string: add string_is_utf8() helper

Ticket #27373.

1 files changed, 48 insertions, 0 deletions

diff --git a/src/test/test_util.c b/src/test/test_util.c
index 6cbd504e34..bdf8b5dafa 100644
--- a/src/test/test_util.c
+++ b/src/test/test_util.c
@@ -4012,6 +4012,53 @@ test_util_string_is_C_identifier(void *ptr)
 }
 
 static void
+test_util_string_is_utf8(void *ptr)
+{
+  (void)ptr;
+
+  tt_int_op(1, OP_EQ, string_is_utf8(NULL, 0));
+  tt_int_op(1, OP_EQ, string_is_utf8("", 1));
+  tt_int_op(1, OP_EQ, string_is_utf8("\uFEFF", 3));
+  tt_int_op(1, OP_EQ, string_is_utf8("\uFFFE", 3));
+  tt_int_op(1, OP_EQ, string_is_utf8("ascii\x7f\n", 7));
+  tt_int_op(1, OP_EQ, string_is_utf8("Risqu\u00e9=1", 9));
+
+  // Validate exactly 'len' bytes.
+  tt_int_op(0, OP_EQ, string_is_utf8("\0\x80", 2));
+  tt_int_op(0, OP_EQ, string_is_utf8("Risqu\u00e9=1", 6));
+
+  // Reject sequences with missing bytes.
+  tt_int_op(0, OP_EQ, string_is_utf8("\x80", 1));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xc2", 1));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xc2 ", 2));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xe1\x80", 2));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xe1\x80 ", 3));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xf1\x80\x80", 3));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xf1\x80\x80 ", 4));
+
+  // Reject encodings that are overly long.
+  tt_int_op(0, OP_EQ, string_is_utf8("\xc1\xbf", 2));
+  tt_int_op(1, OP_EQ, string_is_utf8("\xc2\x80", 2));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xe0\x9f\xbf", 3));
+  tt_int_op(1, OP_EQ, string_is_utf8("\xe0\xa0\x80", 3));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xf0\x8f\xbf\xbf", 4));
+  tt_int_op(1, OP_EQ, string_is_utf8("\xf0\x90\x80\x80", 4));
+
+  // Reject UTF-16 surrogate halves.
+  tt_int_op(1, OP_EQ, string_is_utf8("\xed\x9f\xbf", 3));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xed\xa0\x80", 3));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xed\xbf\xbf", 3));
+  tt_int_op(1, OP_EQ, string_is_utf8("\xee\x80\x80", 3));
+
+  // The maximum legal codepoint, 10FFFF.
+  tt_int_op(1, OP_EQ, string_is_utf8("\xf4\x8f\xbf\xbf", 4));
+  tt_int_op(0, OP_EQ, string_is_utf8("\xf4\x90\x80\x80", 4));
+
+ done:
+  ;
+}
+
+static void
 test_util_asprintf(void *ptr)
 {
 #define LOREMIPSUM                                              \
@@ -6398,6 +6445,7 @@ struct testcase_t util_tests[] = {
   UTIL_TEST(clamp_double_to_int64, 0),
   UTIL_TEST(find_str_at_start_of_line, 0),
   UTIL_TEST(string_is_C_identifier, 0),
+  UTIL_TEST(string_is_utf8, 0),
   UTIL_TEST(asprintf, 0),
   UTIL_TEST(listdir, 0),
   UTIL_TEST(parent_dir, 0),