Trait Cache

Source

pub trait Cache<K, V>where
    K: Eq + Hash,
    V: Clone,{
    // Required methods
    fn get(&self, key: &K) -> Option<V>;
    fn insert(&self, key: K, value: V) -> Option<V>;
    fn remove(&self, key: &K) -> Option<V>;
    fn contains_key(&self, key: &K) -> bool;
    fn len(&self) -> usize;
    fn clear(&self);
    fn capacity(&self) -> usize;

    // Provided method
    fn is_empty(&self) -> bool { ... }
}

Expand description

The common read / write / evict contract every cache type in this crate implements.

All methods take &self (not &mut self) so a cache instance can be shared across threads and across .await points without external locking. Implementations use interior mutability.

§Access semantics

get is an access: it may update the eviction order (e.g. promoting the entry to most-recently-used).
contains_key is a query only: it must not update the eviction order.
insert is an access on the inserted key.
remove is destructive and does not update order.

§Example

use cache_mod::{Cache, LruCache};

let cache: LruCache<&'static str, u32> = LruCache::new(4).expect("capacity > 0");

assert_eq!(cache.insert("a", 1), None);
assert_eq!(cache.get(&"a"), Some(1));
assert!(cache.contains_key(&"a"));
assert_eq!(cache.len(), 1);

assert_eq!(cache.remove(&"a"), Some(1));
assert!(cache.is_empty());