go/store/skip: optimized skip list Iter

go/store/skip/list.go

@@ -113,10 +113,9 @@ func (l *List) Revert() {
 func (l *List) Truncate() {
 	l.nodes = l.nodes[:1]
 	// point sentinel.prev at itself
-	s := l.getNode(sentinelId)
+	s := l.nodePtr(sentinelId)
 	s.next = tower{}
 	s.prev = sentinelId
-	l.updateNode(s)
 	l.checkpoint = nodeId(1)
 	l.count = 0
 }
@@ -139,7 +138,7 @@ func (l *List) Get(key []byte) (val []byte, ok bool) {
 	var id nodeId
 	next, prev := l.headPointer(), sentinelId
 	for lvl := maxHeight; lvl >= 0; {
-		nd := l.getNodeRef(next[lvl])
+		nd := l.nodePtr(next[lvl])
 		// descend if we can't advance at |lvl|
 		if l.compareKeys(key, nd.key) < 0 {
 			id = prev
@@ -150,7 +149,7 @@ func (l *List) Get(key []byte) (val []byte, ok bool) {
 		next = nd.next
 		prev = nd.id
 	}
-	node := l.getNodeRef(id)
+	node := l.nodePtr(id)
 	if l.compareKeys(key, node.key) == 0 {
 		val, ok = node.val, true
 	}
@@ -170,7 +169,7 @@ func (l *List) Put(key, val []byte) {
 	var path tower
 	next, prev := l.headPointer(), sentinelId
 	for h := maxHeight; h >= 0; {
-		curr := l.getNodeRef(next[h])
+		curr := l.nodePtr(next[h])
 		// descend if we can't advance at |lvl|
 		if l.compareKeys(key, curr.key) <= 0 {
 			path[h] = prev
@@ -183,8 +182,8 @@ func (l *List) Put(key, val []byte) {
 	}
 
 	// check if |key| exists in |l|
-	node := l.getNodeRef(path[0])
-	node = l.getNodeRef(node.next[0])
+	node := l.nodePtr(path[0])
+	node = l.nodePtr(node.next[0])
 
 	if l.compareKeys(key, node.key) == 0 {
 		l.overwrite(key, val, path, node)
@@ -214,15 +213,15 @@ func (l *List) insert(key, value []byte, path tower) {
 		id:     id,
 		height: l.rollHeight(key),
 	})
-	novel := l.getNodeRef(id)
+	novel := l.nodePtr(id)
 	for h := uint8(0); h <= novel.height; h++ {
 		// set forward pointers
-		n := l.getNodeRef(path[h])
+		n := l.nodePtr(path[h])
 		novel.next[h] = n.next[h]
 		n.next[h] = novel.id
 	}
 	// set back pointers
-	n := l.getNodeRef(novel.next[0])
+	n := l.nodePtr(novel.next[0])
 	novel.prev = n.prev
 	n.prev = novel.id
 }
@@ -239,16 +238,16 @@ func (l *List) overwrite(key, value []byte, path tower, old *skipNode) {
 	})
 	for h := uint8(0); h <= old.height; h++ {
 		// set forward pointers
-		n := l.getNodeRef(path[h])
+		n := l.nodePtr(path[h])
 		n.next[h] = id
 	}
 	// set back pointer
-	n := l.getNodeRef(old.next[0])
+	n := l.nodePtr(old.next[0])
 	n.prev = id
 }
 
 type ListIter struct {
-	curr skipNode
+	curr *skipNode
 	list *List
 }
 
@@ -259,13 +258,13 @@ func (it *ListIter) Current() (key, val []byte) {
 
 // Advance advances the iterator.
 func (it *ListIter) Advance() {
-	it.curr = it.list.getNode(it.curr.next[0])
+	it.curr = it.list.nodePtr(it.curr.next[0])
 	return
 }
 
 // Retreat retreats the iterator.
 func (it *ListIter) Retreat() {
-	it.curr = it.list.getNode(it.curr.prev)
+	it.curr = it.list.nodePtr(it.curr.prev)
 	return
 }
 
@@ -308,19 +307,19 @@ func (l *List) IterAtEnd() *ListIter {
 }
 
 // seek returns the skipNode with the smallest key >= |key|.
-func (l *List) seek(key []byte) skipNode {
+func (l *List) seek(key []byte) *skipNode {
 	return l.seekWithFn(func(curr []byte) (advance bool) {
 		return l.compareKeys(key, curr) > 0
 	})
 }
 
-func (l *List) seekWithFn(cb SeekFn) (node skipNode) {
+func (l *List) seekWithFn(cb SeekFn) (node *skipNode) {
 	ptr := l.headPointer()
 	for h := int64(maxHeight); h >= 0; h-- {
-		node = l.getNode(ptr[h])
+		node = l.nodePtr(ptr[h])
 		for cb(node.key) {
 			ptr = node.next
-			node = l.getNode(ptr[h])
+			node = l.nodePtr(ptr[h])
 		}
 	}
 	return
@@ -330,27 +329,19 @@ func (l *List) headPointer() tower {
 	return l.nodes[0].next
 }
 
-func (l *List) firstNode() skipNode {
-	return l.getNode(l.nodes[0].next[0])
+func (l *List) firstNode() *skipNode {
+	return l.nodePtr(l.nodes[0].next[0])
 }
 
-func (l *List) lastNode() skipNode {
-	s := l.getNode(sentinelId)
-	return l.getNode(s.prev)
+func (l *List) lastNode() *skipNode {
+	s := l.nodePtr(sentinelId)
+	return l.nodePtr(s.prev)
 }
 
-func (l *List) getNode(id nodeId) skipNode {
-	return l.nodes[id]
-}
-
-func (l *List) getNodeRef(id nodeId) *skipNode {
+func (l *List) nodePtr(id nodeId) *skipNode {
 	return &l.nodes[id]
 }
 
-func (l *List) updateNode(node skipNode) {
-	l.nodes[node.id] = node
-}
-
 func (l *List) nextNodeId() nodeId {
 	return nodeId(len(l.nodes))
 }