fix: preserve UTF-8 advert names

test/test_utf8_helpers/test_utf8_helpers.cpp

@@ -0,0 +1,38 @@
+#include <gtest/gtest.h>
+
+#include <helpers/UTF8Helpers.h>
+
+TEST(UTF8Helpers, KeepsCompleteNameWithinLimit) {
+  const char* name = "Example RPT 🔋🇵🇱";
+
+  EXPECT_EQ(24u, mesh::validUtf8PrefixLength(name, 24));
+}
+
+TEST(UTF8Helpers, StopsBeforeCodePointCrossingLimit) {
+  const char* name = "Example RPT 🔋🇵🇱";
+
+  EXPECT_EQ(20u, mesh::validUtf8PrefixLength(name, 23));
+}
+
+TEST(UTF8Helpers, RejectsMalformedAndTruncatedSequences) {
+  const char overlong[] = {'A', static_cast<char>(0xC0), static_cast<char>(0xAF), 0};
+  const char surrogate[] = {'A', static_cast<char>(0xED), static_cast<char>(0xA0), static_cast<char>(0x80), 0};
+  const char out_of_range[] = {'A', static_cast<char>(0xF4), static_cast<char>(0x90), static_cast<char>(0x80), static_cast<char>(0x80), 0};
+  const char truncated[] = {'A', static_cast<char>(0xF0), static_cast<char>(0x9F), 0};
+
+  EXPECT_EQ(1u, mesh::validUtf8PrefixLength(overlong, sizeof(overlong)));
+  EXPECT_EQ(1u, mesh::validUtf8PrefixLength(surrogate, sizeof(surrogate)));
+  EXPECT_EQ(1u, mesh::validUtf8PrefixLength(out_of_range, sizeof(out_of_range)));
+  EXPECT_EQ(1u, mesh::validUtf8PrefixLength(truncated, sizeof(truncated)));
+}
+
+TEST(UTF8Helpers, RejectsUnexpectedContinuationByte) {
+  const char invalid[] = {'A', static_cast<char>(0x80), 'B', 0};
+
+  EXPECT_EQ(1u, mesh::validUtf8PrefixLength(invalid, sizeof(invalid)));
+}
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}