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<!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="Provides wrapper types `Volatile`, `ReadOnly`, `WriteOnly`, `ReadWrite`, which wrap any copy-able type and allows for volatile memory access to wrapped value. Volatile memory accesses are never optimized away by the compiler, and are useful in many low-level systems programming and concurrent contexts."><meta name="keywords" content="rust, rustlang, rust-lang, volatile"><title>volatile - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Semibold.ttf.woff2"><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="../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../dark.css" disabled><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script src="../crates.js"></script><script defer src="../main.js"></script>
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</a><h2 class="location"><a href="#">Crate volatile</a></h2><div class="sidebar-elems"><div class="block"><ul><li class="version">Version 0.3.0</li><li><a id="all-types" href="all.html">All Items</a></li></div></ul><section><div class="block"><ul><li><a href="#structs">Structs</a></li><li><a href="#types">Type Definitions</a></li></ul></div></section><div id="sidebar-vars" data-name="volatile" data-ty="mod" data-relpath=""></div><script defer src="sidebar-items.js"></script></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../volatile/index.html"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></a><nav class="sub"><div class="theme-picker hidden"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="22" height="22" alt="Pick another theme!" src="../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><button type="button" id="help-button" title="help">?</button><a id="settings-menu" href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../wheel.svg"></a></div></form></nav></div><section id="main-content" class="content"><div class="main-heading">
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<h1 class="fqn"><span class="in-band">Crate <a class="mod" href="#">volatile</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../clipboard.svg" width="19" height="18" alt="Copy item path"></button></span></h1><span class="out-of-band"><a class="srclink" href="../src/volatile/lib.rs.html#1-310">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Provides wrapper types <code>Volatile</code>, <code>ReadOnly</code>, <code>WriteOnly</code>, <code>ReadWrite</code>, which wrap any copy-able type and allows for
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volatile memory access to wrapped value. Volatile memory accesses are never optimized away by
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the compiler, and are useful in many low-level systems programming and concurrent contexts.</p>
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<p>The wrapper types <em>do not</em> enforce any atomicity guarantees; to also get atomicity, consider
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looking at the <code>Atomic</code> wrapper type found in <code>libcore</code> or <code>libstd</code>.</p>
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<p>These wrappers do not depend on the standard library and never panic.</p>
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<h2 id="dealing-with-volatile-pointers"><a href="#dealing-with-volatile-pointers">Dealing with Volatile Pointers</a></h2>
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<p>Frequently, one may have to deal with volatile pointers, eg, writes to specific memory
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locations. The canonical way to solve this is to cast the pointer to a volatile wrapper
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directly, eg:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">volatile::Volatile</span>;
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<span class="kw">let</span> <span class="ident">mut_ptr</span> <span class="op">=</span> <span class="number">0xFEE00000</span> <span class="kw">as</span> <span class="kw-2">*mut</span> <span class="ident">u32</span>;
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<span class="kw">let</span> <span class="ident">volatile_ptr</span> <span class="op">=</span> <span class="ident">mut_ptr</span> <span class="kw">as</span> <span class="kw-2">*mut</span> <span class="ident">Volatile</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span>;</code></pre></div>
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<p>and then perform operations on the pointer as usual in a volatile way. This method works as all
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of the volatile wrapper types are the same size as their contained values.</p>
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</div></details><h2 id="structs" class="small-section-header"><a href="#structs">Structs</a></h2>
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<div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.ReadOnly.html" title="volatile::ReadOnly struct">ReadOnly</a></div><div class="item-right docblock-short"><p>A volatile wrapper which only allows read operations.</p>
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</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.Volatile.html" title="volatile::Volatile struct">Volatile</a></div><div class="item-right docblock-short"><p>A wrapper type around a volatile variable, which allows for volatile reads and writes
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to the contained value. The stored type needs to be <code>Copy</code>, as volatile reads and writes
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take and return copies of the value.</p>
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</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.WriteOnly.html" title="volatile::WriteOnly struct">WriteOnly</a></div><div class="item-right docblock-short"><p>A volatile wrapper which only allows write operations.</p>
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</div></div></div><h2 id="types" class="small-section-header"><a href="#types">Type Definitions</a></h2>
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<div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="type" href="type.ReadWrite.html" title="volatile::ReadWrite type">ReadWrite</a></div><div class="item-right docblock-short"><p>A volatile wrapper which allows both read and write operations;
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functionally equivalent to the <code>Volatile</code> type, as it is a type
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alias for it.</p>
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</div></div></div></section><section id="search" class="content hidden"></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="volatile" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.62.0-nightly (1f7fb6413 2022-04-10)" ></div>
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