Add Len() to common interface

- implement Len for simple cache

Author: Eero Norri

cache.go

@@ -23,6 +23,8 @@ type Interface[K comparable, V any] interface {
 	Keys() []K
 	// Delete deletes the item with provided key from the cache.
 	Delete(key K)
+	// Len returns the number of items in the cache.
+	Len() int
 }
 
 var (
@@ -253,6 +255,13 @@ func (c *Cache[K, V]) Delete(key K) {
 	c.cache.Delete(key)
 }
 
+// Len returns the number of items in the cache.
+func (c *Cache[K, V]) Len() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.cache.Len()
+}
+
 // Contains reports whether key is within cache.
 func (c *Cache[K, V]) Contains(key K) bool {
 	c.mu.Lock()

example_test.go

@@ -123,6 +123,16 @@ func ExampleCache_Keys() {
 	// [a b c]
 }
 
+func ExampleCache_Len() {
+	c := cache.New(cache.AsLFU[string, int]())
+	c.Set("a", 1)
+	c.Set("b", 1)
+	c.Set("c", 1)
+	fmt.Println(c.Len())
+	// Output:
+	// 3
+}
+
 func ExampleCache_Contains() {
 	c := cache.New(cache.AsLRU[string, int]())
 	c.Set("a", 1)

policy/simple/simple.go

@@ -59,3 +59,8 @@ func (c *Cache[K, _]) Keys() []K {
 func (c *Cache[K, V]) Delete(key K) {
 	delete(c.items, key)
 }
+
+// Len returns the number of items in the cache.
+func (c *Cache[K, V]) Len() int {
+	return len(c.items)
+}