clair/vendor/github.com/google/cayley/graph/mongo/lru.go

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2015-11-13 19:11:28 +00:00
// Copyright 2014 The Cayley Authors. All rights reserved.
//
// 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 mongo
import (
"container/list"
)
// TODO(kortschak) Reimplement without container/list.
// cache implements an LRU cache.
type cache struct {
cache map[string]*list.Element
priority *list.List
maxSize int
}
type kv struct {
key string
value interface{}
}
func newCache(size int) *cache {
var lru cache
lru.maxSize = size
lru.priority = list.New()
lru.cache = make(map[string]*list.Element)
return &lru
}
func (lru *cache) Put(key string, value interface{}) {
if _, ok := lru.Get(key); ok {
return
}
if len(lru.cache) == lru.maxSize {
lru.removeOldest()
}
lru.priority.PushFront(kv{key: key, value: value})
lru.cache[key] = lru.priority.Front()
}
func (lru *cache) Get(key string) (interface{}, bool) {
if element, ok := lru.cache[key]; ok {
lru.priority.MoveToFront(element)
return element.Value.(kv).value, true
}
return nil, false
}
func (lru *cache) removeOldest() {
last := lru.priority.Remove(lru.priority.Back())
delete(lru.cache, last.(kv).key)
}