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 static org.jboss.netty.buffer.ChannelBuffers.*;
19
20 import org.jboss.netty.buffer.ChannelBuffer;
21 import org.jboss.netty.buffer.ChannelBufferOutputStream;
22 import org.jboss.netty.channel.Channel;
23 import org.jboss.netty.channel.ChannelHandler.Sharable;
24 import org.jboss.netty.channel.ChannelHandlerContext;
25 import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
26
27 import com.google.protobuf.CodedOutputStream;
28
29 /**
30 * An encoder that prepends the the Google Protocol Buffers
31 * <a href="http://code.google.com/apis/protocolbuffers/docs/encoding.html#varints">Base
32 * 128 Varints</a> integer length field. For example:
33 * <pre>
34 * BEFORE DECODE (300 bytes) AFTER DECODE (302 bytes)
35 * +---------------+ +--------+---------------+
36 * | Protobuf Data |-------------->| Length | Protobuf Data |
37 * | (300 bytes) | | 0xAC02 | (300 bytes) |
38 * +---------------+ +--------+---------------+
39 * </pre> *
40 *
41 * @see com.google.protobuf.CodedOutputStream
42 */
43 @Sharable
44 public class ProtobufVarint32LengthFieldPrepender extends OneToOneEncoder {
45
46 @Override
47 protected Object encode(ChannelHandlerContext ctx, Channel channel,
48 Object msg) throws Exception {
49 if (!(msg instanceof ChannelBuffer)) {
50 return msg;
51 }
52
53 ChannelBuffer body = (ChannelBuffer) msg;
54 int length = body.readableBytes();
55 ChannelBuffer header =
56 channel.getConfig().getBufferFactory().getBuffer(
57 body.order(),
58 CodedOutputStream.computeRawVarint32Size(length));
59 CodedOutputStream codedOutputStream = CodedOutputStream
60 .newInstance(new ChannelBufferOutputStream(header));
61 codedOutputStream.writeRawVarint32(length);
62 codedOutputStream.flush();
63 return wrappedBuffer(header, body);
64 }
65
66 }