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)


@Override
    public void discardReadBytes() {
        buffer.discardReadBytes();
    }
    
    @Override
    public void ensureWritableBytes(int writableBytes) {
        buffer.ensureWritable(writableBytes);
    }
    
    @Override
    public void getBytes(int index, byte[] dst) {
        buffer.getBytes(index, dst);
    }
    
    @Override
    public void getBytes(int index, ChannelBuffer dst) {
        
        getBytes(index, dst, dst.writableBytes());
    }
    
    @Override
    public void getBytes(int index, ChannelBuffer dst, int length) {
        
        if (length > dst.writableBytes()) {
            throw new IndexOutOfBoundsException();
        }
        getBytes(index, dst, dst.writerIndex(), length);
        dst.writerIndex(dst.writerIndex() + length);