/*
* 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.CodedInputStream;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import io.netty.handler.codec.CorruptedFrameException;
/**
* A decoder that splits the received {@link ByteBuf}s dynamically by the
* value of the Google Protocol Buffers
* <a href="http://code.google.com/apis/protocolbuffers/docs/encoding.html#varints">Base
* 128 Varints</a> integer length field in the message. For example:
* <pre>
* BEFORE DECODE (302 bytes) AFTER DECODE (300 bytes)
* +--------+---------------+ +---------------+
* | Length | Protobuf Data |----->| Protobuf Data |
* | 0xAC02 | (300 bytes) | | (300 bytes) |
* +--------+---------------+ +---------------+
* </pre>
*
* @see CodedInputStream
*/
public class ProtobufVarint32FrameDecoder extends ByteToMessageDecoder {
// TODO maxFrameLength + safe skip + fail-fast option
// (just like LengthFieldBasedFrameDecoder)
@Override
protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
in.markReaderIndex();
final byte[] buf = new byte[5];
for (int i = 0; i < buf.length; i ++) {
if (!in.isReadable()) {
in.resetReaderIndex();
return null;
}
buf[i] = in.readByte();
if (buf[i] >= 0) {
int length = CodedInputStream.newInstance(buf, 0, i + 1).readRawVarint32();
if (length < 0) {
throw new CorruptedFrameException("negative length: " + length);
}
if (in.readableBytes() < length) {
in.resetReaderIndex();
return null;
} else {
return in.readBytes(length);
}
}
}
// Couldn't find the byte whose MSB is off.
throw new CorruptedFrameException("length wider than 32-bit");
}
}