Lab skiplist

README.md

@@ -1,3 +1,3 @@
 # corekv
 
-corekv 是一个用来高效率的验证kv引擎feature的项目。
+corekv is a project for efficiently verifying kv engine features.

utils/skiplist.go

@@ -1,6 +1,7 @@
 package utils
 
 import (
+	"bytes"
 	"github.com/hardcore-os/corekv/utils/codec"
 	"math/rand"
 	"sync"
@@ -10,22 +11,6 @@ const (
 	defaultMaxLevel = 48
 )
 
-type SkipList struct {
-	header *Element
-
-	rand *rand.Rand
-
-	maxLevel int
-	length   int
-	lock     sync.RWMutex
-	size     int64
-}
-
-func NewSkipList() *SkipList {
-	//implement me here!!!
-	return nil
-}
-
 type Element struct {
 	levels []*Element
 	entry  *codec.Entry
@@ -34,7 +19,7 @@ type Element struct {
 
 func newElement(score float64, entry *codec.Entry, level int) *Element {
 	return &Element{
-		levels: make([]*Element, level),
+		levels: make([]*Element, level+1),
 		entry:  entry,
 		score:  score,
 	}
@@ -44,13 +29,85 @@ func (elem *Element) Entry() *codec.Entry {
 	return elem.entry
 }
 
+// 跳表的基础实现
+type SkipList struct {
+	header   *Element
+	rand     *rand.Rand
+	maxLevel int
+	length   int
+	lock     sync.RWMutex
+	size     int64
+}
+
+func NewSkipList() *SkipList {
+	header := &Element{
+		levels: make([]*Element, defaultMaxLevel),
+	}
+	return &SkipList{
+		header:   header,
+		maxLevel: defaultMaxLevel - 1,
+		rand:     r,
+	}
+}
+
 func (list *SkipList) Add(data *codec.Entry) error {
-	//implement me here!!!
+	list.lock.Lock()
+	defer list.lock.Unlock()
+
+	prevs := make([]*Element, list.maxLevel+1)
+
+	key := data.Key
+	keyScore := list.calcScore(key)
+	header, maxLevel := list.header, list.maxLevel
+	prev := header
+	for i := maxLevel; i >= 0; i-- {
+		for ne := prev.levels[i]; ne != nil; ne = prev.levels[i] {
+			if comp := list.compare(keyScore, key, ne); comp <= 0 {
+				if comp == 0 {
+					ne.entry = data
+					return nil
+				} else {
+					prev = ne
+				}
+			} else {
+				break
+			}
+		}
+		prevs[i] = prev
+	}
+
+	randLevel, keyScore := list.randLevel(), list.calcScore(key)
+	e := newElement(keyScore, data, randLevel)
+
+	for i := randLevel; i >= 0; i-- {
+		ne := prevs[i].levels[i]
+		prevs[i].levels[i] = e
+		e.levels[i] = ne
+	}
+
 	return nil
 }
 
 func (list *SkipList) Search(key []byte) (e *codec.Entry) {
-	//implement me here!!!
+	list.lock.RLock()
+	defer list.lock.RUnlock()
+
+	keyScore := list.calcScore(key)
+	header, maxLevel := list.header, list.maxLevel
+	prev := header
+	for i := maxLevel; i >= 0; i-- {
+		for ne := prev.levels[i]; ne != nil; ne = prev.levels[i] {
+			if comp := list.compare(keyScore, key, ne); comp <= 0 {
+				if comp == 0 {
+					return ne.entry
+				} else {
+					prev = ne
+				}
+			} else {
+				break
+			}
+		}
+	}
 	return nil
 }
 
@@ -72,20 +129,29 @@ func (list *SkipList) calcScore(key []byte) (score float64) {
 	}
 
 	score = float64(hash)
-	return
+	return score
 }
 
 func (list *SkipList) compare(score float64, key []byte, next *Element) int {
-	//implement me here!!!
-	return 0
+	if score == next.score {
+		return bytes.Compare(key, next.entry.Key)
+	}
+	if score < next.score {
+		return -1
+	} else {
+		return 1
+	}
 }
 
 func (list *SkipList) randLevel() int {
-	//implement me here!!!
-	return 0
+	for i := 0; i < list.maxLevel; i++ {
+		if list.rand.Intn(2) == 0 {
+			return i
+		}
+	}
+	return list.maxLevel
 }
 
 func (list *SkipList) Size() int64 {
-	//implement me here!!!
-	return 0
+	return list.size
 }

utils/skiplist_test.go

@@ -2,11 +2,12 @@ package utils
 
 import (
 	"fmt"
+	"sync"
+	"testing"
+
 	"github.com/hardcore-os/corekv/utils/codec"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"sync"
-	"testing"
 )
 
 func RandString(len int) string {
@@ -27,7 +28,7 @@ func TestSkipList_compare(t *testing.T) {
 	}
 
 	byte1 := []byte("1")
-	byte2 := []byte("2")
+	byte2 := []byte("1")
 	entry1 := codec.NewEntry(byte1, byte1)
 
 	byte1score := list.calcScore(byte1)
@@ -39,7 +40,7 @@ func TestSkipList_compare(t *testing.T) {
 		score:  byte2score,
 	}
 
-	assert.Equal(t, list.compare(byte1score, byte1, elem), -1)
+	assert.Equal(t, list.compare(byte1score, byte1, elem), 0)
 }
 
 func TestSkipListBasicCRUD(t *testing.T) {