xbytebuffer.java

业界著名的tomcat服务器的最新6.0的源代码。

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.tribes.io;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.nio.ByteBuffer;

/**
 * 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.
 * <br>
 * <b>THIS CLASS IS NOT THREAD SAFE</B><BR>
 * <br/>
 * Transfer package:
 * <ul>
 * <li><b>START_DATA/b> - 7 bytes - <i>FLT2002</i></li>
 * <li><b>SIZE</b>      - 4 bytes - size of the data package</li>
 * <li><b>DATA</b>      - should be as many bytes as the prev SIZE</li>
 * <li><b>END_DATA</b>  - 7 bytes - <i>TLF2003</i></lI>
 * </ul>
 * @author Filip Hanik
 * @version $Revision: 467173 $, $Date: 2006-10-24 01:12:17 +0200 (mar., 24 oct. 2006) $
 */
public class XByteBuffer
{
    
    public static org.apache.juli.logging.Log log =
        org.apache.juli.logging.LogFactory.getLog( XByteBuffer.class );
    
    /**
     * This is a package header, 7 bytes (FLT2002)
     */
    public static final byte[] START_DATA = {70,76,84,50,48,48,50};
    
    /**
     * This is the package footer, 7 bytes (TLF2003)
     */
    public static final byte[] END_DATA = {84,76,70,50,48,48,51};
 
    /**
     * Default size on the initial byte buffer
     */
    private static final int DEF_SIZE = 2048;
 
    /**
     * Default size to extend the buffer with
     */
    private 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;
    
    /**
     * Flag for discarding invalid packages
     * If this flag is set to true, and append(byte[],...) is called,
     * the data added will be inspected, and if it doesn't start with 
     * <code>START_DATA</code> it will be thrown away.
     * 
     */
    protected boolean discard = true;
    
    /**
     * Constructs a new XByteBuffer
     * @param size - the initial size of the byte buffer
     * @todo use a pool of byte[] for performance
     */
    public XByteBuffer(int size, boolean discard) {
        buf = new byte[size];
        this.discard = discard;
    }
    
    public XByteBuffer(byte[] data,boolean discard) {
        this(data,data.length+128,discard);
    }
    
    public XByteBuffer(byte[] data, int size,boolean discard) {
        int length = Math.max(data.length,size);
        buf = new byte[length];
        System.arraycopy(data,0,buf,0,data.length);
        bufSize = data.length;
        this.discard = discard;
    }
    
    public int getLength() {
        return bufSize;
    }

    public void setLength(int size) {
        if ( size > buf.length ) throw new ArrayIndexOutOfBoundsException("Size is larger than existing buffer.");
        bufSize = size;
    }
    
    public void trim(int length) {
        if ( (bufSize - length) < 0 ) 
            throw new ArrayIndexOutOfBoundsException("Can't trim more bytes than are available. length:"+bufSize+" trim:"+length);
        bufSize -= length;
    }
    
    public void reset() {
        bufSize = 0;
    }
            
    public byte[] getBytesDirect() {
        return this.buf;
    }

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

    /**
     * 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(ByteBuffer b, int len) {
        int newcount = bufSize + len;
        if (newcount > buf.length) {
            expand(newcount);
        }
        b.get(buf,bufSize,len);
        
        bufSize = newcount;
        
        if ( discard ) {
            if (bufSize > START_DATA.length && (firstIndexOf(buf, 0, START_DATA) == -1)) {
                bufSize = 0;
                log.error("Discarded the package, invalid header");
                return false;
            }
        }
        return true;

    }
    
    public boolean append(byte i) {
        int newcount = bufSize + 1;
        if (newcount > buf.length) {
            expand(newcount);
        }
        buf[bufSize] = i;
        bufSize = newcount;
        return true;
    }


    public boolean append(boolean i) {
        int newcount = bufSize + 1;
        if (newcount > buf.length) {
            expand(newcount);
        }
        XByteBuffer.toBytes(i,buf,bufSize);
        bufSize = newcount;
        return true;
    }

    public boolean append(long i) {
        int newcount = bufSize + 8;
        if (newcount > buf.length) {
            expand(newcount);
        }
        XByteBuffer.toBytes(i,buf,bufSize);
        bufSize = newcount;
        return true;
    }
    
    public boolean append(int i) {
        int newcount = bufSize + 4;
        if (newcount > buf.length) {
            expand(newcount);
        }
        XByteBuffer.toBytes(i,buf,bufSize);
        bufSize = newcount;
        return true;
    }

    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;
        }

        int newcount = bufSize + len;
        if (newcount > buf.length) {
            expand(newcount);
        }
        System.arraycopy(b, off, buf, bufSize, len);
        bufSize = newcount;

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

    public void expand(int newcount) {
        //don't change the allocation strategy
        byte newbuf[] = new byte[Math.max(buf.length << 1, newcount)];
        System.arraycopy(buf, 0, newbuf, 0, bufSize);
        buf = newbuf;
    }
    
    public int getCapacity() {
        return buf.length;
    }


    /**
     * Internal mechanism to make a check if a complete package exists
     * within the buffer
     * @return - true if a complete package (header,compress,size,data,footer) exists within the buffer
     */
    public int countPackages() {
        return countPackages(false);
    }

    public int countPackages(boolean first)
    {
        int cnt = 0;
        int pos = START_DATA.length;
        int start = 0;

        while ( start < bufSize ) {
            //first check start header
            int index = XByteBuffer.firstIndexOf(buf,start,START_DATA);
            //if the header (START_DATA) isn't the first thing or
            //the buffer isn't even 14 bytes
            if ( index != start || ((bufSize-start)<14) ) break;
            //next 4 bytes are compress flag not needed for count packages
            //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;
            //we only want to verify that we have at least one package
            if ( first ) break;
        }
        return cnt;
    }

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