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/
lru-cache.go
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/
lru-cache.go
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// Copyright Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package backend
import "container/list"
type LRUCache struct {
MaxEntries int
ll *list.List
cache map[interface{}]*list.Element
}
type Key interface{}
type entry struct {
key Key
value interface{}
}
func NewLRUCache(maxEntries int) *LRUCache {
return &LRUCache{
MaxEntries: maxEntries,
ll: list.New(),
cache: make(map[interface{}]*list.Element),
}
}
func (c *LRUCache) Add(key Key, value interface{}) {
if ee, ok := c.cache[key]; ok {
c.ll.MoveToFront(ee)
ee.Value.(*entry).value = value
return
}
ele := c.ll.PushFront(&entry{key, value})
c.cache[key] = ele
if c.MaxEntries != 0 && c.ll.Len() > c.MaxEntries {
c.RemoveOldest()
}
}
func (c *LRUCache) Get(key Key) (value interface{}, ok bool) {
if ele, hit := c.cache[key]; hit {
c.ll.MoveToFront(ele)
return ele.Value.(*entry).value, true
}
return
}
func (c *LRUCache) Remove(key Key) {
if ele, hit := c.cache[key]; hit {
c.removeElement(ele)
}
}
func (c *LRUCache) RemoveOldest() {
ele := c.ll.Back()
if ele != nil {
c.removeElement(ele)
}
}
func (c *LRUCache) removeElement(e *list.Element) {
c.ll.Remove(e)
kv := e.Value.(*entry)
delete(c.cache, kv.key)
}
func (c *LRUCache) Len() int {
return c.ll.Len()
}