Function NewLRU

internal/lru/lru.go:52–94

NewLRU returns a new thread-safe cache with expirable entries. Size parameter set to 0 makes cache of unlimited size, e.g. turns LRU mechanism off. Providing 0 TTL turns expiring off. Delete expired entries every 1/100th of ttl value. Goroutine which deletes expired entries runs indefinitely.

(size int, onEvict EvictCallback[K, V], ttl time.Duration)

//
// Delete expired entries every 1/100th of ttl value. Goroutine which deletes expired entries runs indefinitely.
func NewLRU[K comparable, V any](size int, onEvict EvictCallback[K, V], ttl time.Duration) *LRU[K, V] {
	if size < 0 {
		size = 0
	}
	if ttl <= 0 {
		ttl = noEvictionTTL
	}

	res := LRU[K, V]{
		ttl:       ttl,
		size:      size,
		evictList: NewList[K, V](),
		items:     make(map[K]*Entry[K, V]),
		onEvict:   onEvict,
		done:      make(chan struct{}),
	}

	// initialize the buckets
	res.buckets = make([]bucket[K, V], numBuckets)
	for i := 0; i < numBuckets; i++ {
		res.buckets[i] = bucket[K, V]{entries: make(map[K]*Entry[K, V])}
	}

	// enable deleteExpired() running in separate goroutine for cache with non-zero TTL
	//
	// Important: done channel is never closed, so deleteExpired() goroutine will never exit,
	// it's decided to add functionality to close it in the version later than v2.
	if res.ttl != noEvictionTTL {
		go func(done <-chan struct{}) {
			ticker := time.NewTicker(res.ttl / numBuckets)
			defer ticker.Stop()
			for {
				select {
				case <-done:
					return
				case <-ticker.C:
					res.deleteExpired()
				}
			}
		}(res.done)
	}
	return &res
}

// Purge clears the cache completely.
// onEvict is called for each evicted key.