1/*
2 * Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24/*
25 * @test
26 * @summary Check that appends are atomic
27 * @key randomness
28 */
29
30import java.io.File;
31import java.io.FileOutputStream;
32import java.io.OutputStream;
33import java.io.IOException;
34import java.util.Random;
35import java.util.concurrent.Executors;
36import java.util.concurrent.ExecutorService;
37import java.util.concurrent.TimeUnit;
38import java.nio.ByteBuffer;
39import java.nio.channels.FileChannel;
40import java.nio.file.Files;
41import static java.nio.file.StandardOpenOption.*;
42
43public class AtomicAppend {
44    static final Random rand = new Random();
45
46    // Open file for appending, returning FileChannel
47    static FileChannel newFileChannel(File file) throws IOException {
48        if (rand.nextBoolean()) {
49            return new FileOutputStream(file, true).getChannel();
50        } else {
51            return FileChannel.open(file.toPath(), APPEND);
52        }
53    }
54
55    // Open file for append, returning OutputStream
56    static OutputStream newOutputStream(File file) throws IOException {
57        if (rand.nextBoolean()) {
58            return new FileOutputStream(file, true);
59        } else {
60            return Files.newOutputStream(file.toPath(), APPEND);
61        }
62    }
63
64    // write a byte to the given channel
65    static void write(FileChannel fc, int b) throws IOException {
66        ByteBuffer buf = ByteBuffer.allocate(1);
67        buf.put((byte)b);
68        buf.flip();
69        if (rand.nextBoolean()) {
70            ByteBuffer[] bufs = new ByteBuffer[1];
71            bufs[0] = buf;
72            fc.write(bufs);
73        } else {
74            fc.write(buf);
75        }
76    }
77
78    public static void main(String[] args) throws Throwable {
79        final int nThreads = 16;
80        final int writes = 1000;
81        final File file = File.createTempFile("foo", null);
82        try {
83            ExecutorService pool = Executors.newFixedThreadPool(nThreads);
84            for (int i = 0; i < nThreads; i++)
85                pool.execute(new Runnable() { public void run() {
86                    try {
87                        // randomly choose FileChannel or OutputStream
88                        if (rand.nextBoolean()) {
89                            try (FileChannel fc = newFileChannel(file)) {
90                                for (int j=0; j<writes; j++) write(fc, 'x');
91                            }
92                        } else {
93                            try (OutputStream out = newOutputStream(file)) {
94                                for (int j = 0; j<writes; j++) out.write('x');
95                            }
96                        }
97                    } catch (IOException ioe) {
98                        ioe.printStackTrace();
99                    }
100                }});
101            pool.shutdown();
102            pool.awaitTermination(1L, TimeUnit.MINUTES);
103            if (file.length() != (long) (nThreads * writes))
104                throw new RuntimeException("File not expected length");
105        } finally {
106            file.delete();
107        }
108    }
109}
110