diff --git a/src/multipart_form/dune b/src/multipart_form/dune
index 6ce7f437..6adfd691 100644
--- a/src/multipart_form/dune
+++ b/src/multipart_form/dune
@@ -2,4 +2,4 @@
  (name tiny_httpd_multipart_form_data)
  (public_name tiny_httpd.multipart-form-data)
  (synopsis "Port of multipart-form-data for tiny_httpd")
- (libraries iostream stringext))
+ (libraries iostream tiny_httpd))
diff --git a/src/multipart_form/tiny_httpd_multipart_form_data.ml b/src/multipart_form/tiny_httpd_multipart_form_data.ml
index ce753566..ff2d3050 100644
--- a/src/multipart_form/tiny_httpd_multipart_form_data.ml
+++ b/src/multipart_form/tiny_httpd_multipart_form_data.ml
@@ -1,337 +1,101 @@
-(* ported from https://github.com/cryptosense/multipart-form-data .
-   License: BSD-2 *)
+(* ported from https://github.com/cryptosense/multipart-form-data . *)
 
-open Utils_
+open Tiny_httpd
 
-(* TODO: redo some light form of lwt stream for porting purposes? *)
-module Stream_ = struct
-  type 'a t = { next: unit -> 'a option } [@@unboxed]
+type st = {
+  delim: string;
+  ic: Iostream.In.t;
+  buf_split: bytes;  (** Used to split on the delimiter *)
+  mutable buf_len: int;
+  buf_line: Buf.t;
+  mutable eof: bool;
+}
 
-  let from next : _ t = { next }
-  let[@inline] get (self : _ t) : _ option = self.next ()
+let create ?(buf_size = 64 * 1024) ~delim ic : st =
+  let ic = (ic : #Iostream.In.t :> Iostream.In.t) in
+  {
+    delim;
+    ic;
+    buf_split = Bytes.create buf_size;
+    buf_len = 0;
+    buf_line = Buf.create ~size:256 ();
+    eof = false;
+  }
 
-  let filter_map f (self : _ t) : _ t =
-    let rec next () =
-      match self.next () with
-      | None -> None
-      | Some x ->
-        (match f x with
-        | None -> next ()
-        | Some _ as r -> r)
+type chunk = Delim | Eof | Read of int
+
+let[@inline] min_len_ (self : st) : int = 2 + String.length self.delim
+
+let shift_left_ (self : st) n =
+  if n = self.buf_len then
+    self.buf_len <- 0
+  else (
+    assert (n < self.buf_len);
+    Bytes.blit self.buf_split n self.buf_split 0 (self.buf_len - n);
+    self.buf_len <- self.buf_len - n
+  )
+
+exception Found_delim of int
+
+let rec read_chunk_ (self : st) buf i_buf len : chunk =
+  if self.eof then
+    Eof
+  else if self.buf_len < min_len_ self then (
+    (* try to refill buffer *)
+    let n =
+      Iostream.In.input self.ic self.buf_split self.buf_len
+        (Bytes.length self.buf_split - self.buf_len)
     in
-    { next }
-end
-
-let split s boundary =
-  let r = ref None in
-  let push v =
-    match !r with
-    | None -> r := Some v
-    | Some _ -> assert false
-  in
-  let pop () =
-    let res = !r in
-    r := None;
-    res
-  in
-  let go c0 =
-    let c =
-      match pop () with
-      | Some x -> x ^ c0
-      | None -> c0
-    in
-    let string_to_process =
-      match find_common_idx c boundary with
-      | None -> c
-      | Some idx ->
-        let prefix = String.sub c 0 idx in
-        let suffix = String.sub c idx (String.length c - idx) in
-        push suffix;
-        prefix
-    in
-    split_and_process_string ~boundary string_to_process
-  in
-  let initial = List.map go s in
-  let final =
-    Stream_.flatten
-    @@ Stream_.from (fun () ->
-           option_map (split_and_process_string ~boundary) @@ pop ())
-  in
-  Stream_.append initial final
-
-let until_next_delim s =
-  Stream_.from @@ fun () ->
-  let res = Stream_.get s in
-  match res with
-  | None | Some `Delim -> None
-  | Some (`Word w) -> Some w
-
-let join s =
-  Stream_.filter_map
-    (function
-      (* | `Delim -> Some (until_next_delim @@ Lwt_stream.clone s) *)
-      | `Delim -> Some (until_next_delim s)
-      | `Word _ -> None)
-    s
-
-let align stream boundary = join @@ split stream boundary
-
-type header = string * string
-
-let extract_boundary content_type =
-  Stringext.chop_prefix ~prefix:"multipart/form-data; boundary=" content_type
-
-let unquote s = Scanf.sscanf s "%S" @@ fun x -> x
-
-let parse_name s =
-  option_map unquote @@ Stringext.chop_prefix ~prefix:"form-data; name=" s
-
-let parse_header s =
-  match Stringext.cut ~on:": " s with
-  | Some (key, value) -> key, value
-  | None -> invalid_arg "parse_header"
-
-let non_empty st =
-  let%lwt r = Lwt_stream.to_list @@ Lwt_stream.clone st in
-  Lwt.return (String.concat "" r <> "")
-
-let get_headers : string Lwt_stream.t Lwt_stream.t -> header list Lwt.t =
- fun lines ->
-  let%lwt header_lines = Lwt_stream.get_while_s non_empty lines in
-  Lwt_list.map_s
-    (fun header_line_stream ->
-      let%lwt parts = Lwt_stream.to_list header_line_stream in
-      Lwt.return @@ parse_header @@ String.concat "" parts)
-    header_lines
-
-type stream_part = { headers: header list; body: string Lwt_stream.t }
-
-let parse_part chunk_stream =
-  let lines = align chunk_stream "\r\n" in
-  match%lwt get_headers lines with
-  | [] -> Lwt.return_none
-  | headers ->
-    let body = Lwt_stream.concat @@ Lwt_stream.clone lines in
-    Lwt.return_some { headers; body }
-
-let parse_stream ~stream ~content_type =
-  match extract_boundary content_type with
-  | None -> Lwt.fail_with "Cannot parse content-type"
-  | Some boundary ->
-    let actual_boundary = "--" ^ boundary in
-    Lwt.return
-    @@ Lwt_stream.filter_map_s parse_part
-    @@ align stream actual_boundary
-
-let s_part_body { body; _ } = body
-
-let s_part_name { headers; _ } =
-  match parse_name @@ List.assoc "Content-Disposition" headers with
-  | Some x -> x
-  | None -> invalid_arg "s_part_name"
-
-let parse_filename s =
-  let parts = split_on_string s ~pattern:"; " in
-  let f = function
-    | None -> None
-    | Some part ->
-      (match Stringext.cut part ~on:"=" with
-      | Some ("filename", quoted_string) -> Some (unquote quoted_string)
-      | _ -> None)
-  in
-  first_matching f parts
-
-let s_part_filename { headers; _ } =
-  parse_filename @@ List.assoc "Content-Disposition" headers
-
-type file = stream_part
-
-let file_stream = s_part_body
-let file_name = s_part_name
-let file_content_type { headers; _ } = List.assoc "Content-Type" headers
-
-let as_part part =
-  match s_part_filename part with
-  | Some _filename -> Lwt.return (`File part)
-  | None ->
-    let%lwt chunks = Lwt_stream.to_list part.body in
-    let body = String.concat "" chunks in
-    Lwt.return (`String body)
-
-let get_parts s =
-  let go part m =
-    let name = s_part_name part in
-    let%lwt parsed_part = as_part part in
-    Lwt.return @@ StringMap.add name parsed_part m
-  in
-  Lwt_stream.fold_s go s StringMap.empty
-
-let concat a b =
-  match a, b with
-  | _, "" -> a
-  | "", _ -> b
-  | _ -> a ^ b
-
-module Reader = struct
-  type t = { mutable buffer: string; source: string Lwt_stream.t }
-
-  let make stream = { buffer = ""; source = stream }
-  let unread r s = r.buffer <- concat s r.buffer
-
-  let empty r =
-    if r.buffer = "" then
-      Lwt_stream.is_empty r.source
-    else
-      Lwt.return false
-
-  let read_next r =
-    let%lwt next_chunk = Lwt_stream.next r.source in
-    r.buffer <- concat r.buffer next_chunk;
-    Lwt.return_unit
-
-  let read_chunk r =
-    try%lwt
-      let%lwt () =
-        if r.buffer = "" then
-          read_next r
-        else
-          Lwt.return_unit
-      in
-      let res = r.buffer in
-      r.buffer <- "";
-      Lwt.return (Some res)
-    with Lwt_stream.Empty -> Lwt.return None
-
-  let buffer_contains r s =
-    match Stringext.cut r.buffer ~on:s with
-    | Some _ -> true
-    | None -> false
-
-  let rec read_until r cond =
-    if cond () then
-      Lwt.return_unit
-    else (
-      let%lwt () = read_next r in
-      read_until r cond
+    Printf.eprintf "refill n=%d\n%!" n;
+    if n = 0 && self.buf_len = 0 then (
+      self.eof <- true;
+      Eof
+    ) else if n = 0 then (
+      let n_read = min len self.buf_len in
+      Bytes.blit self.buf_split 0 buf i_buf n_read;
+      shift_left_ self n_read;
+      Read n_read
+    ) else (
+      self.buf_len <- self.buf_len + n;
+      read_chunk_ self buf i_buf len
     )
+  ) else (
+    Printf.eprintf "normal path buflen=%d buf=%S\n%!" self.buf_len
+      (Bytes.sub_string self.buf_split 0 self.buf_len);
+    try
+      let i = ref 0 in
+      let end_pos = min len self.buf_len - 2 - String.length self.delim in
+      while !i <= end_pos do
+        Printf.eprintf "at %d\n%!" !i;
+        if
+          Bytes.unsafe_get self.buf_split !i = '-'
+          && Bytes.unsafe_get self.buf_split (!i + 1) = '-'
+          && Utils_.string_eq
+               ~a:(Bytes.unsafe_to_string self.buf_split)
+               ~a_start:(!i + 2) ~b:self.delim ~len:(String.length self.delim)
+        then
+          raise_notrace (Found_delim !i);
+        incr i
+      done;
+      let n_read = min !i len in
+      Bytes.blit self.buf_split 0 buf i_buf n_read;
+      shift_left_ self n_read;
+      Read n_read
+    with
+    | Found_delim 0 ->
+      Printf.eprintf "found delim at 0\n%!";
+      shift_left_ self (2 + String.length self.delim);
+      Delim
+    | Found_delim n ->
+      Printf.eprintf "found delim at %d\n%!" n;
+      let n_read = min n len in
+      Bytes.blit self.buf_split 0 buf i_buf n_read;
+      shift_left_ self n_read;
+      Read n_read
+  )
 
-  let read_line r =
-    let delim = "\r\n" in
-    let%lwt () = read_until r (fun () -> buffer_contains r delim) in
-    match Stringext.cut r.buffer ~on:delim with
-    | None -> assert false
-    | Some (line, next) ->
-      r.buffer <- next;
-      Lwt.return (line ^ delim)
+module Private_ = struct
+  type nonrec chunk = chunk = Delim | Eof | Read of int
+
+  let read_chunk_ = read_chunk_
 end
-
-let read_headers reader =
-  let rec go headers =
-    let%lwt line = Reader.read_line reader in
-    if line = "\r\n" then
-      Lwt.return headers
-    else (
-      let header = parse_header line in
-      go (header :: headers)
-    )
-  in
-  go []
-
-let rec compute_case reader boundary =
-  match%lwt Reader.read_chunk reader with
-  | None -> Lwt.return `Empty
-  | Some line ->
-    (match Stringext.cut line ~on:(boundary ^ "\r\n") with
-    | Some (pre, post) -> Lwt.return @@ `Boundary (pre, post)
-    | None ->
-      (match Stringext.cut line ~on:(boundary ^ "--\r\n") with
-      | Some (pre, post) -> Lwt.return @@ `Boundary (pre, post)
-      | None ->
-        (match find_common_idx line boundary with
-        | Some 0 ->
-          Reader.unread reader line;
-          let%lwt () = Reader.read_next reader in
-          compute_case reader boundary
-        | Some amb_idx ->
-          let unambiguous = String.sub line 0 amb_idx in
-          let ambiguous =
-            String.sub line amb_idx (String.length line - amb_idx)
-          in
-          Lwt.return @@ `May_end_with_boundary (unambiguous, ambiguous)
-        | None -> Lwt.return @@ `App_data line)))
-
-let iter_part reader boundary callback =
-  let fin = ref false in
-  let last () =
-    fin := true;
-    Lwt.return_unit
-  in
-  let handle ~send ~unread ~finish =
-    let%lwt () = callback send in
-    Reader.unread reader unread;
-    if finish then
-      last ()
-    else
-      Lwt.return_unit
-  in
-  while%lwt not !fin do
-    let%lwt res = compute_case reader boundary in
-    match res with
-    | `Empty -> last ()
-    | `Boundary (pre, post) -> handle ~send:pre ~unread:post ~finish:true
-    | `May_end_with_boundary (unambiguous, ambiguous) ->
-      handle ~send:unambiguous ~unread:ambiguous ~finish:false
-    | `App_data line -> callback line
-  done
-
-let read_file_part reader boundary callback = iter_part reader boundary callback
-
-let strip_crlf s =
-  if ends_with ~suffix:"\r\n" ~suffix_length:2 s then
-    String.sub s 0 (String.length s - 2)
-  else
-    s
-
-let read_string_part reader boundary =
-  let value = Buffer.create 0 in
-  let append_to_value line = Lwt.return (Buffer.add_string value line) in
-  let%lwt () = iter_part reader boundary append_to_value in
-  Lwt.return @@ strip_crlf (Buffer.contents value)
-
-let read_part reader boundary callback fields =
-  let%lwt headers = read_headers reader in
-  let content_disposition = List.assoc "Content-Disposition" headers in
-  let name =
-    match parse_name content_disposition with
-    | Some x -> x
-    | None -> invalid_arg "handle_multipart"
-  in
-  match parse_filename content_disposition with
-  | Some filename -> read_file_part reader boundary (callback ~name ~filename)
-  | None ->
-    let%lwt value = read_string_part reader boundary in
-    fields := (name, value) :: !fields;
-    Lwt.return_unit
-
-let handle_multipart reader boundary callback =
-  let fields = (ref [] : (string * string) list ref) in
-  let%lwt () =
-    let%lwt _dummyline = Reader.read_line reader in
-    let fin = ref false in
-    while%lwt not !fin do
-      if%lwt Reader.empty reader then
-        Lwt.return (fin := true)
-      else
-        read_part reader boundary callback fields
-    done
-  in
-  Lwt.return !fields
-
-let parse ~stream ~content_type ~callback =
-  let reader = Reader.make stream in
-  let boundary =
-    match extract_boundary content_type with
-    | Some s -> "--" ^ s
-    | None -> invalid_arg "iter_multipart"
-  in
-  handle_multipart reader boundary callback
diff --git a/src/multipart_form/tiny_httpd_multipart_form_data.mli b/src/multipart_form/tiny_httpd_multipart_form_data.mli
index 557324e7..985154ac 100644
--- a/src/multipart_form/tiny_httpd_multipart_form_data.mli
+++ b/src/multipart_form/tiny_httpd_multipart_form_data.mli
@@ -1,33 +1,11 @@
-val align : string Lwt_stream.t -> string -> string Lwt_stream.t Lwt_stream.t
-(**
-   Align a stream on a particular sequence and remove these boundaries.
- *)
+type st
 
-type stream_part
+val create : ?buf_size:int -> delim:string -> #Iostream.In.t -> st
 
-val s_part_name : stream_part -> string
-val s_part_body : stream_part -> string Lwt_stream.t
-val s_part_filename : stream_part -> string option
+(**/*)
+module Private_ : sig
+  type chunk = Delim | Eof | Read of int
 
-val parse_stream :
-  stream:string Lwt_stream.t ->
-  content_type:string ->
-  stream_part Lwt_stream.t Lwt.t
-
-type file
-
-val file_name : file -> string
-val file_content_type : file -> string
-val file_stream : file -> string Lwt_stream.t
-
-module StringMap : Map.S with type key = string
-
-val get_parts :
-  stream_part Lwt_stream.t ->
-  [ `String of string | `File of file ] StringMap.t Lwt.t
-
-val parse :
-  stream:string Lwt_stream.t ->
-  content_type:string ->
-  callback:(name:string -> filename:string -> string -> unit Lwt.t) ->
-  (string * string) list Lwt.t
+  val read_chunk_ : st -> bytes -> int -> int -> chunk
+end
+(**/*)
diff --git a/src/multipart_form/utils_.ml b/src/multipart_form/utils_.ml
index 4d1c5f56..6d56e698 100644
--- a/src/multipart_form/utils_.ml
+++ b/src/multipart_form/utils_.ml
@@ -1,13 +1,18 @@
-module StringMap = Map.Make (String)
+(* module StringMap = Map.Make (String) *)
 
-let string_eq ~a ~a_start ~b ~len =
-  let r = ref true in
-  for i = 0 to len - 1 do
-    let a_i = a_start + i in
-    let b_i = i in
-    if a.[a_i] <> b.[b_i] then r := false
-  done;
-  !r
+let string_eq ~a ~a_start ~b ~len : bool =
+  assert (len <= String.length b);
+  if String.length a >= a_start + len then (
+    try
+      for i = 0 to len - 1 do
+        let a_i = a_start + i in
+        if String.unsafe_get a a_i <> String.unsafe_get b i then
+          raise_notrace Exit
+      done;
+      true
+    with Exit -> false
+  ) else
+    false
 
 let ends_with ~suffix ~suffix_length s =
   let s_length = String.length s in
@@ -37,6 +42,7 @@ let find_common_idx a b =
   in
   go (String.length b)
 
+(*
 let[@inline] word = function
   | "" -> []
   | w -> [ Some w ]
@@ -60,3 +66,4 @@ let split_and_process_string ~boundary s =
     | Some w -> `Word w
   in
   List.map f @@ split_on_string ~pattern:boundary s
+  *)
diff --git a/tests/multipart_form/dune b/tests/multipart_form/dune
new file mode 100644
index 00000000..3590e207
--- /dev/null
+++ b/tests/multipart_form/dune
@@ -0,0 +1,4 @@
+
+(tests
+  (names t1)
+  (libraries tiny_httpd tiny_httpd.multipart-form-data))
diff --git a/tests/multipart_form/t1.expected b/tests/multipart_form/t1.expected
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/multipart_form/t1.ml b/tests/multipart_form/t1.ml
new file mode 100644
index 00000000..f68edec6
--- /dev/null
+++ b/tests/multipart_form/t1.ml
@@ -0,0 +1,45 @@
+module MFD = Tiny_httpd_multipart_form_data
+
+let pf = Printf.printf
+
+let read_stream (st : MFD.st) : _ list =
+  let l = ref [] in
+  let buf = Bytes.create 12 in
+  let buffer = Buffer.create 32 in
+  let rec loop () =
+    match MFD.Private_.read_chunk_ st buf 0 (Bytes.length buf) with
+    | Delim ->
+      if Buffer.length buffer > 0 then l := `Str (Buffer.contents buffer) :: !l;
+      Buffer.clear buffer;
+      l := `Delim :: !l;
+      loop ()
+    | Read n ->
+      Buffer.add_subbytes buffer buf 0 n;
+      loop ()
+    | Eof ->
+      if Buffer.length buffer > 0 then l := `Str (Buffer.contents buffer) :: !l;
+      List.rev !l
+  in
+  loop ()
+
+let test input_str =
+  let st =
+    MFD.create ~buf_size:16 ~delim:"YOLO" (Iostream.In.of_string input_str)
+  in
+  let chunks = read_stream st in
+  List.iter
+    (function
+      | `Delim -> pf "delim\n"
+      | `Str s -> pf "chunk %S\n" s)
+    chunks;
+  ()
+
+let () =
+  pf "T1\n";
+  test
+    {|hello--YOLO
+  world
+    what is the meaning of--YOLOthis??--YOLOok ok ok--YOLO|};
+  pf "T2\n";
+  test "--YOLO--YOLOah bon--YOLOaight--YOLO--YOLO";
+  ()