From 5776e0ba6e59563c0efd1b397e35a7e59de627f6 Mon Sep 17 00:00:00 2001
From: bandl <1658002533@qq.com>
Date: Tue, 12 Oct 2021 15:10:00 +0800
Subject: [PATCH] feat(util): add skiplist

---
 pkg/util/skiplist/skiplist.go | 307 ++++++++++++++++++++++++++++++++++
 1 file changed, 307 insertions(+)
 create mode 100644 pkg/util/skiplist/skiplist.go

diff --git a/pkg/util/skiplist/skiplist.go b/pkg/util/skiplist/skiplist.go
new file mode 100644
index 0000000..391f559
--- /dev/null
+++ b/pkg/util/skiplist/skiplist.go
@@ -0,0 +1,307 @@
+package skiplist
+
+import (
+	"crypto/rand"
+	"fmt"
+	"math"
+	"math/big"
+)
+
+type skipListNode struct {
+	score float64
+	val   interface{}
+	next  *skipListNode
+	down  *skipListNode
+	up    *skipListNode
+	pre   *skipListNode
+}
+
+func newSkipListNode(score float64, val interface{}) *skipListNode {
+	if val == nil {
+		return nil
+	}
+
+	return &skipListNode{
+		score: score,
+		val:   val,
+	}
+}
+
+type SkipList struct {
+	head   *skipListNode
+	tail   *skipListNode
+	length int
+	levels int // 单前层级
+
+	maxLevels int //  最大层级
+}
+
+func NewSkipList(maxLevel int) *SkipList {
+	skl := new(SkipList)
+	skl.head = &skipListNode{score: math.MinInt64}
+	skl.tail = &skipListNode{score: math.MaxInt64}
+
+	skl.head.next = skl.tail
+	skl.tail.pre = skl.head
+
+	skl.length = 0
+	skl.levels = 1
+	skl.maxLevels = maxLevel
+
+	return skl
+}
+
+func (s *SkipList) Length() int {
+	return s.length
+}
+
+func (s *SkipList) Levels() int {
+	return s.levels
+}
+
+func (s *SkipList) MaxLength() int {
+	return s.maxLevels
+}
+
+// Insert 插入数据
+func (s *SkipList) Insert(score float64, val interface{}) {
+
+	node := newSkipListNode(score, val)
+	f := s.searchNode(score)
+
+	s.insertAfter(f, node)
+
+	// 随机上升
+
+	for newLevel := 1; ; newLevel++ {
+
+		rander, _ := rand.Int(rand.Reader, big.NewInt(2))
+
+		if rander.Int64() == 0 || newLevel >= s.maxLevels {
+			break
+		}
+
+		// 上升层级
+		if newLevel >= s.levels && s.levels < s.maxLevels {
+			s.newLevels()
+		}
+
+		for f.up == nil {
+			f = f.pre
+		}
+
+		f = f.up
+
+		tmpNode := &skipListNode{score: score}
+		node.up = tmpNode
+		tmpNode.down = node
+		s.insertAfter(f, tmpNode)
+
+		node = tmpNode
+	}
+
+	s.length += 1
+}
+
+// Pop 弹出随机一个 score 值的 val
+func (s *SkipList) Pop(score float64) interface{} {
+	f := s.searchNode(score)
+	if f.score == score {
+		return nil
+	}
+	v := f.val
+
+	s.delSkipListNode(f)
+	return v
+}
+
+// Get 获取 随机一个 score 值的 val
+func (s *SkipList) Get(score float64) interface{} {
+	node := s.searchNode(score)
+	if node != nil && node.score == score {
+		return node.val
+	}
+	return nil
+}
+
+// GetAll 获取全部的 ALL
+func (s *SkipList) GetAll(score float64) []interface{} {
+	node := s.searchNode(score)
+	values := make([]interface{}, 0)
+	p := node
+
+	// pre
+	for p.score == score {
+		values = append(values, p.val)
+		p = p.pre
+	}
+
+	// next
+	p = node.next
+	for p.score == score {
+		values = append(values, p.val)
+		p = p.next
+	}
+
+	return values
+}
+
+// RemoveAll 删除全部
+func (s *SkipList) RemoveAll(score float64) {
+	node := s.searchNode(score)
+	p := node
+	delNode := make([]*skipListNode, 0)
+	// pre
+	for p.score == score {
+		delNode = append(delNode, p)
+		p = p.pre
+	}
+
+	// next
+	p = node.next
+	for p.score == score {
+		delNode = append(delNode, p)
+		p = p.next
+	}
+	s.delSkipListNode(delNode...)
+}
+
+// ClearLeft 删除 小等于 score 的全部节点
+func (s *SkipList) ClearLeft(score float64) *skipListNode {
+	head := s.head
+
+	for head.down != nil {
+		p := head
+		for p.score <= score {
+			p = p.next
+		}
+
+		head.next = p
+		p.pre = head
+		head = head.down
+	}
+
+	node := s.searchNode(score)
+	for node.score <= score {
+		node = node.next
+	}
+
+	oldNode := node.pre
+	head.next = node
+
+	node.pre = head
+	return oldNode
+}
+
+func (s *SkipList) PopLeft(score float64) []interface{} {
+	node := s.ClearLeft(score)
+	values := make([]interface{}, 0, 10)
+	for node.score != math.MinInt64 {
+		values = append(values, node.val)
+		node = node.pre
+	}
+	return values
+}
+
+// 查找节点位置
+func (s *SkipList) searchNode(score float64) *skipListNode {
+	p := s.head
+	for p != nil {
+		// 尾部是极大极小值
+		if score == p.score {
+			if p.down == nil {
+				return p
+			}
+			p = p.down
+			continue
+		}
+
+		if score > p.score && score < p.next.score {
+			if p.down == nil {
+				return p
+			}
+			p = p.down
+			continue
+		}
+
+		p = p.next
+	}
+
+	return p
+}
+
+// 在节点后插入新节点
+func (s *SkipList) insertAfter(pNode *skipListNode, newNode *skipListNode) {
+	newNode.next = pNode.next
+	newNode.pre = pNode
+	pNode.next.pre = newNode
+	pNode.next = newNode
+}
+
+// 添加 一个新的 levels 层
+func (s *SkipList) newLevels() {
+	newHead := &skipListNode{score: math.MinInt64}
+	newTail := &skipListNode{score: math.MaxInt64}
+
+	newHead.next = newTail
+	newTail.pre = newHead
+
+	s.head.up = newHead
+	newHead.down = s.head
+	s.tail.up = newTail
+	newTail.down = s.tail
+
+	s.head = newHead
+	s.tail = newTail
+	s.levels++
+}
+
+func (s *SkipList) debugPrint() {
+	mapScore := make(map[float64]int)
+	p := s.head
+	for p.down != nil {
+		p = p.down
+	}
+	index := 0
+	for p != nil {
+		mapScore[p.score] = index
+		p = p.next
+		index++
+	}
+	p = s.head
+	for i := 0; i < s.levels; i++ {
+		q := p
+		preIndex := 0
+		for q != nil {
+			s := q.score
+			if s == math.MinInt64 {
+				fmt.Printf("%s", "BEGIN")
+				q = q.next
+				continue
+			}
+			index := mapScore[s]
+			c := (index - preIndex - 1) * 6
+			for m := 0; m < c; m++ {
+				fmt.Print("-")
+			}
+			if s == math.MaxInt64 {
+				fmt.Printf("-->%s\n", "END")
+			} else {
+				fmt.Printf("-->%3d", int(s))
+				preIndex = index
+			}
+			q = q.next
+		}
+		p = p.down
+	}
+}
+
+func (s *SkipList) delSkipListNode(sKm ...*skipListNode) {
+	for _, f := range sKm {
+		for f != nil {
+			f.pre.next = f.next
+			f.next.pre = f.pre
+			f = f.up
+		}
+	}
+}