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.ProtocolDecoderOutput;
24
25 /**
26 * {@link DecodingState} which consumes all received bytes until a configured
27 * number of read bytes has been reached. Please note that this state can
28 * produce a buffer with less data than the configured length if the associated
29 * session has been closed unexpectedly.
30 *
31 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
32 */
33 public abstract class FixedLengthDecodingState implements DecodingState {
34
35 private final int length;
36
37 private IoBuffer buffer;
38
39 /**
40 * Constructs a new instance using the specified decode length.
41 *
42 * @param length the number of bytes to read.
43 */
44 public FixedLengthDecodingState(int length) {
45 this.length = length;
46 }
47
48 /**
49 * {@inheritDoc}
50 */
51 @Override
52 public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out) throws Exception {
53 if (buffer == null) {
54 if (in.remaining() >= length) {
55 int limit = in.limit();
56 in.limit(in.position() + length);
57 IoBuffer product = in.slice();
58 in.position(in.position() + length);
59 in.limit(limit);
60
61 return finishDecode(product, out);
62 }
63
64 buffer = IoBuffer.allocate(length);
65 buffer.put(in);
66
67 return this;
68 }
69
70 if (in.remaining() >= length - buffer.position()) {
71 int limit = in.limit();
72 in.limit(in.position() + length - buffer.position());
73 buffer.put(in);
74 in.limit(limit);
75 IoBuffer product = this.buffer;
76 this.buffer = null;
77
78 return finishDecode(product.flip(), out);
79 }
80
81 buffer.put(in);
82 return this;
83 }
84
85 /**
86 * {@inheritDoc}
87 */
88 @Override
89 public DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception {
90 IoBuffer readData;
91
92 if (buffer == null) {
93 readData = IoBuffer.allocate(0);
94 } else {
95 readData = buffer.flip();
96 buffer = null;
97 }
98
99 return finishDecode(readData, out);
100 }
101
102 /**
103 * Invoked when this state has consumed the configured number of bytes.
104 *
105 * @param product the data.
106 * @param out the current {@link ProtocolDecoderOutput} used to write
107 * decoded messages.
108 * @return the next state if a state transition was triggered (use
109 * <code>this</code> for loop transitions) or <code>null</code> if
110 * the state machine has reached its end.
111 * @throws Exception if the read data violated protocol specification.
112 */
113 protected abstract DecodingState finishDecode(IoBuffer product, ProtocolDecoderOutput out) throws Exception;
114 }