package cache import ( "container/list" "sync" ) // Lru simple, fast lru cache implementation type Lru interface { Get(key interface{}) (value interface{}, ok bool) GetKeyFromValue(value interface{}) (key interface{}, ok bool) Put(key, value interface{}) } type lru struct { capacity int doubleLinkedlist *list.List keyToElement *sync.Map valueToElement *sync.Map mu *sync.Mutex } type lruElement struct { key interface{} value interface{} } // NewLru initializes a lru cache func NewLru(cap int) Lru { return &lru{ capacity: cap, doubleLinkedlist: list.New(), keyToElement: new(sync.Map), valueToElement: new(sync.Map), mu: new(sync.Mutex), } } func (l *lru) Get(key interface{}) (value interface{}, ok bool) { l.mu.Lock() defer l.mu.Unlock() if v, ok := l.keyToElement.Load(key); ok { element := v.(*list.Element) l.doubleLinkedlist.MoveToFront(element) return element.Value.(*lruElement).value, true } return nil, false } func (l *lru) GetKeyFromValue(value interface{}) (key interface{}, ok bool) { l.mu.Lock() defer l.mu.Unlock() if k, ok := l.valueToElement.Load(value); ok { element := k.(*list.Element) l.doubleLinkedlist.MoveToFront(element) return element.Value.(*lruElement).key, true } return nil, false } func (l *lru) Put(key, value interface{}) { l.mu.Lock() e := &lruElement{key, value} if v, ok := l.keyToElement.Load(key); ok { element := v.(*list.Element) element.Value = e l.doubleLinkedlist.MoveToFront(element) } else { element := l.doubleLinkedlist.PushFront(e) l.keyToElement.Store(key, element) l.valueToElement.Store(value, element) if l.doubleLinkedlist.Len() > l.capacity { toBeRemove := l.doubleLinkedlist.Back() l.doubleLinkedlist.Remove(toBeRemove) l.keyToElement.Delete(toBeRemove.Value.(*lruElement).key) l.valueToElement.Delete(toBeRemove.Value.(*lruElement).value) } } l.mu.Unlock() }