Struct once_cell::race::OnceRef

pub struct OnceRef<'a, T> {
    inner: AtomicPtr<T>,
    ghost: PhantomData<UnsafeCell<&'a T>>,
}

A thread-safe cell which can be written to only once.

Fields

inner: AtomicPtr<T>

ghost: PhantomData<UnsafeCell<&'a T>>

Implementations

impl<'a, T> OnceRef<'a, T>

pub const fn new() -> OnceRef<'a, T>

Creates a new empty cell.

pub fn get(&self) -> Option<&'a T>

Gets a reference to the underlying value.

pub fn set(&self, value: &'a T) -> Result<(), ()>

Sets the contents of this cell to value.

Returns Ok(()) if the cell was empty and Err(value) if it was full.

pub fn get_or_init<F>(&self, f: F) -> &'a Twhere F: FnOnce() -> &'a T,

Gets the contents of the cell, initializing it with f if the cell was empty.

If several threads concurrently run get_or_init, more than one f can be called. However, all threads will return the same value, produced by some f.

pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&'a T, E>where F: FnOnce() -> Result<&'a T, E>,

Gets the contents of the cell, initializing it with f if the cell was empty. If the cell was empty and f failed, an error is returned.

If several threads concurrently run get_or_init, more than one f can be called. However, all threads will return the same value, produced by some f.

fn _dummy()

use once_cell::race::OnceRef;

let mut l = OnceRef::new();

{
    let y = 2;
    let mut r = OnceRef::new();
    r.set(&y).unwrap();
    core::mem::swap(&mut l, &mut r);
}

// l now contains a dangling reference to y
eprintln!("uaf: {}", l.get().unwrap());

Trait Implementations

impl<'a, T> Debug for OnceRef<'a, T>

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

Formats the value using the given formatter.

impl<'a, T> Default for OnceRef<'a, T>

fn default() -> Self

Returns the “default value” for a type.

impl<'a, T: Sync> Sync for OnceRef<'a, T>