src/tint/utils/reflection/reflection.h

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#ifndef SRC_TINT_UTILS_REFLECTION_REFLECTION_H_
#define SRC_TINT_UTILS_REFLECTION_REFLECTION_H_

#include <type_traits>

#include "src/tint/utils/macros/concat.h"
#include "src/tint/utils/macros/foreach.h"

namespace tint {

namespace detail {

/// Helper for detecting whether the type T contains a nested Reflection class.
template <typename T, typename ENABLE = void>
struct HasReflection : std::false_type {};

/// Specialization for types that have a nested Reflection class.
template <typename T>
struct HasReflection<T, std::void_t<typename T::Reflection>> : std::true_type {};

}  // namespace detail

/// Is true if the class T has reflected its fields with TINT_REFLECT()
template <typename T>
static constexpr bool HasReflection = tint::detail::HasReflection<T>::value;

/// Calls @p callback with each field of @p object
/// @param object the object
/// @param callback a function that is called for each field of @p object.
/// @tparam CB a function with the signature `void(FIELD)`
template <typename OBJECT, typename CB>
void ForeachField(OBJECT&& object, CB&& callback) {
    using T = std::decay_t<OBJECT>;
    static_assert(HasReflection<T>, "object type requires a tint::Reflect<> specialization");
    T::Reflection::Fields(object, callback);
}

/// Macro used by TINT_FOREACH() in TINT_REFLECT() to call the callback function with each field in
/// the variadic.
#define TINT_REFLECT_CALLBACK_FIELD(field) callback(object.field);

// TINT_REFLECT(...) reflects each of the fields arguments so that the types can be used with
// tint::ForeachField().
#define TINT_REFLECT(...)                                          \
    struct Reflection {                                            \
        template <typename OBJECT, typename CB>                    \
        static void Fields(OBJECT&& object, CB&& callback) {       \
            TINT_FOREACH(TINT_REFLECT_CALLBACK_FIELD, __VA_ARGS__) \
        }                                                          \
    }

}  // namespace tint

#endif  // SRC_TINT_UTILS_REFLECTION_REFLECTION_H_