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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- This manual is for libffi, a portable foreign function interface library. Copyright (C) 2008-2019 Anthony Green and Red Hat, Inc. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. --> <!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ --> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Structures (libffi: the portable foreign function interface library)</title> <meta name="description" content="Structures (libffi: the portable foreign function interface library)"> <meta name="keywords" content="Structures (libffi: the portable foreign function interface library)"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <link href="index.html" rel="start" title="Top"> <link href="Index.html" rel="index" title="Index"> <link href="Types.html" rel="up" title="Types"> <link href="Size-and-Alignment.html" rel="next" title="Size and Alignment"> <link href="Primitive-Types.html" rel="prev" title="Primitive Types"> <style type="text/css"> <!-- a.summary-letter {text-decoration: none} blockquote.indentedblock {margin-right: 0em} div.display {margin-left: 3.2em} div.example {margin-left: 3.2em} div.lisp {margin-left: 3.2em} kbd {font-style: oblique} pre.display {font-family: inherit} pre.format {font-family: inherit} pre.menu-comment {font-family: serif} pre.menu-preformatted {font-family: serif} span.nolinebreak {white-space: nowrap} span.roman {font-family: initial; font-weight: normal} span.sansserif {font-family: sans-serif; font-weight: normal} ul.no-bullet {list-style: none} --> </style> </head> <body lang="en"> <span id="Structures"></span><div class="header"> <p> Next: <a href="Size-and-Alignment.html" accesskey="n" rel="next">Size and Alignment</a>, Previous: <a href="Primitive-Types.html" accesskey="p" rel="prev">Primitive Types</a>, Up: <a href="Types.html" accesskey="u" rel="up">Types</a> [<a href="Index.html" title="Index" rel="index">Index</a>]</p> </div> <hr> <span id="Structures-1"></span><h4 class="subsection">2.3.2 Structures</h4> <p>‘<samp>libffi</samp>’ is perfectly happy passing structures back and forth. You must first describe the structure to ‘<samp>libffi</samp>’ by creating a new <code>ffi_type</code> object for it. </p> <span id="index-ffi_005ftype"></span> <dl> <dt id="index-ffi_005ftype-1">Data type: <strong>ffi_type</strong></dt> <dd><p>The <code>ffi_type</code> has the following members: </p><dl compact="compact"> <dt><code>size_t size</code></dt> <dd><p>This is set by <code>libffi</code>; you should initialize it to zero. </p> </dd> <dt><code>unsigned short alignment</code></dt> <dd><p>This is set by <code>libffi</code>; you should initialize it to zero. </p> </dd> <dt><code>unsigned short type</code></dt> <dd><p>For a structure, this should be set to <code>FFI_TYPE_STRUCT</code>. </p> </dd> <dt><code>ffi_type **elements</code></dt> <dd><p>This is a ‘<samp>NULL</samp>’-terminated array of pointers to <code>ffi_type</code> objects. There is one element per field of the struct. </p> <p>Note that ‘<samp>libffi</samp>’ has no special support for bit-fields. You must manage these manually. </p></dd> </dl> </dd></dl> <p>The <code>size</code> and <code>alignment</code> fields will be filled in by <code>ffi_prep_cif</code> or <code>ffi_prep_cif_var</code>, as needed. </p> </body> </html>