string pattern match context check instead of regex lookahead assertion

lib.go

@@ -475,34 +475,35 @@ func bstrUnmarshal(s string) (result string) {
 		result += s[cursor:match[0]]
 		subStr := s[match[0]:match[1]]
 		if subStr == "_x005F_" {
+			cursor = match[1]
 			if l > match[1]+6 && !escapeExp.MatchString(s[match[1]:match[1]+6]) {
 				result += subStr
-				cursor = match[1]
-				continue
-			}
-			if l > match[1]+5 && s[match[1]:match[1]+5] == "x005F" {
-				result += "_"
-				cursor = match[1]
-				continue
-			}
-			if escapeExp.MatchString(subStr) {
-				result += "_"
-				cursor = match[1]
 				continue
 			}
+			result += "_"
+			continue
 		}
 		if bstrExp.MatchString(subStr) {
-			x, _ := strconv.Unquote(`"\u` + s[match[0]+2:match[1]-1] + `"`)
+			cursor = match[1]
+			v, err := strconv.Unquote(`"\u` + s[match[0]+2:match[1]-1] + `"`)
+			if err != nil {
+				if l > match[1]+6 && escapeExp.MatchString(s[match[1]:match[1]+6]) {
+					result += subStr[:6]
+					cursor = match[1] + 6
+					continue
+				}
+				result += subStr
+				continue
+			}
 			hasRune := false
-			for _, c := range string(x) {
+			for _, c := range v {
 				if unicode.IsControl(c) {
 					hasRune = true
 				}
 			}
 			if !hasRune {
-				result += string(x)
+				result += v
 			}
-			cursor = match[1]
 		}
 	}
 	if cursor < l {

lib_test.go

@@ -237,19 +237,22 @@ func TestGenXMLNamespace(t *testing.T) {
 
 func TestBstrUnmarshal(t *testing.T) {
 	bstrs := map[string]string{
-		"*_x0000_":                    "*",
 		"*":                           "*",
+		"*_x0000_":                    "*",
 		"*_x0008_":                    "*",
 		"_x0008_*":                    "*",
 		"*_x0008_*":                   "**",
 		"*_x4F60__x597D_":             "*你好",
+		"*_xG000_":                    "*_xG000_",
+		"*_xG05F_x0001_*":             "*_xG05F*",
 		"*_x005F__x0008_*":            "*_x005F_*",
 		"*_x005F_x0001_*":             "*_x0001_*",
+		"*_x005f_x005F__x0008_*":      "*_x005F_*",
+		"*_x005F_x005F_xG05F_x0006_*": "*_x005F_xG05F*",
 		"*_x005F_x005F_x005F_x0006_*": "*_x005F_x0006_*",
 		"_x005F__x0008_******":        "_x005F_******",
 		"******_x005F__x0008_":        "******_x005F_",
 		"******_x005F__x0008_******":  "******_x005F_******",
-		"*_x005F_x005F__x0008_*":      "*_x005F_*",
 	}
 	for bstr, expected := range bstrs {
 		assert.Equal(t, expected, bstrUnmarshal(bstr))