add some util funcs

+package validation
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+const (
+	VALIDTAG = "valid"
+)
+
+var (
+	// key: function name
+	// value: the number of parameters
+	funcs = make(map[string]int)
+
+	// doesn't belong to validation functions
+	unFuncs = map[string]bool{
+		"Clear":     true,
+		"HasErrors": true,
+		"ErrorMap":  true,
+		"Error":     true,
+		"apply":     true,
+		"Check":     true,
+		"Valid":     true,
+	}
+)
+
+func init() {
+	v := &Validation{}
+	t := reflect.TypeOf(v)
+	for i := 0; i < t.NumMethod(); i++ {
+		m := t.Method(i)
+		if !unFuncs[m.Name] {
+			funcs[m.Name] = m.Type.NumIn() - 3
+		}
+	}
+}
+
+type ValidFunc struct {
+	Name   string
+	Params []interface{}
+}
+
+func isStruct(t reflect.Type) bool {
+	return t.Kind() == reflect.Struct
+}
+
+func isStructPtr(t reflect.Type) bool {
+	return t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Struct
+}
+
+func getValidFuncs(f reflect.StructField) (vfs []ValidFunc, err error) {
+	tag := f.Tag.Get(VALIDTAG)
+	if len(tag) == 0 {
+		return
+	}
+	fs := strings.Split(tag, ";")
+	for _, vfunc := range fs {
+		var vf ValidFunc
+		vf, err = parseFunc(vfunc)
+		if err != nil {
+			return
+		}
+		vfs = append(vfs, vf)
+	}
+	return
+}
+
+func parseFunc(vfunc string) (v ValidFunc, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = r.(error)
+		}
+	}()
+
+	vfunc = strings.TrimSpace(vfunc)
+	start := strings.Index(vfunc, "(")
+	var num int
+
+	// doesn't need parameter valid function
+	if start == -1 {
+		if num, err = numIn(vfunc); err != nil {
+			return
+		}
+		if num != 0 {
+			err = fmt.Errorf("%s require %d parameters", vfunc, num)
+			return
+		}
+		v = ValidFunc{Name: vfunc}
+		return
+	}
+
+	end := strings.Index(vfunc, ")")
+	if end == -1 {
+		err = fmt.Errorf("invalid valid function")
+		return
+	}
+
+	name := strings.TrimSpace(vfunc[:start])
+	if num, err = numIn(name); err != nil {
+		return
+	}
+
+	params := strings.Split(vfunc[start+1:end], ",")
+	// the num of param must be equal
+	if num != len(params) {
+		err = fmt.Errorf("%s require %d parameters", name, num)
+		return
+	}
+
+	v = ValidFunc{name, trim(params)}
+	return
+}
+
+func numIn(name string) (num int, err error) {
+	num, ok := funcs[name]
+	if !ok {
+		err = fmt.Errorf("doesn't exsits %s valid function", name)
+	}
+	return
+}
+
+func trim(s []string) []interface{} {
+	ts := make([]interface{}, len(s))
+	for i := 0; i < len(s); i++ {
+		ts[i] = strings.TrimSpace(s[i])
+	}
+	return ts
+}

+package validation
+
+import (
+	"reflect"
+	"testing"
+)
+
+type user struct {
+	Id   int
+	Tag  string `valid:"Maxx(aa)"`
+	Name string `valid:"Required"`
+	Age  int    `valid:"Required;Range(1, 140)"`
+}
+
+func TestGetValidFuncs(t *testing.T) {
+	u := user{Name: "test", Age: 1}
+	tf := reflect.TypeOf(u)
+	var vfs []ValidFunc
+	var err error
+
+	f, _ := tf.FieldByName("Id")
+	if vfs, err = getValidFuncs(f); err != nil {
+		t.Fatal(err)
+	}
+	if len(vfs) != 0 {
+		t.Fatal("should get none ValidFunc")
+	}
+
+	f, _ = tf.FieldByName("Tag")
+	if vfs, err = getValidFuncs(f); err.Error() != "doesn't exsits Maxx valid function" {
+		t.Fatal(err)
+	}
+
+	f, _ = tf.FieldByName("Name")
+	if vfs, err = getValidFuncs(f); err != nil {
+		t.Fatal(err)
+	}
+	if len(vfs) != 1 {
+		t.Fatal("should get 1 ValidFunc")
+	}
+	if vfs[0].Name != "Required" && len(vfs[0].Params) != 0 {
+		t.Error("Required funcs should be got")
+	}
+
+	f, _ = tf.FieldByName("Age")
+	if vfs, err = getValidFuncs(f); err != nil {
+		t.Fatal(err)
+	}
+	if len(vfs) != 2 {
+		t.Fatal("should get 2 ValidFunc")
+	}
+	if vfs[0].Name != "Required" && len(vfs[0].Params) != 0 {
+		t.Error("Required funcs should be got")
+	}
+	if vfs[1].Name != "Range" && len(vfs[1].Params) != 2 {
+		t.Error("Range funcs should be got")
+	}
+}