<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="API documentation for the Rust `ffi` mod in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, ffi"><title>std::os::windows::ffi - Rust</title><link rel="stylesheet" type="text/css" href="../../../../normalize.css"><link rel="stylesheet" type="text/css" href="../../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../../../dark.css"><link rel="stylesheet" type="text/css" href="../../../../light.css" id="themeStyle"><script src="../../../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc mod"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><p class='location'>Module ffi</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#structs">Structs</a></li><li><a href="#traits">Traits</a></li></ul></div><p class='location'><a href='../../../index.html'>std</a>::<wbr><a href='../../index.html'>os</a>::<wbr><a href='../index.html'>windows</a></p><script>window.sidebarCurrent = {name: 'ffi', ty: 'mod', relpath: '../'};</script><script defer src="../sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../../../settings.html"><img src="../../../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Module <a href='../../../index.html'>std</a>::<wbr><a href='../../index.html'>os</a>::<wbr><a href='../index.html'>windows</a>::<wbr><a class="mod" href=''>ffi</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../../../../src/std/sys/windows/ext/ffi.rs.html#11-151' title='goto source code'>[src]</a></span></h1><div class='stability'><div class='stab portability'>This is supported on <strong>Windows</strong> only.</div></div><div class='docblock'><p>Windows-specific extensions to the primitives in the <code>std::ffi</code> module.</p>
<h1 id="overview" class="section-header"><a href="#overview">Overview</a></h1>
<p>For historical reasons, the Windows API uses a form of potentially
ill-formed UTF-16 encoding for strings. Specifically, the 16-bit
code units in Windows strings may contain <a href="https://simonsapin.github.io/wtf-8/#ill-formed-utf-16">isolated surrogate code
points which are not paired together</a>. The
Unicode standard requires that surrogate code points (those in the
range U+D800 to U+DFFF) always be <em>paired</em>, because in the UTF-16
encoding a <em>surrogate code unit pair</em> is used to encode a single
character. For compatibility with code that does not enforce
these pairings, Windows does not enforce them, either.</p>
<p>While it is not always possible to convert such a string losslessly into
a valid UTF-16 string (or even UTF-8), it is often desirable to be
able to round-trip such a string from and to Windows APIs
losslessly. For example, some Rust code may be "bridging" some
Windows APIs together, just passing <code>WCHAR</code> strings among those
APIs without ever really looking into the strings.</p>
<p>If Rust code <em>does</em> need to look into those strings, it can
convert them to valid UTF-8, possibly lossily, by substituting
invalid sequences with U+FFFD REPLACEMENT CHARACTER, as is
conventionally done in other Rust APIs that deal with string
encodings.</p>
<h1 id="osstringext-and-osstrext" class="section-header"><a href="#osstringext-and-osstrext"><code>OsStringExt</code> and <code>OsStrExt</code></a></h1>
<p><a href="../../../ffi/struct.OsString.html"><code>OsString</code></a> is the Rust wrapper for owned strings in the
preferred representation of the operating system. On Windows,
this struct gets augmented with an implementation of the
<a href="trait.OsStringExt.html"><code>OsStringExt</code></a> trait, which has a <a href="trait.OsStringExt.html#tymethod.from_wide"><code>from_wide</code></a> method. This
lets you create an <a href="../../../ffi/struct.OsString.html"><code>OsString</code></a> from a <code>&[u16]</code> slice; presumably
you get such a slice out of a <code>WCHAR</code> Windows API.</p>
<p>Similarly, <a href="../../../ffi/struct.OsStr.html"><code>OsStr</code></a> is the Rust wrapper for borrowed strings from
preferred representation of the operating system. On Windows, the
<a href="trait.OsStrExt.html"><code>OsStrExt</code></a> trait provides the <a href="trait.OsStrExt.html#tymethod.encode_wide"><code>encode_wide</code></a> method, which
outputs an <a href="struct.EncodeWide.html"><code>EncodeWide</code></a> iterator. You can <a href="../../../iter/trait.Iterator.html#method.collect"><code>collect</code></a> this
iterator, for example, to obtain a <code>Vec<u16></code>; you can later get a
pointer to this vector's contents and feed it to Windows APIs.</p>
<p>These traits, along with <a href="../../../ffi/struct.OsString.html"><code>OsString</code></a> and <a href="../../../ffi/struct.OsStr.html"><code>OsStr</code></a>, work in
conjunction so that it is possible to <strong>round-trip</strong> strings from
Windows and back, with no loss of data, even if the strings are
ill-formed UTF-16.</p>
</div><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
<table>
<tr class=' module-item'>
<td><a class="struct" href="struct.EncodeWide.html"
title='struct std::os::windows::ffi::EncodeWide'>EncodeWide</a></td>
<td class='docblock-short'>
[<div class='stab portability'>Windows</div>] <p>Generates a wide character sequence for potentially ill-formed UTF-16.</p>
</td>
</tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
<table>
<tr class=' module-item'>
<td><a class="trait" href="trait.OsStrExt.html"
title='trait std::os::windows::ffi::OsStrExt'>OsStrExt</a></td>
<td class='docblock-short'>
[<div class='stab portability'>Windows</div>] <p>Windows-specific extensions to <a href="../../../../std/ffi/struct.OsStr.html"><code>OsStr</code></a>.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="trait" href="trait.OsStringExt.html"
title='trait std::os::windows::ffi::OsStringExt'>OsStringExt</a></td>
<td class='docblock-short'>
[<div class='stab portability'>Windows</div>] <p>Windows-specific extensions to <a href="../../../../std/ffi/struct.OsString.html"><code>OsString</code></a>.</p>
</td>
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