feature: add cap for 2q and fix bug on arc.Cap

2q.go

@@ -171,6 +171,11 @@ func (c *TwoQueueCache[K, V]) Len() int {
 	return c.recent.Len() + c.frequent.Len()
 }
 
+// Cap returns the capacity of the cache
+func (c *TwoQueueCache[K, V]) Cap() int {
+	return c.size
+}
+
 // Keys returns a slice of the keys in the cache.
 // The frequently used keys are first in the returned slice.
 func (c *TwoQueueCache[K, V]) Keys() []K {

2q_test.go

@@ -230,6 +230,9 @@ func Test2Q(t *testing.T) {
 	if l.Len() != 128 {
 		t.Fatalf("bad len: %v", l.Len())
 	}
+	if l.Cap() != 128 {
+		t.Fatalf("expect %d, but %d", 128, l.Cap())
+	}
 
 	for i, k := range l.Keys() {
 		if v, ok := l.Get(k); !ok || v != k || v != i+128 {

arc/arc.go

@@ -204,7 +204,7 @@ func (c *ARCCache[K, V]) Len() int {
 
 // Cap returns the capacity of cache
 func (c *ARCCache[K, V]) Cap() int {
-	return c.Cap()
+	return c.size
 }
 
 // Keys returns all the cached keys