Struct InternCache

pub(crate) struct InternCache<T: ?Sized> {
    cache: OnceLock<Mutex<WeakHashSet<Weak<T>>>>,
}

An InternCache is a lazily-constructed weak set of objects.

Let’s break that down! It’s “lazily constructed” because it doesn’t actually allocate anything until you use it for the first time. That allows it to have a const new method, so you can make these static.

It’s “weak” because it only holds weak references to its objects; once every strong reference is gone, the object is unallocated. Later, the hash entry is (lazily) removed.

Fields

cache: OnceLock<Mutex<WeakHashSet<Weak<T>>>>

Underlying hashset for interned objects

Implementations

impl<T: ?Sized> InternCache<T>

pub(crate) const fn new() -> Self

Create a new, empty, InternCache.

impl<T: Eq + Hash + ?Sized> InternCache<T>

fn cache(&self) -> MutexGuard<'_, WeakHashSet<Weak<T>>>

Helper: initialize the cache if needed, then lock it.

impl<T: Eq + Hash> InternCache<T>

pub(crate) fn intern(&self, value: T) -> Arc<T>

Intern a given value into this cache.

If value is already stored in this cache, we return a reference to the stored value. Otherwise, we insert value into the cache, and return that.

impl<T: Hash + Eq + ?Sized> InternCache<T>

pub(crate) fn intern_ref<'a, V>(&self, value: &'a V) -> Arc<T>

where V: Hash + Eq + ?Sized, &'a V: Into<Arc<T>>, T: Borrow<V>,

Intern an object by reference.

Works with unsized types, but requires that the reference implements Into<Arc<T>>.