mirror of
https://github.com/ceph/ceph-csi.git
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84 lines
1.9 KiB
Go
84 lines
1.9 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package cache
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import (
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"sync"
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)
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const (
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shardsCount int = 32
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)
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type Cache []*cacheShard
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func NewCache(maxSize int) Cache {
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if maxSize < shardsCount {
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maxSize = shardsCount
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}
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cache := make(Cache, shardsCount)
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for i := 0; i < shardsCount; i++ {
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cache[i] = &cacheShard{
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items: make(map[uint64]interface{}),
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maxSize: maxSize / shardsCount,
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}
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}
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return cache
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}
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func (c Cache) getShard(index uint64) *cacheShard {
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return c[index%uint64(shardsCount)]
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}
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// Returns true if object already existed, false otherwise.
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func (c *Cache) Add(index uint64, obj interface{}) bool {
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return c.getShard(index).add(index, obj)
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}
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func (c *Cache) Get(index uint64) (obj interface{}, found bool) {
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return c.getShard(index).get(index)
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}
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type cacheShard struct {
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items map[uint64]interface{}
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sync.RWMutex
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maxSize int
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}
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// Returns true if object already existed, false otherwise.
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func (s *cacheShard) add(index uint64, obj interface{}) bool {
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s.Lock()
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defer s.Unlock()
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_, isOverwrite := s.items[index]
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if !isOverwrite && len(s.items) >= s.maxSize {
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var randomKey uint64
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for randomKey = range s.items {
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break
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}
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delete(s.items, randomKey)
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}
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s.items[index] = obj
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return isOverwrite
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}
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func (s *cacheShard) get(index uint64) (obj interface{}, found bool) {
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s.RLock()
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defer s.RUnlock()
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obj, found = s.items[index]
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return
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}
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