code: func (b *ByteBuf) SetReaderIndex(newReaderIndex int) error {
  	if newReaderIndex < 0 || newReaderIndex > b.writerIndex {
  		return io.ErrShortBuffer
  	}
  
  	b.readerIndex = newReaderIndex
  
  	return nil
  }
docs: // SetReaderIndex set the read index