crockford base32: remove padding

src/b32.ml

@@ -1,4 +1,3 @@
-(* TODO test *)
 (* Crockford's variant of Base32
    http://www.crockford.com/wrmg/base32.html
    except that:
@@ -6,11 +5,18 @@
      - '-' is not allowed
      - checksum is not allowed *)
 
-(* 'I' 'L' 'O' 'U' excluded *)
+(* 'I' 'L' 'O' 'U' excluded
+   no '=' padding in encoded string *)
 type t = string
 
 let alphabet = Base32.make_alphabet "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
-let encode s = Base32.encode_string ~alphabet s
+
+let encode s =
+  let s = Base32.encode_string ~alphabet s in
+  (* remove '=' padding *)
+  match String.index_opt s '=' with
+  | None -> s
+  | Some i -> String.sub s 0 i
 
 let decode s =
   let s =
@@ -23,6 +29,10 @@ let decode s =
         | c -> c)
       s
   in
+  (* restore padding for base32 lib *)
+  let n = 8 - (String.length s mod 8) in
+  let pad = String.make n '=' in
+  let s = s ^ pad in
   match Base32.decode ~alphabet ~off:0 ~len:(String.length s) s with
   | Error (`Msg e) -> Error e
   | Ok v -> Ok v