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Update documentation
2018-08-22 17:04:13 +00:00
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<p class='location'>Crate bitflags</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#macros">Macros</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'bitflags', ty: 'mod', relpath: '../'};</script></div>
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<h1 class='fqn'><span class='in-band'>Crate <a class="mod" 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#11-1229' title='goto source code'>[src]</a></span></h1>
<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 a <code>struct</code> that manages a set of flags. 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="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">&amp;</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>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>
<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">&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">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">&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">Flags</span>::<span class="ident">A</span> <span class="op">|</span> <span class="ident">Flags</span>::<span class="ident">B</span>), <span class="string">&quot;A | 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">Flags</span>::<span class="ident">B</span>), <span class="string">&quot;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="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="macro">bitflags</span><span class="macro">!</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</span>::<span class="ident">Flags1</span>::<span class="ident">A</span>;
<span class="kw">let</span> <span class="ident">flag2</span> <span class="op">=</span> <span class="ident">example</span>::<span class="ident">Flags2</span>::<span class="ident">B</span>; <span class="comment">// error: const `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>Binary</code>, <code>Debug</code>, <code>LowerExp</code>, <code>Octal</code> and <code>UpperExp</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>
<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>
<li><code>set</code>: inserts or removes the specified flags depending on the passed value</li>
</ul>
<h2 id="default" class="section-header"><a href="#default">Default</a></h2>
<p>The <code>Default</code> trait is not automatically implemented for the generated struct.</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>
<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="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</span>::<span class="ident">default</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">derived_default</span>.<span class="ident">bits</span>(), <span class="number">0</span>);
}</pre>
<p>If your default value is not equal to <code>0</code> you need to implement <code>Default</code> yourself:</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="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="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>() <span class="op">-&gt;</span> <span class="ident">Flags</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">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</span>::<span class="ident">default</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">implemented_default</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>));
}</pre>
<h1 id="zero-flags" class="section-header"><a href="#zero-flags">Zero Flags</a></h1>
<p>Flags with a value equal to zero will have some strange behavior that one should be aware of.</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="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">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</span>::<span class="ident">empty</span>();
<span class="kw">let</span> <span class="ident">none</span> <span class="op">=</span> <span class="ident">Flags</span>::<span class="ident">NONE</span>;
<span class="kw">let</span> <span class="ident">some</span> <span class="op">=</span> <span class="ident">Flags</span>::<span class="ident">SOME</span>;
<span class="comment">// Zero flags are treated as always present</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">empty</span>.<span class="ident">contains</span>(<span class="ident">Flags</span>::<span class="ident">NONE</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">none</span>.<span class="ident">contains</span>(<span class="ident">Flags</span>::<span class="ident">NONE</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">some</span>.<span class="ident">contains</span>(<span class="ident">Flags</span>::<span class="ident">NONE</span>));
<span class="comment">// Zero flags will be ignored when testing for emptiness</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">none</span>.<span class="ident">is_empty</span>());
}</pre>
</div><h2 id='macros' class='section-header'><a href="#macros">Macros</a></h2>
<table>
<tr class=' module-item'>
<td><a class="macro" href="macro.bitflags.html"
title='macro bitflags::bitflags'>bitflags</a></td>
<td class='docblock-short'>
<p>The macro used to generate the flag structure.</p>
</td>
</tr></table></section>
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