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Juniper Documentation Builder 95d942c9d4 Update documentation for Juniper
2016-09-11 18:41:24 +00:00

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<section id='main' class="content macro">
<h1 class='fqn'><span class='in-band'><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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<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='kw-2'>&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>
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