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Add support for querying offsets #39

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Add support for querying offsets #39

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38 changes: 38 additions & 0 deletions include/visit_struct/visit_struct.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -275,6 +275,22 @@ VISIT_STRUCT_CONSTEXPR auto get_accessor(S &&) -> decltype(get_accessor<idx, S>(
return get_accessor<idx, S>();
}

// Get member offset, by index
template <int idx, typename S>
VISIT_STRUCT_CONSTEXPR auto get_offset() ->
typename std::enable_if<
traits::is_visitable<traits::clean_t<S>>::value,
decltype(traits::visitable<traits::clean_t<S>>::get_offset(std::integral_constant<int, idx>{}))
>::type
{
return traits::visitable<traits::clean_t<S>>::get_offset(std::integral_constant<int, idx>{});
}

template <int idx, typename S>
VISIT_STRUCT_CONSTEXPR auto get_offset(S &&) -> size_t {
return get_offset<idx, S>();
}

// Get type, by index
template <int idx, typename S>
struct type_at_s {
Expand All @@ -285,6 +301,7 @@ struct type_at_s {
template <int idx, typename S>
using type_at = typename type_at_s<idx, S>::type;


// Get name of structure
template <typename S>
VISIT_STRUCT_CONSTEXPR auto get_name() ->
Expand Down Expand Up @@ -638,6 +655,9 @@ static VISIT_STRUCT_CONSTEXPR const int max_visitable_members = 69;
* These macros are used with VISIT_STRUCT_PP_MAP
*/

#define VISIT_STRUCT_MEMBER_HELPER_OFFSET(MEMBER_NAME) \
std::forward<V>(visitor)(#MEMBER_NAME, [](){return offsetof(this_type, MEMBER_NAME);});

#define VISIT_STRUCT_FIELD_COUNT(MEMBER_NAME) \
+ 1

Expand Down Expand Up @@ -683,6 +703,12 @@ static VISIT_STRUCT_CONSTEXPR const int max_visitable_members = 69;
return {}; \
} \
\
static VISIT_STRUCT_CONSTEXPR auto \
get_offset(std::integral_constant<int, fields_enum::MEMBER_NAME>) -> \
size_t { \
return offsetof(this_type, MEMBER_NAME); \
} \
\
static auto \
type_at(std::integral_constant<int, fields_enum::MEMBER_NAME>) -> \
visit_struct::type_c<decltype(this_type::MEMBER_NAME)>;
Expand Down Expand Up @@ -749,6 +775,12 @@ struct visitable<STRUCT_NAME, void> {
VISIT_STRUCT_PP_MAP(VISIT_STRUCT_MEMBER_HELPER_ACC, __VA_ARGS__) \
} \
\
template <typename V> \
VISIT_STRUCT_CXX14_CONSTEXPR static void visit_offsets(V && visitor) \
{ \
VISIT_STRUCT_PP_MAP(VISIT_STRUCT_MEMBER_HELPER_OFFSET, __VA_ARGS__) \
} \
\
struct fields_enum { \
enum index { __VA_ARGS__ }; \
}; \
Expand Down Expand Up @@ -809,6 +841,12 @@ struct visitable<STRUCT_NAME, CONTEXT> {
VISIT_STRUCT_PP_MAP(VISIT_STRUCT_MEMBER_HELPER_ACC, __VA_ARGS__) \
} \
\
template <typename V> \
VISIT_STRUCT_CXX14_CONSTEXPR static void visit_offsets(V && visitor) \
{ \
VISIT_STRUCT_PP_MAP(VISIT_STRUCT_MEMBER_HELPER_OFFSET, __VA_ARGS__) \
} \
\
struct fields_enum { \
enum index { __VA_ARGS__ }; \
}; \
Expand Down