Eiyeron
/
luwra


			
				
					
						
						
							123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256
							<!DOCTYPE html>
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  
  
  
  <title>Function Wrapping - Luwra</title>
  

  <link rel="shortcut icon" href="../img/favicon.ico">

  
  <link href='https://fonts.googleapis.com/css?family=Lato:400,700|Roboto+Slab:400,700|Inconsolata:400,700' rel='stylesheet' type='text/css'>

  <link rel="stylesheet" href="../css/theme.css" type="text/css" />
  <link rel="stylesheet" href="../css/theme_extra.css" type="text/css" />
  <link rel="stylesheet" href="../css/highlight.css">

  
  <script>
    // Current page data
    var mkdocs_page_name = "Function Wrapping";
    var mkdocs_page_input_path = "wrapping.md";
    var mkdocs_page_url = "/wrapping/";
  </script>
  
  <script src="../js/jquery-2.1.1.min.js"></script>
  <script src="../js/modernizr-2.8.3.min.js"></script>
  <script type="text/javascript" src="../js/highlight.pack.js"></script>
  <script src="../js/theme.js"></script> 

  
</head>

<body class="wy-body-for-nav" role="document">

  <div class="wy-grid-for-nav">

    
    <nav data-toggle="wy-nav-shift" class="wy-nav-side stickynav">
      <div class="wy-side-nav-search">
        <a href=".." class="icon icon-home"> Luwra</a>
        <div role="search">
  <form id ="rtd-search-form" class="wy-form" action="../search.html" method="get">
    <input type="text" name="q" placeholder="Search docs" />
  </form>
</div>
      </div>

      <div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
        <ul class="current">
          
            <li>
    <li class="toctree-l1 ">
        <a class="" href="..">Home</a>
        
    </li>
<li>
          
            <li>
    <li class="toctree-l1 ">
        <a class="" href="../basics/">Basic Stack Interaction</a>
        
    </li>
<li>
          
            <li>
    <li class="toctree-l1 ">
        <a class="" href="../advanced/">Advanced Stack Interaction</a>
        
    </li>
<li>
          
            <li>
    <li class="toctree-l1 current">
        <a class="current" href="./">Function Wrapping</a>
        
            <ul>
            
                <li class="toctree-l3"><a href="#general">General</a></li>
                
                    <li><a class="toctree-l4" href="#wrap-functions">Wrap functions</a></li>
                
                    <li><a class="toctree-l4" href="#wrap-methods-and-fields">Wrap methods and fields</a></li>
                
            
            </ul>
        
    </li>
<li>
          
            <li>
    <li class="toctree-l1 ">
        <a class="" href="../user-types/">User Types</a>
        
    </li>
<li>
          
        </ul>
      </div>
      &nbsp;
    </nav>

    <section data-toggle="wy-nav-shift" class="wy-nav-content-wrap">

      
      <nav class="wy-nav-top" role="navigation" aria-label="top navigation">
        <i data-toggle="wy-nav-top" class="fa fa-bars"></i>
        <a href="..">Luwra</a>
      </nav>

      
      <div class="wy-nav-content">
        <div class="rst-content">
          <div role="navigation" aria-label="breadcrumbs navigation">
  <ul class="wy-breadcrumbs">
    <li><a href="..">Docs</a> &raquo;</li>
    
      
    
    <li>Function Wrapping</li>
    <li class="wy-breadcrumbs-aside">
      
        
          <a href="https://github.com/vapourismo/luwra" class="icon icon-github"> Edit on GitHub</a>
        
      
    </li>
  </ul>
  <hr/>
</div>
          <div role="main">
            <div class="section">
              
                <h1 id="general">General</h1>
<p>Luwra provides an easy way to turn any C or C++ function into a
<a href="http://www.lua.org/manual/5.3/manual.html#lua_CFunction">lua_CFunction</a> which can be used by the
Lua VM. Note, all parameter types must be readable from the stack (<code>Value&lt;T&gt;::read</code> exists for all)
and the return type must be pushable (<code>Value&lt;T&gt;::push</code> exists).</p>
<h2 id="wrap-functions">Wrap functions</h2>
<p>Assuming you have a function similiar to this:</p>
<pre><code class="c++">int my_function(const char* a, int b) {
    return /* magic */;
}
</code></pre>

<p>You can easily wrap it using the <code>LUWRA_WRAP</code> macro:</p>
<pre><code class="c++">// Convert to lua_CFunction
lua_CFunction cfun = LUWRA_WRAP(my_function);

// Do something with it, for example set it as a Lua global function
luwra::setGlobal(lua, &quot;my_function&quot;, cfun);
</code></pre>

<p><strong>Note:</strong> Do not provide the address of your function (e.g. <code>&amp;my_function</code>) to any wrapping macro.
The macros will take care of this themselves. You must provide only the name of the function.</p>
<p>Calling the function from Lua is fairly straightforward:</p>
<pre><code class="lua">local my_result = my_function(&quot;Hello World&quot;, 1337)
print(my_result)
</code></pre>

<h2 id="wrap-methods-and-fields">Wrap methods and fields</h2>
<p>It is also possible to turn C++ field accessors and methods into <code>lua_CFunction</code>s. It is a little
trickier than wrapping normal functions. The resulting Lua functions expect the first (or <code>self</code>)
parameter to be a user type instance of the type which the wrapped field or method belongs to.</p>
<p><strong>Note:</strong> Before you wrap fields and methods manually, you might want to take a look at the
<a href="../user-types/">User Types</a> section.</p>
<p>The next examples will operate on the following structure:</p>
<pre><code class="c++">struct Point {
    double x, y;

    // ...

    void scale(double f) {
        x *= f;
        y *= f;
    }
};
</code></pre>

<p>In order to wrap <code>x</code>, <code>y</code> and <code>scale</code> we utilize the <code>LUWRA_WRAP</code> macro again:</p>
<pre><code class="c++">lua_CFunction cfun_x     = LUWRA_WRAP(Point::x),
              cfun_y     = LUWRA_WRAP(Point::y),
              cfun_scale = LUWRA_WRAP(Point::scale);

// Register as globals
luwra::setGlobal(lua, &quot;x&quot;, cfun_x);
luwra::setGlobal(lua, &quot;y&quot;, cfun_y);
luwra::setGlobal(lua, &quot;scale&quot;, cfun_scale);
</code></pre>

<p>Usage looks like this:</p>
<pre><code class="lua">local my_point = -- Magic

-- Access 'x' and 'y' field
print(x(my_point), y(my_point))

-- Set 'x' and 'y' field
x(my_point, 13.37)
y(my_point, 73.31)

-- Invoke 'scale' method
scale(my_point, 2)
</code></pre>
              
            </div>
          </div>
          <footer>
  
    <div class="rst-footer-buttons" role="navigation" aria-label="footer navigation">
      
        <a href="../user-types/" class="btn btn-neutral float-right" title="User Types">Next <span class="icon icon-circle-arrow-right"></span></a>
      
      
        <a href="../advanced/" class="btn btn-neutral" title="Advanced Stack Interaction"><span class="icon icon-circle-arrow-left"></span> Previous</a>
      
    </div>
  

  <hr/>

  <div role="contentinfo">
    <!-- Copyright etc -->
    
  </div>

  Built with <a href="http://www.mkdocs.org">MkDocs</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
</footer>
	  
        </div>
      </div>

    </section>

  </div>

<div class="rst-versions" role="note" style="cursor: pointer">
    <span class="rst-current-version" data-toggle="rst-current-version">
      
          <a href="https://github.com/vapourismo/luwra" class="icon icon-github" style="float: left; color: #fcfcfc"> GitHub</a>
      
      
        <span><a href="../advanced/" style="color: #fcfcfc;">&laquo; Previous</a></span>
      
      
        <span style="margin-left: 15px"><a href="../user-types/" style="color: #fcfcfc">Next &raquo;</a></span>
      
    </span>
</div>

</body>
</html>