embed map directly, create new ptr element constraint

backend.go

@@ -7,21 +7,14 @@ import (
 	"github.com/mgnsk/evcache/v3/ringlist"
 )
 
-type storageMap[K comparable, V any] interface {
-	Load(key K) (value V, ok bool)
-	LoadOrStore(key K, value V) (actual V, loaded bool)
-	Delete(key K)
-	Range(f func(key K, value V) bool)
-}
-
 type recordList[V any] struct {
 	ringlist.List[record[V], *record[V]]
 }
 
 type backend[K comparable, V any] struct {
 	timer            *time.Timer
 	done             chan struct{}
-	xmap             storageMap[K, *record[V]]
+	xmap             syncMapWrapper[K, *record[V]]
 	list             recordList[V]
 	earliestExpireAt int64
 	cap              int
@@ -36,7 +29,6 @@ func newBackend[K comparable, V any](capacity int) *backend[K, V] {
 	return &backend[K, V]{
 		timer: t,
 		done:  make(chan struct{}),
-		xmap:  newSyncMapWrapper[K, *record[V]](capacity),
 		cap:   capacity,
 	}
 }

map.go

@@ -1,17 +1,14 @@
 package evcache
 
-import "sync"
+import (
+	"sync"
+)
 
+// syncMapWrapper wraps sync.Map. The zero syncMapWrapper is empty and ready to use.
 type syncMapWrapper[K comparable, V any] struct {
 	sync.Map
 }
 
-var _ storageMap[string, string] = &syncMapWrapper[string, string]{}
-
-func newSyncMapWrapper[K comparable, V any](capacity int) storageMap[K, V] {
-	return &syncMapWrapper[K, V]{}
-}
-
 func (w *syncMapWrapper[K, V]) Load(key K) (value V, ok bool) {
 	if v, ok := w.Map.Load(key); ok {
 		return v.(V), true

ringlist/ringlist.go

@@ -14,12 +14,15 @@ type ListElement[E any] interface {
 	Prev() E
 }
 
-// List is a generic circular doubly linked list.
-// The zero value is a ready to use empty list.
-type List[T any, E interface {
+// PtrListElement is a pointer list element constraint.
+type PtrListElement[T any, E any] interface {
 	*T
 	ListElement[E]
-}] struct {
+}
+
+// List is a generic circular doubly linked list.
+// The zero value is a ready to use empty list.
+type List[T any, E PtrListElement[T, E]] struct {
 	tail E
 	len  int
 }