xbytebuffer.java

This temp directory is used by the JVM for temporary file storage. The JVM is configured to use thi

/*
 * $Header: /home/cvs/jakarta-tomcat-catalina/modules/cluster/src/share/org/apache/catalina/cluster/io/XByteBuffer.java,v 1.6 2004/02/05 22:57:52 fhanik Exp $
 * $Revision: 1.6 $
 * $Date: 2004/02/05 22:57:52 $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  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 acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * 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 THE APACHE SOFTWARE FOUNDATION 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 the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * [Additional notices, if required by prior licensing conditions]
 *
 */

package org.apache.catalina.cluster.io;

/**
 * The XByteBuffer provides a dual functionality.
 * One, it stores message bytes and automatically extends the byte buffer if needed.<BR>
 * Two, it can encode and decode packages so that they can be defined and identified
 * as they come in on a socket.
 *
 * @author Filip Hanik
 * @version $Revision: 1.6 $, $Date: 2004/02/05 22:57:52 $
 */


public class XByteBuffer
{
    
    public static org.apache.commons.logging.Log log =
        org.apache.commons.logging.LogFactory.getLog( XByteBuffer.class );
    
    /**
     * This is a package header, 7 bytes
     */
    public static final byte[] START_DATA = {70,76,84,50,48,48,50};
    /**
     * This is the package footer, 7 bytes
     */
    public static final byte[] END_DATA = {84,76,70,50,48,48,51};
    //A package looks like, always.
    /**
     * START_DATA - 7 bytes
     * SIZE       - 4 bytes - size of the data package
     * DATA       - should be as many bytes as the prev SIZE
     * END_DATA   - 7 bytes
     */

    /**
     * Default size on the initial byte buffer
     */
    static final int DEF_SIZE = 1024;
    /**
     * Default size to extend the buffer with
     */
    static final int DEF_EXT  = 1024;
    /**
     * Variable to hold the data
     */
    protected byte[] buf = null;
    /**
     * Current length of data in the buffer
     */
    protected int bufSize = 0;

    /**
     * Constructs a new XByteBuffer
     * @param size - the initial size of the byte buffer
     */
    public XByteBuffer(int size) {
        buf = new byte[size];
    }//XByteBuffer

    /**
     * Constructs a new XByteBuffer with an initial size of 1024 bytes
     */
    public XByteBuffer()  {
        this(DEF_SIZE);
    }//XByteBuffer

    /**
     * Returns the bytes in the buffer, in its exact length
     * @return
     */
    public byte[] getBytes() {
        byte[] b = new byte[bufSize];
        System.arraycopy(buf,0,b,0,bufSize);
        return b;
    }//getBytes

    /**
     * Resets the buffer
     */
    public void clear() {
        bufSize = 0;
    }

    /**
     * Appends the data to the buffer. If the data is incorrectly formatted, ie, the data should always start with the
     * header, false will be returned and the data will be discarded.
     * @param b - bytes to be appended
     * @param off - the offset to extract data from
     * @param len - the number of bytes to append.
     * @return true if the data was appended correctly. Returns false if the package is incorrect, ie missing header or something, or the length of data is 0
     */
    public boolean append(byte[] b, int off, int len) {
        if ((off < 0) || (off > b.length) || (len < 0) ||
            ((off + len) > b.length) || ((off + len) < 0))  {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return false;
        }//end if

        int newcount = bufSize + len;
        if (newcount > buf.length) {
            byte newbuf[] = new byte[Math.max(buf.length << 1, newcount)];
            System.arraycopy(buf, 0, newbuf, 0, bufSize);
            buf = newbuf;
        }
        System.arraycopy(b, off, buf, bufSize, len);
        bufSize = newcount;

        if (bufSize > START_DATA.length && (firstIndexOf(buf,0,START_DATA)==-1)){
            bufSize = 0;
            log.error("Discarded the package, invalid header");
            return false;
        }
        return true;
    }//append


    /**
     * Internal mechanism to make a check if a complete package exists
     * within the buffer
     * @return - true if a complete package (header,size,data,footer) exists within the buffer
     */
    public int countPackages()
    {
        int cnt = 0;
        int pos = START_DATA.length;
        int start = 0;

        while ( start < bufSize ) {
            //first check start header
            int index = this.firstIndexOf(buf,start,START_DATA);
            //if the header (START_DATA) isn't the first thing or
            //the buffer isn't even 10 bytes
            if ( index != start || ((bufSize-start)<10) ) break;
            //then get the size 4 bytes
            int size = toInt(buf, pos);
            //now the total buffer has to be long enough to hold
            //START_DATA.length+4+size+END_DATA.length
            pos = start + START_DATA.length + 4 + size;
            if ( (pos + END_DATA.length) > bufSize) break;
            //and finally check the footer of the package END_DATA
            int newpos = firstIndexOf(buf, pos, END_DATA);
            //mismatch, there is no package
            if (newpos != pos) break;
            //increase the packet count
            cnt++;
            //reset the values
            start = pos + END_DATA.length;
            pos = start + START_DATA.length;
        }//while
        return cnt;
    }//getSize

    /**
     * Method to check if a package exists in this byte buffer.
     * @return - true if a complete package (header,size,data,footer) exists within the buffer
     */
    public boolean doesPackageExist()  {
        return (countPackages()>0);
    }//doesPackageExist