Side-by-side layout only on some lines of listing

How is the following achieved?

I’ve done the blue parts with escapeinside:

documentclass{article}
usepackage{listings}

lstset{numbers=left}

begin{document} 

% this achieves the first two lines
begin{lstlisting}[escapeinside={(*}{*)}]
  (*{texttt{emp}}*)
  barrier b = new barrier(2);
end{lstlisting}

end{document}

but adding a table in the same way seems like a bad idea. I’m not sure how else to do the || parts within a listing.

Alternatively this could be a bunch of nested tables with formatting applied manually… is there a better way, making use of listings, so I don’t have to reinvent e.g. line numbers?