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<title>Structures (libffi: the portable foreign function interface library)</title>

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<h4 class="subsection" id="Structures-1"><span>2.3.2 Structures<a class="copiable-link" href="#Structures-1"> &para;</a></span></h4>

<p><code class="code">libffi</code> is perfectly happy passing structures back and forth.
You must first describe the structure to <code class="code">libffi</code> by creating a
new <code class="code">ffi_type</code> object for it.
</p>
<a class="index-entry-id" id="index-ffi_005ftype"></a>
<dl class="first-deftp">
<dt class="deftp" id="index-ffi_005ftype-1"><span class="category-def">Data type: </span><span><strong class="def-name">ffi_type</strong><a class="copiable-link" href="#index-ffi_005ftype-1"> &para;</a></span></dt>
<dd><p>The <code class="code">ffi_type</code> has the following members:
</p><dl class="table">
<dt><code class="code">size_t size</code></dt>
<dd><p>This is set by <code class="code">libffi</code>; you should initialize it to zero.
</p>
</dd>
<dt><code class="code">unsigned short alignment</code></dt>
<dd><p>This is set by <code class="code">libffi</code>; you should initialize it to zero.
</p>
</dd>
<dt><code class="code">unsigned short type</code></dt>
<dd><p>For a structure, this should be set to <code class="code">FFI_TYPE_STRUCT</code>.
</p>
</dd>
<dt><code class="code">ffi_type **elements</code></dt>
<dd><p>This is a &lsquo;<samp class="samp">NULL</samp>&rsquo;-terminated array of pointers to <code class="code">ffi_type</code>
objects.  There is one element per field of the struct.
</p>
<p>Note that <code class="code">libffi</code> has no special support for bit-fields.  You
must manage these manually.
</p></dd>
</dl>
</dd></dl>

<p>The <code class="code">size</code> and <code class="code">alignment</code> fields will be filled in by
<code class="code">ffi_prep_cif</code> or <code class="code">ffi_prep_cif_var</code>, as needed.
</p>
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