c69ea32613
Previously, fc reflection generated visitor infrastructure capable of visiting each field of a struct; however, this is only useful for run- time operations on structures. No compile-time information was preserved about the fields of a struct, making compile-time introspection of types impossible. Now FC reflection generates rich compile-time information about the members of structs, including types, names, and structure, allowing code to be written to explore types in detail at compile-time and fetch arbitrary fields at runtime without needing to iterate over the unwanted fields. To make this a reality, a new `typelist` type was added to store this compile-time information. This type is also useful within the context of `static_variant`, as SV previously used implementation detail types in a private namespace to provide this functionality. Now `static_variant` uses the reusable functionality of `typelist` to operate, dramatically reducing the amount of code dedicated to `static_variant` and also making `static_variant` types more flexible to work with since their infrastructure is now based on the `typelist` public interface.
385 lines
15 KiB
C++
385 lines
15 KiB
C++
#pragma once
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/**
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* @file fc/reflect/reflect.hpp
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*
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* @brief Defines types and macros used to provide reflection.
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*
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*/
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#include <fc/string.hpp>
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#include <boost/lexical_cast.hpp>
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#include <boost/preprocessor/seq/for_each.hpp>
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#include <boost/preprocessor/seq/enum.hpp>
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#include <boost/preprocessor/seq/size.hpp>
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#include <boost/preprocessor/seq/seq.hpp>
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#include <boost/preprocessor/stringize.hpp>
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#include <stdint.h>
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#include <string.h>
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#include <type_traits>
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#include <fc/reflect/typename.hpp>
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#include <fc/reflect/typelist.hpp>
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namespace fc {
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template<typename> struct reflector;
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namespace member_names {
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/// A template which stores the name of the native member at a given index in a given class
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template<typename Class, std::size_t index> struct member_name {
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constexpr static const char* value = "Unknown member";
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};
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}
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/**
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* @brief A template to store compile-time information about a field in a reflected struct
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*
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* @tparam Container The type of the struct or class containing the field
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* @tparam Member The type of the field
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* @tparam field A pointer-to-member for the reflected field
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*/
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template<std::size_t Index, typename Container, typename Member, Member Container::*field>
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struct field_reflection {
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using container = Container;
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using type = Member;
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using reflector = fc::reflector<type>;
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constexpr static std::size_t index = Index;
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constexpr static bool is_derived = false;
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constexpr static type container::*pointer = field;
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/// @brief Given a reference to the container type, get a reference to the field
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static type& get(container& c) { return c.*field; }
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static const type& get(const container& c) { return c.*field; }
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/// @brief Get the name of the field
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static const char* get_name() { return fc::member_names::member_name<container, index>::value; }
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};
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/// Basically the same as @ref field_reflection, but for inherited fields
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/// Note that inherited field reflections do not have an index field; indexes are for native fields only
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template<std::size_t IndexInBase, typename Base, typename Derived, typename Member, Member Base::*field>
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struct inherited_field_reflection {
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using container = Derived;
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using field_container = Base;
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using type = Member;
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using reflector = fc::reflector<type>;
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constexpr static std::size_t index_in_base = IndexInBase;
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constexpr static bool is_derived = true;
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constexpr static type field_container::*pointer = field;
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static type& get(container& c) {
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// And we need a distinct inherited_field_reflection type because this conversion can't be done statically
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type container::* derived_field = field;
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return c.*derived_field;
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}
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static const type& get(const container& c) {
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type container::* derived_field = field;
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return c.*derived_field;
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}
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static const char* get_name() {
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using Reflector = typename fc::reflector<Base>::native_members::template at<IndexInBase>;
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return Reflector::get_name();
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}
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};
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namespace impl {
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/// Helper template to create a @ref field_reflection without any commas (makes it macro-friendly)
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template<typename Container>
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struct Reflect_type {
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template<typename Member>
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struct with_field_type {
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template<std::size_t Index>
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struct at_index {
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template<Member Container::*field>
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struct with_field_pointer {
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using type = field_reflection<Index, Container, Member, field>;
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};
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};
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};
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};
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/// Template to make a transformer of a @ref field_reflection from a base class to a derived class
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template<typename Derived>
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struct Derivation_reflection_transformer {
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template<typename> struct transform;
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template<std::size_t IndexInBase, typename BaseContainer, typename Member, Member BaseContainer::*field>
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struct transform<field_reflection<IndexInBase, BaseContainer, Member, field>> {
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using type = inherited_field_reflection<IndexInBase, BaseContainer, Derived, Member, field>;
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};
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template<std::size_t IndexInBase, typename BaseContainer, typename IntermediateContainer,
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typename Member, Member BaseContainer::*field>
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struct transform<inherited_field_reflection<IndexInBase, BaseContainer, IntermediateContainer, Member, field>> {
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using type = inherited_field_reflection<IndexInBase, BaseContainer, Derived, Member, field>;
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};
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};
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} // namespace impl
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/// Macro to transform reflected fields of a base class to a derived class and concatenate them to a type list
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#define FC_CONCAT_BASE_MEMBER_REFLECTIONS(r, derived, base) \
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::add_list<typelist::transform<reflector<base>::members, impl::Derivation_reflection_transformer<derived>>>
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/// Macro to concatenate a new @ref field_reflection to a typelist
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#define FC_CONCAT_MEMBER_REFLECTION(r, container, idx, member) \
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::add<typename impl::Reflect_type<container>::template with_field_type<decltype(container::member)> \
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::template at_index<idx> \
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::template with_field_pointer<&container::member>::type>
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#define FC_REFLECT_MEMBER_NAME(r, container, idx, member) \
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template<> struct member_name<container, idx> { constexpr static const char* value = BOOST_PP_STRINGIZE(member); };
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#define FC_REFLECT_TEMPLATE_MEMBER_NAME(r, data, idx, member) \
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template<BOOST_PP_SEQ_ENUM(BOOST_PP_SEQ_ELEM(0, data))> struct member_name<BOOST_PP_SEQ_ELEM(1, data), idx> { \
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constexpr static const char* value = BOOST_PP_STRINGIZE(member); };
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/// Macro to concatenate a new type to a typelist
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#define FC_CONCAT_TYPE(r, x, TYPE) ::add<TYPE>
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/**
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* @brief defines visit functions for T
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* Unless this is specialized, visit() will not be defined for T.
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*
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* @tparam T - the type that will be visited.
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*
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* The @ref FC_REFLECT(TYPE,MEMBERS) or FC_STATIC_REFLECT_DERIVED(TYPE,BASES,MEMBERS) macro is used to specialize this
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* class for your type.
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*/
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template<typename T>
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struct reflector{
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typedef T type;
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typedef std::false_type is_defined;
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/// A typelist with a @ref field_reflection for each native member (non-inherited) of the struct
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using native_members = typelist::list<>;
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/// A typelist with a @ref field_reflection for each inherited member of the struct
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using inherited_members = typelist::list<>;
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/// A typelist with a @ref field_reflection for each member of the struct, starting with inherited members
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using members = typelist::list<>;
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/// A typelist of base classes for this type
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using base_classes = typelist::list<>;
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/**
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* @tparam Visitor a function object of the form:
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*
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* @code
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* struct functor {
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* template<typename Member, class Class, Member (Class::*member)>
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* void operator()( const char* name )const;
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* };
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* @endcode
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*
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* If T is an enum then the functor has the following form:
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* @code
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* struct functor {
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* template<int Value>
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* void operator()( const char* name )const;
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* };
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* @endcode
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*
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* @param v a functor that will be called for each member on T
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*
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* @note - this method is not defined for non-reflected types.
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*/
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#ifdef DOXYGEN
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template<typename Visitor>
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static inline void visit( const Visitor& v );
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#endif // DOXYGEN
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};
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void throw_bad_enum_cast( int64_t i, const char* e );
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void throw_bad_enum_cast( const char* k, const char* e );
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} // namespace fc
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#ifndef DOXYGEN
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#define FC_REFLECT_VISIT_BASE(r, visitor, base) \
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fc::reflector<base>::visit( visitor );
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#ifndef _MSC_VER
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#define TEMPLATE template
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#else
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// Disable warning C4482: nonstandard extention used: enum 'enum_type::enum_value' used in qualified name
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#pragma warning( disable: 4482 )
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#define TEMPLATE
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#endif
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#define FC_REFLECT_VISIT_MEMBER( r, visitor, elem ) \
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{ typedef decltype(((type*)nullptr)->elem) member_type; \
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visitor.TEMPLATE operator()<member_type,type,&type::elem>( BOOST_PP_STRINGIZE(elem) ); \
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}
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#define FC_REFLECT_VISIT_MEMBER_I( r, visitor, I, elem ) \
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case I: FC_REFLECT_VISIT_MEMBER( r, visitor, elem ) break;
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#define FC_REFLECT_DERIVED_IMPL_INLINE( TYPE, INHERITS, MEMBERS ) \
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template<typename Visitor>\
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static inline void visit( const Visitor& v ) { \
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BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_VISIT_BASE, v, INHERITS ) \
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BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_VISIT_MEMBER, v, MEMBERS ) \
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}
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#endif // DOXYGEN
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#define FC_REFLECT_VISIT_ENUM( r, enum_type, elem ) \
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v.operator()(BOOST_PP_STRINGIZE(elem), int64_t(enum_type::elem) );
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#define FC_REFLECT_ENUM_TO_STRING( r, enum_type, elem ) \
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case enum_type::elem: return BOOST_PP_STRINGIZE(elem);
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#define FC_REFLECT_ENUM_TO_FC_STRING( r, enum_type, elem ) \
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case enum_type::elem: return std::string(BOOST_PP_STRINGIZE(elem));
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#define FC_REFLECT_ENUM_FROM_STRING( r, enum_type, elem ) \
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if( strcmp( s, BOOST_PP_STRINGIZE(elem) ) == 0 ) return enum_type::elem;
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#define FC_REFLECT_ENUM_FROM_STRING_CASE( r, enum_type, elem ) \
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case enum_type::elem:
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#define FC_REFLECT_ENUM( ENUM, FIELDS ) \
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namespace fc { \
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template<> struct reflector<ENUM> { \
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typedef std::true_type is_defined; \
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static const char* to_string(ENUM elem) { \
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switch( elem ) { \
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BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_ENUM_TO_STRING, ENUM, FIELDS ) \
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default: \
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fc::throw_bad_enum_cast( fc::to_string(int64_t(elem)).c_str(), BOOST_PP_STRINGIZE(ENUM) ); \
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}\
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return nullptr; \
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} \
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static const char* to_string(int64_t i) { \
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return to_string(ENUM(i)); \
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} \
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static std::string to_fc_string(ENUM elem) { \
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switch( elem ) { \
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BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_ENUM_TO_FC_STRING, ENUM, FIELDS ) \
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} \
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return fc::to_string(int64_t(elem)); \
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} \
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static std::string to_fc_string(int64_t i) { \
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return to_fc_string(ENUM(i)); \
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} \
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static ENUM from_int(int64_t i) { \
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ENUM e = ENUM(i); \
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switch( e ) \
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{ \
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BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_ENUM_FROM_STRING_CASE, ENUM, FIELDS ) \
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break; \
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default: \
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fc::throw_bad_enum_cast( i, BOOST_PP_STRINGIZE(ENUM) ); \
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} \
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return e;\
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} \
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static ENUM from_string( const char* s ) { \
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BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_ENUM_FROM_STRING, ENUM, FIELDS ) \
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int64_t i = 0; \
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try \
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{ \
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i = boost::lexical_cast<int64_t>(s); \
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} \
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catch( const boost::bad_lexical_cast& ) \
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{ \
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fc::throw_bad_enum_cast( s, BOOST_PP_STRINGIZE(ENUM) ); \
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} \
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return from_int(i); \
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} \
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template< typename Visitor > \
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static void visit( Visitor& v ) \
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{ \
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BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_VISIT_ENUM, ENUM, FIELDS ) \
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} \
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}; \
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template<> struct get_typename<ENUM> { static const char* name() { return BOOST_PP_STRINGIZE(ENUM); } }; \
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}
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/* Note: FC_REFLECT_ENUM previously defined this function, but I don't think it ever
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* did what we expected it to do. I've disabled it for now.
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*
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* template<typename Visitor> \
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* static inline void visit( const Visitor& v ) { \
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* BOOST_PP_SEQ_FOR_EACH( FC_REFLECT_VISIT_ENUM, ENUM, FIELDS ) \
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* }\
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*/
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/**
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* @def FC_REFLECT_DERIVED(TYPE,INHERITS,MEMBERS)
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*
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* @brief Specializes fc::reflector for TYPE where
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* type inherits other reflected classes
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*
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* @param INHERITS - a sequence of base class names (basea)(baseb)(basec)
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* @param MEMBERS - a sequence of member names. (field1)(field2)(field3)
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*/
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#define FC_REFLECT_DERIVED( TYPE, INHERITS, MEMBERS ) \
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namespace fc { \
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template<> struct get_typename<TYPE> { static const char* name() { return BOOST_PP_STRINGIZE(TYPE); } }; \
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template<> struct reflector<TYPE> {\
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typedef TYPE type; \
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typedef std::true_type is_defined; \
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using native_members = \
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typename typelist::builder<>::type \
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BOOST_PP_SEQ_FOR_EACH_I( FC_CONCAT_MEMBER_REFLECTION, TYPE, MEMBERS ) ::finalize; \
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using inherited_members = \
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typename typelist::builder<>::type \
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BOOST_PP_SEQ_FOR_EACH( FC_CONCAT_BASE_MEMBER_REFLECTIONS, TYPE, INHERITS ) ::finalize; \
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using members = typename typelist::concat<inherited_members, native_members>::type; \
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using base_classes = typename typelist::builder<>::type \
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BOOST_PP_SEQ_FOR_EACH( FC_CONCAT_TYPE, x, INHERITS ) ::finalize; \
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enum member_count_enum { \
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local_member_count = typelist::length<native_members>(), \
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total_member_count = typelist::length<members>() \
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}; \
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FC_REFLECT_DERIVED_IMPL_INLINE( TYPE, INHERITS, MEMBERS ) \
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}; \
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namespace member_names { \
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BOOST_PP_SEQ_FOR_EACH_I( FC_REFLECT_MEMBER_NAME, TYPE, MEMBERS ) \
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} }
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#define FC_REFLECT_DERIVED_TEMPLATE( TEMPLATE_ARGS, TYPE, INHERITS, MEMBERS ) \
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namespace fc { \
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template<BOOST_PP_SEQ_ENUM(TEMPLATE_ARGS)> struct get_typename<TYPE> { \
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static const char* name() { return BOOST_PP_STRINGIZE(TYPE); } \
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}; \
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template<BOOST_PP_SEQ_ENUM(TEMPLATE_ARGS)> struct reflector<TYPE> {\
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typedef TYPE type; \
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typedef std::true_type is_defined; \
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using native_members = \
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typename typelist::builder<>::type \
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BOOST_PP_SEQ_FOR_EACH_I( FC_CONCAT_MEMBER_REFLECTION, TYPE, MEMBERS ) ::finalize; \
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using inherited_members = \
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typename typelist::builder<>::type \
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BOOST_PP_SEQ_FOR_EACH( FC_CONCAT_BASE_MEMBER_REFLECTIONS, TYPE, INHERITS ) ::finalize; \
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using members = typename typelist::concat<inherited_members, native_members>::type; \
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using base_classes = typename typelist::builder<>::type \
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BOOST_PP_SEQ_FOR_EACH( FC_CONCAT_TYPE, x, INHERITS ) ::finalize; \
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enum member_count_enum { \
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local_member_count = typelist::length<native_members>(), \
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total_member_count = typelist::length<members>() \
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}; \
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FC_REFLECT_DERIVED_IMPL_INLINE( TYPE, INHERITS, MEMBERS ) \
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}; \
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namespace member_names { \
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BOOST_PP_SEQ_FOR_EACH_I( FC_REFLECT_TEMPLATE_MEMBER_NAME, (TEMPLATE_ARGS)(TYPE), MEMBERS ) \
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} }
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/**
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* @def FC_REFLECT(TYPE,MEMBERS)
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* @brief Specializes fc::reflector for TYPE
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*
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* @param MEMBERS - a sequence of member names. (field1)(field2)(field3)
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*
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* @see FC_REFLECT_DERIVED
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*/
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#define FC_REFLECT( TYPE, MEMBERS ) \
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FC_REFLECT_DERIVED( TYPE, BOOST_PP_SEQ_NIL, MEMBERS )
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#define FC_REFLECT_TEMPLATE( TEMPLATE_ARGS, TYPE, MEMBERS ) \
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FC_REFLECT_DERIVED_TEMPLATE( TEMPLATE_ARGS, TYPE, BOOST_PP_SEQ_NIL, MEMBERS )
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#define FC_REFLECT_EMPTY( TYPE ) \
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FC_REFLECT_DERIVED( TYPE, BOOST_PP_SEQ_NIL, BOOST_PP_SEQ_NIL )
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#define FC_REFLECT_TYPENAME( TYPE ) \
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namespace fc { \
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template<> struct get_typename<TYPE> { static const char* name() { return BOOST_PP_STRINGIZE(TYPE); } }; \
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}
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// vvv These are preserved to merge more smoothly vvv
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#define FC_REFLECT_BASE_MEMBER_COUNT( r, OP, elem ) \
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OP fc::reflector<elem>::total_member_count
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#define FC_REFLECT_MEMBER_COUNT( r, OP, elem ) \
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OP 1
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// ^^^ These can be removed after updating graphene/protocol/types.hpp ^^^
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