Added path_to_plain_ascii for use by driver-ssl

luprex/core/cpp/driver-linux.cpp

@@ -32,6 +32,16 @@ const int INVALID_SOCKET = -1;
 
 struct termios orig_termios;
 
+// OpenSSL requires plain ascii pathnames.  Returns empty string
+// if the path cannot be converted to plain ascii.
+std::string path_to_plain_ascii(const std::filesystem::path &path) {
+	std::string s = path.native();
+	for (char c : s) {
+		if ((c < 1) || (c > 127)) return "";
+	}
+	return s;
+}
+
 std::string strerror_str(int err) {
     char errbuf[256];
     return strerror_r(err, errbuf, 256);