Struct lru_cache::LruCache

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pub struct LruCache<K: Eq + Hash, V, S: BuildHasher = RandomState> { /* private fields */ }

Expand description

An LRU cache.

Implementations§

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impl<K: Eq + Hash, V> LruCache<K, V>

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pub fn new(capacity: usize) -> Self

Creates an empty cache that can hold at most capacity items.

§Examples

use lru_cache::LruCache;
let mut cache: LruCache<i32, &str> = LruCache::new(10);

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impl<K: Eq + Hash, V, S: BuildHasher> LruCache<K, V, S>

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pub fn with_hasher(capacity: usize, hash_builder: S) -> Self

Creates an empty cache that can hold at most capacity items with the given hash builder.

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pub fn contains_key<Q>(&mut self, key: &Q) -> bool
where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Checks if the map contains the given key.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(1);

cache.insert(1, "a");
assert_eq!(cache.contains_key(&1), true);

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pub fn insert(&mut self, k: K, v: V) -> Option<V>

Inserts a key-value pair into the cache. If the key already existed, the old value is returned.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(2);

cache.insert(1, "a");
cache.insert(2, "b");
assert_eq!(cache.get_mut(&1), Some(&mut "a"));
assert_eq!(cache.get_mut(&2), Some(&mut "b"));

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pub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns a mutable reference to the value corresponding to the given key in the cache, if any.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(2);

cache.insert(1, "a");
cache.insert(2, "b");
cache.insert(2, "c");
cache.insert(3, "d");

assert_eq!(cache.get_mut(&1), None);
assert_eq!(cache.get_mut(&2), Some(&mut "c"));

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pub fn remove<Q>(&mut self, k: &Q) -> Option<V>
where K: Borrow<Q>, Q: Hash + Eq + ?Sized,

Removes the given key from the cache and returns its corresponding value.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(2);

cache.insert(2, "a");

assert_eq!(cache.remove(&1), None);
assert_eq!(cache.remove(&2), Some("a"));
assert_eq!(cache.remove(&2), None);
assert_eq!(cache.len(), 0);

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pub fn capacity(&self) -> usize

Returns the maximum number of key-value pairs the cache can hold.

§Examples

use lru_cache::LruCache;
let mut cache: LruCache<i32, &str> = LruCache::new(2);
assert_eq!(cache.capacity(), 2);

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

Sets the number of key-value pairs the cache can hold. Removes least-recently-used key-value pairs if necessary.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(2);

cache.insert(1, "a");
cache.insert(2, "b");
cache.insert(3, "c");

assert_eq!(cache.get_mut(&1), None);
assert_eq!(cache.get_mut(&2), Some(&mut "b"));
assert_eq!(cache.get_mut(&3), Some(&mut "c"));

cache.set_capacity(3);
cache.insert(1, "a");
cache.insert(2, "b");

assert_eq!(cache.get_mut(&1), Some(&mut "a"));
assert_eq!(cache.get_mut(&2), Some(&mut "b"));
assert_eq!(cache.get_mut(&3), Some(&mut "c"));

cache.set_capacity(1);

assert_eq!(cache.get_mut(&1), None);
assert_eq!(cache.get_mut(&2), None);
assert_eq!(cache.get_mut(&3), Some(&mut "c"));

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pub fn remove_lru(&mut self) -> Option<(K, V)>

Removes and returns the least recently used key-value pair as a tuple.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(2);

cache.insert(1, "a");
cache.insert(2, "b");

assert_eq!(cache.remove_lru(), Some((1, "a")));
assert_eq!(cache.len(), 1);

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pub fn len(&self) -> usize

Returns the number of key-value pairs in the cache.

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pub fn is_empty(&self) -> bool

Returns true if the cache contains no key-value pairs.

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pub fn clear(&mut self)

Removes all key-value pairs from the cache.

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pub fn iter(&self) -> Iter<'_, K, V> ⓘ

Returns an iterator over the cache’s key-value pairs in least- to most-recently-used order.

Accessing the cache through the iterator does not affect the cache’s LRU state.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(2);

cache.insert(1, 10);
cache.insert(2, 20);
cache.insert(3, 30);

let kvs: Vec<_> = cache.iter().collect();
assert_eq!(kvs, [(&2, &20), (&3, &30)]);

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pub fn iter_mut(&mut self) -> IterMut<'_, K, V> ⓘ

Returns an iterator over the cache’s key-value pairs in least- to most-recently-used order, with mutable references to the values.

Accessing the cache through the iterator does not affect the cache’s LRU state.

§Examples

use lru_cache::LruCache;

let mut cache = LruCache::new(2);

cache.insert(1, 10);
cache.insert(2, 20);
cache.insert(3, 30);

let mut n = 2;

for (k, v) in cache.iter_mut() {
    assert_eq!(*k, n);
    assert_eq!(*v, n * 10);
    *v *= 10;
    n += 1;
}

assert_eq!(n, 4);
assert_eq!(cache.get_mut(&2), Some(&mut 200));
assert_eq!(cache.get_mut(&3), Some(&mut 300));