49 lines
1.1 KiB
Dart
49 lines
1.1 KiB
Dart
import 'dart:collection';
|
|
|
|
class LRUCache<K, V> {
|
|
int _capacity;
|
|
final LinkedHashMap<K, V> _cache;
|
|
|
|
LRUCache(
|
|
this._capacity, {
|
|
bool Function(K, K)? equals,
|
|
int Function(K)? hashCode,
|
|
bool Function(dynamic)? isValidKey,
|
|
}) : _cache = LinkedHashMap<K, V>(
|
|
equals: equals,
|
|
hashCode: hashCode,
|
|
isValidKey: isValidKey,
|
|
);
|
|
|
|
void resize(int capacity) {
|
|
if (_capacity > capacity) {
|
|
_cache.keys.take(_capacity - capacity).forEach(_cache.remove);
|
|
}
|
|
|
|
_capacity = capacity;
|
|
}
|
|
|
|
V? get(K key) {
|
|
final value = _cache.remove(key); // Temporarily remove the item.
|
|
|
|
if (value != null) {
|
|
_cache[key] =
|
|
value; // Re-inserting the item makes it the most-recently used.
|
|
}
|
|
|
|
return value;
|
|
}
|
|
|
|
V set(K key, V value) {
|
|
if (_cache.containsKey(key)) {
|
|
_cache.remove(key); // Remove the existing item before updating.
|
|
} else if (_cache.length == _capacity) {
|
|
_cache.remove(
|
|
_cache.keys.first,
|
|
); // Explicitly remove the least recently used item if at capacity.
|
|
}
|
|
|
|
return _cache[key] = value; // Inserting or updating the item.
|
|
}
|
|
}
|