Struct Cache

pub struct Cache<K, V> {
    inner: Mutex<HashMap<K, V>>,
}

Cache that remembers the result for each key.

Fields

inner: Mutex<HashMap<K, V>>

Implementations

impl<K: Eq + Hash + Clone, V: Clone> Cache<K, V>

pub fn get_or_insert_with<F: FnOnce(K) -> V>(&self, key: K, f: F) -> V

Retrieve the value or insert a new one created by f.

An invocation to this function should not block another invocation with a different key. For example, if a thread calls get_or_insert_with(key1, f1) and another thread calls get_or_insert_with(key2, f2) (key1≠key2, key1,key2∉cache) concurrently, f1 and f2 should run concurrently.

On the other hand, since f may consume a lot of resource (= money), it’s undesirable to duplicate the work. That is, f should be run only once for each key. Specifically, even for concurrent invocations of get_or_insert_with(key, f), f is called only once per key.

Hint: the Entry API may be useful in implementing this function.

Trait Implementations

impl<K: Debug, V: Debug> Debug for Cache<K, V>

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

Formats the value using the given formatter.

impl<K, V> Default for Cache<K, V>

fn default() -> Self

Returns the “default value” for a type.