/*

 * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.security.*;

import java.lang.instrument.*;

import java.lang.reflect.*;

public class Agent implements ClassFileTransformer {

    public synchronized byte[] transform(final ClassLoader classLoader,

                                         final String className,

                                         Class<?> classBeingRedefined,

                                         ProtectionDomain protectionDomain,

                                         byte[] classfileBuffer) {

        System.out.println("Transforming class " + className);

        return classfileBuffer;

    }

    public static void redefine(String agentArgs, Instrumentation instrumentation, Class to_redefine) {

        try {

            instrumentation.retransformClasses(to_redefine);

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

    public static void premain(String agentArgs, Instrumentation instrumentation) {

        Agent transformer = new Agent();

        instrumentation.addTransformer(transformer, true);

        // Redefine java/lang/Object and java/lang/reflect/Method.invoke and

        // java/lang/ClassLoader

        Class object_class = Object.class;

        redefine(agentArgs, instrumentation, object_class);

        Class method_class = Method.class;

        redefine(agentArgs, instrumentation, method_class);

        Class loader_class = ClassLoader.class;

        redefine(agentArgs, instrumentation, loader_class);

        instrumentation.removeTransformer(transformer);

    }

    public static void main(String[] args) {

        byte[] ba = new byte[0];

        // If it survives 100 GC's, it's good.

        for (int i = 0; i < 100 ; i++) {

            System.gc();

            ba.clone();

        }

        try {

            // Use java/lang/reflect/Method.invoke to call

            WalkThroughInvoke a = new WalkThroughInvoke();

            Class aclass = WalkThroughInvoke.class;

            Method m = aclass.getMethod("stackWalk");

            m.invoke(a);

        } catch (Exception x) {

            x.printStackTrace();

        }

    }

}