diff --git a/util/deepcopy.go b/util/deepcopy.go
new file mode 100644
index 0000000..570718a
--- /dev/null
+++ b/util/deepcopy.go
@@ -0,0 +1,76 @@
+package util
+
+// reference: https://github.com/mohae/deepcopy
+import (
+	"reflect"
+)
+
+func deepCopy(dst, src reflect.Value) {
+	switch src.Kind() {
+	case reflect.Interface:
+		value := src.Elem()
+		if !value.IsValid() {
+			return
+		}
+		newValue := reflect.New(value.Type()).Elem()
+		deepCopy(newValue, value)
+		dst.Set(newValue)
+	case reflect.Ptr:
+		value := src.Elem()
+		if !value.IsValid() {
+			return
+		}
+		dst.Set(reflect.New(value.Type()))
+		deepCopy(dst.Elem(), value)
+	case reflect.Map:
+		dst.Set(reflect.MakeMap(src.Type()))
+		keys := src.MapKeys()
+		for _, key := range keys {
+			value := src.MapIndex(key)
+			newValue := reflect.New(value.Type()).Elem()
+			deepCopy(newValue, value)
+			dst.SetMapIndex(key, newValue)
+		}
+	case reflect.Slice:
+		dst.Set(reflect.MakeSlice(src.Type(), src.Len(), src.Cap()))
+		for i := 0; i < src.Len(); i++ {
+			deepCopy(dst.Index(i), src.Index(i))
+		}
+	case reflect.Struct:
+		typeSrc := src.Type()
+		for i := 0; i < src.NumField(); i++ {
+			value := src.Field(i)
+			tag := typeSrc.Field(i).Tag
+			if value.CanSet() && tag.Get("deepcopy") != "-" {
+				deepCopy(dst.Field(i), value)
+			}
+		}
+	default:
+		dst.Set(src)
+	}
+}
+
+func DeepCopy(dst, src interface{}) {
+	typeDst := reflect.TypeOf(dst)
+	typeSrc := reflect.TypeOf(src)
+	if typeDst != typeSrc {
+		panic("DeepCopy: " + typeDst.String() + " != " + typeSrc.String())
+	}
+	if typeSrc.Kind() != reflect.Ptr {
+		panic("DeepCopy: pass arguments by address")
+	}
+
+	valueDst := reflect.ValueOf(dst).Elem()
+	valueSrc := reflect.ValueOf(src).Elem()
+	if !valueDst.IsValid() || !valueSrc.IsValid() {
+		panic("DeepCopy: invalid arguments")
+	}
+
+	deepCopy(valueDst, valueSrc)
+}
+
+func DeepClone(v interface{}) interface{} {
+	dst := reflect.New(reflect.TypeOf(v)).Elem()
+	deepCopy(dst, reflect.ValueOf(v))
+	return dst.Interface()
+}
diff --git a/util/example_test.go b/util/example_test.go
new file mode 100644
index 0000000..db4cbbe
--- /dev/null
+++ b/util/example_test.go
@@ -0,0 +1,92 @@
+package util_test
+
+import (
+	"fmt"
+	"github.com/name5566/leaf/util"
+)
+
+func ExampleMap() {
+	m := new(util.Map)
+
+	fmt.Println(m.Get("key"))
+	m.Set("key", "value")
+	fmt.Println(m.Get("key"))
+	m.Del("key")
+	fmt.Println(m.Get("key"))
+
+	m.Set(1, "1")
+	m.Set(2, 2)
+	m.Set("3", 3)
+
+	fmt.Println(m.Len())
+
+	// Output:
+	// <nil>
+	// value
+	// <nil>
+	// 3
+}
+
+func ExampleRandGroup() {
+	i := util.RandGroup(0, 0, 50, 50)
+	switch i {
+	case 2, 3:
+		fmt.Println("ok")
+	}
+
+	// Output:
+	// ok
+}
+
+func ExampleRandInterval() {
+	v := util.RandInterval(-1, 1)
+	switch v {
+	case -1, 0, 1:
+		fmt.Println("ok")
+	}
+
+	// Output:
+	// ok
+}
+
+func ExampleRandIntervalN() {
+	r := util.RandIntervalN(-1, 0, 2)
+	if r[0] == -1 && r[1] == 0 ||
+		r[0] == 0 && r[1] == -1 {
+		fmt.Println("ok")
+	}
+
+	// Output:
+	// ok
+}
+
+func ExampleDeepCopy() {
+	src := []int{1, 2, 3}
+
+	var dst []int
+	util.DeepCopy(&dst, &src)
+
+	for _, v := range dst {
+		fmt.Println(v)
+	}
+
+	// Output:
+	// 1
+	// 2
+	// 3
+}
+
+func ExampleDeepClone() {
+	src := []int{1, 2, 3}
+
+	dst := util.DeepClone(src).([]int)
+
+	for _, v := range dst {
+		fmt.Println(v)
+	}
+
+	// Output:
+	// 1
+	// 2
+	// 3
+}
diff --git a/util/map.go b/util/map.go
new file mode 100644
index 0000000..dfba240
--- /dev/null
+++ b/util/map.go
@@ -0,0 +1,101 @@
+package util
+
+import (
+	"sync"
+)
+
+type Map struct {
+	sync.RWMutex
+	m map[interface{}]interface{}
+}
+
+func (m *Map) init() {
+	if m.m == nil {
+		m.m = make(map[interface{}]interface{})
+	}
+}
+
+func (m *Map) UnsafeGet(key interface{}) interface{} {
+	if m.m == nil {
+		return nil
+	} else {
+		return m.m[key]
+	}
+}
+
+func (m *Map) Get(key interface{}) interface{} {
+	m.RLock()
+	defer m.RUnlock()
+	return m.UnsafeGet(key)
+}
+
+func (m *Map) UnsafeSet(key interface{}, value interface{}) {
+	m.init()
+	m.m[key] = value
+}
+
+func (m *Map) Set(key interface{}, value interface{}) {
+	m.Lock()
+	defer m.Unlock()
+	m.UnsafeSet(key, value)
+}
+
+func (m *Map) TestAndSet(key interface{}, value interface{}) interface{} {
+	m.Lock()
+	defer m.Unlock()
+
+	m.init()
+
+	if v, ok := m.m[key]; ok {
+		return v
+	} else {
+		m.m[key] = value
+		return nil
+	}
+}
+
+func (m *Map) UnsafeDel(key interface{}) {
+	m.init()
+	delete(m.m, key)
+}
+
+func (m *Map) Del(key interface{}) {
+	m.Lock()
+	defer m.Unlock()
+	m.UnsafeDel(key)
+}
+
+func (m *Map) UnsafeLen() int {
+	if m.m == nil {
+		return 0
+	} else {
+		return len(m.m)
+	}
+}
+
+func (m *Map) Len() int {
+	m.RLock()
+	defer m.RUnlock()
+	return m.UnsafeLen()
+}
+
+func (m *Map) UnsafeRange(f func(interface{}, interface{})) {
+	if m.m == nil {
+		return
+	}
+	for k, v := range m.m {
+		f(k, v)
+	}
+}
+
+func (m *Map) RLockRange(f func(interface{}, interface{})) {
+	m.RLock()
+	defer m.RUnlock()
+	m.UnsafeRange(f)
+}
+
+func (m *Map) LockRange(f func(interface{}, interface{})) {
+	m.Lock()
+	defer m.Unlock()
+	m.UnsafeRange(f)
+}
diff --git a/util/rand.go b/util/rand.go
new file mode 100644
index 0000000..557c471
--- /dev/null
+++ b/util/rand.go
@@ -0,0 +1,91 @@
+package util
+
+import (
+	"math/rand"
+	"time"
+)
+
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
+func RandGroup(p ...uint32) int {
+	if p == nil {
+		panic("args not found")
+	}
+
+	r := make([]uint32, len(p))
+	for i := 0; i < len(p); i++ {
+		if i == 0 {
+			r[0] = p[0]
+		} else {
+			r[i] = r[i-1] + p[i]
+		}
+	}
+
+	rl := r[len(r)-1]
+	if rl == 0 {
+		return 0
+	}
+
+	rn := uint32(rand.Int63n(int64(rl)))
+	for i := 0; i < len(r); i++ {
+		if rn < r[i] {
+			return i
+		}
+	}
+
+	panic("bug")
+}
+
+func RandInterval(b1, b2 int32) int32 {
+	if b1 == b2 {
+		return b1
+	}
+
+	min, max := int64(b1), int64(b2)
+	if min > max {
+		min, max = max, min
+	}
+	return int32(rand.Int63n(max-min+1) + min)
+}
+
+func RandIntervalN(b1, b2 int32, n uint32) []int32 {
+	if b1 == b2 {
+		return []int32{b1}
+	}
+
+	min, max := int64(b1), int64(b2)
+	if min > max {
+		min, max = max, min
+	}
+	l := max - min + 1
+	if int64(n) > l {
+		n = uint32(l)
+	}
+
+	r := make([]int32, n)
+	m := make(map[int32]int32)
+	for i := uint32(0); i < n; i++ {
+		v := int32(rand.Int63n(l) + min)
+
+		if mv, ok := m[v]; ok {
+			r[i] = mv
+		} else {
+			r[i] = v
+		}
+
+		lv := int32(l - 1 + min)
+		if v != lv {
+			if mv, ok := m[lv]; ok {
+				m[v] = mv
+			} else {
+				m[v] = lv
+			}
+		}
+
+		l--
+	}
+
+	return r
+}
diff --git a/util/semaphore.go b/util/semaphore.go
new file mode 100644
index 0000000..16fd136
--- /dev/null
+++ b/util/semaphore.go
@@ -0,0 +1,15 @@
+package util
+
+type Semaphore chan struct{}
+
+func MakeSemaphore(n int) Semaphore {
+	return make(Semaphore, n)
+}
+
+func (s Semaphore) Acquire() {
+	s <- struct{}{}
+}
+
+func (s Semaphore) Release() {
+	<-s
+}