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 The Apache MINA Project (dev@mina.apache.org)
32 * @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (jeu, 26 jun 2008) $
33 */
34 public abstract class FixedLengthDecodingState implements DecodingState {
35
36 private final int length;
37
38 private IoBuffer buffer;
39
40 /**
41 * Constructs a new instance using the specified decode length.
42 *
43 * @param length the number of bytes to read.
44 */
45 public FixedLengthDecodingState(int length) {
46 this.length = length;
47 }
48
49 /**
50 * {@inheritDoc}
51 */
52 public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
53 throws Exception {
54 if (buffer == null) {
55 if (in.remaining() >= length) {
56 int limit = in.limit();
57 in.limit(in.position() + length);
58 IoBuffer product = in.slice();
59 in.position(in.position() + length);
60 in.limit(limit);
61 return finishDecode(product, out);
62 } else {
63 buffer = IoBuffer.allocate(length);
64 buffer.put(in);
65 return this;
66 }
67 } else {
68 if (in.remaining() >= length - buffer.position()) {
69 int limit = in.limit();
70 in.limit(in.position() + length - buffer.position());
71 buffer.put(in);
72 in.limit(limit);
73 IoBuffer product = this.buffer;
74 this.buffer = null;
75 return finishDecode(product.flip(), out);
76 } else {
77 buffer.put(in);
78 return this;
79 }
80 }
81 }
82
83 /**
84 * {@inheritDoc}
85 */
86 public DecodingState finishDecode(ProtocolDecoderOutput out)
87 throws Exception {
88 IoBuffer readData;
89 if (buffer == null) {
90 readData = IoBuffer.allocate(0);
91 } else {
92 readData = buffer.flip();
93 buffer = null;
94 }
95 return finishDecode(readData ,out);
96 }
97
98 /**
99 * Invoked when this state has consumed the configured number of bytes.
100 *
101 * @param product the data.
102 * @param out the current {@link ProtocolDecoderOutput} used to write
103 * decoded messages.
104 * @return the next state if a state transition was triggered (use
105 * <code>this</code> for loop transitions) or <code>null</code> if
106 * the state machine has reached its end.
107 * @throws Exception if the read data violated protocol specification.
108 */
109 protected abstract DecodingState finishDecode(IoBuffer product,
110 ProtocolDecoderOutput out) throws Exception;
111 }