simple lru again

cache2go/lruttl.go

@@ -2,173 +2,104 @@ package cache2go
 
 import (
 	"container/list"
-	"sync"
 	"time"
 )
 
 // Cache is an LRU cache. It is not safe for concurrent access.
 type Cache struct {
-	mu sync.RWMutex
 	// MaxEntries is the maximum number of cache entries before
 	// an item is evicted. Zero means no limit.
-	maxEntries int
+	MaxEntries int
 
-	lruIndex   *list.List
-	ttlIndex   []*list.Element
-	cache      map[string]*entry
-	expiration time.Duration
+	ll    *list.List
+	cache map[string]*list.Element
 }
 
+// A Key may be any value that is comparable. See http://golang.org/ref/spec#Comparison_operators
+
 type entry struct {
-	element   *list.Element
-	value     interface{}
-	timestamp time.Time
+	key   string
+	value interface{}
 }
 
 // New creates a new Cache.
 // If maxEntries is zero, the cache has no limit and it's assumed
 // that eviction is done by the caller.
-func NewLRUTTL(maxEntries int, expire time.Duration) *Cache {
-	c := &Cache{
-		maxEntries: maxEntries,
-		expiration: expire,
-		lruIndex:   list.New(),
-		cache:      make(map[string]*entry),
-	}
-	if c.expiration > 0 {
-		c.ttlIndex = make([]*list.Element, 0)
-		go c.cleanExpired()
-	}
-	return c
-}
-
-// cleans expired entries performing minimal checks
-func (c *Cache) cleanExpired() {
-	for {
-		c.mu.RLock()
-		if len(c.ttlIndex) == 0 {
-			c.mu.RUnlock()
-			time.Sleep(c.expiration)
-			continue
-		}
-		e := c.ttlIndex[0]
-		c.mu.RUnlock()
-
-		en := c.cache[e.Value.(string)]
-		if time.Now().After(en.timestamp.Add(c.expiration)) {
-			c.mu.Lock()
-			c.removeElement(e)
-			c.mu.Unlock()
-		} else {
-			time.Sleep(time.Now().Sub(en.timestamp.Add(c.expiration)))
-		}
+func NewLRUTTL(maxEntries int, exp time.Duration) *Cache {
+	return &Cache{
+		MaxEntries: maxEntries,
+		ll:         list.New(),
+		cache:      make(map[string]*list.Element),
 	}
 }
 
-// Add adds a value to the cache
+// Add adds a value to the cache.
 func (c *Cache) Set(key string, value interface{}) {
-	c.mu.Lock()
 	if c.cache == nil {
-		c.cache = make(map[string]*entry)
-		c.lruIndex = list.New()
-		if c.expiration > 0 {
-			c.ttlIndex = make([]*list.Element, 0)
-		}
+		c.cache = make(map[string]*list.Element)
+		c.ll = list.New()
 	}
-
-	if en, ok := c.cache[key]; ok {
-		c.lruIndex.MoveToFront(en.element)
-		en.value = value
-		en.timestamp = time.Now()
-
-		c.mu.Unlock()
+	if ee, ok := c.cache[key]; ok {
+		c.ll.MoveToFront(ee)
+		ee.Value.(*entry).value = value
 		return
 	}
-	e := c.lruIndex.PushFront(key)
-	if c.expiration > 0 {
-		c.ttlIndex = append(c.ttlIndex, e)
-	}
-	c.cache[key] = &entry{element: e, value: value, timestamp: time.Now()}
-	c.mu.Unlock()
-
-	if c.maxEntries != 0 && c.lruIndex.Len() > c.maxEntries {
+	ele := c.ll.PushFront(&entry{key, value})
+	c.cache[key] = ele
+	if c.MaxEntries != 0 && c.ll.Len() > c.MaxEntries {
 		c.RemoveOldest()
 	}
 }
 
 // Get looks up a key's value from the cache.
 func (c *Cache) Get(key string) (value interface{}, ok bool) {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
 	if c.cache == nil {
 		return
 	}
-	if en, hit := c.cache[key]; hit {
-		c.lruIndex.MoveToFront(en.element)
-		return en.value, true
+	if ele, hit := c.cache[key]; hit {
+		c.ll.MoveToFront(ele)
+		return ele.Value.(*entry).value, true
 	}
 	return
 }
 
 // Remove removes the provided key from the cache.
 func (c *Cache) Remove(key string) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
 	if c.cache == nil {
 		return
 	}
-	if en, hit := c.cache[key]; hit {
-		c.removeElement(en.element)
+	if ele, hit := c.cache[key]; hit {
+		c.removeElement(ele)
 	}
 }
 
 // RemoveOldest removes the oldest item from the cache.
 func (c *Cache) RemoveOldest() {
-	c.mu.Lock()
-	defer c.mu.Unlock()
 	if c.cache == nil {
 		return
 	}
-	e := c.lruIndex.Back()
-	if e != nil {
-		c.removeElement(e)
+	ele := c.ll.Back()
+	if ele != nil {
+		c.removeElement(ele)
 	}
 }
 
 func (c *Cache) removeElement(e *list.Element) {
-	c.lruIndex.Remove(e)
-	if c.expiration > 0 {
-		for i, se := range c.ttlIndex {
-			if se == e {
-				//delete
-				copy(c.ttlIndex[i:], c.ttlIndex[i+1:])
-				c.ttlIndex[len(c.ttlIndex)-1] = nil
-				c.ttlIndex = c.ttlIndex[:len(c.ttlIndex)-1]
-				break
-			}
-		}
-	}
-	key := e.Value.(string)
-	delete(c.cache, key)
+	c.ll.Remove(e)
+	kv := e.Value.(*entry)
+	delete(c.cache, kv.key)
 }
 
 // Len returns the number of items in the cache.
 func (c *Cache) Len() int {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
 	if c.cache == nil {
 		return 0
 	}
-	return c.lruIndex.Len()
+	return c.ll.Len()
 }
 
 // empties the whole cache
 func (c *Cache) Flush() {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-	c.lruIndex = list.New()
-	if c.expiration > 0 {
-		c.ttlIndex = make([]*list.Element, 0)
-	}
-	c.cache = make(map[string]*entry)
+	c.ll = list.New()
+	c.cache = make(map[string]*list.Element)
 }