessException {

SecurityManager sm = System.getSecurityManager();

if (sm != null) {

System.out.println("Security manager installed.");

} else {

System.out.println("No security manager.");

}

// get the offset of the "standard" error output stream.

Unsafe unsafe = getUnsafeObject();

Field f = System.class.getDeclaredField("err");

System.out.println(unsafe.staticFieldOffset(f));

} // end main

} // end NotSafe class