/*

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

 *

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

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 * 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.

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 */

/* @test

 * @bug 6606598 7024172

 * @summary Unit test for java.lang.management.BufferPoolMXBean

 * @run main/othervm Basic

 * @key randomness

 */

import java.nio.ByteBuffer;

import java.nio.MappedByteBuffer;

import java.nio.file.Path;

import java.nio.file.Files;

import static java.nio.file.StandardOpenOption.*;

import java.nio.channels.FileChannel;

import java.lang.management.BufferPoolMXBean;

import java.lang.management.ManagementFactory;

import javax.management.MBeanServer;

import javax.management.ObjectName;

import java.lang.ref.WeakReference;

import java.util.*;

public class Basic {

    // static fields to ensure buffers aren't GC'ed

    static List<ByteBuffer> buffers;

    static MappedByteBuffer mbb;

    // check counters

    static void check(List<BufferPoolMXBean> pools,

                      int minBufferCount,

                      long minTotalCapacity)

    {

        int bufferCount = 0;

        long totalCap = 0;

        long totalMem = 0;

        for (BufferPoolMXBean pool: pools) {

            bufferCount += pool.getCount();

            totalCap += pool.getTotalCapacity();

            totalMem += pool.getMemoryUsed();

        }

        if (bufferCount < minBufferCount)

            throw new RuntimeException("Count less than expected");

        if (totalMem < minTotalCapacity)

            throw new RuntimeException("Memory usage less than expected");

        if (totalCap < minTotalCapacity)

            throw new RuntimeException("Total capacity less than expected");

    }

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

        Random rand = new Random();

        // allocate a few direct buffers

        int bufferCount = 5 + rand.nextInt(20);

        buffers = new ArrayList<ByteBuffer>(bufferCount);

        long totalCapacity = 0L;

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

            int cap = 1024 + rand.nextInt(4096);

            buffers.add( ByteBuffer.allocateDirect(cap) );

            totalCapacity += cap;

        }

        // create a mapped buffer

        Path tmpfile = Files.createTempFile("blah", null);

        tmpfile.toFile().deleteOnExit();

        try (FileChannel fc = FileChannel.open(tmpfile, READ, WRITE)) {

            mbb = fc.map(FileChannel.MapMode.READ_WRITE, 10, 100);

            bufferCount++;

            totalCapacity += mbb.capacity();

        }

        // use platform MXBeans directly

        List<BufferPoolMXBean> pools =

            ManagementFactory.getPlatformMXBeans(BufferPoolMXBean.class);

        check(pools, bufferCount, totalCapacity);

        // use MBeanServer

        MBeanServer server = ManagementFactory.getPlatformMBeanServer();

        Set<ObjectName> mbeans = server.queryNames(

            new ObjectName("java.nio:type=BufferPool,*"), null);

        pools = new ArrayList<BufferPoolMXBean>();

        for (ObjectName name: mbeans) {

            BufferPoolMXBean pool = ManagementFactory

                .newPlatformMXBeanProxy(server, name.toString(), BufferPoolMXBean.class);

            pools.add(pool);

        }

        check(pools, bufferCount, totalCapacity);

        // attempt to unmap mapped buffer

        WeakReference<MappedByteBuffer> ref = new WeakReference<>(mbb);

        mbb = null;

        do {

            System.gc();

            Thread.sleep(250);

        } while (ref.get() != null);

    }

}