<!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="../../../../main.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"> </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#11-147' 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 <code>OsStr</code>.</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 <code>OsString</code>.</p> </td> </tr></table></section> <section id='search' class="content hidden"></section> <section class="footer"></section> <aside id="help" class="hidden"> <div> <h1 class="hidden">Help</h1> <div class="shortcuts"> <h2>Keyboard Shortcuts</h2> <dl> <dt><kbd>?</kbd></dt> <dd>Show this help dialog</dd> <dt><kbd>S</kbd></dt> <dd>Focus the search field</dd> <dt><kbd>↑</kbd></dt> <dd>Move up in search results</dd> <dt><kbd>↓</kbd></dt> <dd>Move down in search results</dd> <dt><kbd>↹</kbd></dt> <dd>Switch tab</dd> <dt><kbd>⏎</kbd></dt> <dd>Go to active search result</dd> <dt><kbd>+</kbd></dt> <dd>Expand all sections</dd> <dt><kbd>-</kbd></dt> <dd>Collapse all sections</dd> </dl> </div> <div class="infos"> <h2>Search Tricks</h2> <p> Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type. </p> <p> Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>. </p> <p> Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>) </p> </div> </div> </aside> <script> window.rootPath = "../../../../"; window.currentCrate = "std"; </script> <script src="../../../../main.js"></script> <script defer src="../../../../search-index.js"></script> </body> </html>