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loading_cache.go
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loading_cache.go
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package cache
import (
"time"
csmap "github.com/mhmtszr/concurrent-swiss-map"
)
// Function that gets executed by the 'Load' and 'Reload' function
type LoaderFunc[K comparable, V any] func(key K) (V, error)
type LoadingCache[K comparable, V any] interface {
// Loads an item into cache using the provided LoaderFunc and returns the value.
//
// If the item is already cached, it'll return that value instead.
//
// Whenever the LoaderFunc returns an error, the value does NOT get saved.
//
// This function is thread-safe and the LoaderFunc is called only once in a concurrent environment.
Load(key K) (V, error)
// Reloads an item into cache using the provided LoaderFunc and returns the new value.
//
// Whenever the LoaderFunc returns an error, the value does NOT get saved (old value remains in cache)
Reload(key K) (V, error)
// Embed Cache
Cache[K, V]
}
func NewLoadingCache[K comparable, V any](
loaderFunc LoaderFunc[K, V],
options ...Option[K, V],
) LoadingCache[K, V] {
data := csmap.Create[K, *entry[K, V]]()
cleaner := newCacheCleaner(data, time.Second*5)
opts := append(options, withLoaderFunc(loaderFunc))
return newCache(data, cleaner, opts...)
}
func (c *cache[K, V]) Load(key K) (V, error) {
unlock := c.mu.lock(key)
defer unlock()
cached, found := c.get(key)
if found {
return cached, nil
}
value, err := c.loaderFunc(key)
if err == nil {
c.data.Store(key, c.newEntry(key, value))
}
return value, err
}
func (c *cache[K, V]) Reload(key K) (V, error) {
unlock := c.mu.lock(key)
defer unlock()
value, err := c.loaderFunc(key)
if err == nil {
c.data.Store(key, c.newEntry(key, value))
}
return value, err
}
// Function that can be used inside a testing environment
func NoopLoaderFunc[K comparable, V any](key K) (V, error) {
var empty V
return empty, nil
}
func withLoaderFunc[K comparable, V any](
loaderFunc LoaderFunc[K, V],
) Option[K, V] {
return func(c *cache[K, V]) {
c.loaderFunc = loaderFunc
}
}