fix invalid cache length when set with zero value key (#24)

* fix invalid cache length when set with zero value key

* Update ttl_shard.go

Co-authored-by: ccoVeille <3875889+ccoVeille@users.noreply.github.com>

---------

Co-authored-by: ccoVeille <3875889+ccoVeille@users.noreply.github.com>

lru_shard.go

@@ -131,7 +131,9 @@ func (s *lrushard[K, V]) Set(hash uint32, key K, value V) (prev V, replaced bool
 	index := s.list[0].prev
 	node := (*lrunode[K, V])(unsafe.Add(unsafe.Pointer(&s.list[0]), uintptr(index)*unsafe.Sizeof(s.list[0])))
 	evictedValue := node.value
-	if key != node.key {
+
+	// delete the old key if the list is full, note that the list length is size+1
+	if uint32(len(s.list)-1) < s.tableLength+1 && key != node.key {
 		s.tableDelete(uint32(s.tableHasher(noescape(unsafe.Pointer(&node.key)), s.tableSeed)), node.key)
 	}
 

lru_shard_test.go

@@ -1,7 +1,9 @@
 package lru
 
 import (
+	"fmt"
 	"testing"
+	"time"
 	"unsafe"
 )
 
@@ -41,3 +43,40 @@ func TestLRUShardTableSet(t *testing.T) {
 		t.Errorf("foobar should be set to 42: %v %v", i, ok)
 	}
 }
+
+func TestLRUCacheLengthWithZeroValue(t *testing.T) {
+	cache := NewTTLCache[string, string](128, WithShards[string, string](1))
+
+	cache.Set("", "", time.Hour)
+	cache.Set("1", "1", time.Hour)
+
+	if got, want := cache.Len(), 2; got != want {
+		t.Fatalf("curent cache length %v should be %v", got, want)
+	}
+
+	for i := 2; i < 128; i++ {
+		k := fmt.Sprintf("%d", i)
+		if _, replace := cache.Set(k, k, time.Hour); replace {
+			t.Fatalf("key %v should not be replaced", k)
+		}
+	}
+
+	if l := cache.Len(); l != 128 {
+		t.Fatalf("cache length %v should be 128", l)
+	}
+
+	for i := 128; i < 256; i++ {
+		k := fmt.Sprintf("%d", i)
+		v := ""
+		if i-128 > 0 {
+			v = fmt.Sprintf("%d", i-128)
+		}
+		if prev, _ := cache.Set(k, k, time.Hour); prev != v {
+			t.Fatalf("value %v should be evicted", prev)
+		}
+	}
+
+	if l := cache.Len(); l != 128 {
+		t.Fatalf("cache length %v should be 128", l)
+	}
+}

ttl_cache_test.go

@@ -73,6 +73,37 @@ func TestTTLCacheGetSet(t *testing.T) {
 	}
 }
 
+func TestTTLCacheLengthWithZeroValue(t *testing.T) {
+	cache := NewTTLCache[int, int](128, WithShards[int, int](1))
+
+	cache.Set(0, 0, time.Hour)
+	cache.Set(1, 1, time.Hour)
+
+	if got, want := cache.Len(), 2; got != want {
+		t.Fatalf("curent cache length %v should be %v", got, want)
+	}
+
+	for i := 2; i < 128; i++ {
+		if _, replace := cache.Set(i, i, time.Hour); replace {
+			t.Fatalf("no value should be replaced")
+		}
+	}
+
+	if l := cache.Len(); l != 128 {
+		t.Fatalf("cache length %v should be 128", l)
+	}
+
+	for i := 128; i < 256; i++ {
+		if prev, _ := cache.Set(i, i, time.Hour); prev != i-128 {
+			t.Fatalf("value %v should be evicted", prev)
+		}
+	}
+
+	if l := cache.Len(); l != 128 {
+		t.Fatalf("cache length %v should be 128", l)
+	}
+}
+
 func TestTTLCacheSetIfAbsent(t *testing.T) {
 	cache := NewTTLCache[int, int](128)
 

ttl_shard.go

@@ -183,7 +183,9 @@ func (s *ttlshard[K, V]) Set(hash uint32, key K, value V, ttl time.Duration) (pr
 	index := s.list[0].prev
 	node := (*ttlnode[K, V])(unsafe.Add(unsafe.Pointer(&s.list[0]), uintptr(index)*unsafe.Sizeof(s.list[0])))
 	evictedValue := node.value
-	if key != node.key {
+
+	// delete the old key if the list is full, note that the list length is size+1
+	if len(s.list)-1 < int(s.tableLength+1) && key != node.key {
 		s.tableDelete(uint32(s.tableHasher(noescape(unsafe.Pointer(&node.key)), s.tableSeed)), node.key)
 	}