How to layout code listings with a caption and a frame around the code

codelistinghelper.tex

\usepackage{color}
\usepackage{xcolor}
\usepackage{calc}
\newlength\captionLeftDimension
\newlength\captionRightDimension
\setlength\captionLeftDimension{ \fboxsep+(\fboxrule*3)}
\setlength\captionRightDimension{-\fboxsep+(\fboxrule*3)}
\usepackage{listings}

\lstset{frame=single,
        frameround=fttf,
        xleftmargin=\captionLeftDimension,
        rulecolor=\color{gray},
        xrightmargin=\captionRightDimension}
\usepackage{caption}
\DeclareCaptionFont{white}{\color{white}}
\DeclareCaptionFormat{listing}{\parbox{\textwidth}{\colorbox{gray}{\parbox{\textwidth}{#1#2#3}}\vskip+1pt}}
\captionsetup[lstlisting]{format=listing,labelfont=white,textfont=white}