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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 fixed (ASCII) 
27   * character is reached. The terminator is skipped.
28   *
29   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
30   */
31  public abstract class ConsumeToDynamicTerminatorDecodingState implements DecodingState {
32  
33      private IoBuffer buffer;
34  
35      /**
36       * {@inheritDoc}
37       */
38      public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out) throws Exception {
39          int beginPos = in.position();
40          int terminatorPos = -1;
41          int limit = in.limit();
42  
43          for (int i = beginPos; i < limit; i++) {
44              byte b = in.get(i);
45              if (isTerminator(b)) {
46                  terminatorPos = i;
47                  break;
48              }
49          }
50  
51          if (terminatorPos >= 0) {
52              IoBuffer product;
53  
54              if (beginPos < terminatorPos) {
55                  in.limit(terminatorPos);
56  
57                  if (buffer == null) {
58                      product = in.slice();
59                  } else {
60                      buffer.put(in);
61                      product = buffer.flip();
62                      buffer = null;
63                  }
64  
65                  in.limit(limit);
66              } else {
67                  // When input contained only terminator rather than actual data...
68                  if (buffer == null) {
69                      product = IoBuffer.allocate(0);
70                  } else {
71                      product = buffer.flip();
72                      buffer = null;
73                  }
74              }
75              in.position(terminatorPos + 1);
76              return finishDecode(product, out);
77          }
78  
79          if (buffer == null) {
80              buffer = IoBuffer.allocate(in.remaining());
81              buffer.setAutoExpand(true);
82          }
83          buffer.put(in);
84          return this;
85      }
86  
87      /**
88       * {@inheritDoc}
89       */
90      public DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception {
91          IoBuffer product;
92          // When input contained only terminator rather than actual data...
93          if (buffer == null) {
94              product = IoBuffer.allocate(0);
95          } else {
96              product = buffer.flip();
97              buffer = null;
98          }
99          return finishDecode(product, out);
100     }
101 
102     /**
103      * Determines whether the specified <code>byte</code> is a terminator.
104      * 
105      * @param b the <code>byte</code> to check.
106      * @return <code>true</code> if <code>b</code> is a terminator, 
107      *         <code>false</code> otherwise.
108      */
109     protected abstract boolean isTerminator(byte b);
110 
111     /**
112      * Invoked when this state has reached the terminator byte.
113      * 
114      * @param product the read bytes not including the terminator.
115      * @param out the current {@link ProtocolDecoderOutput} used to write 
116      *        decoded messages.
117      * @return the next state if a state transition was triggered (use 
118      *         <code>this</code> for loop transitions) or <code>null</code> if 
119      *         the state machine has reached its end.
120      * @throws Exception if the read data violated protocol specification.
121      */
122     protected abstract DecodingState finishDecode(IoBuffer product, ProtocolDecoderOutput out) throws Exception;
123 }