initial implementation

src/callback/CMakeLists.txt

@@ -0,0 +1,14 @@
+# callback/CMakeLists.txt
+
+set(SELF_LIB callback)
+set(SELF_SRCS CallbackSet.cpp)
+
+# reminder: can't be header-only library,  because depends on non-header-only refcnt
+xo_add_shared_library(${SELF_LIB} ${PROJECT_VERSION} 1 ${SELF_SRCS})
+
+# ----------------------------------------------------------------
+# external dependencies:
+
+xo_dependency(${SELF_LIB} refcnt)
+
+# end CMakeLists.txt

src/callback/CallbackSet.cpp

@@ -0,0 +1,22 @@
+/* file CallbackSet.cpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#include "CallbackSet.hpp"
+
+namespace xo {
+    namespace fn {
+        CallbackId
+        CallbackId::generate()
+        {
+            static CallbackId s_last_id;
+
+            s_last_id = CallbackId(s_last_id.id() + 1);
+
+            return s_last_id;
+        } /*generate*/
+    } /*namespace fn*/
+} /*namespace xo*/
+
+/* end CallbackSet.cpp */