diff --git a/src/core/CCString.ml b/src/core/CCString.ml
index 260d9d69..240f9e06 100644
--- a/src/core/CCString.ml
+++ b/src/core/CCString.ml
@@ -585,6 +585,24 @@ let take n s =
   else
     s
 
+let take_while p s =
+  let i = ref 0 in
+  while !i < String.length s && p (String.unsafe_get s !i) do
+    incr i
+  done;
+  String.sub s 0 !i
+
+let rtake_while p s =
+  let s_len_pred = String.length s - 1 in
+  let i = ref s_len_pred in
+  while !i >= 0 && p (String.unsafe_get s !i) do
+    decr i
+  done ;
+  if !i < s_len_pred
+    then String.sub s (!i + 1) (s_len_pred - !i)
+  else
+    ""
+
 let drop n s =
   if n < String.length s then
     String.sub s n (String.length s - n)