Struct atomic_polyfill::AtomicBool

#[repr(C, align(1))]
pub struct AtomicBool { /* private fields */ }

A boolean type which can be safely shared between threads.

This type has the same in-memory representation as a [bool].

Note: This type is only available on platforms that support atomic loads and stores of u8.

Implementations

impl AtomicBool

pub const fn new(v: bool) -> AtomicBool

Creates a new AtomicBool.

Examples

use std::sync::atomic::AtomicBool;

let atomic_true = AtomicBool::new(true);
let atomic_false = AtomicBool::new(false);

pub unsafe fn from_ptr<'a>(ptr: *mut bool) -> &'a AtomicBool

🔬This is a nightly-only experimental API. (atomic_from_ptr)

Creates a new AtomicBool from a pointer.

Examples

#![feature(atomic_from_ptr, pointer_is_aligned)]
use std::sync::atomic::{self, AtomicBool};
use std::mem::align_of;

// Get a pointer to an allocated value
let ptr: *mut bool = Box::into_raw(Box::new(false));

assert!(ptr.is_aligned_to(align_of::<AtomicBool>()));

{
    // Create an atomic view of the allocated value
    let atomic = unsafe { AtomicBool::from_ptr(ptr) };

    // Use `atomic` for atomic operations, possibly share it with other threads
    atomic.store(true, atomic::Ordering::Relaxed);
}

// It's ok to non-atomically access the value behind `ptr`,
// since the reference to the atomic ended its lifetime in the block above
assert_eq!(unsafe { *ptr }, true);

// Deallocate the value
unsafe { drop(Box::from_raw(ptr)) }

Safety

• ptr must be aligned to align_of::<AtomicBool>() (note that on some platforms this can be bigger than align_of::<bool>()).
• ptr must be valid for both reads and writes for the whole lifetime 'a.
• The value behind ptr must not be accessed through non-atomic operations for the whole lifetime 'a.

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

Returns a mutable reference to the underlying [bool].

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

Examples

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

let mut some_bool = AtomicBool::new(true);
assert_eq!(*some_bool.get_mut(), true);
*some_bool.get_mut() = false;
assert_eq!(some_bool.load(Ordering::SeqCst), false);

pub fn from_mut(v: &mut bool) -> &mut AtomicBool

🔬This is a nightly-only experimental API. (atomic_from_mut)

Get atomic access to a &mut bool.

Examples

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

let mut some_bool = true;
let a = AtomicBool::from_mut(&mut some_bool);
a.store(false, Ordering::Relaxed);
assert_eq!(some_bool, false);

pub fn get_mut_slice(this: &mut [AtomicBool]) -> &mut [bool]

🔬This is a nightly-only experimental API. (atomic_from_mut)

Get non-atomic access to a &mut [AtomicBool] slice.

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

Examples

#![feature(atomic_from_mut, inline_const)]
use std::sync::atomic::{AtomicBool, Ordering};

let mut some_bools = [const { AtomicBool::new(false) }; 10];

let view: &mut [bool] = AtomicBool::get_mut_slice(&mut some_bools);
assert_eq!(view, [false; 10]);
view[..5].copy_from_slice(&[true; 5]);

std::thread::scope(|s| {
    for t in &some_bools[..5] {
        s.spawn(move || assert_eq!(t.load(Ordering::Relaxed), true));
    }

    for f in &some_bools[5..] {
        s.spawn(move || assert_eq!(f.load(Ordering::Relaxed), false));
    }
});

pub fn from_mut_slice(v: &mut [bool]) -> &mut [AtomicBool]

🔬This is a nightly-only experimental API. (atomic_from_mut)

Get atomic access to a &mut [bool] slice.

Examples

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

let mut some_bools = [false; 10];
let a = &*AtomicBool::from_mut_slice(&mut some_bools);
std::thread::scope(|s| {
    for i in 0..a.len() {
        s.spawn(move || a[i].store(true, Ordering::Relaxed));
    }
});
assert_eq!(some_bools, [true; 10]);

pub fn into_inner(self) -> bool

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::AtomicBool;

let some_bool = AtomicBool::new(true);
assert_eq!(some_bool.into_inner(), true);

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

Loads a value from the bool.

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::{AtomicBool, Ordering};

let some_bool = AtomicBool::new(true);

assert_eq!(some_bool.load(Ordering::Relaxed), true);

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

Stores a value into the bool.

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::{AtomicBool, Ordering};

let some_bool = AtomicBool::new(true);

some_bool.store(false, Ordering::Relaxed);
assert_eq!(some_bool.load(Ordering::Relaxed), false);

pub const fn as_ptr(&self) -> *mut bool

Returns a mutable pointer to the underlying [bool].

Doing non-atomic reads and writes on the resulting integer can be a data race. This method is mostly useful for FFI, where the function signature may use *mut bool instead of &AtomicBool.

Returning an *mut pointer from a shared reference to this atomic is safe because the atomic types work with interior mutability. All modifications of an atomic change the value through a shared reference, and can do so safely as long as they use atomic operations. Any use of the returned raw pointer requires an unsafe block and still has to uphold the same restriction: operations on it must be atomic.

Examples

use std::sync::atomic::AtomicBool;

extern "C" {
    fn my_atomic_op(arg: *mut bool);
}

let mut atomic = AtomicBool::new(true);
unsafe {
    my_atomic_op(atomic.as_ptr());
}

Trait Implementations

impl Debug for AtomicBool

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

Formats the value using the given formatter.

impl Default for AtomicBool

fn default() -> AtomicBool

Creates an AtomicBool initialized to false.

impl From<bool> for AtomicBool

fn from(b: bool) -> AtomicBool

Converts a bool into an AtomicBool.

Examples

use std::sync::atomic::AtomicBool;
let atomic_bool = AtomicBool::from(true);
assert_eq!(format!("{atomic_bool:?}"), "true")

impl RefUnwindSafe for AtomicBool

impl Sync for AtomicBool