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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'>
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
[<span class='inner'>−</span>]
</a>
</span><a class='srclink' href='../src/bitflags/lib.rs.html#300-358' 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">outer</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span>
<span class="kw">pub</span> <span class="kw">struct</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">inner</span>:<span class="ident">ident</span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="kw-2">*</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">=></span> { ... };
(
$(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">outer</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span>
<span class="kw">struct</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">inner</span>:<span class="ident">ident</span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="kw-2">*</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">=></span> { ... };
(
$(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">outer</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span>
<span class="kw">pub</span> ($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">vis</span>:<span class="ident">tt</span>)<span class="op">+</span>) <span class="kw">struct</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">inner</span>:<span class="ident">ident</span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="kw-2">*</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">=></span> { ... };
}</pre>
<div class='docblock'><p>The macro used to generate the flag structure.</p>
<p>See the <a href="../bitflags/index.html">crate level docs</a> for complete documentation.</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="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="self">Self</span>::<span class="ident">A</span>.<span class="ident">bits</span> <span class="op">|</span> <span class="self">Self</span>::<span class="ident">B</span>.<span class="ident">bits</span> <span class="op">|</span> <span class="self">Self</span>::<span class="ident">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</span>::<span class="ident">A</span> <span class="op">|</span> <span class="ident">Flags</span>::<span class="ident">C</span>;
<span class="kw">let</span> <span class="ident">e2</span> <span class="op">=</span> <span class="ident">Flags</span>::<span class="ident">B</span> <span class="op">|</span> <span class="ident">Flags</span>::<span class="ident">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">Flags</span>::<span class="ident">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">&</span> <span class="ident">e2</span>), <span class="ident">Flags</span>::<span class="ident">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">Flags</span>::<span class="ident">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">Flags</span>::<span class="ident">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="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">&</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">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></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">"hi!"</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</span>::<span class="ident">A</span> <span class="op">|</span> <span class="ident">Flags</span>::<span class="ident">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">"{}"</span>, <span class="ident">flags</span>), <span class="string">"hi!"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">Flags</span>::<span class="ident">A</span> <span class="op">|</span> <span class="ident">Flags</span>::<span class="ident">B</span>), <span class="string">"A | B"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">Flags</span>::<span class="ident">B</span>), <span class="string">"B"</span>);
}</pre>
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