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.encoder.DnsMessageEncoder;
025    import org.apache.directory.server.dns.messages.DnsMessage;
026    import org.apache.mina.core.buffer.IoBuffer;
027    import org.apache.mina.core.session.IoSession;
028    import org.apache.mina.filter.codec.ProtocolEncoderAdapter;
029    import org.apache.mina.filter.codec.ProtocolEncoderOutput;
030    
031    
032    /**
033     * A ProtocolEncoder for use in the MINA framework that uses the 
034     * DnsMessageEncoder to encode DnsMessages.
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 DnsTcpEncoder extends ProtocolEncoderAdapter
040    {
041        private DnsMessageEncoder encoder = new DnsMessageEncoder();
042    
043    
044        public void encode( IoSession session, Object message, ProtocolEncoderOutput out )
045        {
046            IoBuffer buf = IoBuffer.allocate( 1024 );
047    
048            // make space for short length
049            buf.putShort( ( short ) 0 );
050    
051            encoder.encode( buf, ( DnsMessage ) message );
052    
053            // mark position
054            int end = buf.position();
055    
056            // length is the data minus 2 bytes for the pre-pended length
057            short recordLength = ( short ) ( end - 2 );
058    
059            // write the length
060            buf.rewind();
061            buf.putShort( recordLength );
062    
063            // set the position back before flipping the buffer
064            buf.position( end );
065            buf.flip();
066    
067            out.write( buf );
068        }
069    }