Struct LruCache 

pub struct LruCache<K, V>
where
    K: Clone + Eq + Hash,
{ /* private fields */ }

A fixed-capacity LRU cache.

The cache holds at most capacity entries. When a put would exceed the capacity, the least-recently-used entry is evicted. get updates the recency so the just-read entry becomes the most- recently-used.

All operations are O(1) amortized (put, get, remove, contains) except iter, which is O(n).

Capacity edge cases

• capacity = 0 - the cache accepts no entries. Both put and get behave as no-ops (well, get still evicts because there’s nothing to evict; put silently drops the entry).
• capacity = 1 - the cache holds exactly one entry. Every put evicts the previous entry.

Lombok New derivation

#[derive(New)] generates LruCache::new(capacity) — the map and order fields are skipped with #[new(skip)] so Lombok falls back to <HashMap as Default>::default() and <VecDeque as Default>::default() (which both call new() internally), preserving the canonical single-argument call site.

Implementations

impl<K, V> LruCache<K, V>

where K: Clone + Eq + Hash,

pub fn len(&self) -> usize

Returns the current number of entries in the cache.

Returns

• usize - The number of items in the collection.

pub fn is_empty(&self) -> bool

Returns true if the cache is empty.

Returns

• bool - true when the collection is empty.

pub fn is_full(&self) -> bool

Returns true if the cache is at capacity.

Returns

• bool - A boolean.

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

Returns true if the cache contains a value for the given key. Does NOT update the recency (use get for that).

Arguments

• &K - Shared reference to a K.

Returns

• bool - A boolean.

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

Returns the value for the given key, updating the recency so the entry becomes the most-recently- used.

Returns None if the key is not in the cache.

Arguments

• &K - Shared reference to a K.

Returns

• Option<V> - The current value (or a snapshot thereof).

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

Returns the value for the given key without updating the recency. Useful for “is this cached?” checks that should not affect eviction order.

Arguments

• &K - Shared reference to a K.

Returns

• Option<V> - Some(...) on success, None otherwise.

pub fn put(&mut self, key: K, value: V) -> Option<(K, V)>

Inserts a key-value pair into the cache. If the key is already present, the existing value is replaced (and the entry becomes the most- recently-used). If the cache is at capacity and the key is new, the least-recently-used entry is evicted first.

Returns the evicted entry, if any.

Arguments

• K: Clone + Eq + Hash - A generic type parameter.
• V - A V parameter.

Returns

• Option<(K, V)> - Some(...) on success, None otherwise.

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

Removes the entry for the given key, returning the removed value if any.

Arguments

• &K - Shared reference to a K.

Returns

• Option<V> - Some(...) on success, None otherwise.

pub fn clear(&mut self)

Removes every entry from the cache.

pub fn iter(&self) -> impl Iterator<Item = (&K, &V)>

Returns an iterator over the entries in most-recently-used-first order.

Returns

• impl Iterator<Item - A impl Iterator<Item value.

pub fn keys(&self) -> impl Iterator<Item = &K>

Returns an iterator over the keys in most-recently-used-first order.

Returns

• impl Iterator<Item - A impl Iterator<Item value.

pub fn values(&self) -> impl Iterator<Item = &V>

Returns an iterator over the values in most-recently-used-first order.

Returns

• impl Iterator<Item - A impl Iterator<Item value.

pub fn resize(&mut self, new_capacity: usize)

Resizes the cache to a new capacity.

If the new capacity is smaller than the current size, the least-recently-used entries are evicted until the cache fits.

Arguments

• usize - A non-negative integer (usize).

impl<K, V> LruCache<K, V>

where K: Clone + Eq + Hash,

pub fn get_mut_capacity(&mut self) -> &mut usize

pub fn set_capacity(&mut self, val: usize) -> &mut Self

pub fn get_map(&self) -> &HashMap<K, V>

pub fn get_mut_map(&mut self) -> &mut HashMap<K, V>

pub fn set_map(&mut self, val: HashMap<K, V>) -> &mut Self

pub fn get_order(&self) -> &VecDeque<K>

pub fn get_mut_order(&mut self) -> &mut VecDeque<K>

pub fn set_order(&mut self, val: VecDeque<K>) -> &mut Self

impl<K, V> LruCache<K, V>

where K: Clone + Eq + Hash,

pub fn new(capacity: usize) -> Self

Trait Implementations

impl<K, V: Clone> Clone for LruCache<K, V>

where K: Clone + Eq + Hash + Clone,

fn clone(&self) -> LruCache<K, V>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

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

where K: Clone + Eq + Hash + Debug,

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

Formats the value using the given formatter.