View Javadoc

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.filter.codec.ProtocolDecoderException;
24  import org.apache.mina.filter.codec.ProtocolDecoderOutput;
25  
26  /**
27   * {@link DecodingState} which decodes <code>byte</code> values.
28   * 
29   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
30   */
31  public abstract class SingleByteDecodingState implements DecodingState {
32  
33      public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
34              throws Exception {
35          if (in.hasRemaining()) {
36              return finishDecode(in.get(), out);
37          }
38          
39          return this;
40      }
41      
42      /**
43       * {@inheritDoc}
44       */
45      public DecodingState finishDecode(ProtocolDecoderOutput out)
46              throws Exception {
47          throw new ProtocolDecoderException(
48                  "Unexpected end of session while waiting for a single byte.");
49      }
50  
51      /**
52       * Invoked when this state has consumed a complete <code>byte</code>.
53       * 
54       * @param b the byte.
55       * @param out the current {@link ProtocolDecoderOutput} used to write 
56       *        decoded messages.
57       * @return the next state if a state transition was triggered (use 
58       *         <code>this</code> for loop transitions) or <code>null</code> if 
59       *         the state machine has reached its end.
60       * @throws Exception if the read data violated protocol specification.
61       */
62      protected abstract DecodingState finishDecode(byte b,
63              ProtocolDecoderOutput out) throws Exception;
64  }