Struct mmtk::util::rust_util::InitializeOnce

pub struct InitializeOnce<T: 'static> {
    v: UnsafeCell<MaybeUninit<T>>,
    once: Once,
}

InitializeOnce creates an uninitialized value that needs to be manually initialized later. InitializeOnce guarantees the value is only initialized once. This type is used to allow more efficient reads. Unlike the lazy_static! which checks whether the static is initialized in every read, InitializeOnce has no extra check for reads.

Fields

v: UnsafeCell<MaybeUninit<T>>

once: Once

This is used to guarantee init_fn is only called once.

Implementations

impl<T> InitializeOnce<T>

pub const fn new() -> Self

pub fn initialize_once(&self, init_fn: &'static dyn Fn() -> T)

Initialize the value. This should be called before ever using the struct. If this method is called by multiple threads, the first thread will initialize the value, and the other threads will be blocked until the initialization is done (Once returns).

pub fn get_ref(&self) -> &T

Get the value. This should only be used after initialize_once()

pub unsafe fn get_mut(&self) -> &mut T

Get a mutable reference to the value. This is currently only used for SFTMap during plan creation (single threaded), and before the plan creation is done, the binding cannot use MMTK at all.

Safety

The caller needs to make sure there is no race when mutating the value.

Trait Implementations

impl<T> Deref for InitializeOnce<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T> Sync for InitializeOnce<T>