/*

 * 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;

import java.lang.reflect.*;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLClassLoader;

import java.nio.file.Paths;

public class Agent implements ClassFileTransformer {

    public static ClassLoader newClassLoader() {

        try {

            return new URLClassLoader(new URL[] {

                    Paths.get(System.getProperty("test.classes",".")).toUri().toURL(),

            }, null);

        } catch (MalformedURLException e){

            throw new RuntimeException("Unexpected URL conversion failure", e);

        }

    }

    static public Class Test_class;

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

        // loader2 must be first on the list so loader 1 must be used first

        ClassLoader loader1 = newClassLoader();

        Class dummy = loader1.loadClass("Test");

        ClassLoader loader2 = newClassLoader();

        Test_class = loader2.loadClass("Test");

        Method m3 = Test_class.getMethod("m3", ClassLoader.class);

        // Add speculative trap in m2() (loaded by loader1) that

        // references m4() (loaded by loader2).

        m3.invoke(Test_class.newInstance(), loader1);

        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 Test loaded by loader2

        for (int i = 0; i < 2; i++) {

            try {

                VirtualMachine vm = VirtualMachine.attach(pid);

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

                vm.detach();

            } catch (Exception e) {

                throw new RuntimeException(e);

            }

        }

        // Will process loader2 first, find m4() is redefined and

        // needs to be freed then process loader1, check the

        // speculative trap in m2() and try to access m4() which was

        // freed already.

        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 + " "+ classLoader);

        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);

    }

}