channelinputstream.java

一个工作流设计及定义的系统,可以直接与数据库结合进行系统工作流程的定义及应用.

/*
 * Copyright (c) 2005, John Mettraux, OpenWFE.org
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 * . Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.  
 * 
 * . 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.
 * 
 * . Neither the name of the "OpenWFE" nor the names of its contributors may be
 *   used to endorse or promote products derived from this software without
 *   specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS 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 THE COPYRIGHT OWNER OR 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.
 *
 * $Id: ChannelInputStream.java,v 1.4 2005/07/13 20:53:39 jmettraux Exp $
 */

//
// ChannelInputStream.java
//
// [e-mail]
//
// generated with 
// jtmpl 1.1.01 2004/05/19 ([e-mail])
//

package openwfe.org.net;

import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;


/**
 * Wrapping a channel inside of an InputStream.
 * The initial intent of this method is to feed a SAXBuilder with a Channel.<br>
 * We had to implement this class in order to avoid 'non-blocking' problems
 * with Channels.newInputStream(ch); ...
 *
 * <p><font size=2>CVS Info :
 * <br>$Author: jmettraux $
 * <br>$Id: ChannelInputStream.java,v 1.4 2005/07/13 20:53:39 jmettraux Exp $ </font>
 *
 * @author [e-mail]
 */
public class ChannelInputStream

    extends java.io.InputStream

{

    /*
    private final static org.apache.log4j.Logger log = org.apache.log4j.Logger
        .getLogger(ChannelInputStream.class.getName());
    */

    //
    // CONSTANTS & co

    private final static int MAX_ATTEMPT = 3;

    //
    // FIELDS

    private ReadableByteChannel channel = null;

    //
    // CONSTRUCTORS

    /**
     * This constructor wraps the given channel.
     */
    public ChannelInputStream (final ReadableByteChannel channel)
    {
        this.channel = channel;
    }

    //
    // METHODS from InputStream

    /**
     * Reads and returns the next byte of the channel.
     */
    public int read ()
        throws java.io.IOException
    {
        //log.debug("read()");

        final ByteBuffer buffer = ByteBuffer.allocateDirect(1);

        final int readCount = this.channel.read(buffer);

        if (readCount < 1) return -1;

        //log.debug("read() 0 buffer remaining : "+buffer.remaining());

        buffer.flip();

        //log.debug("read() 1 buffer remaining : "+buffer.remaining());

        final int result = buffer.get();

        buffer.clear();

        return result;
    }

    /**
     * Reads byte into a given byte array, returns the count of byte read
     * from the channel.
     */
    public int read (final byte[] ba)
        throws java.io.IOException
    {
        //log.debug("read(ba)");

        final ByteBuffer buffer = ByteBuffer.wrap(ba);

        final int readCount = this.channel.read(buffer);

        return readCount;
    }

    /**
     * Reads byte into a given byte array, returns the count of byte read
     * from the channel.
     */
    public int read (final byte[] ba, final int offset, final int length)
        throws java.io.IOException
    {
        //log.debug("read(ba, o, l) : (ba, "+offset+", "+length+")");

        return read(0, ba, offset, length);
    }

    /*
     * doing the job
     */
    private int read 
        (final int attempt, final byte[] ba, final int offset, final int length)
    throws 
        java.io.IOException
    {
        //log.debug
        //    ("read(a, ba, o, l) : ("+attempt+", ba, "+offset+", "+length+")");

        if (attempt > MAX_ATTEMPT) return -1;

        final ByteBuffer buffer = ByteBuffer.wrap(ba, offset, length);

        final int readCount = this.channel.read(buffer);

        //log.debug("read(a, ba, o, l) ("+attempt+") readCount : "+readCount);

        if (readCount == 0)
        {
            Thread.currentThread().yield();

            return read(attempt+1, ba, offset, length);
        }

        return readCount;
    }

    /**
     * Closes this input stream (and especially the underlying channel).
     */
    public void close ()
        throws java.io.IOException
    {
        //this.channel.close();
            // for ed
    }

    //
    // METHODS

    //
    // STATIC METHODS

}