Create & Init Project...

app/service/live/resource/lrucache/lrucache.go

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+package lrucache
+
+// Element - node to store cache item
+type Element struct {
+	prev, next *Element
+	Key        interface{}
+	Value      interface{}
+}
+
+// Next - fetch older element
+func (e *Element) Next() *Element {
+	return e.next
+}
+
+// Prev - fetch newer element
+func (e *Element) Prev() *Element {
+	return e.prev
+}
+
+// LRUCache - a data structure that is efficient to insert/fetch/delete cache items [both O(1) time complexity]
+type LRUCache struct {
+	cache    map[interface{}]*Element
+	head     *Element
+	tail     *Element
+	capacity int
+}
+
+// New - create a new lru cache object
+func New(capacity int) *LRUCache {
+	return &LRUCache{make(map[interface{}]*Element), nil, nil, capacity}
+}
+
+// Put - put a cache item into lru cache
+func (lc *LRUCache) Put(key interface{}, value interface{}) {
+	if e, ok := lc.cache[key]; ok {
+		e.Value = value
+		lc.refresh(e)
+		return
+	}
+
+	if lc.capacity == 0 {
+		return
+	} else if len(lc.cache) >= lc.capacity {
+		// evict the oldest item
+		delete(lc.cache, lc.tail.Key)
+		lc.remove(lc.tail)
+	}
+
+	e := &Element{nil, lc.head, key, value}
+	lc.cache[key] = e
+	if len(lc.cache) != 1 {
+		lc.head.prev = e
+	} else {
+		lc.tail = e
+	}
+	lc.head = e
+}
+
+// Get - get value of key from lru cache with result
+func (lc *LRUCache) Get(key interface{}) (interface{}, bool) {
+	if e, ok := lc.cache[key]; ok {
+		lc.refresh(e)
+		return e.Value, ok
+	}
+	return nil, false
+}
+
+// Delete - delete item by key from lru cache
+func (lc *LRUCache) Delete(key interface{}) {
+	if e, ok := lc.cache[key]; ok {
+		delete(lc.cache, key)
+		lc.remove(e)
+	}
+}
+
+// Range - calls f sequentially for each key and value present in the lru cache
+func (lc *LRUCache) Range(f func(key, value interface{}) bool) {
+	for i := lc.head; i != nil; i = i.Next() {
+		if !f(i.Key, i.Value) {
+			break
+		}
+	}
+}
+
+// Update - inplace update
+func (lc *LRUCache) Update(key interface{}, f func(value *interface{})) {
+	if e, ok := lc.cache[key]; ok {
+		f(&e.Value)
+		lc.refresh(e)
+	}
+}
+
+// Front - get front element of lru cache
+func (lc *LRUCache) Front() *Element {
+	return lc.head
+}
+
+// Back - get back element of lru cache
+func (lc *LRUCache) Back() *Element {
+	return lc.tail
+}
+
+// Len - length of lru cache
+func (lc *LRUCache) Len() int {
+	return len(lc.cache)
+}
+
+// Capacity - capacity of lru cache
+func (lc *LRUCache) Capacity() int {
+	return lc.capacity
+}
+
+func (lc *LRUCache) refresh(e *Element) {
+	if e.prev != nil {
+		e.prev.next = e.next
+		if e.next == nil {
+			lc.tail = e.prev
+		} else {
+			e.next.prev = e.prev
+		}
+		e.prev = nil
+		e.next = lc.head
+		lc.head.prev = e
+		lc.head = e
+	}
+}
+
+func (lc *LRUCache) remove(e *Element) {
+	if e.prev == nil {
+		lc.head = e.next
+	} else {
+		e.prev.next = e.next
+	}
+	if e.next == nil {
+		lc.tail = e.prev
+	} else {
+		e.next.prev = e.prev
+	}
+}