/*
 * Copyright (c) 2017, 2020, 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.lang.instrument.ClassFileTransformer;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.ref.Cleaner;
import java.security.ProtectionDomain;

public class GCDuringDumpTransformer implements ClassFileTransformer {
    static boolean TEST_WITH_CLEANER = Boolean.getBoolean("test.with.cleaner");
    static Cleaner cleaner;
    static Thread thread;
    static Object garbage;

    static {
        if (TEST_WITH_CLEANER) {
            cleaner = Cleaner.create();
            garbage = new Object();
            cleaner.register(garbage, new MyCleaner());
            System.out.println("Registered cleaner");
        }
    }

    public byte[] transform(ClassLoader loader, String name, Class<?> classBeingRedefined,
                            ProtectionDomain pd, byte[] buffer) throws IllegalClassFormatException {
        if (TEST_WITH_CLEANER) {
            if (name.equals("Hello")) {
                garbage = null;
                System.out.println("Unreferenced GCDuringDumpTransformer.garbage");
            }
        } else {
            try {
                makeGarbage();
            } catch (Throwable t) {
                t.printStackTrace();
                try {
                    Thread.sleep(200); // let GC to have a chance to run
                } catch (Throwable t2) {}
            }
        }

        return null;
    }

    private static Instrumentation savedInstrumentation;

    public static void premain(String agentArguments, Instrumentation instrumentation) {
        System.out.println("ClassFileTransformer.premain() is called: TEST_WITH_CLEANER = " + TEST_WITH_CLEANER);
        instrumentation.addTransformer(new GCDuringDumpTransformer(), /*canRetransform=*/true);
        savedInstrumentation = instrumentation;
    }

    public static Instrumentation getInstrumentation() {
        return savedInstrumentation;
    }

    public static void agentmain(String args, Instrumentation inst) throws Exception {
        premain(args, inst);
    }

    public static void makeGarbage() {
        for (int x=0; x<10; x++) {
            Object[] a = new Object[10000];
        }
    }

    static class MyCleaner implements Runnable {
        static int count = 0;
        int i = count++;
        public void run() {
            // Allocate something. This will cause G1 to allocate an EDEN region.
            // See JDK-8245925
            Object o = new Object();
            System.out.println("cleaning " + i);
        }
    }
}