new unmap uvalue operator

headers/meta.hpp/meta_detail/value_traits/unmap_traits.hpp

@@ -0,0 +1,45 @@
+/*******************************************************************************
+ * This file is part of the "https://github.com/blackmatov/meta.hpp"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2021-2023, by Matvey Cherevko (blackmatov@gmail.com)
+ ******************************************************************************/
+
+#pragma once
+
+#include "../../meta_base.hpp"
+#include "../../meta_uvalue.hpp"
+
+namespace meta_hpp::detail
+{
+    template < typename T >
+    struct unmap_traits;
+
+    template < typename T >
+    concept has_unmap_traits = requires(const T& v) {
+        { unmap_traits<T>{}(v) } -> std::convertible_to<uvalue>;
+    };
+}
+
+namespace meta_hpp::detail
+{
+    template < typename T >
+    struct unmap_traits<std::shared_ptr<T>> {
+        uvalue operator()(const std::shared_ptr<T>& v) const {
+            return uvalue{v.get()};
+        }
+    };
+
+    template < typename T, typename D >
+    struct unmap_traits<std::unique_ptr<T, D>> {
+        uvalue operator()(const std::unique_ptr<T, D>& v) const {
+            return uvalue{v.get()};
+        }
+    };
+
+    template < typename T >
+    struct unmap_traits<std::reference_wrapper<T>> {
+        uvalue operator()(const std::reference_wrapper<T>& v) const {
+            return uvalue{std::addressof(v.get())};
+        }
+    };
+}

headers/meta.hpp/meta_uvalue.hpp

@@ -88,6 +88,9 @@ namespace meta_hpp
         [[nodiscard]] uvalue operator[](std::size_t index) const;
         [[nodiscard]] bool has_index_op() const noexcept;
 
+        [[nodiscard]] uvalue unmap() const;
+        [[nodiscard]] bool has_unmap_op() const noexcept;
+
         template < typename T >
         [[nodiscard]] T get_as() &&;
 

headers/meta.hpp/meta_uvalue/uvalue.hpp

@@ -12,6 +12,7 @@
 
 #include "../meta_detail/value_traits/deref_traits.hpp"
 #include "../meta_detail/value_traits/index_traits.hpp"
+#include "../meta_detail/value_traits/unmap_traits.hpp"
 
 #include "../meta_detail/value_utilities/utraits.hpp"
 
@@ -29,6 +30,7 @@ namespace meta_hpp
 
         uvalue (*const deref)(const storage_u& from);
         uvalue (*const index)(const storage_u& from, std::size_t);
+        uvalue (*const unmap)(const storage_u& from);
 
         template < typename T >
         static T* buffer_cast(buffer_t& buffer) noexcept {
@@ -180,7 +182,6 @@ namespace meta_hpp
                     self.vtable_ = nullptr;
                 },
 
-
                 .deref = [](){
                     if constexpr ( detail::has_deref_traits<Tp> ) {
                         return +[](const storage_u& from) -> uvalue {
@@ -200,6 +201,16 @@ namespace meta_hpp
                         return nullptr;
                     }
                 }(),
+
+                .unmap = [](){
+                    if constexpr ( detail::has_unmap_traits<Tp> ) {
+                        return +[](const storage_u& from) -> uvalue {
+                            return detail::unmap_traits<Tp>{}(*storage_cast<Tp>(from));
+                        };
+                    } else {
+                        return nullptr;
+                    }
+                }(),
             };
 
             return &table;
@@ -338,6 +349,14 @@ namespace meta_hpp
         return vtable_ != nullptr && vtable_->index != nullptr;
     }
 
+    inline uvalue uvalue::unmap() const {
+        return has_unmap_op() ? vtable_->unmap(storage_) : uvalue{};
+    }
+
+    inline bool uvalue::has_unmap_op() const noexcept {
+        return vtable_ != nullptr && vtable_->unmap != nullptr;
+    }
+
     template < typename T >
     T uvalue::get_as() && {
         static_assert(std::is_same_v<T, std::decay_t<T>>);