Struct core::sync::atomic::AtomicUsize

#[repr(C)]
pub struct AtomicUsize { /* fields omitted */ }

An integer type which can be safely shared between threads.

This type has the same in-memory representation as the underlying integer type, usize. For more about the differences between atomic types and non-atomic types as well as information about the portability of this type, please see the module-level documentation.

Methods

impl AtomicUsize

pub const fn new(v: usize) -> Self

Creates a new atomic integer.

Examples

use std::sync::atomic::AtomicUsize;

let atomic_forty_two = AtomicUsize::new(42);

pub fn get_mut(&mut self) -> &mut usize

Returns a mutable reference to the underlying integer.

This is safe because the mutable reference guarantees that no other threads are concurrently accessing the atomic data.

Examples

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

let mut some_var = AtomicUsize::new(10);
assert_eq!(*some_var.get_mut(), 10);
*some_var.get_mut() = 5;
assert_eq!(some_var.load(Ordering::SeqCst), 5);

pub fn into_inner(self) -> usize

Consumes the atomic and returns the contained value.

This is safe because passing self by value guarantees that no other threads are concurrently accessing the atomic data.

Examples

use std::sync::atomic::AtomicUsize;

let some_var = AtomicUsize::new(5);
assert_eq!(some_var.into_inner(), 5);

pub fn load(&self, order: Ordering) -> usize

Loads a value from the atomic integer.

load takes an Ordering argument which describes the memory ordering of this operation. Possible values are SeqCst, Acquire and Relaxed.

Panics

Panics if order is Release or AcqRel.

Examples

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

let some_var = AtomicUsize::new(5);

assert_eq!(some_var.load(Ordering::Relaxed), 5);

pub fn store(&self, val: usize, order: Ordering)

Stores a value into the atomic integer.

store takes an Ordering argument which describes the memory ordering of this operation. Possible values are SeqCst, Release and Relaxed.

Panics

Panics if order is Acquire or AcqRel.

Examples

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

let some_var = AtomicUsize::new(5);

some_var.store(10, Ordering::Relaxed);
assert_eq!(some_var.load(Ordering::Relaxed), 10);

pub fn swap(&self, val: usize, order: Ordering) -> usize

Stores a value into the atomic integer, returning the previous value.

swap takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

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

let some_var = AtomicUsize::new(5);

assert_eq!(some_var.swap(10, Ordering::Relaxed), 5);

pub fn compare_and_swap(
    &self,
    current: usize,
    new: usize,
    order: Ordering
) -> usize

Stores a value into the atomic integer if the current value is the same as the current value.

The return value is always the previous value. If it is equal to current, then the value was updated.

compare_and_swap also takes an Ordering argument which describes the memory ordering of this operation. Notice that even when using AcqRel, the operation might fail and hence just perform an Acquire load, but not have Release semantics. Using Acquire makes the store part of this operation Relaxed if it happens, and using Release makes the load part Relaxed.

Examples

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

let some_var = AtomicUsize::new(5);

assert_eq!(some_var.compare_and_swap(5, 10, Ordering::Relaxed), 5);
assert_eq!(some_var.load(Ordering::Relaxed), 10);

assert_eq!(some_var.compare_and_swap(6, 12, Ordering::Relaxed), 10);
assert_eq!(some_var.load(Ordering::Relaxed), 10);

pub fn compare_exchange(
    &self,
    current: usize,
    new: usize,
    success: Ordering,
    failure: Ordering
) -> Result<usize, usize>

Stores a value into the atomic integer if the current value is the same as the current value.

The return value is a result indicating whether the new value was written and containing the previous value. On success this value is guaranteed to be equal to current.

compare_exchange takes two Ordering arguments to describe the memory ordering of this operation. The first describes the required ordering if the operation succeeds while the second describes the required ordering when the operation fails. Using Acquire as success ordering makes the store part of this operation Relaxed, and using Release makes the successful load Relaxed. The failure ordering can only be SeqCst, Acquire or Relaxed and must be equivalent to or weaker than the success ordering.

Examples

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

let some_var = AtomicUsize::new(5);

assert_eq!(some_var.compare_exchange(5, 10,
                                     Ordering::Acquire,
                                     Ordering::Relaxed),
           Ok(5));
assert_eq!(some_var.load(Ordering::Relaxed), 10);

assert_eq!(some_var.compare_exchange(6, 12,
                                     Ordering::SeqCst,
                                     Ordering::Acquire),
           Err(10));
assert_eq!(some_var.load(Ordering::Relaxed), 10);

pub fn compare_exchange_weak(
    &self,
    current: usize,
    new: usize,
    success: Ordering,
    failure: Ordering
) -> Result<usize, usize>

Stores a value into the atomic integer if the current value is the same as the current value.

Unlike compare_exchange, this function is allowed to spuriously fail even when the comparison succeeds, which can result in more efficient code on some platforms. The return value is a result indicating whether the new value was written and containing the previous value.

compare_exchange_weak takes two Ordering arguments to describe the memory ordering of this operation. The first describes the required ordering if the operation succeeds while the second describes the required ordering when the operation fails. Using Acquire as success ordering makes the store part of this operation Relaxed, and using Release makes the successful load Relaxed. The failure ordering can only be SeqCst, Acquire or Relaxed and must be equivalent to or weaker than the success ordering.

Examples

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

let val = AtomicUsize::new(4);

let mut old = val.load(Ordering::Relaxed);
loop {
    let new = old * 2;
    match val.compare_exchange_weak(old, new, Ordering::SeqCst, Ordering::Relaxed) {
        Ok(_) => break,
        Err(x) => old = x,
    }
}

pub fn fetch_add(&self, val: usize, order: Ordering) -> usize

Adds to the current value, returning the previous value.

This operation wraps around on overflow.

fetch_add takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

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

let foo = AtomicUsize::new(0);
assert_eq!(foo.fetch_add(10, Ordering::SeqCst), 0);
assert_eq!(foo.load(Ordering::SeqCst), 10);

pub fn fetch_sub(&self, val: usize, order: Ordering) -> usize

Subtracts from the current value, returning the previous value.

This operation wraps around on overflow.

fetch_sub takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

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

let foo = AtomicUsize::new(20);
assert_eq!(foo.fetch_sub(10, Ordering::SeqCst), 20);
assert_eq!(foo.load(Ordering::SeqCst), 10);

pub fn fetch_and(&self, val: usize, order: Ordering) -> usize

Bitwise "and" with the current value.

Performs a bitwise "and" operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_and takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

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

let foo = AtomicUsize::new(0b101101);
assert_eq!(foo.fetch_and(0b110011, Ordering::SeqCst), 0b101101);
assert_eq!(foo.load(Ordering::SeqCst), 0b100001);

pub fn fetch_nand(&self, val: usize, order: Ordering) -> usize

Bitwise "nand" with the current value.

Performs a bitwise "nand" operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_nand takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

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

let foo = AtomicUsize::new(0x13);
assert_eq!(foo.fetch_nand(0x31, Ordering::SeqCst), 0x13);
assert_eq!(foo.load(Ordering::SeqCst), !(0x13 & 0x31));

pub fn fetch_or(&self, val: usize, order: Ordering) -> usize

Bitwise "or" with the current value.

Performs a bitwise "or" operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_or takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

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

let foo = AtomicUsize::new(0b101101);
assert_eq!(foo.fetch_or(0b110011, Ordering::SeqCst), 0b101101);
assert_eq!(foo.load(Ordering::SeqCst), 0b111111);

pub fn fetch_xor(&self, val: usize, order: Ordering) -> usize

Bitwise "xor" with the current value.

Performs a bitwise "xor" operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_xor takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

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

let foo = AtomicUsize::new(0b101101);
assert_eq!(foo.fetch_xor(0b110011, Ordering::SeqCst), 0b101101);
assert_eq!(foo.load(Ordering::SeqCst), 0b011110);

pub fn fetch_update<F>(
    &self,
    f: F,
    fetch_order: Ordering,
    set_order: Ordering
) -> Result<usize, usize> where
    F: FnMut(usize) -> Option<usize>, 

🔬 This is a nightly-only experimental API. (no_more_cas #48655)

no more CAS loops in user code

Fetches the value, and applies a function to it that returns an optional new value. Returns a Result of Ok(previous_value) if the function returned Some(_), else Err(previous_value).

Note: This may call the function multiple times if the value has been changed from other threads in the meantime, as long as the function returns Some(_), but the function will have been applied but once to the stored value.

fetch_update takes two Ordering arguments to describe the memory ordering of this operation. The first describes the required ordering for loads and failed updates while the second describes the required ordering when the operation finally succeeds. Beware that this is different from the two modes in compare_exchange!

Using Acquire as success ordering makes the store part of this operation Relaxed, and using Release makes the final successful load Relaxed. The (failed) load ordering can only be SeqCst, Acquire or Relaxed and must be equivalent to or weaker than the success ordering.

Examples

#![feature(no_more_cas)]
use std::sync::atomic::{AtomicUsize, Ordering};

let x = AtomicUsize::new(7);
assert_eq!(x.fetch_update(|_| None, Ordering::SeqCst, Ordering::SeqCst), Err(7));
assert_eq!(x.fetch_update(|x| Some(x + 1), Ordering::SeqCst, Ordering::SeqCst), Ok(7));
assert_eq!(x.fetch_update(|x| Some(x + 1), Ordering::SeqCst, Ordering::SeqCst), Ok(8));
assert_eq!(x.load(Ordering::SeqCst), 9);

pub fn fetch_max(&self, val: usize, order: Ordering) -> usize

🔬 This is a nightly-only experimental API. (atomic_min_max #48655)

easier and faster min/max than writing manual CAS loop

Maximum with the current value.

Finds the maximum of the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_max takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

#![feature(atomic_min_max)]
use std::sync::atomic::{AtomicUsize, Ordering};

let foo = AtomicUsize::new(23);
assert_eq!(foo.fetch_max(42, Ordering::SeqCst), 23);
assert_eq!(foo.load(Ordering::SeqCst), 42);

If you want to obtain the maximum value in one step, you can use the following:

#![feature(atomic_min_max)]
use std::sync::atomic::{AtomicUsize, Ordering};

let foo = AtomicUsize::new(23);
let bar = 42;
let max_foo = foo.fetch_max(bar, Ordering::SeqCst).max(bar);
assert!(max_foo == 42);

pub fn fetch_min(&self, val: usize, order: Ordering) -> usize

🔬 This is a nightly-only experimental API. (atomic_min_max #48655)

easier and faster min/max than writing manual CAS loop

Minimum with the current value.

Finds the minimum of the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_min takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Examples

#![feature(atomic_min_max)]
use std::sync::atomic::{AtomicUsize, Ordering};

let foo = AtomicUsize::new(23);
assert_eq!(foo.fetch_min(42, Ordering::Relaxed), 23);
assert_eq!(foo.load(Ordering::Relaxed), 23);
assert_eq!(foo.fetch_min(22, Ordering::Relaxed), 23);
assert_eq!(foo.load(Ordering::Relaxed), 22);

If you want to obtain the minimum value in one step, you can use the following:

#![feature(atomic_min_max)]
use std::sync::atomic::{AtomicUsize, Ordering};

let foo = AtomicUsize::new(23);
let bar = 12;
let min_foo = foo.fetch_min(bar, Ordering::SeqCst).min(bar);
assert_eq!(min_foo, 12);

Trait Implementations

impl Sync for AtomicUsize

impl Default for AtomicUsize

fn default() -> Self

Returns the "default value" for a type.

impl From<usize> for AtomicUsize

fn from(v: usize) -> Self

Converts an usize into an AtomicUsize.

impl Debug for AtomicUsize

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

Formats the value using the given formatter.