<!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 `write` fn in crate `std`."> <meta name="keywords" content="rust, rustlang, rust-lang, write"> <title>std::ptr::write - 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='../../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'><a href='../index.html'>std</a>::<wbr><a href='index.html'>ptr</a></p><script>window.sidebarCurrent = {name: 'write', 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'>std</a>::<wbr><a href='index.html'>ptr</a>::<wbr><a class="fn" href=''>write</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/ptr.rs.html#363-365' title='goto source code'>[src]</a></span></h1> <pre class='rust fn'>pub unsafe fn write<T>(dst: <a class="primitive" href="../primitive.pointer.html">*mut T</a>, src: T)</pre><div class='docblock'><p>Overwrites a memory location with the given value without reading or dropping the old value.</p> <h1 id="safety" class="section-header"><a href="#safety">Safety</a></h1> <p>This operation is marked unsafe because it accepts a raw pointer.</p> <p>It does not drop the contents of <code>dst</code>. This is safe, but it could leak allocations or resources, so care must be taken not to overwrite an object that should be dropped.</p> <p>Additionally, it does not drop <code>src</code>. Semantically, <code>src</code> is moved into the location pointed to by <code>dst</code>.</p> <p>This is appropriate for initializing uninitialized memory, or overwriting memory that has previously been <code>read</code> from.</p> <p>The pointer must be aligned; use <code>write_unaligned</code> if that is not the case.</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">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">0</span>; <span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">i32</span>; <span class="kw">let</span> <span class="ident">z</span> <span class="op">=</span> <span class="number">12</span>; <span class="kw">unsafe</span> { <span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">write</span>(<span class="ident">y</span>, <span class="ident">z</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">read</span>(<span class="ident">y</span>), <span class="number">12</span>); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%200%3B%0Alet%20y%20%3D%20%26mut%20x%20as%20*mut%20i32%3B%0Alet%20z%20%3D%2012%3B%0A%0Aunsafe%20%7B%0A%20%20%20%20std%3A%3Aptr%3A%3Awrite(y%2C%20z)%3B%0A%20%20%20%20assert_eq!(std%3A%3Aptr%3A%3Aread(y)%2C%2012)%3B%0A%7D%0A%7D">Run</a></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 = "std"; </script> <script src="../../main.js"></script> <script defer src="../../search-index.js"></script> </body> </html>