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 a single <code>CRLF</code>.
28 * If it is found, the bytes are consumed and <code>true</code>
29 * is provided as the product. Otherwise, read bytes are pushed back
30 * to the stream, and <code>false</code> is provided as the
31 * product.
32 * Note that if we find a CR but do not find a following LF, we raise
33 * an error.
34 *
35 * @author The Apache MINA Project (dev@mina.apache.org)
36 * @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (jeu, 26 jun 2008) $
37 */
38 public abstract class CrLfDecodingState implements DecodingState {
39 /**
40 * Carriage return character
41 */
42 private static final byte CR = 13;
43
44 /**
45 * Line feed character
46 */
47 private static final byte LF = 10;
48
49 private boolean hasCR;
50
51 /**
52 * {@inheritDoc}
53 */
54 public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
55 throws Exception {
56 boolean found = false;
57 boolean finished = false;
58 while (in.hasRemaining()) {
59 byte b = in.get();
60 if (!hasCR) {
61 if (b == CR) {
62 hasCR = true;
63 } else {
64 if (b == LF) {
65 found = true;
66 } else {
67 in.position(in.position() - 1);
68 found = false;
69 }
70 finished = true;
71 break;
72 }
73 } else {
74 if (b == LF) {
75 found = true;
76 finished = true;
77 break;
78 } else {
79 throw new ProtocolDecoderException(
80 "Expected LF after CR but was: " + (b & 0xff));
81 }
82 }
83 }
84
85 if (finished) {
86 hasCR = false;
87 return finishDecode(found, out);
88 } else {
89 return this;
90 }
91 }
92
93 /**
94 * {@inheritDoc}
95 */
96 public DecodingState finishDecode(ProtocolDecoderOutput out)
97 throws Exception {
98 return finishDecode(false, out);
99 }
100
101 /**
102 * Invoked when this state has found a <code>CRLF</code>.
103 *
104 * @param foundCRLF <code>true</code> if <code>CRLF</code> was found.
105 * @param out the current {@link ProtocolDecoderOutput} used to write
106 * decoded messages.
107 * @return the next state if a state transition was triggered (use
108 * <code>this</code> for loop transitions) or <code>null</code> if
109 * the state machine has reached its end.
110 * @throws Exception if the read data violated protocol specification.
111 */
112 protected abstract DecodingState finishDecode(boolean foundCRLF,
113 ProtocolDecoderOutput out) throws Exception;
114 }