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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="A typesafe bitmask flag generator useful for sets of C-style bitmask flags. It can be used for creating typesafe wrappers around C APIs."><meta name="keywords" content="rust, rustlang, rust-lang, bitflags"><title>bitflags - 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 defer src="../crates.js"></script><script defer src="../main.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../favicon.svg"></head><body class="rustdoc mod crate"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">&#9776;</button><a class="sidebar-logo" href="../bitflags/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div>
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        </a><h2 class="location"><a href="#">Crate bitflags</a></h2><div class="sidebar-elems"><div class="block"><ul><li class="version">Version 1.3.2</li><li><a id="all-types" href="all.html">All Items</a></li></ul></div><section><div class="block"><ul><li><a href="#macros">Macros</a></li></ul></div></section></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../bitflags/index.html"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></a><nav class="sub"><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"><div id="help-button" title="help" tabindex="-1"><button type="button">?</button></div><div id="settings-menu" tabindex="-1">
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    <h1 class="fqn"><span class="in-band">Crate <a class="mod" href="#">bitflags</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/bitflags/lib.rs.html#11-1729">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">&#x2212;</span>]</a></span></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A typesafe bitmask flag generator useful for sets of C-style bitmask flags.
It can be used for creating typesafe wrappers around C APIs.</p>
<p>The <code>bitflags!</code> macro generates <code>struct</code>s that manage a set of flags. The
flags should only be defined for integer types, otherwise unexpected type
errors may occur at compile time.</p>
<h2 id="example"><a href="#example">Example</a></h2>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;

<span class="macro">bitflags!</span> {
    <span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
        <span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
        <span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
        <span class="kw">const</span> <span class="ident">C</span> <span class="op">=</span> <span class="number">0b00000100</span>;
        <span class="kw">const</span> <span class="ident">ABC</span> <span class="op">=</span> <span class="ident"><span class="self">Self</span>::A</span>.<span class="ident">bits</span> <span class="op">|</span> <span class="ident"><span class="self">Self</span>::B</span>.<span class="ident">bits</span> <span class="op">|</span> <span class="ident"><span class="self">Self</span>::C</span>.<span class="ident">bits</span>;
    }
}

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="kw">let</span> <span class="ident">e1</span> <span class="op">=</span> <span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::C</span>;
    <span class="kw">let</span> <span class="ident">e2</span> <span class="op">=</span> <span class="ident">Flags::B</span> <span class="op">|</span> <span class="ident">Flags::C</span>;
    <span class="macro">assert_eq!</span>((<span class="ident">e1</span> <span class="op">|</span> <span class="ident">e2</span>), <span class="ident">Flags::ABC</span>);   <span class="comment">// union</span>
    <span class="macro">assert_eq!</span>((<span class="ident">e1</span> <span class="op">&amp;</span> <span class="ident">e2</span>), <span class="ident">Flags::C</span>);     <span class="comment">// intersection</span>
    <span class="macro">assert_eq!</span>((<span class="ident">e1</span> <span class="op">-</span> <span class="ident">e2</span>), <span class="ident">Flags::A</span>);     <span class="comment">// set difference</span>
    <span class="macro">assert_eq!</span>(<span class="op">!</span><span class="ident">e2</span>, <span class="ident">Flags::A</span>);           <span class="comment">// set complement</span>
}</code></pre></div>
<p>See <a href="./example_generated/struct.Flags.html"><code>example_generated::Flags</code></a> for documentation of code
generated by the above <code>bitflags!</code> expansion.</p>
<p>The generated <code>struct</code>s can also be extended with type and trait
implementations:</p>

<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">std::fmt</span>;

<span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;

<span class="macro">bitflags!</span> {
    <span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
        <span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
        <span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
    }
}

<span class="kw">impl</span> <span class="ident">Flags</span> {
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">clear</span>(<span class="kw-2">&amp;mut</span> <span class="self">self</span>) {
        <span class="self">self</span>.<span class="ident">bits</span> <span class="op">=</span> <span class="number">0</span>;  <span class="comment">// The `bits` field can be accessed from within the</span>
                        <span class="comment">// same module where the `bitflags!` macro was invoked.</span>
    }
}

<span class="kw">impl</span> <span class="ident">fmt::Display</span> <span class="kw">for</span> <span class="ident">Flags</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&amp;mut</span> <span class="ident">fmt::Formatter</span>) -&gt; <span class="ident">fmt::Result</span> {
        <span class="macro">write!</span>(<span class="ident">f</span>, <span class="string">&quot;hi!&quot;</span>)
    }
}

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">flags</span> <span class="op">=</span> <span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::B</span>;
    <span class="ident">flags</span>.<span class="ident">clear</span>();
    <span class="macro">assert!</span>(<span class="ident">flags</span>.<span class="ident">is_empty</span>());
    <span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">flags</span>), <span class="string">&quot;hi!&quot;</span>);
    <span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::B</span>), <span class="string">&quot;A | B&quot;</span>);
    <span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">Flags::B</span>), <span class="string">&quot;B&quot;</span>);
}</code></pre></div>
<h2 id="visibility"><a href="#visibility">Visibility</a></h2>
<p>The generated structs and their associated flag constants are not exported
out of the current module by default. A definition can be exported out of
the current module by adding <code>pub</code> before <code>struct</code>:</p>

<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">mod</span> <span class="ident">example</span> {
    <span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;

    <span class="macro">bitflags!</span> {
        <span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Flags1</span>: <span class="ident">u32</span> {
            <span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
        }

        <span class="kw">struct</span> <span class="ident">Flags2</span>: <span class="ident">u32</span> {
            <span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
        }
    }
}

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="kw">let</span> <span class="ident">flag1</span> <span class="op">=</span> <span class="ident">example::Flags1::A</span>;
    <span class="kw">let</span> <span class="ident">flag2</span> <span class="op">=</span> <span class="ident">example::Flags2::B</span>; <span class="comment">// error: const `B` is private</span>
}</code></pre></div>
<h2 id="attributes"><a href="#attributes">Attributes</a></h2>
<p>Attributes can be attached to the generated <code>struct</code>s by placing them
before the <code>struct</code> keyword.</p>
<h3 id="representations"><a href="#representations">Representations</a></h3>
<p>It’s valid to add a <code>#[repr(C)]</code> or <code>#[repr(transparent)]</code> attribute to a type
generated by <code>bitflags!</code>. In these cases, the type is guaranteed to be a newtype.</p>

<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;

<span class="macro">bitflags!</span> {
    <span class="attribute">#[<span class="ident">repr</span>(<span class="ident">transparent</span>)]</span>
    <span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
        <span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
        <span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
        <span class="kw">const</span> <span class="ident">C</span> <span class="op">=</span> <span class="number">0b00000100</span>;
    }
}</code></pre></div>
<h2 id="trait-implementations-1"><a href="#trait-implementations-1">Trait implementations</a></h2>
<p>The <code>Copy</code>, <code>Clone</code>, <code>PartialEq</code>, <code>Eq</code>, <code>PartialOrd</code>, <code>Ord</code> and <code>Hash</code>
traits are automatically derived for the <code>struct</code>s using the <code>derive</code> attribute.
Additional traits can be derived by providing an explicit <code>derive</code>
attribute on <code>struct</code>.</p>
<p>The <code>Extend</code> and <code>FromIterator</code> traits are implemented for the <code>struct</code>s,
too: <code>Extend</code> adds the union of the instances of the <code>struct</code> iterated over,
while <code>FromIterator</code> calculates the union.</p>
<p>The <code>Binary</code>, <code>Debug</code>, <code>LowerHex</code>, <code>Octal</code> and <code>UpperHex</code> traits are also
implemented by displaying the bits value of the internal struct.</p>
<h3 id="operators"><a href="#operators">Operators</a></h3>
<p>The following operator traits are implemented for the generated <code>struct</code>s:</p>
<ul>
<li><code>BitOr</code> and <code>BitOrAssign</code>: union</li>
<li><code>BitAnd</code> and <code>BitAndAssign</code>: intersection</li>
<li><code>BitXor</code> and <code>BitXorAssign</code>: toggle</li>
<li><code>Sub</code> and <code>SubAssign</code>: set difference</li>
<li><code>Not</code>: set complement</li>
</ul>
<h2 id="methods"><a href="#methods">Methods</a></h2>
<p>The following methods are defined for the generated <code>struct</code>s:</p>
<ul>
<li><code>empty</code>: an empty set of flags</li>
<li><code>all</code>: the set of all defined flags</li>
<li><code>bits</code>: the raw value of the flags currently stored</li>
<li><code>from_bits</code>: convert from underlying bit representation, unless that
representation contains bits that do not correspond to a
defined flag</li>
<li><code>from_bits_truncate</code>: convert from underlying bit representation, dropping
any bits that do not correspond to defined flags</li>
<li><code>from_bits_unchecked</code>: convert from underlying bit representation, keeping
all bits (even those not corresponding to defined
flags)</li>
<li><code>is_empty</code>: <code>true</code> if no flags are currently stored</li>
<li><code>is_all</code>: <code>true</code> if currently set flags exactly equal all defined flags</li>
<li><code>intersects</code>: <code>true</code> if there are flags common to both <code>self</code> and <code>other</code></li>
<li><code>contains</code>: <code>true</code> if all of the flags in <code>other</code> are contained within <code>self</code></li>
<li><code>insert</code>: inserts the specified flags in-place</li>
<li><code>remove</code>: removes the specified flags in-place</li>
<li><code>toggle</code>: the specified flags will be inserted if not present, and removed
if they are.</li>
<li><code>set</code>: inserts or removes the specified flags depending on the passed value</li>
<li><code>intersection</code>: returns a new set of flags, containing only the flags present
in both <code>self</code> and <code>other</code> (the argument to the function).</li>
<li><code>union</code>: returns a new set of flags, containing any flags present in
either <code>self</code> or <code>other</code> (the argument to the function).</li>
<li><code>difference</code>: returns a new set of flags, containing all flags present in
<code>self</code> without any of the flags present in <code>other</code> (the
argument to the function).</li>
<li><code>symmetric_difference</code>: returns a new set of flags, containing all flags
present in either <code>self</code> or <code>other</code> (the argument
to the function), but not both.</li>
<li><code>complement</code>: returns a new set of flags, containing all flags which are
not set in <code>self</code>, but which are allowed for this type.</li>
</ul>
<h3 id="default"><a href="#default">Default</a></h3>
<p>The <code>Default</code> trait is not automatically implemented for the generated structs.</p>
<p>If your default value is equal to <code>0</code> (which is the same value as calling <code>empty()</code>
on the generated struct), you can simply derive <code>Default</code>:</p>

<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;

<span class="macro">bitflags!</span> {
    <span class="comment">// Results in default value with bits: 0</span>
    <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Default</span>)]</span>
    <span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
        <span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
        <span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
        <span class="kw">const</span> <span class="ident">C</span> <span class="op">=</span> <span class="number">0b00000100</span>;
    }
}

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="kw">let</span> <span class="ident">derived_default</span>: <span class="ident">Flags</span> <span class="op">=</span> <span class="ident">Default::default</span>();
    <span class="macro">assert_eq!</span>(<span class="ident">derived_default</span>.<span class="ident">bits</span>(), <span class="number">0</span>);
}</code></pre></div>
<p>If your default value is not equal to <code>0</code> you need to implement <code>Default</code> yourself:</p>

<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;

<span class="macro">bitflags!</span> {
    <span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
        <span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
        <span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
        <span class="kw">const</span> <span class="ident">C</span> <span class="op">=</span> <span class="number">0b00000100</span>;
    }
}

<span class="comment">// explicit `Default` implementation</span>
<span class="kw">impl</span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">Flags</span> {
    <span class="kw">fn</span> <span class="ident">default</span>() -&gt; <span class="ident">Flags</span> {
        <span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::C</span>
    }
}

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="kw">let</span> <span class="ident">implemented_default</span>: <span class="ident">Flags</span> <span class="op">=</span> <span class="ident">Default::default</span>();
    <span class="macro">assert_eq!</span>(<span class="ident">implemented_default</span>, (<span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::C</span>));
}</code></pre></div>
<h2 id="zero-flags"><a href="#zero-flags">Zero Flags</a></h2>
<p>Flags with a value equal to zero will have some strange behavior that one should be aware of.</p>

<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;

<span class="macro">bitflags!</span> {
    <span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
        <span class="kw">const</span> <span class="ident">NONE</span> <span class="op">=</span> <span class="number">0b00000000</span>;
        <span class="kw">const</span> <span class="ident">SOME</span> <span class="op">=</span> <span class="number">0b00000001</span>;
    }
}

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="kw">let</span> <span class="ident">empty</span> <span class="op">=</span> <span class="ident">Flags::empty</span>();
    <span class="kw">let</span> <span class="ident">none</span> <span class="op">=</span> <span class="ident">Flags::NONE</span>;
    <span class="kw">let</span> <span class="ident">some</span> <span class="op">=</span> <span class="ident">Flags::SOME</span>;

    <span class="comment">// Zero flags are treated as always present</span>
    <span class="macro">assert!</span>(<span class="ident">empty</span>.<span class="ident">contains</span>(<span class="ident">Flags::NONE</span>));
    <span class="macro">assert!</span>(<span class="ident">none</span>.<span class="ident">contains</span>(<span class="ident">Flags::NONE</span>));
    <span class="macro">assert!</span>(<span class="ident">some</span>.<span class="ident">contains</span>(<span class="ident">Flags::NONE</span>));

    <span class="comment">// Zero flags will be ignored when testing for emptiness</span>
    <span class="macro">assert!</span>(<span class="ident">none</span>.<span class="ident">is_empty</span>());
}</code></pre></div>
<p>Users should generally avoid defining a flag with a value of zero.</p>
</div></details><h2 id="macros" class="small-section-header"><a href="#macros">Macros</a></h2>
<div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="macro" href="macro.bitflags.html" title="bitflags::bitflags macro">bitflags</a></div><div class="item-right docblock-short"><p>The macro used to generate the flag structures.</p>
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