001    /*
002     *  Licensed to the Apache Software Foundation (ASF) under one
003     *  or more contributor license agreements.  See the NOTICE file
004     *  distributed with this work for additional information
005     *  regarding copyright ownership.  The ASF licenses this file
006     *  to you under the Apache License, Version 2.0 (the
007     *  "License"); you may not use this file except in compliance
008     *  with the License.  You may obtain a copy of the License at
009     *  
010     *    http://www.apache.org/licenses/LICENSE-2.0
011     *  
012     *  Unless required by applicable law or agreed to in writing,
013     *  software distributed under the License is distributed on an
014     *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015     *  KIND, either express or implied.  See the License for the
016     *  specific language governing permissions and limitations
017     *  under the License. 
018     *  
019     */
020    
021    package org.apache.directory.server.dns.protocol;
022    
023    
024    import org.apache.directory.server.dns.io.decoder.DnsMessageDecoder;
025    import org.apache.directory.server.i18n.I18n;
026    import org.apache.mina.core.buffer.IoBuffer;
027    import org.apache.mina.core.session.IoSession;
028    import org.apache.mina.filter.codec.CumulativeProtocolDecoder;
029    import org.apache.mina.filter.codec.ProtocolDecoderOutput;
030    
031    
032    /**
033     * A {@link CumulativeProtocolDecoder} which supports DNS operation over TCP,
034     * by reassembling split packets prior to decoding.
035     * 
036     * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
037     * @version $Rev: 545041 $, $Date: 2007-06-06 20:31:34 -0700 (Wed, 06 Jun 2007) $
038     */
039    public class DnsTcpDecoder extends CumulativeProtocolDecoder
040    {
041        private DnsMessageDecoder decoder = new DnsMessageDecoder();
042    
043        private int maxObjectSize = 16384; // 16KB
044    
045    
046        /**
047         * Returns the allowed maximum size of the object to be decoded.
048         * If the size of the object to be decoded exceeds this value, this
049         * decoder will throw a {@link BufferDataException}.  The default
050         * value is <tt>16384</tt> (16KB).
051         * 
052         * @return The max object size.
053         */
054        public int getMaxObjectSize()
055        {
056            return maxObjectSize;
057        }
058    
059    
060        /**
061         * Sets the allowed maximum size of the object to be decoded.
062         * If the size of the object to be decoded exceeds this value, this
063         * decoder will throw a {@link BufferDataException}.  The default
064         * value is <tt>16384</tt> (16KB).
065         * 
066         * @param maxObjectSize 
067         */
068        public void setMaxObjectSize( int maxObjectSize )
069        {
070            if ( maxObjectSize <= 0 )
071            {
072                throw new IllegalArgumentException( I18n.err( I18n.ERR_634, maxObjectSize ) );
073            }
074    
075            this.maxObjectSize = maxObjectSize;
076        }
077    
078    
079        @Override
080        protected boolean doDecode( IoSession session, IoBuffer in, ProtocolDecoderOutput out ) throws Exception
081        {
082            if ( !in.prefixedDataAvailable( 2, maxObjectSize ) )
083            {
084                return false;
085            }
086    
087            in.getShort();
088    
089            out.write( decoder.decode( in ) );
090    
091            return true;
092        }
093    }