<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="Defines a Thompson NFA and provides the `PikeVM` and `BoundedBacktracker` regex engines."><title>regex_automata::nfa::thompson - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../../../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../../../static.files/rustdoc-ac92e1bbe349e143.css"><metaname="rustdoc-vars"data-root-path="../../../"data-static-root-path="../../../static.files/"data-current-crate="regex_automata"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"><scriptsrc="../../../static.files/storage-f2adc0d6ca4d09fb.js"></script><scriptdefersrc="../sidebar-items.js"></script><scriptdefersrc="../../../static.files/main-305769736d49e732.js"></script><noscript><linkrel="stylesheet"href="../../../static.files/noscript-feafe1bb7466e4bd.css"></noscript><linkrel="alternate icon"type="image/png"href="../../../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../../../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../../../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc mod"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle">☰</button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../../../regex_automata/index.html">regex_automata</a><spanclass="version">0.4.5</span></h2></div><h2class="location"><ahref="#">Module thompson</a></h2><divclass="sidebar-elems"><section><ulclass="block"><li><ahref="#modules">Modules</a></li><li><ahref="#structs">Structs</a></li><li><ahref="#enums">Enums</a></li></ul></section><h2><ahref="../index.html">In regex_automata::nfa</a></h2></div></nav><divclass="sidebar-resizer"></div>
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../../../regex_automata/all.html"title="show sidebar"></a></div><inputclass="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"><divid="help-button"tabindex="-1"><ahref="../../../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../../../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Module <ahref="../../index.html">regex_automata</a>::<wbr><ahref="../index.html">nfa</a>::<wbr><aclass="mod"href="#">thompson</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../../../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../../../src/regex_automata/nfa/thompson/mod.rs.html#1-81">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>Defines a Thompson NFA and provides the <ahref="pikevm/struct.PikeVM.html"title="struct regex_automata::nfa::thompson::pikevm::PikeVM"><code>PikeVM</code></a> and
<p>A Thompson NFA (non-deterministic finite automaton) is arguably <em>the</em> central
data type in this library. It is the result of what is commonly referred to as
“regex compilation.” That is, turning a regex pattern from its concrete syntax
string into something that can run a search looks roughly like this:</p>
<ul>
<li>A <code>&str</code> is parsed into a <ahref="../../../regex_syntax/ast/enum.Ast.html"title="enum regex_syntax::ast::Ast"><code>regex-syntax::ast::Ast</code></a>.</li>
<li>An <code>Ast</code> is translated into a <ahref="../../../regex_syntax/hir/struct.Hir.html"title="struct regex_syntax::hir::Hir"><code>regex-syntax::hir::Hir</code></a>.</li>
<li>An <code>Hir</code> is compiled into a <ahref="struct.NFA.html"title="struct regex_automata::nfa::thompson::NFA"><code>NFA</code></a>.</li>
<li>The <code>NFA</code> is then used to build one of a few different regex engines:
<ul>
<li>An <code>NFA</code> is used directly in the <code>PikeVM</code> and <code>BoundedBacktracker</code> engines.</li>
<li>Parsing a string into an <code>Ast</code> gives it a structured representation.
Crucially, the size and amount of work done in this step is proportional to the
size of the original string. No optimization or Unicode handling is done at
this point. This means that parsing into an <code>Ast</code> has very predictable costs.
Moreover, an <code>Ast</code> can be roundtripped back to its original pattern string as
written.</li>
<li>Translating an <code>Ast</code> into an <code>Hir</code> is a process by which the structured
representation is simplified down to its most fundamental components.
Translation deals with flags such as case insensitivity by converting things
like <code>(?i:a)</code> to <code>[Aa]</code>. Translation is also where Unicode tables are consulted
to resolve things like <code>\p{Emoji}</code> and <code>\p{Greek}</code>. It also flattens each
character class, regardless of how deeply nested it is, into a single sequence
of non-overlapping ranges. All the various literal forms are thrown out in
favor of one common representation. Overall, the <code>Hir</code> is small enough to fit
into your head and makes analysis and other tasks much simpler.</li>
<li>Compiling an <code>Hir</code> into an <code>NFA</code> formulates the regex into a finite state
machine whose transitions are defined over bytes. For example, an <code>Hir</code> might
have a Unicode character class corresponding to a sequence of ranges defined
in terms of <code>char</code>. Compilation is then responsible for turning those ranges
into a UTF-8 automaton. That is, an automaton that matches the UTF-8 encoding
of just the codepoints specified by those ranges. Otherwise, the main job of
an <code>NFA</code> is to serve as a byte-code of sorts for a virtual machine. It can be
seen as a sequence of instructions for how to match a regex.</li>
</ul>
</div></details><h2id="modules"class="section-header"><ahref="#modules">Modules</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="mod"href="pikevm/index.html"title="mod regex_automata::nfa::thompson::pikevm">pikevm</a></div><divclass="desc docblock-short">An NFA backed Pike VM for executing regex searches with capturing groups.</div></li></ul><h2id="structs"class="section-header"><ahref="#structs">Structs</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="struct"href="struct.BuildError.html"title="struct regex_automata::nfa::thompson::BuildError">BuildError</a></div><divclass="desc docblock-short">An error that can occurred during the construction of a thompson NFA.</div></li><li><divclass="item-name"><aclass="struct"href="struct.Builder.html"title="struct regex_automata::nfa::thompson::Builder">Builder</a></div><divclass="desc docblock-short">An abstraction for building Thompson NFAs by hand.</div></li><li><divclass="item-name"><aclass="struct"href="struct.Compiler.html"title="struct regex_automata::nfa::thompson::Compiler">Compiler</a></div><divclass="desc docblock-short">A builder for compiling an NFA from a regex’s high-level intermediate
representation (HIR).</div></li><li><divclass="item-name"><aclass="struct"href="struct.Config.html"title="struct regex_automata::nfa::thompson::Config">Config</a></div><divclass="desc docblock-short">The configuration used for a Thompson NFA compiler.</div></li><li><divclass="item-name"><aclass="struct"href="struct.DenseTransitions.html"title="struct regex_automata::nfa::thompson::DenseTransitions">DenseTransitions</a></div><divclass="desc docblock-short">A sequence of transitions used to represent a dense state.</div></li><li><divclass="item-name"><aclass="struct"href="struct.NFA.html"title="struct regex_automata::nfa::thompson::NFA">NFA</a></div><divclass="desc docblock-short">A byte oriented Thompson non-deterministic finite automaton (NFA).</div></li><li><divclass="item-name"><aclass="struct"href="struct.PatternIter.html"title="struct regex_automata::nfa::thompson::PatternIter">PatternIter</a></div><divclass="desc docblock-short">An iterator over all pattern IDs in an NFA.</div></li><li><divclass="item-name"><aclass="struct"href="struct.SparseTransitions.html"title="struct regex_automata::nfa::thompson::SparseTransitions">SparseTransitions</a></div><divclass="desc docblock-short">A sequence of transitions used to represent a sparse state.</div></li><li><divclass="item-name"><aclass="struct"href="struct.Transition.html"title="struct regex_automata::nfa::thompson::Transition">Transition</a></div><divclass="desc docblock-short">A single transition to another state.</div></li></ul><h2id="enums"class="section-header"><ahref="#enums">Enums</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="enum"href="enum.State.html"title="enum regex_automata::nfa::thompson::State">State</a></div><divclass="desc docblock-short">A state in an NFA.</div></li><li><divclass="item-name"><aclass="enum"href="enum.WhichCaptures.html"title="enum regex_automata::nfa::thompson::WhichCaptures">WhichCaptures</a></div><divclass="desc docblock-short">A configuration indicating which kinds of
<ahref="enum.State.html#variant.Capture"title="variant regex_automata::nfa::thompson::State::Capture"><code>State::Capture</code></a> states to include.</div></li></ul></section></div></main></body></html>
