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## Addresses #15999 - [x] Added/updated tests - [ ] Manual QA for all new/changed functionality --------- Co-authored-by: Jacob Shandling <jacob@fleetdm.com>
84 lines
2.1 KiB
Go
84 lines
2.1 KiB
Go
// Copyright (c) Facebook, Inc. and its affiliates.
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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 cvefeed
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import (
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"container/heap"
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"time"
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)
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type evictionData struct {
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key string // which key in Cache.data refers to it
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index int // the index of item on the heap
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access time.Time // last access time
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}
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// evictionQueue is a priority queue for LRU cache
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type evictionQueue struct {
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q evictionHeap
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}
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// pop pops next key to evict
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func (eq *evictionQueue) pop() string {
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if eq.q.Len() > 0 {
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return heap.Pop(&eq.q).(*evictionData).key
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}
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return ""
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}
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// push pushes a key onto heap, returns the index item ended up at.
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func (eq *evictionQueue) push(key string) int {
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index := eq.q.Len()
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ed := &evictionData{
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key: key,
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index: index,
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access: time.Now(),
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}
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heap.Push(&eq.q, ed)
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return ed.index
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}
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// touch updates the access time of the item at index, returns the new index of that item.
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func (eq *evictionQueue) touch(index int) int {
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ed := eq.q[index]
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ed.access = time.Now()
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heap.Fix(&eq.q, index)
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return ed.index
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}
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// evictionHeap is a slice of evictionData that implements heap.Interface
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type evictionHeap []*evictionData
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func (eh evictionHeap) Len() int { return len(eh) }
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func (eh evictionHeap) Less(i, j int) bool { return eh[i].access.Before(eh[j].access) }
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func (eh evictionHeap) Swap(i, j int) {
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eh[i], eh[j] = eh[j], eh[i]
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eh[i].index, eh[j].index = i, j
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}
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func (eh *evictionHeap) Push(x interface{}) {
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ed := x.(*evictionData)
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ed.index = len(*eh)
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*eh = append(*eh, ed)
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}
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func (eh *evictionHeap) Pop() interface{} {
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old := *eh
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ed := old[len(old)-1]
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*eh = old[:len(old)-1]
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return ed
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}
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