/*
* @(#) $Id: CompressionFilter.java 389058 2006-03-27 08:10:46Z trustin $
*
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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.mina.filter;
import java.io.IOException;
import org.apache.mina.common.ByteBuffer;
import org.apache.mina.common.IoFilter;
import org.apache.mina.common.IoFilterAdapter;
import org.apache.mina.common.IoFilterChain;
import org.apache.mina.common.IoSession;
import org.apache.mina.filter.support.Zlib;
/**
* An {@link IoFilter} which compresses all data using
* <a href="http://www.jcraft.com/jzlib/">JZlib</a>.
* Support for the LZW (DLCZ) algorithm is also planned.
* <p>
* This filter only supports compression using the <tt>PARTIAL FLUSH</tt> method,
* since that is the only method useful when doing stream level compression.
* <p>
* This filter supports compression/decompression of the input and output
* channels selectively. It can also be enabled/disabled on the fly.
* <p>
* This filter does not discard the zlib objects, keeping them around for the
* entire life of the filter. This is because the zlib dictionary needs to
* be built up over time, which is used during compression and decompression.
* Over time, as repetitive data is sent over the wire, the compression efficiency
* steadily increases.
* <p>
* Note that the zlib header is written only once. It is not necessary that
* the data received after processing by this filter may not be complete due
* to packet fragmentation.
* <p>
* It goes without saying that the other end of this stream should also have a
* compatible compressor/decompressor using the same algorithm.
*
* @author The Apache Directory Project (mina-dev@directory.apache.org)
* @version $Rev: 389058 $, $Date: 2006-03-27 17:10:46 +0900 (Mon, 27 Mar 2006) $
*/
public class CompressionFilter extends IoFilterAdapter
{
/**
* Max compression level. Will give the highest compression ratio, but
* will also take more cpu time and is the slowest.
*/
public static final int COMPRESSION_MAX = Zlib.COMPRESSION_MAX;
/**
* Provides the best speed at the price of a low compression ratio.
*/
public static final int COMPRESSION_MIN = Zlib.COMPRESSION_MIN;
/**
* No compression done on the data.
*/
public static final int COMPRESSION_NONE = Zlib.COMPRESSION_NONE;
/**
* The default compression level used. Provides the best balance
* between speed and compression
*/
public static final int COMPRESSION_DEFAULT = Zlib.COMPRESSION_DEFAULT;
/**
* A session attribute that stores the {@link Zlib} object used for compression.
*/
private static final String DEFLATER = CompressionFilter.class.getName()
+ ".Deflater";
/**
* A session attribute that stores the {@link Zlib} object used for decompression.
*/
private static final String INFLATER = CompressionFilter.class.getName()
+ ".Inflater";
/**
* A flag that allows you to disable compression once.
*/
public static final String DISABLE_COMPRESSION_ONCE = CompressionFilter.class
.getName()
+ ".DisableCompressionOnce";
private boolean compressInbound = true;
private boolean compressOutbound = true;
private int compressionLevel;
/**
* Creates a new instance which compresses outboud data and decompresses
* inbound data with default compression level.
*/
public CompressionFilter()
{
this( true, true, COMPRESSION_DEFAULT );
}
/**
* Creates a new instance which compresses outboud data and decompresses
* inbound data with the specified <tt>compressionLevel</tt>.
*
* @param compressionLevel the level of compression to be used. Must
* be one of {@link #COMPRESSION_DEFAULT},
* {@link #COMPRESSION_MAX},
* {@link #COMPRESSION_MIN}, and
* {@link #COMPRESSION_NONE}.
*/
public CompressionFilter( final int compressionLevel )
{
this( true, true, compressionLevel );
}
/**
* Creates a new instance.
*
* @param compressInbound <tt>true</tt> if data read is to be decompressed
* @param compressOutbound <tt>true</tt> if data written is to be compressed
* @param compressionLevel the level of compression to be used. Must
* be one of {@link #COMPRESSION_DEFAULT},
* {@link #COMPRESSION_MAX},
* {@link #COMPRESSION_MIN}, and
* {@link #COMPRESSION_NONE}.
*/
public CompressionFilter(
final boolean compressInbound,
final boolean compressOutbound,
final int compressionLevel )
{
this.compressionLevel = compressionLevel;
this.compressInbound = compressInbound;
this.compressOutbound = compressOutbound;
}
public void messageReceived( NextFilter nextFilter,
IoSession session, Object message ) throws Exception
{
if( !compressInbound )
{
nextFilter.messageReceived( session, message );
return;
}
Zlib inflater = ( Zlib ) session.getAttribute( INFLATER );
if( inflater == null )
{
throw new IllegalStateException();
}
ByteBuffer inBuffer = ( ByteBuffer ) message;
ByteBuffer outBuffer = inflater.inflate( inBuffer );
nextFilter.messageReceived( session, outBuffer );
}
/*
* @see org.apache.mina.common.IoFilter#filterWrite(org.apache.mina.common.IoFilter.NextFilter, org.apache.mina.common.IoSession, org.apache.mina.common.IoFilter.WriteRequest)
*/
public void filterWrite( NextFilter nextFilter,
IoSession session, WriteRequest writeRequest ) throws IOException
{
if( !compressOutbound )
{
nextFilter.filterWrite( session, writeRequest );
return;
}
if( session.containsAttribute( DISABLE_COMPRESSION_ONCE ) )
{
// Remove the marker attribute because it is temporary.
session.removeAttribute( DISABLE_COMPRESSION_ONCE );
nextFilter.filterWrite( session, writeRequest );
return;
}
Zlib deflater = ( Zlib ) session.getAttribute( DEFLATER );
if( deflater == null )
{
throw new IllegalStateException();
}
ByteBuffer inBuffer = ( ByteBuffer ) writeRequest.getMessage();
ByteBuffer outBuf = deflater.deflate( inBuffer );
nextFilter.filterWrite( session, new WriteRequest( outBuf, writeRequest
.getFuture() ) );
}
public void onPreAdd( IoFilterChain parent, String name, NextFilter nextFilter ) throws Exception
{
if( parent.contains( CompressionFilter.class ) )
{
throw new IllegalStateException( "A filter chain cannot contain more than" +
" one Stream Compression filter." );
}
Zlib deflater = new Zlib( compressionLevel, Zlib.MODE_DEFLATER );
Zlib inflater = new Zlib( compressionLevel, Zlib.MODE_INFLATER );
IoSession session = parent.getSession();
session.setAttribute( DEFLATER, deflater );
session.setAttribute( INFLATER, inflater );
}
/**
* Returns <tt>true</tt> if incoming data is being compressed.
*/
public boolean isCompressInbound()
{
return compressInbound;
}
/**
* Sets if incoming data has to be compressed.
*/
public void setCompressInbound( boolean compressInbound )
{
this.compressInbound = compressInbound;
}
/**
* Returns <tt>true</tt> if the filter is compressing data being written.
*/
public boolean isCompressOutbound()
{
return compressOutbound;
}
/**
* Set if outgoing data has to be compressed.
*/
public void setCompressOutbound( boolean compressOutbound )
{
this.compressOutbound = compressOutbound;
}
public void onPostRemove( IoFilterChain parent, String name, NextFilter nextFilter ) throws Exception
{
super.onPostRemove( parent, name, nextFilter );
IoSession session = parent.getSession();
if( session == null )
{
return;
}
Zlib inflater = ( Zlib ) session.getAttribute( INFLATER );
Zlib deflater = ( Zlib ) session.getAttribute( DEFLATER );
if( deflater != null )
{
deflater.cleanUp();
}
if( inflater != null )
{
inflater.cleanUp();
}
}
}