diff --git a/src/util_str.rs b/src/util_str.rs
new file mode 100644
index 0000000..28ac26e
--- /dev/null
+++ b/src/util_str.rs
@@ -0,0 +1,30 @@
+
+
+pub fn split_kv(s: &str, split: char) -> (String, String) {
+    let mut k = String::new();
+    let mut v = String::new();
+
+    let mut is_splited = false;
+    let cs = s.chars();
+    for c in cs {
+        if is_splited {
+            v.push(c);
+        } else if c == split {
+            is_splited = true;
+        } else {
+            k.push(c);
+        }
+    }
+
+    (k, v)
+}
+
+
+#[test]
+fn test_split_kv() {
+    assert_eq!(("".to_owned(), "".to_owned()), split_kv("", '='));
+    assert_eq!(("aaaa".to_owned(), "".to_owned()), split_kv("aaaa", '='));
+    assert_eq!(("".to_owned(), "aaaa".to_owned()), split_kv("=aaaa", '='));
+    assert_eq!(("aa".to_owned(), "bb".to_owned()), split_kv("aa=bb", '='));
+    assert_eq!(("aa".to_owned(), "bb".to_owned()), split_kv("aa:bb", ':'));
+}