[#31] Add boolean value return in Set

Add return a boolean value when setting a key-value item with too high a cost.

cache.go

@@ -139,25 +139,26 @@ func (c *Cache[K, V]) afterGet(got *node.Node[K, V]) {
 	}
 }
 
-// Set associates the value with the key in this cache. If the cache previously
-// contained a value associated with the key, the old value is replaced by the new value.
-func (c *Cache[K, V]) Set(key K, value V) {
-	c.set(key, value, 0)
+// Set associates the value with the key in this cache.
+//
+// If it returns false, then the key-value item had too much cost and the Set was dropped.
+func (c *Cache[K, V]) Set(key K, value V) bool {
+	return c.set(key, value, 0)
 }
 
-// SetWithTTL associates the value with the key in this cache and sets the custom ttl for this key-value pair.
+// SetWithTTL associates the value with the key in this cache and sets the custom ttl for this key-value item.
 //
-// If the cache previously contained a value associated with the key, the old value is replaced by the new value.
-func (c *Cache[K, V]) SetWithTTL(key K, value V, ttl time.Duration) {
+// If it returns false, then the key-value item had too much cost and the SetWithTTL was dropped.
+func (c *Cache[K, V]) SetWithTTL(key K, value V, ttl time.Duration) bool {
 	ttl = (ttl + time.Second - 1) / time.Second
 	expiration := unixtime.Now() + uint32(ttl)
-	c.set(key, value, expiration)
+	return c.set(key, value, expiration)
 }
 
-func (c *Cache[K, V]) set(key K, value V, expiration uint32) {
+func (c *Cache[K, V]) set(key K, value V, expiration uint32) bool {
 	cost := c.costFunc(key, value)
 	if cost > c.policy.MaxAvailableCost() {
-		return
+		return false
 	}
 
 	n := node.New(key, value, expiration, cost)
@@ -169,6 +170,8 @@ func (c *Cache[K, V]) set(key K, value V, expiration uint32) {
 		// insert
 		c.writeBuffer.Insert(node.NewAddTask(n))
 	}
+
+	return true
 }
 
 // Delete removes the association for this key from the cache.

cache_test.go

@@ -122,6 +122,34 @@ func TestCache_SetWithTTL(t *testing.T) {
 	}
 }
 
+func TestCache_SetWithCost(t *testing.T) {
+	size := 10
+	c, err := MustBuilder[int, int](size).Cost(func(key int, value int) uint32 {
+		return uint32(key)
+	}).Build()
+	if err != nil {
+		t.Fatalf("can not create cache: %v", err)
+	}
+
+	goodCost := int(c.policy.MaxAvailableCost())
+	badCost := goodCost + 1
+
+	added := c.Set(goodCost, 1)
+	if !added {
+		t.Fatalf("Set was dropped, even though it shouldn't have been. Max available cost: %d, actual cost: %d",
+			c.policy.MaxAvailableCost(),
+			c.costFunc(goodCost, 1),
+		)
+	}
+	added = c.Set(badCost, 1)
+	if added {
+		t.Fatalf("Set wasn't dropped, though it should have been. Max available cost: %d, actual cost: %d",
+			c.policy.MaxAvailableCost(),
+			c.costFunc(badCost, 1),
+		)
+	}
+}
+
 func TestCache_Ratio(t *testing.T) {
 	b, err := NewBuilder[uint64, uint64](100)
 	if err != nil {