| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="A speedy hash algorithm for use within rustc. The hashmap in liballoc by default uses SipHash which isn’t quite as speedy as we want. In the compiler we’re not really worried about DOS attempts, so we use a fast non-cryptographic hash."><meta name="keywords" content="rust, rustlang, rust-lang, FxHasher"><title>FxHasher in rustc_hash - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../normalize.css"><link rel="stylesheet" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../ayu.css" disabled><link rel="stylesheet" href="../dark.css" disabled><link rel="stylesheet" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script defer src="sidebar-items.js"></script><script defer src="../main.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../favicon.svg"></head><body class="rustdoc struct"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../rustc_hash/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../rustc_hash/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">FxHasher</a></h2><div class="sidebar-elems"><section><h3><a href="#trait-implementations">Trait Implementations</a></h3><ul class="block"><li><a href="#impl-Default-for-FxHasher">Default</a></li><li><a href="#impl-Hasher-for-FxHasher">Hasher</a></li></ul><h3><a href="#synthetic-implementations">Auto Trait Implementations</a></h3><ul class="block"><li><a href="#impl-RefUnwindSafe-for-FxHasher">RefUnwindSafe</a></li><li><a href="#impl-Send-for-FxHasher">Send</a></li><li><a href="#impl-Sync-for-FxHasher">Sync</a></li><li><a href="#impl-Unpin-for-FxHasher">Unpin</a></li><li><a href="#impl-UnwindSafe-for-FxHasher">UnwindSafe</a></li></ul><h3><a href="#blanket-implementations">Blanket Implementations</a></h3><ul class="block"><li><a href="#impl-Any-for-FxHasher">Any</a></li><li><a href="#impl-Borrow%3CT%3E-for-FxHasher">Borrow<T></a></li><li><a href="#impl-BorrowMut%3CT%3E-for-FxHasher">BorrowMut<T></a></li><li><a href="#impl-From%3CT%3E-for-FxHasher">From<T></a></li><li><a href="#impl-Into%3CU%3E-for-FxHasher">Into<U></a></li><li><a href="#impl-TryFrom%3CU%3E-for-FxHasher">TryFrom<U></a></li><li><a href="#impl-TryInto%3CU%3E-for-FxHasher">TryInto<U></a></li></ul></section><h2><a href="index.html">In rustc_hash</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Struct <a href="index.html">rustc_hash</a>::<wbr><a class="struct" href="#">FxHasher</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../clipboard.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="srclink" href="../src/rustc_hash/lib.rs.html#60-62">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="item-decl"><pre class="rust struct"><code>pub struct FxHasher { /* private fields */ }</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A speedy hash algorithm for use within rustc. The hashmap in liballoc |
| by default uses SipHash which isn’t quite as speedy as we want. In the |
| compiler we’re not really worried about DOS attempts, so we use a fast |
| non-cryptographic hash.</p> |
| <p>This is the same as the algorithm used by Firefox – which is a homespun |
| one not based on any widely-known algorithm – though modified to produce |
| 64-bit hash values instead of 32-bit hash values. It consistently |
| out-performs an FNV-based hash within rustc itself – the collision rate is |
| similar or slightly worse than FNV, but the speed of the hash function |
| itself is much higher because it works on up to 8 bytes at a time.</p> |
| </div></details><h2 id="trait-implementations" class="small-section-header">Trait Implementations<a href="#trait-implementations" class="anchor"></a></h2><div id="trait-implementations-list"><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Default-for-FxHasher" class="impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#69-74">source</a><a href="#impl-Default-for-FxHasher" class="anchor"></a><h3 class="code-header">impl Default for <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.default" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#71-73">source</a><a href="#method.default" class="anchor"></a><h4 class="code-header">fn <a class="fnname">default</a>() -> <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h4></section></summary><div class='docblock'>Returns the “default value” for a type. <a>Read more</a></div></details></div></details><details class="rustdoc-toggle implementors-toggle" open><summary><section id="impl-Hasher-for-FxHasher" class="impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#83-148">source</a><a href="#impl-Hasher-for-FxHasher" class="anchor"></a><h3 class="code-header">impl Hasher for <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#85-109">source</a><a href="#method.write" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write</a>(&mut self, bytes: &[u8])</h4></section></summary><div class='docblock'>Writes some data into this <code>Hasher</code>. <a>Read more</a></div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_u8" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#112-114">source</a><a href="#method.write_u8" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_u8</a>(&mut self, i: u8)</h4></section></summary><div class='docblock'>Writes a single <code>u8</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_u16" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#117-119">source</a><a href="#method.write_u16" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_u16</a>(&mut self, i: u16)</h4></section></summary><div class='docblock'>Writes a single <code>u16</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_u32" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#122-124">source</a><a href="#method.write_u32" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_u32</a>(&mut self, i: u32)</h4></section></summary><div class='docblock'>Writes a single <code>u32</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_u64" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#135-137">source</a><a href="#method.write_u64" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_u64</a>(&mut self, i: u64)</h4></section></summary><div class='docblock'>Writes a single <code>u64</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_usize" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#140-142">source</a><a href="#method.write_usize" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_usize</a>(&mut self, i: usize)</h4></section></summary><div class='docblock'>Writes a single <code>usize</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.finish" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/rustc_hash/lib.rs.html#145-147">source</a><a href="#method.finish" class="anchor"></a><h4 class="code-header">fn <a class="fnname">finish</a>(&self) -> u64</h4></section></summary><div class='docblock'>Returns the hash value for the values written so far. <a>Read more</a></div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_u128" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.26.0">1.26.0</span><a href="#method.write_u128" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_u128</a>(&mut self, i: u128)</h4></section></summary><div class='docblock'>Writes a single <code>u128</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_i8" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.3.0">1.3.0</span><a href="#method.write_i8" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_i8</a>(&mut self, i: i8)</h4></section></summary><div class='docblock'>Writes a single <code>i8</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_i16" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.3.0">1.3.0</span><a href="#method.write_i16" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_i16</a>(&mut self, i: i16)</h4></section></summary><div class='docblock'>Writes a single <code>i16</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_i32" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.3.0">1.3.0</span><a href="#method.write_i32" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_i32</a>(&mut self, i: i32)</h4></section></summary><div class='docblock'>Writes a single <code>i32</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_i64" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.3.0">1.3.0</span><a href="#method.write_i64" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_i64</a>(&mut self, i: i64)</h4></section></summary><div class='docblock'>Writes a single <code>i64</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_i128" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.26.0">1.26.0</span><a href="#method.write_i128" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_i128</a>(&mut self, i: i128)</h4></section></summary><div class='docblock'>Writes a single <code>i128</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_isize" class="method trait-impl has-srclink"><span class="since rightside" title="Stable since Rust version 1.3.0">1.3.0</span><a href="#method.write_isize" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_isize</a>(&mut self, i: isize)</h4></section></summary><div class='docblock'>Writes a single <code>isize</code> into this hasher.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_length_prefix" class="method trait-impl has-srclink"><a href="#method.write_length_prefix" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_length_prefix</a>(&mut self, len: usize)</h4></section></summary><span class="item-info"><div class="stab unstable"><span class="emoji">🔬</span><span>This is a nightly-only experimental API. (<code>hasher_prefixfree_extras</code>)</span></div></span><div class='docblock'>Writes a length prefix into this hasher, as part of being prefix-free. <a>Read more</a></div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.write_str" class="method trait-impl has-srclink"><a href="#method.write_str" class="anchor"></a><h4 class="code-header">fn <a class="fnname">write_str</a>(&mut self, s: &str)</h4></section></summary><span class="item-info"><div class="stab unstable"><span class="emoji">🔬</span><span>This is a nightly-only experimental API. (<code>hasher_prefixfree_extras</code>)</span></div></span><div class='docblock'>Writes a single <code>str</code> into this hasher. <a>Read more</a></div></details></div></details></div><h2 id="synthetic-implementations" class="small-section-header">Auto Trait Implementations<a href="#synthetic-implementations" class="anchor"></a></h2><div id="synthetic-implementations-list"><section id="impl-RefUnwindSafe-for-FxHasher" class="impl has-srclink"><a href="#impl-RefUnwindSafe-for-FxHasher" class="anchor"></a><h3 class="code-header">impl RefUnwindSafe for <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h3></section><section id="impl-Send-for-FxHasher" class="impl has-srclink"><a href="#impl-Send-for-FxHasher" class="anchor"></a><h3 class="code-header">impl Send for <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h3></section><section id="impl-Sync-for-FxHasher" class="impl has-srclink"><a href="#impl-Sync-for-FxHasher" class="anchor"></a><h3 class="code-header">impl Sync for <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h3></section><section id="impl-Unpin-for-FxHasher" class="impl has-srclink"><a href="#impl-Unpin-for-FxHasher" class="anchor"></a><h3 class="code-header">impl Unpin for <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h3></section><section id="impl-UnwindSafe-for-FxHasher" class="impl has-srclink"><a href="#impl-UnwindSafe-for-FxHasher" class="anchor"></a><h3 class="code-header">impl UnwindSafe for <a class="struct" href="struct.FxHasher.html" title="struct rustc_hash::FxHasher">FxHasher</a></h3></section></div><h2 id="blanket-implementations" class="small-section-header">Blanket Implementations<a href="#blanket-implementations" class="anchor"></a></h2><div id="blanket-implementations-list"><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Any-for-FxHasher" class="impl has-srclink"><a href="#impl-Any-for-FxHasher" class="anchor"></a><h3 class="code-header">impl<T> Any for T<span class="where fmt-newline">where<br> T: 'static + ?Sized,</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.type_id" class="method trait-impl has-srclink"><a href="#method.type_id" class="anchor"></a><h4 class="code-header">fn <a class="fnname">type_id</a>(&self) -> TypeId</h4></section></summary><div class='docblock'>Gets the <code>TypeId</code> of <code>self</code>. <a>Read more</a></div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Borrow%3CT%3E-for-FxHasher" class="impl has-srclink"><a href="#impl-Borrow%3CT%3E-for-FxHasher" class="anchor"></a><h3 class="code-header">impl<T> Borrow<T> for T<span class="where fmt-newline">where<br> T: ?Sized,</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.borrow" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span><a href="#method.borrow" class="anchor"></a><h4 class="code-header">fn <a class="fnname">borrow</a>(&self) -> &T</h4></section></summary><div class='docblock'>Immutably borrows from an owned value. <a>Read more</a></div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-BorrowMut%3CT%3E-for-FxHasher" class="impl has-srclink"><a href="#impl-BorrowMut%3CT%3E-for-FxHasher" class="anchor"></a><h3 class="code-header">impl<T> BorrowMut<T> for T<span class="where fmt-newline">where<br> T: ?Sized,</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.borrow_mut" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/91522" title="Tracking issue for const_borrow">unstable</a></span><a href="#method.borrow_mut" class="anchor"></a><h4 class="code-header">fn <a class="fnname">borrow_mut</a>(&mut self) -> &mut T</h4></section></summary><div class='docblock'>Mutably borrows from an owned value. <a>Read more</a></div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-From%3CT%3E-for-FxHasher" class="impl has-srclink"><a href="#impl-From%3CT%3E-for-FxHasher" class="anchor"></a><h3 class="code-header">impl<T> From<T> for T</h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.from" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.from" class="anchor"></a><h4 class="code-header">fn <a class="fnname">from</a>(t: T) -> T</h4></section></summary><div class="docblock"><p>Returns the argument unchanged.</p> |
| </div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-Into%3CU%3E-for-FxHasher" class="impl has-srclink"><a href="#impl-Into%3CU%3E-for-FxHasher" class="anchor"></a><h3 class="code-header">impl<T, U> Into<U> for T<span class="where fmt-newline">where<br> U: From<T>,</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.into" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.into" class="anchor"></a><h4 class="code-header">fn <a class="fnname">into</a>(self) -> U</h4></section></summary><div class="docblock"><p>Calls <code>U::from(self)</code>.</p> |
| <p>That is, this conversion is whatever the implementation of |
| <code>[From]<T> for U</code> chooses to do.</p> |
| </div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-TryFrom%3CU%3E-for-FxHasher" class="impl has-srclink"><a href="#impl-TryFrom%3CU%3E-for-FxHasher" class="anchor"></a><h3 class="code-header">impl<T, U> TryFrom<U> for T<span class="where fmt-newline">where<br> U: Into<T>,</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle" open><summary><section id="associatedtype.Error-1" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Error-1" class="anchor"></a><h4 class="code-header">type <a class="associatedtype">Error</a> = Infallible</h4></section></summary><div class='docblock'>The type returned in the event of a conversion error.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_from" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.try_from" class="anchor"></a><h4 class="code-header">fn <a class="fnname">try_from</a>(value: U) -> Result<T, <T as TryFrom<U>>::Error></h4></section></summary><div class='docblock'>Performs the conversion.</div></details></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-TryInto%3CU%3E-for-FxHasher" class="impl has-srclink"><a href="#impl-TryInto%3CU%3E-for-FxHasher" class="anchor"></a><h3 class="code-header">impl<T, U> TryInto<U> for T<span class="where fmt-newline">where<br> U: TryFrom<T>,</span></h3></section></summary><div class="impl-items"><details class="rustdoc-toggle" open><summary><section id="associatedtype.Error" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Error" class="anchor"></a><h4 class="code-header">type <a class="associatedtype">Error</a> = <U as TryFrom<T>>::Error</h4></section></summary><div class='docblock'>The type returned in the event of a conversion error.</div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.try_into" class="method trait-impl has-srclink"><span class="since rightside" title="const unstable">const: <a href="https://github.com/rust-lang/rust/issues/88674" title="Tracking issue for const_convert">unstable</a></span><a href="#method.try_into" class="anchor"></a><h4 class="code-header">fn <a class="fnname">try_into</a>(self) -> Result<U, <U as TryFrom<T>>::Error></h4></section></summary><div class='docblock'>Performs the conversion.</div></details></div></details></div></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="rustc_hash" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
