prometheus/utility/cache.go
Matt T. Proud 1e37b23a17 Extract LRUCache into generic cache type.
Change-Id: I402da4de408a44457daeec7497d2393c5f65ab66
2013-08-17 13:57:49 +02:00

177 lines
3.6 KiB
Go

// Copyright 2013 Prometheus Team
// 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 utility
import (
"container/list"
"sync"
)
type Cache interface {
Put(k, v interface{}) (replaced bool, err error)
PutIfAbsent(k, v interface{}) (put bool, err error)
Get(k interface{}) (v interface{}, ok bool, err error)
Has(k interface{}) (ok bool, err error)
Delete(k interface{}) (deleted bool, err error)
Clear() (cleared bool, err error)
}
type LRUCache struct {
list *list.List
table map[interface{}]*list.Element
limit uint
size uint
}
func NewLRUCache(limit uint) *LRUCache {
return &LRUCache{
list: list.New(),
table: map[interface{}]*list.Element{},
limit: limit,
}
}
func (c *LRUCache) Has(k interface{}) (has bool, err error) {
_, ok := c.table[k]
return ok, nil
}
func (c *LRUCache) Get(k interface{}) (v interface{}, ok bool, err error) {
element, ok := c.table[k]
if !ok {
return nil, false, nil
}
c.moveToFront(element)
return element.Value, true, nil
}
func (c *LRUCache) Put(k, v interface{}) (replaced bool, err error) {
element, ok := c.table[k]
if ok {
c.updateInplace(element, v)
return true, nil
}
c.addNew(k, v)
return false, nil
}
func (c *LRUCache) PutIfAbsent(k, v interface{}) (put bool, err error) {
if _, ok := c.table[k]; ok {
return false, nil
}
c.addNew(k, v)
return true, nil
}
func (c *LRUCache) Delete(k interface{}) (deleted bool, err error) {
element, ok := c.table[k]
if !ok {
return false, nil
}
c.list.Remove(element)
delete(c.table, k)
return true, nil
}
func (c *LRUCache) Clear() (cleared bool, err error) {
c.list.Init()
c.table = map[interface{}]*list.Element{}
c.size = 0
return true, nil
}
func (c *LRUCache) updateInplace(e *list.Element, v interface{}) {
e.Value = v
c.moveToFront(e)
c.checkCapacity()
}
func (c *LRUCache) moveToFront(e *list.Element) {
c.list.MoveToFront(e)
}
func (c *LRUCache) addNew(k, v interface{}) {
c.table[k] = c.list.PushFront(v)
c.checkCapacity()
}
func (c *LRUCache) checkCapacity() {
for c.size > c.limit {
delElem := c.list.Back()
v := delElem.Value
c.list.Remove(delElem)
delete(c.table, v)
}
}
type SynchronizedCache struct {
mu sync.Mutex
c Cache
}
func (c *SynchronizedCache) Put(k, v interface{}) (replaced bool, err error) {
c.mu.Lock()
defer c.mu.Unlock()
return c.c.Put(k, v)
}
func (c *SynchronizedCache) PutIfAbsent(k, v interface{}) (put bool, err error) {
c.mu.Lock()
defer c.mu.Unlock()
return c.PutIfAbsent(k, v)
}
func (c *SynchronizedCache) Get(k interface{}) (v interface{}, ok bool, err error) {
c.mu.Lock()
defer c.mu.Unlock()
return c.c.Get(k)
}
func (c *SynchronizedCache) Has(k interface{}) (ok bool, err error) {
c.mu.Lock()
defer c.mu.Unlock()
return c.c.Has(k)
}
func (c *SynchronizedCache) Delete(k interface{}) (deleted bool, err error) {
c.mu.Lock()
defer c.mu.Unlock()
return c.c.Delete(k)
}
func (c *SynchronizedCache) Clear() (cleared bool, err error) {
c.mu.Lock()
defer c.mu.Unlock()
return c.c.Clear()
}
func NewSynchronizedCache(c Cache) *SynchronizedCache {
return &SynchronizedCache{
c: c,
}
}