<!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 `from_utf8` fn in crate `alloc`."> <meta name="keywords" content="rust, rustlang, rust-lang, from_utf8"> <title>alloc::str::from_utf8 - 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 fn"> <!--[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='../../alloc/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> <p class='location'><a href='../index.html'>alloc</a>::<wbr><a href='index.html'>str</a></p><script>window.sidebarCurrent = {name: 'from_utf8', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script> </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'>Function <a href='../index.html'>alloc</a>::<wbr><a href='index.html'>str</a>::<wbr><a class="fn" href=''>from_utf8</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/core/str/mod.rs.html#301-304' title='goto source code'>[src]</a></span></h1> <pre class='rust fn'>pub fn from_utf8(v: &[u8]) -> <a class="enum" href="../../core/result/enum.Result.html" title="enum core::result::Result">Result</a><&str, <a class="struct" href="../../alloc/str/struct.Utf8Error.html" title="struct alloc::str::Utf8Error">Utf8Error</a>></pre><div class='docblock'><p>Converts a slice of bytes to a string slice.</p> <p>A string slice (<a href="../../std/primitive.str.html"><code>&str</code></a>) is made of bytes (<a href="../../std/primitive.u8.html"><code>u8</code></a>), and a byte slice (<a href="../../std/primitive.slice.html"><code>&[u8]</code></a>) is made of bytes, so this function converts between the two. Not all byte slices are valid string slices, however: <a href="../../std/primitive.str.html"><code>&str</code></a> requires that it is valid UTF-8. <code>from_utf8()</code> checks to ensure that the bytes are valid UTF-8, and then does the conversion.</p> <p>If you are sure that the byte slice is valid UTF-8, and you don't want to incur the overhead of the validity check, there is an unsafe version of this function, <a href="fn.from_utf8_unchecked.html"><code>from_utf8_unchecked</code></a>, which has the same behavior but skips the check.</p> <p>If you need a <code>String</code> instead of a <code>&str</code>, consider <a href="../../std/string/struct.String.html#method.from_utf8"><code>String::from_utf8</code></a>.</p> <p>Because you can stack-allocate a <code>[u8; N]</code>, and you can take a <a href="../../std/primitive.slice.html"><code>&[u8]</code></a> of it, this function is one way to have a stack-allocated string. There is an example of this in the examples section below.</p> <h1 id="errors" class="section-header"><a href="#errors">Errors</a></h1> <p>Returns <code>Err</code> if the slice is not UTF-8 with a description as to why the provided slice is not UTF-8.</p> <h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1> <p>Basic usage:</p> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">str</span>; <span class="comment">// some bytes, in a vector</span> <span class="kw">let</span> <span class="ident">sparkle_heart</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">240</span>, <span class="number">159</span>, <span class="number">146</span>, <span class="number">150</span>]; <span class="comment">// We know these bytes are valid, so just use `unwrap()`.</span> <span class="kw">let</span> <span class="ident">sparkle_heart</span> <span class="op">=</span> <span class="ident">str</span>::<span class="ident">from_utf8</span>(<span class="kw-2">&</span><span class="ident">sparkle_heart</span>).<span class="ident">unwrap</span>(); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="string">"💖"</span>, <span class="ident">sparkle_heart</span>);</pre> <p>Incorrect bytes:</p> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">str</span>; <span class="comment">// some invalid bytes, in a vector</span> <span class="kw">let</span> <span class="ident">sparkle_heart</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">0</span>, <span class="number">159</span>, <span class="number">146</span>, <span class="number">150</span>]; <span class="macro">assert</span><span class="macro">!</span>(<span class="ident">str</span>::<span class="ident">from_utf8</span>(<span class="kw-2">&</span><span class="ident">sparkle_heart</span>).<span class="ident">is_err</span>());</pre> <p>See the docs for <a href="struct.Utf8Error.html"><code>Utf8Error</code></a> for more details on the kinds of errors that can be returned.</p> <p>A "stack allocated string":</p> <pre class="rust rust-example-rendered"> <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">str</span>; <span class="comment">// some bytes, in a stack-allocated array</span> <span class="kw">let</span> <span class="ident">sparkle_heart</span> <span class="op">=</span> [<span class="number">240</span>, <span class="number">159</span>, <span class="number">146</span>, <span class="number">150</span>]; <span class="comment">// We know these bytes are valid, so just use `unwrap()`.</span> <span class="kw">let</span> <span class="ident">sparkle_heart</span> <span class="op">=</span> <span class="ident">str</span>::<span class="ident">from_utf8</span>(<span class="kw-2">&</span><span class="ident">sparkle_heart</span>).<span class="ident">unwrap</span>(); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="string">"💖"</span>, <span class="ident">sparkle_heart</span>);</pre> </div></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 = "alloc"; </script> <script src="../../main.js"></script> <script defer src="../../search-index.js"></script> </body> </html>