Provider type abstraction, partially completed.

include/wsrep/client_id.hpp

@@ -0,0 +1,28 @@
+//
+// Copyright (C) 2018 Codership Oy <info@codership.com>
+//
+
+#ifndef WSREP_CLIENT_ID_HPP
+#define WSREP_CLIENT_ID_HPP
+
+namespace wsrep
+{
+    class client_id
+    {
+    public:
+        typedef unsigned long long type;
+        client_id()
+            : id_(-1)
+        { }
+        template <typename I>
+        client_id(I id)
+            : id_(static_cast<type>(id))
+        { }
+        type get() const { return id_; }
+        static type invalid() { return -1; }
+    private:
+        type id_;
+    };
+}
+
+#endif // WSREP_CLIENT_ID_HPP