1 files changed, 19 insertions, 1 deletions
diff --git a/lib/cString.ml b/lib/cString.ml
index b54c23c5b2..fd375c5c34 100644
--- a/lib/cString.ml
+++ b/lib/cString.ml
@@ -46,6 +46,7 @@ module type ExtS =
 sig
   include S
   external equal : string -> string -> bool = "caml_string_equal" "noalloc"
+  val is_empty : string -> bool
   val explode : string -> string list
   val implode : string list -> string
   val strip : string -> string
@@ -56,6 +57,7 @@ sig
   val plural : int -> string -> string
   val ordinal : int -> string
   val split : char -> string -> string list
+  val is_sub : string -> string -> int -> bool
 end
 
 include String
@@ -77,6 +79,8 @@ let is_blank = function
   | ' ' | '\r' | '\t' | '\n' -> true
   | _ -> false
 
+let is_empty s = String.length s = 0
+
 let strip s =
   let n = String.length s in
   let rec lstrip_rec i =
@@ -100,7 +104,7 @@ let map f s =
 
 let drop_simple_quotes s =
   let n = String.length s in
-  if n > 2 & s.[0] = '\'' & s.[n-1] = '\'' then String.sub s 1 (n-2) else s
+  if n > 2 && s.[0] = '\'' & s.[n-1] = '\'' then String.sub s 1 (n-2) else s
 
 (* substring searching... *)
 
@@ -130,6 +134,20 @@ let string_contains ~where ~what =
   with
       Not_found -> false
 
+let is_sub p s off =
+  let lp = String.length p in
+  let ls = String.length s in
+  if ls < off + lp then false
+  else
+    let rec aux i =
+      if lp <= i then true
+      else
+        let cp = String.unsafe_get p i in
+        let cs = String.unsafe_get s (off + i) in
+        if cp = cs then aux (succ i) else false
+    in
+    aux 0
+
 let plural n s = if n<>1 then s^"s" else s
 
 let ordinal n =