| <!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/git/checkouts/tantivy-65d0bbbddbbd5d02/433372d/bitpacker/src/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.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="../../tantivy_bitpacker/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="../../tantivy_bitpacker/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">mod </span>bitpacker; |
| <span class="kw">mod </span>blocked_bitpacker; |
| |
| <span class="kw">pub use </span><span class="kw">crate</span>::bitpacker::{BitPacker, BitUnpacker}; |
| <span class="kw">pub use </span><span class="kw">crate</span>::blocked_bitpacker::BlockedBitpacker; |
| |
| <span class="doccomment">/// Computes the number of bits that will be used for bitpacking. |
| /// |
| /// In general the target is the minimum number of bits |
| /// required to express the amplitude given in argument. |
| /// |
| /// e.g. If the amplitude is 10, we can store all ints on simply 4bits. |
| /// |
| /// The logic is slightly more convoluted here as for optimization |
| /// reasons, we want to ensure that a value spawns over at most 8 bytes |
| /// of aligned bytes. |
| /// |
| /// Spanning over 9 bytes is possible for instance, if we do |
| /// bitpacking with an amplitude of 63 bits. |
| /// In this case, the second int will start on bit |
| /// 63 (which belongs to byte 7) and ends at byte 15; |
| /// Hence 9 bytes (from byte 7 to byte 15 included). |
| /// |
| /// To avoid this, we force the number of bits to 64bits |
| /// when the result is greater than `64-8 = 56 bits`. |
| /// |
| /// Note that this only affects rare use cases spawning over |
| /// a very large range of values. Even in this case, it results |
| /// in an extra cost of at most 12% compared to the optimal |
| /// number of bits. |
| </span><span class="kw">pub fn </span>compute_num_bits(n: u64) -> u8 { |
| <span class="kw">let </span>amplitude = (<span class="number">64u32 </span>- n.leading_zeros()) <span class="kw">as </span>u8; |
| <span class="kw">if </span>amplitude <= <span class="number">64 </span>- <span class="number">8 </span>{ |
| amplitude |
| } <span class="kw">else </span>{ |
| <span class="number">64 |
| </span>} |
| } |
| |
| <span class="kw">pub fn </span>minmax<I, T>(<span class="kw-2">mut </span>vals: I) -> <span class="prelude-ty">Option</span><(T, T)> |
| <span class="kw">where |
| </span>I: Iterator<Item = T>, |
| T: Copy + Ord, |
| { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(first_el) = vals.next() { |
| <span class="kw">return </span><span class="prelude-val">Some</span>(vals.fold((first_el, first_el), |(min_val, max_val), el| { |
| (min_val.min(el), max_val.max(el)) |
| })); |
| } |
| <span class="prelude-val">None |
| </span>} |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_compute_num_bits() { |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">1</span>), <span class="number">1u8</span>); |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">0</span>), <span class="number">0u8</span>); |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">2</span>), <span class="number">2u8</span>); |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">3</span>), <span class="number">2u8</span>); |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">4</span>), <span class="number">3u8</span>); |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">255</span>), <span class="number">8u8</span>); |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">256</span>), <span class="number">9u8</span>); |
| <span class="macro">assert_eq!</span>(compute_num_bits(<span class="number">5_000_000_000</span>), <span class="number">33u8</span>); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_minmax_empty() { |
| <span class="kw">let </span>vals: Vec<u32> = <span class="macro">vec!</span>[]; |
| <span class="macro">assert_eq!</span>(minmax(vals.into_iter()), <span class="prelude-val">None</span>); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_minmax_one() { |
| <span class="macro">assert_eq!</span>(minmax(<span class="macro">vec!</span>[<span class="number">1</span>].into_iter()), <span class="prelude-val">Some</span>((<span class="number">1</span>, <span class="number">1</span>))); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_minmax_two() { |
| <span class="macro">assert_eq!</span>(minmax(<span class="macro">vec!</span>[<span class="number">1</span>, <span class="number">2</span>].into_iter()), <span class="prelude-val">Some</span>((<span class="number">1</span>, <span class="number">2</span>))); |
| <span class="macro">assert_eq!</span>(minmax(<span class="macro">vec!</span>[<span class="number">2</span>, <span class="number">1</span>].into_iter()), <span class="prelude-val">Some</span>((<span class="number">1</span>, <span class="number">2</span>))); |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="tantivy_bitpacker" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
