Java example source code file (ShortWrite.java)

This example Java source code file (ShortWrite.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

boundary, bytebuffer, callable, checksum, crc32, exception, executorservice, future, inetsocketaddress, net, network, nio, random, reader, runtimeexception, short, socketchannel, threads, util, zip

The ShortWrite.java Java example source code

/*
 * Copyright (c) 2012, 2013, 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 7176630 7074436
 * @summary Check for short writes on SocketChannels configured in blocking mode
 */

import java.net.*;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.concurrent.*;
import java.util.Random;
import java.util.zip.CRC32;

public class ShortWrite {

    static final Random rand = new Random();

    /**
     * Returns a checksum on the remaining bytes in the given buffers.
     */
    static long computeChecksum(ByteBuffer... bufs) {
        CRC32 crc32 = new CRC32();
        for (int i=0; i<bufs.length; i++)
            crc32.update(bufs[i]);
        return crc32.getValue();
    }

    /**
     * A task that reads the expected number of bytes and returns the CRC32
     * of those bytes.
     */
    static class Reader implements Callable<Long> {
        final SocketChannel sc;
        final ByteBuffer buf;

        Reader(SocketChannel sc, int expectedSize) {
            this.sc = sc;
            this.buf = ByteBuffer.allocate(expectedSize);
        }

        public Long call() throws Exception {
            while (buf.hasRemaining()) {
                int n = sc.read(buf);
                if (n == -1)
                    throw new RuntimeException("Premature EOF encountered");
            }
            buf.flip();
            return computeChecksum(buf);
        }
    }

    /**
     * Exercise write(ByteBuffer) with given number of bytes.
     */
    static void test1(ExecutorService pool,
                      SocketChannel source,
                      SocketChannel sink,
                      int size)
        throws Exception
    {
        System.out.println("write(ByteBuffer), size=" + size);

        // random bytes in the buffer
        ByteBuffer buf = ByteBuffer.allocate(size);
        rand.nextBytes(buf.array());

        // submit task to read the bytes
        Future<Long> result = pool.submit(new Reader(sink, size));

        // write the bytes
        int n = source.write(buf);
        if (n != size)
            throw new RuntimeException("Short write detected");

        // check the bytes that were received match
        buf.rewind();
        long expected = computeChecksum(buf);
        long actual = result.get();
        if (actual != expected)
            throw new RuntimeException("Checksum did not match");
    }

    /**
     * Exercise write(ByteBuffer[]) with buffers of the given sizes.
     */
    static void testN(ExecutorService pool,
                      SocketChannel source,
                      SocketChannel sink,
                      int... sizes)
        throws Exception
    {
        System.out.print("write(ByteBuffer[]), sizes=");
        for (int size: sizes)
            System.out.print(size + " ");
        System.out.println();

        int total = 0;
        int len = sizes.length;
        ByteBuffer[] bufs = new ByteBuffer[len];
        for (int i=0; i<len; i++) {
            int size = sizes[i];
            ByteBuffer buf = ByteBuffer.allocate(size);
            rand.nextBytes(buf.array());
            bufs[i] = buf;
            total += size;
        }

        // submit task to read the bytes
        Future<Long> result = pool.submit(new Reader(sink, total));

        // write the bytes
        long n = source.write(bufs);
        if (n != total)
            throw new RuntimeException("Short write detected");

        // check the bytes that were received match
        for (int i=0; i<len; i++)
            bufs[i].rewind();
        long expected = computeChecksum(bufs);
        long actual = result.get();
        if (actual != expected)
            throw new RuntimeException("Checksum did not match");
    }

    public static void main(String[] args) throws Exception {
        ExecutorService pool = Executors.newSingleThreadExecutor();
        try {
            try (ServerSocketChannel ssc = ServerSocketChannel.open()) {
                ssc.bind(new InetSocketAddress(0));
                InetAddress lh = InetAddress.getLocalHost();
                int port = ssc.socket().getLocalPort();
                SocketAddress sa = new InetSocketAddress(lh, port);

                try (SocketChannel source = SocketChannel.open(sa);
                     SocketChannel sink = ssc.accept())
                {
                    // Exercise write(BufferBuffer) on sizes around 128k
                    int BOUNDARY = 128 * 1024;
                    for (int size=(BOUNDARY-2); size<=(BOUNDARY+2); size++) {
                        test1(pool, source, sink, size);
                    }

                    // Exercise write(BufferBuffer) on random sizes
                    for (int i=0; i<20; i++) {
                        int size = rand.nextInt(1024*1024);
                        test1(pool, source, sink, size);
                    }

                    // Exercise write(BufferBuffer[]) on sizes around 128k
                    for (int i=BOUNDARY-2; i<=BOUNDARY+2; i++) {
                        testN(pool, source, sink, i);
                        testN(pool, source, sink, 0, i);
                        testN(pool, source, sink, i, 0);
                        for (int j=BOUNDARY-2; j<=BOUNDARY+2; j++) {
                            testN(pool, source, sink, i, j);
                            testN(pool, source, sink, 0, i, j);
                            testN(pool, source, sink, i, 0, j);
                            testN(pool, source, sink, i, j, 0);
                            for (int k=BOUNDARY-2; k<=BOUNDARY+2; k++) {
                                testN(pool, source, sink, i, j, k);
                                testN(pool, source, sink, 0, i, j, k);
                                testN(pool, source, sink, i, 0, j, k);
                                testN(pool, source, sink, i, j, 0, k);
                                testN(pool, source, sink, i, j, k, 0);
                            }
                        }
                    }

                    // Exercise write(BufferBuffer[]) on random sizes
                    // (assumes IOV_MAX >= 8)
                    for (int i=0; i<20; i++) {
                        int n = rand.nextInt(9);
                        int[] sizes = new int[n];
                        for (int j=0; j<n; j++) {
                            sizes[j] = rand.nextInt(1024*1024);
                        }
                        testN(pool, source, sink, sizes);
                    }
                }
            }

        } finally {
            pool.shutdown();
        }
    }
}