<!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="The configuration used to determine a DFA’s start state for a search."><title>Config in regex_automata::util::start - 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-5bc39a1768837dd0.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="1.77.1 (7cf61ebde 2024-03-27)"data-channel="1.77.1"data-search-js="search-dd67cee4cfa65049.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../../../static.files/storage-4c98445ec4002617.js"></script><scriptdefersrc="sidebar-items.js"></script><scriptdefersrc="../../../static.files/main-48f368f3872407c8.js"></script><noscript><linkrel="stylesheet"href="../../../static.files/noscript-04d5337699b92874.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 struct"><!--[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"title="show sidebar"></button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../../../regex_automata/index.html">regex_automata</a><spanclass="version">0.4.6</span></h2></div><h2class="location"><ahref="#">Config</a></h2><divclass="sidebar-elems"><section><h3><ahref="#implementations">Methods</a></h3><ulclass="block method"><li><ahref="#method.anchored">anchored</a></li><li><ahref="#method.from_input_forward">from_input_forward</a></li><li><ahref="#method.from_input_reverse">from_input_reverse</a></li><li><ahref="#method.get_anchored">get_anchored</a></li><li><ahref="#method.get_look_behind">get_look_behind</a></li><li><ahref="#method.look_behind">look_behind</a></li><li><ahref="#method.new">new</a></li></ul><h3><ahref="#trait-implementations">Trait Implementations</a></h3><ulclass="block trait-implementation"><li><ahref="#impl-Clone-for-Config">Clone</a></li><li><ahref="#impl-Debug-for-Config">Debug</a></li></ul><h3><ahref="#synthetic-implementations">Auto Trait Implementations</a></h3><ulclass="block synthetic-implementation"><li><ahref="#impl-RefUnwindSafe-for-Config">RefUnwindSafe</a></li><li><ahref="#impl-Send-for-Config">Send</a></li><li><ahref="#impl-Sync-for-Config">Sync</a></li><li><ahref="#impl-Unpin-for-Config">Unpin</a></li><li><ahref="#impl-UnwindSafe-for-Config">UnwindSafe</a></li></ul><h3><ahref="#blanket-implementations">Blanket Implementations</a></h3><ulclass="block blanket-implementation"><li><ahref="#impl-Any-for-T">Any</a></li><li><ahref="#impl-Borrow%3CT%3E-for-T">Borrow<T></a></li><li><ahref="#impl-BorrowMut%3CT%3E-for-T">BorrowMut<T></a></li><li><ahref="#impl-From%3CT%3E-for-T">From<T></a></li><li><ahref="#impl-Into%3CU
<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>Struct <ahref="../../index.html">regex_automata</a>::<wbr><ahref="../index.html">util</a>::<wbr><ahref="index.html">start</a>::<wbr><aclass="struct"href="#">Config</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/util/start.rs.html#121-124">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><code>pub struct Config { <spanclass="comment">/* private fields */</span> }</code></pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>The configuration used to determine a DFA’s start state for a search.</p>
<p>A DFA has a single starting state in the typical textbook description. That
is, it corresponds to the set of all starting states for the NFA that built
it, along with their espsilon closures. In this crate, however, DFAs have
many possible start states due to a few factors:</p>
<ul>
<li>DFAs support the ability to run either anchored or unanchored searches.
Each type of search needs its own start state. For example, an unanchored
search requires starting at a state corresponding to a regex with a
<code>(?s-u:.)*?</code> prefix, which will match through anything.</li>
<li>DFAs also optionally support starting an anchored search for any one
specific pattern. Each such pattern requires its own start state.</li>
<li>If a look-behind assertion like <code>^</code> or <code>\b</code> is used in the regex, then
the DFA will need to inspect a single byte immediately before the start of
the search to choose the correct start state.</li>
</ul>
<p>Indeed, this configuration precisely encapsulates all of the above factors.
The <ahref="struct.Config.html#method.anchored"title="method regex_automata::util::start::Config::anchored"><code>Config::anchored</code></a> method sets which kind of anchored search to
perform while the <ahref="struct.Config.html#method.look_behind"title="method regex_automata::util::start::Config::look_behind"><code>Config::look_behind</code></a> method provides a way to set
the byte that occurs immediately before the start of the search.</p>
<p>Generally speaking, this type is only useful when you want to run searches
without using an <ahref="../../struct.Input.html"title="struct regex_automata::Input"><code>Input</code></a>. In particular, an <code>Input</code> wants a haystack
slice, but callers may not have a contiguous sequence of bytes as a
haystack in all cases. This type provides a lower level of control such
that callers can provide their own anchored configuration and look-behind
</div></details><h2id="implementations"class="section-header">Implementations<ahref="#implementations"class="anchor">§</a></h2><divid="implementations-list"><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Config"class="impl"><aclass="src rightside"href="../../../src/regex_automata/util/start.rs.html#126-191">source</a><ahref="#impl-Config"class="anchor">§</a><h3class="code-header">impl <aclass="struct"href="struct.Config.html"title="struct regex_automata::util::start::Config">Config</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.new"class="method"><aclass="src rightside"href="../../../src/regex_automata/util/start.rs.html#131-133">source</a><h4class="code-header">pub fn <ahref="#method.new"class="fn">new</a>() -><aclass="struct"href="struct.Config.html"title="struct regex_automata::util::start::Config">Config</a></h4></section></summary><divclass="docblock"><p>Create a new default start configuration.</p>
<p>The default is an unanchored search that starts at the beginning of the
haystack.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.from_input_forward"class="method"><aclass="src rightside"href="../../../src/regex_automata/util/start.rs.html#141-147">source</a><h4class="code-header">pub fn <ahref="#method.from_input_forward"class="fn">from_input_forward</a>(input: &<aclass="struct"href="../../struct.Input.html"title="struct regex_automata::Input">Input</a><'_>) -><aclass="struct"href="struct.Config.html"title="struct regex_automata::util::start::Config">Config</a></h4></section></summary><divclass="docblock"><p>A convenience routine for building a start configuration from an
<ahref="../../struct.Input.html"title="struct regex_automata::Input"><code>Input</code></a> for a forward search.</p>
<p>This automatically sets the look-behind byte to the byte immediately
preceding the start of the search. If the start of the search is at
offset <code>0</code>, then no look-behind byte is set.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.from_input_reverse"class="method"><aclass="src rightside"href="../../../src/regex_automata/util/start.rs.html#155-158">source</a><h4class="code-header">pub fn <ahref="#method.from_input_reverse"class="fn">from_input_reverse</a>(input: &<aclass="struct"href="../../struct.Input.html"title="struct regex_automata::Input">Input</a><'_>) -><aclass="struct"href="struct.Config.html"title="struct regex_automata::util::start::Config">Config</a></h4></section></summary><divclass="docblock"><p>A convenience routine for building a start configuration from an
<ahref="../../struct.Input.html"title="struct regex_automata::Input"><code>Input</code></a> for a reverse search.</p>
<p>This automatically sets the look-behind byte to the byte immediately
following the end of the search. If the end of the search is at
offset <code>haystack.len()</code>, then no look-behind byte is set.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.look_behind"class="method"><aclass="src rightside"href="../../../src/regex_automata/util/start.rs.html#169-172">source</a><h4class="code-header">pub fn <ahref="#method.look_behind"class="fn">look_behind</a>(self, byte: <aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/option/enum.Option.html"title="enum core::option::Option">Option</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.u8.html">u8</a>>) -><aclass="struct"href="struct.Config.html"title="struct regex_automata::util::start::Config">Config</a></h4></section></summary><divclass="docblock"><p>Set the look-behind byte at the start of a search.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.get_look_behind"class="method"><aclass="src rightside"href="../../../src/regex_automata/util/start.rs.html#183-185">source</a><h4class="code-header">pub fn <ahref="#method.get_look_behind"class="fn">get_look_behind</a>(&self) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/option/enum.Option.html"title="enum core::option::Option">Option</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.u8.html">u8</a>></h4></section></summary><divclass="docblock"><p>Return the look-behind byte in this configuration, if one exists.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.get_anchored"class="method"><aclass="src rightside"href="../../../src/regex_automata/util/start.rs.html#188-190">source</a><h4class="code-header">pub fn <ahref="#method.get_anchored"class="fn">get_anchored</a>(&self) -><aclass="enum"href="../../enum.Anchored.html"title="enum regex_automata::Anchored">Anchored</a></h4></section></summary><divclass="docblock"><p>Return the anchored mode in this configuration.</p>
<code><ahref="https://doc.rust-lang.org/1.77.1/core/convert/trait.From.html"title="trait core::convert::From">From</a><T> for U</code> chooses to do.</p>
</div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-ToOwned-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.1/src/alloc/borrow.rs.html#83-85">source</a><ahref="#impl-ToOwned-for-T"class="anchor">§</a><h3class="code-header">impl<T><aclass="trait"href="https://doc.rust-lang.org/1.77.1/alloc/borrow/trait.ToOwned.html"title="trait alloc::borrow::ToOwned">ToOwned</a> for T<divclass="where">where
T: <aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/clone/trait.Clone.html"title="trait core::clone::Clone">Clone</a>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Owned"class="associatedtype trait-impl"><ahref="#associatedtype.Owned"class="anchor">§</a><h4class="code-header">type <ahref="https://doc.rust-lang.org/1.77.1/alloc/borrow/trait.ToOwned.html#associatedtype.Owned"class="associatedtype">Owned</a> = T</h4></section></summary><divclass='docblock'>The resulting type after obtaining ownership.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.to_owned"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.1/src/alloc/borrow.rs.html#88">source</a><ahref="#method.to_owned"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.1/alloc/borrow/trait.ToOwned.html#tymethod.to_owned"class="fn">to_owned</a>(&self) -> T</h4></section></summary><divclass='docblock'>Creates owned data from borrowed data, usually by cloning. <ahref="https://doc.rust-lang.org/1.77.1/alloc/borrow/trait.ToOwned.html#tymethod.to_owned">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.clone_into"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.1/src/alloc/borrow.rs.html#92">source</a><ahref="#method.clone_into"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.1/alloc/borrow/trait.ToOwned.html#method.clone_into"class="fn">clone_into</a>(&self, target: <aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.reference.html">&mut T</a>)</h4></section></summary><divclass='docblock'>Uses borrowed data to replace owned data, usually by cloning. <ahref="https://doc.rust-lang.org/1.77.1/alloc/borrow/trait.ToOwned.html#method.clone_into">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-TryFrom%3CU%3E-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.1/src/core/convert/mod.rs.html#804-806">source</a><ahref="#impl-TryFrom%3CU%3E-for-T"class="anchor">§</a><h3class="code-header">impl<T, U><aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><U> for T<divclass="where">where
U: <aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.Into.html"title="trait core::convert::Into">Into</a><T>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Error-1"class="associatedtype trait-impl"><ahref="#associatedtype.Error-1"class="anchor">§</a><h4class="code-header">type <ahref="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html#associatedtype.Error"class="associatedtype">Error</a> = <aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/convert/enum.Infallible.html"title="enum core::convert::Infallible">Infallible</a></h4></section></summary><divclass='docblock'>The type returned in the event of a conversion error.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.try_from"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.1/src/core/convert/mod.rs.html#811">source</a><ahref="#method.try_from"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html#tymethod.try_from"class="fn">try_from</a>(value: U) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/result/enum.Result.html"title="enum core::result::Result">Result</a><T, <T as <aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><U>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html#associatedtype.Error"title="type core::convert::TryFrom::Error">Error</a>></h4></section></summary><divclass='docblock'>Performs the conversion.</div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-TryInto%3CU%3E-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.1/src/core/convert/mod.rs.html#789-791">source</a><ahref="#impl-TryInto%3CU%3E-for-T"class="anchor">§</a><h3class="code-header">impl<T, U><aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryInto.html"title="trait core::convert::TryInto">TryInto</a><U> for T<divclass="where">where
U: <aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Error"class="associatedtype trait-impl"><ahref="#associatedtype.Error"class="anchor">§</a><h4class="code-header">type <ahref="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryInto.html#associatedtype.Error"class="associatedtype">Error</a> = <U as <aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html#associatedtype.Error"title="type core::convert::TryFrom::Error">Error</a></h4></section></summary><divclass='docblock'>The type returned in the event of a conversion error.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.try_into"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.1/src/core/convert/mod.rs.html#796">source</a><ahref="#method.try_into"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryInto.html#tymethod.try_into"class="fn">try_into</a>(self) -><aclass="enum"href="https://doc.rust-lang.org/1.77.1/core/result/enum.Result.html"title="enum core::result::Result">Result</a><U, <U as <aclass="trait"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.77.1/core/convert/trait.TryFrom.html#associatedtype.Error"title="type core::convert::TryFrom::Error">Error</a>></h4></section></summary><divclass='docblock'>Performs the conversion.</div></details></div></details></div></section></div></main></body></html>
