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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.core.buffer.IoBuffer;
23  import org.apache.mina.filter.codec.ProtocolDecoderOutput;
24  
25  /**
26   * {@link DecodingState} which consumes all bytes until a <code>CRLF</code> 
27   * has been encountered.
28   * 
29   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
30   */
31  public abstract class ConsumeToCrLfDecodingState implements DecodingState {
32  
33      /**
34       * Carriage return character
35       */
36      private static final byte CR = 13;
37  
38      /**
39       * Line feed character
40       */
41      private static final byte LF = 10;
42  
43      private boolean lastIsCR;
44  
45      private IoBuffer buffer;
46  
47      /**
48       * Creates a new instance.
49       */
50      public ConsumeToCrLfDecodingState() {
51          // Do nothing
52      }
53  
54      public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
55              throws Exception {
56          int beginPos = in.position();
57          int limit = in.limit();
58          int terminatorPos = -1;
59  
60          for (int i = beginPos; i < limit; i++) {
61              byte b = in.get(i);
62              if (b == CR) {
63                  lastIsCR = true;
64              } else {
65                  if (b == LF && lastIsCR) {
66                      terminatorPos = i;
67                      break;
68                  }
69                  lastIsCR = false;
70              }
71          }
72  
73          if (terminatorPos >= 0) {
74              IoBuffer product;
75  
76              int endPos = terminatorPos - 1;
77  
78              if (beginPos < endPos) {
79                  in.limit(endPos);
80  
81                  if (buffer == null) {
82                      product = in.slice();
83                  } else {
84                      buffer.put(in);
85                      product = buffer.flip();
86                      buffer = null;
87                  }
88  
89                  in.limit(limit);
90              } else {
91                  // When input contained only CR or LF rather than actual data...
92                  if (buffer == null) {
93                      product = IoBuffer.allocate(0);
94                  } else {
95                      product = buffer.flip();
96                      buffer = null;
97                  }
98              }
99              in.position(terminatorPos + 1);
100             return finishDecode(product, out);
101         }
102         
103         in.position(beginPos);
104         
105         if (buffer == null) {
106             buffer = IoBuffer.allocate(in.remaining());
107             buffer.setAutoExpand(true);
108         }
109 
110         buffer.put(in);
111         
112         if (lastIsCR) {
113             buffer.position(buffer.position() - 1);
114         }
115 
116         return this;
117     }
118 
119     /**
120      * {@inheritDoc}
121      */
122     public DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception {
123         IoBuffer product;
124         // When input contained only CR or LF rather than actual data...
125         if (buffer == null) {
126             product = IoBuffer.allocate(0);
127         } else {
128             product = buffer.flip();
129             buffer = null;
130         }
131         return finishDecode(product, out);
132     }
133 
134     /**
135      * Invoked when this state has reached a <code>CRLF</code>.
136      * 
137      * @param product the read bytes including the <code>CRLF</code>.
138      * @param out the current {@link ProtocolDecoderOutput} used to write 
139      *        decoded messages.
140      * @return the next state if a state transition was triggered (use 
141      *         <code>this</code> for loop transitions) or <code>null</code> if 
142      *         the state machine has reached its end.
143      * @throws Exception if the read data violated protocol specification.
144      */
145     protected abstract DecodingState finishDecode(IoBuffer product,
146             ProtocolDecoderOutput out) throws Exception;
147 }