Trait Cache 

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 { ... }
}

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());

Required Methods

fn get(&self, key: &K) -> Option<V>

Returns the value associated with key, if any, and counts as an access for the purposes of the eviction policy.

fn insert(&self, key: K, value: V) -> Option<V>

Inserts value under key. Returns the previously-stored value if key was already present.

May evict one or more existing entries to make room, according to the cache’s eviction policy.

fn remove(&self, key: &K) -> Option<V>

Removes the entry for key and returns the value if present.

fn contains_key(&self, key: &K) -> bool

Returns true if the cache currently holds an entry for key.

Unlike get, this method does not count as an access — eviction order is left unchanged.

fn len(&self) -> usize

Number of entries currently stored.

fn clear(&self)

Removes every entry. Capacity is preserved.

fn capacity(&self) -> usize

Configured capacity bound.

The unit depends on the implementation:

• LruCache, LfuCache, TtlCache, TinyLfuCache — maximum number of entries.
• SizedCache — maximum total byte-weight across entries.

Provided Methods

fn is_empty(&self) -> bool

Returns true when the cache holds no entries.

Implementors

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

where K: Eq + Hash + Clone, V: Clone,

Available on crate feature std only.

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

where K: Eq + Hash + Clone, V: Clone,

Available on crate feature std only.

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

where K: Eq + Hash + Clone, V: Clone,

Available on crate feature std only.

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

where K: Eq + Hash + Clone, V: Clone,

Available on crate feature std only.

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

where K: Eq + Hash + Clone, V: Clone,

Available on crate feature std only.