feat(furvm): add a thing

furvm/include/furvm/thing.hpp

@@ -0,0 +1,59 @@
+#ifndef FURVM_THING_HPP
+#define FURVM_THING_HPP
+
+#include "furvm/fwd.hpp"
+
+#include <memory>
+
+namespace furvm {
+
+enum class thing_t : std::uint8_t {
+    Int,
+};
+
+class thing {
+    friend class executor;
+private:
+    /**
+     * @brief A private token for the private constructor.
+     *
+     * Also `rzecz` in Polish translates to `thing` I think.
+     */
+    struct rzecz {
+        explicit rzecz() = default;
+    };
+public:
+    /**
+     * @brief Private constructor.
+     *
+     * @param id
+     * @param type
+     * @param context
+     */
+    thing(rzecz, thing_handle id, thing_t type, const std::shared_ptr<context>& context);
+
+    ~thing();
+
+    /**
+     * @brief Move constructor.
+     */
+    thing(thing&&) noexcept = default;
+
+    /**
+     * @brief Move constructor.
+     */
+    thing& operator=(thing&&) noexcept = default;
+
+    thing(const thing&)            = delete;
+    thing& operator=(const thing&) = delete;
+private:
+    thing_handle             m_id;
+    thing_t                  m_type;
+    std::shared_ptr<context> m_context;
+
+    void* m_data;
+};
+
+} // namespace furvm
+
+#endif // FURVM_THING_HPP