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
021package org.apache.directory.server.dns.protocol;
022
023
024import org.apache.directory.server.dns.io.encoder.DnsMessageEncoder;
025import org.apache.directory.server.dns.messages.DnsMessage;
026import org.apache.mina.core.buffer.IoBuffer;
027import org.apache.mina.core.session.IoSession;
028import org.apache.mina.filter.codec.ProtocolEncoderAdapter;
029import 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 */
038public class DnsTcpEncoder extends ProtocolEncoderAdapter
039{
040    private DnsMessageEncoder encoder = new DnsMessageEncoder();
041
042
043    public void encode( IoSession session, Object message, ProtocolEncoderOutput out )
044    {
045        IoBuffer buf = IoBuffer.allocate( 1024 );
046
047        // make space for short length
048        buf.putShort( ( short ) 0 );
049
050        encoder.encode( buf, ( DnsMessage ) message );
051
052        // mark position
053        int end = buf.position();
054
055        // length is the data minus 2 bytes for the pre-pended length
056        short recordLength = ( short ) ( end - 2 );
057
058        // write the length
059        buf.rewind();
060        buf.putShort( recordLength );
061
062        // set the position back before flipping the buffer
063        buf.position( end );
064        buf.flip();
065
066        out.write( buf );
067    }
068}