watchedinputstream.java

jxta_src_2.41b jxta 2.41b 最新版源码 from www.jxta.org

/*
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 *
 * $Id: WatchedInputStream.java,v 1.6 2004/05/30 12:27:40 jice Exp $
 */

package net.jxta.util;

import java.io.*;
import java.util.Collection;

public class WatchedInputStream extends FilterInputStream
    implements WatchedStream {

    static final int DEFAULT_CHUNK_SIZE = 4096;
    Collection watchList = null;
    volatile boolean stalled = false;
    volatile boolean idle = true;
    boolean closed = false;
    final int chunkSize;
    InputStream in = null;

    public WatchedInputStream(InputStream in, int chunkSize) {
        super(in);
        this.in = in;
        this.chunkSize = chunkSize;
    }

    public WatchedInputStream(InputStream in) {
        this(in, DEFAULT_CHUNK_SIZE);
    }

    /**
     * {@inheritDoc}
     *
     *  <p/>Debugging toString.
     **/
    public String toString() {
        if( null == in ) {
            return "closed/" + super.toString();
        } else {
            if( in instanceof ByteArrayInputStream ) {
                // ByteArrayInputStream.toString() prints the entire stream! 
                return in.getClass().getName() + "@" + System.identityHashCode(in)  + "/" + super.toString();
            } else {
                return in.toString() + "/" + super.toString();
            }
        }
    }
    
    /**
     * Sets the watcher list onto which this stream must register
     * when it is not idle (so that it can be watched).
     * This implementation may or may not remain registered while idle.
     * This may affect performance but not functionality.
     * It is assumed that that list is monitored by a watcher task that
     * invokes the watch method as often as needed to monitor progress
     * to its satifaction.
     *
     * @param watchList The watchList to register with. Must be a
     * Synchronized Collection.
     */
    public synchronized void setWatchList(Collection watchList) {
        if (this.watchList != null) {
            this.watchList.remove(this);
        }
        this.watchList = watchList;
        watchList.add(this);
    }

		
    // This routine may be invoked as often as progress needs to be asserted.
    // After at most two watch cycles stalling is detected.
    public void watch() {

        if (idle) return;

        if (! stalled) {
            stalled = true; // challenge a write method to clear that flag.
            return;
        }

        // It's stalled. The last time around it was not idle, so we set the
        // stalled flag. Now, it is still not idle and the flag is still there.
        // break the stream.
        try {
            close();
        } catch (IOException ioe) { ; }
    }

    public void close() throws IOException {
        idle = true;
        synchronized(this) {
            if (watchList != null) {
                watchList.remove(this);
                watchList = null;
            }

            // Avoid calling close redundantly; some OSes seem to have
            // deadlock capabilities when doing that.
            
            if (closed) return;
            closed = true;
        }
        super.close();
    }

    public int read() throws IOException {
        stalled = false;
        idle = false;
        try {
            return in.read();
        } finally {
            idle = true;
        }
    }

    // We overload it; not trusting that the base classes method does
    // call read(byte[], int, int) in the future.
    public int read(byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    public int read(byte[] b, int off, int len) throws IOException {

        // Apply the standard checks here; we will call in.read repeatedly
        // which means that errors could be discovered too late per read's
        // contract.

        if (   (off < 0) || (len < 0) || ((off + len) > b.length)
            || ((off + len) < 0)) {

	    throw new IndexOutOfBoundsException();

	}

        stalled = false;
        idle = false;
        int left = len;

        try {
            int i = 0;
            while (left > chunkSize) {
                i = in.read(b, off, chunkSize);
                stalled = false;
                if (i <= 0) {
                    if (left == len) return i;
                    return len - left;
                }
                off += i;
                left -= i;

                // Must check available only after firt read.
                // first read must wait for at least one byte.

                if (in.available() == 0) {
                    return len - left;
                }
            }

            // Read the left over now. If this is not the first read,
            // available has been checked in the loop above.
            i = in.read(b, off, left);
            if (i <= 0) {
                if (left == len) return i;
                return len - left;
            }

            return len - left + i;

        } finally {
            idle = true;
        }
    }
}