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 java.util.Queue;
23
24 import org.apache.mina.core.buffer.IoBuffer;
25 import org.apache.mina.core.session.IoSession;
26 import org.apache.mina.filter.codec.ProtocolDecoder;
27 import org.apache.mina.filter.codec.ProtocolDecoderOutput;
28 import org.apache.mina.util.CircularQueue;
29
30 /**
31 * {@link ProtocolDecoder} which uses a {@link DecodingState} to decode data.
32 * Use a {@link DecodingStateMachine} as {@link DecodingState} to create
33 * a state machine which can decode your protocol.
34 * <p>
35 * NOTE: This is a stateful decoder. You should create one instance per session.
36 * </p>
37 *
38 * @author The Apache MINA Project (dev@mina.apache.org)
39 * @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (jeu, 26 jun 2008) $
40 */
41 public class DecodingStateProtocolDecoder implements ProtocolDecoder {
42 private final DecodingState state;
43 private final Queue<IoBuffer> undecodedBuffers = new CircularQueue<IoBuffer>();
44 private IoSession session;
45
46 /**
47 * Creates a new instance using the specified {@link DecodingState}
48 * instance.
49 *
50 * @param state the {@link DecodingState}.
51 * @throws NullPointerException if the specified state is <code>null</code>.
52 */
53 public DecodingStateProtocolDecoder(DecodingState state) {
54 if (state == null) {
55 throw new NullPointerException("state");
56 }
57 this.state = state;
58 }
59
60 /**
61 * {@inheritDoc}
62 */
63 public void decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out)
64 throws Exception {
65 if (this.session == null) {
66 this.session = session;
67 } else if (this.session != session) {
68 throw new IllegalStateException(
69 getClass().getSimpleName() + " is a stateful decoder. " +
70 "You have to create one per session.");
71 }
72
73 undecodedBuffers.offer(in);
74 for (;;) {
75 IoBuffer b = undecodedBuffers.peek();
76 if (b == null) {
77 break;
78 }
79
80 int oldRemaining = b.remaining();
81 state.decode(b, out);
82 int newRemaining = b.remaining();
83 if (newRemaining != 0) {
84 if (oldRemaining == newRemaining) {
85 throw new IllegalStateException(
86 DecodingState.class.getSimpleName() + " must " +
87 "consume at least one byte per decode().");
88 }
89 } else {
90 undecodedBuffers.poll();
91 }
92 }
93 }
94
95 /**
96 * {@inheritDoc}
97 */
98 public void finishDecode(IoSession session, ProtocolDecoderOutput out)
99 throws Exception {
100 state.finishDecode(out);
101 }
102
103 /**
104 * {@inheritDoc}
105 */
106 public void dispose(IoSession session) throws Exception {}
107 }