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.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 CodedInputStream
40 */
41 public class ProtobufVarint32FrameDecoder extends FrameDecoder {
42
43 // TODO maxFrameLength + safe skip + fail-fast option
44 // (just like LengthFieldBasedFrameDecoder)
45
46 @Override
47 protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
48 buffer.markReaderIndex();
49 final byte[] buf = new byte[5];
50 for (int i = 0; i < buf.length; i ++) {
51 if (!buffer.readable()) {
52 buffer.resetReaderIndex();
53 return null;
54 }
55
56 buf[i] = buffer.readByte();
57 if (buf[i] >= 0) {
58 int length = CodedInputStream.newInstance(buf, 0, i + 1).readRawVarint32();
59 if (length < 0) {
60 throw new CorruptedFrameException("negative length: " + length);
61 }
62
63 if (buffer.readableBytes() < length) {
64 buffer.resetReaderIndex();
65 return null;
66 } else {
67 return buffer.readBytes(length);
68 }
69 }
70 }
71
72 // Couldn't find the byte whose MSB is off.
73 throw new CorruptedFrameException("length wider than 32-bit");
74 }
75 }