Struct std::sync::Arc [] [src]

pub struct Arc<T> where T: ?Sized {
    // some fields omitted
}
1.0.0

An atomically reference counted wrapper for shared state.

Examples

In this example, a large vector is shared between several threads. With simple pipes, without Arc, a copy would have to be made for each thread.

When you clone an Arc<T>, it will create another pointer to the data and increase the reference counter.

use std::sync::Arc; use std::thread; fn main() { let numbers: Vec<_> = (0..100u32).collect(); let shared_numbers = Arc::new(numbers); for _ in 0..10 { let child_numbers = shared_numbers.clone(); thread::spawn(move || { let local_numbers = &child_numbers[..]; // Work with the local numbers }); } }
use std::sync::Arc;
use std::thread;

fn main() {
    let numbers: Vec<_> = (0..100u32).collect();
    let shared_numbers = Arc::new(numbers);

    for _ in 0..10 {
        let child_numbers = shared_numbers.clone();

        thread::spawn(move || {
            let local_numbers = &child_numbers[..];

            // Work with the local numbers
        });
    }
}

Methods

impl<T> Arc<T>

fn new(data: T) -> Arc<T>

Constructs a new Arc<T>.

Examples

fn main() { use std::sync::Arc; let five = Arc::new(5); }
use std::sync::Arc;

let five = Arc::new(5);

1.4.0fn try_unwrap(this: Arc<T>) -> Result<T, Arc<T>>

Unwraps the contained value if the Arc<T> has only one strong reference. This will succeed even if there are outstanding weak references.

Otherwise, an Err is returned with the same Arc<T>.

Examples

fn main() { use std::sync::Arc; let x = Arc::new(3); assert_eq!(Arc::try_unwrap(x), Ok(3)); let x = Arc::new(4); let _y = x.clone(); assert_eq!(Arc::try_unwrap(x), Err(Arc::new(4))); }
use std::sync::Arc;

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

let x = Arc::new(4);
let _y = x.clone();
assert_eq!(Arc::try_unwrap(x), Err(Arc::new(4)));

impl<T> Arc<T> where T: ?Sized

1.4.0fn downgrade(this: &Arc<T>) -> Weak<T>

Downgrades the Arc<T> to a Weak<T> reference.

Examples

fn main() { use std::sync::Arc; let five = Arc::new(5); let weak_five = Arc::downgrade(&five); }
use std::sync::Arc;

let five = Arc::new(5);

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

fn weak_count(this: &Arc<T>) -> usize

Unstable (arc_counts #28356)

: not clearly useful, and racy

Get the number of weak references to this value.

fn strong_count(this: &Arc<T>) -> usize

Unstable (arc_counts #28356)

: not clearly useful, and racy

Get the number of strong references to this value.

impl<T> Arc<T> where T: Clone

1.4.0fn make_mut(this: &mut Arc<T>) -> &mut T

Make a mutable reference into the given Arc<T>. If the Arc<T> has more than one strong reference, or any weak references, the inner data is cloned.

This is also referred to as a copy-on-write.

Examples

fn main() { use std::sync::Arc; let mut data = Arc::new(5); *Arc::make_mut(&mut data) += 1; // Won't clone anything let mut other_data = data.clone(); // 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 // Note: data and other_data now point to different numbers assert_eq!(*data, 8); assert_eq!(*other_data, 12); }
use std::sync::Arc;

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

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

// Note: data and other_data now point to different numbers
assert_eq!(*data, 8);
assert_eq!(*other_data, 12);

impl<T> Arc<T> where T: ?Sized

1.4.0fn get_mut(this: &mut Arc<T>) -> Option<&mut T>

Returns a mutable reference to the contained value if the Arc<T> has one strong reference and no weak references.

Examples

fn main() { use std::sync::Arc; let mut x = Arc::new(3); *Arc::get_mut(&mut x).unwrap() = 4; assert_eq!(*x, 4); let _y = x.clone(); assert!(Arc::get_mut(&mut x).is_none()); }
use std::sync::Arc;

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

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

Trait Implementations

impl<T> Send for Arc<T> where T: Send + Sync + ?Sized

impl<T> Sync for Arc<T> where T: Send + Sync + ?Sized

impl<T, U> CoerceUnsized<Arc<U>> for Arc<T> where U: ?Sized, T: Unsize<U> + ?Sized

impl<T> Clone for Arc<T> where T: ?Sized

fn clone(&self) -> Arc<T>

fn clone_from(&mut self, source: &Self)

impl<T> Deref for Arc<T> where T: ?Sized

type Target = T

fn deref(&self) -> &T

impl<T> Drop for Arc<T> where T: ?Sized

fn drop(&mut self)

impl<T> PartialEq<Arc<T>> for Arc<T> where T: PartialEq<T> + ?Sized

fn eq(&self, other: &Arc<T>) -> bool

fn ne(&self, other: &Arc<T>) -> bool

impl<T> PartialOrd<Arc<T>> for Arc<T> where T: PartialOrd<T> + ?Sized

fn partial_cmp(&self, other: &Arc<T>) -> Option<Ordering>

fn lt(&self, other: &Arc<T>) -> bool

fn le(&self, other: &Arc<T>) -> bool

fn gt(&self, other: &Arc<T>) -> bool

fn ge(&self, other: &Arc<T>) -> bool

impl<T> Ord for Arc<T> where T: Ord + ?Sized

fn cmp(&self, other: &Arc<T>) -> Ordering

impl<T> Eq for Arc<T> where T: Eq + ?Sized

impl<T> Display for Arc<T> where T: Display + ?Sized

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

impl<T> Debug for Arc<T> where T: Debug + ?Sized

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

impl<T> Pointer for Arc<T> where T: ?Sized

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

impl<T> Default for Arc<T> where T: Default

fn default() -> Arc<T>

impl<T> Hash for Arc<T> where T: Hash + ?Sized

fn hash<H>(&self, state: &mut H) where H: Hasher

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

impl<T> From<T> for Arc<T>1.6.0

fn from(t: T) -> Arc<T>

impl<T> Borrow<T> for Arc<T> where T: ?Sized

fn borrow(&self) -> &T

impl<T> AsRef<T> for Arc<T> where T: ?Sized1.5.0

fn as_ref(&self) -> &T

impl<T: RefRecoverSafe + ?Sized> RecoverSafe for Arc<T>