/*

 * Copyright (c) 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.*;

import java.lang.management.ManagementFactory;

import com.sun.tools.attach.VirtualMachine;

class A {

    void m() {

    }

}

class B extends A {

    void m() {

    }

}

class C extends A {

    void m() {

    }

}

class Test {

    static public void m() throws Exception {

        for (int i = 0; i < 20000; i++) {

            m1(a);

        }

        for (int i = 0; i < 4; i++) {

            m1(b);

        }

    }

    static boolean m1(A a) {

        boolean res =  Agent.m2(a);

        return res;

    }

    static public A a = new A();

    static public B b = new B();

    static public C c = new C();

}

public class Agent implements ClassFileTransformer {

    static public boolean m2(A a) {

        boolean res = false;

        if (a.getClass() == B.class) {

            a.m();

        } else {

            res = true;

        }

        return res;

    }

    static public void main(String[] args) throws Exception {

        // Create speculative trap entries

        Test.m();

        String nameOfRunningVM = ManagementFactory.getRuntimeMXBean().getName();

        int p = nameOfRunningVM.indexOf('@');

        String pid = nameOfRunningVM.substring(0, p);

        // Make the nmethod go away

        for (int i = 0; i < 10; i++) {

            System.gc();

        }

        // Redefine class

        try {

            VirtualMachine vm = VirtualMachine.attach(pid);

            vm.loadAgent(System.getProperty("test.classes",".") + "/agent.jar", "");

            vm.detach();

        } catch (Exception e) {

            throw new RuntimeException(e);

        }

        Test.m();

        // GC will hit dead method pointer

        for (int i = 0; i < 10; i++) {

            System.gc();

        }

    }

    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 agentmain(String agentArgs, Instrumentation instrumentation) throws Exception {

        Agent transformer = new Agent();

        instrumentation.addTransformer(transformer, true);

        redefine(agentArgs, instrumentation, Test.class);

    }

}