Add: StringUtils.Substring

StringUtils.go

@@ -33,3 +33,36 @@ func (s *StringUtils) LeftPad(str string, size int, padStr string) string {
 
 	return strings.Repeat(padStr, padCount) + str
 }
+
+func (s *StringUtils) Substring(str string, start, end int) string {
+	if str == "" {
+		return str
+	}
+
+	runes := []rune(str)
+
+	if end < 0 {
+		end = len(runes) + end
+	}
+	if start < 0 {
+		start = len(runes) + start
+	}
+
+	if end > len(str) {
+		end = len(str)
+	}
+
+	if start > end {
+		return EMPTY
+	}
+
+	if start < 0 {
+		start = 0
+	}
+
+	if end < 0 {
+		end = 0
+	}
+
+	return string(runes[start:end])
+}