undefect. CWE-407 — 63 sites patched across 27 ecosystems

Authors: russell@unturf.com · brackishbert@gmail.com · foxhop.net · TimeHexOn.com

Patches, unit tests, benchmarks, whitepaper, and outreach briefs.
Public domain — no copyright claimed. Use freely.

test/jdk/java/nio/channels/FileChannel/AtomicAppend.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2010, 2018, 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
+ * @summary Check that appends are atomic
+ * @key randomness
+ */
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.OutputStream;
+import java.io.IOException;
+import java.util.Random;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.file.Files;
+import static java.nio.file.StandardOpenOption.*;
+
+public class AtomicAppend {
+    static final Random rand = new Random();
+
+    // Open file for appending, returning FileChannel
+    static FileChannel newFileChannel(File file) throws IOException {
+        if (rand.nextBoolean()) {
+            return new FileOutputStream(file, true).getChannel();
+        } else {
+            return FileChannel.open(file.toPath(), APPEND);
+        }
+    }
+
+    // Open file for append, returning OutputStream
+    static OutputStream newOutputStream(File file) throws IOException {
+        if (rand.nextBoolean()) {
+            return new FileOutputStream(file, true);
+        } else {
+            return Files.newOutputStream(file.toPath(), APPEND);
+        }
+    }
+
+    // write a byte to the given channel
+    static void write(FileChannel fc, int b) throws IOException {
+        ByteBuffer buf = ByteBuffer.allocate(1);
+        buf.put((byte)b);
+        buf.flip();
+        if (rand.nextBoolean()) {
+            ByteBuffer[] bufs = new ByteBuffer[1];
+            bufs[0] = buf;
+            fc.write(bufs);
+        } else {
+            fc.write(buf);
+        }
+    }
+
+    public static void main(String[] args) throws Throwable {
+        final int nThreads = 16;
+        final int writes = 1000;
+        final File file = File.createTempFile("foo", null);
+        try {
+            ExecutorService pool = Executors.newFixedThreadPool(nThreads);
+            for (int i = 0; i < nThreads; i++)
+                pool.execute(new Runnable() { public void run() {
+                    try {
+                        // randomly choose FileChannel or OutputStream
+                        if (rand.nextBoolean()) {
+                            try (FileChannel fc = newFileChannel(file)) {
+                                for (int j=0; j<writes; j++) write(fc, 'x');
+                            }
+                        } else {
+                            try (OutputStream out = newOutputStream(file)) {
+                                for (int j = 0; j<writes; j++) out.write('x');
+                            }
+                        }
+                    } catch (IOException ioe) {
+                        ioe.printStackTrace();
+                    }
+                }});
+            pool.shutdown();
+            pool.awaitTermination(1L, TimeUnit.MINUTES);
+            if (file.length() != (long) (nThreads * writes))
+                throw new RuntimeException("File not expected length");
+        } finally {
+            file.delete();
+        }
+    }
+}