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.codec.delimited;
21
22 import java.nio.ByteBuffer;
23
24 import org.apache.mina.codec.IoBuffer;
25 import org.apache.mina.codec.ProtocolDecoder;
26 import org.apache.mina.codec.ProtocolDecoderException;
27 import org.apache.mina.codec.StatelessProtocolDecoder;
28 import org.apache.mina.codec.delimited.ints.RawInt32;
29 import org.apache.mina.codec.delimited.ints.VarInt;
30
31 /**
32 * Abstract class providing both encoding and decoding methods between a given
33 * type and ByteBuffers.
34 *
35 * <p>
36 * Transcoder is stateless class providing encoding and decoding facilities.
37 * Additionally this abstract requires two methods which allows to determine the
38 * size of a given message and to write it directly to a previously allocated
39 * ByteBuffer.
40 * </p>
41 *
42 * @param <INPUT>
43 * the type of the messages which will be encoded in ByteBuffers and
44 * decoded from ByteBuffers.
45 *
46 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
47 */
48 public abstract class IoBufferDecoder<INPUT> implements StatelessProtocolDecoder<IoBuffer, INPUT> {
49 /**
50 * Being stateless, this method is left empty
51 *
52 * @see ProtocolDecoder#createDecoderState()
53 */
54 @Override
55 public final Void createDecoderState() {
56 // stateless !
57 return null;
58 }
59
60 /**
61 * Decodes a message from a {@link IoBuffer}
62 *
63 * <p>
64 * When a truncated input is given to this method it <b>may</b> return null.
65 * Not all decoder will be able to detect this issue and report it that way.
66 * Thanks to prefixing of messages, decoder will only receive appropriately
67 * sized ByteBuffers.
68 * </p>
69 *
70 * <p>
71 * n.b. The decoders used for the prefixing (i.e. {@link RawInt32} and
72 * {@link VarInt}) <b>have</b> to detect truncated ByteBuffers.
73 * </p>
74 *
75 * @param input
76 * data to be decoded as a TYPE message
77 * @return the decoded message on success, null otherwise
78 *
79 * @throws ProtocolDecoderException
80 */
81 public abstract INPUT decode(IoBuffer input);
82
83 /**
84 * Decodes a message from a {@link ByteBuffer}
85 * <p>
86 * The actual decoding needs to be implemented in the abstract method
87 * {@link IoBufferDecoder#decode(ByteBuffer)}
88 * </p>
89 */
90 @Override
91 public final INPUT decode(IoBuffer input, Void context) {
92 return decode(input);
93 }
94
95 /**
96 * Being stateless, this method is left empty
97 *
98 * @see ProtocolDecoder#finishDecode(Object)
99 */
100 @Override
101 public final void finishDecode(Void context) {
102 // stateless !
103 }
104
105 }