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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="API documentation for the Rust `Condvar` struct in crate `parking_lot`."><meta name="keywords" content="rust, rustlang, rust-lang, Condvar"><title>parking_lot::Condvar - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script></head><body class="rustdoc struct"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><p class='location'>Struct Condvar</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.new">new</a><a href="#method.notify_one">notify_one</a><a href="#method.notify_all">notify_all</a><a href="#method.wait">wait</a><a href="#method.wait_until">wait_until</a><a href="#method.wait_for">wait_for</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Default">Default</a><a href="#impl-Debug">Debug</a></div><a class="sidebar-title" href="#synthetic-implementations">Auto Trait Implementations</a><div class="sidebar-links"><a href="#impl-Send">Send</a><a href="#impl-Sync">Sync</a></div></div><p class='location'><a href='index.html'>parking_lot</a></p><script>window.sidebarCurrent = {name: 'Condvar', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Struct <a href='index.html'>parking_lot</a>::<wbr><a class="struct" href=''>Condvar</a></span><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../src/parking_lot/condvar.rs.html#83-85' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust struct'>pub struct Condvar { /* fields omitted */ }</pre></div><div class='docblock'><p>A Condition Variable</p>
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<p>Condition variables represent the ability to block a thread such that it
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consumes no CPU time while waiting for an event to occur. Condition
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variables are typically associated with a boolean predicate (a condition)
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and a mutex. The predicate is always verified inside of the mutex before
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determining that thread must block.</p>
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<p>Note that this module places one additional restriction over the system
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condition variables: each condvar can be used with only one mutex at a
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time. Any attempt to use multiple mutexes on the same condition variable
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simultaneously will result in a runtime panic. However it is possible to
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switch to a different mutex if there are no threads currently waiting on
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the condition variable.</p>
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<h1 id="differences-from-the-standard-library-condvar" class="section-header"><a href="#differences-from-the-standard-library-condvar">Differences from the standard library <code>Condvar</code></a></h1>
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<ul>
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<li>No spurious wakeups: A wait will only return a non-timeout result if it
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was woken up by <code>notify_one</code> or <code>notify_all</code>.</li>
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<li><code>Condvar::notify_all</code> will only wake up a single thread, the rest are
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requeued to wait for the <code>Mutex</code> to be unlocked by the thread that was
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woken up.</li>
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<li>Only requires 1 word of space, whereas the standard library boxes the
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<code>Condvar</code> due to platform limitations.</li>
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<li>Can be statically constructed (requires the <code>const_fn</code> nightly feature).</li>
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<li>Does not require any drop glue when dropped.</li>
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<li>Inline fast path for the uncontended case.</li>
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</ul>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">parking_lot</span>::{<span class="ident">Mutex</span>, <span class="ident">Condvar</span>};
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Arc</span>;
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
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<span class="kw">let</span> <span class="ident">pair</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>((<span class="ident">Mutex</span>::<span class="ident">new</span>(<span class="bool-val">false</span>), <span class="ident">Condvar</span>::<span class="ident">new</span>()));
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<span class="kw">let</span> <span class="ident">pair2</span> <span class="op">=</span> <span class="ident">pair</span>.<span class="ident">clone</span>();
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<span class="comment">// Inside of our lock, spawn a new thread, and then wait for it to start</span>
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<span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span><span class="op">||</span> {
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<span class="kw">let</span> <span class="kw-2">&</span>(<span class="kw-2">ref</span> <span class="ident">lock</span>, <span class="kw-2">ref</span> <span class="ident">cvar</span>) <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">pair2</span>;
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">started</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">lock</span>();
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<span class="kw-2">*</span><span class="ident">started</span> <span class="op">=</span> <span class="bool-val">true</span>;
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<span class="ident">cvar</span>.<span class="ident">notify_one</span>();
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});
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<span class="comment">// wait for the thread to start up</span>
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<span class="kw">let</span> <span class="kw-2">&</span>(<span class="kw-2">ref</span> <span class="ident">lock</span>, <span class="kw-2">ref</span> <span class="ident">cvar</span>) <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">pair</span>;
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">started</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">lock</span>();
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<span class="kw">while</span> <span class="op">!</span><span class="kw-2">*</span><span class="ident">started</span> {
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<span class="ident">cvar</span>.<span class="ident">wait</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">started</span>);
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}</pre>
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</div><h2 id='methods' class='small-section-header'>Methods<a href='#methods' class='anchor'></a></h2><h3 id='impl' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="struct" href="../parking_lot/struct.Condvar.html" title="struct parking_lot::Condvar">Condvar</a></code><a href='#impl' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#87-356' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.new' class="method"><span id='new.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.new' class='fnname'>new</a>() -> <a class="struct" href="../parking_lot/struct.Condvar.html" title="struct parking_lot::Condvar">Condvar</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#102-106' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates a new condition variable which is ready to be waited on and
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notified.</p>
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</div><h4 id='method.notify_one' class="method"><span id='notify_one.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.notify_one' class='fnname'>notify_one</a>(&self)</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#116-123' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Wakes up one blocked thread on this condvar.</p>
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<p>If there is a blocked thread on this condition variable, then it will
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be woken up from its call to <code>wait</code> or <code>wait_timeout</code>. Calls to
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<code>notify_one</code> are not buffered in any way.</p>
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<p>To wake up all threads, see <code>notify_all()</code>.</p>
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</div><h4 id='method.notify_all' class="method"><span id='notify_all.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.notify_all' class='fnname'>notify_all</a>(&self)</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#150-158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Wakes up all blocked threads on this condvar.</p>
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<p>This method will ensure that any current waiters on the condition
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variable are awoken. Calls to <code>notify_all()</code> are not buffered in any
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way.</p>
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<p>To wake up only one thread, see <code>notify_one()</code>.</p>
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</div><h4 id='method.wait' class="method"><span id='wait.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.wait' class='fnname'>wait</a><T: ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>>(&self, mutex_guard: &mut <a class="type" href="../parking_lot/type.MutexGuard.html" title="type parking_lot::MutexGuard">MutexGuard</a><T>)</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#219-221' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Blocks the current thread until this condition variable receives a
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notification.</p>
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<p>This function will atomically unlock the mutex specified (represented by
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<code>mutex_guard</code>) and block the current thread. This means that any calls
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to <code>notify_*()</code> which happen logically after the mutex is unlocked are
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candidates to wake this thread up. When this function call returns, the
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lock specified will have been re-acquired.</p>
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<h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
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<p>This function will panic if another thread is waiting on the <code>Condvar</code>
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with a different <code>Mutex</code> object.</p>
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</div><h4 id='method.wait_until' class="method"><span id='wait_until.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.wait_until' class='fnname'>wait_until</a><T: ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>>(<br> &self, <br> mutex_guard: &mut <a class="type" href="../parking_lot/type.MutexGuard.html" title="type parking_lot::MutexGuard">MutexGuard</a><T>, <br> timeout: <a class="struct" href="https://doc.rust-lang.org/nightly/std/time/struct.Instant.html" title="struct std::time::Instant">Instant</a><br>) -> <a class="struct" href="../parking_lot/struct.WaitTimeoutResult.html" title="struct parking_lot::WaitTimeoutResult">WaitTimeoutResult</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#247-256' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Waits on this condition variable for a notification, timing out after
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the specified time instant.</p>
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<p>The semantics of this function are equivalent to <code>wait()</code> except that
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the thread will be blocked roughly until <code>timeout</code> is reached. This
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method should not be used for precise timing due to anomalies such as
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preemption or platform differences that may not cause the maximum
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amount of time waited to be precisely <code>timeout</code>.</p>
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<p>Note that the best effort is made to ensure that the time waited is
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measured with a monotonic clock, and not affected by the changes made to
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the system time.</p>
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<p>The returned <code>WaitTimeoutResult</code> value indicates if the timeout is
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known to have elapsed.</p>
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<p>Like <code>wait</code>, the lock specified will be re-acquired when this function
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returns, regardless of whether the timeout elapsed or not.</p>
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<h1 id="panics-1" class="section-header"><a href="#panics-1">Panics</a></h1>
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<p>This function will panic if another thread is waiting on the <code>Condvar</code>
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with a different <code>Mutex</code> object.</p>
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</div><h4 id='method.wait_for' class="method"><span id='wait_for.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.wait_for' class='fnname'>wait_for</a><T: ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>>(<br> &self, <br> guard: &mut <a class="type" href="../parking_lot/type.MutexGuard.html" title="type parking_lot::MutexGuard">MutexGuard</a><T>, <br> timeout: <a class="struct" href="https://doc.rust-lang.org/nightly/core/time/struct.Duration.html" title="struct core::time::Duration">Duration</a><br>) -> <a class="struct" href="../parking_lot/struct.WaitTimeoutResult.html" title="struct parking_lot::WaitTimeoutResult">WaitTimeoutResult</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#349-355' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Waits on this condition variable for a notification, timing out after a
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specified duration.</p>
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<p>The semantics of this function are equivalent to <code>wait()</code> except that
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the thread will be blocked for roughly no longer than <code>timeout</code>. This
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method should not be used for precise timing due to anomalies such as
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preemption or platform differences that may not cause the maximum
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amount of time waited to be precisely <code>timeout</code>.</p>
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<p>Note that the best effort is made to ensure that the time waited is
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measured with a monotonic clock, and not affected by the changes made to
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the system time.</p>
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<p>The returned <code>WaitTimeoutResult</code> value indicates if the timeout is
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known to have elapsed.</p>
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<p>Like <code>wait</code>, the lock specified will be re-acquired when this function
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returns, regardless of whether the timeout elapsed or not.</p>
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</div></div><h2 id='implementations' class='small-section-header'>Trait Implementations<a href='#implementations' class='anchor'></a></h2><div id='implementations-list'><h3 id='impl-Default' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html" title="trait core::default::Default">Default</a> for <a class="struct" href="../parking_lot/struct.Condvar.html" title="struct parking_lot::Condvar">Condvar</a></code><a href='#impl-Default' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#358-363' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.default' class="method"><span id='default.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/default/trait.Default.html#tymethod.default' class='fnname'>default</a>() -> <a class="struct" href="../parking_lot/struct.Condvar.html" title="struct parking_lot::Condvar">Condvar</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#360-362' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns the "default value" for a type. <a href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html#tymethod.default">Read more</a></p>
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</div></div><h3 id='impl-Debug' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="struct" href="../parking_lot/struct.Condvar.html" title="struct parking_lot::Condvar">Condvar</a></code><a href='#impl-Debug' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#365-369' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>) -> <a class="type" href="https://doc.rust-lang.org/nightly/core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/parking_lot/condvar.rs.html#366-368' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Formats the value using the given formatter. <a href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p>
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||
</div></div></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'><h3 id='impl-Send' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="../parking_lot/struct.Condvar.html" title="struct parking_lot::Condvar">Condvar</a></code><a href='#impl-Send' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-Sync' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="struct" href="../parking_lot/struct.Condvar.html" title="struct parking_lot::Condvar">Condvar</a></code><a href='#impl-Sync' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div></div></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../";window.currentCrate = "parking_lot";</script><script src="../aliases.js"></script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html> |