Struct NicheCell 

pub struct NicheCell<T>(UnsafeCell<Option<T>>);

A datatype with interior mutability, which can be uninitialized via [Option]. This datatype is designed to be used with values that can take advantage of niche optimization (where the datatype T has a value which is guaranteed to be invalid, like a NonZeroU64 being zero)

The caller may also use this datatype if [Option] instead of MaybeUninit is necessary for code safety, as this type returns [None] on calling Self::get if Self::init has not been run yet, compared to UncheckedCell where calling UncheckedCell::get before UncheckedCell::init is undefined behavior.

Tuple Fields

0: UnsafeCell<Option<T>>

Implementations

impl<T> NicheCell<T>

pub const fn new() -> Self

Constructor; creates a new NicheCell containing [None]

pub unsafe fn init(&self, value: T)

Set the inner value

Safety

The caller must guarantee the following:

• That this method has never been called before and will never be called again
• That at the time of calling this method, no references or pointers to this data exist
• While this method is being called, no other CPU is working with the given data

pub unsafe fn get(&self) -> &Option<T>

Get a reference to the inner value

Safety

The caller must guarantee that at this method’s entire execution time, no mutable references or pointers to this data exist or will exist

Trait Implementations

impl<T: Send + Sync> Sync for NicheCell<T>

Safety: this type can be shared across CPUs as the callers have the responsibility to ensure proper data safety because of the unsafe contracts on init and get