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.protobuf;
17
18 import org.jboss.netty.buffer.ChannelBuffer;
19 import org.jboss.netty.channel.Channel;
20 import org.jboss.netty.channel.ChannelHandlerContext;
21 import org.jboss.netty.handler.codec.frame.CorruptedFrameException;
22 import org.jboss.netty.handler.codec.frame.FrameDecoder;
23
24 import com.google.protobuf.CodedInputStream;
25
26 /**
27 * A decoder that splits the received {@link ChannelBuffer}s dynamically by the
28 * value of the Google Protocol Buffers
29 * <a href="http://code.google.com/apis/protocolbuffers/docs/encoding.html#varints">Base
30 * 128 Varints</a> integer length field in the message. For example:
31 * <pre>
32 * BEFORE DECODE (302 bytes) AFTER DECODE (300 bytes)
33 * +--------+---------------+ +---------------+
34 * | Length | Protobuf Data |----->| Protobuf Data |
35 * | 0xAC02 | (300 bytes) | | (300 bytes) |
36 * +--------+---------------+ +---------------+
37 * </pre>
38 *
39 * @see com.google.protobuf.CodedInputStream
40 *
41 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
42 * @author Tomasz Blachowicz (tblachowicz@gmail.com)
43 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
44 *
45 * @version $Rev: 2323 $, $Date: 2010-06-24 11:13:12 +0900 (Thu, 24 Jun 2010) $
46 */
47 public class ProtobufVarint32FrameDecoder extends FrameDecoder {
48
49 // TODO maxFrameLength + safe skip + fail-fast option
50 // (just like LengthFieldBasedFrameDecoder)
51
52 /**
53 * Creates a new instance.
54 */
55 public ProtobufVarint32FrameDecoder() {
56 super();
57 }
58
59 @Override
60 protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
61 buffer.markReaderIndex();
62 final byte[] buf = new byte[5];
63 for (int i = 0; i < buf.length; i ++) {
64 if (!buffer.readable()) {
65 buffer.resetReaderIndex();
66 return null;
67 }
68
69 buf[i] = buffer.readByte();
70 if (buf[i] >= 0) {
71 int length = CodedInputStream.newInstance(buf, 0, i + 1).readRawVarint32();
72 if (length < 0) {
73 throw new CorruptedFrameException("negative length: " + length);
74 }
75
76 if (buffer.readableBytes() < length) {
77 buffer.resetReaderIndex();
78 return null;
79 } else {
80 return buffer.readBytes(length);
81 }
82 }
83 }
84
85 // Couldn't find the byte whose MSB is off.
86 throw new CorruptedFrameException("length wider than 32-bit");
87 }
88 }