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66 lines
1.6 KiB
66 lines
1.6 KiB
// Copyright 2014 The Cayley Authors. All rights reserved.
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//
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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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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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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package mongo
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import (
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"container/list"
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)
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// TODO(kortschak) Reimplement without container/list.
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// cache implements an LRU cache.
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type cache struct {
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cache map[string]*list.Element
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priority *list.List
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maxSize int
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}
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type kv struct {
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key string
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value interface{}
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}
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func newCache(size int) *cache {
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var lru cache
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lru.maxSize = size
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lru.priority = list.New()
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lru.cache = make(map[string]*list.Element)
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return &lru
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}
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func (lru *cache) Put(key string, value interface{}) {
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if _, ok := lru.Get(key); ok {
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return
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}
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if len(lru.cache) == lru.maxSize {
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lru.removeOldest()
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}
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lru.priority.PushFront(kv{key: key, value: value})
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lru.cache[key] = lru.priority.Front()
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}
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func (lru *cache) Get(key string) (interface{}, bool) {
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if element, ok := lru.cache[key]; ok {
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lru.priority.MoveToFront(element)
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return element.Value.(kv).value, true
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}
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return nil, false
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}
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func (lru *cache) removeOldest() {
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last := lru.priority.Remove(lru.priority.Back())
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delete(lru.cache, last.(kv).key)
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}
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