| <!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" href="../normalize.css"><link rel="stylesheet" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../ayu.css" disabled><link rel="stylesheet" href="../dark.css" disabled><link rel="stylesheet" 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">☰</button><a class="sidebar-logo" href="../bitflags/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../bitflags/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">Crate bitflags</a></h2><div class="sidebar-elems"><ul class="block"><li class="version">Version 1.3.2</li><li><a id="all-types" href="all.html">All Items</a></li></ul><section><ul class="block"><li><a href="#macros">Macros</a></li></ul></section></div></nav><main><div class="width-limiter"><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"><a href="../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">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></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">−</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>bitflags::bitflags; |
| |
| <span class="macro">bitflags! </span>{ |
| <span class="kw">struct </span>Flags: u32 { |
| <span class="kw">const </span>A = <span class="number">0b00000001</span>; |
| <span class="kw">const </span>B = <span class="number">0b00000010</span>; |
| <span class="kw">const </span>C = <span class="number">0b00000100</span>; |
| <span class="kw">const </span>ABC = <span class="self">Self</span>::A.bits | <span class="self">Self</span>::B.bits | <span class="self">Self</span>::C.bits; |
| } |
| } |
| |
| <span class="kw">fn </span>main() { |
| <span class="kw">let </span>e1 = Flags::A | Flags::C; |
| <span class="kw">let </span>e2 = Flags::B | Flags::C; |
| <span class="macro">assert_eq!</span>((e1 | e2), Flags::ABC); <span class="comment">// union |
| </span><span class="macro">assert_eq!</span>((e1 & e2), Flags::C); <span class="comment">// intersection |
| </span><span class="macro">assert_eq!</span>((e1 - e2), Flags::A); <span class="comment">// set difference |
| </span><span class="macro">assert_eq!</span>(!e2, Flags::A); <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>std::fmt; |
| |
| <span class="kw">use </span>bitflags::bitflags; |
| |
| <span class="macro">bitflags! </span>{ |
| <span class="kw">struct </span>Flags: u32 { |
| <span class="kw">const </span>A = <span class="number">0b00000001</span>; |
| <span class="kw">const </span>B = <span class="number">0b00000010</span>; |
| } |
| } |
| |
| <span class="kw">impl </span>Flags { |
| <span class="kw">pub fn </span>clear(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.bits = <span class="number">0</span>; <span class="comment">// The `bits` field can be accessed from within the |
| // same module where the `bitflags!` macro was invoked. |
| </span>} |
| } |
| |
| <span class="kw">impl </span>fmt::Display <span class="kw">for </span>Flags { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter) -> fmt::Result { |
| <span class="macro">write!</span>(f, <span class="string">"hi!"</span>) |
| } |
| } |
| |
| <span class="kw">fn </span>main() { |
| <span class="kw">let </span><span class="kw-2">mut </span>flags = Flags::A | Flags::B; |
| flags.clear(); |
| <span class="macro">assert!</span>(flags.is_empty()); |
| <span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">"{}"</span>, flags), <span class="string">"hi!"</span>); |
| <span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">"{:?}"</span>, Flags::A | Flags::B), <span class="string">"A | B"</span>); |
| <span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">"{:?}"</span>, Flags::B), <span class="string">"B"</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>example { |
| <span class="kw">use </span>bitflags::bitflags; |
| |
| <span class="macro">bitflags! </span>{ |
| <span class="kw">pub struct </span>Flags1: u32 { |
| <span class="kw">const </span>A = <span class="number">0b00000001</span>; |
| } |
| |
| <span class="kw">struct </span>Flags2: u32 { |
| <span class="kw">const </span>B = <span class="number">0b00000010</span>; |
| } |
| } |
| } |
| |
| <span class="kw">fn </span>main() { |
| <span class="kw">let </span>flag1 = example::Flags1::A; |
| <span class="kw">let </span>flag2 = example::Flags2::B; <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>bitflags::bitflags; |
| |
| <span class="macro">bitflags! </span>{ |
| <span class="attribute">#[repr(transparent)] |
| </span><span class="kw">struct </span>Flags: u32 { |
| <span class="kw">const </span>A = <span class="number">0b00000001</span>; |
| <span class="kw">const </span>B = <span class="number">0b00000010</span>; |
| <span class="kw">const </span>C = <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>bitflags::bitflags; |
| |
| <span class="macro">bitflags! </span>{ |
| <span class="comment">// Results in default value with bits: 0 |
| </span><span class="attribute">#[derive(Default)] |
| </span><span class="kw">struct </span>Flags: u32 { |
| <span class="kw">const </span>A = <span class="number">0b00000001</span>; |
| <span class="kw">const </span>B = <span class="number">0b00000010</span>; |
| <span class="kw">const </span>C = <span class="number">0b00000100</span>; |
| } |
| } |
| |
| <span class="kw">fn </span>main() { |
| <span class="kw">let </span>derived_default: Flags = Default::default(); |
| <span class="macro">assert_eq!</span>(derived_default.bits(), <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>bitflags::bitflags; |
| |
| <span class="macro">bitflags! </span>{ |
| <span class="kw">struct </span>Flags: u32 { |
| <span class="kw">const </span>A = <span class="number">0b00000001</span>; |
| <span class="kw">const </span>B = <span class="number">0b00000010</span>; |
| <span class="kw">const </span>C = <span class="number">0b00000100</span>; |
| } |
| } |
| |
| <span class="comment">// explicit `Default` implementation |
| </span><span class="kw">impl </span>Default <span class="kw">for </span>Flags { |
| <span class="kw">fn </span>default() -> Flags { |
| Flags::A | Flags::C |
| } |
| } |
| |
| <span class="kw">fn </span>main() { |
| <span class="kw">let </span>implemented_default: Flags = Default::default(); |
| <span class="macro">assert_eq!</span>(implemented_default, (Flags::A | Flags::C)); |
| }</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>bitflags::bitflags; |
| |
| <span class="macro">bitflags! </span>{ |
| <span class="kw">struct </span>Flags: u32 { |
| <span class="kw">const </span>NONE = <span class="number">0b00000000</span>; |
| <span class="kw">const </span>SOME = <span class="number">0b00000001</span>; |
| } |
| } |
| |
| <span class="kw">fn </span>main() { |
| <span class="kw">let </span>empty = Flags::empty(); |
| <span class="kw">let </span>none = Flags::NONE; |
| <span class="kw">let </span>some = Flags::SOME; |
| |
| <span class="comment">// Zero flags are treated as always present |
| </span><span class="macro">assert!</span>(empty.contains(Flags::NONE)); |
| <span class="macro">assert!</span>(none.contains(Flags::NONE)); |
| <span class="macro">assert!</span>(some.contains(Flags::NONE)); |
| |
| <span class="comment">// Zero flags will be ignored when testing for emptiness |
| </span><span class="macro">assert!</span>(none.is_empty()); |
| }</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">The macro used to generate the flag structures.</div></div></div></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="bitflags" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
