107 lines
1.7 KiB
Go
107 lines
1.7 KiB
Go
package lru
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import (
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"container/list"
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"time"
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)
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type LRU[T any] struct {
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queue *list.List
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items map[string]*list.Element
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capacity int
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}
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type item[T any] struct {
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key string
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value *T
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eol time.Time
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}
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func New[T any](capacity int) *LRU[T] {
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return &LRU[T]{
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queue: list.New(),
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items: make(map[string]*list.Element, capacity),
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capacity: capacity,
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}
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}
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func (lru *LRU[T]) Set(key string, value T, ttl time.Duration) (evicted bool) {
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eol := time.Now().Add(ttl)
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if element, ok := lru.items[key]; ok {
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lru.queue.MoveToFront(element)
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item := element.Value.(*item[T])
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item.value = &value
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item.eol = eol
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return
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}
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if lru.queue.Len() == lru.capacity {
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lru.evict()
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evicted = true
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}
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item := &item[T]{
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key: key,
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value: &value,
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eol: eol,
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}
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element := lru.queue.PushFront(item)
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lru.items[item.key] = element
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return
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}
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func (lru *LRU[T]) Get(name string) (value T, ok bool) {
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element, ok := lru.items[name]
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if !ok {
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return value, false
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}
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item := element.Value.(*item[T])
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if item.expired() {
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lru.delete(element)
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return value, false
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}
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lru.queue.MoveToFront(element)
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return *item.value, true
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}
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func (lru *LRU[T]) evict() {
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element := lru.queue.Back()
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if element == nil {
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return
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}
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for { // find first expired
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item := element.Value.(*item[T])
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if item.expired() {
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lru.delete(element)
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return
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}
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element = element.Prev()
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if element == nil {
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break // probably expired not found
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}
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}
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lru.delete(lru.queue.Back()) // delete oldest if no one expired
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}
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func (lru *LRU[T]) delete(element *list.Element) {
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lru.queue.Remove(element)
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delete(lru.items, element.Value.(*item[T]).key)
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}
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func (i *item[T]) expired() bool {
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return time.Now().After(i.eol)
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}
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