incremental
diff --git a/include/base64.hpp b/include/base64.hpp
new file mode 100644
index 0000000..f5ff338
--- /dev/null
+++ b/include/base64.hpp
@@ -0,0 +1,9 @@
+#include <gsl/string_span>
+#include <string>
+
+namespace base64 {
+
+    bool base64_encode(const gsl::cstring_span<> &input, std::string &output);
+    bool base64_decode(const gsl::cstring_span<> &input, std::string &output);
+
+}
\ No newline at end of file