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| <p class='location'>Crate thread_local</p><div class="block items"><ul><li><a href="#structs">Structs</a></li><li><a href="#types">Type Definitions</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'thread_local', ty: 'mod', relpath: '../'};</script> |
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| <h1 class='fqn'><span class='in-band'>Crate <a class="mod" href=''>thread_local</a></span><span class='out-of-band'><span id='render-detail'> |
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| </span><a class='srclink' href='../src/thread_local/lib.rs.html#8-773' title='goto source code'>[src]</a></span></h1> |
| <div class='docblock'><p>Per-object thread-local storage</p> |
| |
| <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's <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>A <code>CachedThreadLocal</code> type is also provided which wraps a <code>ThreadLocal</code> but |
| also uses a special fast path for the first thread that writes into it. The |
| fast path has very low overhead (<1ns per access) while keeping the same |
| performance as <code>ThreadLocal</code> for other threads.</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> |
| |
| <h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1> |
| <p>Basic usage of <code>ThreadLocal</code>:</p> |
| |
| <pre class="rust rust-example-rendered"> |
| <span class="kw">use</span> <span class="ident">thread_local</span>::<span class="ident">ThreadLocal</span>; |
| <span class="kw">let</span> <span class="ident">tls</span>: <span class="ident">ThreadLocal</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">ThreadLocal</span>::<span class="ident">new</span>(); |
| <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">tls</span>.<span class="ident">get</span>(), <span class="prelude-val">None</span>); |
| <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">tls</span>.<span class="ident">get_or</span>(<span class="op">||</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="number">5</span>)), <span class="kw-2">&</span><span class="number">5</span>); |
| <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">tls</span>.<span class="ident">get</span>(), <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="number">5</span>));</pre> |
| |
| <p>Combining thread-local values into a single result:</p> |
| |
| <pre class="rust rust-example-rendered"> |
| <span class="kw">use</span> <span class="ident">thread_local</span>::<span class="ident">ThreadLocal</span>; |
| <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Arc</span>; |
| <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">cell</span>::<span class="ident">Cell</span>; |
| <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>; |
| |
| <span class="kw">let</span> <span class="ident">tls</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">ThreadLocal</span>::<span class="ident">new</span>()); |
| |
| <span class="comment">// Create a bunch of threads to do stuff</span> |
| <span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..<span class="number">5</span> { |
| <span class="kw">let</span> <span class="ident">tls2</span> <span class="op">=</span> <span class="ident">tls</span>.<span class="ident">clone</span>(); |
| <span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> { |
| <span class="comment">// Increment a counter to count some event...</span> |
| <span class="kw">let</span> <span class="ident">cell</span> <span class="op">=</span> <span class="ident">tls2</span>.<span class="ident">get_or</span>(<span class="op">||</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">Cell</span>::<span class="ident">new</span>(<span class="number">0</span>))); |
| <span class="ident">cell</span>.<span class="ident">set</span>(<span class="ident">cell</span>.<span class="ident">get</span>() <span class="op">+</span> <span class="number">1</span>); |
| }).<span class="ident">join</span>().<span class="ident">unwrap</span>(); |
| } |
| |
| <span class="comment">// Once all threads are done, collect the counter values and return the</span> |
| <span class="comment">// sum of all thread-local counter values.</span> |
| <span class="kw">let</span> <span class="ident">tls</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">try_unwrap</span>(<span class="ident">tls</span>).<span class="ident">unwrap</span>(); |
| <span class="kw">let</span> <span class="ident">total</span> <span class="op">=</span> <span class="ident">tls</span>.<span class="ident">into_iter</span>().<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">x</span>, <span class="ident">y</span><span class="op">|</span> <span class="ident">x</span> <span class="op">+</span> <span class="ident">y</span>.<span class="ident">get</span>()); |
| <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">total</span>, <span class="number">5</span>);</pre> |
| </div><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2> |
| <table> |
| <tr class=' module-item'> |
| <td><a class="struct" href="struct.CachedThreadLocal.html" |
| title='struct thread_local::CachedThreadLocal'>CachedThreadLocal</a></td> |
| <td class='docblock-short'> |
| <p>Wrapper around <code>ThreadLocal</code> which adds a fast path for a single thread.</p> |
| </td> |
| </tr> |
| <tr class=' module-item'> |
| <td><a class="struct" href="struct.IntoIter.html" |
| title='struct thread_local::IntoIter'>IntoIter</a></td> |
| <td class='docblock-short'> |
| <p>An iterator that moves out of a <code>ThreadLocal</code>.</p> |
| </td> |
| </tr> |
| <tr class=' module-item'> |
| <td><a class="struct" href="struct.IterMut.html" |
| title='struct thread_local::IterMut'>IterMut</a></td> |
| <td class='docblock-short'> |
| <p>Mutable iterator over the contents of a <code>ThreadLocal</code>.</p> |
| </td> |
| </tr> |
| <tr class=' module-item'> |
| <td><a class="struct" href="struct.ThreadLocal.html" |
| title='struct thread_local::ThreadLocal'>ThreadLocal</a></td> |
| <td class='docblock-short'> |
| <p>Thread-local variable wrapper</p> |
| </td> |
| </tr></table><h2 id='types' class='section-header'><a href="#types">Type Definitions</a></h2> |
| <table> |
| <tr class=' module-item'> |
| <td><a class="type" href="type.CachedIntoIter.html" |
| title='type thread_local::CachedIntoIter'>CachedIntoIter</a></td> |
| <td class='docblock-short'> |
| <p>An iterator that moves out of a <code>CachedThreadLocal</code>.</p> |
| </td> |
| </tr> |
| <tr class=' module-item'> |
| <td><a class="type" href="type.CachedIterMut.html" |
| title='type thread_local::CachedIterMut'>CachedIterMut</a></td> |
| <td class='docblock-short'> |
| <p>Mutable iterator over the contents of a <code>CachedThreadLocal</code>.</p> |
| </td> |
| </tr></table></section> |
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