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 skips data until {@link #canSkip(byte)} returns
27 * <tt>false</tt>.
28 *
29 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
30 */
31 public abstract class SkippingState implements DecodingState {
32
33 private int skippedBytes;
34
35 /**
36 * {@inheritDoc}
37 */
38 public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out)
39 throws Exception {
40 int beginPos = in.position();
41 int limit = in.limit();
42 for (int i = beginPos; i < limit; i++) {
43 byte b = in.get(i);
44 if (!canSkip(b)) {
45 in.position(i);
46 int answer = this.skippedBytes;
47 this.skippedBytes = 0;
48 return finishDecode(answer);
49 }
50
51 skippedBytes++;
52 }
53
54 in.position(limit);
55 return this;
56 }
57
58 /**
59 * {@inheritDoc}
60 */
61 public DecodingState finishDecode(ProtocolDecoderOutput out)
62 throws Exception {
63 return finishDecode(skippedBytes);
64 }
65
66 /**
67 * Called to determine whether the specified byte can be skipped.
68 *
69 * @param b the byte to check.
70 * @return <code>true</code> if the byte can be skipped.
71 */
72 protected abstract boolean canSkip(byte b);
73
74 /**
75 * Invoked when this state cannot skip any more bytes.
76 *
77 * @param skippedBytes the number of bytes skipped.
78 * @return the next state if a state transition was triggered (use
79 * <code>this</code> for loop transitions) or <code>null</code> if
80 * the state machine has reached its end.
81 * @throws Exception if the read data violated protocol specification.
82 */
83 protected abstract DecodingState finishDecode(int skippedBytes)
84 throws Exception;
85 }