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    • net.dongliu.prettypb.rpc.coder.VarIntFrameDecoder Maven / Gradle / Ivy

    There is a newer version: 0.3.5
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    package net.dongliu.prettypb.rpc.coder;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import io.netty.handler.codec.CorruptedFrameException;
import net.dongliu.prettypb.runtime.code.ProtoBufReader;

import java.io.ByteArrayInputStream;
import java.util.List;

/**
 * A decoder that splits the received {@link io.netty.buffer.ByteBuf}s dynamically by the
 * value of the Google Protocol Buffers
 * Base
 * 128 Varints integer length field in the message.  For example:
 * 
     * BEFORE DECODE (302 bytes)       AFTER DECODE (300 bytes)
 * +--------+---------------+      +---------------+
 * | Length | Protobuf Data |----- | Protobuf Data |
 * | 0xAC02 |  (300 bytes)  |      |  (300 bytes)  |
 * +--------+---------------+      +---------------+
 * 
    
 *
 * @author dongliu
 */
public class VarIntFrameDecoder extends ByteToMessageDecoder {

    // TODO maxFrameLength + safe skip + fail-fast option
    //      (just like LengthFieldBasedFrameDecoder)

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List out)
            throws Exception {
        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;
                try (ProtoBufReader reader = new ProtoBufReader(new ByteArrayInputStream(buf))) {
                    length = reader.readVarInt();
                }
                if (length < 0) {
                    throw new CorruptedFrameException("negative length: " + length);
                }

                if (in.readableBytes() < length) {
                    in.resetReaderIndex();
                    return;
                } else {
                    out.add(in.readBytes(length));
                    return;
                }
            }
        }

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

    




    
    
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