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</pre><div class="example-wrap"><pre class="rust ">
<span class="comment">// Copyright 2020 Shin Yoshida</span>
<span class="comment">//</span>
<span class="comment">// "LGPL-3.0-or-later OR Apache-2.0 OR BSD-2-Clause"</span>
<span class="comment">//</span>
<span class="comment">// This is part of spin-sync</span>
<span class="comment">//</span>
<span class="comment">// spin-sync is free software: you can redistribute it and/or modify</span>
<span class="comment">// it under the terms of the GNU Lesser General Public License as published by</span>
<span class="comment">// the Free Software Foundation, either version 3 of the License, or</span>
<span class="comment">// (at your option) any later version.</span>
<span class="comment">//</span>
<span class="comment">// spin-sync is distributed in the hope that it will be useful,</span>
<span class="comment">// but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<span class="comment">// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span>
<span class="comment">// GNU Lesser General Public License for more details.</span>
<span class="comment">//</span>
<span class="comment">// You should have received a copy of the GNU Lesser General Public License</span>
<span class="comment">// along with spin-sync. If not, see <http://www.gnu.org/licenses/>.</span>
<span class="comment">//</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 (the "License");</span>
<span class="comment">// you may not use this file except in compliance with the License.</span>
<span class="comment">// You may obtain a copy of the License at</span>
<span class="comment">//</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0</span>
<span class="comment">//</span>
<span class="comment">// Unless required by applicable law or agreed to in writing, software</span>
<span class="comment">// distributed under the License is distributed on an "AS IS" BASIS,</span>
<span class="comment">// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.</span>
<span class="comment">// See the License for the specific language governing permissions and</span>
<span class="comment">// limitations under the License.</span>
<span class="comment">//</span>
<span class="comment">//</span>
<span class="comment">// Redistribution and use in source and binary forms, with or without modification, are permitted</span>
<span class="comment">// provided that the following conditions are met:</span>
<span class="comment">//</span>
<span class="comment">// 1. Redistributions of source code must retain the above copyright notice, this list of</span>
<span class="comment">// conditions and the following disclaimer.</span>
<span class="comment">// 2. Redistributions in binary form must reproduce the above copyright notice, this</span>
<span class="comment">// list of conditions and the following disclaimer in the documentation and/or other</span>
<span class="comment">// materials provided with the distribution.</span>
<span class="comment">//</span>
<span class="comment">// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND</span>
<span class="comment">// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED</span>
<span class="comment">// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.</span>
<span class="comment">// IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,</span>
<span class="comment">// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT</span>
<span class="comment">// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR</span>
<span class="comment">// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,</span>
<span class="comment">// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)</span>
<span class="comment">// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE</span>
<span class="comment">// POSSIBILITY OF SUCH DAMAGE.</span>
<span class="kw">use</span> <span class="kw">crate</span>::<span class="ident">misc</span>::<span class="ident">PhantomOnce</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">atomic</span>::{<span class="ident">AtomicU8</span>, <span class="ident">Ordering</span>};
<span class="doccomment">/// A synchronization primitive which can be used to run a one-time global initialization.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `Once` behaves like `std::sync::Once` except for using spinlock.</span>
<span class="doccomment">/// Useful for one-time initialization for FFI or related functionality.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use spin_sync::Once;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// static INIT: Once = Once::new();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// INIT.call_once(|| {</span>
<span class="doccomment">/// // Do some initialization here.</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Once</span> {
<span class="ident">state</span>: <span class="ident">AtomicU8</span>,
<span class="ident">_phantom</span>: <span class="ident">PhantomOnce</span>,
}
<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Once</span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">f</span>.<span class="ident">pad</span>(<span class="string">"Once { .. }"</span>)
}
}
<span class="kw">impl</span> <span class="ident">Once</span> {
<span class="doccomment">/// Create a new `Once` instance.</span>
<span class="kw">pub</span> <span class="kw">const</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="self">Self</span> {
<span class="ident">state</span>: <span class="ident">AtomicU8</span>::<span class="ident">new</span>(<span class="ident">OnceState</span>::<span class="ident">default</span>().<span class="ident">state</span>),
<span class="ident">_phantom</span>: <span class="ident">PhantomOnce</span> {},
}
}
<span class="doccomment">/// Performs an initialization routine once and only once. The given closure will be executed</span>
<span class="doccomment">/// if this is the first time [`call_once`] has been called, and otherwise the routine will not be invoked.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method will block the calling thread if another initialization routine is currently running.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// When this function returns, it is guaranteed that some initialization has run and completed</span>
<span class="doccomment">/// (it may not be the closure specified). It is also guaranteed that any memory writes performed</span>
<span class="doccomment">/// by the executed closure can be reliably observed by other threads at this point (there is a happens-before</span>
<span class="doccomment">/// relation between the closure and code executing after the return).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If the given closure recursively invokes [`call_once`] on the same `Once` instance the exact behavior</span>
<span class="doccomment">/// is not specified, allowed outcomes are a panic or a deadlock.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`call_once`]: #method.call_once</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `Once` enable to access static mut data safely.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use spin_sync::Once;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// static mut CACHE: usize = 0;</span>
<span class="doccomment">/// static INIT: Once = Once::new();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn expensive_calculation(val: usize) -> usize {</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// INIT.call_once(|| { CACHE = val; });</span>
<span class="doccomment">/// CACHE</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // INIT.call_once() invokes the closure and set the CACHE.</span>
<span class="doccomment">/// assert_eq!(1, expensive_calculation(1));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // INIT.call_once() do nothing and return the CACHE.</span>
<span class="doccomment">/// assert_eq!(1, expensive_calculation(2));</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The closure f will only be executed once if this is called concurrently among</span>
<span class="doccomment">/// many threads. If that closure panics, however, then it will poison this `Once` instance,</span>
<span class="doccomment">/// causing all future invocations of [`call_once`] to also panic.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`call_once`]: #method.call_once</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">call_once</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnOnce</span>()<span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) {
<span class="kw">let</span> (<span class="ident">_guard</span>, <span class="ident">s</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>();
<span class="kw">if</span> <span class="ident">s</span>.<span class="ident">poisoned</span>() {
<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"`Once.call_once()' is called while the instance is poisoned."</span>);
}
<span class="kw">if</span> <span class="ident">s</span>.<span class="ident">finished</span>() {
<span class="kw">return</span>;
}
<span class="ident">f</span>();
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">finish</span>();
<span class="self">self</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">s</span>.<span class="ident">state</span>, <span class="ident">Ordering</span>::<span class="ident">Relaxed</span>);
}
<span class="doccomment">/// Performs the same function as [`call_once`] except ignores poisoning.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Unlike [`call_once`], if this `Once` has been poisoned (i.e., a previous call to [`call_once`]</span>
<span class="doccomment">/// or [`call_once_force`] caused a panic), calling [`call_once_force`] will still invoke the closure</span>
<span class="doccomment">/// f and will not result in an immediate panic. If f panics, the `Once` will remain in a poison state.</span>
<span class="doccomment">/// If f does not panic, the `Once` will no longer be in a poison state and all future calls to</span>
<span class="doccomment">/// [`call_once`] or [`call_once_force`] will be no-ops.</span>
<span class="doccomment">///</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The closure f is yielded a [`OnceState`] structure which can be used to query the poison status of the `Once`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`call_once`]: #method.call_once</span>
<span class="doccomment">/// [`call_once_force`]: #method.call_once_force</span>
<span class="doccomment">/// [`OnceState`]: struct.OnceState.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use spin_sync::Once;</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// static INIT: Once = Once::new();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Poison INIT</span>
<span class="doccomment">/// let handle = thread::spawn(|| {</span>
<span class="doccomment">/// INIT.call_once(|| panic!());</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// assert!(handle.join().is_err());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Poisoning propagates</span>
<span class="doccomment">/// let handle = thread::spawn(|| {</span>
<span class="doccomment">/// INIT.call_once(|| {});</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// assert!(handle.join().is_err());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // call_once_force will still run and reset the poisoned state</span>
<span class="doccomment">/// INIT.call_once_force(|state| {</span>
<span class="doccomment">/// assert!(state.poisoned());</span>
<span class="doccomment">/// });</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // once any success happens, we stop propagating the poison</span>
<span class="doccomment">/// INIT.call_once(|| {});</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">call_once_force</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="kw-2">&</span><span class="ident">OnceState</span>)<span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) {
<span class="kw">let</span> (<span class="ident">_guard</span>, <span class="ident">s</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>();
<span class="kw">if</span> <span class="ident">s</span>.<span class="ident">finished</span>() {
<span class="kw">return</span>;
}
<span class="ident">f</span>(<span class="kw-2">&</span><span class="ident">s</span>);
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">finish</span>();
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">unpoison</span>();
<span class="self">self</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">s</span>.<span class="ident">state</span>, <span class="ident">Ordering</span>::<span class="ident">Relaxed</span>);
}
<span class="doccomment">/// Returns true if some [`call_once`] call has completed successfully.</span>
<span class="doccomment">/// Specifically, [`is_completed`] will return false in the following situations:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Neither [`call_once`] nor [`call_once_force`] was not called at all,</span>
<span class="doccomment">/// * [`call_once`] or/and [`call_once_force`] was called, but has not yet completed,</span>
<span class="doccomment">/// * the `Once` instance is poisoned</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function returning false does not mean that `Once` has not been executed.</span>
<span class="doccomment">/// For example, it may have been executed in the time between when [`is_completed`]</span>
<span class="doccomment">/// starts executing and when it returns, in which case the false return value would</span>
<span class="doccomment">/// be stale (but still permissible).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`call_once`]: #method.call_once</span>
<span class="doccomment">/// [`call_once_force`]: #method.call_once_force</span>
<span class="doccomment">/// [`is_completed`]: #method.is_completed</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `call_once` was succeeded.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use spin_sync::Once;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// static INIT: Once = Once::new();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(INIT.is_completed(), false);</span>
<span class="doccomment">/// INIT.call_once(|| {</span>
<span class="doccomment">/// assert_eq!(INIT.is_completed(), false);</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// assert_eq!(INIT.is_completed(), true);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `call_once` caused panic.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use spin_sync::Once;</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// static INIT: Once = Once::new();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(INIT.is_completed(), false);</span>
<span class="doccomment">/// let handle = thread::spawn(|| {</span>
<span class="doccomment">/// INIT.call_once(|| panic!());</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// assert!(handle.join().is_err());</span>
<span class="doccomment">/// assert_eq!(INIT.is_completed(), false);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_completed</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">OnceState</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Ordering</span>::<span class="ident">Relaxed</span>));
(<span class="op">!</span><span class="ident">s</span>.<span class="ident">poisoned</span>()) <span class="op">&&</span> (<span class="ident">s</span>.<span class="ident">finished</span>())
}
<span class="kw">fn</span> <span class="ident">lock</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> (<span class="ident">OnceGuard</span>, <span class="ident">OnceState</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">expected</span> <span class="op">=</span> <span class="ident">OnceState</span>::<span class="ident">default</span>();
<span class="kw">loop</span> {
<span class="kw">let</span> <span class="ident">desired</span> <span class="op">=</span> <span class="ident">expected</span>.<span class="ident">acquire_lock</span>();
<span class="kw">let</span> <span class="ident">current</span> <span class="op">=</span> <span class="ident">OnceState</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">state</span>.<span class="ident">compare_and_swap</span>(
<span class="ident">expected</span>.<span class="ident">state</span>,
<span class="ident">desired</span>.<span class="ident">state</span>,
<span class="ident">Ordering</span>::<span class="ident">Acquire</span>,
));
<span class="comment">// self is locked now. Try again later.</span>
<span class="kw">if</span> <span class="ident">current</span>.<span class="ident">locked</span>() {
<span class="ident">expected</span> <span class="op">=</span> <span class="ident">current</span>.<span class="ident">release_lock</span>();
<span class="ident">std</span>::<span class="ident">thread</span>::<span class="ident">yield_now</span>();
<span class="kw">continue</span>;
}
<span class="comment">// Succeed</span>
<span class="kw">if</span> <span class="ident">current</span>.<span class="ident">state</span> <span class="op">=</span><span class="op">=</span> <span class="ident">expected</span>.<span class="ident">state</span> {
<span class="kw">return</span> (<span class="ident">OnceGuard</span> { <span class="ident">once</span>: <span class="kw-2">&</span><span class="self">self</span> }, <span class="ident">desired</span>);
}
<span class="comment">// expected was wrong.</span>
<span class="ident">expected</span> <span class="op">=</span> <span class="ident">current</span>;
}
}
}
<span class="kw">struct</span> <span class="ident">OnceGuard</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">once</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Once</span>,
}
<span class="kw">impl</span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">OnceGuard</span><span class="op"><</span><span class="lifetime">'_</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">OnceState</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">once</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Ordering</span>::<span class="ident">Relaxed</span>));
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">locked</span>());
<span class="kw">if</span> <span class="ident">std</span>::<span class="ident">thread</span>::<span class="ident">panicking</span>() {
<span class="ident">s</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">poison</span>();
}
<span class="ident">s</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">release_lock</span>();
<span class="self">self</span>.<span class="ident">once</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">s</span>.<span class="ident">state</span>, <span class="ident">Ordering</span>::<span class="ident">Release</span>);
}
}
<span class="doccomment">/// State yielded to [`call_once_force`] ’s closure parameter. The state can be used to query</span>
<span class="doccomment">/// the poison status of the [`Once`]</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`call_once_force`]: struct.Once.html#method.call_once_force</span>
<span class="doccomment">/// [`Once`]: struct.Once.html</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">OnceState</span> {
<span class="ident">state</span>: <span class="ident">u8</span>,
}
<span class="kw">impl</span> <span class="ident">OnceState</span> {
<span class="kw">const</span> <span class="ident">INIT</span>: <span class="ident">u8</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">const</span> <span class="ident">LOCK</span>: <span class="ident">u8</span> <span class="op">=</span> <span class="number">1</span>;
<span class="kw">const</span> <span class="ident">FINISHED</span>: <span class="ident">u8</span> <span class="op">=</span> <span class="number">2</span>;
<span class="kw">const</span> <span class="ident">POISONED</span>: <span class="ident">u8</span> <span class="op">=</span> <span class="number">4</span>;
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">const</span> <span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="self">Self</span> { <span class="ident">state</span>: <span class="self">Self</span>::<span class="ident">INIT</span> }
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">const</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">state</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="self">Self</span> { <span class="ident">state</span> }
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">const</span> <span class="kw">fn</span> <span class="ident">locked</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
(<span class="self">self</span>.<span class="ident">state</span> <span class="op">&</span> <span class="self">Self</span>::<span class="ident">LOCK</span>) <span class="op">!</span><span class="op">=</span> <span class="number">0</span>
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">const</span> <span class="kw">fn</span> <span class="ident">finished</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
(<span class="self">self</span>.<span class="ident">state</span> <span class="op">&</span> <span class="self">Self</span>::<span class="ident">FINISHED</span>) <span class="op">!</span><span class="op">=</span> <span class="number">0</span>
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="doccomment">/// Returns true if the associated [`Once`] was poisoned prior to the invocation of the closure</span>
<span class="doccomment">/// passed to [`call_once_force`] .</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Once`]: struct.Once.html</span>
<span class="doccomment">/// [`call_once_force`]: struct.Once.html#method.call_once_force</span>
<span class="kw">pub</span> <span class="kw">const</span> <span class="kw">fn</span> <span class="ident">poisoned</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
(<span class="self">self</span>.<span class="ident">state</span> <span class="op">&</span> <span class="self">Self</span>::<span class="ident">POISONED</span>) <span class="op">!</span><span class="op">=</span> <span class="number">0</span>
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">fn</span> <span class="ident">acquire_lock</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="op">!</span><span class="self">self</span>.<span class="ident">locked</span>());
<span class="self">Self</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">state</span> <span class="op">|</span> <span class="self">Self</span>::<span class="ident">LOCK</span>)
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">fn</span> <span class="ident">release_lock</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">locked</span>());
<span class="self">Self</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">state</span> <span class="op">^</span> <span class="self">Self</span>::<span class="ident">LOCK</span>)
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">fn</span> <span class="ident">finish</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="op">!</span><span class="self">self</span>.<span class="ident">finished</span>());
<span class="self">Self</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">state</span> <span class="op">|</span> <span class="self">Self</span>::<span class="ident">FINISHED</span>)
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">fn</span> <span class="ident">poison</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="self">Self</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">state</span> <span class="op">|</span> <span class="self">Self</span>::<span class="ident">POISONED</span>)
}
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="kw">fn</span> <span class="ident">unpoison</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="self">Self</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">state</span> <span class="op">^</span> <span class="self">Self</span>::<span class="ident">POISONED</span>)
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">tests</span> {
<span class="kw">use</span> <span class="kw">super</span>::<span class="kw-2">*</span>;
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">call_once_invoke_task_only_once</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">val</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="ident">once</span> <span class="op">=</span> <span class="ident">Once</span>::<span class="ident">new</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>, <span class="ident">val</span>);
<span class="ident">once</span>.<span class="ident">call_once</span>(<span class="op">|</span><span class="op">|</span> <span class="ident">val</span> <span class="op">=</span> <span class="number">1</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">1</span>, <span class="ident">val</span>);
<span class="ident">once</span>.<span class="ident">call_once</span>(<span class="op">|</span><span class="op">|</span> <span class="ident">val</span> <span class="op">=</span> <span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">1</span>, <span class="ident">val</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">call_once_force_do_nothing_after_call_once_succeeded</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">val</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">let</span> <span class="ident">once</span> <span class="op">=</span> <span class="ident">Once</span>::<span class="ident">new</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>, <span class="ident">val</span>);
<span class="ident">once</span>.<span class="ident">call_once</span>(<span class="op">|</span><span class="op">|</span> <span class="ident">val</span> <span class="op">=</span> <span class="number">1</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">1</span>, <span class="ident">val</span>);
<span class="ident">once</span>.<span class="ident">call_once_force</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">val</span> <span class="op">=</span> <span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">1</span>, <span class="ident">val</span>);
}
}
</pre></div>
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