/*
* Copyright 2015 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 com.google.protobuf.nano.CodedOutputByteBufferNano;
import io.netty.buffer.ByteBuf;
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="https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints">Base
* 128 Varints</a> integer length field. For example:
* <pre>
* BEFORE ENCODE (300 bytes) AFTER ENCODE (302 bytes)
* +---------------+ +--------+---------------+
* | Protobuf Data |-------------->| Length | Protobuf Data |
* | (300 bytes) | | 0xAC02 | (300 bytes) |
* +---------------+ +--------+---------------+
* </pre> *
*
* @see CodedOutputStream
* @see CodedOutputByteBufferNano
*/
@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 = computeRawVarint32Size(bodyLen);
out.ensureWritable(headerLen + bodyLen);
writeRawVarint32(out, bodyLen);
out.writeBytes(msg, msg.readerIndex(), bodyLen);
}
/**
* Writes protobuf varint32 to (@link ByteBuf).
* @param out to be written to
* @param value to be written
*/
static void writeRawVarint32(ByteBuf out, int value) {
while (true) {
if ((value & ~0x7F) == 0) {
out.writeByte(value);
return;
} else {
out.writeByte((value & 0x7F) | 0x80);
value >>>= 7;
}
}
}
/**
* Computes size of protobuf varint32 after encoding.
* @param value which is to be encoded.
* @return size of value encoded as protobuf varint32.
*/
static int computeRawVarint32Size(final int value) {
if ((value & (0xffffffff << 7)) == 0) {
return 1;
}
if ((value & (0xffffffff << 14)) == 0) {
return 2;
}
if ((value & (0xffffffff << 21)) == 0) {
return 3;
}
if ((value & (0xffffffff << 28)) == 0) {
return 4;
}
return 5;
}
}