Tests: Add some test for utf8/utf16 conversion

Author: hhugo

lib/tests/dune.inc

@@ -99,6 +99,16 @@
  (preprocess
   (pps ppx_js_internal ppx_expect)))
 
+(library
+ ;; lib/tests/test_string.ml
+ (name test_string_75)
+ (enabled_if true)
+ (modules test_string)
+ (libraries js_of_ocaml unix)
+ (inline_tests (modes js wasm))
+ (preprocess
+  (pps ppx_js_internal ppx_expect)))
+
 (library
  ;; lib/tests/test_sys.ml
  (name test_sys_75)

lib/tests/test_string.ml

@@ -0,0 +1,74 @@
+(* Js_of_ocaml tests
+ * http://www.ocsigen.org/js_of_ocaml/
+ * Copyright (C) 2025 Hugo Heuzard
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *)
+
+open Js_of_ocaml
+
+let%expect_test "test utf8-utf16 conversions" =
+  let min = Uchar.to_int Uchar.min in
+  let max = Uchar.to_int Uchar.max in
+  let utf8 = Buffer.create (max * 4) in
+  let utf16 = Buffer.create (max * 4) in
+  let l = ref [] in
+  for i = max downto min do
+    if Uchar.is_valid i then l := Uchar.of_int i :: !l
+  done;
+  List.iter
+    (fun u ->
+      Buffer.add_utf_16be_uchar utf16 u;
+      Buffer.add_utf_8_uchar utf8 u)
+    !l;
+  let utf8 = Buffer.contents utf8 in
+  let utf16 = Buffer.contents utf16 in
+
+  let utf16' = Js.string utf8 in
+  let rec loop i =
+    if i / 2 >= utf16'##.length
+    then assert (i = String.length utf16)
+    else
+      let u_js =
+        utf16'##codePointAt (i / 2)
+        |> Js.Optdef.to_option
+        |> Option.get
+        |> Js.to_float
+        |> int_of_float
+      in
+      let u_ml, len =
+        let d = String.get_utf_16be_uchar utf16 i in
+        assert (Uchar.utf_decode_is_valid d);
+        let len = Uchar.utf_decode_length d in
+        Uchar.to_int (Uchar.utf_decode_uchar d), len
+      in
+      if u_js = u_ml
+      then loop (i + len)
+      else (
+        Printf.eprintf "%x <> %x\n" u_js u_ml;
+        Printf.eprintf "string differ at %x\n" i;
+        assert false)
+  in
+  loop 0;
+  let utf8' = Js.to_string utf16' in
+  for i = 0 to String.length utf8 - 1 do
+    if Char.equal (String.get utf8 i) (String.get utf8' i)
+    then ()
+    else (
+      Printf.eprintf "%C <> %C\n" (String.get utf8 i) (String.get utf8' i);
+      Printf.eprintf "string differ at %d\n" i;
+      ())
+  done;
+  [%expect {||}]