Method utf16_to_utf8

extlibs/fmt/src/os.cc:76–81

#ifdef _WIN32
internal::utf16_to_utf8::utf16_to_utf8(wstring_view s) {
  if (int error_code = convert(s)) {
    FMT_THROW(windows_error(error_code,
                            "cannot convert string from UTF-16 to UTF-8"));
  }
}

int internal::utf16_to_utf8::convert(wstring_view s) {
  if (s.size() > INT_MAX) return ERROR_INVALID_PARAMETER;