Struct Lru

pub struct Lru<K, V> {
    evict_fn: Box<dyn Fn(K, V, usize) + Send>,
    capacity: Weight,
    next_time: Time,
    entries: HashMap<K, (V, Weight, Time)>,
    by_time: BTreeMap<Time, K>,
    total_weight: Weight,
}

A weighted cache, evicting the least recently used entries.

This is reimplemented here, instead of using an existing crate, because existing options seem to either not support weights or they use unsafe.

Fields

evict_fn: Box<dyn Fn(K, V, usize) + Send>

capacity: Weight

next_time: Time

entries: HashMap<K, (V, Weight, Time)>

by_time: BTreeMap<Time, K>

total_weight: Weight

Implementations

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

pub fn new<F>(capacity: usize, evict_fn: F) -> Self

where F: Fn(K, V, usize) + Send + 'static,

Returns a new Lru with the requested configuration.

evict_fn is called for every entry evicted by the least recently used policy. It is not called for entries replaced by the same key in insert nor entries explictly removed by remove.

pub fn capacity(&self) -> usize

Returns the capacity of the cache.

pub fn entry_count(&self) -> usize

Returns the total number of entries in the cache.

pub fn entry_weight(&self) -> usize

Returns the sum of weights of entries in the cache.

pub fn update_capacity(&mut self, capacity: usize)

Changes the weighted capacity of the cache, evicting as necessary if the new value is smaller.

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

where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns a reference to entry with the given key, if present, marking it as most recently used.

pub fn insert(&mut self, key: K, val: V, weight: usize)

Inserts the given key and value into the cache, marking it as most recently used.

If the key already exists in the cache, the existing value and weight are first removed.

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

where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Removes the entry with the given key from the cache, if present.

Returns None if the entry was not in the cache.

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

Returns an iterator over the entries in the cache in order from most recently used to least.

fn insert_not_exists(&mut self, key: K, val: V, weight: Weight)

fn remove_exists(&mut self, time: Time) -> (K, V, Weight)

fn resize(&mut self)

Trait Implementations

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

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

Formats the value using the given formatter.