lstlisting environment inside luacode

Question

I'd like to feed a lstlisting environment (from the listings package) with contents back to TeX from Lua, but the end of lstlisting is apparently not found. The same happens if lstlisting is replaced with verbatim. How do I fix this?

Note that I want luacode to feed lstlisting back to TeX, not a hack that works in this instance but doesn't do that.

\documentclass{article}

\usepackage{listings}
\usepackage{luacode,luatexbase}

\newcommand{\processfile}[1]{\directlua{processfile("#1")}}

\begin{luacode*}
function processfile(fn)
  tex.print("\\begin{lstlisting}\n")
  local f=assert(io.open(fn,"r"))
  local t= f:read("*all")
  f:close()
  tex.print(t)
  tex.print("\\end{lstlisting}\n")  
  end
\end{luacode*}

\begin{document}
\processfile{code.c}
\end{document}

Answer 1

The following seems to work. But I had to use the luacode-environment. So it not "pure" luacode but I didn't find a way to do the \detokenize on the lua-side. I also changed the processing to line-by-line to get the correct linebreak.

\documentclass{article}
\usepackage{listings}
\newcommand{\processfile}[1]{\directlua{processfilebyline("#1")}}
\usepackage{luacode}

\begin{luacode}
function processfilebyline(fn)
  tex.print("\\begin{lstlisting}")
  local f=assert(io.open(fn,"r"))
  while true do
      local line = f:read("*line")
      if line == nil then break end
      tex.print(line)
    end
  f:close()
  tex.print("\detokenize{\\end{lstlisting}}")
  end

\end{luacode}
 %
\begin{document}
\processfile{duck.tex}
\end{document}