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>short</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 ShortIntegerDecodingState implements DecodingState {
33 private int counter;
34
35 /**
36 * {@inheritDoc}
37 */
38 @Override
39 public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out) throws Exception {
40 int highByte = 0;
41
42
43 while (in.hasRemaining()) {
44 switch (counter) {
45 case 0:
46 highByte = in.getUnsigned();
47 break;
48
49 case 1:
50 counter = 0;
51 return finishDecode((short) ((highByte << 8) | in.getUnsigned()), out);
52
53 default:
54 throw new InternalError();
55 }
56
57 counter++;
58 }
59 return this;
60 }
61
62 /**
63 * {@inheritDoc}
64 */
65 @Override
66 public DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception {
67 throw new ProtocolDecoderException("Unexpected end of session while waiting for a short integer.");
68 }
69
70 /**
71 * Invoked when this state has consumed a complete <code>short</code>.
72 *
73 * @param value the short.
74 * @param out the current {@link ProtocolDecoderOutput} used to write
75 * decoded messages.
76 * @return the next state if a state transition was triggered (use
77 * <code>this</code> for loop transitions) or <code>null</code> if
78 * the state machine has reached its end.
79 * @throws Exception if the read data violated protocol specification.
80 */
81 protected abstract DecodingState finishDecode(short value, ProtocolDecoderOutput out) throws Exception;
82 }