Struct lru::LruCache

pub struct LruCache<K, V, S = RandomState> { /* private fields */ }

An LRU Cache

Implementations

impl<K: Hash + Eq, V> LruCache<K, V>

pub fn new(cap: usize) -> LruCache<K, V>

Creates a new LRU Cache that holds at most cap items.

Example

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

pub fn unbounded() -> LruCache<K, V>

Creates a new LRU Cache that never automatically evicts items.

Example

use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::unbounded();

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

pub fn with_hasher(cap: usize, hash_builder: S) -> LruCache<K, V, S>

Creates a new LRU Cache that holds at most cap items and uses the providedash builder to hash keys.

Example

use std::collections::HashMap;
use std::collections::hash_map::RandomState;
use lru::LruCache;

let s = RandomState::new();
let mut cache: LruCache<isize, &str> = LruCache::with_hasher(10, s);

pub fn put(&mut self, k: K, v: V)

Puts a key-value pair into cache. If the key already exists it updates its value.

Example

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

cache.put(1, "a");
cache.put(2, "b");
assert_eq!(cache.get(&1), Some(&"a"));
assert_eq!(cache.get(&2), Some(&"b"));

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

Returns a reference to the value of the key in the cache or None if it is not present in the cache. Moves the key to the head of the LRU list if it exists.

Example

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

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

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

pub fn get_mut<'a>(&'a mut self, k: &K) -> Option<&'a mut V>

Returns a mutable reference to the value of the key in the cache or None if it is not present in the cache. Moves the key to the head of the LRU list if it exists.

Example

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

cache.put("apple", 8);
cache.put("banana", 4);
cache.put("banana", 6);
cache.put("pear", 2);

assert_eq!(cache.get_mut(&"apple"), None);
assert_eq!(cache.get_mut(&"banana"), Some(&mut 6));
assert_eq!(cache.get_mut(&"pear"), Some(&mut 2));

pub fn peek<'a>(&'a self, k: &K) -> Option<&'a V>

Returns the value corresponding to the key in the cache or None if it is not present in the cache. Unlike get, peek does not update the LRU list so the key’s position will be unchanged.

Example

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

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

assert_eq!(cache.peek(&1), Some(&"a"));
assert_eq!(cache.peek(&2), Some(&"b"));

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

Returns a bool indicating whether the given key is in the cache. Does not update the LRU list.

Example

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

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

assert!(!cache.contains(&1));
assert!(cache.contains(&2));
assert!(cache.contains(&3));

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

Removes and returns the value corresponding to the key from the cache or None if it does not exist.

Example

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

cache.put(2, "a");

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

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

Removes and returns the key and value corresponding to the least recently used item or None if the cache is empty.

Example

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

cache.put(2, "a");
cache.put(3, "b");
cache.put(4, "c");
cache.get(&3);

assert_eq!(cache.pop_lru(), Some((4, "c")));
assert_eq!(cache.pop_lru(), Some((3, "b")));
assert_eq!(cache.pop_lru(), None);
assert_eq!(cache.len(), 0);

pub fn len(&self) -> usize

Returns the number of key-value pairs that are currently in the the cache.

Example

use lru::LruCache;
let mut cache = LruCache::new(2);
assert_eq!(cache.len(), 0);

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

cache.put(2, "b");
assert_eq!(cache.len(), 2);

cache.put(3, "c");
assert_eq!(cache.len(), 2);

pub fn is_empty(&self) -> bool

Returns a bool indicating whether the cache is empty or not.

Example

use lru::LruCache;
let mut cache = LruCache::new(2);
assert!(cache.is_empty());

cache.put(1, "a");
assert!(!cache.is_empty());

pub fn cap(&self) -> usize

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

Example

use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::new(2);
assert_eq!(cache.cap(), 2);

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

Resizes the cache. If the new capacity is smaller than the size of the current cache any entries past the new capacity are discarded.

Example

use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::new(2);

cache.put(1, "a");
cache.put(2, "b");
cache.resize(4);
cache.put(3, "c");
cache.put(4, "d");

assert_eq!(cache.len(), 4);
assert_eq!(cache.get(&1), Some(&"a"));
assert_eq!(cache.get(&2), Some(&"b"));
assert_eq!(cache.get(&3), Some(&"c"));
assert_eq!(cache.get(&4), Some(&"d"));

pub fn clear(&mut self)

Clears the contents of the cache.

Example

use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::new(2);
assert_eq!(cache.len(), 0);

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

cache.put(2, "b");
assert_eq!(cache.len(), 2);

cache.clear();
assert_eq!(cache.len(), 0);

Trait Implementations

impl<K, V, S> Drop for LruCache<K, V, S>

fn drop(&mut self)

Executes the destructor for this type.

impl<K: Sync + Send, V: Sync + Send> Send for LruCache<K, V>

impl<K: Sync + Send, V: Sync + Send> Sync for LruCache<K, V>