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<h1 class='fqn'><span class='in-band'>Function <a href='../index.html'>core</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'>
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[<span class='inner'>−</span>]
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</span><a class='srclink' href='../../src/core/str/mod.rs.html#298-301' 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="../../core/str/struct.Utf8Error.html" title="struct core::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>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Ause%20std%3A%3Astr%3B%0A%0A%2F%2F%20some%20bytes%2C%20in%20a%20vector%0Alet%20sparkle_heart%20%3D%20vec!%5B240%2C%20159%2C%20146%2C%20150%5D%3B%0A%0A%2F%2F%20We%20know%20these%20bytes%20are%20valid%2C%20so%20just%20use%20%60unwrap()%60.%0Alet%20sparkle_heart%20%3D%20str%3A%3Afrom_utf8(%26sparkle_heart).unwrap()%3B%0A%0Aassert_eq!(%22%F0%9F%92%96%22%2C%20sparkle_heart)%3B%0A%7D">Run</a></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>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Ause%20std%3A%3Astr%3B%0A%0A%2F%2F%20some%20invalid%20bytes%2C%20in%20a%20vector%0Alet%20sparkle_heart%20%3D%20vec!%5B0%2C%20159%2C%20146%2C%20150%5D%3B%0A%0Aassert!(str%3A%3Afrom_utf8(%26sparkle_heart).is_err())%3B%0A%7D">Run</a></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>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Ause%20std%3A%3Astr%3B%0A%0A%2F%2F%20some%20bytes%2C%20in%20a%20stack-allocated%20array%0Alet%20sparkle_heart%20%3D%20%5B240%2C%20159%2C%20146%2C%20150%5D%3B%0A%0A%2F%2F%20We%20know%20these%20bytes%20are%20valid%2C%20so%20just%20use%20%60unwrap()%60.%0Alet%20sparkle_heart%20%3D%20str%3A%3Afrom_utf8(%26sparkle_heart).unwrap()%3B%0A%0Aassert_eq!(%22%F0%9F%92%96%22%2C%20sparkle_heart)%3B%0A%7D">Run</a></pre>
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