💾 Archived View for sdf.org › rsdoiel › blog › 2020 › 05 › 01 › Combining-Oberon-and-C.html captured on 2023-06-14 at 14:27:21.
⬅️ Previous capture (2023-03-20)
-=-=-=-=-=-=-
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="language" content="EN">
<title>Combining-Oberon-and-C</title>
<link rel="stylesheet" type="text/css" href="/printfonts/print.css" media="print" />
<link rel="stylesheet" type="text/css" href="/webfonts/fonts.css" media="screen" />
<link rel="stylesheet" type="text/css" href="/css/site.css" media="screen" />
<link rel="stylesheet" type="text/css" href="/css/tables.css" media="screen" />
<link title="RSS feed for rsdoiel's blog" rel="alternate" type="application/rss+xml" href="https://rsdoiel.github.io/rss.xml" />
<meta name="keywords" content="Oberon, programming">
<link rel="alternative" type="application/markdown" href="/blog/2020/05/01/Combining-Oberon-and-C.md">
<link rel="search" type="application/opensearchdescription+xml"
title="Robert's Rambling Search Engine"
href="search.osdx">
</head>
<body>
<nav>
<ul>
<li><a href="/">R. S. Doiel</a></li>
<li><a href="/about.html">About</a></li>
<li><a href="/blog/">Blog</a></li>
<li><a href="/cv.html">CV</a></li>
<li><a href="https://github.com/rsdoiel">GitHub</a></li>
<li><a href="/library-terminology.html">Library Jargon</a></li>
<li><a href="/presentations.html">Presentations</a></li>
<li><a href="/projects.html">Projects</a></li>
<li><a href="/resume.html">Resume</a></li>
<li><a href="/search.html">Search</a></li>
<li><a href="/series/">Series</a></li>
</ul>
</nav>
<section>
<article>
<a data-pocket-label="pocket" data-pocket-count="none" class="pocket-btn" data-lang="en"></a>
<script type="text/javascript">!function(d,i){if(!d.getElementById(i)){var j=d.createElement("script");j.id=i;j.src="https://widgets.getpocket.com/v1/j/btn.js?v=1";var w=d.getElementById(i);d.body.appendChild(j);}}(document,"pocket-btn-js");</script>
<h1 id="combining-oberon-07-and-c-with-obnc">Combining Oberon-07 and C
with OBNC</h1>
<p>By R. S. Doiel, 2020-05-01</p>
<p>This is the fifth post in the <a
href="../../04/11/Mostly-Oberon.html">Mostly Oberon</a> series. Mostly
Oberon documents my exploration of the Oberon Language, Oberon System
and the various rabbit holes I will inevitably fall into.</p>
<p>In my day job I write allot of code in Go and orchestration code in
Python. It’s nice having the convenience of combining code written one
language with an another. You can do the same with <a
href="https://miasap.se/obnc/">OBNC</a>. The OBNC compiler supports
inclusion of C code in a straight forward manner. In fact Karl’s
compiler will generate the C file for you!</p>
<p>In learning how to combine C code and Oberon-07 I started by
reviewing Karl’s <a href="https://miasap.se/obnc/man/obnc.txt">manual
page</a>. The bottom part of that manual page describes the steps I will
repeat below. The description sounds more complicated but when you walk
through the steps it turns out to be pretty easy.</p>
<h2 id="basic-process">Basic Process</h2>
<p>Creating a C extension for use with OBNC is very straight
forward.</p>
<ol type="1">
<li>Create a Oberon module with empty exported procedures</li>
<li>Create a Oberon test module that uses your module</li>
<li>Compile your test module with OBNC</li>
<li>Copy the generated module <code>.c</code> file to the same directory
as your Oberon module source</li>
<li>Edit the skeleton <code>.c</code>, re-compile and test</li>
</ol>
<p>Five steps may sound complicated but in practice is straight
forward.</p>
<h2 id="fmt-an-example">Fmt, an example</h2>
<p>In my demonstration of Karl’s instructions I will be creating a
module named <code>Fmt</code> that includes two procedures
<code>Int()</code> and <code>Real()</code> that let you use a C-style
format string to format an INTEGER or REAL as an ARRAY OF CHAR. We
retain the idiomatic way Oberon works with types but allow a little more
flexibility in how the numbers are converted and rendered as
strings.</p>
<h3 id="step-1">Step 1</h3>
<p>Create <a href="Fmt.Mod">Fmt.Mod</a> defining two exported procedures
<code>Int*()</code> and <code>Real*()</code>. The procedures body should
be empty. Karl’s practice is to use exported comments to explain the
procedures.</p>
<pre class="oberon"><code>
MODULE Fmt;
PROCEDURE Int*(value : INTEGER; fmt: ARRAY OF CHAR;
VAR dest : ARRAY OF CHAR);
END Int;
PROCEDURE Real*(value : REAL; fmt: ARRAY OF CHAR;
VAR dest : ARRAY OF CHAR);
END Real;
BEGIN
END Fmt.
</code></pre>
<h3 id="step-2">Step 2</h3>
<p>Create a test module, <a href="FmtTest.Mod">FmtTest.Mod</a>, for <a
href="Fmt.Mod">Fmt.Mod</a>.</p>
<pre class="oberon"><code>
MODULE FmtTest;
IMPORT Out, Fmt;
PROCEDURE TestInt(): BOOLEAN;
VAR
fmtString : ARRAY 24 OF CHAR;
dest : ARRAY 128 OF CHAR;
i : INTEGER;
BEGIN
i := 42;
fmtString := "%d";
Fmt.Int(i, fmtString, dest);
Out.String(dest);Out.Ln;
RETURN TRUE
END TestInt;
PROCEDURE TestReal(): BOOLEAN;
VAR
fmtString : ARRAY 24 OF CHAR;
dest : ARRAY 128 OF CHAR;
r : REAL;
BEGIN
r := 3.145;
fmtString := "%d";
Fmt.Real(r, fmtString, dest);
Out.String(dest);Out.Ln;
RETURN TRUE
END TestReal;
BEGIN
ASSERT(TestInt());
ASSERT(TestReal());
Out.String("Success!");Out.Ln;
END FmtTest.
</code></pre>
<h3 id="step-3">Step 3</h3>
<p>Generate a new <a href="Fmt.c">Fmt.c</a> by using the OBNC
compiler.</p>
<pre class="shell"><code>
obnc FmtTest.Mod
mv .obnc/Fmt.c ./
</code></pre>
<p>the file <code>.obnc/Fmt.c</code> is your C template file. Copy it to
the directory where Fmt.Mod is.</p>
<h3 id="step-4">Step 4</h3>
<p>Update the skeleton <code>Fmt.c</code> with the necessary C code.
Here’s what OBNC generated version.</p>
<div class="sourceCode" id="cb4"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a> <span class="co">/*GENERATED BY OBNC 0.16.1*/</span></span>
<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-4"><a href="#cb4-4" aria-hidden="true" tabindex="-1"></a> <span class="pp">#include </span><span class="im">"Fmt.h"</span></span>
<span id="cb4-5"><a href="#cb4-5" aria-hidden="true" tabindex="-1"></a> <span class="pp">#include </span><span class="im"><obnc/OBNC.h></span></span>
<span id="cb4-6"><a href="#cb4-6" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-7"><a href="#cb4-7" aria-hidden="true" tabindex="-1"></a> <span class="pp">#define OBERON_SOURCE_FILENAME "Fmt.Mod"</span></span>
<span id="cb4-8"><a href="#cb4-8" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-9"><a href="#cb4-9" aria-hidden="true" tabindex="-1"></a> <span class="dt">void</span> Fmt__Int_<span class="op">(</span>OBNC_INTEGER value_<span class="op">,</span> <span class="dt">const</span> <span class="dt">char</span> fmt_<span class="op">[],</span> </span>
<span id="cb4-10"><a href="#cb4-10" aria-hidden="true" tabindex="-1"></a> OBNC_INTEGER fmt_len<span class="op">,</span> <span class="dt">char</span> dest_<span class="op">[],</span> </span>
<span id="cb4-11"><a href="#cb4-11" aria-hidden="true" tabindex="-1"></a> OBNC_INTEGER dest_len<span class="op">)</span></span>
<span id="cb4-12"><a href="#cb4-12" aria-hidden="true" tabindex="-1"></a> <span class="op">{</span></span>
<span id="cb4-13"><a href="#cb4-13" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
<span id="cb4-14"><a href="#cb4-14" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-15"><a href="#cb4-15" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-16"><a href="#cb4-16" aria-hidden="true" tabindex="-1"></a> <span class="dt">void</span> Fmt__Real_<span class="op">(</span>OBNC_REAL value_<span class="op">,</span> <span class="dt">const</span> <span class="dt">char</span> fmt_<span class="op">[],</span></span>
<span id="cb4-17"><a href="#cb4-17" aria-hidden="true" tabindex="-1"></a> OBNC_INTEGER fmt_len<span class="op">,</span> <span class="dt">char</span> dest_<span class="op">[],</span></span>
<span id="cb4-18"><a href="#cb4-18" aria-hidden="true" tabindex="-1"></a> OBNC_INTEGER dest_len<span class="op">)</span></span>
<span id="cb4-19"><a href="#cb4-19" aria-hidden="true" tabindex="-1"></a> <span class="op">{</span></span>
<span id="cb4-20"><a href="#cb4-20" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
<span id="cb4-21"><a href="#cb4-21" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-22"><a href="#cb4-22" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-23"><a href="#cb4-23" aria-hidden="true" tabindex="-1"></a> <span class="dt">void</span> Fmt__Init<span class="op">(</span><span class="dt">void</span><span class="op">)</span></span>
<span id="cb4-24"><a href="#cb4-24" aria-hidden="true" tabindex="-1"></a> <span class="op">{</span></span>
<span id="cb4-25"><a href="#cb4-25" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span></code></pre></div>
<p>Here’s the skeleton revised with do what we need to be done.</p>
<div class="sourceCode" id="cb5"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a> <span class="pp">#include </span><span class="im">".obnc/Fmt.h"</span></span>
<span id="cb5-3"><a href="#cb5-3" aria-hidden="true" tabindex="-1"></a> <span class="pp">#include </span><span class="im"><obnc/OBNC.h></span></span>
<span id="cb5-4"><a href="#cb5-4" aria-hidden="true" tabindex="-1"></a> <span class="pp">#include </span><span class="im"><stdio.h></span></span>
<span id="cb5-5"><a href="#cb5-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-6"><a href="#cb5-6" aria-hidden="true" tabindex="-1"></a> <span class="pp">#define OBERON_SOURCE_FILENAME "Fmt.Mod"</span></span>
<span id="cb5-7"><a href="#cb5-7" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-8"><a href="#cb5-8" aria-hidden="true" tabindex="-1"></a> <span class="dt">void</span> Fmt__Int_<span class="op">(</span>OBNC_INTEGER value_<span class="op">,</span> </span>
<span id="cb5-9"><a href="#cb5-9" aria-hidden="true" tabindex="-1"></a> <span class="dt">const</span> <span class="dt">char</span> fmt_<span class="op">[],</span> OBNC_INTEGER fmt_len<span class="op">,</span></span>
<span id="cb5-10"><a href="#cb5-10" aria-hidden="true" tabindex="-1"></a> <span class="dt">char</span> dest_<span class="op">[],</span> OBNC_INTEGER dest_len<span class="op">)</span></span>
<span id="cb5-11"><a href="#cb5-11" aria-hidden="true" tabindex="-1"></a> <span class="op">{</span></span>
<span id="cb5-12"><a href="#cb5-12" aria-hidden="true" tabindex="-1"></a> sprintf<span class="op">(</span>dest_<span class="op">,</span> fmt_<span class="op">,</span> value_<span class="op">);</span></span>
<span id="cb5-13"><a href="#cb5-13" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
<span id="cb5-14"><a href="#cb5-14" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-15"><a href="#cb5-15" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-16"><a href="#cb5-16" aria-hidden="true" tabindex="-1"></a> <span class="dt">void</span> Fmt__Real_<span class="op">(</span>OBNC_REAL value_<span class="op">,</span> <span class="dt">const</span> <span class="dt">char</span> fmt_<span class="op">[],</span></span>
<span id="cb5-17"><a href="#cb5-17" aria-hidden="true" tabindex="-1"></a> OBNC_INTEGER fmt_len<span class="op">,</span> <span class="dt">char</span> dest_<span class="op">[],</span></span>
<span id="cb5-18"><a href="#cb5-18" aria-hidden="true" tabindex="-1"></a> OBNC_INTEGER dest_len<span class="op">)</span></span>
<span id="cb5-19"><a href="#cb5-19" aria-hidden="true" tabindex="-1"></a> <span class="op">{</span></span>
<span id="cb5-20"><a href="#cb5-20" aria-hidden="true" tabindex="-1"></a> sprintf<span class="op">(</span>dest_<span class="op">,</span> fmt_<span class="op">,</span> value_<span class="op">);</span></span>
<span id="cb5-21"><a href="#cb5-21" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span>
<span id="cb5-22"><a href="#cb5-22" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-23"><a href="#cb5-23" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-24"><a href="#cb5-24" aria-hidden="true" tabindex="-1"></a> <span class="dt">void</span> Fmt__Init<span class="op">(</span><span class="dt">void</span><span class="op">)</span></span>
<span id="cb5-25"><a href="#cb5-25" aria-hidden="true" tabindex="-1"></a> <span class="op">{</span></span>
<span id="cb5-26"><a href="#cb5-26" aria-hidden="true" tabindex="-1"></a> <span class="op">}</span></span></code></pre></div>
<p>NOTE: You need to change the path for the <code>Fmt.h</code> file
reference. I also add the <code>stdio.h</code> include so I have access
to the C function I wish to use. Also notice how OBNC the signature for
the functions use the <code>_</code> character to identify mapped values
as well as the char arrays being provided with a length parameter. If
you are doing more extensive string work you’ll want to take advantage
of these additional parameters so insure that the as strings are
terminated properly for Oberon’s reuse.</p>
<h3 id="step-5">Step 5</h3>
<p>Recompile and test.</p>
<pre class="shell"><code>
obnc FmtTest.Mod
./FmtTest
</code></pre>
<h3 id="next-and-previous">Next and Previous</h3>
<ul>
<li>Next <a href="../06/Compiling-OBNC-on-macOS.html">Compiling OBNC on
macOS</a></li>
<li>Previously <a
href="../../04/19/Mostly-Oberon-Loops-and-Conditions.html">Oberon Loops
and Conditions</a></li>
</ul>
</article>
</section>
<footer>
<p>copyright © 2016 - 2023 R. S. Doiel<br /> <a
href="/rssfeed.html">RSS</a> feeds and website built with <a
href="https://rsdoiel.github.io/pttk">pttk</a>, Bash, Make and <a
href="https://pandoc.org">Pandoc</a>.</p>
</footer>
<!-- START: PrettyFi from https://github.com/google/code-prettify -->
<script>
/* We want to add the class "prettyprint" to all the pre elements */
var pre_list = document.querySelectorAll("pre");
pre_list.forEach(function(elem) {
elem.classList.add("prettyprint");
elem.classList.add("linenums");/**/
elem.classList.add("json"); /**/
});
</script>
<style>
li.L0, li.L1, li.L2, li.L3, li.L4, li.L5, li.L6, li.L7, li.L8, li.L9
{
color: #555;
list-style-type: decimal;
}
</style>
<link rel="stylesheet" type="text/css" href="/css/prettify.css">
<script src="https://cdn.jsdelivr.net/gh/google/code-prettify@master/loader/run_
prettify.js"></script>
<!-- END: PrettyFi from https://github.com/google/code-prettify -->
</body>
</html>