1 /*
2 * Copyright 2012 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the 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.buffer.ChannelBufferFactory;
20 import org.jboss.netty.channel.Channel;
21 import org.jboss.netty.channel.ChannelHandlerContext;
22
23 /**
24 * A decoder that splits the received {@link ChannelBuffer}s by the fixed number
25 * of bytes. For example, if you received the following four fragmented packets:
26 * <pre>
27 * +---+----+------+----+
28 * | A | BC | DEFG | HI |
29 * +---+----+------+----+
30 * </pre>
31 * A {@link FixedLengthFrameDecoder}{@code (3)} will decode them into the
32 * following three packets with the fixed length:
33 * <pre>
34 * +-----+-----+-----+
35 * | ABC | DEF | GHI |
36 * +-----+-----+-----+
37 * </pre>
38 */
39 public class FixedLengthFrameDecoder extends FrameDecoder {
40
41 private final int frameLength;
42 private final boolean allocateFullBuffer;
43
44 /**
45 * Calls {@link #FixedLengthFrameDecoder(int, boolean)} with {@code false}
46 */
47 public FixedLengthFrameDecoder(int frameLength) {
48 this(frameLength, false);
49 }
50
51 /**
52 * Creates a new instance.
53 *
54 * @param frameLength
55 * the length of the frame
56 * @param allocateFullBuffer
57 * {@code true} if the cumulative {@link ChannelBuffer} should use the
58 * {@link #frameLength} as its initial size
59 */
60 public FixedLengthFrameDecoder(int frameLength, boolean allocateFullBuffer) {
61 if (frameLength <= 0) {
62 throw new IllegalArgumentException(
63 "frameLength must be a positive integer: " + frameLength);
64 }
65 this.frameLength = frameLength;
66 this.allocateFullBuffer = allocateFullBuffer;
67 }
68
69 @Override
70 protected Object decode(
71 ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
72 if (buffer.readableBytes() < frameLength) {
73 return null;
74 } else {
75 ChannelBuffer frame = extractFrame(buffer, buffer.readerIndex(), frameLength);
76 buffer.skipBytes(frameLength);
77 return frame;
78 }
79 }
80
81 @Override
82 protected ChannelBuffer newCumulationBuffer(ChannelHandlerContext ctx, int minimumCapacity) {
83 ChannelBufferFactory factory = ctx.getChannel().getConfig().getBufferFactory();
84 if (allocateFullBuffer) {
85 return factory.getBuffer(frameLength);
86 }
87 return super.newCumulationBuffer(ctx, minimumCapacity);
88 }
89 }