Hide list root (#2)

internal/list/entry.go

@@ -19,8 +19,18 @@ type Entry[K comparable, V any] struct {
 }
 
 // PrevEntry returns the previous list element or nil.
+// note: can't get root entry
 func (e *Entry[K, V]) PrevEntry() *Entry[K, V] {
-	if p := e.prev; e.list != nil && p != e.list.Root() {
+	if p := e.prev; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+// NextEntry returns the next list element or nil.
+// note: can't get root entry
+func (e *Entry[K, V]) NextEntry() *Entry[K, V] {
+	if p := e.next; e.list != nil && p != &e.list.root {
 		return p
 	}
 	return nil

internal/list/list.go

@@ -121,20 +121,15 @@ func (l *DoublyLinkedList[K, V]) Back() *Entry[K, V] {
 	return l.root.prev
 }
 
-// Root returns the root of the list.
-func (l *DoublyLinkedList[K, V]) Root() *Entry[K, V] {
-	return &l.root
-}
-
 // Root returns the root of the list.
 func (l *DoublyLinkedList[K, V]) Debug() []string {
 	asc := []string{"root"}
-	for ent := l.Root().next; ent.list == l; ent = ent.next {
+	for ent := l.root.next; ent.list == l; ent = ent.next {
 		asc = append(asc, fmt.Sprintf("%v", ent.Key))
 	}
 	asc = append(asc, "root")
 	desc := []string{"root"}
-	for ent := l.Root().prev; ent.list == l; ent = ent.prev {
+	for ent := l.root.prev; ent.list == l; ent = ent.prev {
 		desc = append(desc, fmt.Sprintf("%v", ent.Key))
 	}
 	desc = append(desc, "root")

internal/list/list_test.go

@@ -37,7 +37,7 @@ func TestLruList_PushFront(t *testing.T) {
 	assert.EqualValues(t, 1, l.Len())
 
 	second := l.PushFront(2, 22)
-	assert.EqualValues(t, second.prev, l.Root()) // forbid root
+	assert.EqualValues(t, second.prev, &l.root) // forbid root
 	assert.Equal(t, first.PrevEntry(), second)
 
 	assert.EqualValues(t, 2, second.Key)
@@ -118,7 +118,7 @@ func TestLruList_PushBack(t *testing.T) {
 	assert.EqualValues(t, 1, l.Len())
 
 	second := l.PushBack(2, 22)
-	assert.Equal(t, second.next, l.Root())
+	assert.Equal(t, second.next, &l.root)
 	assert.Equal(t, first.next, second)
 
 	assert.EqualValues(t, 2, second.Key)
@@ -155,5 +155,7 @@ func TestLruList_Entry(t *testing.T) {
 	first := l.PushFront(1, 1)
 	second := l.PushFront(2, 2)
 	assert.Equal(t, first.PrevEntry(), second)
+	assert.Equal(t, second.NextEntry(), first)
 	assert.Nil(t, second.PrevEntry())
+	assert.Nil(t, first.NextEntry())
 }

simplelfu/lfu.go

@@ -190,12 +190,13 @@ func (c *Cache[K, V]) removeElement(ent *list.Entry[K, *LFUValue[V]]) {
 
 // moveForward is used to move a given list element to the front of the cache
 func (c *Cache[K, V]) moveForward(ent *list.Entry[K, *LFUValue[V]]) {
+	// if ent is root entry, ent.PrevEntry() is nil
 	for prev := ent.PrevEntry(); prev != nil; prev = ent.PrevEntry() {
 		if ent.Value.GetVisit() < prev.Value.GetVisit() {
 			break
 		}
-		if !c.evictList.MoveToAt(ent, prev.PrevEntry()) {
-			break
-		}
+		// because ent can't get root entry from PrevEntry(),
+		// so we don't need to check
+		_ = c.evictList.MoveToAt(ent, prev.PrevEntry())
 	}
 }