org.apache.drill.exec.rpc.ZeroCopyProtobufLengthDecoder.java Source code

Introduction

Here is the source code for org.apache.drill.exec.rpc.ZeroCopyProtobufLengthDecoder.java

Source

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 org.apache.drill.exec.rpc;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import io.netty.handler.codec.CorruptedFrameException;

import java.util.List;

import com.google.protobuf.CodedInputStream;

/**
 * Modified version of ProtobufVarint32FrameDecoder that avoids bytebuf copy.
 */
public class ZeroCopyProtobufLengthDecoder extends ByteToMessageDecoder {
    static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ZeroCopyProtobufLengthDecoder.class);

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {

        if (!ctx.channel().isOpen()) {
            if (in.readableBytes() > 0)
                logger.info("Channel is closed, discarding remaining {} byte(s) in buffer.", in.readableBytes());
            in.skipBytes(in.readableBytes());
            return;
        }

        in.markReaderIndex();
        final byte[] buf = new byte[5];
        for (int i = 0; i < buf.length; i++) {
            if (!in.isReadable()) {
                in.resetReaderIndex();
                return;
            }

            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 (length == 0) {
                    throw new CorruptedFrameException("Received a message of length 0.");
                }

                if (in.readableBytes() < length) {
                    in.resetReaderIndex();
                    return;
                } else {
                    // need to make buffer copy, otherwise netty will try to refill this buffer if we move the readerIndex forward...
                    // TODO: Can we avoid this copy?
                    ByteBuf outBuf = in.copy(in.readerIndex(), length);
                    in.skipBytes(length);

                    if (RpcConstants.EXTRA_DEBUGGING)
                        logger.debug(String.format(
                                "ReaderIndex is %d after length header of %d bytes and frame body of length %d bytes.",
                                in.readerIndex(), i + 1, length));
                    out.add(outBuf);
                    return;
                }
            }
        }

        // Couldn't find the byte whose MSB is off.
        throw new CorruptedFrameException("length wider than 32-bit");

    }

}