mirror of
https://github.com/ceph/ceph-csi.git
synced 2024-11-23 14:50:24 +00:00
134 lines
3.0 KiB
Go
134 lines
3.0 KiB
Go
/*
|
|
Copyright 2013 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 lru implements an LRU cache.
|
|
package lru
|
|
|
|
import "container/list"
|
|
|
|
// Cache is an LRU cache. It is not safe for concurrent access.
|
|
type Cache struct {
|
|
// MaxEntries is the maximum number of cache entries before
|
|
// an item is evicted. Zero means no limit.
|
|
MaxEntries int
|
|
|
|
// OnEvicted optionally specifies a callback function to be
|
|
// executed when an entry is purged from the cache.
|
|
OnEvicted func(key Key, value interface{})
|
|
|
|
ll *list.List
|
|
cache map[interface{}]*list.Element
|
|
}
|
|
|
|
// A Key may be any value that is comparable. See http://golang.org/ref/spec#Comparison_operators
|
|
type Key interface{}
|
|
|
|
type entry struct {
|
|
key Key
|
|
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 New(maxEntries int) *Cache {
|
|
return &Cache{
|
|
MaxEntries: maxEntries,
|
|
ll: list.New(),
|
|
cache: make(map[interface{}]*list.Element),
|
|
}
|
|
}
|
|
|
|
// Add adds a value to the cache.
|
|
func (c *Cache) Add(key Key, value interface{}) {
|
|
if c.cache == nil {
|
|
c.cache = make(map[interface{}]*list.Element)
|
|
c.ll = list.New()
|
|
}
|
|
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()
|
|
}
|
|
}
|
|
|
|
// Get looks up a key's value from the cache.
|
|
func (c *Cache) Get(key Key) (value interface{}, ok bool) {
|
|
if c.cache == nil {
|
|
return
|
|
}
|
|
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 Key) {
|
|
if c.cache == nil {
|
|
return
|
|
}
|
|
if ele, hit := c.cache[key]; hit {
|
|
c.removeElement(ele)
|
|
}
|
|
}
|
|
|
|
// RemoveOldest removes the oldest item from the cache.
|
|
func (c *Cache) RemoveOldest() {
|
|
if c.cache == nil {
|
|
return
|
|
}
|
|
ele := c.ll.Back()
|
|
if ele != nil {
|
|
c.removeElement(ele)
|
|
}
|
|
}
|
|
|
|
func (c *Cache) removeElement(e *list.Element) {
|
|
c.ll.Remove(e)
|
|
kv := e.Value.(*entry)
|
|
delete(c.cache, kv.key)
|
|
if c.OnEvicted != nil {
|
|
c.OnEvicted(kv.key, kv.value)
|
|
}
|
|
}
|
|
|
|
// Len returns the number of items in the cache.
|
|
func (c *Cache) Len() int {
|
|
if c.cache == nil {
|
|
return 0
|
|
}
|
|
return c.ll.Len()
|
|
}
|
|
|
|
// Clear purges all stored items from the cache.
|
|
func (c *Cache) Clear() {
|
|
if c.OnEvicted != nil {
|
|
for _, e := range c.cache {
|
|
kv := e.Value.(*entry)
|
|
c.OnEvicted(kv.key, kv.value)
|
|
}
|
|
}
|
|
c.ll = nil
|
|
c.cache = nil
|
|
}
|