xo-alloc2: still more header org-streamlining

xo-alloc2/include/xo/alloc2/gcobject/AGCObject.hpp

@@ -0,0 +1,53 @@
+/** @file AGCObject.hpp
+ *
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#pragma once
+
+#include "Allocator.hpp"
+#include "xo/facet/facet_implementation.hpp"
+#include "xo/facet/typeseq.hpp"
+#include "xo/facet/obj.hpp"   // for obj<AAllocator> in shallow_copy
+#include <cstdint>
+#include <cstddef>
+
+namespace xo {
+    namespace mm {
+        using Copaque = const void *;
+        using Opaque = void *;
+
+        /** @class AObject
+         *  @brief Abstract facet for collector-eligible data
+         *
+         *  Data that supports AGCObject can have memory managed
+         *  by ACollector
+         **/
+        struct AGCObject {
+            using size_type = std::size_t;
+
+            /** RTTI: unique id# for actual runtime data representation **/
+            virtual int32_t _typeseq() const noexcept = 0;
+
+            virtual size_type shallow_size(Copaque d) const noexcept = 0;
+            virtual Opaque * shallow_copy(Copaque d,
+                                          obj<AAllocator> mm) const noexcept = 0;
+            virtual size_type forward_children(Opaque d) const noexcept = 0;
+        };
+
+        // implementation IGCObject_DRepr of AGCObject for state DRepr
+        // should provide a specialization:
+        //
+        //   template <>
+        //   struct xo::facet::FacetImplementation<AGCObjectx, DRepr> {
+        //       using ImplType = IGCObject_DRepr;
+        //   };
+        //
+        //   then IGCObject_ImplType<DRepr> --> IGCObject_DRepr
+        //
+        template <typename DRepr>
+        using IGCObject_ImplType = xo::facet::FacetImplType<AGCObject, DRepr>;
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end AGCObject.hpp */