func()

in lru.go [358:437]

• 58 lines of code
• 10 McCabe index (conditional complexity)

func (lru *LRU[K, V]) addWithLifetime(hash uint32, key K, value V,
	lifetime time.Duration) (evicted bool) {
	bucketPos, startPos := lru.hashToPos(hash)
	if startPos == emptyBucket {
		pos := lru.len

		if pos == lru.cap {
			// Capacity reached, evict the oldest entry and
			// store the new entry at evicted position.
			pos = lru.elements[lru.head].next
			lru.evict(pos)
			lru.metrics.Evictions++
			evicted = true
		}

		// insert new (first) entry into the bucket
		lru.buckets[bucketPos] = pos
		lru.elements[pos].bucketPos = bucketPos

		lru.elements[pos].nextBucket = pos
		lru.elements[pos].prevBucket = pos
		lru.insert(pos, key, value, lifetime)
		return evicted
	}

	// Walk through the bucket list to see whether key already exists.
	pos := startPos
	for {
		if lru.elements[pos].key == key {
			// Key exists, replace the value and update element to be the head element.
			lru.elements[pos].value = value
			lru.elements[pos].expire = expire(lifetime)

			if pos != lru.head {
				lru.unlinkElement(pos)
				lru.setHead(pos)
			}
			// count as insert, even if it's just an update
			lru.metrics.Inserts++
			return false
		}

		pos = lru.elements[pos].nextBucket
		if pos == startPos {
			// Key not found
			break
		}
	}

	pos = lru.len
	if pos == lru.cap {
		// Capacity reached, evict the oldest entry and
		// store the new entry at evicted position.
		pos = lru.elements[lru.head].next
		lru.evict(pos)
		lru.metrics.Evictions++
		evicted = true
		startPos = lru.buckets[bucketPos]
		if startPos == emptyBucket {
			startPos = pos
		}
	}

	// insert new entry into the existing bucket before startPos
	lru.buckets[bucketPos] = pos
	lru.elements[pos].bucketPos = bucketPos

	lru.elements[pos].nextBucket = startPos
	lru.elements[pos].prevBucket = lru.elements[startPos].prevBucket
	lru.elements[lru.elements[startPos].prevBucket].nextBucket = pos
	lru.elements[startPos].prevBucket = pos
	lru.insert(pos, key, value, lifetime)

	if lru.elements[pos].prevBucket != pos {
		// The bucket now contains more than 1 element.
		// That means we have a collision.
		lru.metrics.Collisions++
	}
	return evicted
}