/*
* Copyright 2012 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.handler.codec.protobuf;
import com.google.protobuf.CodedOutputStream;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufOutputStream;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
/**
* An encoder that prepends the the Google Protocol Buffers
* <a href="http://code.google.com/apis/protocolbuffers/docs/encoding.html#varints">Base
* 128 Varints</a> integer length field. For example:
* <pre>
* BEFORE DECODE (300 bytes) AFTER DECODE (302 bytes)
* +---------------+ +--------+---------------+
* | Protobuf Data |-------------->| Length | Protobuf Data |
* | (300 bytes) | | 0xAC02 | (300 bytes) |
* +---------------+ +--------+---------------+
* </pre> *
*
* @see CodedOutputStream
*/
@Sharable
public class ProtobufVarint32LengthFieldPrepender extends MessageToByteEncoder<ByteBuf> {
@Override
protected void encode(
ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception {
int bodyLen = msg.readableBytes();
int headerLen = CodedOutputStream.computeRawVarint32Size(bodyLen);
out.ensureWritable(headerLen + bodyLen);
CodedOutputStream headerOut =
CodedOutputStream.newInstance(new ByteBufOutputStream(out));
headerOut.writeRawVarint32(bodyLen);
headerOut.flush();
out.writeBytes(msg, msg.readerIndex(), bodyLen);
}
}