feature: add Cap interface{} (#145)

* feature: add Cap interface{}
* feature: add Cap for 2q and fix bug on arc.Cap
* feature: add Cap for expireable_lru
* test: add Cap for expire lru

Author: zhuliquan

2q.go

@@ -175,6 +175,11 @@ 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
+}
+
 // Resize changes the cache size.
 func (c *TwoQueueCache[K, V]) Resize(size int) (evicted int) {
 	c.lock.Lock()

2q_test.go

@@ -299,6 +299,9 @@ 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

@@ -202,6 +202,11 @@ func (c *ARCCache[K, V]) Len() int {
 	return c.t1.Len() + c.t2.Len()
 }
 
+// Cap returns the capacity of the cache
+func (c *ARCCache[K, V]) Cap() int {
+	return c.size
+}
+
 // Keys returns all the cached keys
 func (c *ARCCache[K, V]) Keys() []K {
 	c.lock.RLock()

arc/arc_test.go

@@ -313,6 +313,9 @@ func TestARC(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 {
@@ -340,6 +343,9 @@ func TestARC(t *testing.T) {
 			t.Fatalf("should be deleted")
 		}
 	}
+	if l.Cap() != 128 {
+		t.Fatalf("expect %d, but %d", 128, l.Cap())
+	}
 
 	l.Purge()
 	if l.Len() != 0 {
@@ -348,6 +354,9 @@ func TestARC(t *testing.T) {
 	if _, ok := l.Get(200); ok {
 		t.Fatalf("should contain nothing")
 	}
+	if l.Cap() != 128 {
+		t.Fatalf("expect %d, but %d", 128, l.Cap())
+	}
 }
 
 // Test that Contains doesn't update recent-ness

expirable/expirable_lru.go

@@ -339,3 +339,8 @@ func (c *LRU[K, V]) addToBucket(e *internal.Entry[K, V]) {
 func (c *LRU[K, V]) removeFromBucket(e *internal.Entry[K, V]) {
 	delete(c.buckets[e.ExpireBucket].entries, e.Key)
 }
+
+// Cap returns the capacity of the cache
+func (c *LRU[K, V]) Cap() int {
+	return c.size
+}

expirable/expirable_lru_test.go

@@ -425,6 +425,10 @@ func TestLoadingExpired(t *testing.T) {
 func TestLRURemoveOldest(t *testing.T) {
 	lc := NewLRU[string, string](2, nil, 0)
 
+	if lc.Cap() != 2 {
+		t.Fatalf("expect cap is 2")
+	}
+
 	k, v, ok := lc.RemoveOldest()
 	if k != "" {
 		t.Fatalf("should be empty")

lru.go

@@ -248,3 +248,8 @@ func (c *Cache[K, V]) Len() int {
 	c.lock.RUnlock()
 	return length
 }
+
+// Cap returns the capacity of the cache
+func (c *Cache[K, V]) Cap() int {
+	return c.lru.Cap()
+}

lru_test.go

@@ -86,6 +86,9 @@ func TestLRU(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())
+	}
 
 	if evictCounter != 128 {
 		t.Fatalf("bad evict count: %v", evictCounter)

simplelru/lru.go

@@ -147,6 +147,11 @@ func (c *LRU[K, V]) Len() int {
 	return c.evictList.Length()
 }
 
+// Cap returns the capacity of the cache
+func (c *LRU[K, V]) Cap() int {
+	return c.size
+}
+
 // Resize changes the cache size.
 func (c *LRU[K, V]) Resize(size int) (evicted int) {
 	diff := c.Len() - size

simplelru/lru_interface.go

@@ -38,6 +38,9 @@ type LRUCache[K comparable, V any] interface {
 	// Returns the number of items in the cache.
 	Len() int
 
+	// Returns the capacity of the cache.
+	Cap() int
+
 	// Clears all cache entries.
 	Purge()
 

simplelru/lru_test.go

@@ -27,6 +27,9 @@ func TestLRU(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())
+	}
 
 	if evictCounter != 128 {
 		t.Fatalf("bad evict count: %v", evictCounter)