<!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 `FileExt` trait in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, FileExt"><title>std::os::windows::fs::FileExt - 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 trait"><!--[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'>Trait FileExt</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.seek_read">seek_read</a><a href="#tymethod.seek_write">seek_write</a></div><a class="sidebar-title" href="#implementors">Implementors</a></div><p class='location'><a href='../../../index.html'>std</a>::<wbr><a href='../../index.html'>os</a>::<wbr><a href='../index.html'>windows</a>::<wbr><a href='index.html'>fs</a></p><script>window.sidebarCurrent = {name: 'FileExt', ty: 'trait', 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'>Trait <a href='../../../index.html'>std</a>::<wbr><a href='../../index.html'>os</a>::<wbr><a href='../index.html'>windows</a>::<wbr><a href='index.html'>fs</a>::<wbr><a class="trait" href=''>FileExt</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.15.0'>1.15.0</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/fs.rs.html#25-93' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust trait'>pub trait FileExt {
fn <a href='#tymethod.seek_read' class='fnname'>seek_read</a>(&self, buf: <a class="primitive" href="../../../primitive.slice.html">&mut [</a><a class="primitive" href="../../../primitive.u8.html">u8</a><a class="primitive" href="../../../primitive.slice.html">]</a>, offset: <a class="primitive" href="../../../primitive.u64.html">u64</a>) -> <a class="type" href="../../../../std/io/type.Result.html" title="type std::io::Result">Result</a><<a class="primitive" href="../../../primitive.usize.html">usize</a>>;
<div class='item-spacer'></div> fn <a href='#tymethod.seek_write' class='fnname'>seek_write</a>(&self, buf: <a class="primitive" href="../../../primitive.slice.html">&[</a><a class="primitive" href="../../../primitive.u8.html">u8</a><a class="primitive" href="../../../primitive.slice.html">]</a>, offset: <a class="primitive" href="../../../primitive.u64.html">u64</a>) -> <a class="type" href="../../../../std/io/type.Result.html" title="type std::io::Result">Result</a><<a class="primitive" href="../../../primitive.usize.html">usize</a>>;
}</pre></div><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 <a href="../../../fs/struct.File.html"><code>File</code></a>.</p>
</div>
<h2 id='required-methods' class='small-section-header'>
Required Methods<a href='#required-methods' class='anchor'></a>
</h2>
<div class='methods'>
<h3 id='tymethod.seek_read' class='method'><span id='seek_read.v' class='invisible'><code>fn <a href='#tymethod.seek_read' class='fnname'>seek_read</a>(&self, buf: <a class="primitive" href="../../../primitive.slice.html">&mut [</a><a class="primitive" href="../../../primitive.u8.html">u8</a><a class="primitive" href="../../../primitive.slice.html">]</a>, offset: <a class="primitive" href="../../../primitive.u64.html">u64</a>) -> <a class="type" href="../../../../std/io/type.Result.html" title="type std::io::Result">Result</a><<a class="primitive" href="../../../primitive.usize.html">usize</a>></code></span></h3><div class='stability'><div class='stab portability'>This is supported on <strong>Windows</strong> only.</div></div><div class='docblock'><p>Seeks to a given position and reads a number of bytes.</p>
<p>Returns the number of bytes read.</p>
<p>The offset is relative to the start of the file and thus independent
from the current cursor. The current cursor <strong>is</strong> affected by this
function, it is set to the end of the read.</p>
<p>Reading beyond the end of the file will always return with a length of
0.</p>
<p>Note that similar to <code>File::read</code>, it is not an error to return with a
short read. When returning from such a short read, the file pointer is
still updated.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fs</span>::<span class="ident">File</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">os</span>::<span class="ident">windows</span>::<span class="ident">prelude</span>::<span class="kw-2">*</span>;
<span class="kw">fn</span> <span class="ident">main</span>() <span class="op">-></span> <span class="ident">io</span>::<span class="prelude-ty">Result</span><span class="op"><</span>()<span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">file</span> <span class="op">=</span> <span class="ident">File</span>::<span class="ident">open</span>(<span class="string">"foo.txt"</span>)<span class="question-mark">?</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buffer</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">10</span>];
<span class="comment">// Read 10 bytes, starting 72 bytes from the</span>
<span class="comment">// start of the file.</span>
<span class="ident">file</span>.<span class="ident">seek_read</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buffer</span>[..], <span class="number">72</span>)<span class="question-mark">?</span>;
<span class="prelude-val">Ok</span>(())
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Aio%3B%0Ause%20std%3A%3Afs%3A%3AFile%3B%0Ause%20std%3A%3Aos%3A%3Awindows%3A%3Aprelude%3A%3A*%3B%0A%0Afn%20main()%20-%3E%20io%3A%3AResult%3C()%3E%20%7B%0A%20%20%20%20let%20mut%20file%20%3D%20File%3A%3Aopen(%22foo.txt%22)%3F%3B%0A%20%20%20%20let%20mut%20buffer%20%3D%20%5B0%3B%2010%5D%3B%0A%0A%20%20%20%20%2F%2F%20Read%2010%20bytes%2C%20starting%2072%20bytes%20from%20the%0A%20%20%20%20%2F%2F%20start%20of%20the%20file.%0A%20%20%20%20file.seek_read(%26mut%20buffer%5B..%5D%2C%2072)%3F%3B%0A%20%20%20%20Ok(())%0A%7D">Run</a></pre>
</div><h3 id='tymethod.seek_write' class='method'><span id='seek_write.v' class='invisible'><code>fn <a href='#tymethod.seek_write' class='fnname'>seek_write</a>(&self, buf: <a class="primitive" href="../../../primitive.slice.html">&[</a><a class="primitive" href="../../../primitive.u8.html">u8</a><a class="primitive" href="../../../primitive.slice.html">]</a>, offset: <a class="primitive" href="../../../primitive.u64.html">u64</a>) -> <a class="type" href="../../../../std/io/type.Result.html" title="type std::io::Result">Result</a><<a class="primitive" href="../../../primitive.usize.html">usize</a>></code></span></h3><div class='stability'><div class='stab portability'>This is supported on <strong>Windows</strong> only.</div></div><div class='docblock'><p>Seeks to a given position and writes a number of bytes.</p>
<p>Returns the number of bytes written.</p>
<p>The offset is relative to the start of the file and thus independent
from the current cursor. The current cursor <strong>is</strong> affected by this
function, it is set to the end of the write.</p>
<p>When writing beyond the end of the file, the file is appropriately
extended and the intermediate bytes are left uninitialized.</p>
<p>Note that similar to <code>File::write</code>, it is not an error to return a
short write. When returning from such a short write, the file pointer
is still updated.</p>
<h1 id="examples-1" class="section-header"><a href="#examples-1">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fs</span>::<span class="ident">File</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">os</span>::<span class="ident">windows</span>::<span class="ident">prelude</span>::<span class="kw-2">*</span>;
<span class="kw">fn</span> <span class="ident">main</span>() <span class="op">-></span> <span class="ident">std</span>::<span class="ident">io</span>::<span class="prelude-ty">Result</span><span class="op"><</span>()<span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buffer</span> <span class="op">=</span> <span class="ident">File</span>::<span class="ident">create</span>(<span class="string">"foo.txt"</span>)<span class="question-mark">?</span>;
<span class="comment">// Write a byte string starting 72 bytes from</span>
<span class="comment">// the start of the file.</span>
<span class="ident">buffer</span>.<span class="ident">seek_write</span>(<span class="string">b"some bytes"</span>, <span class="number">72</span>)<span class="question-mark">?</span>;
<span class="prelude-val">Ok</span>(())
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Afs%3A%3AFile%3B%0Ause%20std%3A%3Aos%3A%3Awindows%3A%3Aprelude%3A%3A*%3B%0A%0Afn%20main()%20-%3E%20std%3A%3Aio%3A%3AResult%3C()%3E%20%7B%0A%20%20%20%20let%20mut%20buffer%20%3D%20File%3A%3Acreate(%22foo.txt%22)%3F%3B%0A%0A%20%20%20%20%2F%2F%20Write%20a%20byte%20string%20starting%2072%20bytes%20from%0A%20%20%20%20%2F%2F%20the%20start%20of%20the%20file.%0A%20%20%20%20buffer.seek_write(b%22some%20bytes%22%2C%2072)%3F%3B%0A%20%20%20%20Ok(())%0A%7D">Run</a></pre>
</div></div>
<h2 id='implementors' class='small-section-header'>
Implementors<a href='#implementors' class='anchor'></a>
</h2>
<ul class='item-list' id='implementors-list'>
<li><table class='table-display'><tbody><tr><td><code>impl FileExt for <a class="struct" href="../../../../std/fs/struct.File.html" title="struct std::fs::File">File</a></code><td><div class='out-of-band'><a class='srclink' href='../../../../src/std/sys/windows/ext/fs.rs.html#96-104' title='goto source code'>[src]</a></div></td></tr></tbody></table></li>
</ul><script type="text/javascript">window.inlined_types=new Set([]);</script><script type="text/javascript" async
src="../../../../implementors/std/os/windows/fs/trait.FileExt.js">
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