/*

 * Copyright (c) 2017, 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.

 */

/* @test

 * @bug 8012019

 * @summary Tests interruption of threads doing position-based read methods in

 *   an attempt to provoke a deadlock between position sensitive and position

 *   insensitive methods

 */

import java.nio.ByteBuffer;

import java.nio.channels.*;

import java.nio.file.*;

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

public class InterruptDeadlock {

    /**

     * A thread that continuously reads from a FileChannel with

     * read(ByteBuffer,long). The thread terminates when interrupted and/or

     * the FileChannel is closed.

     */

    static class Reader extends Thread {

        final FileChannel fc;

        volatile Exception exception;

        Reader(FileChannel fc) {

            this.fc = fc;

        }

        @Override

        public void run() {

            ByteBuffer bb = ByteBuffer.allocate(1024);

            try {

                long pos = 0L;

                for (;;) {

                    bb.clear();

                    int n = fc.read(bb, pos);

                    if (n > 0)

                        pos += n;

                    // fc.size is important here as it is position sensitive

                    if (pos >= fc.size())

                        pos = 0L;

                }

            } catch (ClosedChannelException x) {

                System.out.println(x.getClass() + " (expected)");

            } catch (Exception unexpected) {

                this.exception = unexpected;

            }

        }

        Exception exception() {

            return exception;

        }

        static Reader startReader(FileChannel fc) {

            Reader r = new Reader(fc);

            r.start();

            return r;

        }

    }

    // the number of reader threads to start

    private static final int READER_COUNT = 4;

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

        Path file = Paths.get("data.txt");

        try (FileChannel fc = FileChannel.open(file, CREATE, TRUNCATE_EXISTING, WRITE)) {

            fc.position(1024L * 1024L);

            fc.write(ByteBuffer.wrap(new byte[1]));

        }

        Reader[] readers = new Reader[READER_COUNT];

        for (int i=1; i<=20; i++) {

            System.out.format("Iteration: %s%n", i);

            try (FileChannel fc = FileChannel.open(file)) {

                boolean failed = false;

                // start reader threads

                for (int j=0; j<READER_COUNT; j++) {

                    readers[j] = Reader.startReader(fc);

                }

                // give readers a bit of time to get started (not strictly required)

                Thread.sleep(100);

                // interrupt and wait for the readers to terminate

                for (Reader r: readers) {

                    r.interrupt();

                }

                for (Reader r: readers) {

                    try {

                        r.join(10000);

                        Exception e = r.exception();

                        if (e != null) {

                            System.err.println("Reader thread failed with: " + e);

                            failed = true;

                        }

                    } catch (InterruptedException x) {

                        System.err.println("Reader thread did not terminte");

                        failed = true;

                    }

                }

                // the channel should not be open at this point

                if (fc.isOpen()) {

                    System.err.println("FileChannel was not closed");

                    failed = true;

                }

                if (failed)

                    throw new RuntimeException("Test failed - see log for details");

            }

        }

    }

}