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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><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../../../static.files/rustdoc-42caa33d.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="1.84.1 (e71f9a9a9 2025-01-27)" data-channel="1.84.1" data-search-js="search-92e6798f.js" data-settings-js="settings-0f613d39.js" ><script src="../../../../static.files/storage-59e33391.js"></script><script defer src="../sidebar-items.js"></script><script defer src="../../../../static.files/main-5f194d8c.js"></script><noscript><link rel="stylesheet" href="../../../../static.files/noscript-893ab5e7.css"></noscript><link rel="alternate icon" type="image/png" href="../../../../static.files/favicon-32x32-6580c154.png"><link rel="icon" type="image/svg+xml" href="../../../../static.files/favicon-044be391.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" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../../../memchr/index.html">memchr</a><span class="version">2.7.4</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">Module twoway</a></h2><h3><a href="#structs">Module Items</a></h3><ul class="block"><li><a href="#structs" title="Structs">Structs</a></li></ul></section><div id="rustdoc-modnav"><h2><a href="../index.html">In memchr::<wbr>arch::<wbr>all</a></h2></div></div></nav><div class="sidebar-resizer"></div><main><div class="width-limiter"><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><span class="rustdoc-breadcrumbs"><a href="../../../index.html">memchr</a>::<wbr><a href="../../index.html">arch</a>::<wbr><a href="../index.html">all</a></span><h1>Module <span>twoway</span><button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../../../../src/memchr/arch/all/twoway.rs.html#1-877">Source</a> </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">Structs<a href="#structs" class="anchor">§</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">Finder<wbr>Rev</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> |