hi,I see the  code for method setBytes in class com.alibaba.dubbo.remoting.transport.netty4.NettyBackedChannelBuffer.java which is below,is there a problem ?

![image](https://user-images.githubusercontent.com/20593632/46648646-90eaba00-cbc8-11e8-896d-9a1d235d7e0b.png)


if (length > dst.writableBytes()) {
            throw new IndexOutOfBoundsException();
        }
        getBytes(index, dst, dst.writerIndex(), length);
        dst.writerIndex(dst.writerIndex() + length);
    }
    @Override
    public void markReaderIndex() {
        buffer.markReaderIndex();
    }
    @Override
    public void markWriterIndex() {
        buffer.markWriterIndex();
    }
    @Override
    public boolean readable() {
        return buffer.readable();
    }
    @Override
    public int readableBytes() {
        return buffer.readableBytes();
    }
    @Override
    public byte readByte() {
        return buffer.readByte();
    }
    @Override
    public void readBytes(byte[] dst) {
        buffer.readBytes(dst);