bytearraymessageelement.java

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

/************************************************************************
 *
 * $Id: ByteArrayMessageElement.java,v 1.13 2004/08/06 17:42:29 bondolo Exp $
 *
 * 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
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 * 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.
 *********************************************************************************/

package net.jxta.endpoint;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ref.SoftReference;
import java.util.zip.CRC32;         // used in hashCode
import java.util.zip.Checksum;

import java.io.UnsupportedEncodingException;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

import net.jxta.document.MimeMediaType;

/**
 * A Message Element using byte arrays for the element data.
 *
 * <p/>This implementation does not copy the byte array provided and assumes
 * that the contents of the byte array will not change through out the lifetime
 * of the MessageElement.
 *
 * <p/>some synchronization is due to optimization in {@link #getBytes(boolean)}
 * which replaces value of internal member {@link #b}.
 *
 **/
public class ByteArrayMessageElement extends MessageElement {
    
    /**
     *  Log4J category
     **/
    private static transient final Logger LOG = Logger.getLogger( ByteArrayMessageElement.class.getName() );
    
    /**
     *  The bytes of this element.
     **/
    protected byte [] b;
    
    /**
     *  This is the offset of our data within the array
     **/
    protected int offset;
    
    /**
     *  length of the element data. sometimes the same as b.length, but may be
     *  lesser.
     **/
    protected int len;
    
    /**
     * Create a new Message Element. The contents of the provided byte array
     * are <b>not</b> copied during construction.
     *
     * @param name Name of the MessageElement. May be the empty string ("") if
     * the MessageElement is not named.
     * @param type Type of the MessageElement. null is the same as specifying
     * the type "Application/Octet-stream".
     * @param b A byte array containing the contents of this element.
     * @param sig optional message digest/digital signature elemnent or null if
     * no signature is desired.
     **/
    public ByteArrayMessageElement(String name, MimeMediaType type, byte[] b, MessageElement sig) {
        this( name, type, b, 0, b.length, sig );
    }
    
    /**
     * Create a new MessageElement, The contents of the provided byte array are
     * <b>not</b> copied during construction.
     *
     * @param name Name of the MessageElement. May be the empty string ("") if
     * the MessageElement is not named.
     * @param type Type of the MessageElement. null is the same as specifying
     * the type "Application/Octet-stream".
     * @param b A byte array containing the contents of this element.
     * @param offset all bytes before this location in <code>b</code>
     * will be ignored.
     * @param sig optional message digest/digital signature elemnent or null if
     * no signature is desired.
     **/
    public ByteArrayMessageElement(String name, MimeMediaType type, byte[] b, int offset, MessageElement sig) {
        this( name, type, b, offset, b.length - offset, sig );
    }
    
    /**
     *  Create a new Element, but dont add it to the message.  The contents of
     * the byte array are <b>not</b> copied during construction.
     *
     * @param name Name of the MessageElement. May be the empty string ("") if
     * the MessageElement is not named.
     * @param type Type of the MessageElement. null is the same as specifying
     * the type "Application/Octet-stream".
     * @param b A byte array containing the contents of this Element.
     * @param offset all bytes before this location will be ignored.
     * @param len number of bytes to include
     * @param sig optional message digest/digital signature elemnent or null if
     * no signature is desired.
     **/
    public ByteArrayMessageElement(String name, MimeMediaType type, byte[] b, int offset, int len, MessageElement sig) {
        super( name, type, sig );
        
        if( null == b ) {
            throw new IllegalArgumentException( "byte array must not be null" );
        }
        
        if( len < 0 ) {
            throw new IllegalArgumentException( "len must be >= 0 : " + len );
        }
        
        if( offset < 0 ) {
            throw new IllegalArgumentException( "offset must within byte array : " + offset );
        }
        
        if( (0 != len) && (offset >= b.length) ) {
            throw new IllegalArgumentException( "offset must be positioned within byte array : " + offset + "," + len );
        }
        
        if( ((offset + len) > b.length) || ((offset + len) < 0) ) {
            throw new IllegalArgumentException( "offset + len must be positioned within byte array" );
        }
        
        // if we get an empty request and a non-empty buffer, we don't use the provided buffer.
        if( (0 == len) && (0 != b.length) ) {
            b = new byte [len];
            offset = 0;
        }
        
        this.b = b;
        this.offset = offset;
        this.len = len;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public boolean equals( Object target ) {
        if( this == target ) {
            return true;
        }
        
        if( target instanceof MessageElement ) {
            if( !super.equals(target) ) {
                return false;
            }
            
            if( target instanceof ByteArrayMessageElement ) {
                ByteArrayMessageElement likeMe = (ByteArrayMessageElement) target;
                
                synchronized( this ) {
                    synchronized( likeMe ) {
                        if( likeMe.len != len )
                            return false;
                        
                        for( int eachByte = len - 1; eachByte >= 0; eachByte-- ) {
                            if( likeMe.b[likeMe.offset + eachByte] != b[offset + eachByte] )
                                return false;
                        }
                    }
                }
                
                return true;
            } else {
                // have to do a slow stream comparison.
                // XXX 20020615 [e-mail] the performance of this could be much improved.
                try {
                    MessageElement likeMe = (MessageElement) target;
                    
                    InputStream myStream = getStream();
                    InputStream itsStream = likeMe.getStream();
                    
                    int mine;
                    int its;
                    do {
                        mine = myStream.read();
                        its = itsStream.read();
                        
                        if( mine != its )
                            return false;       // content didn't match
                        
                    } while( (-1 != mine) && (-1 != its) );
                    
                    return ( (-1 == mine) && (-1 == its) ); // end at the same time?
                } catch( IOException fatal ) {
                    if (LOG.isEnabledFor(Level.ERROR)) {
                        LOG.error( "MessageElements could not be compared.", fatal );
                    }
                    
                    throw new IllegalStateException( "MessageElements could not be compared." + fatal );
                }
            }
        }
        
        return false; // not a message element
    }
    
    /**
     *  {@inheritDoc}
     **/
    public synchronized int hashCode() {
        Checksum crc = new CRC32();
        crc.update( b, offset, len );
        int dataHash = (int) crc.getValue();
        
        int result = super.hashCode() *  6037 +   // a prime
        dataHash;
        
        return (0 != result) ? result : 1;
    }
    
    /**
     *  {@inheritDoc}
     *
     *  Returns the string representation of this element. The 'charset'
     *  parameter of the mimetype, if any, is used to determine encoding. If
     *  the charset specified is unsupported then the default enconding will be
     *  used.
     *
     *  @return String string representation of this message element.
     **/
    public synchronized String toString( ) {
        String result = null;
        
        if( null != cachedToString ) {
            result = (String) cachedToString.get();
            
            if (null != result)
                return result;
        }
        
/*
        if (LOG.isEnabledFor(Level.DEBUG)) {
            LOG.debug( "creating toString of " + getClass().getName() + '@' + Integer.toHexString(hashCode()) );
        }
 */
        String charset = type.getParameter( "charset" );
        
        try {
            if( null == charset ) {
                result = new String( b, offset, len );
            } else {
                result = new String( b, offset, len, charset );
            }
        } catch ( UnsupportedEncodingException caught ) {
            result = new String( b, offset, len );
        }
        
        cachedToString = new SoftReference( result );
        
        return result;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public long getByteLength() {
        return len;
    }
    
    /**
     *  {@inheritDoc}
     *
     *  <p/>synchronized so that we can replace our internal buffer with
     *  the buffer we are returning if we were using a shared buffer.
     **/
    public synchronized byte[] getBytes( boolean copy ) {
        if( (!copy) && (0 == offset ) && (b.length == len) ) {
            return b;
        }
        
        byte [] result = new byte[ len ];
        
        System.arraycopy( b, offset, result, 0, len );
        
        // if we were using a sub-array we can switch to using this copy.
        if( !copy ) {
            b = result;
            offset = 0;
        }
        
        return result;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public synchronized InputStream getStream() {
        return new ByteArrayInputStream( b, offset, len );
    }
    
    /**
     *  {@inheritDoc}
     **/
    public void sendToStream( OutputStream sendTo ) throws IOException {
        byte [] sending;
        int sendingOffset;
        
        // locals enable us to reduce the time which the object is synchronized.
        synchronized( this ) {
            sending = b;
            sendingOffset = offset;
        }
        
        sendTo.write( sending, sendingOffset, len );
    }
    
    /**
     * Returns the contents of this element as a byte array. If this elements
     * was originally constructed from a intact byte array, the array returned
     * is a "shared" copy of the byte array used by this element. If this
     * element was constructed with an offset of other than zero and a length
     * different than the length of the source array then this function <b>WILL
     * RETURN A COPY OF THE BYTE ARRAY</b>.
     *
     *  @return a byte array containing the contents of this element.
     **/
    public byte [] getBytes() {
        return getBytes( false );
    }
}