container/gtree: refactor code with gods package (#3595)

container/gtree/gtree_btree.go

@@ -7,32 +7,21 @@
 package gtree
 
 import (
-	"bytes"
-	"context"
 	"fmt"
-	"strings"
 
+	"github.com/emirpasic/gods/trees/btree"
 	"github.com/gogf/gf/v2/container/gvar"
-	"github.com/gogf/gf/v2/internal/intlog"
-	"github.com/gogf/gf/v2/internal/json"
 	"github.com/gogf/gf/v2/internal/rwmutex"
+	"github.com/gogf/gf/v2/text/gstr"
 	"github.com/gogf/gf/v2/util/gconv"
 )
 
 // BTree holds elements of the B-tree.
 type BTree struct {
 	mu         rwmutex.RWMutex
-	root       *BTreeNode
 	comparator func(v1, v2 interface{}) int
-	size       int // Total number of keys in the tree
 	m          int // order (maximum number of children)
-}
-
-// BTreeNode is a single element within the tree.
-type BTreeNode struct {
-	Parent   *BTreeNode
-	Entries  []*BTreeEntry // Contained keys in node
-	Children []*BTreeNode  // Children nodes
+	tree       *btree.Tree
 }
 
 // BTreeEntry represents the key-value pair contained within nodes.
@@ -46,13 +35,11 @@ type BTreeEntry struct {
 // which is false in default.
 // Note that the `m` must be greater or equal than 3, or else it panics.
 func NewBTree(m int, comparator func(v1, v2 interface{}) int, safe ...bool) *BTree {
-	if m < 3 {
-		panic("Invalid order, should be at least 3")
-	}
 	return &BTree{
-		comparator: comparator,
 		mu:         rwmutex.Create(safe...),
 		m:          m,
+		comparator: comparator,
+		tree:       btree.NewWith(m, comparator),
 	}
 }
 
@@ -81,21 +68,6 @@ func (tree *BTree) Set(key interface{}, value interface{}) {
 	tree.doSet(key, value)
 }
 
-// doSet inserts key-value pair node into the tree.
-// If key already exists, then its value is updated with the new value.
-func (tree *BTree) doSet(key interface{}, value interface{}) {
-	entry := &BTreeEntry{Key: key, Value: value}
-	if tree.root == nil {
-		tree.root = &BTreeNode{Entries: []*BTreeEntry{entry}, Children: []*BTreeNode{}}
-		tree.size++
-		return
-	}
-
-	if tree.insert(tree.root, entry) {
-		tree.size++
-	}
-}
-
 // Sets batch sets key-values to the tree.
 func (tree *BTree) Sets(data map[interface{}]interface{}) {
 	tree.mu.Lock()
@@ -107,39 +79,19 @@ func (tree *BTree) Sets(data map[interface{}]interface{}) {
 
 // Get searches the node in the tree by `key` and returns its value or nil if key is not found in tree.
 func (tree *BTree) Get(key interface{}) (value interface{}) {
-	value, _ = tree.Search(key)
-	return
-}
-
-// doSetWithLockCheck checks whether value of the key exists with mutex.Lock,
-// if not exists, set value to the map with given `key`,
-// or else just return the existing value.
-//
-// When setting value, if `value` is type of <func() interface {}>,
-// it will be executed with mutex.Lock of the hash map,
-// and its return value will be set to the map with `key`.
-//
-// It returns value with given `key`.
-func (tree *BTree) doSetWithLockCheck(key interface{}, value interface{}) interface{} {
 	tree.mu.Lock()
 	defer tree.mu.Unlock()
-	if entry := tree.doSearch(key); entry != nil {
-		return entry.Value
-	}
-	if f, ok := value.(func() interface{}); ok {
-		value = f()
-	}
-	if value != nil {
-		tree.doSet(key, value)
-	}
-	return value
+	value, _ = tree.doGet(key)
+	return
 }
 
 // GetOrSet returns the value by key,
 // or sets value with given `value` if it does not exist and then returns this value.
 func (tree *BTree) GetOrSet(key interface{}, value interface{}) interface{} {
-	if v, ok := tree.Search(key); !ok {
-		return tree.doSetWithLockCheck(key, value)
+	tree.mu.Lock()
+	defer tree.mu.Unlock()
+	if v, ok := tree.doGet(key); !ok {
+		return tree.doSet(key, value)
 	} else {
 		return v
 	}
@@ -149,8 +101,10 @@ func (tree *BTree) GetOrSet(key interface{}, value interface{}) interface{} {
 // or sets value with returned value of callback function `f` if it does not exist
 // and then returns this value.
 func (tree *BTree) GetOrSetFunc(key interface{}, f func() interface{}) interface{} {
-	if v, ok := tree.Search(key); !ok {
-		return tree.doSetWithLockCheck(key, f())
+	tree.mu.Lock()
+	defer tree.mu.Unlock()
+	if v, ok := tree.doGet(key); !ok {
+		return tree.doSet(key, f())
 	} else {
 		return v
 	}
@@ -163,8 +117,10 @@ func (tree *BTree) GetOrSetFunc(key interface{}, f func() interface{}) interface
 // GetOrSetFuncLock differs with GetOrSetFunc function is that it executes function `f`
 // with mutex.Lock of the hash map.
 func (tree *BTree) GetOrSetFuncLock(key interface{}, f func() interface{}) interface{} {
-	if v, ok := tree.Search(key); !ok {
-		return tree.doSetWithLockCheck(key, f)
+	tree.mu.Lock()
+	defer tree.mu.Unlock()
+	if v, ok := tree.doGet(key); !ok {
+		return tree.doSet(key, f)
 	} else {
 		return v
 	}
@@ -197,8 +153,10 @@ func (tree *BTree) GetVarOrSetFuncLock(key interface{}, f func() interface{}) *g
 // SetIfNotExist sets `value` to the map if the `key` does not exist, and then returns true.
 // It returns false if `key` exists, and `value` would be ignored.
 func (tree *BTree) SetIfNotExist(key interface{}, value interface{}) bool {
-	if !tree.Contains(key) {
-		tree.doSetWithLockCheck(key, value)
+	tree.mu.Lock()
+	defer tree.mu.Unlock()
+	if _, ok := tree.doGet(key); !ok {
+		tree.doSet(key, value)
 		return true
 	}
 	return false
@@ -207,8 +165,10 @@ func (tree *BTree) SetIfNotExist(key interface{}, value interface{}) bool {
 // SetIfNotExistFunc sets value with return value of callback function `f`, and then returns true.
 // It returns false if `key` exists, and `value` would be ignored.
 func (tree *BTree) SetIfNotExistFunc(key interface{}, f func() interface{}) bool {
-	if !tree.Contains(key) {
-		tree.doSetWithLockCheck(key, f())
+	tree.mu.Lock()
+	defer tree.mu.Unlock()
+	if _, ok := tree.doGet(key); !ok {
+		tree.doSet(key, f())
 		return true
 	}
 	return false
@@ -220,29 +180,29 @@ func (tree *BTree) SetIfNotExistFunc(key interface{}, f func() interface{}) bool
 // SetIfNotExistFuncLock differs with SetIfNotExistFunc function is that
 // it executes function `f` with mutex.Lock of the hash map.
 func (tree *BTree) SetIfNotExistFuncLock(key interface{}, f func() interface{}) bool {
-	if !tree.Contains(key) {
-		tree.doSetWithLockCheck(key, f)
+	tree.mu.Lock()
+	defer tree.mu.Unlock()
+	if _, ok := tree.doGet(key); !ok {
+		tree.doSet(key, f)
 		return true
 	}
 	return false
 }
 
-// Contains checks whether `key` exists in the tree.
-func (tree *BTree) Contains(key interface{}) bool {
-	_, ok := tree.Search(key)
-	return ok
+// Search searches the tree with given `key`.
+// Second return parameter `found` is true if key was found, otherwise false.
+func (tree *BTree) Search(key interface{}) (value interface{}, found bool) {
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
+	return tree.tree.Get(key)
 }
 
-// doRemove removes the node from the tree by key.
-// Key should adhere to the comparator's type assertion, otherwise method panics.
-func (tree *BTree) doRemove(key interface{}) (value interface{}) {
-	node, index, found := tree.searchRecursively(tree.root, key)
-	if found {
-		value = node.Entries[index].Value
-		tree.delete(node, index)
-		tree.size--
-	}
-	return
+// Contains checks whether `key` exists in the tree.
+func (tree *BTree) Contains(key interface{}) bool {
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
+	_, ok := tree.doGet(key)
+	return ok
 }
 
 // Remove removes the node from the tree by `key`.
@@ -263,42 +223,36 @@ func (tree *BTree) Removes(keys []interface{}) {
 
 // IsEmpty returns true if tree does not contain any nodes
 func (tree *BTree) IsEmpty() bool {
-	return tree.Size() == 0
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
+	return tree.tree.Size() == 0
 }
 
 // Size returns number of nodes in the tree.
 func (tree *BTree) Size() int {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	return tree.size
+	return tree.tree.Size()
 }
 
 // Keys returns all keys in asc order.
 func (tree *BTree) Keys() []interface{} {
-	keys := make([]interface{}, tree.Size())
-	index := 0
-	tree.IteratorAsc(func(key, value interface{}) bool {
-		keys[index] = key
-		index++
-		return true
-	})
-	return keys
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
+	return tree.tree.Keys()
 }
 
 // Values returns all values in asc order based on the key.
 func (tree *BTree) Values() []interface{} {
-	values := make([]interface{}, tree.Size())
-	index := 0
-	tree.IteratorAsc(func(key, value interface{}) bool {
-		values[index] = value
-		index++
-		return true
-	})
-	return values
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
+	return tree.tree.Values()
 }
 
 // Map returns all key-value items as map.
 func (tree *BTree) Map() map[interface{}]interface{} {
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
 	m := make(map[interface{}]interface{}, tree.Size())
 	tree.IteratorAsc(func(key, value interface{}) bool {
 		m[key] = value
@@ -309,6 +263,8 @@ func (tree *BTree) Map() map[interface{}]interface{} {
 
 // MapStrAny returns all key-value items as map[string]interface{}.
 func (tree *BTree) MapStrAny() map[string]interface{} {
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
 	m := make(map[string]interface{}, tree.Size())
 	tree.IteratorAsc(func(key, value interface{}) bool {
 		m[gconv.String(key)] = value
@@ -321,16 +277,14 @@ func (tree *BTree) MapStrAny() map[string]interface{} {
 func (tree *BTree) Clear() {
 	tree.mu.Lock()
 	defer tree.mu.Unlock()
-	tree.root = nil
-	tree.size = 0
+	tree.tree.Clear()
 }
 
 // Replace the data of the tree with given `data`.
 func (tree *BTree) Replace(data map[interface{}]interface{}) {
 	tree.mu.Lock()
 	defer tree.mu.Unlock()
-	tree.root = nil
-	tree.size = 0
+	tree.tree.Clear()
 	for k, v := range data {
 		tree.doSet(k, v)
 	}
@@ -340,65 +294,42 @@ func (tree *BTree) Replace(data map[interface{}]interface{}) {
 func (tree *BTree) Height() int {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	return tree.root.height()
+	return tree.tree.Height()
 }
 
 // Left returns the left-most (min) entry or nil if tree is empty.
 func (tree *BTree) Left() *BTreeEntry {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	node := tree.left(tree.root)
-	if node != nil {
-		return node.Entries[0]
-	}
+	node := tree.tree.Left()
+	if node == nil || node.Entries == nil || len(node.Entries) == 0 {
 		return nil
 	}
+	return &BTreeEntry{
+		Key:   node.Entries[0].Key,
+		Value: node.Entries[0].Value,
+	}
+}
 
 // Right returns the right-most (max) entry or nil if tree is empty.
 func (tree *BTree) Right() *BTreeEntry {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	node := tree.right(tree.root)
-	if node != nil {
-		return node.Entries[len(node.Entries)-1]
-	}
+	node := tree.tree.Right()
+	if node == nil || node.Entries == nil || len(node.Entries) == 0 {
 		return nil
 	}
+	return &BTreeEntry{
+		Key:   node.Entries[len(node.Entries)-1].Key,
+		Value: node.Entries[len(node.Entries)-1].Value,
+	}
+}
 
 // String returns a string representation of container (for debugging purposes)
 func (tree *BTree) String() string {
-	if tree == nil {
-		return ""
-	}
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	var buffer bytes.Buffer
-	if tree.size != 0 {
-		tree.output(&buffer, tree.root, 0, true)
-	}
-	return buffer.String()
-}
-
-// Search searches the tree with given `key`.
-// Second return parameter `found` is true if key was found, otherwise false.
-func (tree *BTree) Search(key interface{}) (value interface{}, found bool) {
-	tree.mu.RLock()
-	defer tree.mu.RUnlock()
-	node, index, found := tree.searchRecursively(tree.root, key)
-	if found {
-		return node.Entries[index].Value, true
-	}
-	return nil, false
-}
-
-// Search searches the tree with given `key` without mutex.
-// It returns the entry if found or otherwise nil.
-func (tree *BTree) doSearch(key interface{}) *BTreeEntry {
-	node, index, found := tree.searchRecursively(tree.root, key)
-	if found {
-		return node.Entries[index]
-	}
-	return nil
+	return gstr.Replace(tree.tree.String(), "BTree\n", "")
 }
 
 // Print prints the tree to stdout.
@@ -421,11 +352,13 @@ func (tree *BTree) IteratorFrom(key interface{}, match bool, f func(key, value i
 func (tree *BTree) IteratorAsc(f func(key, value interface{}) bool) {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	node := tree.left(tree.root)
-	if node == nil {
-		return
+	it := tree.tree.Iterator()
+	for it.Begin(); it.Next(); {
+		index, value := it.Key(), it.Value()
+		if ok := f(index, value); !ok {
+			break
+		}
 	}
-	tree.doIteratorAsc(node, node.Entries[0], 0, f)
 }
 
 // IteratorAscFrom iterates the tree readonly in ascending order with given callback function `f`.
@@ -435,59 +368,13 @@ func (tree *BTree) IteratorAsc(f func(key, value interface{}) bool) {
 func (tree *BTree) IteratorAscFrom(key interface{}, match bool, f func(key, value interface{}) bool) {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	node, index, found := tree.searchRecursively(tree.root, key)
-	if match {
-		if found {
-			tree.doIteratorAsc(node, node.Entries[index], index, f)
-		}
-	} else {
-		if index >= 0 && index < len(node.Entries) {
-			tree.doIteratorAsc(node, node.Entries[index], index, f)
-		}
-	}
-}
-
-func (tree *BTree) doIteratorAsc(node *BTreeNode, entry *BTreeEntry, index int, f func(key, value interface{}) bool) {
-	first := true
-loop:
-	if entry == nil {
+	var keys = tree.tree.Keys()
+	index, isIterator := tree.iteratorFromGetIndex(key, keys, match)
+	if !isIterator {
 		return
 	}
-	if !f(entry.Key, entry.Value) {
-		return
-	}
-	// Find current entry position in current node
-	if !first {
-		index, _ = tree.search(node, entry.Key)
-	} else {
-		first = false
-	}
-	// Try to go down to the child right of the current entry
-	if index+1 < len(node.Children) {
-		node = node.Children[index+1]
-		// Try to go down to the child left of the current node
-		for len(node.Children) > 0 {
-			node = node.Children[0]
-		}
-		// Return the left-most entry
-		entry = node.Entries[0]
-		goto loop
-	}
-	// Above assures that we have reached a leaf node, so return the next entry in current node (if any)
-	if index+1 < len(node.Entries) {
-		entry = node.Entries[index+1]
-		goto loop
-	}
-	// Reached leaf node and there are no entries to the right of the current entry, so go up to the parent
-	for node.Parent != nil {
-		node = node.Parent
-		// Find next entry position in current node (note: search returns the first equal or bigger than entry)
-		index, _ = tree.search(node, entry.Key)
-		// Check that there is a next entry position in current node
-		if index < len(node.Entries) {
-			entry = node.Entries[index]
-			goto loop
-		}
+	for ; index < len(keys); index++ {
+		f(keys[index], tree.Get(keys[index]))
 	}
 }
 
@@ -496,13 +383,13 @@ loop:
 func (tree *BTree) IteratorDesc(f func(key, value interface{}) bool) {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	node := tree.right(tree.root)
-	if node == nil {
-		return
+	it := tree.tree.Iterator()
+	for it.End(); it.Prev(); {
+		index, value := it.Key(), it.Value()
+		if ok := f(index, value); !ok {
+			break
+		}
 	}
-	index := len(node.Entries) - 1
-	entry := node.Entries[index]
-	tree.doIteratorDesc(node, entry, index, f)
 }
 
 // IteratorDescFrom iterates the tree readonly in descending order with given callback function `f`.
@@ -512,468 +399,70 @@ func (tree *BTree) IteratorDesc(f func(key, value interface{}) bool) {
 func (tree *BTree) IteratorDescFrom(key interface{}, match bool, f func(key, value interface{}) bool) {
 	tree.mu.RLock()
 	defer tree.mu.RUnlock()
-	node, index, found := tree.searchRecursively(tree.root, key)
-	if match {
-		if found {
-			tree.doIteratorDesc(node, node.Entries[index], index, f)
-		}
-	} else {
-		if index >= 0 && index < len(node.Entries) {
-			tree.doIteratorDesc(node, node.Entries[index], index, f)
-		}
-	}
-}
-
-// IteratorDesc iterates the tree readonly in descending order with given callback function `f`.
-// If `f` returns true, then it continues iterating; or false to stop.
-func (tree *BTree) doIteratorDesc(node *BTreeNode, entry *BTreeEntry, index int, f func(key, value interface{}) bool) {
-	first := true
-loop:
-	if entry == nil {
+	var keys = tree.tree.Keys()
+	index, isIterator := tree.iteratorFromGetIndex(key, keys, match)
+	if !isIterator {
 		return
 	}
-	if !f(entry.Key, entry.Value) {
-		return
+	for ; index >= 0; index-- {
+		f(keys[index], tree.Get(keys[index]))
 	}
-	// Find current entry position in current node
-	if !first {
-		index, _ = tree.search(node, entry.Key)
-	} else {
-		first = false
-	}
-	// Try to go down to the child left of the current entry
-	if index < len(node.Children) {
-		node = node.Children[index]
-		// Try to go down to the child right of the current node
-		for len(node.Children) > 0 {
-			node = node.Children[len(node.Children)-1]
-		}
-		// Return the right-most entry
-		entry = node.Entries[len(node.Entries)-1]
-		goto loop
-	}
-	// Above assures that we have reached a leaf node, so return the previous entry in current node (if any)
-	if index-1 >= 0 {
-		entry = node.Entries[index-1]
-		goto loop
-	}
-
-	// Reached leaf node and there are no entries to the left of the current entry, so go up to the parent
-	for node.Parent != nil {
-		node = node.Parent
-		// Find previous entry position in current node (note: search returns the first equal or bigger than entry)
-		index, _ = tree.search(node, entry.Key)
-		// Check that there is a previous entry position in current node
-		if index-1 >= 0 {
-			entry = node.Entries[index-1]
-			goto loop
-		}
-	}
-}
-
-func (tree *BTree) output(buffer *bytes.Buffer, node *BTreeNode, level int, isTail bool) {
-	for e := 0; e < len(node.Entries)+1; e++ {
-		if e < len(node.Children) {
-			tree.output(buffer, node.Children[e], level+1, true)
-		}
-		if e < len(node.Entries) {
-			if _, err := buffer.WriteString(strings.Repeat("    ", level)); err != nil {
-				intlog.Errorf(context.TODO(), `%+v`, err)
-			}
-			if _, err := buffer.WriteString(fmt.Sprintf("%v", node.Entries[e].Key) + "\n"); err != nil {
-				intlog.Errorf(context.TODO(), `%+v`, err)
-			}
-		}
-	}
-}
-
-func (node *BTreeNode) height() int {
-	h := 0
-	n := node
-	for ; n != nil; n = n.Children[0] {
-		h++
-		if len(n.Children) == 0 {
-			break
-		}
-	}
-	return h
-}
-
-func (tree *BTree) isLeaf(node *BTreeNode) bool {
-	return len(node.Children) == 0
-}
-
-// func (tree *BTree) isFull(node *BTreeNode) bool {
-//	return len(node.Entries) == tree.maxEntries()
-// }
-
-func (tree *BTree) shouldSplit(node *BTreeNode) bool {
-	return len(node.Entries) > tree.maxEntries()
-}
-
-func (tree *BTree) maxChildren() int {
-	return tree.m
-}
-
-func (tree *BTree) minChildren() int {
-	return (tree.m + 1) / 2 // ceil(m/2)
-}
-
-func (tree *BTree) maxEntries() int {
-	return tree.maxChildren() - 1
-}
-
-func (tree *BTree) minEntries() int {
-	return tree.minChildren() - 1
-}
-
-func (tree *BTree) middle() int {
-	// "-1" to favor right nodes to have more keys when splitting
-	return (tree.m - 1) / 2
-}
-
-// search does search only within the single node among its entries
-func (tree *BTree) search(node *BTreeNode, key interface{}) (index int, found bool) {
-	low, mid, high := 0, 0, len(node.Entries)-1
-	for low <= high {
-		mid = low + (high-low)/2
-		compare := tree.getComparator()(key, node.Entries[mid].Key)
-		switch {
-		case compare > 0:
-			low = mid + 1
-		case compare < 0:
-			high = mid - 1
-		case compare == 0:
-			return mid, true
-		}
-	}
-	return low, false
-}
-
-// searchRecursively searches recursively down the tree starting at the startNode
-func (tree *BTree) searchRecursively(startNode *BTreeNode, key interface{}) (node *BTreeNode, index int, found bool) {
-	if tree.size == 0 {
-		return nil, -1, false
-	}
-	node = startNode
-	for {
-		index, found = tree.search(node, key)
-		if found {
-			return node, index, true
-		}
-		if tree.isLeaf(node) {
-			return node, index, false
-		}
-		node = node.Children[index]
-	}
-}
-
-func (tree *BTree) insert(node *BTreeNode, entry *BTreeEntry) (inserted bool) {
-	if tree.isLeaf(node) {
-		return tree.insertIntoLeaf(node, entry)
-	}
-	return tree.insertIntoInternal(node, entry)
-}
-
-func (tree *BTree) insertIntoLeaf(node *BTreeNode, entry *BTreeEntry) (inserted bool) {
-	insertPosition, found := tree.search(node, entry.Key)
-	if found {
-		node.Entries[insertPosition] = entry
-		return false
-	}
-	// Insert entry's key in the middle of the node
-	node.Entries = append(node.Entries, nil)
-	copy(node.Entries[insertPosition+1:], node.Entries[insertPosition:])
-	node.Entries[insertPosition] = entry
-	tree.split(node)
-	return true
-}
-
-func (tree *BTree) insertIntoInternal(node *BTreeNode, entry *BTreeEntry) (inserted bool) {
-	insertPosition, found := tree.search(node, entry.Key)
-	if found {
-		node.Entries[insertPosition] = entry
-		return false
-	}
-	return tree.insert(node.Children[insertPosition], entry)
-}
-
-func (tree *BTree) split(node *BTreeNode) {
-	if !tree.shouldSplit(node) {
-		return
-	}
-
-	if node == tree.root {
-		tree.splitRoot()
-		return
-	}
-
-	tree.splitNonRoot(node)
-}
-
-func (tree *BTree) splitNonRoot(node *BTreeNode) {
-	middle := tree.middle()
-	parent := node.Parent
-
-	left := &BTreeNode{Entries: append([]*BTreeEntry(nil), node.Entries[:middle]...), Parent: parent}
-	right := &BTreeNode{Entries: append([]*BTreeEntry(nil), node.Entries[middle+1:]...), Parent: parent}
-
-	// Move children from the node to be split into left and right nodes
-	if !tree.isLeaf(node) {
-		left.Children = append([]*BTreeNode(nil), node.Children[:middle+1]...)
-		right.Children = append([]*BTreeNode(nil), node.Children[middle+1:]...)
-		setParent(left.Children, left)
-		setParent(right.Children, right)
-	}
-
-	insertPosition, _ := tree.search(parent, node.Entries[middle].Key)
-
-	// Insert middle key into parent
-	parent.Entries = append(parent.Entries, nil)
-	copy(parent.Entries[insertPosition+1:], parent.Entries[insertPosition:])
-	parent.Entries[insertPosition] = node.Entries[middle]
-
-	// Set child left of inserted key in parent to the created left node
-	parent.Children[insertPosition] = left
-
-	// Set child right of inserted key in parent to the created right node
-	parent.Children = append(parent.Children, nil)
-	copy(parent.Children[insertPosition+2:], parent.Children[insertPosition+1:])
-	parent.Children[insertPosition+1] = right
-
-	tree.split(parent)
-}
-
-func (tree *BTree) splitRoot() {
-	middle := tree.middle()
-	left := &BTreeNode{Entries: append([]*BTreeEntry(nil), tree.root.Entries[:middle]...)}
-	right := &BTreeNode{Entries: append([]*BTreeEntry(nil), tree.root.Entries[middle+1:]...)}
-
-	// Move children from the node to be split into left and right nodes
-	if !tree.isLeaf(tree.root) {
-		left.Children = append([]*BTreeNode(nil), tree.root.Children[:middle+1]...)
-		right.Children = append([]*BTreeNode(nil), tree.root.Children[middle+1:]...)
-		setParent(left.Children, left)
-		setParent(right.Children, right)
-	}
-
-	// Root is a node with one entry and two children (left and right)
-	newRoot := &BTreeNode{
-		Entries:  []*BTreeEntry{tree.root.Entries[middle]},
-		Children: []*BTreeNode{left, right},
-	}
-
-	left.Parent = newRoot
-	right.Parent = newRoot
-	tree.root = newRoot
-}
-
-func setParent(nodes []*BTreeNode, parent *BTreeNode) {
-	for _, node := range nodes {
-		node.Parent = parent
-	}
-}
-
-func (tree *BTree) left(node *BTreeNode) *BTreeNode {
-	if tree.size == 0 {
-		return nil
-	}
-	current := node
-	for {
-		if tree.isLeaf(current) {
-			return current
-		}
-		current = current.Children[0]
-	}
-}
-
-func (tree *BTree) right(node *BTreeNode) *BTreeNode {
-	if tree.size == 0 {
-		return nil
-	}
-	current := node
-	for {
-		if tree.isLeaf(current) {
-			return current
-		}
-		current = current.Children[len(current.Children)-1]
-	}
-}
-
-// leftSibling returns the node's left sibling and child index (in parent) if it exists, otherwise (nil,-1)
-// key is any of keys in node (could even be deleted).
-func (tree *BTree) leftSibling(node *BTreeNode, key interface{}) (*BTreeNode, int) {
-	if node.Parent != nil {
-		index, _ := tree.search(node.Parent, key)
-		index--
-		if index >= 0 && index < len(node.Parent.Children) {
-			return node.Parent.Children[index], index
-		}
-	}
-	return nil, -1
-}
-
-// rightSibling returns the node's right sibling and child index (in parent) if it exists, otherwise (nil,-1)
-// key is any of keys in node (could even be deleted).
-func (tree *BTree) rightSibling(node *BTreeNode, key interface{}) (*BTreeNode, int) {
-	if node.Parent != nil {
-		index, _ := tree.search(node.Parent, key)
-		index++
-		if index < len(node.Parent.Children) {
-			return node.Parent.Children[index], index
-		}
-	}
-	return nil, -1
-}
-
-// delete deletes an entry in node at entries' index
-// ref.: https://en.wikipedia.org/wiki/B-tree#Deletion
-func (tree *BTree) delete(node *BTreeNode, index int) {
-	// deleting from a leaf node
-	if tree.isLeaf(node) {
-		deletedKey := node.Entries[index].Key
-		tree.deleteEntry(node, index)
-		tree.reBalance(node, deletedKey)
-		if len(tree.root.Entries) == 0 {
-			tree.root = nil
-		}
-		return
-	}
-
-	// deleting from an internal node
-	leftLargestNode := tree.right(node.Children[index]) // largest node in the left sub-tree (assumed to exist)
-	leftLargestEntryIndex := len(leftLargestNode.Entries) - 1
-	node.Entries[index] = leftLargestNode.Entries[leftLargestEntryIndex]
-	deletedKey := leftLargestNode.Entries[leftLargestEntryIndex].Key
-	tree.deleteEntry(leftLargestNode, leftLargestEntryIndex)
-	tree.reBalance(leftLargestNode, deletedKey)
-}
-
-// reBalance reBalances the tree after deletion if necessary and returns true, otherwise false.
-// Note that we first delete the entry and then call reBalance, thus the passed deleted key as reference.
-func (tree *BTree) reBalance(node *BTreeNode, deletedKey interface{}) {
-	// check if re-balancing is needed
-	if node == nil || len(node.Entries) >= tree.minEntries() {
-		return
-	}
-
-	// try to borrow from left sibling
-	leftSibling, leftSiblingIndex := tree.leftSibling(node, deletedKey)
-	if leftSibling != nil && len(leftSibling.Entries) > tree.minEntries() {
-		// rotate right
-		node.Entries = append([]*BTreeEntry{node.Parent.Entries[leftSiblingIndex]}, node.Entries...) // prepend parent's separator entry to node's entries
-		node.Parent.Entries[leftSiblingIndex] = leftSibling.Entries[len(leftSibling.Entries)-1]
-		tree.deleteEntry(leftSibling, len(leftSibling.Entries)-1)
-		if !tree.isLeaf(leftSibling) {
-			leftSiblingRightMostChild := leftSibling.Children[len(leftSibling.Children)-1]
-			leftSiblingRightMostChild.Parent = node
-			node.Children = append([]*BTreeNode{leftSiblingRightMostChild}, node.Children...)
-			tree.deleteChild(leftSibling, len(leftSibling.Children)-1)
-		}
-		return
-	}
-
-	// try to borrow from right sibling
-	rightSibling, rightSiblingIndex := tree.rightSibling(node, deletedKey)
-	if rightSibling != nil && len(rightSibling.Entries) > tree.minEntries() {
-		// rotate left
-		node.Entries = append(node.Entries, node.Parent.Entries[rightSiblingIndex-1]) // append parent's separator entry to node's entries
-		node.Parent.Entries[rightSiblingIndex-1] = rightSibling.Entries[0]
-		tree.deleteEntry(rightSibling, 0)
-		if !tree.isLeaf(rightSibling) {
-			rightSiblingLeftMostChild := rightSibling.Children[0]
-			rightSiblingLeftMostChild.Parent = node
-			node.Children = append(node.Children, rightSiblingLeftMostChild)
-			tree.deleteChild(rightSibling, 0)
-		}
-		return
-	}
-
-	// merge with siblings
-	if rightSibling != nil {
-		// merge with right sibling
-		node.Entries = append(node.Entries, node.Parent.Entries[rightSiblingIndex-1])
-		node.Entries = append(node.Entries, rightSibling.Entries...)
-		deletedKey = node.Parent.Entries[rightSiblingIndex-1].Key
-		tree.deleteEntry(node.Parent, rightSiblingIndex-1)
-		tree.appendChildren(node.Parent.Children[rightSiblingIndex], node)
-		tree.deleteChild(node.Parent, rightSiblingIndex)
-	} else if leftSibling != nil {
-		// merge with left sibling
-		entries := append([]*BTreeEntry(nil), leftSibling.Entries...)
-		entries = append(entries, node.Parent.Entries[leftSiblingIndex])
-		node.Entries = append(entries, node.Entries...)
-		deletedKey = node.Parent.Entries[leftSiblingIndex].Key
-		tree.deleteEntry(node.Parent, leftSiblingIndex)
-		tree.prependChildren(node.Parent.Children[leftSiblingIndex], node)
-		tree.deleteChild(node.Parent, leftSiblingIndex)
-	}
-
-	// make the merged node the root if its parent was the root and the root is empty
-	if node.Parent == tree.root && len(tree.root.Entries) == 0 {
-		tree.root = node
-		node.Parent = nil
-		return
-	}
-
-	// parent might be underflow, so try to reBalance if necessary
-	tree.reBalance(node.Parent, deletedKey)
-}
-
-func (tree *BTree) prependChildren(fromNode *BTreeNode, toNode *BTreeNode) {
-	children := append([]*BTreeNode(nil), fromNode.Children...)
-	toNode.Children = append(children, toNode.Children...)
-	setParent(fromNode.Children, toNode)
-}
-
-func (tree *BTree) appendChildren(fromNode *BTreeNode, toNode *BTreeNode) {
-	toNode.Children = append(toNode.Children, fromNode.Children...)
-	setParent(fromNode.Children, toNode)
-}
-
-func (tree *BTree) deleteEntry(node *BTreeNode, index int) {
-	copy(node.Entries[index:], node.Entries[index+1:])
-	node.Entries[len(node.Entries)-1] = nil
-	node.Entries = node.Entries[:len(node.Entries)-1]
-}
-
-func (tree *BTree) deleteChild(node *BTreeNode, index int) {
-	if index >= len(node.Children) {
-		return
-	}
-	copy(node.Children[index:], node.Children[index+1:])
-	node.Children[len(node.Children)-1] = nil
-	node.Children = node.Children[:len(node.Children)-1]
 }
 
 // MarshalJSON implements the interface MarshalJSON for json.Marshal.
-func (tree BTree) MarshalJSON() (jsonBytes []byte, err error) {
-	if tree.root == nil {
-		return []byte("null"), nil
-	}
-	buffer := bytes.NewBuffer(nil)
-	buffer.WriteByte('{')
-	tree.Iterator(func(key, value interface{}) bool {
-		valueBytes, valueJsonErr := json.Marshal(value)
-		if valueJsonErr != nil {
-			err = valueJsonErr
-			return false
-		}
-		if buffer.Len() > 1 {
-			buffer.WriteByte(',')
-		}
-		buffer.WriteString(fmt.Sprintf(`"%v":%s`, key, valueBytes))
-		return true
-	})
-	buffer.WriteByte('}')
-	return buffer.Bytes(), nil
+func (tree *BTree) MarshalJSON() (jsonBytes []byte, err error) {
+	tree.mu.RLock()
+	defer tree.mu.RUnlock()
+	return tree.tree.MarshalJSON()
 }
 
-// getComparator returns the comparator if it's previously set,
-// or else it panics.
-func (tree *BTree) getComparator() func(a, b interface{}) int {
-	if tree.comparator == nil {
-		panic("comparator is missing for tree")
+// doSet inserts key-value pair node into the tree.
+// If key already exists, then its value is updated with the new value.
+// If `value` is type of <func() interface {}>,
+// it will be executed and its return value will be set to the map with `key`.
+//
+// It returns value with given `key`.
+func (tree *BTree) doSet(key interface{}, value interface{}) interface{} {
+	if f, ok := value.(func() interface{}); ok {
+		value = f()
 	}
-	return tree.comparator
+	if value == nil {
+		return value
+	}
+	tree.tree.Put(key, value)
+	return value
+}
+
+// doGet get the value from the tree by key.
+func (tree *BTree) doGet(key interface{}) (value interface{}, ok bool) {
+	return tree.tree.Get(key)
+}
+
+// doRemove removes the node from the tree by key.
+// Key should adhere to the comparator's type assertion, otherwise method panics.
+func (tree *BTree) doRemove(key interface{}) (value interface{}) {
+	value, _ = tree.tree.Get(key)
+	tree.tree.Remove(key)
+	return
+}
+
+// iteratorFromGetIndex returns the index of the key in the keys slice.
+// The parameter `match` specifies whether starting iterating if the `key` is fully matched,
+// or else using index searching iterating.
+// If `isIterator` is true, iterator is available; or else not.
+func (tree *BTree) iteratorFromGetIndex(key interface{}, keys []interface{}, match bool) (index int, isIterator bool) {
+	if match {
+		for i, k := range keys {
+			if k == key {
+				isIterator = true
+				index = i
+			}
+		}
+	} else {
+		if i, ok := key.(int); ok {
+			isIterator = true
+			index = i
+		}
+	}
+	return
 }

go.mod

@@ -20,6 +20,7 @@ require (
 )
 
 require (
+	github.com/emirpasic/gods v1.18.1 // indirect
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect

go.sum

@@ -3,6 +3,8 @@ github.com/BurntSushi/toml v1.3.2/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbi
 github.com/clbanning/mxj/v2 v2.7.0 h1:WA/La7UGCanFe5NpHF0Q3DNtnCsVoxbPKuyBNHWRyME=
 github.com/clbanning/mxj/v2 v2.7.0/go.mod h1:hNiWqW14h+kc+MdF9C6/YoRfjEJoR3ou6tn/Qo+ve2s=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/emirpasic/gods v1.18.1 h1:FXtiHYKDGKCW2KzwZKx0iC0PQmdlorYgdFG9jPXJ1Bc=
+github.com/emirpasic/gods v1.18.1/go.mod h1:8tpGGwCnJ5H4r6BWwaV6OrWmMoPhUl5jm/FMNAnJvWQ=
 github.com/fatih/color v1.16.0 h1:zmkK9Ngbjj+K0yRhTVONQh1p/HknKYSlNT+vZCzyokM=
 github.com/fatih/color v1.16.0/go.mod h1:fL2Sau1YI5c0pdGEVCbKQbLXB6edEj1ZgiY4NijnWvE=
 github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=