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https://github.com/HDT3213/godis.git
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refactor project structure
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hdt3213
344
datastruct/sortedset/skiplist.go
Normal file
344
datastruct/sortedset/skiplist.go
Normal file
@@ -0,0 +1,344 @@
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package sortedset
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import "math/rand"
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const (
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maxLevel = 16
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)
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type Element struct {
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Member string
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Score float64
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}
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// level aspect of a Node
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type Level struct {
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forward *Node // forward node has greater score
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span int64
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}
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type Node struct {
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Element
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backward *Node
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level []*Level // level[0] is base level
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}
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type skiplist struct {
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header *Node
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tail *Node
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length int64
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level int16
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}
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func makeNode(level int16, score float64, member string) *Node {
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n := &Node{
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Element: Element{
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Score: score,
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Member: member,
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},
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level: make([]*Level, level),
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}
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for i := range n.level {
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n.level[i] = new(Level)
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}
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return n
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}
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func makeSkiplist() *skiplist {
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return &skiplist{
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level: 1,
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header: makeNode(maxLevel, 0, ""),
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}
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}
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func randomLevel() int16 {
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level := int16(1)
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for float32(rand.Int31()&0xFFFF) < (0.25 * 0xFFFF) {
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level++
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}
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if level < maxLevel {
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return level
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}
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return maxLevel
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}
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func (skiplist *skiplist) insert(member string, score float64) *Node {
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update := make([]*Node, maxLevel) // link new node with node in `update`
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rank := make([]int64, maxLevel)
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// find position to insert
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node := skiplist.header
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for i := skiplist.level - 1; i >= 0; i-- {
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if i == skiplist.level-1 {
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rank[i] = 0
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} else {
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rank[i] = rank[i+1] // store rank that is crossed to reach the insert position
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}
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if node.level[i] != nil {
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// traverse the skip list
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for node.level[i].forward != nil &&
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(node.level[i].forward.Score < score ||
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(node.level[i].forward.Score == score && node.level[i].forward.Member < member)) { // same score, different key
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rank[i] += node.level[i].span
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node = node.level[i].forward
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}
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}
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update[i] = node
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}
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level := randomLevel()
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// extend skiplist level
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if level > skiplist.level {
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for i := skiplist.level; i < level; i++ {
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rank[i] = 0
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update[i] = skiplist.header
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update[i].level[i].span = skiplist.length
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}
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skiplist.level = level
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}
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// make node and link into skiplist
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node = makeNode(level, score, member)
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for i := int16(0); i < level; i++ {
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node.level[i].forward = update[i].level[i].forward
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update[i].level[i].forward = node
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// update span covered by update[i] as node is inserted here
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node.level[i].span = update[i].level[i].span - (rank[0] - rank[i])
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update[i].level[i].span = (rank[0] - rank[i]) + 1
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}
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// increment span for untouched levels
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for i := level; i < skiplist.level; i++ {
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update[i].level[i].span++
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}
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// set backward node
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if update[0] == skiplist.header {
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node.backward = nil
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} else {
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node.backward = update[0]
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}
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if node.level[0].forward != nil {
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node.level[0].forward.backward = node
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} else {
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skiplist.tail = node
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}
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skiplist.length++
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return node
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}
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/*
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* param node: node to delete
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* param update: backward node (of target)
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*/
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func (skiplist *skiplist) removeNode(node *Node, update []*Node) {
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for i := int16(0); i < skiplist.level; i++ {
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if update[i].level[i].forward == node {
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update[i].level[i].span += node.level[i].span - 1
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update[i].level[i].forward = node.level[i].forward
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} else {
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update[i].level[i].span--
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}
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}
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if node.level[0].forward != nil {
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node.level[0].forward.backward = node.backward
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} else {
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skiplist.tail = node.backward
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}
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for skiplist.level > 1 && skiplist.header.level[skiplist.level-1].forward == nil {
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skiplist.level--
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}
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skiplist.length--
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}
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/*
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* return: has found and removed node
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*/
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func (skiplist *skiplist) remove(member string, score float64) bool {
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/*
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* find backward node (of target) or last node of each level
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* their forward need to be updated
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*/
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update := make([]*Node, maxLevel)
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node := skiplist.header
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for i := skiplist.level - 1; i >= 0; i-- {
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for node.level[i].forward != nil &&
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(node.level[i].forward.Score < score ||
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(node.level[i].forward.Score == score &&
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node.level[i].forward.Member < member)) {
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node = node.level[i].forward
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}
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update[i] = node
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}
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node = node.level[0].forward
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if node != nil && score == node.Score && node.Member == member {
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skiplist.removeNode(node, update)
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// free x
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return true
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}
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return false
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}
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/*
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* return: 1 based rank, 0 means member not found
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*/
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func (skiplist *skiplist) getRank(member string, score float64) int64 {
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var rank int64 = 0
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x := skiplist.header
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for i := skiplist.level - 1; i >= 0; i-- {
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for x.level[i].forward != nil &&
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(x.level[i].forward.Score < score ||
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(x.level[i].forward.Score == score &&
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x.level[i].forward.Member <= member)) {
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rank += x.level[i].span
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x = x.level[i].forward
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}
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/* x might be equal to zsl->header, so test if obj is non-NULL */
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if x.Member == member {
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return rank
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}
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}
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return 0
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}
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/*
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* 1-based rank
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*/
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func (skiplist *skiplist) getByRank(rank int64) *Node {
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var i int64 = 0
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n := skiplist.header
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// scan from top level
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for level := skiplist.level - 1; level >= 0; level-- {
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for n.level[level].forward != nil && (i+n.level[level].span) <= rank {
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i += n.level[level].span
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n = n.level[level].forward
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}
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if i == rank {
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return n
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}
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}
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return nil
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}
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func (skiplist *skiplist) hasInRange(min *ScoreBorder, max *ScoreBorder) bool {
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// min & max = empty
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if min.Value > max.Value || (min.Value == max.Value && (min.Exclude || max.Exclude)) {
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return false
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}
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// min > tail
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n := skiplist.tail
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if n == nil || !min.less(n.Score) {
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return false
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}
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// max < head
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n = skiplist.header.level[0].forward
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if n == nil || !max.greater(n.Score) {
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return false
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}
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return true
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}
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func (skiplist *skiplist) getFirstInScoreRange(min *ScoreBorder, max *ScoreBorder) *Node {
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if !skiplist.hasInRange(min, max) {
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return nil
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}
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n := skiplist.header
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// scan from top level
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for level := skiplist.level - 1; level >= 0; level-- {
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// if forward is not in range than move forward
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for n.level[level].forward != nil && !min.less(n.level[level].forward.Score) {
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n = n.level[level].forward
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}
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}
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/* This is an inner range, so the next node cannot be NULL. */
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n = n.level[0].forward
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if !max.greater(n.Score) {
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return nil
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}
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return n
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}
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func (skiplist *skiplist) getLastInScoreRange(min *ScoreBorder, max *ScoreBorder) *Node {
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if !skiplist.hasInRange(min, max) {
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return nil
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}
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n := skiplist.header
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// scan from top level
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for level := skiplist.level - 1; level >= 0; level-- {
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for n.level[level].forward != nil && max.greater(n.level[level].forward.Score) {
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n = n.level[level].forward
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}
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}
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if !min.less(n.Score) {
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return nil
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}
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return n
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}
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/*
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* return removed elements
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*/
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func (skiplist *skiplist) RemoveRangeByScore(min *ScoreBorder, max *ScoreBorder) (removed []*Element) {
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update := make([]*Node, maxLevel)
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removed = make([]*Element, 0)
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// find backward nodes (of target range) or last node of each level
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node := skiplist.header
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for i := skiplist.level - 1; i >= 0; i-- {
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for node.level[i].forward != nil {
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if min.less(node.level[i].forward.Score) { // already in range
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break
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}
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node = node.level[i].forward
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}
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update[i] = node
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}
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// node is the first one within range
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node = node.level[0].forward
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// remove nodes in range
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for node != nil {
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if !max.greater(node.Score) { // already out of range
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break
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}
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next := node.level[0].forward
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removedElement := node.Element
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removed = append(removed, &removedElement)
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skiplist.removeNode(node, update)
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node = next
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}
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return removed
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}
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// 1-based rank, including start, exclude stop
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func (skiplist *skiplist) RemoveRangeByRank(start int64, stop int64) (removed []*Element) {
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var i int64 = 0 // rank of iterator
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update := make([]*Node, maxLevel)
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removed = make([]*Element, 0)
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// scan from top level
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node := skiplist.header
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for level := skiplist.level - 1; level >= 0; level-- {
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for node.level[level].forward != nil && (i+node.level[level].span) < start {
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i += node.level[level].span
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node = node.level[level].forward
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}
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update[level] = node
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}
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i++
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node = node.level[0].forward // first node in range
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// remove nodes in range
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for node != nil && i < stop {
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next := node.level[0].forward
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removedElement := node.Element
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removed = append(removed, &removedElement)
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skiplist.removeNode(node, update)
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node = next
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i++
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}
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return removed
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}
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