io.netty.handler.codec.protobuf.ProtobufVarint32LengthFieldPrepender Maven / Gradle / Ivy
/*
* 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
* Base
* 128 Varints integer length field. For example:
*
* BEFORE DECODE (300 bytes) AFTER DECODE (302 bytes)
* +---------------+ +--------+---------------+
* | Protobuf Data |-------------->| Length | Protobuf Data |
* | (300 bytes) | | 0xAC02 | (300 bytes) |
* +---------------+ +--------+---------------+
*
*
*
* @see CodedOutputStream
*/
@Sharable
public class ProtobufVarint32LengthFieldPrepender extends MessageToByteEncoder {
@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), headerLen);
headerOut.writeRawVarint32(bodyLen);
headerOut.flush();
out.writeBytes(msg, msg.readerIndex(), bodyLen);
}
}