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 import java.util.concurrent.ConcurrentLinkedQueue;
24
25 import org.apache.mina.core.buffer.IoBuffer;
26 import org.apache.mina.core.session.IoSession;
27 import org.apache.mina.filter.codec.ProtocolDecoder;
28 import org.apache.mina.filter.codec.ProtocolDecoderOutput;
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 <a href="http://mina.apache.org">Apache MINA Project</a>
39 */
40 public class DecodingStateProtocolDecoder implements ProtocolDecoder {
41 private final DecodingState state;
42
43 private final Queue<IoBuffer> undecodedBuffers = new ConcurrentLinkedQueue<>();
44
45 private IoSession session;
46
47 /**
48 * Creates a new instance using the specified {@link DecodingState}
49 * instance.
50 *
51 * @param state the {@link DecodingState}.
52 * @throws IllegalArgumentException if the specified state is <code>null</code>.
53 */
54 public DecodingStateProtocolDecoder(DecodingState state) {
55 if (state == null) {
56 throw new IllegalArgumentException("state");
57 }
58 this.state = state;
59 }
60
61 /**
62 * {@inheritDoc}
63 */
64 @Override
65 public void decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws Exception {
66 if (this.session == null) {
67 this.session = session;
68 } else if (this.session != session) {
69 throw new IllegalStateException(getClass().getSimpleName() + " is a stateful decoder. "
70 + "You have to create one per session.");
71 }
72
73 undecodedBuffers.offer(in);
74
75 for (;;) {
76 IoBuffer b = undecodedBuffers.peek();
77 if (b == null) {
78 break;
79 }
80
81 int oldRemaining = b.remaining();
82 state.decode(b, out);
83 int newRemaining = b.remaining();
84
85 if (newRemaining != 0) {
86 if (oldRemaining == newRemaining) {
87 throw new IllegalStateException(DecodingState.class.getSimpleName() + " must "
88 + "consume at least one byte per decode().");
89 }
90 } else {
91 undecodedBuffers.poll();
92 }
93 }
94 }
95
96 /**
97 * {@inheritDoc}
98 */
99 @Override
100 public void finishDecode(IoSession session, ProtocolDecoderOutput out) throws Exception {
101 state.finishDecode(out);
102 }
103
104 /**
105 * {@inheritDoc}
106 */
107 @Override
108 public void dispose(IoSession session) throws Exception {
109 // Do nothing
110 }
111 }