net.dongliu.prettypb.rpc.coder.VarIntLengthFieldPrepender Maven / Gradle / Ivy

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proto rpc libs, compatible with proto-rpc-pro

There is a newer version: 0.3.5

package net.dongliu.prettypb.rpc.coder;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufOutputStream;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import net.dongliu.prettypb.runtime.code.ProtoBufWriter;

/**
 * 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 VarIntLengthFieldPrepender extends MessageToByteEncoder {

    @Override
    protected void encode(
            ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception {
        int bodyLen = msg.readableBytes();
        out.ensureWritable(bodyLen);

        try (ProtoBufWriter writer = new ProtoBufWriter(new ByteBufOutputStream(out))) {
            writer.writeVarInt(bodyLen);
        }
        out.writeBytes(msg, msg.readerIndex(), bodyLen);
    }
}