<!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="Source to the Rust file `liballoc/arc.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>arc.rs.html -- source</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><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[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><a href='../../alloc/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a></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"><pre class="line-numbers"><span id="1"> 1</span>
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</pre><pre class="rust ">
<span class="comment">// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="attribute">#![<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="doccomment">//! Thread-safe reference-counting pointers.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! See the [`Arc<T>`][arc] documentation for more details.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [arc]: struct.Arc.html</span>
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">any</span>::<span class="ident">Any</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">sync</span>::<span class="ident">atomic</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">sync</span>::<span class="ident">atomic</span>::<span class="ident">Ordering</span>::{<span class="ident">Acquire</span>, <span class="ident">Relaxed</span>, <span class="ident">Release</span>, <span class="ident">SeqCst</span>};
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">borrow</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">cmp</span>::<span class="ident">Ordering</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">intrinsics</span>::<span class="ident">abort</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">mem</span>::{<span class="self">self</span>, <span class="ident">align_of_val</span>, <span class="ident">size_of_val</span>, <span class="ident">uninitialized</span>};
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ops</span>::<span class="ident">Deref</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ops</span>::<span class="ident">CoerceUnsized</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ptr</span>::{<span class="self">self</span>, <span class="ident">NonNull</span>};
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">marker</span>::{<span class="ident">Unsize</span>, <span class="ident">PhantomData</span>};
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">hash</span>::{<span class="ident">Hash</span>, <span class="ident">Hasher</span>};
<span class="kw">use</span> <span class="ident">core</span>::{<span class="ident">isize</span>, <span class="ident">usize</span>};
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">convert</span>::<span class="ident">From</span>;
<span class="kw">use</span> <span class="ident">alloc</span>::{<span class="ident">Global</span>, <span class="ident">Alloc</span>, <span class="ident">Layout</span>, <span class="ident">box_free</span>, <span class="ident">handle_alloc_error</span>};
<span class="kw">use</span> <span class="ident">boxed</span>::<span class="ident">Box</span>;
<span class="kw">use</span> <span class="ident">string</span>::<span class="ident">String</span>;
<span class="kw">use</span> <span class="ident">vec</span>::<span class="ident">Vec</span>;
<span class="doccomment">/// A soft limit on the amount of references that may be made to an `Arc`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Going above this limit will abort your program (although not</span>
<span class="doccomment">/// necessarily) at _exactly_ `MAX_REFCOUNT + 1` references.</span>
<span class="kw">const</span> <span class="ident">MAX_REFCOUNT</span>: <span class="ident">usize</span> <span class="op">=</span> (<span class="ident">isize</span>::<span class="ident">MAX</span>) <span class="kw">as</span> <span class="ident">usize</span>;
<span class="doccomment">/// A thread-safe reference-counting pointer. 'Arc' stands for 'Atomically</span>
<span class="doccomment">/// Reference Counted'.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The type `Arc<T>` provides shared ownership of a value of type `T`,</span>
<span class="doccomment">/// allocated in the heap. Invoking [`clone`][clone] on `Arc` produces</span>
<span class="doccomment">/// a new pointer to the same value in the heap. When the last `Arc`</span>
<span class="doccomment">/// pointer to a given value is destroyed, the pointed-to value is</span>
<span class="doccomment">/// also destroyed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Shared references in Rust disallow mutation by default, and `Arc` is no</span>
<span class="doccomment">/// exception: you cannot generally obtain a mutable reference to something</span>
<span class="doccomment">/// inside an `Arc`. If you need to mutate through an `Arc`, use</span>
<span class="doccomment">/// [`Mutex`][mutex], [`RwLock`][rwlock], or one of the [`Atomic`][atomic]</span>
<span class="doccomment">/// types.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Thread Safety</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Unlike [`Rc<T>`], `Arc<T>` uses atomic operations for its reference</span>
<span class="doccomment">/// counting. This means that it is thread-safe. The disadvantage is that</span>
<span class="doccomment">/// atomic operations are more expensive than ordinary memory accesses. If you</span>
<span class="doccomment">/// are not sharing reference-counted values between threads, consider using</span>
<span class="doccomment">/// [`Rc<T>`] for lower overhead. [`Rc<T>`] is a safe default, because the</span>
<span class="doccomment">/// compiler will catch any attempt to send an [`Rc<T>`] between threads.</span>
<span class="doccomment">/// However, a library might choose `Arc<T>` in order to give library consumers</span>
<span class="doccomment">/// more flexibility.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `Arc<T>` will implement [`Send`] and [`Sync`] as long as the `T` implements</span>
<span class="doccomment">/// [`Send`] and [`Sync`]. Why can't you put a non-thread-safe type `T` in an</span>
<span class="doccomment">/// `Arc<T>` to make it thread-safe? This may be a bit counter-intuitive at</span>
<span class="doccomment">/// first: after all, isn't the point of `Arc<T>` thread safety? The key is</span>
<span class="doccomment">/// this: `Arc<T>` makes it thread safe to have multiple ownership of the same</span>
<span class="doccomment">/// data, but it doesn't add thread safety to its data. Consider</span>
<span class="doccomment">/// `Arc<`[`RefCell<T>`]`>`. [`RefCell<T>`] isn't [`Sync`], and if `Arc<T>` was always</span>
<span class="doccomment">/// [`Send`], `Arc<`[`RefCell<T>`]`>` would be as well. But then we'd have a problem:</span>
<span class="doccomment">/// [`RefCell<T>`] is not thread safe; it keeps track of the borrowing count using</span>
<span class="doccomment">/// non-atomic operations.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// In the end, this means that you may need to pair `Arc<T>` with some sort of</span>
<span class="doccomment">/// [`std::sync`] type, usually [`Mutex<T>`][mutex].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Breaking cycles with `Weak`</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The [`downgrade`][downgrade] method can be used to create a non-owning</span>
<span class="doccomment">/// [`Weak`][weak] pointer. A [`Weak`][weak] pointer can be [`upgrade`][upgrade]d</span>
<span class="doccomment">/// to an `Arc`, but this will return [`None`] if the value has already been</span>
<span class="doccomment">/// dropped.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A cycle between `Arc` pointers will never be deallocated. For this reason,</span>
<span class="doccomment">/// [`Weak`][weak] is used to break cycles. For example, a tree could have</span>
<span class="doccomment">/// strong `Arc` pointers from parent nodes to children, and [`Weak`][weak]</span>
<span class="doccomment">/// pointers from children back to their parents.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Cloning references</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Creating a new reference from an existing reference counted pointer is done using the</span>
<span class="doccomment">/// `Clone` trait implemented for [`Arc<T>`][arc] and [`Weak<T>`][weak].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">/// let foo = Arc::new(vec![1.0, 2.0, 3.0]);</span>
<span class="doccomment">/// // The two syntaxes below are equivalent.</span>
<span class="doccomment">/// let a = foo.clone();</span>
<span class="doccomment">/// let b = Arc::clone(&foo);</span>
<span class="doccomment">/// // a and b both point to the same memory location as foo.</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The [`Arc::clone(&from)`] syntax is the most idiomatic because it conveys more explicitly</span>
<span class="doccomment">/// the meaning of the code. In the example above, this syntax makes it easier to see that</span>
<span class="doccomment">/// this code is creating a new reference rather than copying the whole content of foo.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## `Deref` behavior</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `Arc<T>` automatically dereferences to `T` (via the [`Deref`][deref] trait),</span>
<span class="doccomment">/// so you can call `T`'s methods on a value of type `Arc<T>`. To avoid name</span>
<span class="doccomment">/// clashes with `T`'s methods, the methods of `Arc<T>` itself are [associated</span>
<span class="doccomment">/// functions][assoc], called using function-like syntax:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">/// let my_arc = Arc::new(());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Arc::downgrade(&my_arc);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Weak<T>`][weak] does not auto-dereference to `T`, because the value may have</span>
<span class="doccomment">/// already been destroyed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [arc]: struct.Arc.html</span>
<span class="doccomment">/// [weak]: struct.Weak.html</span>
<span class="doccomment">/// [`Rc<T>`]: ../../std/rc/struct.Rc.html</span>
<span class="doccomment">/// [clone]: ../../std/clone/trait.Clone.html#tymethod.clone</span>
<span class="doccomment">/// [mutex]: ../../std/sync/struct.Mutex.html</span>
<span class="doccomment">/// [rwlock]: ../../std/sync/struct.RwLock.html</span>
<span class="doccomment">/// [atomic]: ../../std/sync/atomic/index.html</span>
<span class="doccomment">/// [`Send`]: ../../std/marker/trait.Send.html</span>
<span class="doccomment">/// [`Sync`]: ../../std/marker/trait.Sync.html</span>
<span class="doccomment">/// [deref]: ../../std/ops/trait.Deref.html</span>
<span class="doccomment">/// [downgrade]: struct.Arc.html#method.downgrade</span>
<span class="doccomment">/// [upgrade]: struct.Weak.html#method.upgrade</span>
<span class="doccomment">/// [`None`]: ../../std/option/enum.Option.html#variant.None</span>
<span class="doccomment">/// [assoc]: ../../book/first-edition/method-syntax.html#associated-functions</span>
<span class="doccomment">/// [`RefCell<T>`]: ../../std/cell/struct.RefCell.html</span>
<span class="doccomment">/// [`std::sync`]: ../../std/sync/index.html</span>
<span class="doccomment">/// [`Arc::clone(&from)`]: #method.clone</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Sharing some immutable data between threads:</span>
<span class="doccomment">///</span>
<span class="comment">// Note that we **do not** run these tests here. The windows builders get super</span>
<span class="comment">// unhappy if a thread outlives the main thread and then exits at the same time</span>
<span class="comment">// (something deadlocks) so we just avoid this entirely by not running these</span>
<span class="comment">// tests.</span>
<span class="doccomment">/// ```no_run</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// for _ in 0..10 {</span>
<span class="doccomment">/// let five = Arc::clone(&five);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// println!("{:?}", five);</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Sharing a mutable [`AtomicUsize`]:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`AtomicUsize`]: ../../std/sync/atomic/struct.AtomicUsize.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```no_run</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">/// use std::sync::atomic::{AtomicUsize, Ordering};</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let val = Arc::new(AtomicUsize::new(5));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// for _ in 0..10 {</span>
<span class="doccomment">/// let val = Arc::clone(&val);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::spawn(move || {</span>
<span class="doccomment">/// let v = val.fetch_add(1, Ordering::SeqCst);</span>
<span class="doccomment">/// println!("{:?}", v);</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See the [`rc` documentation][rc_examples] for more examples of reference</span>
<span class="doccomment">/// counting in general.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [rc_examples]: ../../std/rc/index.html#examples</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> {
<span class="ident">ptr</span>: <span class="ident">NonNull</span><span class="op"><</span><span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="ident">phantom</span>: <span class="ident">PhantomData</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>,
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Sync</span> <span class="op">+</span> <span class="ident">Send</span><span class="op">></span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Sync</span> <span class="op">+</span> <span class="ident">Send</span><span class="op">></span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"coerce_unsized"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"27732"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Unsize</span><span class="op"><</span><span class="ident">U</span><span class="op">></span>, <span class="ident">U</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">CoerceUnsized</span><span class="op"><</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">U</span><span class="op">>></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="doccomment">/// `Weak` is a version of [`Arc`] that holds a non-owning reference to the</span>
<span class="doccomment">/// managed value. The value is accessed by calling [`upgrade`] on the `Weak`</span>
<span class="doccomment">/// pointer, which returns an [`Option`]`<`[`Arc`]`<T>>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Since a `Weak` reference does not count towards ownership, it will not</span>
<span class="doccomment">/// prevent the inner value from being dropped, and `Weak` itself makes no</span>
<span class="doccomment">/// guarantees about the value still being present and may return [`None`]</span>
<span class="doccomment">/// when [`upgrade`]d.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A `Weak` pointer is useful for keeping a temporary reference to the value</span>
<span class="doccomment">/// within [`Arc`] without extending its lifetime. It is also used to prevent</span>
<span class="doccomment">/// circular references between [`Arc`] pointers, since mutual owning references</span>
<span class="doccomment">/// would never allow either [`Arc`] to be dropped. For example, a tree could</span>
<span class="doccomment">/// have strong [`Arc`] pointers from parent nodes to children, and `Weak`</span>
<span class="doccomment">/// pointers from children back to their parents.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The typical way to obtain a `Weak` pointer is to call [`Arc::downgrade`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Arc`]: struct.Arc.html</span>
<span class="doccomment">/// [`Arc::downgrade`]: struct.Arc.html#method.downgrade</span>
<span class="doccomment">/// [`upgrade`]: struct.Weak.html#method.upgrade</span>
<span class="doccomment">/// [`Option`]: ../../std/option/enum.Option.html</span>
<span class="doccomment">/// [`None`]: ../../std/option/enum.Option.html#variant.None</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> {
<span class="ident">ptr</span>: <span class="ident">NonNull</span><span class="op"><</span><span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Sync</span> <span class="op">+</span> <span class="ident">Send</span><span class="op">></span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Sync</span> <span class="op">+</span> <span class="ident">Send</span><span class="op">></span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"coerce_unsized"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"27732"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Unsize</span><span class="op"><</span><span class="ident">U</span><span class="op">></span>, <span class="ident">U</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">CoerceUnsized</span><span class="op"><</span><span class="ident">Weak</span><span class="op"><</span><span class="ident">U</span><span class="op">>></span> <span class="kw">for</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">fmt</span>::<span class="ident">Debug</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></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="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="macro">write</span><span class="macro">!</span>(<span class="ident">f</span>, <span class="string">"(Weak)"</span>)
}
}
<span class="kw">struct</span> <span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> {
<span class="ident">strong</span>: <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>,
<span class="comment">// the value usize::MAX acts as a sentinel for temporarily "locking" the</span>
<span class="comment">// ability to upgrade weak pointers or downgrade strong ones; this is used</span>
<span class="comment">// to avoid races in `make_mut` and `get_mut`.</span>
<span class="ident">weak</span>: <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>,
<span class="ident">data</span>: <span class="ident">T</span>,
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Sync</span> <span class="op">+</span> <span class="ident">Send</span><span class="op">></span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Sync</span> <span class="op">+</span> <span class="ident">Send</span><span class="op">></span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Constructs a new `Arc<T>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">data</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// Start the weak pointer count as 1 which is the weak pointer that's</span>
<span class="comment">// held by all the strong pointers (kinda), see std/rc.rs for more info</span>
<span class="kw">let</span> <span class="ident">x</span>: <span class="ident">Box</span><span class="op"><</span><span class="kw">_</span><span class="op">></span> <span class="op">=</span> <span class="kw">box</span> <span class="ident">ArcInner</span> {
<span class="ident">strong</span>: <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">1</span>),
<span class="ident">weak</span>: <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">1</span>),
<span class="ident">data</span>,
};
<span class="ident">Arc</span> { <span class="ident">ptr</span>: <span class="ident">Box</span>::<span class="ident">into_raw_non_null</span>(<span class="ident">x</span>), <span class="ident">phantom</span>: <span class="ident">PhantomData</span> }
}
<span class="doccomment">/// Returns the contained value, if the `Arc` has exactly one strong reference.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Otherwise, an [`Err`][result] is returned with the same `Arc` that was</span>
<span class="doccomment">/// passed in.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This will succeed even if there are outstanding weak references.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [result]: ../../std/result/enum.Result.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = Arc::new(3);</span>
<span class="doccomment">/// assert_eq!(Arc::try_unwrap(x), Ok(3));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = Arc::new(4);</span>
<span class="doccomment">/// let _y = Arc::clone(&x);</span>
<span class="doccomment">/// assert_eq!(*Arc::try_unwrap(x).unwrap_err(), 4);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_unique"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">try_unwrap</span>(<span class="ident">this</span>: <span class="self">Self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="self">Self</span><span class="op">></span> {
<span class="comment">// See `drop` for why all these atomics are like this</span>
<span class="kw">if</span> <span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">strong</span>.<span class="ident">compare_exchange</span>(<span class="number">1</span>, <span class="number">0</span>, <span class="ident">Release</span>, <span class="ident">Relaxed</span>).<span class="ident">is_err</span>() {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">this</span>);
}
<span class="ident">atomic</span>::<span class="ident">fence</span>(<span class="ident">Acquire</span>);
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">elem</span> <span class="op">=</span> <span class="ident">ptr</span>::<span class="ident">read</span>(<span class="kw-2">&</span><span class="ident">this</span>.<span class="ident">ptr</span>.<span class="ident">as_ref</span>().<span class="ident">data</span>);
<span class="comment">// Make a weak pointer to clean up the implicit strong-weak reference</span>
<span class="kw">let</span> <span class="ident">_weak</span> <span class="op">=</span> <span class="ident">Weak</span> { <span class="ident">ptr</span>: <span class="ident">this</span>.<span class="ident">ptr</span> };
<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="ident">this</span>);
<span class="prelude-val">Ok</span>(<span class="ident">elem</span>)
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Consumes the `Arc`, returning the wrapped pointer.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// To avoid a memory leak the pointer must be converted back to an `Arc` using</span>
<span class="doccomment">/// [`Arc::from_raw`][from_raw].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [from_raw]: struct.Arc.html#method.from_raw</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = Arc::new(10);</span>
<span class="doccomment">/// let x_ptr = Arc::into_raw(x);</span>
<span class="doccomment">/// assert_eq!(unsafe { *x_ptr }, 10);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rc_raw"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.17.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">into_raw</span>(<span class="ident">this</span>: <span class="self">Self</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span> {
<span class="kw">let</span> <span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">this</span>;
<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="ident">this</span>);
<span class="ident">ptr</span>
}
<span class="doccomment">/// Constructs an `Arc` from a raw pointer.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The raw pointer must have been previously returned by a call to a</span>
<span class="doccomment">/// [`Arc::into_raw`][into_raw].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is unsafe because improper use may lead to memory problems. For example, a</span>
<span class="doccomment">/// double-free may occur if the function is called twice on the same raw pointer.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [into_raw]: struct.Arc.html#method.into_raw</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = Arc::new(10);</span>
<span class="doccomment">/// let x_ptr = Arc::into_raw(x);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// // Convert back to an `Arc` to prevent leak.</span>
<span class="doccomment">/// let x = Arc::from_raw(x_ptr);</span>
<span class="doccomment">/// assert_eq!(*x, 10);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Further calls to `Arc::from_raw(x_ptr)` would be memory unsafe.</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rc_raw"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.17.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">from_raw</span>(<span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="comment">// Align the unsized value to the end of the ArcInner.</span>
<span class="comment">// Because it is ?Sized, it will always be the last field in memory.</span>
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">align_of_val</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">ptr</span>);
<span class="kw">let</span> <span class="ident">layout</span> <span class="op">=</span> <span class="ident">Layout</span>::<span class="ident">new</span>::<span class="op"><</span><span class="ident">ArcInner</span><span class="op"><</span>()<span class="op">>></span>();
<span class="kw">let</span> <span class="ident">offset</span> <span class="op">=</span> (<span class="ident">layout</span>.<span class="ident">size</span>() <span class="op">+</span> <span class="ident">layout</span>.<span class="ident">padding_needed_for</span>(<span class="ident">align</span>)) <span class="kw">as</span> <span class="ident">isize</span>;
<span class="comment">// Reverse the offset to find the original ArcInner.</span>
<span class="kw">let</span> <span class="ident">fake_ptr</span> <span class="op">=</span> <span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">let</span> <span class="ident">arc_ptr</span> <span class="op">=</span> <span class="ident">set_data_ptr</span>(<span class="ident">fake_ptr</span>, (<span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>).<span class="ident">offset</span>(<span class="op">-</span><span class="ident">offset</span>));
<span class="ident">Arc</span> {
<span class="ident">ptr</span>: <span class="ident">NonNull</span>::<span class="ident">new_unchecked</span>(<span class="ident">arc_ptr</span>),
<span class="ident">phantom</span>: <span class="ident">PhantomData</span>,
}
}
<span class="doccomment">/// Creates a new [`Weak`][weak] pointer to this value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [weak]: struct.Weak.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let weak_five = Arc::downgrade(&five);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">downgrade</span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// This Relaxed is OK because we're checking the value in the CAS</span>
<span class="comment">// below.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cur</span> <span class="op">=</span> <span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">load</span>(<span class="ident">Relaxed</span>);
<span class="kw">loop</span> {
<span class="comment">// check if the weak counter is currently "locked"; if so, spin.</span>
<span class="kw">if</span> <span class="ident">cur</span> <span class="op">==</span> <span class="ident">usize</span>::<span class="ident">MAX</span> {
<span class="ident">cur</span> <span class="op">=</span> <span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">load</span>(<span class="ident">Relaxed</span>);
<span class="kw">continue</span>;
}
<span class="comment">// NOTE: this code currently ignores the possibility of overflow</span>
<span class="comment">// into usize::MAX; in general both Rc and Arc need to be adjusted</span>
<span class="comment">// to deal with overflow.</span>
<span class="comment">// Unlike with Clone(), we need this to be an Acquire read to</span>
<span class="comment">// synchronize with the write coming from `is_unique`, so that the</span>
<span class="comment">// events prior to that write happen before this read.</span>
<span class="kw">match</span> <span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">compare_exchange_weak</span>(<span class="ident">cur</span>, <span class="ident">cur</span> <span class="op">+</span> <span class="number">1</span>, <span class="ident">Acquire</span>, <span class="ident">Relaxed</span>) {
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) <span class="op">=></span> <span class="kw">return</span> <span class="ident">Weak</span> { <span class="ident">ptr</span>: <span class="ident">this</span>.<span class="ident">ptr</span> },
<span class="prelude-val">Err</span>(<span class="ident">old</span>) <span class="op">=></span> <span class="ident">cur</span> <span class="op">=</span> <span class="ident">old</span>,
}
}
}
<span class="doccomment">/// Gets the number of [`Weak`][weak] pointers to this value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [weak]: struct.Weak.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Safety</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method by itself is safe, but using it correctly requires extra care.</span>
<span class="doccomment">/// Another thread can change the weak count at any time,</span>
<span class="doccomment">/// including potentially between calling this method and acting on the result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">/// let _weak_five = Arc::downgrade(&five);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // This assertion is deterministic because we haven't shared</span>
<span class="doccomment">/// // the `Arc` or `Weak` between threads.</span>
<span class="doccomment">/// assert_eq!(1, Arc::weak_count(&five));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_counts"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.15.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">weak_count</span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">let</span> <span class="ident">cnt</span> <span class="op">=</span> <span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>);
<span class="comment">// If the weak count is currently locked, the value of the</span>
<span class="comment">// count was 0 just before taking the lock.</span>
<span class="kw">if</span> <span class="ident">cnt</span> <span class="op">==</span> <span class="ident">usize</span>::<span class="ident">MAX</span> { <span class="number">0</span> } <span class="kw">else</span> { <span class="ident">cnt</span> <span class="op">-</span> <span class="number">1</span> }
}
<span class="doccomment">/// Gets the number of strong (`Arc`) pointers to this value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Safety</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method by itself is safe, but using it correctly requires extra care.</span>
<span class="doccomment">/// Another thread can change the strong count at any time,</span>
<span class="doccomment">/// including potentially between calling this method and acting on the result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">/// let _also_five = Arc::clone(&five);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // This assertion is deterministic because we haven't shared</span>
<span class="doccomment">/// // the `Arc` between threads.</span>
<span class="doccomment">/// assert_eq!(2, Arc::strong_count(&five));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_counts"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.15.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">strong_count</span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">strong</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>)
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">inner</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// This unsafety is ok because while this arc is alive we're guaranteed</span>
<span class="comment">// that the inner pointer is valid. Furthermore, we know that the</span>
<span class="comment">// `ArcInner` structure itself is `Sync` because the inner data is</span>
<span class="comment">// `Sync` as well, so we're ok loaning out an immutable pointer to these</span>
<span class="comment">// contents.</span>
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">as_ref</span>() }
}
<span class="comment">// Non-inlined part of `drop`.</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">never</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">drop_slow</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="comment">// Destroy the data at this time, even though we may not free the box</span>
<span class="comment">// allocation itself (there may still be weak pointers lying around).</span>
<span class="ident">ptr</span>::<span class="ident">drop_in_place</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">as_mut</span>().<span class="ident">data</span>);
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">fetch_sub</span>(<span class="number">1</span>, <span class="ident">Release</span>) <span class="op">==</span> <span class="number">1</span> {
<span class="ident">atomic</span>::<span class="ident">fence</span>(<span class="ident">Acquire</span>);
<span class="ident">Global</span>.<span class="ident">dealloc</span>(<span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">cast</span>(), <span class="ident">Layout</span>::<span class="ident">for_value</span>(<span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">as_ref</span>()))
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"ptr_eq"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.17.0"</span>)]</span>
<span class="doccomment">/// Returns true if the two `Arc`s point to the same value (not</span>
<span class="doccomment">/// just values that compare as equal).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">/// let same_five = Arc::clone(&five);</span>
<span class="doccomment">/// let other_five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(Arc::ptr_eq(&five, &same_five));</span>
<span class="doccomment">/// assert!(!Arc::ptr_eq(&five, &other_five));</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ptr_eq</span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="self">Self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="ident">this</span>.<span class="ident">ptr</span>.<span class="ident">as_ptr</span>() <span class="op">==</span> <span class="ident">other</span>.<span class="ident">ptr</span>.<span class="ident">as_ptr</span>()
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// Allocates an `ArcInner<T>` with sufficient space for an unsized value</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">allocate_for_ptr</span>(<span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// Create a fake ArcInner to find allocation size and alignment</span>
<span class="kw">let</span> <span class="ident">fake_ptr</span> <span class="op">=</span> <span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">let</span> <span class="ident">layout</span> <span class="op">=</span> <span class="ident">Layout</span>::<span class="ident">for_value</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">fake_ptr</span>);
<span class="kw">let</span> <span class="ident">mem</span> <span class="op">=</span> <span class="ident">Global</span>.<span class="ident">alloc</span>(<span class="ident">layout</span>)
.<span class="ident">unwrap_or_else</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">handle_alloc_error</span>(<span class="ident">layout</span>));
<span class="comment">// Initialize the real ArcInner</span>
<span class="kw">let</span> <span class="ident">inner</span> <span class="op">=</span> <span class="ident">set_data_ptr</span>(<span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">mem</span>.<span class="ident">as_ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="ident">ptr</span>::<span class="ident">write</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">inner</span>).<span class="ident">strong</span>, <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">1</span>));
<span class="ident">ptr</span>::<span class="ident">write</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">inner</span>).<span class="ident">weak</span>, <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">1</span>));
<span class="ident">inner</span>
}
<span class="kw">fn</span> <span class="ident">from_box</span>(<span class="ident">v</span>: <span class="ident">Box</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">box_unique</span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">into_unique</span>(<span class="ident">v</span>);
<span class="kw">let</span> <span class="ident">bptr</span> <span class="op">=</span> <span class="ident">box_unique</span>.<span class="ident">as_ptr</span>();
<span class="kw">let</span> <span class="ident">value_size</span> <span class="op">=</span> <span class="ident">size_of_val</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">bptr</span>);
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="self">Self</span>::<span class="ident">allocate_for_ptr</span>(<span class="ident">bptr</span>);
<span class="comment">// Copy value as bytes</span>
<span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(
<span class="ident">bptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">u8</span>,
<span class="kw-2">&</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">ptr</span>).<span class="ident">data</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw">_</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>,
<span class="ident">value_size</span>);
<span class="comment">// Free the allocation without dropping its contents</span>
<span class="ident">box_free</span>(<span class="ident">box_unique</span>);
<span class="ident">Arc</span> { <span class="ident">ptr</span>: <span class="ident">NonNull</span>::<span class="ident">new_unchecked</span>(<span class="ident">ptr</span>), <span class="ident">phantom</span>: <span class="ident">PhantomData</span> }
}
}
}
<span class="comment">// Sets the data pointer of a `?Sized` raw pointer.</span>
<span class="comment">//</span>
<span class="comment">// For a slice/trait object, this sets the `data` field and leaves the rest</span>
<span class="comment">// unchanged. For a sized raw pointer, this simply sets the pointer.</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">set_data_ptr</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span>, <span class="ident">U</span><span class="op">></span>(<span class="kw-2">mut</span> <span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">data</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">U</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="ident">ptr</span>::<span class="ident">write</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw">_</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>, <span class="ident">data</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>);
<span class="ident">ptr</span>
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="comment">// Copy elements from slice into newly allocated Arc<[T]></span>
<span class="comment">//</span>
<span class="comment">// Unsafe because the caller must either take ownership or bind `T: Copy`</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">copy_from_slice</span>(<span class="ident">v</span>: <span class="kw-2">&</span>[<span class="ident">T</span>]) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="kw">let</span> <span class="ident">v_ptr</span> <span class="op">=</span> <span class="ident">v</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> [<span class="ident">T</span>];
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="self">Self</span>::<span class="ident">allocate_for_ptr</span>(<span class="ident">v_ptr</span>);
<span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(
<span class="ident">v</span>.<span class="ident">as_ptr</span>(),
<span class="kw-2">&</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">ptr</span>).<span class="ident">data</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> [<span class="ident">T</span>] <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>,
<span class="ident">v</span>.<span class="ident">len</span>());
<span class="ident">Arc</span> { <span class="ident">ptr</span>: <span class="ident">NonNull</span>::<span class="ident">new_unchecked</span>(<span class="ident">ptr</span>), <span class="ident">phantom</span>: <span class="ident">PhantomData</span> }
}
}
<span class="comment">// Specialization trait used for From<&[T]></span>
<span class="kw">trait</span> <span class="ident">ArcFromSlice</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">from_slice</span>(<span class="ident">slice</span>: <span class="kw-2">&</span>[<span class="ident">T</span>]) <span class="op">-></span> <span class="self">Self</span>;
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Clone</span><span class="op">></span> <span class="ident">ArcFromSlice</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="ident">default</span> <span class="kw">fn</span> <span class="ident">from_slice</span>(<span class="ident">v</span>: <span class="kw-2">&</span>[<span class="ident">T</span>]) <span class="op">-></span> <span class="self">Self</span> {
<span class="comment">// Panic guard while cloning T elements.</span>
<span class="comment">// In the event of a panic, elements that have been written</span>
<span class="comment">// into the new ArcInner will be dropped, then the memory freed.</span>
<span class="kw">struct</span> <span class="ident">Guard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">mem</span>: <span class="ident">NonNull</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span>,
<span class="ident">elems</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>,
<span class="ident">layout</span>: <span class="ident">Layout</span>,
<span class="ident">n_elems</span>: <span class="ident">usize</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">Guard</span><span class="op"><</span><span class="ident">T</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">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::<span class="ident">from_raw_parts_mut</span>;
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="ident">from_raw_parts_mut</span>(<span class="self">self</span>.<span class="ident">elems</span>, <span class="self">self</span>.<span class="ident">n_elems</span>);
<span class="ident">ptr</span>::<span class="ident">drop_in_place</span>(<span class="ident">slice</span>);
<span class="ident">Global</span>.<span class="ident">dealloc</span>(<span class="self">self</span>.<span class="ident">mem</span>.<span class="ident">cast</span>(), <span class="self">self</span>.<span class="ident">layout</span>.<span class="ident">clone</span>());
}
}
}
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">v_ptr</span> <span class="op">=</span> <span class="ident">v</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> [<span class="ident">T</span>];
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="self">Self</span>::<span class="ident">allocate_for_ptr</span>(<span class="ident">v_ptr</span>);
<span class="kw">let</span> <span class="ident">mem</span> <span class="op">=</span> <span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="kw">_</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>;
<span class="kw">let</span> <span class="ident">layout</span> <span class="op">=</span> <span class="ident">Layout</span>::<span class="ident">for_value</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">ptr</span>);
<span class="comment">// Pointer to first element</span>
<span class="kw">let</span> <span class="ident">elems</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">ptr</span>).<span class="ident">data</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> [<span class="ident">T</span>] <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">Guard</span>{
<span class="ident">mem</span>: <span class="ident">NonNull</span>::<span class="ident">new_unchecked</span>(<span class="ident">mem</span>),
<span class="ident">elems</span>: <span class="ident">elems</span>,
<span class="ident">layout</span>: <span class="ident">layout</span>,
<span class="ident">n_elems</span>: <span class="number">0</span>,
};
<span class="kw">for</span> (<span class="ident">i</span>, <span class="ident">item</span>) <span class="kw">in</span> <span class="ident">v</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() {
<span class="ident">ptr</span>::<span class="ident">write</span>(<span class="ident">elems</span>.<span class="ident">offset</span>(<span class="ident">i</span> <span class="kw">as</span> <span class="ident">isize</span>), <span class="ident">item</span>.<span class="ident">clone</span>());
<span class="ident">guard</span>.<span class="ident">n_elems</span> <span class="op">+=</span> <span class="number">1</span>;
}
<span class="comment">// All clear. Forget the guard so it doesn't free the new ArcInner.</span>
<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="ident">guard</span>);
<span class="ident">Arc</span> { <span class="ident">ptr</span>: <span class="ident">NonNull</span>::<span class="ident">new_unchecked</span>(<span class="ident">ptr</span>), <span class="ident">phantom</span>: <span class="ident">PhantomData</span> }
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Copy</span><span class="op">></span> <span class="ident">ArcFromSlice</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from_slice</span>(<span class="ident">v</span>: <span class="kw-2">&</span>[<span class="ident">T</span>]) <span class="op">-></span> <span class="self">Self</span> {
<span class="kw">unsafe</span> { <span class="ident">Arc</span>::<span class="ident">copy_from_slice</span>(<span class="ident">v</span>) }
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Makes a clone of the `Arc` pointer.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This creates another pointer to the same inner value, increasing the</span>
<span class="doccomment">/// strong reference count.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Arc::clone(&five);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// Using a relaxed ordering is alright here, as knowledge of the</span>
<span class="comment">// original reference prevents other threads from erroneously deleting</span>
<span class="comment">// the object.</span>
<span class="comment">//</span>
<span class="comment">// As explained in the [Boost documentation][1], Increasing the</span>
<span class="comment">// reference counter can always be done with memory_order_relaxed: New</span>
<span class="comment">// references to an object can only be formed from an existing</span>
<span class="comment">// reference, and passing an existing reference from one thread to</span>
<span class="comment">// another must already provide any required synchronization.</span>
<span class="comment">//</span>
<span class="comment">// [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)</span>
<span class="kw">let</span> <span class="ident">old_size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">strong</span>.<span class="ident">fetch_add</span>(<span class="number">1</span>, <span class="ident">Relaxed</span>);
<span class="comment">// However we need to guard against massive refcounts in case someone</span>
<span class="comment">// is `mem::forget`ing Arcs. If we don't do this the count can overflow</span>
<span class="comment">// and users will use-after free. We racily saturate to `isize::MAX` on</span>
<span class="comment">// the assumption that there aren't ~2 billion threads incrementing</span>
<span class="comment">// the reference count at once. This branch will never be taken in</span>
<span class="comment">// any realistic program.</span>
<span class="comment">//</span>
<span class="comment">// We abort because such a program is incredibly degenerate, and we</span>
<span class="comment">// don't care to support it.</span>
<span class="kw">if</span> <span class="ident">old_size</span> <span class="op">></span> <span class="ident">MAX_REFCOUNT</span> {
<span class="kw">unsafe</span> {
<span class="ident">abort</span>();
}
}
<span class="ident">Arc</span> { <span class="ident">ptr</span>: <span class="self">self</span>.<span class="ident">ptr</span>, <span class="ident">phantom</span>: <span class="ident">PhantomData</span> }
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">data</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Clone</span><span class="op">></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Makes a mutable reference into the given `Arc`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If there are other `Arc` or [`Weak`][weak] pointers to the same value,</span>
<span class="doccomment">/// then `make_mut` will invoke [`clone`][clone] on the inner value to</span>
<span class="doccomment">/// ensure unique ownership. This is also referred to as clone-on-write.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See also [`get_mut`][get_mut], which will fail rather than cloning.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [weak]: struct.Weak.html</span>
<span class="doccomment">/// [clone]: ../../std/clone/trait.Clone.html#tymethod.clone</span>
<span class="doccomment">/// [get_mut]: struct.Arc.html#method.get_mut</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut data = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// *Arc::make_mut(&mut data) += 1; // Won't clone anything</span>
<span class="doccomment">/// let mut other_data = Arc::clone(&data); // Won't clone inner data</span>
<span class="doccomment">/// *Arc::make_mut(&mut data) += 1; // Clones inner data</span>
<span class="doccomment">/// *Arc::make_mut(&mut data) += 1; // Won't clone anything</span>
<span class="doccomment">/// *Arc::make_mut(&mut other_data) *= 2; // Won't clone anything</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Now `data` and `other_data` point to different values.</span>
<span class="doccomment">/// assert_eq!(*data, 8);</span>
<span class="doccomment">/// assert_eq!(*other_data, 12);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_unique"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">make_mut</span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">Self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="comment">// Note that we hold both a strong reference and a weak reference.</span>
<span class="comment">// Thus, releasing our strong reference only will not, by itself, cause</span>
<span class="comment">// the memory to be deallocated.</span>
<span class="comment">//</span>
<span class="comment">// Use Acquire to ensure that we see any writes to `weak` that happen</span>
<span class="comment">// before release writes (i.e., decrements) to `strong`. Since we hold a</span>
<span class="comment">// weak count, there's no chance the ArcInner itself could be</span>
<span class="comment">// deallocated.</span>
<span class="kw">if</span> <span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">strong</span>.<span class="ident">compare_exchange</span>(<span class="number">1</span>, <span class="number">0</span>, <span class="ident">Acquire</span>, <span class="ident">Relaxed</span>).<span class="ident">is_err</span>() {
<span class="comment">// Another strong pointer exists; clone</span>
<span class="kw-2">*</span><span class="ident">this</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>((<span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">this</span>).<span class="ident">clone</span>());
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">load</span>(<span class="ident">Relaxed</span>) <span class="op">!=</span> <span class="number">1</span> {
<span class="comment">// Relaxed suffices in the above because this is fundamentally an</span>
<span class="comment">// optimization: we are always racing with weak pointers being</span>
<span class="comment">// dropped. Worst case, we end up allocated a new Arc unnecessarily.</span>
<span class="comment">// We removed the last strong ref, but there are additional weak</span>
<span class="comment">// refs remaining. We'll move the contents to a new Arc, and</span>
<span class="comment">// invalidate the other weak refs.</span>
<span class="comment">// Note that it is not possible for the read of `weak` to yield</span>
<span class="comment">// usize::MAX (i.e., locked), since the weak count can only be</span>
<span class="comment">// locked by a thread with a strong reference.</span>
<span class="comment">// Materialize our own implicit weak pointer, so that it can clean</span>
<span class="comment">// up the ArcInner as needed.</span>
<span class="kw">let</span> <span class="ident">weak</span> <span class="op">=</span> <span class="ident">Weak</span> { <span class="ident">ptr</span>: <span class="ident">this</span>.<span class="ident">ptr</span> };
<span class="comment">// mark the data itself as already deallocated</span>
<span class="kw">unsafe</span> {
<span class="comment">// there is no data race in the implicit write caused by `read`</span>
<span class="comment">// here (due to zeroing) because data is no longer accessed by</span>
<span class="comment">// other threads (due to there being no more strong refs at this</span>
<span class="comment">// point).</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">swap</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">ptr</span>::<span class="ident">read</span>(<span class="kw-2">&</span><span class="ident">weak</span>.<span class="ident">ptr</span>.<span class="ident">as_ref</span>().<span class="ident">data</span>));
<span class="ident">mem</span>::<span class="ident">swap</span>(<span class="ident">this</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">swap</span>);
<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="ident">swap</span>);
}
} <span class="kw">else</span> {
<span class="comment">// We were the sole reference of either kind; bump back up the</span>
<span class="comment">// strong ref count.</span>
<span class="ident">this</span>.<span class="ident">inner</span>().<span class="ident">strong</span>.<span class="ident">store</span>(<span class="number">1</span>, <span class="ident">Release</span>);
}
<span class="comment">// As with `get_mut()`, the unsafety is ok because our reference was</span>
<span class="comment">// either unique to begin with, or became one upon cloning the contents.</span>
<span class="kw">unsafe</span> {
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">this</span>.<span class="ident">ptr</span>.<span class="ident">as_mut</span>().<span class="ident">data</span>
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Returns a mutable reference to the inner value, if there are</span>
<span class="doccomment">/// no other `Arc` or [`Weak`][weak] pointers to the same value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns [`None`][option] otherwise, because it is not safe to</span>
<span class="doccomment">/// mutate a shared value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See also [`make_mut`][make_mut], which will [`clone`][clone]</span>
<span class="doccomment">/// the inner value when it's shared.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [weak]: struct.Weak.html</span>
<span class="doccomment">/// [option]: ../../std/option/enum.Option.html</span>
<span class="doccomment">/// [make_mut]: struct.Arc.html#method.make_mut</span>
<span class="doccomment">/// [clone]: ../../std/clone/trait.Clone.html#tymethod.clone</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x = Arc::new(3);</span>
<span class="doccomment">/// *Arc::get_mut(&mut x).unwrap() = 4;</span>
<span class="doccomment">/// assert_eq!(*x, 4);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let _y = Arc::clone(&x);</span>
<span class="doccomment">/// assert!(Arc::get_mut(&mut x).is_none());</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_unique"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_mut</span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">Self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">this</span>.<span class="ident">is_unique</span>() {
<span class="comment">// This unsafety is ok because we're guaranteed that the pointer</span>
<span class="comment">// returned is the *only* pointer that will ever be returned to T. Our</span>
<span class="comment">// reference count is guaranteed to be 1 at this point, and we required</span>
<span class="comment">// the Arc itself to be `mut`, so we're returning the only possible</span>
<span class="comment">// reference to the inner data.</span>
<span class="kw">unsafe</span> {
<span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">this</span>.<span class="ident">ptr</span>.<span class="ident">as_mut</span>().<span class="ident">data</span>)
}
} <span class="kw">else</span> {
<span class="prelude-val">None</span>
}
}
<span class="doccomment">/// Determine whether this is the unique reference (including weak refs) to</span>
<span class="doccomment">/// the underlying data.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this requires locking the weak ref count.</span>
<span class="kw">fn</span> <span class="ident">is_unique</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="comment">// lock the weak pointer count if we appear to be the sole weak pointer</span>
<span class="comment">// holder.</span>
<span class="comment">//</span>
<span class="comment">// The acquire label here ensures a happens-before relationship with any</span>
<span class="comment">// writes to `strong` prior to decrements of the `weak` count (via drop,</span>
<span class="comment">// which uses Release).</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">compare_exchange</span>(<span class="number">1</span>, <span class="ident">usize</span>::<span class="ident">MAX</span>, <span class="ident">Acquire</span>, <span class="ident">Relaxed</span>).<span class="ident">is_ok</span>() {
<span class="comment">// Due to the previous acquire read, this will observe any writes to</span>
<span class="comment">// `strong` that were due to upgrading weak pointers; only strong</span>
<span class="comment">// clones remain, which require that the strong count is > 1 anyway.</span>
<span class="kw">let</span> <span class="ident">unique</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">strong</span>.<span class="ident">load</span>(<span class="ident">Relaxed</span>) <span class="op">==</span> <span class="number">1</span>;
<span class="comment">// The release write here synchronizes with a read in `downgrade`,</span>
<span class="comment">// effectively preventing the above read of `strong` from happening</span>
<span class="comment">// after the write.</span>
<span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">store</span>(<span class="number">1</span>, <span class="ident">Release</span>); <span class="comment">// release the lock</span>
<span class="ident">unique</span>
} <span class="kw">else</span> {
<span class="bool-val">false</span>
}
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="attribute">#[<span class="ident">may_dangle</span>]</span> <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Drops the `Arc`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This will decrement the strong reference count. If the strong reference</span>
<span class="doccomment">/// count reaches zero then the only other references (if any) are</span>
<span class="doccomment">/// [`Weak`][weak], so we `drop` the inner value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [weak]: struct.Weak.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// struct Foo;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// impl Drop for Foo {</span>
<span class="doccomment">/// fn drop(&mut self) {</span>
<span class="doccomment">/// println!("dropped!");</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let foo = Arc::new(Foo);</span>
<span class="doccomment">/// let foo2 = Arc::clone(&foo);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// drop(foo); // Doesn't print anything</span>
<span class="doccomment">/// drop(foo2); // Prints "dropped!"</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</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="comment">// Because `fetch_sub` is already atomic, we do not need to synchronize</span>
<span class="comment">// with other threads unless we are going to delete the object. This</span>
<span class="comment">// same logic applies to the below `fetch_sub` to the `weak` count.</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">strong</span>.<span class="ident">fetch_sub</span>(<span class="number">1</span>, <span class="ident">Release</span>) <span class="op">!=</span> <span class="number">1</span> {
<span class="kw">return</span>;
}
<span class="comment">// This fence is needed to prevent reordering of use of the data and</span>
<span class="comment">// deletion of the data. Because it is marked `Release`, the decreasing</span>
<span class="comment">// of the reference count synchronizes with this `Acquire` fence. This</span>
<span class="comment">// means that use of the data happens before decreasing the reference</span>
<span class="comment">// count, which happens before this fence, which happens before the</span>
<span class="comment">// deletion of the data.</span>
<span class="comment">//</span>
<span class="comment">// As explained in the [Boost documentation][1],</span>
<span class="comment">//</span>
<span class="comment">// > It is important to enforce any possible access to the object in one</span>
<span class="comment">// > thread (through an existing reference) to *happen before* deleting</span>
<span class="comment">// > the object in a different thread. This is achieved by a "release"</span>
<span class="comment">// > operation after dropping a reference (any access to the object</span>
<span class="comment">// > through this reference must obviously happened before), and an</span>
<span class="comment">// > "acquire" operation before deleting the object.</span>
<span class="comment">//</span>
<span class="comment">// In particular, while the contents of an Arc are usually immutable, it's</span>
<span class="comment">// possible to have interior writes to something like a Mutex<T>. Since a</span>
<span class="comment">// Mutex is not acquired when it is deleted, we can't rely on its</span>
<span class="comment">// synchronization logic to make writes in thread A visible to a destructor</span>
<span class="comment">// running in thread B.</span>
<span class="comment">//</span>
<span class="comment">// Also note that the Acquire fence here could probably be replaced with an</span>
<span class="comment">// Acquire load, which could improve performance in highly-contended</span>
<span class="comment">// situations. See [2].</span>
<span class="comment">//</span>
<span class="comment">// [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)</span>
<span class="comment">// [2]: (https://github.com/rust-lang/rust/pull/41714)</span>
<span class="ident">atomic</span>::<span class="ident">fence</span>(<span class="ident">Acquire</span>);
<span class="kw">unsafe</span> {
<span class="self">self</span>.<span class="ident">drop_slow</span>();
}
}
}
<span class="kw">impl</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">Any</span> <span class="op">+</span> <span class="ident">Send</span> <span class="op">+</span> <span class="ident">Sync</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rc_downcast"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"44608"</span>)]</span>
<span class="doccomment">/// Attempt to downcast the `Arc<Any + Send + Sync>` to a concrete type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// #![feature(rc_downcast)]</span>
<span class="doccomment">/// use std::any::Any;</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn print_if_string(value: Arc<Any + Send + Sync>) {</span>
<span class="doccomment">/// if let Ok(string) = value.downcast::<String>() {</span>
<span class="doccomment">/// println!("String ({}): {}", string.len(), string);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn main() {</span>
<span class="doccomment">/// let my_string = "Hello World".to_string();</span>
<span class="doccomment">/// print_if_string(Arc::new(my_string));</span>
<span class="doccomment">/// print_if_string(Arc::new(0i8));</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">downcast</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="self">Self</span><span class="op">></span>
<span class="kw">where</span>
<span class="ident">T</span>: <span class="ident">Any</span> <span class="op">+</span> <span class="ident">Send</span> <span class="op">+</span> <span class="ident">Sync</span> <span class="op">+</span> <span class="lifetime">'static</span>,
{
<span class="kw">if</span> (<span class="kw-2">*</span><span class="self">self</span>).<span class="ident">is</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() {
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">cast</span>::<span class="op"><</span><span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>();
<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="self">self</span>);
<span class="prelude-val">Ok</span>(<span class="ident">Arc</span> { <span class="ident">ptr</span>, <span class="ident">phantom</span>: <span class="ident">PhantomData</span> })
} <span class="kw">else</span> {
<span class="prelude-val">Err</span>(<span class="self">self</span>)
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Constructs a new `Weak<T>`, allocating memory for `T` without initializing</span>
<span class="doccomment">/// it. Calling [`upgrade`] on the return value always gives [`None`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`upgrade`]: struct.Weak.html#method.upgrade</span>
<span class="doccomment">/// [`None`]: ../../std/option/enum.Option.html#variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Weak;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let empty: Weak<i64> = Weak::new();</span>
<span class="doccomment">/// assert!(empty.upgrade().is_none());</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"downgraded_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.10.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-></span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">unsafe</span> {
<span class="ident">Weak</span> {
<span class="ident">ptr</span>: <span class="ident">Box</span>::<span class="ident">into_raw_non_null</span>(<span class="kw">box</span> <span class="ident">ArcInner</span> {
<span class="ident">strong</span>: <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">0</span>),
<span class="ident">weak</span>: <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">1</span>),
<span class="ident">data</span>: <span class="ident">uninitialized</span>(),
}),
}
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Attempts to upgrade the `Weak` pointer to an [`Arc`], extending</span>
<span class="doccomment">/// the lifetime of the value if successful.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns [`None`] if the value has since been dropped.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Arc`]: struct.Arc.html</span>
<span class="doccomment">/// [`None`]: ../../std/option/enum.Option.html#variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let weak_five = Arc::downgrade(&five);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let strong_five: Option<Arc<_>> = weak_five.upgrade();</span>
<span class="doccomment">/// assert!(strong_five.is_some());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Destroy all strong pointers.</span>
<span class="doccomment">/// drop(strong_five);</span>
<span class="doccomment">/// drop(five);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(weak_five.upgrade().is_none());</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">upgrade</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> {
<span class="comment">// We use a CAS loop to increment the strong count instead of a</span>
<span class="comment">// fetch_add because once the count hits 0 it must never be above 0.</span>
<span class="kw">let</span> <span class="ident">inner</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">inner</span>();
<span class="comment">// Relaxed load because any write of 0 that we can observe</span>
<span class="comment">// leaves the field in a permanently zero state (so a</span>
<span class="comment">// "stale" read of 0 is fine), and any other value is</span>
<span class="comment">// confirmed via the CAS below.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">n</span> <span class="op">=</span> <span class="ident">inner</span>.<span class="ident">strong</span>.<span class="ident">load</span>(<span class="ident">Relaxed</span>);
<span class="kw">loop</span> {
<span class="kw">if</span> <span class="ident">n</span> <span class="op">==</span> <span class="number">0</span> {
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
<span class="comment">// See comments in `Arc::clone` for why we do this (for `mem::forget`).</span>
<span class="kw">if</span> <span class="ident">n</span> <span class="op">></span> <span class="ident">MAX_REFCOUNT</span> {
<span class="kw">unsafe</span> {
<span class="ident">abort</span>();
}
}
<span class="comment">// Relaxed is valid for the same reason it is on Arc's Clone impl</span>
<span class="kw">match</span> <span class="ident">inner</span>.<span class="ident">strong</span>.<span class="ident">compare_exchange_weak</span>(<span class="ident">n</span>, <span class="ident">n</span> <span class="op">+</span> <span class="number">1</span>, <span class="ident">Relaxed</span>, <span class="ident">Relaxed</span>) {
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">Some</span>(<span class="ident">Arc</span> { <span class="ident">ptr</span>: <span class="self">self</span>.<span class="ident">ptr</span>, <span class="ident">phantom</span>: <span class="ident">PhantomData</span> }),
<span class="prelude-val">Err</span>(<span class="ident">old</span>) <span class="op">=></span> <span class="ident">n</span> <span class="op">=</span> <span class="ident">old</span>,
}
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">inner</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">ArcInner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// See comments above for why this is "safe"</span>
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">as_ref</span>() }
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Makes a clone of the `Weak` pointer that points to the same value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::{Arc, Weak};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let weak_five = Arc::downgrade(&Arc::new(5));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Weak::clone(&weak_five);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// See comments in Arc::clone() for why this is relaxed. This can use a</span>
<span class="comment">// fetch_add (ignoring the lock) because the weak count is only locked</span>
<span class="comment">// where are *no other* weak pointers in existence. (So we can't be</span>
<span class="comment">// running this code in that case).</span>
<span class="kw">let</span> <span class="ident">old_size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">fetch_add</span>(<span class="number">1</span>, <span class="ident">Relaxed</span>);
<span class="comment">// See comments in Arc::clone() for why we do this (for mem::forget).</span>
<span class="kw">if</span> <span class="ident">old_size</span> <span class="op">></span> <span class="ident">MAX_REFCOUNT</span> {
<span class="kw">unsafe</span> {
<span class="ident">abort</span>();
}
}
<span class="kw">return</span> <span class="ident">Weak</span> { <span class="ident">ptr</span>: <span class="self">self</span>.<span class="ident">ptr</span> };
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"downgraded_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.10.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Constructs a new `Weak<T>`, allocating memory for `T` without initializing</span>
<span class="doccomment">/// it. Calling [`upgrade`] on the return value always gives [`None`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`upgrade`]: struct.Weak.html#method.upgrade</span>
<span class="doccomment">/// [`None`]: ../../std/option/enum.Option.html#variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Weak;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let empty: Weak<i64> = Default::default();</span>
<span class="doccomment">/// assert!(empty.upgrade().is_none());</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-></span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">Weak</span>::<span class="ident">new</span>()
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"arc_weak"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">Weak</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Drops the `Weak` pointer.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::{Arc, Weak};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// struct Foo;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// impl Drop for Foo {</span>
<span class="doccomment">/// fn drop(&mut self) {</span>
<span class="doccomment">/// println!("dropped!");</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let foo = Arc::new(Foo);</span>
<span class="doccomment">/// let weak_foo = Arc::downgrade(&foo);</span>
<span class="doccomment">/// let other_weak_foo = Weak::clone(&weak_foo);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// drop(weak_foo); // Doesn't print anything</span>
<span class="doccomment">/// drop(foo); // Prints "dropped!"</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(other_weak_foo.upgrade().is_none());</span>
<span class="doccomment">/// ```</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="comment">// If we find out that we were the last weak pointer, then its time to</span>
<span class="comment">// deallocate the data entirely. See the discussion in Arc::drop() about</span>
<span class="comment">// the memory orderings</span>
<span class="comment">//</span>
<span class="comment">// It's not necessary to check for the locked state here, because the</span>
<span class="comment">// weak count can only be locked if there was precisely one weak ref,</span>
<span class="comment">// meaning that drop could only subsequently run ON that remaining weak</span>
<span class="comment">// ref, which can only happen after the lock is released.</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>().<span class="ident">weak</span>.<span class="ident">fetch_sub</span>(<span class="number">1</span>, <span class="ident">Release</span>) <span class="op">==</span> <span class="number">1</span> {
<span class="ident">atomic</span>::<span class="ident">fence</span>(<span class="ident">Acquire</span>);
<span class="kw">unsafe</span> {
<span class="ident">Global</span>.<span class="ident">dealloc</span>(<span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">cast</span>(), <span class="ident">Layout</span>::<span class="ident">for_value</span>(<span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">as_ref</span>()))
}
}
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">PartialEq</span><span class="op">></span> <span class="ident">PartialEq</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Equality for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Two `Arc`s are equal if their inner values are equal.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(five == Arc::new(5));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">eq</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw-2">*</span>(<span class="kw-2">*</span><span class="self">self</span>) <span class="op">==</span> <span class="kw-2">*</span>(<span class="kw-2">*</span><span class="ident">other</span>)
}
<span class="doccomment">/// Inequality for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Two `Arc`s are unequal if their inner values are unequal.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(five != Arc::new(6));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">ne</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw-2">*</span>(<span class="kw-2">*</span><span class="self">self</span>) <span class="op">!=</span> <span class="kw-2">*</span>(<span class="kw-2">*</span><span class="ident">other</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">PartialOrd</span><span class="op">></span> <span class="ident">PartialOrd</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Partial comparison for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The two are compared by calling `partial_cmp()` on their inner values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">/// use std::cmp::Ordering;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(Some(Ordering::Less), five.partial_cmp(&Arc::new(6)));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">partial_cmp</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Ordering</span><span class="op">></span> {
(<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">partial_cmp</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">other</span>)
}
<span class="doccomment">/// Less-than comparison for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The two are compared by calling `<` on their inner values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(five < Arc::new(6));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">lt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw-2">*</span>(<span class="kw-2">*</span><span class="self">self</span>) <span class="op"><</span> <span class="kw-2">*</span>(<span class="kw-2">*</span><span class="ident">other</span>)
}
<span class="doccomment">/// 'Less than or equal to' comparison for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The two are compared by calling `<=` on their inner values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(five <= Arc::new(5));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">le</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw-2">*</span>(<span class="kw-2">*</span><span class="self">self</span>) <span class="op"><=</span> <span class="kw-2">*</span>(<span class="kw-2">*</span><span class="ident">other</span>)
}
<span class="doccomment">/// Greater-than comparison for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The two are compared by calling `>` on their inner values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(five > Arc::new(4));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">gt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw-2">*</span>(<span class="kw-2">*</span><span class="self">self</span>) <span class="op">></span> <span class="kw-2">*</span>(<span class="kw-2">*</span><span class="ident">other</span>)
}
<span class="doccomment">/// 'Greater than or equal to' comparison for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The two are compared by calling `>=` on their inner values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(five >= Arc::new(5));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">ge</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw-2">*</span>(<span class="kw-2">*</span><span class="self">self</span>) <span class="op">>=</span> <span class="kw-2">*</span>(<span class="kw-2">*</span><span class="ident">other</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Ord</span><span class="op">></span> <span class="ident">Ord</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Comparison for two `Arc`s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The two are compared by calling `cmp()` on their inner values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">/// use std::cmp::Ordering;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let five = Arc::new(5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(Ordering::Less, five.cmp(&Arc::new(6)));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">cmp</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Ordering</span> {
(<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">cmp</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">other</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Eq</span><span class="op">></span> <span class="ident">Eq</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">fmt</span>::<span class="ident">Display</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></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="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">fmt</span>::<span class="ident">Display</span>::<span class="ident">fmt</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>, <span class="ident">f</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">fmt</span>::<span class="ident">Debug</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></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="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">fmt</span>::<span class="ident">Debug</span>::<span class="ident">fmt</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>, <span class="ident">f</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Pointer</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></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="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">fmt</span>::<span class="ident">Pointer</span>::<span class="ident">fmt</span>(<span class="kw-2">&</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span>), <span class="ident">f</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Default</span><span class="op">></span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Creates a new `Arc<T>`, with the `Default` value for `T`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::sync::Arc;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Arc<i32> = Default::default();</span>
<span class="doccomment">/// assert_eq!(*x, 0);</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">Default</span>::<span class="ident">default</span>())
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Hash</span><span class="op">></span> <span class="ident">Hash</span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">hash</span><span class="op"><</span><span class="ident">H</span>: <span class="ident">Hasher</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">state</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">H</span>) {
(<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">hash</span>(<span class="ident">state</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"from_for_ptrs"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.6.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">t</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">t</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"shared_from_slice"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="ident">Clone</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> [<span class="ident">T</span>]<span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">v</span>: <span class="kw-2">&</span>[<span class="ident">T</span>]) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="op"><</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">ArcFromSlice</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>::<span class="ident">from_slice</span>(<span class="ident">v</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"shared_from_slice"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">v</span>: <span class="kw-2">&</span><span class="ident">str</span>) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">arc</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span>::<span class="ident">from</span>(<span class="ident">v</span>.<span class="ident">as_bytes</span>());
<span class="kw">unsafe</span> { <span class="ident">Arc</span>::<span class="ident">from_raw</span>(<span class="ident">Arc</span>::<span class="ident">into_raw</span>(<span class="ident">arc</span>) <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">str</span>) }
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"shared_from_slice"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span> <span class="ident">From</span><span class="op"><</span><span class="ident">String</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">v</span>: <span class="ident">String</span>) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> {
<span class="ident">Arc</span>::<span class="ident">from</span>(<span class="kw-2">&</span><span class="ident">v</span>[..])
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"shared_from_slice"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">Box</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">v</span>: <span class="ident">Box</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">Arc</span>::<span class="ident">from_box</span>(<span class="ident">v</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"shared_from_slice"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="kw-2">mut</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">arc</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">copy_from_slice</span>(<span class="kw-2">&</span><span class="ident">v</span>);
<span class="comment">// Allow the Vec to free its memory, but not destroy its contents</span>
<span class="ident">v</span>.<span class="ident">set_len</span>(<span class="number">0</span>);
<span class="ident">arc</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="ident">std</span>::<span class="ident">boxed</span>::<span class="ident">Box</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">clone</span>::<span class="ident">Clone</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">mpsc</span>::<span class="ident">channel</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>::<span class="ident">drop</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ops</span>::<span class="ident">Drop</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">option</span>::<span class="prelude-ty">Option</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">option</span>::<span class="prelude-ty">Option</span>::{<span class="prelude-val">None</span>, <span class="prelude-val">Some</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">atomic</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">atomic</span>::<span class="ident">Ordering</span>::{<span class="ident">Acquire</span>, <span class="ident">SeqCst</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Mutex</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">convert</span>::<span class="ident">From</span>;
<span class="kw">use</span> <span class="kw">super</span>::{<span class="ident">Arc</span>, <span class="ident">Weak</span>};
<span class="kw">use</span> <span class="ident">vec</span>::<span class="ident">Vec</span>;
<span class="kw">struct</span> <span class="ident">Canary</span>(<span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>);
<span class="kw">impl</span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">Canary</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">unsafe</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="ident">Canary</span>(<span class="ident">c</span>) <span class="op">=></span> {
(<span class="kw-2">*</span><span class="ident">c</span>).<span class="ident">fetch_add</span>(<span class="number">1</span>, <span class="ident">SeqCst</span>);
}
}
}
}
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"emscripten"</span>, <span class="ident">ignore</span>)]</span>
<span class="kw">fn</span> <span class="ident">manually_share_arc</span>() {
<span class="kw">let</span> <span class="ident">v</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>, <span class="number">10</span>];
<span class="kw">let</span> <span class="ident">arc_v</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">v</span>);
<span class="kw">let</span> (<span class="ident">tx</span>, <span class="ident">rx</span>) <span class="op">=</span> <span class="ident">channel</span>();
<span class="kw">let</span> <span class="ident">_t</span> <span class="op">=</span> <span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
<span class="kw">let</span> <span class="ident">arc_v</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">i32</span><span class="op">>></span> <span class="op">=</span> <span class="ident">rx</span>.<span class="ident">recv</span>().<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="kw-2">*</span><span class="ident">arc_v</span>)[<span class="number">3</span>], <span class="number">4</span>);
});
<span class="ident">tx</span>.<span class="ident">send</span>(<span class="ident">arc_v</span>.<span class="ident">clone</span>()).<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="kw-2">*</span><span class="ident">arc_v</span>)[<span class="number">2</span>], <span class="number">3</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="kw-2">*</span><span class="ident">arc_v</span>)[<span class="number">4</span>], <span class="number">5</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_arc_get_mut</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">3</span>);
<span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span>).<span class="ident">unwrap</span>() <span class="op">=</span> <span class="number">4</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">x</span>, <span class="number">4</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">clone</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span>).<span class="ident">is_none</span>());
<span class="ident">drop</span>(<span class="ident">y</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span>).<span class="ident">is_some</span>());
<span class="kw">let</span> <span class="ident">_w</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">x</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span>).<span class="ident">is_none</span>());
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">try_unwrap</span>() {
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">3</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">try_unwrap</span>(<span class="ident">x</span>), <span class="prelude-val">Ok</span>(<span class="number">3</span>));
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">4</span>);
<span class="kw">let</span> <span class="ident">_y</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">clone</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">try_unwrap</span>(<span class="ident">x</span>), <span class="prelude-val">Err</span>(<span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">4</span>)));
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">5</span>);
<span class="kw">let</span> <span class="ident">_w</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">x</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">try_unwrap</span>(<span class="ident">x</span>), <span class="prelude-val">Ok</span>(<span class="number">5</span>));
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">into_from_raw</span>() {
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="kw">box</span> <span class="string">"hello"</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">clone</span>();
<span class="kw">let</span> <span class="ident">x_ptr</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">into_raw</span>(<span class="ident">x</span>);
<span class="ident">drop</span>(<span class="ident">y</span>);
<span class="kw">unsafe</span> {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">x_ptr</span>, <span class="string">"hello"</span>);
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from_raw</span>(<span class="ident">x_ptr</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">x</span>, <span class="string">"hello"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">try_unwrap</span>(<span class="ident">x</span>).<span class="ident">map</span>(<span class="op">|</span><span class="ident">x</span><span class="op">|</span> <span class="kw-2">*</span><span class="ident">x</span>), <span class="prelude-val">Ok</span>(<span class="string">"hello"</span>));
}
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_into_from_raw_unsized</span>() {
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>::<span class="ident">Display</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">string</span>::<span class="ident">ToString</span>;
<span class="kw">let</span> <span class="ident">arc</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="string">"foo"</span>);
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">into_raw</span>(<span class="ident">arc</span>.<span class="ident">clone</span>());
<span class="kw">let</span> <span class="ident">arc2</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">Arc</span>::<span class="ident">from_raw</span>(<span class="ident">ptr</span>) };
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw">unsafe</span> { <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">ptr</span> }, <span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">arc</span>, <span class="ident">arc2</span>);
<span class="kw">let</span> <span class="ident">arc</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">Display</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">123</span>);
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">into_raw</span>(<span class="ident">arc</span>.<span class="ident">clone</span>());
<span class="kw">let</span> <span class="ident">arc2</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">Arc</span>::<span class="ident">from_raw</span>(<span class="ident">ptr</span>) };
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw">unsafe</span> { <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">ptr</span> }.<span class="ident">to_string</span>(), <span class="string">"123"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">arc2</span>.<span class="ident">to_string</span>(), <span class="string">"123"</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_cowarc_clone_make_mut</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cow0</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">75</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cow1</span> <span class="op">=</span> <span class="ident">cow0</span>.<span class="ident">clone</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cow2</span> <span class="op">=</span> <span class="ident">cow1</span>.<span class="ident">clone</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow0</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow1</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow2</span>));
<span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow0</span>) <span class="op">+=</span> <span class="number">1</span>;
<span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow1</span>) <span class="op">+=</span> <span class="number">2</span>;
<span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow2</span>) <span class="op">+=</span> <span class="number">3</span>;
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">76</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">77</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">78</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow2</span>);
<span class="comment">// none should point to the same backing memory</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">cow0</span> <span class="op">!=</span> <span class="kw-2">*</span><span class="ident">cow1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">cow0</span> <span class="op">!=</span> <span class="kw-2">*</span><span class="ident">cow2</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">cow1</span> <span class="op">!=</span> <span class="kw-2">*</span><span class="ident">cow2</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_cowarc_clone_unique2</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cow0</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">75</span>);
<span class="kw">let</span> <span class="ident">cow1</span> <span class="op">=</span> <span class="ident">cow0</span>.<span class="ident">clone</span>();
<span class="kw">let</span> <span class="ident">cow2</span> <span class="op">=</span> <span class="ident">cow1</span>.<span class="ident">clone</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow2</span>);
<span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow0</span>) <span class="op">+=</span> <span class="number">1</span>;
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">76</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow2</span>);
<span class="comment">// cow1 and cow2 should share the same contents</span>
<span class="comment">// cow0 should have a unique reference</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">cow0</span> <span class="op">!=</span> <span class="kw-2">*</span><span class="ident">cow1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">cow0</span> <span class="op">!=</span> <span class="kw-2">*</span><span class="ident">cow2</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">cow1</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow2</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_cowarc_clone_weak</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cow0</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">75</span>);
<span class="kw">let</span> <span class="ident">cow1_weak</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">cow0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">75</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow1_weak</span>.<span class="ident">upgrade</span>().<span class="ident">unwrap</span>());
<span class="kw-2">*</span><span class="ident">Arc</span>::<span class="ident">make_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cow0</span>) <span class="op">+=</span> <span class="number">1</span>;
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">76</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">cow0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">cow1_weak</span>.<span class="ident">upgrade</span>().<span class="ident">is_none</span>());
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_live</span>() {
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">5</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">x</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">y</span>.<span class="ident">upgrade</span>().<span class="ident">is_some</span>());
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_dead</span>() {
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">5</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">x</span>);
<span class="ident">drop</span>(<span class="ident">x</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">y</span>.<span class="ident">upgrade</span>().<span class="ident">is_none</span>());
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">weak_self_cyclic</span>() {
<span class="kw">struct</span> <span class="ident">Cycle</span> {
<span class="ident">x</span>: <span class="ident">Mutex</span><span class="op"><</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Weak</span><span class="op"><</span><span class="ident">Cycle</span><span class="op">>></span><span class="op">></span>,
}
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">Cycle</span> { <span class="ident">x</span>: <span class="ident">Mutex</span>::<span class="ident">new</span>(<span class="prelude-val">None</span>) });
<span class="kw">let</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">a</span>.<span class="ident">clone</span>());
<span class="kw-2">*</span><span class="ident">a</span>.<span class="ident">x</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>() <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">b</span>);
<span class="comment">// hopefully we don't double-free (or leak)...</span>
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">drop_arc</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">canary</span> <span class="op">=</span> <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">0</span>);
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">Canary</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">canary</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>));
<span class="ident">drop</span>(<span class="ident">x</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">canary</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">==</span> <span class="number">1</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">drop_arc_weak</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">canary</span> <span class="op">=</span> <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">0</span>);
<span class="kw">let</span> <span class="ident">arc</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">Canary</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">canary</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>));
<span class="kw">let</span> <span class="ident">arc_weak</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">arc</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">canary</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">==</span> <span class="number">0</span>);
<span class="ident">drop</span>(<span class="ident">arc</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">canary</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="ident">drop</span>(<span class="ident">arc_weak</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_strong_count</span>() {
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="kw">let</span> <span class="ident">w</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">a</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="kw">let</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">w</span>.<span class="ident">upgrade</span>().<span class="ident">expect</span>(<span class="string">""</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">b</span>) <span class="op">==</span> <span class="number">2</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">2</span>);
<span class="ident">drop</span>(<span class="ident">w</span>);
<span class="ident">drop</span>(<span class="ident">a</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">b</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">b</span>.<span class="ident">clone</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">b</span>) <span class="op">==</span> <span class="number">2</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">c</span>) <span class="op">==</span> <span class="number">2</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_weak_count</span>() {
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">weak_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">0</span>);
<span class="kw">let</span> <span class="ident">w</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">a</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">weak_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">w</span>.<span class="ident">clone</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">weak_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">2</span>);
<span class="ident">drop</span>(<span class="ident">w</span>);
<span class="ident">drop</span>(<span class="ident">x</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">weak_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">0</span>);
<span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">a</span>.<span class="ident">clone</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">2</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">weak_count</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">==</span> <span class="number">0</span>);
<span class="kw">let</span> <span class="ident">d</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">c</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">weak_count</span>(<span class="kw-2">&</span><span class="ident">c</span>) <span class="op">==</span> <span class="number">1</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">strong_count</span>(<span class="kw-2">&</span><span class="ident">c</span>) <span class="op">==</span> <span class="number">2</span>);
<span class="ident">drop</span>(<span class="ident">a</span>);
<span class="ident">drop</span>(<span class="ident">c</span>);
<span class="ident">drop</span>(<span class="ident">d</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">show_arc</span>() {
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">5</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">a</span>), <span class="string">"5"</span>);
}
<span class="comment">// Make sure deriving works with Arc<T></span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Eq</span>, <span class="ident">Ord</span>, <span class="ident">PartialEq</span>, <span class="ident">PartialOrd</span>, <span class="ident">Clone</span>, <span class="ident">Debug</span>, <span class="ident">Default</span>)]</span>
<span class="kw">struct</span> <span class="ident">Foo</span> {
<span class="ident">inner</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">i32</span><span class="op">></span>,
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_unsized</span>() {
<span class="kw">let</span> <span class="ident">x</span>: <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">i32</span>]<span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>([<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">x</span>), <span class="string">"[1, 2, 3]"</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">downgrade</span>(<span class="kw-2">&</span><span class="ident">x</span>.<span class="ident">clone</span>());
<span class="ident">drop</span>(<span class="ident">x</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">y</span>.<span class="ident">upgrade</span>().<span class="ident">is_none</span>());
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_owned</span>() {
<span class="kw">let</span> <span class="ident">foo</span> <span class="op">=</span> <span class="number">123</span>;
<span class="kw">let</span> <span class="ident">foo_arc</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">foo</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="number">123</span> <span class="op">==</span> <span class="kw-2">*</span><span class="ident">foo_arc</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_new_weak</span>() {
<span class="kw">let</span> <span class="ident">foo</span>: <span class="ident">Weak</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> <span class="op">=</span> <span class="ident">Weak</span>::<span class="ident">new</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">foo</span>.<span class="ident">upgrade</span>().<span class="ident">is_none</span>());
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_ptr_eq</span>() {
<span class="kw">let</span> <span class="ident">five</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">5</span>);
<span class="kw">let</span> <span class="ident">same_five</span> <span class="op">=</span> <span class="ident">five</span>.<span class="ident">clone</span>();
<span class="kw">let</span> <span class="ident">other_five</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="number">5</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">Arc</span>::<span class="ident">ptr_eq</span>(<span class="kw-2">&</span><span class="ident">five</span>, <span class="kw-2">&</span><span class="ident">same_five</span>));
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">Arc</span>::<span class="ident">ptr_eq</span>(<span class="kw-2">&</span><span class="ident">five</span>, <span class="kw-2">&</span><span class="ident">other_five</span>));
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"emscripten"</span>, <span class="ident">ignore</span>)]</span>
<span class="kw">fn</span> <span class="ident">test_weak_count_locked</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">atomic</span>::<span class="ident">AtomicBool</span>::<span class="ident">new</span>(<span class="bool-val">false</span>));
<span class="kw">let</span> <span class="ident">a2</span> <span class="op">=</span> <span class="ident">a</span>.<span class="ident">clone</span>();
<span class="kw">let</span> <span class="ident">t</span> <span class="op">=</span> <span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
<span class="kw">for</span> <span class="ident">_i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="number">1000000</span> {
<span class="ident">Arc</span>::<span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">a</span>);
}
<span class="ident">a</span>.<span class="ident">store</span>(<span class="bool-val">true</span>, <span class="ident">SeqCst</span>);
});
<span class="kw">while</span> <span class="op">!</span><span class="ident">a2</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) {
<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">weak_count</span>(<span class="kw-2">&</span><span class="ident">a2</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">n</span> <span class="op"><</span> <span class="number">2</span>, <span class="string">"bad weak count: {}"</span>, <span class="ident">n</span>);
}
<span class="ident">t</span>.<span class="ident">join</span>().<span class="ident">unwrap</span>();
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_str</span>() {
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">r</span>[..], <span class="string">"foo"</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_copy_from_slice</span>() {
<span class="kw">let</span> <span class="ident">s</span>: <span class="kw-2">&</span>[<span class="ident">u32</span>] <span class="op">=</span> <span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>];
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">u32</span>]<span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">s</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">r</span>[..], [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_clone_from_slice</span>() {
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>, <span class="ident">Eq</span>, <span class="ident">PartialEq</span>)]</span>
<span class="kw">struct</span> <span class="ident">X</span>(<span class="ident">u32</span>);
<span class="kw">let</span> <span class="ident">s</span>: <span class="kw-2">&</span>[<span class="ident">X</span>] <span class="op">=</span> <span class="kw-2">&</span>[<span class="ident">X</span>(<span class="number">1</span>), <span class="ident">X</span>(<span class="number">2</span>), <span class="ident">X</span>(<span class="number">3</span>)];
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">X</span>]<span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">s</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">r</span>[..], <span class="ident">s</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="attribute">#[<span class="ident">should_panic</span>]</span>
<span class="kw">fn</span> <span class="ident">test_clone_from_slice_panic</span>() {
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">string</span>::{<span class="ident">String</span>, <span class="ident">ToString</span>};
<span class="kw">struct</span> <span class="ident">Fail</span>(<span class="ident">u32</span>, <span class="ident">String</span>);
<span class="kw">impl</span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">Fail</span> {
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Fail</span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="number">0</span> <span class="op">==</span> <span class="number">2</span> {
<span class="macro">panic</span><span class="macro">!</span>();
}
<span class="ident">Fail</span>(<span class="self">self</span>.<span class="number">0</span>, <span class="self">self</span>.<span class="number">1</span>.<span class="ident">clone</span>())
}
}
<span class="kw">let</span> <span class="ident">s</span>: <span class="kw-2">&</span>[<span class="ident">Fail</span>] <span class="op">=</span> <span class="kw-2">&</span>[
<span class="ident">Fail</span>(<span class="number">0</span>, <span class="string">"foo"</span>.<span class="ident">to_string</span>()),
<span class="ident">Fail</span>(<span class="number">1</span>, <span class="string">"bar"</span>.<span class="ident">to_string</span>()),
<span class="ident">Fail</span>(<span class="number">2</span>, <span class="string">"baz"</span>.<span class="ident">to_string</span>()),
];
<span class="comment">// Should panic, but not cause memory corruption</span>
<span class="kw">let</span> <span class="ident">_r</span>: <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">Fail</span>]<span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">s</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_box</span>() {
<span class="kw">let</span> <span class="ident">b</span>: <span class="ident">Box</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="kw">box</span> <span class="number">123</span>;
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">b</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">r</span>, <span class="number">123</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_box_str</span>() {
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">string</span>::<span class="ident">String</span>;
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">String</span>::<span class="ident">from</span>(<span class="string">"foo"</span>).<span class="ident">into_boxed_str</span>();
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">s</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">r</span>[..], <span class="string">"foo"</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_box_slice</span>() {
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>].<span class="ident">into_boxed_slice</span>();
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">u32</span>]<span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">s</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">r</span>[..], [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_box_trait</span>() {
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>::<span class="ident">Display</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">string</span>::<span class="ident">ToString</span>;
<span class="kw">let</span> <span class="ident">b</span>: <span class="ident">Box</span><span class="op"><</span><span class="ident">Display</span><span class="op">></span> <span class="op">=</span> <span class="kw">box</span> <span class="number">123</span>;
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">Display</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">b</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">to_string</span>(), <span class="string">"123"</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_box_trait_zero_sized</span>() {
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>::<span class="ident">Debug</span>;
<span class="kw">let</span> <span class="ident">b</span>: <span class="ident">Box</span><span class="op"><</span><span class="ident">Debug</span><span class="op">></span> <span class="op">=</span> <span class="kw">box</span> ();
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">Debug</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">b</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">r</span>), <span class="string">"()"</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_from_vec</span>() {
<span class="kw">let</span> <span class="ident">v</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>];
<span class="kw">let</span> <span class="ident">r</span>: <span class="ident">Arc</span><span class="op"><</span>[<span class="ident">u32</span>]<span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">from</span>(<span class="ident">v</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">r</span>[..], [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_downcast</span>() {
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span>;
<span class="kw">let</span> <span class="ident">r1</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">Any</span> <span class="op">+</span> <span class="ident">Send</span> <span class="op">+</span> <span class="ident">Sync</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">i32</span>::<span class="ident">max_value</span>());
<span class="kw">let</span> <span class="ident">r2</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">Any</span> <span class="op">+</span> <span class="ident">Send</span> <span class="op">+</span> <span class="ident">Sync</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="string">"abc"</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">r1</span>.<span class="ident">clone</span>().<span class="ident">downcast</span>::<span class="op"><</span><span class="ident">u32</span><span class="op">></span>().<span class="ident">is_err</span>());
<span class="kw">let</span> <span class="ident">r1i32</span> <span class="op">=</span> <span class="ident">r1</span>.<span class="ident">downcast</span>::<span class="op"><</span><span class="ident">i32</span><span class="op">></span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">r1i32</span>.<span class="ident">is_ok</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">r1i32</span>.<span class="ident">unwrap</span>(), <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">i32</span>::<span class="ident">max_value</span>()));
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">r2</span>.<span class="ident">clone</span>().<span class="ident">downcast</span>::<span class="op"><</span><span class="ident">i32</span><span class="op">></span>().<span class="ident">is_err</span>());
<span class="kw">let</span> <span class="ident">r2str</span> <span class="op">=</span> <span class="ident">r2</span>.<span class="ident">downcast</span>::<span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'static</span> <span class="ident">str</span><span class="op">></span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">r2str</span>.<span class="ident">is_ok</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">r2str</span>.<span class="ident">unwrap</span>(), <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="string">"abc"</span>));
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">borrow</span>::<span class="ident">Borrow</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">borrow</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> {
<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"1.5.0"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"smart_ptr_as_ref"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">AsRef</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">as_ref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> {
<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>
}
}
</pre>
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