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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.mina.filter.codec.statemachine;
21  
22  import org.apache.mina.core.buffer.IoBuffer;
23  import org.apache.mina.core.session.IoSession;
24  import org.apache.mina.filter.codec.ProtocolDecoderOutput;
25  
26  /**
27   * Represents a state in a decoder state machine used by 
28   * {@link DecodingStateMachine}.
29   * 
30   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
31   */
32  public interface DecodingState {
33      /**
34       * Invoked when data is available for this state.
35       * 
36       * @param in the data to be decoded.
37       * @param out used to write decoded objects.
38       * @return the next state if a state transition was triggered (use 
39       *         <code>this</code> for loop transitions) or <code>null</code> if 
40       *         the state machine has reached its end.
41       * @throws Exception if the read data violated protocol specification.
42       */
43      DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
44              throws Exception;
45      
46      /**
47       * Invoked when the associated {@link IoSession} is closed. This method is 
48       * useful when you deal with protocols which don't specify the length of a 
49       * message (e.g. HTTP responses without <tt>content-length</tt> header). 
50       * Implement this method to process the remaining data that 
51       * {@link #decode(IoBuffer, ProtocolDecoderOutput)} method didn't process 
52       * completely.
53       * 
54       * @param out used to write decoded objects.
55       * @return the next state if a state transition was triggered (use 
56       *         <code>this</code> for loop transitions) or <code>null</code> if 
57       *         the state machine has reached its end.
58       * @throws Exception if the read data violated protocol specification.
59       */
60      DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception;
61  }