<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../../../regex_syntax/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_syntax</a>::<wbr><ahref="../index.html">hir</a>::<wbr><ahref="index.html">literal</a>::<wbr><aclass="struct"href="#">Extractor</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_syntax/hir/literal.rs.html#147-153">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><code>pub struct Extractor { <spanclass="comment">/* private fields */</span> }</code></pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>Extracts prefix or suffix literal sequences from <ahref="../struct.Hir.html"title="struct regex_syntax::hir::Hir"><code>Hir</code></a> expressions.</p>
<p>Literal extraction is based on the following observations:</p>
<ul>
<li>Many regexes start with one or a small number of literals.</li>
<li>Substring search for literals is often much faster (sometimes by an order
of magnitude) than a regex search.</li>
</ul>
<p>Thus, in many cases, one can search for literals to find candidate starting
locations of a match, and then only run the full regex engine at each such
location instead of over the full haystack.</p>
<p>The main downside of literal extraction is that it can wind up causing a
search to be slower overall. For example, if there are many matches or if
there are many candidates that don’t ultimately lead to a match, then a
lot of overhead will be spent in shuffing back-and-forth between substring
search and the regex engine. This is the fundamental reason why literal
optimizations for regex patterns is sometimes considered a “black art.”</p>
</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-Extractor"class="impl"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#155-627">source</a><ahref="#impl-Extractor"class="anchor">§</a><h3class="code-header">impl <aclass="struct"href="struct.Extractor.html"title="struct regex_syntax::hir::literal::Extractor">Extractor</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.new"class="method"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#160-168">source</a><h4class="code-header">pub fn <ahref="#method.new"class="fn">new</a>() -><aclass="struct"href="struct.Extractor.html"title="struct regex_syntax::hir::literal::Extractor">Extractor</a></h4></section></summary><divclass="docblock"><p>Create a new extractor with a default configuration.</p>
<p>The extractor can be optionally configured before calling
<ahref="struct.Extractor.html#method.extract"title="method regex_syntax::hir::literal::Extractor::extract"><code>Extractor::extract</code></a> to get a literal sequence.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.extract"class="method"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#171-199">source</a><h4class="code-header">pub fn <ahref="#method.extract"class="fn">extract</a>(&self, hir: &<aclass="struct"href="../struct.Hir.html"title="struct regex_syntax::hir::Hir">Hir</a>) -><aclass="struct"href="struct.Seq.html"title="struct regex_syntax::hir::literal::Seq">Seq</a></h4></section></summary><divclass="docblock"><p>Execute the extractor and return a sequence of literals.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.kind"class="method"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#220-223">source</a><h4class="code-header">pub fn <ahref="#method.kind"class="fn">kind</a>(&mut self, kind: <aclass="enum"href="enum.ExtractKind.html"title="enum regex_syntax::hir::literal::ExtractKind">ExtractKind</a>) ->&mut <aclass="struct"href="struct.Extractor.html"title="struct regex_syntax::hir::literal::Extractor">Extractor</a></h4></section></summary><divclass="docblock"><p>Set the kind of literal sequence to extract from an <ahref="../struct.Hir.html"title="struct regex_syntax::hir::Hir"><code>Hir</code></a> expression.</p>
<p>The default is to extract prefixes, but suffixes can be selected
instead. The contract for prefixes is that every match of the
corresponding <code>Hir</code> must start with one of the literals in the sequence
returned. Moreover, the <em>order</em> of the sequence returned corresponds to
the preference order.</p>
<p>Suffixes satisfy a similar contract in that every match of the
corresponding <code>Hir</code> must end with one of the literals in the sequence
returned. However, there is no guarantee that the literals are in
preference order.</p>
<p>Remember that a sequence can be infinite. For example, unless the
limits are configured to be impractically large, attempting to extract
prefixes (or suffixes) for the pattern <code>[A-Z]</code> will return an infinite
sequence. Generally speaking, if the sequence returned is infinite,
then it is presumed to be unwise to do prefix (or suffix) optimizations
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.limit_class"class="method"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#255-258">source</a><h4class="code-header">pub fn <ahref="#method.limit_class"class="fn">limit_class</a>(&mut self, limit: <aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.usize.html">usize</a>) ->&mut <aclass="struct"href="struct.Extractor.html"title="struct regex_syntax::hir::literal::Extractor">Extractor</a></h4></section></summary><divclass="docblock"><p>Configure a limit on the length of the sequence that is permitted for
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.limit_repeat"class="method"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#292-295">source</a><h4class="code-header">pub fn <ahref="#method.limit_repeat"class="fn">limit_repeat</a>(&mut self, limit: <aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.usize.html">usize</a>) ->&mut <aclass="struct"href="struct.Extractor.html"title="struct regex_syntax::hir::literal::Extractor">Extractor</a></h4></section></summary><divclass="docblock"><p>Configure a limit on the total number of repetitions that is permitted
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.limit_literal_len"class="method"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#329-332">source</a><h4class="code-header">pub fn <ahref="#method.limit_literal_len"class="fn">limit_literal_len</a>(&mut self, limit: <aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.usize.html">usize</a>) ->&mut <aclass="struct"href="struct.Extractor.html"title="struct regex_syntax::hir::literal::Extractor">Extractor</a></h4></section></summary><divclass="docblock"><p>Configure a limit on the maximum length of any literal in a sequence.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.limit_total"class="method"><aclass="src rightside"href="../../../src/regex_syntax/hir/literal.rs.html#385-388">source</a><h4class="code-header">pub fn <ahref="#method.limit_total"class="fn">limit_total</a>(&mut self, limit: <aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.usize.html">usize</a>) ->&mut <aclass="struct"href="struct.Extractor.html"title="struct regex_syntax::hir::literal::Extractor">Extractor</a></h4></section></summary><divclass="docblock"><p>Configure a limit on the total number of literals that will be
<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>
