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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="An implementation of the Two-Way substring search algorithm."><title>memchr::arch::all::twoway - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../../../../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../../../../static.files/rustdoc-ac92e1bbe349e143.css"><meta name="rustdoc-vars" data-root-path="../../../../" data-static-root-path="../../../../static.files/" data-current-crate="memchr" data-themes="" data-resource-suffix="" data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)" data-channel="1.76.0" data-search-js="search-2b6ce74ff89ae146.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../../../../static.files/storage-f2adc0d6ca4d09fb.js"></script><script defer src="../sidebar-items.js"></script><script defer src="../../../../static.files/main-305769736d49e732.js"></script><noscript><link rel="stylesheet" href="../../../../static.files/noscript-feafe1bb7466e4bd.css"></noscript><link rel="alternate icon" type="image/png" href="../../../../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../../../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc mod"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../../../memchr/index.html">memchr</a><span class="version">2.7.1</span></h2></div><h2 class="location"><a href="#">Module twoway</a></h2><div class="sidebar-elems"><section><ul class="block"><li><a href="#structs">Structs</a></li></ul></section><h2><a href="../index.html">In memchr::arch::all</a></h2></div></nav><div class="sidebar-resizer"></div>
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<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../../../../memchr/all.html" title="show sidebar"></a></div><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" tabindex="-1"><a href="../../../../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Module <a href="../../../index.html">memchr</a>::<wbr><a href="../../index.html">arch</a>::<wbr><a href="../index.html">all</a>::<wbr><a class="mod" href="#">twoway</a><button id="copy-path" title="Copy item path to clipboard"><img src="../../../../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../../../../src/memchr/arch/all/twoway.rs.html#1-877">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>An implementation of the <a href="https://en.wikipedia.org/wiki/Two-way_string-matching_algorithm">Two-Way substring search algorithm</a>.</p>
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<p><a href="struct.Finder.html" title="struct memchr::arch::all::twoway::Finder"><code>Finder</code></a> can be built for forward searches, while <a href="struct.FinderRev.html" title="struct memchr::arch::all::twoway::FinderRev"><code>FinderRev</code></a> can be built
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for reverse searches.</p>
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<p>Two-Way makes for a nice general purpose substring search algorithm because of
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its time and space complexity properties. It also performs well in practice.
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Namely, with <code>m = len(needle)</code> and <code>n = len(haystack)</code>, Two-Way takes <code>O(m)</code>
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time to create a finder, <code>O(1)</code> space and <code>O(n)</code> search time. In other words,
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the preprocessing step is quick, doesn’t require any heap memory and the worst
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case search time is guaranteed to be linear in the haystack regardless of the
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size of the needle.</p>
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<p>While vector algorithms will usually beat Two-Way handedly, vector algorithms
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also usually have pathological or edge cases that are better handled by Two-Way.
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Moreover, not all targets support vector algorithms or implementations for them
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simply may not exist yet.</p>
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<p>Two-Way can be found in the <code>memmem</code> implementations in at least <a href="https://www.gnu.org/software/libc/">GNU libc</a> and
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<a href="https://www.musl-libc.org/">musl</a>.</p>
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</div></details><h2 id="structs" class="section-header"><a href="#structs">Structs</a></h2><ul class="item-table"><li><div class="item-name"><a class="struct" href="struct.Finder.html" title="struct memchr::arch::all::twoway::Finder">Finder</a></div><div class="desc docblock-short">A forward substring searcher that uses the Two-Way algorithm.</div></li><li><div class="item-name"><a class="struct" href="struct.FinderRev.html" title="struct memchr::arch::all::twoway::FinderRev">FinderRev</a></div><div class="desc docblock-short">A reverse substring searcher that uses the Two-Way algorithm.</div></li></ul></section></div></main></body></html>
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