| /* |
| Copyright 2014 The Kubernetes Authors. |
| |
| 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 cache |
| |
| import ( |
| "sync" |
| ) |
| |
| const ( |
| shardsCount int = 32 |
| ) |
| |
| type Cache []*cacheShard |
| |
| func NewCache(maxSize int) Cache { |
| if maxSize < shardsCount { |
| maxSize = shardsCount |
| } |
| cache := make(Cache, shardsCount) |
| for i := 0; i < shardsCount; i++ { |
| cache[i] = &cacheShard{ |
| items: make(map[uint64]interface{}), |
| maxSize: maxSize / shardsCount, |
| } |
| } |
| return cache |
| } |
| |
| func (c Cache) getShard(index uint64) *cacheShard { |
| return c[index%uint64(shardsCount)] |
| } |
| |
| // Returns true if object already existed, false otherwise. |
| func (c *Cache) Add(index uint64, obj interface{}) bool { |
| return c.getShard(index).add(index, obj) |
| } |
| |
| func (c *Cache) Get(index uint64) (obj interface{}, found bool) { |
| return c.getShard(index).get(index) |
| } |
| |
| type cacheShard struct { |
| items map[uint64]interface{} |
| sync.RWMutex |
| maxSize int |
| } |
| |
| // Returns true if object already existed, false otherwise. |
| func (s *cacheShard) add(index uint64, obj interface{}) bool { |
| s.Lock() |
| defer s.Unlock() |
| _, isOverwrite := s.items[index] |
| if !isOverwrite && len(s.items) >= s.maxSize { |
| var randomKey uint64 |
| for randomKey = range s.items { |
| break |
| } |
| delete(s.items, randomKey) |
| } |
| s.items[index] = obj |
| return isOverwrite |
| } |
| |
| func (s *cacheShard) get(index uint64) (obj interface{}, found bool) { |
| s.RLock() |
| defer s.RUnlock() |
| obj, found = s.items[index] |
| return |
| } |