Test and fix Bytes.is_valid_utf_8.

stdlib/bytes.ml

@@ -674,48 +674,55 @@ let is_valid_utf_8 b =
     | '\x00' .. '\x7F' -> loop max b (i + 1)
     | '\xC2' .. '\xDF' ->
         let last = i + 1 in
-        last > max
+        if last > max
         || not_in_x80_to_xBF (get b last)
-        || loop max b (last + 1)
+        then false
+        else loop max b (last + 1)
     | '\xE0' ->
         let last = i + 2 in
-        last > max
+        if last > max
         || not_in_xA0_to_xBF (get b (i + 1))
         || not_in_x80_to_xBF (get b last)
-        || loop max b (last + 1)
+        then false
+        else loop max b (last + 1)
     | '\xE1' .. '\xEC' | '\xEE' .. '\xEF' ->
         let last = i + 2 in
-        last > max
+        if last > max
         || not_in_x80_to_xBF (get b (i + 1))
         || not_in_x80_to_xBF (get b last)
-        || loop max b (last + 1)
+        then false
+        else loop max b (last + 1)
     | '\xED' ->
         let last = i + 2 in
-        last > max
+        if last > max
         || not_in_x80_to_x9F (get b (i + 1))
         || not_in_x80_to_xBF (get b last)
-        || loop max b (last + 1)
+        then false
+        else loop max b (last + 1)
     | '\xF0' ->
         let last = i + 3 in
-        last > max
+        if last > max
         || not_in_x90_to_xBF (get b (i + 1))
         || not_in_x80_to_xBF (get b (i + 2))
         || not_in_x80_to_xBF (get b last)
-        || loop max b (last + 1)
+        then false
+        else loop max b (last + 1)
     | '\xF1' .. '\xF3' ->
         let last = i + 3 in
-        last > max
+        if last > max
         || not_in_x80_to_xBF (get b (i + 1))
         || not_in_x80_to_xBF (get b (i + 2))
         || not_in_x80_to_xBF (get b last)
-        || loop max b (last + 1)
+        then false
+        else loop max b (last + 1)
     | '\xF4' ->
         let last = i + 3 in
-        last > max
+        if last > max
         || not_in_x80_to_x8F (get b (i + 1))
         || not_in_x80_to_xBF (get b (i + 2))
         || not_in_x80_to_xBF (get b last)
-        || loop max b (last + 1)
+        then false
+        else loop max b (last + 1)
     | _ -> false
   in
   loop (length b - 1) b 0

testsuite/tests/lib-bytes-utf/test.ml

@@ -119,6 +119,13 @@ let () =
   assert (Bytes.set_utf_16le_uchar b 0 Uchar.max = 0 && Bytes.get b 0 = '\xab');
   ()
 
+let () =
+  (* Test bug found during review *)
+  let b = Bytes.create 2 in
+  let () = Bytes.set_uint8 b 0 0xC3 in
+  let () = Bytes.set_uint8 b 1 0x00 in
+  assert (not (Bytes.is_valid_utf_8 b))
+
 let () =
   (* Test used bytes and replacement according to WHATWG recommendation.
      This is just a recommendation.
@@ -215,17 +222,20 @@ let test_invalid_decodes () =
     in
     fold_uchars add (Sset.empty, Sset.empty, Sset.empty)
   in
-  let test_seqs utf utf_encs get_utf_char =
+  let test_seqs utf utf_encs get_utf_char is_valid_utf =
     let test seq =
       let dec = get_utf_char seq 0 in
       let valid = Uchar.utf_decode_is_valid dec in
+      let is_valid = is_valid_utf seq in
       let is_enc = Sset.mem (Bytes.unsafe_to_string seq) utf_encs in
-      if not ((valid && is_enc) || (not valid && not is_enc)) then begin
+      if not ((valid && is_enc) || (not valid && not is_enc)) ||
+         not ((is_valid && is_enc) || (not is_valid && not is_enc))
+      then begin
         for i = 0 to Bytes.length seq - 1 do
           Printf.printf "%02X " (Bytes.get_uint8 seq i);
         done;
-        Printf.printf "valid: %b is_encoding: %b decode: U+%04X\n" valid is_enc
-          (Uchar.to_int (Uchar.utf_decode_uchar dec));
+        Printf.printf "valid: %b is_encoding: %b decode: U+%04X\n is_valid:%b"
+          valid is_enc (Uchar.to_int (Uchar.utf_decode_uchar dec)) is_valid;
         assert false
       end;
       valid
@@ -257,7 +267,9 @@ let test_invalid_decodes () =
       end
     done
   in
-  test_seqs "UTF-8" utf_8_encs Bytes.get_utf_8_uchar;
-  test_seqs "UTF-16BE" utf_16be_encs Bytes.get_utf_16be_uchar;
-  test_seqs "UTF-16LE" utf_16le_encs Bytes.get_utf_16le_uchar;
+  test_seqs "UTF-8" utf_8_encs Bytes.get_utf_8_uchar Bytes.is_valid_utf_8;
+  test_seqs "UTF-16BE"
+    utf_16be_encs Bytes.get_utf_16be_uchar Bytes.is_valid_utf_16be;
+  test_seqs "UTF-16LE" utf_16le_encs Bytes.get_utf_16le_uchar
+    Bytes.is_valid_utf_16le;
   ()