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<!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 = "Per-object thread-local storage" > < title > thread_local - 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 > < link rel = "stylesheet" href = "../static.files/normalize-76eba96aa4d2e634.css" > < link rel = "stylesheet" href = "../static.files/rustdoc-dd39b87e5fcfba68.css" > < meta name = "rustdoc-vars" data-root-path = "../" data-static-root-path = "../static.files/" data-current-crate = "thread_local" 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" > < script src = "../static.files/storage-118b08c4c78b968e.js" > < / script > < script defer src = "../crates.js" > < / script > < script defer src = "../static.files/main-20a3ad099b048cf2.js" > < / script > < noscript > < link rel = "stylesheet" href = "../static.files/noscript-df360f571f6edeae.css" > < / noscript > < link rel = "alternate icon" type = "image/png" href = "../static.files/favicon-32x32-422f7d1d52889060.png" > < link rel = "icon" type = "image/svg+xml" href = "../static.files/favicon-2c020d218678b618.svg" > < / head > < body class = "rustdoc mod crate" > <!-- [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" title = "show sidebar" > < / button > < / nav > < nav class = "sidebar" > < div class = "sidebar-crate" > < h2 > < a href = "../thread_local/index.html" > thread_local< / a > < span class = "version" > 1.1.8< / span > < / h2 > < / div > < div class = "sidebar-elems" > < ul class = "block" > < li > < a id = "all-types" href = "all.html" > All Items< / a > < / li > < / ul > < section > < ul class = "block" > < li > < a href = "#structs" > Structs< / a > < / li > < / ul > < / section > < / div > < / nav > < div class = "sidebar-resizer" > < / div > < main > < div class = "width-limiter" > < rustdoc-search > < / rustdoc-search > < section id = "main-content" class = "content" > < div class = "main-heading" > < h1 > Crate < a class = "mod" href = "#" > thread_local< / a > < button id = "copy-path" title = "Copy item path to clipboard" > Copy item path< / button > < / h1 > < span class = "out-of-band" > < a class = "src" href = "../src/thread_local/lib.rs.html#8-683" > source< / a > · < button id = "toggle-all-docs" title = "collapse all docs" > [< span > − < / span > ]< / button > < / span > < / div > < details class = "toggle top-doc" open > < summary class = "hideme" > < span > Expand description< / span > < / summary > < div class = "docblock" > < p > Per-object thread-local storage< / p >
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< p > This library provides the < code > ThreadLocal< / code > type which allows a separate copy of
an object to be used for each thread. This allows for per-object
thread-local storage, unlike the standard library’ < code > thread_local!< / code > macro
which only allows static thread-local storage.< / p >
< p > Per-thread objects are not destroyed when a thread exits. Instead, objects
are only destroyed when the < code > ThreadLocal< / code > containing them is destroyed.< / p >
< p > You can also iterate over the thread-local values of all thread in a
< code > ThreadLocal< / code > object using the < code > iter_mut< / code > and < code > into_iter< / code > methods. This can
only be done if you have mutable access to the < code > ThreadLocal< / code > object, which
guarantees that you are the only thread currently accessing it.< / p >
< p > Note that since thread IDs are recycled when a thread exits, it is possible
for one thread to retrieve the object of another thread. Since this can only
occur after a thread has exited this does not lead to any race conditions.< / p >
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< h2 id = "examples" > < a class = "doc-anchor" href = "#examples" > §< / a > Examples< / h2 >
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< p > Basic usage of < code > ThreadLocal< / code > :< / p >
< div class = "example-wrap" > < pre class = "rust rust-example-rendered" > < code > < span class = "kw" > use < / span > thread_local::ThreadLocal;
< span class = "kw" > let < / span > tls: ThreadLocal< u32> = ThreadLocal::new();
< span class = "macro" > assert_eq!< / span > (tls.get(), < span class = "prelude-val" > None< / span > );
< span class = "macro" > assert_eq!< / span > (tls.get_or(|| < span class = "number" > 5< / span > ), < span class = "kw-2" > & < / span > < span class = "number" > 5< / span > );
< span class = "macro" > assert_eq!< / span > (tls.get(), < span class = "prelude-val" > Some< / span > (< span class = "kw-2" > & < / span > < span class = "number" > 5< / span > ));< / code > < / pre > < / div >
< p > Combining thread-local values into a single result:< / p >
< div class = "example-wrap" > < pre class = "rust rust-example-rendered" > < code > < span class = "kw" > use < / span > thread_local::ThreadLocal;
< span class = "kw" > use < / span > std::sync::Arc;
< span class = "kw" > use < / span > std::cell::Cell;
< span class = "kw" > use < / span > std::thread;
< span class = "kw" > let < / span > tls = Arc::new(ThreadLocal::new());
< span class = "comment" > // Create a bunch of threads to do stuff
< / span > < span class = "kw" > for _ in < / span > < span class = "number" > 0< / span > ..< span class = "number" > 5 < / span > {
< span class = "kw" > let < / span > tls2 = tls.clone();
thread::spawn(< span class = "kw" > move < / span > || {
< span class = "comment" > // Increment a counter to count some event...
< / span > < span class = "kw" > let < / span > cell = tls2.get_or(|| Cell::new(< span class = "number" > 0< / span > ));
cell.set(cell.get() + < span class = "number" > 1< / span > );
}).join().unwrap();
}
< span class = "comment" > // Once all threads are done, collect the counter values and return the
// sum of all thread-local counter values.
< / span > < span class = "kw" > let < / span > tls = Arc::try_unwrap(tls).unwrap();
< span class = "kw" > let < / span > total = tls.into_iter().fold(< span class = "number" > 0< / span > , |x, y| x + y.get());
< span class = "macro" > assert_eq!< / span > (total, < span class = "number" > 5< / span > );< / code > < / pre > < / div >
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< / div > < / details > < h2 id = "structs" class = "section-header" > Structs< a href = "#structs" class = "anchor" > §< / a > < / h2 > < ul class = "item-table" > < li > < div class = "item-name" > < a class = "struct" href = "struct.CachedIntoIter.html" title = "struct thread_local::CachedIntoIter" > CachedIntoIter< / a > < span class = "stab deprecated" title = "" > Deprecated< / span > < / div > < div class = "desc docblock-short" > An iterator that moves out of a < code > CachedThreadLocal< / code > .< / div > < / li > < li > < div class = "item-name" > < a class = "struct" href = "struct.CachedIterMut.html" title = "struct thread_local::CachedIterMut" > CachedIterMut< / a > < span class = "stab deprecated" title = "" > Deprecated< / span > < / div > < div class = "desc docblock-short" > Mutable iterator over the contents of a < code > CachedThreadLocal< / code > .< / div > < / li > < li > < div class = "item-name" > < a class = "struct" href = "struct.CachedThreadLocal.html" title = "struct thread_local::CachedThreadLocal" > CachedThreadLocal< / a > < span class = "stab deprecated" title = "" > Deprecated< / span > < / div > < div class = "desc docblock-short" > Wrapper around < a href = "struct.ThreadLocal.html" title = "struct thread_local::ThreadLocal" > < code > ThreadLocal< / code > < / a > .< / div > < / li > < li > < div class = "item-name" > < a class = "struct" href = "struct.IntoIter.html" title = "struct thread_local::IntoIter" > IntoIter< / a > < / div > < div class = "desc docblock-short" > An iterator that moves out of a < code > ThreadLocal< / code > .< / div > < / li > < li > < div class = "item-name" > < a class = "struct" href = "struct.Iter.html" title = "struct thread_local::Iter" > Iter< / a > < / div > < div class = "desc docblock-short" > Iterator over the contents of a < code > ThreadLocal< / code > .< / div > < / li > < li > < div class = "item-name" > < a class = "struct" href = "struct.IterMut.html" title = "struct thread_local::IterMut" > IterMut< / a > < / div > < div class = "desc docblock-short" > Mutable iterator over the contents of a < code > ThreadLocal< / code > .< / div > < / li > < li > < div class = "item-name" > < a class = "struct" href = "struct.ThreadLocal.html" title = "struct thread_local::ThreadLocal" > ThreadLocal< / a > < / div > < div class = "desc docblock-short" > Thread-local variable wrapper< / div > < / li > < / ul > < / section > < / div > < / main > < / body > < / html >
