/*

 * Copyright (c) 2015, 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 randomAccessFile 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 4823133

 * @summary optimize RandomAccessFile.length() and length() is thread safe now.

 */

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.RandomAccessFile;

/**

 *

 * @author vyom.tewari@oracle.com

 */

public class FileLengthTest {

    private static final int BUF_SIZE = 4096;

    private static RandomAccessFile randomAccessFile;

    private static Thread fileLengthCaller;

    private static Thread fileContentReader;

    private static StringBuilder fileContents;

    private static volatile boolean isFailed = false;

    /**

     * this thread will call length() in loop

     */

    private static void startLengthThread() {

        if (randomAccessFile == null) {

            return;

        }

        fileLengthCaller = new Thread(() -> {

            while (true) {

                try {

                    long length = randomAccessFile.length();

                    if (length < 0) {

                        return;

                    }

                } catch (IOException ex) {

                    return;

                }

            }

        });

        fileLengthCaller.setName("RandomAccessFile-length-caller");

        fileLengthCaller.setDaemon(true);

        fileLengthCaller.start();

    }

    /**

     * this thread will call read() and store the content in internal buffer.

     */

    private static void startReaderThread() {

        if (randomAccessFile == null) {

            return;

        }

        fileContentReader = new Thread(() -> {

            StringBuilder sb = new StringBuilder(BUF_SIZE);

            int i;

            byte arr[] = new byte[8];

            try {

                while ((i = randomAccessFile.read(arr)) != -1) {

                    sb.append(new String(arr, 0, i));

                }

                if (!sb.toString().equals(fileContents.toString())) {

                    isFailed = true;

                }

            } catch (IOException ex) {

            }

        });

        fileContentReader.setName("RandomAccessFile-content-reader");

        fileContentReader.setDaemon(true);

        fileContentReader.start();

    }

    public static void main(String args[]) {

        byte arr[] = new byte[BUF_SIZE];

        String testFile = "testfile.txt";

        try {

            createDummyFile(testFile);

            File file = new File(testFile);

            file.deleteOnExit();

            randomAccessFile = new RandomAccessFile(file, "r");

            int count = randomAccessFile.read(arr);

            randomAccessFile.seek(0);

            fileContents = new StringBuilder(BUF_SIZE);

            fileContents.append(new String(arr, 0, count));

            startLengthThread();

            startReaderThread();

            fileContentReader.join();

        } catch (FileNotFoundException | InterruptedException ex) {

        } catch (IOException ex) {

        } finally {

            try {

                randomAccessFile.close();

            } catch (IOException ex) {

            }

        }

        if (isFailed) {

            throw new RuntimeException("RandomAccessFile.length() changed the underlying file pointer.");

        }

    }

    private static void createDummyFile(String fileName) throws FileNotFoundException, IOException {

        try (FileOutputStream outputStream = new FileOutputStream(new File(fileName))) {

            String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";

            int count = 0;

            while ((count + str.length()) < BUF_SIZE) {

                outputStream.write(str.getBytes());

                count += str.length();

            }

            outputStream.flush();

        }

    }

}