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loadingcache.go
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loadingcache.go
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package main
import (
"sync"
"time"
)
const (
WriteThrough = 1 << iota
Loading
WriteBack
)
type LoadingFunction[K comparable, V any] func(key K) (V, error)
type WeighingFunction[K comparable, V any] func(key K, value V) int64
type WriteThroughFunction[K comparable, V any] func(key K, value V) error
type cacheEntry[T any] struct {
value T
expiration int64
}
type LoadingCache[K comparable, V any] struct {
maximumSize int64
maximumWeight int64
expirationSeconds int64
loadingFunction LoadingFunction[K, V]
writeThroughFunction WriteThroughFunction[K, V]
weighingFunction WeighingFunction[K, V]
cache map[K]*cacheEntry[V]
currentWeight int64
mu sync.RWMutex
}
func (c *LoadingCache[K, V]) addEntry(key K, value V) {
if c.weighingFunction != nil {
c.currentWeight += c.weighingFunction(key, value)
}
c.evictIfNecessary()
c.cache[key] = &cacheEntry[V]{
value: value,
expiration: time.Now().Unix() + c.expirationSeconds,
}
}
func (c *LoadingCache[K, V]) shouldEvict() bool {
if c.maximumSize > 0 && int64(len(c.cache)) >= c.maximumSize {
return true
}
if c.weighingFunction == nil || c.maximumWeight <= 0 {
return false
}
return c.currentWeight > c.maximumWeight
}
func (c *LoadingCache[K, V]) evictIfNecessary() {
c.mu.Lock()
defer c.mu.Unlock()
for c.shouldEvict() {
// implement LRU eviction policy
}
}
func (c *LoadingCache[K, V]) isExpired(entry *cacheEntry[V]) bool {
return time.Now().Unix() > entry.expiration
}
func (c *LoadingCache[K, V]) Get(key K) (V, error) {
c.mu.RLock()
entry, exists := c.cache[key]
if exists && !c.isExpired(entry) {
c.mu.RUnlock()
return entry.value, nil
}
c.mu.RUnlock()
c.mu.Lock()
defer c.mu.Unlock()
entry, exists = c.cache[key]
if exists && !c.isExpired(entry) {
return entry.value, nil
}
value, err := c.loadingFunction(key)
if err != nil {
var zeroValue V
return zeroValue, err
}
c.addEntry(key, value)
return value, nil
}
func (c *LoadingCache[K, V]) Invalidate(key K) {
c.mu.Lock()
defer c.mu.Unlock()
if entry, exists := c.cache[key]; exists {
if c.weighingFunction != nil {
c.currentWeight -= c.weighingFunction(key, entry.value)
}
delete(c.cache, key)
}
}
func (c *LoadingCache[K, V]) Refresh(key K) (V, error) {
if _, exists := c.cache[key]; exists {
c.mu.Lock()
defer c.mu.Unlock()
value, err := c.loadingFunction(key)
if err != nil {
var zeroValue V
return zeroValue, err
}
c.cache[key].expiration = time.Now().Unix() + c.expirationSeconds
c.cache[key].value = value
return value, nil
}
return c.Get(key)
}
func (c *LoadingCache[K, V]) IsLoaded(key K) bool {
if _, exists := c.cache[key]; exists {
return true
}
return false
}