std::sync::Arc - Rust
Description: API documentation for the Rust `Arc` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, Arc

# 1.0.0[−][src]Struct std::sync::Arc

    #[lang = "arc"]
    pub struct Arc<T> where
        T: ?Sized,  { /* fields omitted */ }

A thread-safe reference-counting pointer. 'Arc' stands for 'Atomically Reference Counted'.

The type `Arc<T>` provides shared ownership of a value of type `T`, allocated in the heap. Invoking `clone` on `Arc` produces a new `Arc` instance, which points to the same allocation on the heap as the source `Arc`, while increasing a reference count. When the last `Arc` pointer to a given allocation is destroyed, the value stored in that allocation (often referred to as "inner value") is also dropped.

Shared references in Rust disallow mutation by default, and `Arc` is no exception: you cannot generally obtain a mutable reference to something inside an `Arc`. If you need to mutate through an `Arc`, use `Mutex`, `RwLock`, or one of the `Atomic` types.

## Thread Safety

Unlike `Rc<T>`, `Arc<T>` uses atomic operations for its reference counting. This means that it is thread-safe. The disadvantage is that atomic operations are more expensive than ordinary memory accesses. If you are not sharing reference-counted allocations between threads, consider using `Rc<T>` for lower overhead. `Rc<T>` is a safe default, because the compiler will catch any attempt to send an `Rc<T>` between threads. However, a library might choose `Arc<T>` in order to give library consumers more flexibility.

`Arc<T>` will implement `Send` and `Sync` as long as the `T` implements `Send` and `Sync`. Why can't you put a non-thread-safe type `T` in an `Arc<T>` to make it thread-safe? This may be a bit counter-intuitive at first: after all, isn't the point of `Arc<T>` thread safety? The key is this: `Arc<T>` makes it thread safe to have multiple ownership of the same data, but it doesn't add thread safety to its data. Consider `Arc<``RefCell<T>``>`. `RefCell<T>` isn't `Sync`, and if `Arc<T>` was always `Send`, `Arc<``RefCell<T>``>` would be as well. But then we'd have a problem: `RefCell<T>` is not thread safe; it keeps track of the borrowing count using non-atomic operations.

In the end, this means that you may need to pair `Arc<T>` with some sort of `std::sync` type, usually `Mutex<T>`.

## Breaking cycles with `Weak`

The `downgrade` method can be used to create a non-owning `Weak` pointer. A `Weak` pointer can be `upgrade`d to an `Arc`, but this will return `None` if the value stored in the allocation has already been dropped. In other words, `Weak` pointers do not keep the value inside the allocation alive; however, they do keep the allocation (the backing store for the value) alive.

A cycle between `Arc` pointers will never be deallocated. For this reason, `Weak` is used to break cycles. For example, a tree could have strong `Arc` pointers from parent nodes to children, and `Weak` pointers from children back to their parents.

# Cloning references

Creating a new reference from an existing reference counted pointer is done using the `Clone` trait implemented for `Arc<T>` and `Weak<T>`.

    use std::sync::Arc;
    let foo = Arc::new(vec![1.0, 2.0, 3.0]);
    // The two syntaxes below are equivalent.
    let a = foo.clone();
    let b = Arc::clone(&foo);
    // a, b, and foo are all Arcs that point to the same memory locationRun

## `Deref` behavior

`Arc<T>` automatically dereferences to `T` (via the `Deref` trait), so you can call `T`'s methods on a value of type `Arc<T>`. To avoid name clashes with `T`'s methods, the methods of `Arc<T>` itself are associated functions, called using function-like syntax:

    use std::sync::Arc;
    let my_arc = Arc::new(());

    Arc::downgrade(&my_arc);Run

`Weak<T>` does not auto-dereference to `T`, because the inner value may have already been dropped.

# Examples

Sharing some immutable data between threads:

    use std::sync::Arc;
    use std::thread;

    let five = Arc::new(5);

    for _ in 0..10 {
        let five = Arc::clone(&five);

        thread::spawn(move || {
            println!("{:?}", five);
        });
    }Run

Sharing a mutable `AtomicUsize`:

    use std::sync::Arc;
    use std::sync::atomic::{AtomicUsize, Ordering};
    use std::thread;

    let val = Arc::new(AtomicUsize::new(5));

    for _ in 0..10 {
        let val = Arc::clone(&val);

        thread::spawn(move || {
            let v = val.fetch_add(1, Ordering::SeqCst);
            println!("{:?}", v);
        });
    }Run

See the `rc` documentation for more examples of reference counting in general.

## Methods

### `impl<T> Arc<T>`[src]

#### `pub fn new(data: T) -> Arc<T>`[src]

Constructs a new `Arc<T>`.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);Run

#### `pub fn new_uninit() -> Arc<MaybeUninit<T>>`[src]

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Constructs a new `Arc` with uninitialized contents.

# Examples

    #![feature(new_uninit)]
    #![feature(get_mut_unchecked)]

    use std::sync::Arc;

    let mut five = Arc::<u32>::new_uninit();

    let five = unsafe {
        // Deferred initialization:
        Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);

        five.assume_init()
    };

    assert_eq!(*five, 5)Run

####
ⓘImportant traits for Pin<P>

### Important traits for Pin<P>

`impl<P> Future for Pin<P> where
P: Unpin + DerefMut,
<P as Deref>::Target: Future, type Output = <<P as Deref>::Target as Future>::Output;`
`pub fn pin(data: T) -> Pin<Arc<T>>`1.33.0[src]

Constructs a new `Pin<Arc<T>>`. If `T` does not implement `Unpin`, then `data` will be pinned in memory and unable to be moved.

#### `pub fn try_unwrap(this: Arc<T>) -> Result<T, Arc<T>>`1.4.0[src]

Returns the inner value, if the `Arc` has exactly one strong reference.

Otherwise, an `Err` is returned with the same `Arc` that was passed in.

This will succeed even if there are outstanding weak references.

# Examples

    use std::sync::Arc;

    let x = Arc::new(3);
    assert_eq!(Arc::try_unwrap(x), Ok(3));

    let x = Arc::new(4);
    let _y = Arc::clone(&x);
    assert_eq!(*Arc::try_unwrap(x).unwrap_err(), 4);Run

### `impl<T> Arc<[T]>`[src]

#### `pub fn new_uninit_slice(len: usize) -> Arc<[MaybeUninit<T>]>`[src]

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Constructs a new reference-counted slice with uninitialized contents.

# Examples

    #![feature(new_uninit)]
    #![feature(get_mut_unchecked)]

    use std::sync::Arc;

    let mut values = Arc::<[u32]>::new_uninit_slice(3);

    let values = unsafe {
        // Deferred initialization:
        Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
        Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
        Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);

        values.assume_init()
    };

    assert_eq!(*values, [1, 2, 3])Run

### `impl<T> Arc<MaybeUninit<T>>`[src]

#### `pub unsafe fn assume_init(self) -> Arc<T>`[src]

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Converts to `Arc<T>`.

# Safety

As with `MaybeUninit::assume_init`, it is up to the caller to guarantee that the inner value really is in an initialized state. Calling this when the content is not yet fully initialized causes immediate undefined behavior.

# Examples

    #![feature(new_uninit)]
    #![feature(get_mut_unchecked)]

    use std::sync::Arc;

    let mut five = Arc::<u32>::new_uninit();

    let five = unsafe {
        // Deferred initialization:
        Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);

        five.assume_init()
    };

    assert_eq!(*five, 5)Run

### `impl<T> Arc<[MaybeUninit<T>]>`[src]

#### `pub unsafe fn assume_init(self) -> Arc<[T]>`[src]

🔬 This is a nightly-only experimental API. (`new_uninit` #63291)

Converts to `Arc<[T]>`.

# Safety

As with `MaybeUninit::assume_init`, it is up to the caller to guarantee that the inner value really is in an initialized state. Calling this when the content is not yet fully initialized causes immediate undefined behavior.

# Examples

    #![feature(new_uninit)]
    #![feature(get_mut_unchecked)]

    use std::sync::Arc;

    let mut values = Arc::<[u32]>::new_uninit_slice(3);

    let values = unsafe {
        // Deferred initialization:
        Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
        Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
        Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);

        values.assume_init()
    };

    assert_eq!(*values, [1, 2, 3])Run

### `impl<T> Arc<T> where
T: ?Sized,` [src]

#### `pub fn into_raw(this: Arc<T>) -> *const T`1.17.0[src]

Consumes the `Arc`, returning the wrapped pointer.

To avoid a memory leak the pointer must be converted back to an `Arc` using `Arc::from_raw`.

# Examples

    use std::sync::Arc;

    let x = Arc::new("hello".to_owned());
    let x_ptr = Arc::into_raw(x);
    assert_eq!(unsafe { &*x_ptr }, "hello");Run

#### `pub unsafe fn from_raw(ptr: *const T) -> Arc<T>`1.17.0[src]

Constructs an `Arc` from a raw pointer.

The raw pointer must have been previously returned by a call to a `Arc::into_raw`.

This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.

# Examples

    use std::sync::Arc;

    let x = Arc::new("hello".to_owned());
    let x_ptr = Arc::into_raw(x);

    unsafe {
        // Convert back to an `Arc` to prevent leak.
        let x = Arc::from_raw(x_ptr);
        assert_eq!(&*x, "hello");

        // Further calls to `Arc::from_raw(x_ptr)` would be memory-unsafe.
    }

    // The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!Run

#### `pub fn into_raw_non_null(this: Arc<T>) -> NonNull<T>`[src]

🔬 This is a nightly-only experimental API. (`rc_into_raw_non_null` #47336)

Consumes the `Arc`, returning the wrapped pointer as `NonNull<T>`.

# Examples

    #![feature(rc_into_raw_non_null)]

    use std::sync::Arc;

    let x = Arc::new("hello".to_owned());
    let ptr = Arc::into_raw_non_null(x);
    let deref = unsafe { ptr.as_ref() };
    assert_eq!(deref, "hello");Run

#### `pub fn downgrade(this: &Arc<T>) -> Weak<T>`1.4.0[src]

Creates a new `Weak` pointer to this allocation.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    let weak_five = Arc::downgrade(&five);Run

#### `pub fn weak_count(this: &Arc<T>) -> usize`1.15.0[src]

Gets the number of `Weak` pointers to this allocation.

# Safety

This method by itself is safe, but using it correctly requires extra care. Another thread can change the weak count at any time, including potentially between calling this method and acting on the result.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);
    let _weak_five = Arc::downgrade(&five);

    // This assertion is deterministic because we haven't shared
    // the `Arc` or `Weak` between threads.
    assert_eq!(1, Arc::weak_count(&five));Run

#### `pub fn strong_count(this: &Arc<T>) -> usize`1.15.0[src]

Gets the number of strong (`Arc`) pointers to this allocation.

# Safety

This method by itself is safe, but using it correctly requires extra care. Another thread can change the strong count at any time, including potentially between calling this method and acting on the result.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);
    let _also_five = Arc::clone(&five);

    // This assertion is deterministic because we haven't shared
    // the `Arc` between threads.
    assert_eq!(2, Arc::strong_count(&five));Run

#### `pub fn ptr_eq(this: &Arc<T>, other: &Arc<T>) -> bool`1.17.0[src]

Returns `true` if the two `Arc`s point to the same allocation (in a vein similar to `ptr::eq`).

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);
    let same_five = Arc::clone(&five);
    let other_five = Arc::new(5);

    assert!(Arc::ptr_eq(&five, &same_five));
    assert!(!Arc::ptr_eq(&five, &other_five));Run

### `impl<T> Arc<T> where
T: Clone,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`pub fn make_mut(this: &mut Arc<T>) -> &mut T`1.4.0[src]

Makes a mutable reference into the given `Arc`.

If there are other `Arc` or `Weak` pointers to the same allocation, then `make_mut` will create a new allocation and invoke `clone` on the inner value to ensure unique ownership. This is also referred to as clone-on-write.

Note that this differs from the behavior of `Rc::make_mut` which disassociates any remaining `Weak` pointers.

See also `get_mut`, which will fail rather than cloning.

# Examples

    use std::sync::Arc;

    let mut data = Arc::new(5);

    *Arc::make_mut(&mut data) += 1;         // Won't clone anything
    let mut other_data = Arc::clone(&data); // Won't clone inner data
    *Arc::make_mut(&mut data) += 1;         // Clones inner data
    *Arc::make_mut(&mut data) += 1;         // Won't clone anything
    *Arc::make_mut(&mut other_data) *= 2;   // Won't clone anything

    // Now `data` and `other_data` point to different allocations.
    assert_eq!(*data, 8);
    assert_eq!(*other_data, 12);Run

### `impl<T> Arc<T> where
T: ?Sized,` [src]

#### `pub fn get_mut(this: &mut Arc<T>) -> Option<&mut T>`1.4.0[src]

Returns a mutable reference into the given `Arc`, if there are no other `Arc` or `Weak` pointers to the same allocation.

Returns `None` otherwise, because it is not safe to mutate a shared value.

See also `make_mut`, which will `clone` the inner value when there are other pointers.

# Examples

    use std::sync::Arc;

    let mut x = Arc::new(3);
    *Arc::get_mut(&mut x).unwrap() = 4;
    assert_eq!(*x, 4);

    let _y = Arc::clone(&x);
    assert!(Arc::get_mut(&mut x).is_none());Run

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`pub unsafe fn get_mut_unchecked(this: &mut Arc<T>) -> &mut T`[src]

🔬 This is a nightly-only experimental API. (`get_mut_unchecked` #63292)

Returns a mutable reference into the given `Arc`, without any check.

See also `get_mut`, which is safe and does appropriate checks.

# Safety

Any other `Arc` or `Weak` pointers to the same allocation must not be dereferenced for the duration of the returned borrow. This is trivially the case if no such pointers exist, for example immediately after `Arc::new`.

# Examples

    #![feature(get_mut_unchecked)]

    use std::sync::Arc;

    let mut x = Arc::new(String::new());
    unsafe {
        Arc::get_mut_unchecked(&mut x).push_str("foo")
    }
    assert_eq!(*x, "foo");Run

### `impl Arc<dyn Any + 'static + Send + Sync>`[src]

#### `pub fn downcast<T>(self) -> Result<Arc<T>, Arc<dyn Any + 'static + Send + Sync>> where
T: Any + Send + Sync + 'static,` 1.29.0[src]

Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.

# Examples

    use std::any::Any;
    use std::sync::Arc;

    fn print_if_string(value: Arc<dyn Any + Send + Sync>) {
        if let Ok(string) = value.downcast::<String>() {
            println!("String ({}): {}", string.len(), string);
        }
    }

    let my_string = "Hello World".to_string();
    print_if_string(Arc::new(my_string));
    print_if_string(Arc::new(0i8));Run

## Trait Implementations

### `impl<T> AsRef<T> for Arc<T> where
T: ?Sized,` 1.5.0[src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn as_ref(&self) -> &T`[src]

Performs the conversion.

### `impl<T> Ord for Arc<T> where
T: Ord + ?Sized,` [src]

#### `fn cmp(&self, other: &Arc<T>) -> Ordering`[src]

Comparison for two `Arc`s.

The two are compared by calling `cmp()` on their inner values.

# Examples

    use std::sync::Arc;
    use std::cmp::Ordering;

    let five = Arc::new(5);

    assert_eq!(Ordering::Less, five.cmp(&Arc::new(6)));Run

#### `fn max(self, other: Self) -> Self`1.21.0[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self`1.21.0[src]

Compares and returns the minimum of two values. Read more

#### `fn clamp(self, min: Self, max: Self) -> Self`[src]

🔬 This is a nightly-only experimental API. (`clamp` #44095)

Restrict a value to a certain interval. Read more

### `impl<T, U> DispatchFromDyn<Arc<U>> for Arc<T> where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<T> Borrow<T> for Arc<T> where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl From<String> for Arc<str>`1.21.0[src]

#### `fn from(v: String) -> Arc<str>`[src]

Performs the conversion.

### `impl<T> From<Vec<T>> for Arc<[T]>`1.21.0[src]

#### `fn from(v: Vec<T>) -> Arc<[T]>`[src]

Performs the conversion.

### `impl<'_, T> From<&'_ [T]> for Arc<[T]> where
T: Clone,` 1.21.0[src]

#### `fn from(v: &[T]) -> Arc<[T]>`[src]

Performs the conversion.

### `impl<T> From<Box<T>> for Arc<T> where
T: ?Sized,` 1.21.0[src]

#### `fn from(v: Box<T>) -> Arc<T>`[src]

Performs the conversion.

### `impl<'_> From<&'_ str> for Arc<str>`1.21.0[src]

#### `fn from(v: &str) -> Arc<str>`[src]

Performs the conversion.

### `impl<T> From<T> for Arc<T>`1.6.0[src]

#### `fn from(t: T) -> Arc<T>`[src]

Performs the conversion.

### `impl<T> Deref for Arc<T> where
T: ?Sized,` [src]

#### `type Target = T`

The resulting type after dereferencing.

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn deref(&self) -> &T`[src]

Dereferences the value.

### `impl<T> Pointer for Arc<T> where
T: ?Sized,` [src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`[src]

Formats the value using the given formatter.

### `impl<T> Drop for Arc<T> where
T: ?Sized,` [src]

#### `fn drop(&mut self)`[src]

Drops the `Arc`.

This will decrement the strong reference count. If the strong reference count reaches zero then the only other references (if any) are `Weak`, so we `drop` the inner value.

# Examples

    use std::sync::Arc;

    struct Foo;

    impl Drop for Foo {
        fn drop(&mut self) {
            println!("dropped!");
        }
    }

    let foo  = Arc::new(Foo);
    let foo2 = Arc::clone(&foo);

    drop(foo);    // Doesn't print anything
    drop(foo2);   // Prints "dropped!"Run

### `impl<T> PartialEq<Arc<T>> for Arc<T> where
T: PartialEq<T> + ?Sized,` [src]

#### `fn eq(&self, other: &Arc<T>) -> bool`[src]

Equality for two `Arc`s.

Two `Arc`s are equal if their inner values are equal, even if they are stored in different allocation.

If `T` also implements `Eq` (implying reflexivity of equality), two `Arc`s that point to the same allocation are always equal.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    assert!(five == Arc::new(5));Run

#### `fn ne(&self, other: &Arc<T>) -> bool`[src]

Inequality for two `Arc`s.

Two `Arc`s are unequal if their inner values are unequal.

If `T` also implements `Eq` (implying reflexivity of equality), two `Arc`s that point to the same value are never unequal.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    assert!(five != Arc::new(6));Run

### `impl<T> Default for Arc<T> where
T: Default,` [src]

#### `fn default() -> Arc<T>`[src]

Creates a new `Arc<T>`, with the `Default` value for `T`.

# Examples

    use std::sync::Arc;

    let x: Arc<i32> = Default::default();
    assert_eq!(*x, 0);Run

### `impl<T> PartialOrd<Arc<T>> for Arc<T> where
T: PartialOrd<T> + ?Sized,` [src]

#### `fn partial_cmp(&self, other: &Arc<T>) -> Option<Ordering>`[src]

Partial comparison for two `Arc`s.

The two are compared by calling `partial_cmp()` on their inner values.

# Examples

    use std::sync::Arc;
    use std::cmp::Ordering;

    let five = Arc::new(5);

    assert_eq!(Some(Ordering::Less), five.partial_cmp(&Arc::new(6)));Run

#### `fn lt(&self, other: &Arc<T>) -> bool`[src]

Less-than comparison for two `Arc`s.

The two are compared by calling `<` on their inner values.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    assert!(five < Arc::new(6));Run

#### `fn le(&self, other: &Arc<T>) -> bool`[src]

'Less than or equal to' comparison for two `Arc`s.

The two are compared by calling `<=` on their inner values.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    assert!(five <= Arc::new(5));Run

#### `fn gt(&self, other: &Arc<T>) -> bool`[src]

Greater-than comparison for two `Arc`s.

The two are compared by calling `>` on their inner values.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    assert!(five > Arc::new(4));Run

#### `fn ge(&self, other: &Arc<T>) -> bool`[src]

'Greater than or equal to' comparison for two `Arc`s.

The two are compared by calling `>=` on their inner values.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    assert!(five >= Arc::new(5));Run

### `impl<T> Unpin for Arc<T> where
T: ?Sized,` 1.33.0[src]

### `impl<T, U> CoerceUnsized<Arc<U>> for Arc<T> where
T: Unsize<U> + ?Sized,
U: ?Sized,` [src]

### `impl<T> Send for Arc<T> where
T: Send + Sync + ?Sized,` [src]

### `impl<T> Eq for Arc<T> where
T: Eq + ?Sized,` [src]

### `impl<T> Hash for Arc<T> where
T: Hash + ?Sized,` [src]

#### `fn hash<H>(&self, state: &mut H) where
H: Hasher,` [src]

Feeds this value into the given [`Hasher`]. Read more

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,` 1.3.0[src]

Feeds a slice of this type into the given [`Hasher`]. Read more

### `impl<const N: usize, T> TryFrom<Arc<[T]>> for Arc<[T; N]> where
[T; N]: LengthAtMost32,` [src]

#### `type Error = Arc<[T]>`

The type returned in the event of a conversion error.

#### `fn try_from(
boxed_slice: Arc<[T]>
) -> Result<Arc<[T; N]>, <Arc<[T; N]> as TryFrom<Arc<[T]>>>::Error>`[src]

Performs the conversion.

### `impl<T> Clone for Arc<T> where
T: ?Sized,` [src]

#### `fn clone(&self) -> Arc<T>`[src]

Makes a clone of the `Arc` pointer.

This creates another pointer to the same allocation, increasing the strong reference count.

# Examples

    use std::sync::Arc;

    let five = Arc::new(5);

    let _ = Arc::clone(&five);Run

#### `fn clone_from(&mut self, source: &Self)`[src]

Performs copy-assignment from `source`. Read more

### `impl<T> Display for Arc<T> where
T: Display + ?Sized,` [src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`[src]

Formats the value using the given formatter. Read more

### `impl<T> Debug for Arc<T> where
T: Debug + ?Sized,` [src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`[src]

Formats the value using the given formatter. Read more

### `impl<T> Sync for Arc<T> where
T: Send + Sync + ?Sized,` [src]

### `impl<T> FromIterator<T> for Arc<[T]>`1.37.0[src]

#### `fn from_iter<I>(iter: I) -> Arc<[T]> where
I: IntoIterator<Item = T>,` [src]

Takes each element in the `Iterator` and collects it into an `Arc<[T]>`.

# Performance characteristics

## The general case

In the general case, collecting into `Arc<[T]>` is done by first collecting into a `Vec<T>`. That is, when writing the following:

    let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0).collect();Run

this behaves as if we wrote:

    let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0)
        .collect::<Vec<_>>() // The first set of allocations happens here.
        .into(); // A second allocation for `Arc<[T]>` happens here.Run

This will allocate as many times as needed for constructing the `Vec<T>` and then it will allocate once for turning the `Vec<T>` into the `Arc<[T]>`.

## Iterators of known length

When your `Iterator` implements `TrustedLen` and is of an exact size, a single allocation will be made for the `Arc<[T]>`. For example:

    let evens: Arc<[u8]> = (0..10).collect(); // Just a single allocation happens here.Run

### `impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Arc<T>`1.9.0[src]

### `impl From<CString> for Arc<CStr>`1.24.0[src]

#### `fn from(s: CString) -> Arc<CStr>`[src]

Converts a `CString` into a `Arc``<CStr>` without copying or allocating.

### `impl<'_> From<&'_ CStr> for Arc<CStr>`1.24.0[src]

#### `fn from(s: &CStr) -> Arc<CStr>`[src]

Performs the conversion.

### `impl From<OsString> for Arc<OsStr>`1.24.0[src]

#### `fn from(s: OsString) -> Arc<OsStr>`[src]

Converts a `OsString` into a `Arc``<OsStr>` without copying or allocating.

### `impl<'_> From<&'_ OsStr> for Arc<OsStr>`1.24.0[src]

#### `fn from(s: &OsStr) -> Arc<OsStr>`[src]

Performs the conversion.

### `impl From<PathBuf> for Arc<Path>`1.24.0[src]

#### `fn from(s: PathBuf) -> Arc<Path>`[src]

Converts a `PathBuf` into an `Arc` by moving the `PathBuf` data into a new `Arc` buffer.

### `impl<'_> From<&'_ Path> for Arc<Path>`1.24.0[src]

#### `fn from(s: &Path) -> Arc<Path>`[src]

Converts a `Path` into an `Arc` by copying the `Path` data into a new `Arc` buffer.

## Auto Trait Implementations

### `impl<T: ?Sized> RefUnwindSafe for Arc<T> where
T: RefUnwindSafe,`

## Blanket Implementations

### `impl<T> From<T> for T`[src]

#### `fn from(t: T) -> T`[src]

Performs the conversion.

### `impl<T> From<!> for T`[src]

#### `fn from(t: !) -> T`[src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `fn into(self) -> U`[src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

Performs the conversion.

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `fn to_owned(&self) -> T`[src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `fn clone_into(&self, target: &mut T)`[src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T> ToString for T where
T: Display + ?Sized,` [src]

#### `default fn to_string(&self) -> String`[src]

Converts the given value to a `String`. Read more