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<h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>bitflags</a>::<wbr><a class="macro" href=''>bitflags</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../src/bitflags/lib.rs.html#178-496' title='goto source code'>[src]</a></span></h1>
<pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">bitflags</span> {
($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="kw">pub</span> <span class="ident">flags</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">BitFlags</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">T</span>:<span class="ident">ty</span> {
$($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag_attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="kw">const</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag</span>:<span class="ident">ident</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">value</span>:<span class="ident">expr</span>),<span class="op">+</span>
}) <span class="op">=&gt;</span> { ... };
($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="ident">flags</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">BitFlags</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">T</span>:<span class="ident">ty</span> {
$($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag_attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="kw">const</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag</span>:<span class="ident">ident</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">value</span>:<span class="ident">expr</span>),<span class="op">+</span>
}) <span class="op">=&gt;</span> { ... };
(@<span class="ident">_impl</span> <span class="ident">flags</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">BitFlags</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">T</span>:<span class="ident">ty</span> {
$($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag_attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="kw">const</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag</span>:<span class="ident">ident</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">value</span>:<span class="ident">expr</span>),<span class="op">+</span>
}) <span class="op">=&gt;</span> { ... };
($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="kw">pub</span> <span class="ident">flags</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">BitFlags</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">T</span>:<span class="ident">ty</span> {
$($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag_attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="kw">const</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag</span>:<span class="ident">ident</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">value</span>:<span class="ident">expr</span>),<span class="op">+</span>,
}) <span class="op">=&gt;</span> { ... };
($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="ident">flags</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">BitFlags</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">T</span>:<span class="ident">ty</span> {
$($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag_attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="kw">const</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag</span>:<span class="ident">ident</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">value</span>:<span class="ident">expr</span>),<span class="op">+</span>,
}) <span class="op">=&gt;</span> { ... };
}</pre>
<div class='docblock'><p>The <code>bitflags!</code> macro generates a <code>struct</code> that holds a set of C-style
bitmask flags. It is useful for creating typesafe wrappers for C APIs.</p>
<p>The flags should only be defined for integer types, otherwise unexpected
type errors may occur at compile time.</p>
<h1 id='example' class='section-header'><a href='#example'>Example</a></h1>
<pre class="rust rust-example-rendered">
<span class="attribute">#[<span class="ident">macro_use</span>]</span>
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">bitflags</span>;
<span class="macro">bitflags</span><span class="macro">!</span> {
<span class="ident">flags</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
<span class="kw">const</span> <span class="ident">FLAG_A</span> <span class="op">=</span> <span class="number">0b00000001</span>,
<span class="kw">const</span> <span class="ident">FLAG_B</span> <span class="op">=</span> <span class="number">0b00000010</span>,
<span class="kw">const</span> <span class="ident">FLAG_C</span> <span class="op">=</span> <span class="number">0b00000100</span>,
<span class="kw">const</span> <span class="ident">FLAG_ABC</span> <span class="op">=</span> <span class="ident">FLAG_A</span>.<span class="ident">bits</span>
<span class="op">|</span> <span class="ident">FLAG_B</span>.<span class="ident">bits</span>
<span class="op">|</span> <span class="ident">FLAG_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">FLAG_A</span> <span class="op">|</span> <span class="ident">FLAG_C</span>;
<span class="kw">let</span> <span class="ident">e2</span> <span class="op">=</span> <span class="ident">FLAG_B</span> <span class="op">|</span> <span class="ident">FLAG_C</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="ident">e1</span> <span class="op">|</span> <span class="ident">e2</span>), <span class="ident">FLAG_ABC</span>); <span class="comment">// union</span>
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="ident">e1</span> <span class="op">&amp;</span> <span class="ident">e2</span>), <span class="ident">FLAG_C</span>); <span class="comment">// intersection</span>
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="ident">e1</span> <span class="op">-</span> <span class="ident">e2</span>), <span class="ident">FLAG_A</span>); <span class="comment">// set difference</span>
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">e2</span>, <span class="ident">FLAG_A</span>); <span class="comment">// set complement</span>
}</pre>
<p>The generated <code>struct</code>s can also be extended with type and trait
implementations:</p>
<pre class="rust rust-example-rendered">
<span class="attribute">#[<span class="ident">macro_use</span>]</span>
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">bitflags</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;
<span class="macro">bitflags</span><span class="macro">!</span> {
<span class="ident">flags</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
<span class="kw">const</span> <span class="ident">FLAG_A</span> <span class="op">=</span> <span class="number">0b00000001</span>,
<span class="kw">const</span> <span class="ident">FLAG_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;</span><span class="kw-2">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</span>::<span class="ident">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;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="macro">write</span><span class="macro">!</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">FLAG_A</span> <span class="op">|</span> <span class="ident">FLAG_B</span>;
<span class="ident">flags</span>.<span class="ident">clear</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">flags</span>.<span class="ident">is_empty</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="macro">format</span><span class="macro">!</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">!</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">FLAG_A</span> <span class="op">|</span> <span class="ident">FLAG_B</span>), <span class="string">&quot;FLAG_A | FLAG_B&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">FLAG_B</span>), <span class="string">&quot;FLAG_B&quot;</span>);
}</pre>
<h1 id='visibility' class='section-header'><a href='#visibility'>Visibility</a></h1>
<p>The generated struct and its 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>flags</code>:</p>
<pre class="rust rust-example-rendered">
<span class="attribute">#[<span class="ident">macro_use</span>]</span>
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">bitflags</span>;
<span class="kw">mod</span> <span class="ident">example</span> {
<span class="macro">bitflags</span><span class="macro">!</span> {
<span class="kw">pub</span> <span class="ident">flags</span> <span class="ident">Flags1</span>: <span class="ident">u32</span> {
<span class="kw">const</span> <span class="ident">FLAG_A</span> <span class="op">=</span> <span class="number">0b00000001</span>,
}
}
<span class="macro">bitflags</span><span class="macro">!</span> {
<span class="ident">flags</span> <span class="ident">Flags2</span>: <span class="ident">u32</span> {
<span class="kw">const</span> <span class="ident">FLAG_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</span>::<span class="ident">FLAG_A</span>;
<span class="kw">let</span> <span class="ident">flag2</span> <span class="op">=</span> <span class="ident">example</span>::<span class="ident">FLAG_B</span>; <span class="comment">// error: const `FLAG_B` is private</span>
}</pre>
<h1 id='attributes' class='section-header'><a href='#attributes'>Attributes</a></h1>
<p>Attributes can be attached to the generated <code>struct</code> by placing them
before the <code>flags</code> keyword.</p>
<h1 id='trait-implementations' class='section-header'><a href='#trait-implementations'>Trait implementations</a></h1>
<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 automatically derived for the <code>struct</code> using the <code>derive</code> attribute.
Additional traits can be derived by providing an explicit <code>derive</code>
attribute on <code>flags</code>.</p>
<p>The <code>Extend</code> and <code>FromIterator</code> traits are implemented for the <code>struct</code>,
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>Debug</code> trait is also implemented by displaying the bits value of the
internal struct.</p>
<h2 id='operators' class='section-header'><a href='#operators'>Operators</a></h2>
<p>The following operator traits are implemented for the generated <code>struct</code>:</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>
<p>As long as the assignment operators are unstable rust feature they are only
available with the crate feature <code>assignment_ops</code> enabled.</p>
<h1 id='methods-1' class='section-header'><a href='#methods-1'>Methods</a></h1>
<p>The following methods are defined for the generated <code>struct</code>:</p>
<ul>
<li><code>empty</code>: an empty set of flags</li>
<li><code>all</code>: the set of all 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 flag</li>
<li><code>from_bits_truncate</code>: convert from underlying bit representation, dropping
any bits that do not correspond to 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 all flags are currently set</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> 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>
</ul>
</div></section>
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