<!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="An implementation of the Fowler–Noll–Vo hash function."><title>fnv - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-46f98efaafac5295.ttf.woff2,FiraSans-Regular-018c141bf0843ffd.woff2,FiraSans-Medium-8f9a781e4970d388.woff2,SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2,SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/${f}">`).join(""))</script><linkrel="stylesheet"href="../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../static.files/rustdoc-dd39b87e5fcfba68.css"><metaname="rustdoc-vars"data-root-path="../"data-static-root-path="../static.files/"data-current-crate="fnv"data-themes=""data-resource-suffix=""data-rustdoc-version="1.80.0 (051478957 2024-07-21)"data-channel="1.80.0"data-search-js="search-d52510db62a78183.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../static.files/storage-118b08c4c78b968e.js"></script><scriptdefersrc="../crates.js"></script><scriptdefersrc="../static.files/main-20a3ad099b048cf2.js"></script><noscript><linkrel="stylesheet"href="../static.files/noscript-df360f571f6edeae.css"></noscript><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 crate"><!--[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="../fnv/index.html">fnv</a><spanclass="version">1.0.7</span></h2></div><divclass="sidebar-elems"><ulclass="block"><li><aid="all-types"href="all.html">All Items</a></li></ul><section><ulclass="block"><li><ahref="#structs">Structs</a></li><li><ahref="#types">Type Aliases</a></li></ul></section></div></nav><divclass="sidebar-resizer"></div><main><divclass="width-limiter"><rustdoc-search></rustdoc-search><sectionid="main-content"class="content"><divclass="main-heading"><h1>Crate <aclass="mod"href="#">fnv</a><buttonid="copy-path"title="Copy item path to clipboard">Copy item path</button></h1><spanclass="out-of-band"><aclass="src"href="../src/fnv/lib.rs.html#1-367">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>An implementation of the <ahref="http://www.isthe.com/chongo/tech/comp/fnv/index.html">Fowler–Noll–Vo hash function</a>.</p>
<p>The FNV hash function is a custom <code>Hasher</code> implementation that is more
efficient for smaller hash keys.</p>
<p><ahref="https://www.rust-lang.org/en-US/faq.html#why-are-rusts-hashmaps-slow">The Rust FAQ states that</a> while the default <code>Hasher</code> implementation,
SipHash, is good in many cases, it is notably slower than other algorithms
with short keys, such as when you have a map of integers to other values.
In cases like these, <ahref="https://cglab.ca/~abeinges/blah/hash-rs/">FNV is demonstrably faster</a>.</p>
<p>Its disadvantages are that it performs badly on larger inputs, and
provides no protection against collision attacks, where a malicious user
can craft specific keys designed to slow a hasher down. Thus, it is
important to profile your program to ensure that you are using small hash
keys, and be certain that your program could not be exposed to malicious
inputs (including being a networked server).</p>
<p>The Rust compiler itself uses FNV, as it is not worried about
denial-of-service attacks, and can assume that its inputs are going to be
</div></details><h2id="structs"class="section-header">Structs<ahref="#structs"class="anchor">§</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="struct"href="struct.FnvHasher.html"title="struct fnv::FnvHasher">FnvHasher</a></div><divclass="desc docblock-short">An implementation of the Fowler–Noll–Vo hash function.</div></li></ul><h2id="types"class="section-header">Type Aliases<ahref="#types"class="anchor">§</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="type"href="type.FnvBuildHasher.html"title="type fnv::FnvBuildHasher">FnvBuildHasher</a></div><divclass="desc docblock-short">A builder for default FNV hashers.</div></li><li><divclass="item-name"><aclass="type"href="type.FnvHashMap.html"title="type fnv::FnvHashMap">FnvHashMap</a></div><divclass="desc docblock-short">A <code>HashMap</code> using a default FNV hasher.</div></li><li><divclass="item-name"><aclass="type"href="type.FnvHashSet.html"title="type fnv::FnvHashSet">FnvHashSet</a></div><divclass="desc docblock-short">A <code>HashSet</code> using a default FNV hasher.</div></li></ul></section></div></main></body></html>
