Adjust caption of algorithm2e using own macro

Question

I have a document with a few tables that have their captions formatted like this

which I achieved using

\usepackage[format=plain, justification=raggedright,singlelinecheck=true]{caption}
\captionsetup[table]{labelsep=newline, textfont=it, singlelinecheck=false, margin=1em}

and I would like to use the same layout for algorithms. I did find out from the package-readme and this page that I need

\usepackage[plainruled]{algorithm2e}

to remove the top rule above the caption and get this:

Next, I understand I need to define my own macro style to be able to use

\SetAlgoCaptionLayout{style}

but I am confused how to create the macro and how to left-align, use normalfont in footnotesize for the algorithm heading, insert the line break, and italicize the caption text.

MWE:

\documentclass{article}
\usepackage[plainruled]{algorithm2e}
\begin{document}

\begin{algorithm}
{\footnotesize
\caption{An example}
some text\;
}
\end{algorithm}
\end{document}

Answer 1

Got it. You can redefine the function defining the top rule. It is not perfect, but works.

\documentclass{article}
\usepackage[algoruled]{algorithm2e}

% Removes the top rule above caption see l.2531 of algorithm2e.sty
\makeatletter
\def\@algocf@pre@algoruled{}%
\makeatother
% Changes the caption font to italic
\renewcommand{\AlCapNameFnt}{\footnotesize\itshape}
% Removes bold font Algorithm
\renewcommand{\AlCapFnt}{\footnotesize\normalfont}
% Replaces ":" with a linebreak after Algorithm n°xxx
\SetAlgoCaptionSeparator{\\}
\begin{document}
\begin{algorithm}
{\footnotesize
\caption{An example}
some text\;
}
\end{algorithm}
\end{document}

Answer 2

The following also adds the \footnotesize font size to your algorithm environment:

\documentclass{article}

\usepackage{fourier}
\usepackage[ruled]{algorithm2e}

\SetAlCapFnt{\normalfont\footnotesize}% Set caption font
\SetAlgoCaptionSeparator{\par\nobreak}% Set caption separator
\SetAlCapNameFnt{\unskip\itshape\footnotesize}% Set caption name font
\makeatletter
\def\@algocf@pre@ruled{}% Remove rule above caption
\let\old@algocf@start\@algocf@start
\renewcommand{\@algocf@start}{\old@algocf@start\footnotesize}
\makeatother

\begin{document}

\begin{algorithm}
  \caption{An example}
  some text\;
\end{algorithm}

\end{document}