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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.common.IoBuffer;
23  import org.apache.mina.filter.codec.ProtocolDecoderException;
24  import org.apache.mina.filter.codec.ProtocolDecoderOutput;
25  
26  /**
27   * Decodes a single <code>CRLF</code>.
28   * If it is found, the bytes are consumed and <code>Boolean.TRUE</code>
29   * is provided as the product. Otherwise, read bytes are pushed back
30   * to the stream, and <code>Boolean.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: 601994 $, $Date: 2007-12-06 21:58:00 -0700 (Thu, 06 Dec 2007) $
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      public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
52              throws Exception {
53          boolean found = false;
54          boolean finished = false;
55          while (in.hasRemaining()) {
56              byte b = in.get();
57              if (!hasCR) {
58                  if (b == CR) {
59                      hasCR = true;
60                  } else {
61                      if (b == LF) {
62                          found = true;
63                      } else {
64                          in.position(in.position() - 1);
65                          found = false;
66                      }
67                      finished = true;
68                      break;
69                  }
70              } else {
71                  if (b == LF) {
72                      found = true;
73                      finished = true;
74                      break;
75                  } else {
76                      throw new ProtocolDecoderException(
77                              "Expected LF after CR but was: " + (b & 0xff));
78                  }
79              }
80          }
81  
82          if (finished) {
83              hasCR = false;
84              return finishDecode(found, out);
85          } else {
86              return this;
87          }
88      }
89  
90      public DecodingState finishDecode(ProtocolDecoderOutput out)
91              throws Exception {
92          return finishDecode(false, out);
93      }
94  
95      protected abstract DecodingState finishDecode(boolean foundCRLF,
96              ProtocolDecoderOutput out) throws Exception;
97  }