From b65b34a976b586f4e407f7a89567163c85b94aa6 Mon Sep 17 00:00:00 2001
From: Stanislaw Halik <sthalik@misaki.pl>
Date: Fri, 18 Nov 2022 10:42:26 +0100
Subject: split erased accessor from main header

---
 entity/accessor.hpp | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 entity/accessor.hpp

(limited to 'entity/accessor.hpp')

diff --git a/entity/accessor.hpp b/entity/accessor.hpp
new file mode 100644
index 00000000..9b836420
--- /dev/null
+++ b/entity/accessor.hpp
@@ -0,0 +1,112 @@
+#pragma once
+#include "util.hpp"
+#include <type_traits>
+#include <Corrade/Containers/StringView.h>
+
+namespace floormat::entities {
+
+struct erased_accessor final {
+    using erased_reader_t = void;
+    using erased_writer_t = void;
+    using Object = void;
+    using Value = void;
+
+    const erased_reader_t* reader;
+    const erased_writer_t* writer;
+    StringView object_name, field_type_name;
+    void(*read_fun)(const Object*, const erased_reader_t*, Value*);
+    void(*write_fun)(Object*, const erased_writer_t*, Value*);
+
+    constexpr erased_accessor(const erased_accessor&) = default;
+    constexpr erased_accessor(erased_reader_t* reader, erased_writer_t * writer,
+                               StringView object_name, StringView field_type_name,
+                               void(*read_fun)(const Object*, const erased_reader_t*, Value*),
+                               void(*write_fun)(Object*, const erased_writer_t*, Value*)) :
+        reader{reader}, writer{writer},
+        object_name{object_name}, field_type_name{field_type_name},
+        read_fun{read_fun}, write_fun{write_fun}
+    {}
+
+    template<typename T, typename FieldType>
+    static constexpr bool check_name_static();
+
+    template<typename T, typename FieldType>
+    constexpr bool check_name() const noexcept;
+
+    template<typename Obj, typename FieldType> constexpr void assert_name() const noexcept;
+    template<typename Obj, typename FieldType> void read_unchecked(const Obj& x, FieldType& value) const noexcept;
+    template<typename Obj, typename FieldType> requires std::is_default_constructible_v<FieldType> FieldType read_unchecked(const Obj& x) const noexcept;
+    template<typename Obj, typename FieldType> void write_unchecked(Obj& x, move_qualified<FieldType> value) const noexcept;
+    template<typename Obj, typename FieldType> requires std::is_default_constructible_v<FieldType> FieldType read(const Obj& x) const noexcept;
+    template<typename Obj, typename FieldType> void read(const Obj& x, FieldType& value) const noexcept;
+    template<typename Obj, typename FieldType> void write(Obj& x, move_qualified<FieldType> value) const noexcept;
+};
+
+template<typename T, typename FieldType>
+constexpr bool erased_accessor::check_name_static()
+{
+    return !std::is_pointer_v<T> && !std::is_reference_v<T> &&
+           !std::is_pointer_v<FieldType> && !std::is_reference_v<T>;
+}
+
+template<typename T, typename FieldType>
+constexpr bool erased_accessor::check_name() const noexcept
+{
+    static_assert(check_name_static<T, FieldType>());
+    constexpr auto obj = name_of<T>, field = name_of<FieldType>;
+    return (obj.data() == object_name.data() && field.data() == field_type_name.data()) ||
+           obj == object_name && field == field_type_name;
+}
+
+template<typename Obj, typename FieldType>
+constexpr void erased_accessor::assert_name() const noexcept
+{
+    fm_assert(check_name<Obj, FieldType>());
+}
+
+template<typename Obj, typename FieldType>
+void erased_accessor::read_unchecked(const Obj& x, FieldType& value) const noexcept
+{
+    static_assert(check_name_static<Obj, FieldType>());
+    read_fun(&x, reader, &value);
+}
+
+template<typename Obj, typename FieldType>
+requires std::is_default_constructible_v<FieldType>
+FieldType erased_accessor::read_unchecked(const Obj& x) const noexcept
+{
+    static_assert(check_name_static<Obj, FieldType>());
+    FieldType value;
+    read_unchecked(x, value);
+    return value;
+}
+
+template<typename Obj, typename FieldType>
+void erased_accessor::write_unchecked(Obj& x, move_qualified<FieldType> value) const noexcept
+{
+    static_assert(check_name_static<Obj, FieldType>());
+    write_fun(&x, writer, &value);
+}
+
+template<typename Obj, typename FieldType>
+requires std::is_default_constructible_v<FieldType>
+FieldType erased_accessor::read(const Obj& x) const noexcept {
+    assert_name<Obj, FieldType>();
+    return read_unchecked<Obj, FieldType>(x);
+}
+
+template<typename Obj, typename FieldType>
+void erased_accessor::read(const Obj& x, FieldType& value) const noexcept
+{
+    assert_name<Obj, FieldType>();
+    read_unchecked<Obj, FieldType>(x, value);
+}
+
+template<typename Obj, typename FieldType>
+void erased_accessor::write(Obj& x, move_qualified<FieldType> value) const noexcept
+{
+    assert_name<Obj, FieldType>();
+    write_unchecked<Obj, FieldType>(x, value);
+}
+
+} // namespace floormat::entities
-- 
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