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..100).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..100).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> where T: ?Sized

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

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());

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

fn make_mut(this: &mut Arc<T>) -> &mut T1.4.0

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

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

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>

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);

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

Unwraps the contained value if the Arc<T> has exactly one strong reference.

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

This will succeed even if there are outstanding weak references.

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)));

Trait Implementations

impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Arc<T>1.9.0

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

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

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

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

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

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

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

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

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

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

Partial comparison for two Arc<T>s.

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

Examples

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

let five = Arc::new(5);

five.partial_cmp(&Arc::new(5));

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

Less-than comparison for two Arc<T>s.

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

Examples

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

let five = Arc::new(5);

five < Arc::new(5);

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

'Less-than or equal to' comparison for two Arc<T>s.

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

Examples

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

let five = Arc::new(5);

five <= Arc::new(5);

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

Greater-than comparison for two Arc<T>s.

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

Examples

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

let five = Arc::new(5);

five > Arc::new(5);

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

'Greater-than or equal to' comparison for two Arc<T>s.

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

Examples

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

let five = Arc::new(5);

five >= Arc::new(5);

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

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

Equality for two Arc<T>s.

Two Arc<T>s are equal if their inner value are equal.

Examples

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

let five = Arc::new(5);

five == Arc::new(5);

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

Inequality for two Arc<T>s.

Two Arc<T>s are unequal if their inner value are unequal.

Examples

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

let five = Arc::new(5);

five != Arc::new(5);

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

fn drop(&mut self)

Drops the Arc<T>.

This will decrement the strong reference count. If the strong reference count becomes zero and the only other references are Weak<T> ones, drops the inner value.

Examples

fn main() { use std::sync::Arc; { let five = Arc::new(5); // stuff drop(five); // explicit drop } { let five = Arc::new(5); // stuff } // implicit drop }
use std::sync::Arc;

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

    // stuff

    drop(five); // explicit drop
}
{
    let five = Arc::new(5);

    // stuff

} // implicit drop

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

type Target = T

fn deref(&self) -> &T

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

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

Makes a clone of the Arc<T>.

This increases the strong reference count.

Examples

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

let five = Arc::new(5);

five.clone();

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

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

fn as_ref(&self) -> &T

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

fn borrow(&self) -> &T

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

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

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

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

fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher1.3.0

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

fn default() -> Arc<T>