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<!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="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/hashbrown-0.12.3/src/raw/bitmask.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>bitmask.rs - source</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="../../../source-script.js"></script><script defer src="../../../source-files.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 source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../hashbrown/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../hashbrown/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><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="example-wrap"><pre class="src-line-numbers"><span id="1">1</span>
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</pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::imp::{BitMaskWord, BITMASK_MASK, BITMASK_STRIDE};
<span class="attribute">#[cfg(feature = <span class="string">&quot;nightly&quot;</span>)]
</span><span class="kw">use </span>core::intrinsics;
<span class="doccomment">/// A bit mask which contains the result of a `Match` operation on a `Group` and
/// allows iterating through them.
///
/// The bit mask is arranged so that low-order bits represent lower memory
/// addresses for group match results.
///
/// For implementation reasons, the bits in the set may be sparsely packed, so
/// that there is only one bit-per-byte used (the high bit, 7). If this is the
/// case, `BITMASK_STRIDE` will be 8 to indicate a divide-by-8 should be
/// performed on counts/indices to normalize this difference. `BITMASK_MASK` is
/// similarly a mask of all the actually-used bits.
</span><span class="attribute">#[derive(Copy, Clone)]
</span><span class="kw">pub struct </span>BitMask(<span class="kw">pub </span>BitMaskWord);
<span class="attribute">#[allow(clippy::use_self)]
</span><span class="kw">impl </span>BitMask {
<span class="doccomment">/// Returns a new `BitMask` with all bits inverted.
</span><span class="attribute">#[inline]
#[must_use]
</span><span class="kw">pub fn </span>invert(<span class="self">self</span>) -&gt; <span class="self">Self </span>{
BitMask(<span class="self">self</span>.<span class="number">0 </span>^ BITMASK_MASK)
}
<span class="doccomment">/// Flip the bit in the mask for the entry at the given index.
///
/// Returns the bit&#39;s previous state.
</span><span class="attribute">#[inline]
#[allow(clippy::cast_ptr_alignment)]
#[cfg(feature = <span class="string">&quot;raw&quot;</span>)]
</span><span class="kw">pub unsafe fn </span>flip(<span class="kw-2">&amp;mut </span><span class="self">self</span>, index: usize) -&gt; bool {
<span class="comment">// NOTE: The + BITMASK_STRIDE - 1 is to set the high bit.
</span><span class="kw">let </span>mask = <span class="number">1 </span>&lt;&lt; (index * BITMASK_STRIDE + BITMASK_STRIDE - <span class="number">1</span>);
<span class="self">self</span>.<span class="number">0 </span>^= mask;
<span class="comment">// The bit was set if the bit is now 0.
</span><span class="self">self</span>.<span class="number">0 </span>&amp; mask == <span class="number">0
</span>}
<span class="doccomment">/// Returns a new `BitMask` with the lowest bit removed.
</span><span class="attribute">#[inline]
#[must_use]
</span><span class="kw">pub fn </span>remove_lowest_bit(<span class="self">self</span>) -&gt; <span class="self">Self </span>{
BitMask(<span class="self">self</span>.<span class="number">0 </span>&amp; (<span class="self">self</span>.<span class="number">0 </span>- <span class="number">1</span>))
}
<span class="doccomment">/// Returns whether the `BitMask` has at least one set bit.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>any_bit_set(<span class="self">self</span>) -&gt; bool {
<span class="self">self</span>.<span class="number">0 </span>!= <span class="number">0
</span>}
<span class="doccomment">/// Returns the first set bit in the `BitMask`, if there is one.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>lowest_set_bit(<span class="self">self</span>) -&gt; <span class="prelude-ty">Option</span>&lt;usize&gt; {
<span class="kw">if </span><span class="self">self</span>.<span class="number">0 </span>== <span class="number">0 </span>{
<span class="prelude-val">None
</span>} <span class="kw">else </span>{
<span class="prelude-val">Some</span>(<span class="kw">unsafe </span>{ <span class="self">self</span>.lowest_set_bit_nonzero() })
}
}
<span class="doccomment">/// Returns the first set bit in the `BitMask`, if there is one. The
/// bitmask must not be empty.
</span><span class="attribute">#[inline]
#[cfg(feature = <span class="string">&quot;nightly&quot;</span>)]
</span><span class="kw">pub unsafe fn </span>lowest_set_bit_nonzero(<span class="self">self</span>) -&gt; usize {
intrinsics::cttz_nonzero(<span class="self">self</span>.<span class="number">0</span>) <span class="kw">as </span>usize / BITMASK_STRIDE
}
<span class="attribute">#[inline]
#[cfg(not(feature = <span class="string">&quot;nightly&quot;</span>))]
</span><span class="kw">pub unsafe fn </span>lowest_set_bit_nonzero(<span class="self">self</span>) -&gt; usize {
<span class="self">self</span>.trailing_zeros()
}
<span class="doccomment">/// Returns the number of trailing zeroes in the `BitMask`.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>trailing_zeros(<span class="self">self</span>) -&gt; usize {
<span class="comment">// ARM doesn&#39;t have a trailing_zeroes instruction, and instead uses
// reverse_bits (RBIT) + leading_zeroes (CLZ). However older ARM
// versions (pre-ARMv7) don&#39;t have RBIT and need to emulate it
// instead. Since we only have 1 bit set in each byte on ARM, we can
// use swap_bytes (REV) + leading_zeroes instead.
</span><span class="kw">if </span><span class="macro">cfg!</span>(target_arch = <span class="string">&quot;arm&quot;</span>) &amp;&amp; BITMASK_STRIDE % <span class="number">8 </span>== <span class="number">0 </span>{
<span class="self">self</span>.<span class="number">0</span>.swap_bytes().leading_zeros() <span class="kw">as </span>usize / BITMASK_STRIDE
} <span class="kw">else </span>{
<span class="self">self</span>.<span class="number">0</span>.trailing_zeros() <span class="kw">as </span>usize / BITMASK_STRIDE
}
}
<span class="doccomment">/// Returns the number of leading zeroes in the `BitMask`.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>leading_zeros(<span class="self">self</span>) -&gt; usize {
<span class="self">self</span>.<span class="number">0</span>.leading_zeros() <span class="kw">as </span>usize / BITMASK_STRIDE
}
}
<span class="kw">impl </span>IntoIterator <span class="kw">for </span>BitMask {
<span class="kw">type </span>Item = usize;
<span class="kw">type </span>IntoIter = BitMaskIter;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>into_iter(<span class="self">self</span>) -&gt; BitMaskIter {
BitMaskIter(<span class="self">self</span>)
}
}
<span class="doccomment">/// Iterator over the contents of a `BitMask`, returning the indices of set
/// bits.
</span><span class="kw">pub struct </span>BitMaskIter(BitMask);
<span class="kw">impl </span>Iterator <span class="kw">for </span>BitMaskIter {
<span class="kw">type </span>Item = usize;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>next(<span class="kw-2">&amp;mut </span><span class="self">self</span>) -&gt; <span class="prelude-ty">Option</span>&lt;usize&gt; {
<span class="kw">let </span>bit = <span class="self">self</span>.<span class="number">0</span>.lowest_set_bit()<span class="question-mark">?</span>;
<span class="self">self</span>.<span class="number">0 </span>= <span class="self">self</span>.<span class="number">0</span>.remove_lowest_bit();
<span class="prelude-val">Some</span>(bit)
}
}
</code></pre></div>
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