1 /*
2 * Copyright 2009 Red Hat, Inc.
3 *
4 * Red Hat licenses this file to you under the Apache License, version 2.0
5 * (the "License"); you may not use this file except in compliance with the
6 * License. You may obtain a copy of the License at:
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package org.jboss.netty.handler.codec.frame;
17
18 import org.jboss.netty.buffer.ChannelBuffer;
19 import org.jboss.netty.channel.Channel;
20 import org.jboss.netty.channel.ChannelHandlerContext;
21
22 /**
23 * A decoder that splits the received {@link ChannelBuffer}s by the fixed number
24 * of bytes. For example, if you received the following four fragmented packets:
25 * <pre>
26 * +---+----+------+----+
27 * | A | BC | DEFG | HI |
28 * +---+----+------+----+
29 * </pre>
30 * A {@link FixedLengthFrameDecoder}{@code (3)} will decode them into the
31 * following three packets with the fixed length:
32 * <pre>
33 * +-----+-----+-----+
34 * | ABC | DEF | GHI |
35 * +-----+-----+-----+
36 * </pre>
37 *
38 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
39 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
40 *
41 * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
42 */
43 public class FixedLengthFrameDecoder extends FrameDecoder {
44
45 private final int frameLength;
46
47 /**
48 * Creates a new instance.
49 *
50 * @param frameLength the length of the frame
51 */
52 public FixedLengthFrameDecoder(int frameLength) {
53 if (frameLength <= 0) {
54 throw new IllegalArgumentException(
55 "frameLength must be a positive integer: " + frameLength);
56 }
57 this.frameLength = frameLength;
58 }
59
60 @Override
61 protected Object decode(
62 ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
63 if (buffer.readableBytes() < frameLength) {
64 return null;
65 } else {
66 return buffer.readBytes(frameLength);
67 }
68 }
69 }