1 /* 2 * Copyright (c) 2010, 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 */ 28 29 import java.io.File; 30 import java.io.FileOutputStream; 31 import java.io.OutputStream; 32 import java.io.IOException; 33 import java.util.Random; 34 import java.util.concurrent.Executors; 35 import java.util.concurrent.ExecutorService; 36 import java.util.concurrent.TimeUnit; 37 import java.nio.ByteBuffer; 38 import java.nio.channels.FileChannel; 39 import static java.nio.file.StandardOpenOption.*; 40 41 public class AtomicAppend { 42 static final Random rand = new Random(); 43 44 // Open file for appending, returning FileChannel 45 static FileChannel newFileChannel(File file) throws IOException { 46 if (rand.nextBoolean()) { 47 return new FileOutputStream(file, true).getChannel(); 48 } else { 49 return FileChannel.open(file.toPath(), APPEND); 50 } 51 } 52 53 // Open file for append, returning OutputStream 54 static OutputStream newOutputStream(File file) throws IOException { 55 if (rand.nextBoolean()) { 56 return new FileOutputStream(file, true); 57 } else { 58 return file.toPath().newOutputStream(APPEND); 59 } 60 } 61 62 // write a byte to the given channel 63 static void write(FileChannel fc, int b) throws IOException { 64 ByteBuffer buf = ByteBuffer.allocate(1); 65 buf.put((byte)b); 66 buf.flip(); 67 if (rand.nextBoolean()) { 68 ByteBuffer[] bufs = new ByteBuffer[1]; 69 bufs[0] = buf; 70 fc.write(bufs); 71 } else { 72 fc.write(buf); 73 } 74 } 75 76 public static void main(String[] args) throws Throwable { 77 final int nThreads = 16; 78 final int writes = 1000; 79 final File file = File.createTempFile("foo", null); 80 try { 81 ExecutorService pool = Executors.newFixedThreadPool(nThreads); 82 for (int i = 0; i < nThreads; i++) 83 pool.execute(new Runnable() { public void run() { 84 try { 85 // randomly choose FileChannel or OutputStream 86 if (rand.nextBoolean()) { 87 try (FileChannel fc = newFileChannel(file)) { 88 for (int j=0; j<writes; j++) write(fc, 'x'); 89 } 90 } else { 91 try (OutputStream out = newOutputStream(file)) { 92 for (int j = 0; j<writes; j++) out.write('x'); 93 } 94 } 95 } catch (IOException ioe) { 96 ioe.printStackTrace(); 97 } 98 }}); 99 pool.shutdown(); 100 pool.awaitTermination(1L, TimeUnit.MINUTES); 101 if (file.length() != (long) (nThreads * writes)) 102 throw new RuntimeException("File not expected length"); 103 } finally { 104 file.delete(); 105 } 106 } 107 }