KeepAliveStream.java

/*
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 * 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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
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 */

package sun.net.www.http;

import java.io.*;
import sun.net.ProgressSource;
import sun.net.www.MeteredStream;

/**
 * A stream that has the property of being able to be kept alive for
 * multiple downloads from the same server.
 *
 * @author Stephen R. Pietrowicz (NCSA)
 * @author Dave Brown
 */
public
class KeepAliveStream extends MeteredStream implements Hurryable {

    // instance variables
    HttpClient hc;

    boolean hurried;

    // has this KeepAliveStream been put on the queue for asynchronous cleanup.
    protected boolean queuedForCleanup = false;

    private static final KeepAliveStreamCleaner queue = new KeepAliveStreamCleaner();
    private static Thread cleanerThread; // null

    /**
     * Constructor
     */
    public KeepAliveStream(InputStream is, ProgressSource pi, long expected, HttpClient hc)  {
        super(is, pi, expected);
        this.hc = hc;
    }

    /**
     * Attempt to cache this connection
     */
    public void close() throws IOException  {
        // If the inputstream is closed already, just return.
        if (closed) {
            return;
        }

        // If this stream has already been queued for cleanup.
        if (queuedForCleanup) {
            return;
        }

        // Skip past the data that's left in the Inputstream because
        // some sort of error may have occurred.
        // Do this ONLY if the skip won't block. The stream may have
        // been closed at the beginning of a big file and we don't want
        // to hang around for nothing. So if we can't skip without blocking
        // we just close the socket and, therefore, terminate the keepAlive
        // NOTE: Don't close super class
        try {
            if (expected > count) {
                long nskip = expected - count;
                if (nskip <= available()) {
                    do {} while ((nskip = (expected - count)) > 0L
                                 && skip(Math.min(nskip, available())) > 0L);
                } else if (expected <= KeepAliveStreamCleaner.MAX_DATA_REMAINING && !hurried) {
                    //put this KeepAliveStream on the queue so that the data remaining
                    //on the socket can be cleanup asyncronously.
                    queueForCleanup(new KeepAliveCleanerEntry(this, hc));
                } else {
                    hc.closeServer();
                }
            }
            if (!closed && !hurried && !queuedForCleanup) {
                hc.finished();
            }
        } finally {
            if (pi != null)
                pi.finishTracking();

            if (!queuedForCleanup) {
                // nulling out the underlying inputstream as well as
                // httpClient to let gc collect the memories faster
                in = null;
                hc = null;
                closed = true;
            }
        }
    }

    /* we explicitly do not support mark/reset */

    public boolean markSupported()  {
        return false;
    }

    public void mark(int limit) {}

    public void reset() throws IOException {
        throw new IOException("mark/reset not supported");
    }

    public synchronized boolean hurry() {
        try {
            /* CASE 0: we're actually already done */
            if (closed || count >= expected) {
                return false;
            } else if (in.available() < (expected - count)) {
                /* CASE I: can't meet the demand */
                return false;
            } else {
                /* CASE II: fill our internal buffer
                 * Remind: possibly check memory here
                 */
                int size = (int) (expected - count);
                byte[] buf = new byte[size];
                DataInputStream dis = new DataInputStream(in);
                dis.readFully(buf);
                in = new ByteArrayInputStream(buf);
                hurried = true;
                return true;
            }
        } catch (IOException e) {
            // e.printStackTrace();
            return false;
        }
    }

    private static void queueForCleanup(KeepAliveCleanerEntry kace) {
        synchronized(queue) {
            if(!kace.getQueuedForCleanup()) {
                if (!queue.offer(kace)) {
                    kace.getHttpClient().closeServer();
                    return;
                }

                kace.setQueuedForCleanup();
                queue.notifyAll();
            }

            boolean startCleanupThread = (cleanerThread == null);
            if (!startCleanupThread) {
                if (!cleanerThread.isAlive()) {
                    startCleanupThread = true;
                }
            }

            if (startCleanupThread) {
                java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<Void>() {
                    public Void run() {
                        // We want to create the Keep-Alive-SocketCleaner in the
                        // system threadgroup
                        ThreadGroup grp = Thread.currentThread().getThreadGroup();
                        ThreadGroup parent = null;
                        while ((parent = grp.getParent()) != null) {
                            grp = parent;
                        }

                        cleanerThread = new Thread(grp, queue, "Keep-Alive-SocketCleaner");
                        cleanerThread.setDaemon(true);
                        cleanerThread.setPriority(Thread.MAX_PRIORITY - 2);
                        // Set the context class loader to null in order to avoid
                        // keeping a strong reference to an application classloader.
                        cleanerThread.setContextClassLoader(null);
                        cleanerThread.start();
                        return null;
                    }
                });
            }
        } // queue
    }

    protected long remainingToRead() {
        return expected - count;
    }

    protected void setClosed() {
        in = null;
        hc = null;
        closed = true;
    }
}