Add 'xo-reflect/' from commit '5dce303fe1'

git-subtree-dir: xo-reflect
git-subtree-mainline: 8111f3846c
git-subtree-split: 5dce303fe1

xo-reflect/include/xo/reflect/pointer/PointerTdx.hpp

@@ -0,0 +1,85 @@
+/* file PointerTdx.hpp
+ *
+ * author: Roland Conybeare, Sep 2022
+ */
+
+#pragma once
+
+#include "xo/reflect/TypeDescrExtra.hpp"
+#include "xo/reflect/EstablishTypeDescr.hpp"
+#include "xo/indentlog/scope.hpp"
+
+namespace xo {
+    namespace reflect {
+        /* Extra type-associated information for a pointer-like type
+         *
+         * Treat a pointer as a container that has 0 or 1 children;
+         * - 0 children if null
+         * - 1 child otherwise
+         */
+        class PointerTdx : public TypeDescrExtra {
+        public:
+            // ----- Inherited from TypeDescrExtra -----
+
+            virtual Metatype metatype() const override { return Metatype::mt_pointer; }
+            virtual uint32_t n_child(void * object) const override = 0;
+
+            /* number of children unknown at compile time.
+             * null-pointer -> 0, non-null pointer -> 1
+             */
+            virtual uint32_t n_child_fixed() const override { return 0; /*unknown*/ }
+            virtual TaggedPtr child_tp(uint32_t i, void * object) const override = 0;
+            /* (forbidden) */
+            virtual std::string const & struct_member_name(uint32_t i) const override;
+        }; /*PointerTdx*/
+
+        // ----- RefPointerTdx -----
+
+        /* Pointer = xo::ref::intrusive_ptr<T> for some T */
+        template<typename Pointer>
+        class RefPointerTdx : public PointerTdx {
+        public:
+            using target_t = Pointer;
+
+            static std::unique_ptr<RefPointerTdx> make() {
+                return std::unique_ptr<RefPointerTdx>(new RefPointerTdx());
+            } /*make*/
+
+            virtual uint32_t n_child(void * object) const override {
+                /* e.g:
+                 *   target_t = ref::rp<filter::KalmanFilterState>
+                 */
+                target_t * ptr = reinterpret_cast<target_t *>(object);
+
+                if (*ptr)
+                    return 1;
+                else
+                    return 0;
+            } /*n_child*/
+
+            virtual TypeDescrBase * fixed_child_td(uint32_t /*i*/) const override {
+                return EstablishTypeDescr::establish<typename Pointer::element_type>();
+            }
+
+            virtual TaggedPtr child_tp(uint32_t i, void * object) const override {
+                using xo::tostr;
+                using xo::xtag;
+
+                target_t * ptr = reinterpret_cast<target_t *>(object);
+
+                if (i > 0) {
+                    throw std::runtime_error(tostr("RefPointerTdx<T>::child_tp"
+                                                   ": attempt to fetch child #i from a ref::rp<T>",
+                                                   xtag("T", type_name<target_t>()),
+                                                   xtag("i", i),
+                                                   xtag("n", this->n_child(object))));
+                }
+
+                return establish_most_derived_tp(ptr->get());
+            } /*child_tp*/
+        }; /*RefPointerTdx*/
+
+    } /*namespace reflect*/
+} /*namespace xo*/
+
+/* end PointerTdx.hpp */