| <!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 trait describing smart reference counted pointers."><meta name="keywords" content="rust, rustlang, rust-lang, RefCnt"><title>RefCnt in arc_swap - 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 trait"><!--[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="../arc_swap/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="../arc_swap/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">RefCnt</a></h2><div class="sidebar-elems"><section><h3><a href="#required-associated-types">Required Associated Types</a></h3><ul class="block"><li><a href="#associatedtype.Base">Base</a></li></ul><h3><a href="#required-methods">Required Methods</a></h3><ul class="block"><li><a href="#tymethod.as_ptr">as_ptr</a></li><li><a href="#tymethod.from_ptr">from_ptr</a></li><li><a href="#tymethod.into_ptr">into_ptr</a></li></ul><h3><a href="#provided-methods">Provided Methods</a></h3><ul class="block"><li><a href="#method.dec">dec</a></li><li><a href="#method.inc">inc</a></li></ul><h3><a href="#foreign-impls">Implementations on Foreign Types</a></h3><ul class="block"><li><a href="#impl-RefCnt-for-Arc%3CT%3E">Arc<T></a></li><li><a href="#impl-RefCnt-for-Option%3CT%3E">Option<T></a></li><li><a href="#impl-RefCnt-for-Rc%3CT%3E">Rc<T></a></li></ul><h3><a href="#implementors">Implementors</a></h3></section><h2><a href="index.html">In arc_swap</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">Trait <a href="index.html">arc_swap</a>::<wbr><a class="trait" href="#">RefCnt</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/arc_swap/ref_cnt.rs.html#38-88">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 trait"><code>pub unsafe trait RefCnt: Clone { |
| type <a href="#associatedtype.Base" class="associatedtype">Base</a>; |
| |
| fn <a href="#tymethod.into_ptr" class="fnname">into_ptr</a>(me: Self) -> *mut Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a>; |
| <span class="item-spacer"></span> fn <a href="#tymethod.as_ptr" class="fnname">as_ptr</a>(me: &Self) -> *mut Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a>; |
| <span class="item-spacer"></span> unsafe fn <a href="#tymethod.from_ptr" class="fnname">from_ptr</a>(ptr: *const Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a>) -> Self; |
| |
| fn <a href="#method.inc" class="fnname">inc</a>(me: &Self) -> *mut Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a> { ... } |
| <span class="item-spacer"></span> unsafe fn <a href="#method.dec" class="fnname">dec</a>(ptr: *const Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a>) { ... } |
| }</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A trait describing smart reference counted pointers.</p> |
| <p>Note that in a way [<code>Option<Arc<T>></code>][Option] is also a smart reference counted pointer, just |
| one that can hold NULL.</p> |
| <p>The trait is unsafe, because a wrong implementation will break the <a href="struct.ArcSwapAny.html">ArcSwapAny</a> |
| implementation and lead to UB.</p> |
| <p>This is not actually expected for downstream crate to implement, this is just means to reuse |
| code for <a href="std::sync::Arc">Arc</a> and [<code>Option<Arc></code>][Option] variants. However, it is theoretically possible (if |
| you have your own <a href="std::sync::Arc">Arc</a> implementation).</p> |
| <p>It is also implemented for <a href="std::rc::Rc">Rc</a>, but that is not considered very useful (because the |
| <a href="struct.ArcSwapAny.html">ArcSwapAny</a> is not <code>Send</code> or <code>Sync</code>, therefore there’s very little advantage for it to be |
| atomic).</p> |
| <h2 id="safety"><a href="#safety">Safety</a></h2> |
| <p>Aside from the obvious properties (like that incrementing and decrementing a reference count |
| cancel each out and that having less references tracked than how many things actually point to |
| the value is fine as long as the count doesn’t drop to 0), it also must satisfy that if two |
| pointers have the same value, they point to the same object. This is specifically not true for |
| ZSTs, but it is true for <code>Arc</code>s of ZSTs, because they have the reference counts just after the |
| value. It would be fine to point to a type-erased version of the same object, though (if one |
| could use this trait with unsized types in the first place).</p> |
| <p>Furthermore, the type should be Pin (eg. if the type is cloned or moved, it should still |
| point/deref to the same place in memory).</p> |
| </div></details><h2 id="required-associated-types" class="small-section-header">Required Associated Types<a href="#required-associated-types" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle method-toggle" open><summary><section id="associatedtype.Base" class="method has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#40">source</a><h4 class="code-header">type <a href="#associatedtype.Base" class="associatedtype">Base</a></h4></section></summary><div class="docblock"><p>The base type the pointer points to.</p> |
| </div></details></div><h2 id="required-methods" class="small-section-header">Required Methods<a href="#required-methods" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle method-toggle" open><summary><section id="tymethod.into_ptr" class="method has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#49">source</a><h4 class="code-header">fn <a href="#tymethod.into_ptr" class="fnname">into_ptr</a>(me: Self) -> *mut Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a></h4></section></summary><div class="docblock"><p>Converts the smart pointer into a raw pointer, without affecting the reference count.</p> |
| <p>This can be seen as kind of freezing the pointer ‒ it’ll be later converted back using |
| <a href="#method.from_ptr"><code>from_ptr</code></a>.</p> |
| <p>The pointer must point to the value stored (and the value must be the same as one returned |
| by <a href="#method.as_ptr"><code>as_ptr</code></a>.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="tymethod.as_ptr" class="method has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#54">source</a><h4 class="code-header">fn <a href="#tymethod.as_ptr" class="fnname">as_ptr</a>(me: &Self) -> *mut Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a></h4></section></summary><div class="docblock"><p>Provides a view into the smart pointer as a raw pointer.</p> |
| <p>This must not affect the reference count ‒ the pointer is only borrowed.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="tymethod.from_ptr" class="method has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#67">source</a><h4 class="code-header">unsafe fn <a href="#tymethod.from_ptr" class="fnname">from_ptr</a>(ptr: *const Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a>) -> Self</h4></section></summary><div class="docblock"><p>Converts a raw pointer back into the smart pointer, without affecting the reference count.</p> |
| <p>This is only called on values previously returned by <a href="#method.into_ptr"><code>into_ptr</code></a>. |
| However, it is not guaranteed to be 1:1 relation ‒ <code>from_ptr</code> may be called more times than |
| <code>into_ptr</code> temporarily provided the reference count never drops under 1 during that time |
| (the implementation sometimes owes a reference). These extra pointers will either be |
| converted back using <code>into_ptr</code> or forgotten.</p> |
| <h5 id="safety-1"><a href="#safety-1">Safety</a></h5> |
| <p>This must not be called by code outside of this crate.</p> |
| </div></details></div><h2 id="provided-methods" class="small-section-header">Provided Methods<a href="#provided-methods" class="anchor"></a></h2><div class="methods"><details class="rustdoc-toggle method-toggle" open><summary><section id="method.inc" class="method has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#72-74">source</a><h4 class="code-header">fn <a href="#method.inc" class="fnname">inc</a>(me: &Self) -> *mut Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a></h4></section></summary><div class="docblock"><p>Increments the reference count by one.</p> |
| <p>Return the pointer to the inner thing as a side effect.</p> |
| </div></details><details class="rustdoc-toggle method-toggle" open><summary><section id="method.dec" class="method has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#85-87">source</a><h4 class="code-header">unsafe fn <a href="#method.dec" class="fnname">dec</a>(ptr: *const Self::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a>)</h4></section></summary><div class="docblock"><p>Decrements the reference count by one.</p> |
| <p>Note this is called on a raw pointer (one previously returned by |
| <a href="#method.into_ptr"><code>into_ptr</code></a>. This may lead to dropping of the reference count to 0 and |
| destruction of the internal pointer.</p> |
| <h5 id="safety-2"><a href="#safety-2">Safety</a></h5> |
| <p>This must not be called by code outside of this crate.</p> |
| </div></details></div><h2 id="foreign-impls" class="small-section-header">Implementations on Foreign Types<a href="#foreign-impls" class="anchor"></a></h2><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-RefCnt-for-Arc%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#90-123">source</a><a href="#impl-RefCnt-for-Arc%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> <a class="trait" href="trait.RefCnt.html" title="trait arc_swap::RefCnt">RefCnt</a> for Arc<T></h3></section></summary><div class="impl-items"><section id="associatedtype.Base-1" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Base-1" class="anchor"></a><h4 class="code-header">type <a href="#associatedtype.Base" class="associatedtype">Base</a> = T</h4></section><section id="method.into_ptr" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#92-94">source</a><a href="#method.into_ptr" class="anchor"></a><h4 class="code-header">fn <a href="#tymethod.into_ptr" class="fnname">into_ptr</a>(me: Arc<T>) -> *mut T</h4></section><section id="method.as_ptr" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#95-119">source</a><a href="#method.as_ptr" class="anchor"></a><h4 class="code-header">fn <a href="#tymethod.as_ptr" class="fnname">as_ptr</a>(me: &Arc<T>) -> *mut T</h4></section><section id="method.from_ptr" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#120-122">source</a><a href="#method.from_ptr" class="anchor"></a><h4 class="code-header">unsafe fn <a href="#tymethod.from_ptr" class="fnname">from_ptr</a>(ptr: *const T) -> Arc<T></h4></section></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-RefCnt-for-Rc%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#125-158">source</a><a href="#impl-RefCnt-for-Rc%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T> <a class="trait" href="trait.RefCnt.html" title="trait arc_swap::RefCnt">RefCnt</a> for Rc<T></h3></section></summary><div class="impl-items"><section id="associatedtype.Base-2" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Base-2" class="anchor"></a><h4 class="code-header">type <a href="#associatedtype.Base" class="associatedtype">Base</a> = T</h4></section><section id="method.into_ptr-1" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#127-129">source</a><a href="#method.into_ptr-1" class="anchor"></a><h4 class="code-header">fn <a href="#tymethod.into_ptr" class="fnname">into_ptr</a>(me: Rc<T>) -> *mut T</h4></section><section id="method.as_ptr-1" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#130-154">source</a><a href="#method.as_ptr-1" class="anchor"></a><h4 class="code-header">fn <a href="#tymethod.as_ptr" class="fnname">as_ptr</a>(me: &Rc<T>) -> *mut T</h4></section><section id="method.from_ptr-1" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#155-157">source</a><a href="#method.from_ptr-1" class="anchor"></a><h4 class="code-header">unsafe fn <a href="#tymethod.from_ptr" class="fnname">from_ptr</a>(ptr: *const T) -> Rc<T></h4></section></div></details><details class="rustdoc-toggle implementors-toggle"><summary><section id="impl-RefCnt-for-Option%3CT%3E" class="impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#160-175">source</a><a href="#impl-RefCnt-for-Option%3CT%3E" class="anchor"></a><h3 class="code-header">impl<T: <a class="trait" href="trait.RefCnt.html" title="trait arc_swap::RefCnt">RefCnt</a>> <a class="trait" href="trait.RefCnt.html" title="trait arc_swap::RefCnt">RefCnt</a> for Option<T></h3></section></summary><div class="impl-items"><section id="associatedtype.Base-3" class="associatedtype trait-impl has-srclink"><a href="#associatedtype.Base-3" class="anchor"></a><h4 class="code-header">type <a href="#associatedtype.Base" class="associatedtype">Base</a> = <T as <a class="trait" href="trait.RefCnt.html" title="trait arc_swap::RefCnt">RefCnt</a>>::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a></h4></section><section id="method.into_ptr-2" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#162-164">source</a><a href="#method.into_ptr-2" class="anchor"></a><h4 class="code-header">fn <a href="#tymethod.into_ptr" class="fnname">into_ptr</a>(me: Option<T>) -> *mut T::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a></h4></section><section id="method.as_ptr-2" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#165-167">source</a><a href="#method.as_ptr-2" class="anchor"></a><h4 class="code-header">fn <a href="#tymethod.as_ptr" class="fnname">as_ptr</a>(me: &Option<T>) -> *mut T::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a></h4></section><section id="method.from_ptr-2" class="method trait-impl has-srclink"><a class="srclink rightside" href="../src/arc_swap/ref_cnt.rs.html#168-174">source</a><a href="#method.from_ptr-2" class="anchor"></a><h4 class="code-header">unsafe fn <a href="#tymethod.from_ptr" class="fnname">from_ptr</a>(ptr: *const T::<a class="associatedtype" href="trait.RefCnt.html#associatedtype.Base" title="type arc_swap::RefCnt::Base">Base</a>) -> Option<T></h4></section></div></details><h2 id="implementors" class="small-section-header">Implementors<a href="#implementors" class="anchor"></a></h2><div id="implementors-list"></div><script src="../implementors/arc_swap/ref_cnt/trait.RefCnt.js" data-ignore-extern-crates="alloc,core" async></script></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="arc_swap" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
