first commit

lrucache/lrucache.go

@@ -0,0 +1,60 @@
+package lrucache
+
+import (
+	"container/list"
+)
+
+type Creator func(key string) interface{}
+
+type cacheKey struct {
+	Value                interface{}
+	DoubleLinkedListNode *list.Element
+}
+
+type LRUCache struct {
+	cache   map[string]*cacheKey
+	ddl     *list.List
+	creator Creator
+	length  int
+}
+
+func New(creator Creator, length int) *LRUCache {
+	return &LRUCache{
+		cache:   make(map[string]*cacheKey),
+		creator: creator,
+		ddl:     new(list.List).Init(),
+		length:  length,
+	}
+}
+
+func (lru *LRUCache) add(key string, val interface{}) interface{} {
+	lru.ddl.PushFront(key)
+	lru.cache[key] = &cacheKey{val, lru.ddl.Front()}
+	return val
+}
+
+func (lru *LRUCache) Size() int {
+	return len(lru.cache)
+}
+
+func (lru *LRUCache) removeExtraKeys() {
+	if lru.ddl.Len() < lru.length {
+		return
+	}
+	for e := lru.ddl.Back(); lru.ddl.Len() > lru.length; {
+		delete(lru.cache, e.Value.(string))
+		be := e.Prev()
+		lru.ddl.Remove(e)
+		e = be
+	}
+}
+
+func (lru *LRUCache) Get(key string) interface{} {
+	if val, ok := lru.cache[key]; ok {
+		lru.ddl.MoveToFront(val.DoubleLinkedListNode)
+		return val.Value
+	}
+	ret := lru.add(key, lru.creator(key))
+	lru.removeExtraKeys()
+	return ret
+}