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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.filter.codec.ProtocolDecoderException;
24  import org.apache.mina.filter.codec.ProtocolDecoderOutput;
25  
26  /**
27   * {@link DecodingState} which decodes <code>int</code> values in big-endian 
28   * order (high bytes come first).
29   * 
30   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
31   */
32  public abstract class IntegerDecodingState implements DecodingState {
33      
34      private int firstByte;
35      private int secondByte;
36      private int thirdByte;
37      private int counter;
38  
39      /**
40       * {@inheritDoc}
41       */
42      public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
43              throws Exception {
44          while (in.hasRemaining()) {
45              switch (counter) {
46              case 0:
47                  firstByte = in.getUnsigned();
48                  break;
49              case 1:
50                  secondByte = in.getUnsigned();
51                  break;
52              case 2:
53                  thirdByte = in.getUnsigned();
54                  break;
55              case 3:
56                  counter = 0;
57                  return finishDecode(
58                          (firstByte << 24) | (secondByte << 16) | (thirdByte << 8) | in.getUnsigned(),
59                          out);
60              default:
61                  throw new InternalError();
62              }
63              counter ++;
64          }
65  
66          return this;
67      }
68  
69      /**
70       * {@inheritDoc}
71       */
72      public DecodingState finishDecode(ProtocolDecoderOutput out)
73              throws Exception {
74          throw new ProtocolDecoderException(
75                  "Unexpected end of session while waiting for an integer.");
76      }
77  
78      /**
79       * Invoked when this state has consumed a complete <code>int</code>.
80       * 
81       * @param value the integer.
82       * @param out the current {@link ProtocolDecoderOutput} used to write 
83       *        decoded messages.
84       * @return the next state if a state transition was triggered (use 
85       *         <code>this</code> for loop transitions) or <code>null</code> if 
86       *         the state machine has reached its end.
87       * @throws Exception if the read data violated protocol specification.
88       */
89      protected abstract DecodingState finishDecode(int value,
90              ProtocolDecoderOutput out) throws Exception;
91  }