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1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *  
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *  
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License. 
18   *  
19   */
20  package org.apache.directory.mitosis.service.protocol.codec;
21  
22  
23  import org.apache.directory.mitosis.service.protocol.message.BaseMessage;
24  import org.apache.mina.common.ByteBuffer;
25  import org.apache.mina.common.IoSession;
26  import org.apache.mina.filter.codec.ProtocolEncoderOutput;
27  import org.apache.mina.filter.codec.demux.MessageEncoder;
28  
29  
30  public abstract class BaseMessageEncoder implements MessageEncoder
31  {
32      public BaseMessageEncoder()
33      {
34      }
35  
36  
37      public final void encode( IoSession session, Object in, ProtocolEncoderOutput out ) throws Exception
38      {
39          BaseMessage m = ( BaseMessage ) in;
40          ByteBuffer buf = ByteBuffer.allocate( 16 );
41          buf.setAutoExpand( true );
42          buf.put( ( byte ) m.getType() );
43          buf.putInt( m.getSequence() );
44          buf.putInt( 0 ); // placeholder for body length field
45  
46          final int bodyStartPos = buf.position();
47          encodeBody( m, buf );
48          final int bodyEndPos = buf.position();
49          final int bodyLength = bodyEndPos - bodyStartPos;
50  
51          // fill bodyLength
52          buf.position( bodyStartPos - 4 );
53          buf.putInt( bodyLength );
54          buf.position( bodyEndPos );
55  
56          buf.flip();
57          out.write( buf );
58      }
59  
60  
61      protected abstract void encodeBody( BaseMessage in, ByteBuffer out ) throws Exception;
62  }