<!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="A pair of byte offsets into a needle to use as a predicate."><title>Pair in memchr::arch::all::packedpair - 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="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"><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 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">☰</button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../../../../memchr/index.html">memchr</a><spanclass="version">2.7.1</span></h2></div><h2class="location"><ahref="#">Pair</a></h2><divclass="sidebar-elems"><section><h3><ahref="#implementations">Methods</a></h3><ulclass="block method"><li><ahref="#method.index1">index1</a></li><li><ahref="#method.index2">index2</a></li><li><ahref="#method.new">new</a></li><li><ahref="#method.with_indices">with_indices</a></li><li><ahref="#method.with_ranker">with_ranker</a></li></ul><h3><ahref="#trait-implementations">Trait Implementations</a></h3><ulclass="block trait-implementation"><li><ahref="#impl-Clone-for-Pair">Clone</a></li><li><ahref="#impl-Copy-for-Pair">Copy</a></li><li><ahref="#impl-Debug-for-Pair">Debug</a></li></ul><h3><ahref="#synthetic-implementations">Auto Trait Implementations</a></h3><ulclass="block synthetic-implementation"><li><ahref="#impl-RefUnwindSafe-for-Pair">RefUnwindSafe</a></li><li><ahref="#impl-Send-for-Pair">Send</a></li><li><ahref="#impl-Sync-for-Pair">Sync</a></li><li><ahref="#impl-Unpin-for-Pair">Unpin</a></li><li><ahref="#impl-UnwindSafe-for-Pair">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%3E-for-T">Into<U></a></li><li><ahref="#impl-ToOwned-for-T">ToOwned</a></li><li><ahref="#impl-TryFrom%3CU%3E-for-T">TryFr
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../../../../memchr/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">memchr</a>::<wbr><ahref="../../index.html">arch</a>::<wbr><ahref="../index.html">all</a>::<wbr><ahref="index.html">packedpair</a>::<wbr><aclass="struct"href="#">Pair</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/memchr/arch/all/packedpair/mod.rs.html#135-138">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><code>pub struct Pair { <spanclass="comment">/* private fields */</span> }</code></pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>A pair of byte offsets into a needle to use as a predicate.</p>
<p>This pair is used as a predicate to quickly filter out positions in a
haystack in which a needle cannot match. In some cases, this pair can even
be used in vector algorithms such that the vector algorithm only switches
over to scalar code once this pair has been found.</p>
<p>A pair of offsets can be used in both substring search implementations and
in prefilters. The former will report matches of a needle in a haystack
where as the latter will only report possible matches of a needle.</p>
<p>The offsets are limited each to a maximum of 255 to keep memory usage low.
Moreover, it’s rarely advantageous to create a predicate using offsets
greater than 255 anyway.</p>
<p>The only guarantee enforced on the pair of offsets is that they are not
equivalent. It is not necessarily the case that <code>index1 < index2</code> for
example. By convention, <code>index1</code> corresponds to the byte in the needle
that is believed to be most the predictive. Note also that because of the
requirement that the indices be both valid for the needle used to build
the pair and not equal, it follows that a pair can only be constructed for
</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-Pair"class="impl"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#140-247">source</a><ahref="#impl-Pair"class="anchor">§</a><h3class="code-header">impl <aclass="struct"href="struct.Pair.html"title="struct memchr::arch::all::packedpair::Pair">Pair</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.new"class="method"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#149-151">source</a><h4class="code-header">pub fn <ahref="#method.new"class="fn">new</a>(needle: &[<aclass="primitive"href="https://doc.rust-lang.org/1.76.0/std/primitive.u8.html">u8</a>]) -><aclass="enum"href="https://doc.rust-lang.org/1.76.0/core/option/enum.Option.html"title="enum core::option::Option">Option</a><<aclass="struct"href="struct.Pair.html"title="struct memchr::arch::all::packedpair::Pair">Pair</a>></h4></section></summary><divclass="docblock"><p>Create a new pair of offsets from the given needle.</p>
) -><aclass="enum"href="https://doc.rust-lang.org/1.76.0/core/option/enum.Option.html"title="enum core::option::Option">Option</a><<aclass="struct"href="struct.Pair.html"title="struct memchr::arch::all::packedpair::Pair">Pair</a>></h4></section></summary><divclass="docblock"><p>Create a new pair of offsets from the given needle and ranker.</p>
<p>This permits the caller to choose a background frequency distribution
with which bytes are selected. The idea is to select a pair of bytes
that is believed to strongly predict a match in the haystack. This
usually means selecting bytes that occur rarely in a haystack.</p>
<p>If a pair could not be created (for example, if the needle is too
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.with_indices"class="method"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#214-234">source</a><h4class="code-header">pub fn <ahref="#method.with_indices"class="fn">with_indices</a>(needle: &[<aclass="primitive"href="https://doc.rust-lang.org/1.76.0/std/primitive.u8.html">u8</a>], index1: <aclass="primitive"href="https://doc.rust-lang.org/1.76.0/std/primitive.u8.html">u8</a>, index2: <aclass="primitive"href="https://doc.rust-lang.org/1.76.0/std/primitive.u8.html">u8</a>) -><aclass="enum"href="https://doc.rust-lang.org/1.76.0/core/option/enum.Option.html"title="enum core::option::Option">Option</a><<aclass="struct"href="struct.Pair.html"title="struct memchr::arch::all::packedpair::Pair">Pair</a>></h4></section></summary><divclass="docblock"><p>Create a new pair using the offsets given for the needle given.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.index1"class="method"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#238-240">source</a><h4class="code-header">pub fn <ahref="#method.index1"class="fn">index1</a>(&self) -><aclass="primitive"href="https://doc.rust-lang.org/1.76.0/std/primitive.u8.html">u8</a></h4></section></summary><divclass="docblock"><p>Returns the first offset of the pair.</p>
</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.index2"class="method"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#244-246">source</a><h4class="code-header">pub fn <ahref="#method.index2"class="fn">index2</a>(&self) -><aclass="primitive"href="https://doc.rust-lang.org/1.76.0/std/primitive.u8.html">u8</a></h4></section></summary><divclass="docblock"><p>Returns the second offset of the pair.</p>
</div></details></div></details></div><h2id="trait-implementations"class="section-header">Trait Implementations<ahref="#trait-implementations"class="anchor">§</a></h2><divid="trait-implementations-list"><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Clone-for-Pair"class="impl"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#134">source</a><ahref="#impl-Clone-for-Pair"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.76.0/core/clone/trait.Clone.html"title="trait core::clone::Clone">Clone</a> for <aclass="struct"href="struct.Pair.html"title="struct memchr::arch::all::packedpair::Pair">Pair</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.clone"class="method trait-impl"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#134">source</a><ahref="#method.clone"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.76.0/core/clone/trait.Clone.html#tymethod.clone"class="fn">clone</a>(&self) -><aclass="struct"href="struct.Pair.html"title="struct memchr::arch::all::packedpair::Pair">Pair</a></h4></section></summary><divclass='docblock'>Returns a copy of the value. <ahref="https://doc.rust-lang.org/1.76.0/core/clone/trait.Clone.html#tymethod.clone">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.clone_from"class="method trait-impl"><spanclass="rightside"><spanclass="since"title="Stable since Rust version 1.0.0">1.0.0</span> · <aclass="src"href="https://doc.rust-lang.org/1.76.0/src/core/clone.rs.html#169">source</a></span><ahref="#method.clone_from"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.76.0/core/clone/trait.Clone.html#method.clone_from"class="fn">clone_from</a>(&mut self, source: <aclass="primitive"href="https://doc.rust-lang.org/1.76.0/std/primitive.reference.html">&Self</a>)</h4></section></summary><divclass='docblock'>Performs copy-assignment from <code>source</code>. <ahref="https://doc.rust-lang.org/1.76.0/core/clone/trait.Clone.html#method.clone_from">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Debug-for-Pair"class="impl"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#134">source</a><ahref="#impl-Debug-for-Pair"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.76.0/core/fmt/trait.Debug.html"title="trait core::fmt::Debug">Debug</a> for <aclass="struct"href="struct.Pair.html"title="struct memchr::arch::all::packedpair::Pair">Pair</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.fmt"class="method trait-impl"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#134">source</a><ahref="#method.fmt"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.76.0/core/fmt/trait.Debug.html#tymethod.fmt"class="fn">fmt</a>(&self, f: &mut <aclass="struct"href="https://doc.rust-lang.org/1.76.0/core/fmt/struct.Formatter.html"title="struct core::fmt::Formatter">Formatter</a><'_>) -><aclass="type"href="https://doc.rust-lang.org/1.76.0/core/fmt/type.Result.html"title="type core::fmt::Result">Result</a></h4></section></summary><divclass='docblock'>Formats the value using the given formatter. <ahref="https://doc.rust-lang.org/1.76.0/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></div></details></div></details><sectionid="impl-Copy-for-Pair"class="impl"><aclass="src rightside"href="../../../../src/memchr/arch/all/packedpair/mod.rs.html#134">source</a><ahref="#impl-Copy-for-Pair"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.76.0/core/marker/trait.C
<p>That is, this conversion is whatever the implementation of
<code><ahref="https://doc.rust-lang.org/1.76.0/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/1.76.0/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/1.76.0/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/1.76.0/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/1.76.0/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/1.76.0/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/1.76.0/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/1.76.0/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/1.76.0/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/1.76.0/alloc/borrow/trait.ToOwned.html#method.clone_into"class="fn">clone_into</a>(&self, target: <aclass="primitive"href="https://doc.rust-lang.org/1.76.0/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/1.76.0/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/1.76.0/src/core/convert/mod.rs.html#803-805">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/1.76.0/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/1.76.0/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"class="associatedtype trait-impl"><ahref="#associatedtype.Error"class="anchor">§</a><h4class="code-header">type <ahref="https://doc.rust-lang.org/1.76.0/core/convert/trait.TryFrom.html#associatedtype.Error"class="associatedtype">Error</a> = <aclass="enum"href="https://doc.rust-lang.org/1.76.0/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/1.76.0/src/core/convert/mod.rs.html#810">source</a><ahref="#method.try_from"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.76.0/core/convert/trait.TryFrom.html#tymethod.try_from"class="fn">try_from</a>(value: U) -><aclass="enum"href="https://doc.rust-lang.org/1.76.0/core/result/enum.Result.html"title="enum core::result::Result">Result</a><T, <T as <aclass="trait"href="https://doc.rust-lang.org/1.76.0/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><U>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.76.0/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/1.76.0/src/core/convert/mod.rs.html#788-790">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/1.76.0/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/1.76.0/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-1"class="associatedtype trait-impl"><ahref="#associatedtype.Error-1"class="anchor">§</a><h4class="code-header">type <ahref="https://doc.rust-lang.org/1.76.0/core/convert/trait.TryInto.html#associatedtype.Error"class="associatedtype">Error</a> = <U as <aclass="trait"href="https://doc.rust-lang.org/1.76.0/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.76.0/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/1.76.0/src/core/convert/mod.rs.html#795">source</a><ahref="#method.try_into"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.76.0/core/convert/trait.TryInto.html#tymethod.try_into"class="fn">try_into</a>(self) -><aclass="enum"href="https://doc.rust-lang.org/1.76.0/core/result/enum.Result.html"title="enum core::result::Result">Result</a><U, <U as <aclass="trait"href="https://doc.rust-lang.org/1.76.0/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.76.0/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>
