| <!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/tokio-1.28.2/src/util/bit.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>bit.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="../../../tokio/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="../../../tokio/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>std::fmt; |
| |
| <span class="attribute">#[derive(Clone, Copy, PartialEq)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Pack { |
| mask: usize, |
| shift: u32, |
| } |
| |
| <span class="kw">impl </span>Pack { |
| <span class="doccomment">/// Value is packed in the `width` least-significant bits. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>least_significant(width: u32) -> Pack { |
| <span class="kw">let </span>mask = mask_for(width); |
| |
| Pack { mask, shift: <span class="number">0 </span>} |
| } |
| |
| <span class="doccomment">/// Value is packed in the `width` more-significant bits. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>then(<span class="kw-2">&</span><span class="self">self</span>, width: u32) -> Pack { |
| <span class="kw">let </span>shift = pointer_width() - <span class="self">self</span>.mask.leading_zeros(); |
| <span class="kw">let </span>mask = mask_for(width) << shift; |
| |
| Pack { mask, shift } |
| } |
| |
| <span class="doccomment">/// Width, in bits, dedicated to storing the value. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>width(<span class="kw-2">&</span><span class="self">self</span>) -> u32 { |
| pointer_width() - (<span class="self">self</span>.mask >> <span class="self">self</span>.shift).leading_zeros() |
| } |
| |
| <span class="doccomment">/// Max representable value. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>max_value(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| (<span class="number">1 </span><< <span class="self">self</span>.width()) - <span class="number">1 |
| </span>} |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>pack(<span class="kw-2">&</span><span class="self">self</span>, value: usize, base: usize) -> usize { |
| <span class="macro">assert!</span>(value <= <span class="self">self</span>.max_value()); |
| (base & !<span class="self">self</span>.mask) | (value << <span class="self">self</span>.shift) |
| } |
| |
| <span class="doccomment">/// Packs the value with `base`, losing any bits of `value` that fit. |
| /// |
| /// If `value` is larger than the max value that can be represented by the |
| /// allotted width, the most significant bits are truncated. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>pack_lossy(<span class="kw-2">&</span><span class="self">self</span>, value: usize, base: usize) -> usize { |
| <span class="self">self</span>.pack(value & <span class="self">self</span>.max_value(), base) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>unpack(<span class="kw-2">&</span><span class="self">self</span>, src: usize) -> usize { |
| unpack(src, <span class="self">self</span>.mask, <span class="self">self</span>.shift) |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>Pack { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, fmt: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="macro">write!</span>( |
| fmt, |
| <span class="string">"Pack {{ mask: {:b}, shift: {} }}"</span>, |
| <span class="self">self</span>.mask, <span class="self">self</span>.shift |
| ) |
| } |
| } |
| |
| <span class="doccomment">/// Returns the width of a pointer in bits. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>pointer_width() -> u32 { |
| std::mem::size_of::<usize>() <span class="kw">as </span>u32 * <span class="number">8 |
| </span>} |
| |
| <span class="doccomment">/// Returns a `usize` with the right-most `n` bits set. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>mask_for(n: u32) -> usize { |
| <span class="kw">let </span>shift = <span class="number">1usize</span>.wrapping_shl(n - <span class="number">1</span>); |
| shift | (shift - <span class="number">1</span>) |
| } |
| |
| <span class="doccomment">/// Unpacks a value using a mask & shift. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>unpack(src: usize, mask: usize, shift: u32) -> usize { |
| (src & mask) >> shift |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |