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 io.netty.handler.codec.protobuf;
17
18 import com.google.protobuf.CodedOutputStream;
19 import io.netty.buffer.ByteBuf;
20 import io.netty.buffer.ByteBufOutputStream;
21 import io.netty.channel.ChannelHandler.Sharable;
22 import io.netty.channel.ChannelHandlerContext;
23 import io.netty.handler.codec.MessageToByteEncoder;
24
25 /**
26 * An encoder that prepends the the Google Protocol Buffers
27 * <a href="https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints">Base
28 * 128 Varints</a> integer length field. For example:
29 * <pre>
30 * BEFORE DECODE (300 bytes) AFTER DECODE (302 bytes)
31 * +---------------+ +--------+---------------+
32 * | Protobuf Data |-------------->| Length | Protobuf Data |
33 * | (300 bytes) | | 0xAC02 | (300 bytes) |
34 * +---------------+ +--------+---------------+
35 * </pre> *
36 *
37 * @see CodedOutputStream
38 */
39 @Sharable
40 public class ProtobufVarint32LengthFieldPrepender extends MessageToByteEncoder<ByteBuf> {
41
42 @Override
43 protected void encode(
44 ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception {
45 int bodyLen = msg.readableBytes();
46 int headerLen = CodedOutputStream.computeRawVarint32Size(bodyLen);
47 out.ensureWritable(headerLen + bodyLen);
48
49 CodedOutputStream headerOut =
50 CodedOutputStream.newInstance(new ByteBufOutputStream(out), headerLen);
51 headerOut.writeRawVarint32(bodyLen);
52 headerOut.flush();
53
54 out.writeBytes(msg, msg.readerIndex(), bodyLen);
55 }
56 }