From a5a06f0159b29d2f8aecb83acacb423f96fc9121 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Mon, 2 Dec 2024 14:45:26 -0500
Subject: [PATCH] feat multipart: add helper to parse boundary

---
 .../tiny_httpd_multipart_form_data.ml         | 24 ++++++++
 .../tiny_httpd_multipart_form_data.mli        |  3 +
 src/multipart_form/utils_.ml                  | 59 ++-----------------
 3 files changed, 31 insertions(+), 55 deletions(-)

diff --git a/src/multipart_form/tiny_httpd_multipart_form_data.ml b/src/multipart_form/tiny_httpd_multipart_form_data.ml
index 6529f0e6..315b35e0 100644
--- a/src/multipart_form/tiny_httpd_multipart_form_data.ml
+++ b/src/multipart_form/tiny_httpd_multipart_form_data.ml
@@ -204,6 +204,30 @@ and parse_headers_rec (self : st) acc : Headers.t =
       )
   )
 
+let parse_content_type (hs : Tiny_httpd.Headers.t) : _ option =
+  match Tiny_httpd.Headers.get "content-type" hs with
+  | None -> None
+  | Some s ->
+    (match String.split_on_char ';' s with
+    | "multipart/form-data" :: tl ->
+      let boundary = ref None in
+      List.iter
+        (fun s ->
+          match Utils_.split1_on ~c:'=' @@ String.trim s with
+          | Some ("boundary", "") -> ()
+          | Some ("boundary", s) ->
+            let s =
+              if s.[0] = '"' && s.[String.length s - 1] = '"' then
+                String.sub s 1 (String.length s - 2)
+              else
+                s
+            in
+            boundary := Some (`boundary s)
+          | _ -> ())
+        tl;
+      !boundary
+    | _ -> None)
+
 module Private_ = struct
   type nonrec chunk = chunk = Delim | Eof | Read of int
 
diff --git a/src/multipart_form/tiny_httpd_multipart_form_data.mli b/src/multipart_form/tiny_httpd_multipart_form_data.mli
index 009dbc47..a1747e5d 100644
--- a/src/multipart_form/tiny_httpd_multipart_form_data.mli
+++ b/src/multipart_form/tiny_httpd_multipart_form_data.mli
@@ -5,6 +5,9 @@ type st
 val create :
   ?buf_size:int -> ?out_buf_size:int -> boundary:string -> #Iostream.In.t -> st
 
+val parse_content_type : Tiny_httpd.Headers.t -> [ `boundary of string ] option
+(** Parse headers for [content-type: multipart/form-data; boundary=…] *)
+
 type slice = Iostream.Slice.t
 type event = Part of Tiny_httpd.Headers.t | Read of slice | End_of_input
 
diff --git a/src/multipart_form/utils_.ml b/src/multipart_form/utils_.ml
index 6d56e698..a1f993ce 100644
--- a/src/multipart_form/utils_.ml
+++ b/src/multipart_form/utils_.ml
@@ -1,5 +1,3 @@
-(* module StringMap = Map.Make (String) *)
-
 let string_eq ~a ~a_start ~b ~len : bool =
   assert (len <= String.length b);
   if String.length a >= a_start + len then (
@@ -14,56 +12,7 @@ let string_eq ~a ~a_start ~b ~len : bool =
   ) else
     false
 
-let ends_with ~suffix ~suffix_length s =
-  let s_length = String.length s in
-  s_length >= suffix_length
-  && string_eq ~a:s ~a_start:(s_length - suffix_length) ~b:suffix
-       ~len:suffix_length
-
-let rec first_matching p = function
-  | [] -> None
-  | x :: xs ->
-    (match p x with
-    | Some y -> Some y
-    | None -> first_matching p xs)
-
-let[@inline] option_map f = function
-  | None -> None
-  | Some x -> Some (f x)
-
-let find_common_idx a b =
-  let rec go i =
-    if i <= 0 then
-      None
-    else if ends_with ~suffix:b ~suffix_length:i a then
-      Some (String.length a - i)
-    else
-      go (i - 1)
-  in
-  go (String.length b)
-
-(*
-let[@inline] word = function
-  | "" -> []
-  | w -> [ Some w ]
-
-let split_on_string ~pattern s =
-  let pattern_length = String.length pattern in
-  let rec go start acc =
-    match Stringext.find_from ~start s ~pattern with
-    | Some match_start ->
-      let before = String.sub s start (match_start - start) in
-      let new_acc = (None :: word before) @ acc in
-      let new_start = match_start + pattern_length in
-      go new_start new_acc
-    | None -> word (Stringext.string_after s start) @ acc
-  in
-  List.rev (go 0 [])
-
-let split_and_process_string ~boundary s =
-  let f = function
-    | None -> `Delim
-    | Some w -> `Word w
-  in
-  List.map f @@ split_on_string ~pattern:boundary s
-  *)
+let split1_on ~c s =
+  match String.index s c with
+  | exception Not_found -> None
+  | i -> Some (String.sub s 0 i, String.sub s (i + 1) (String.length s - i - 1))