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296 lines
11 KiB
C++
296 lines
11 KiB
C++
/* Copyright (C) 2016
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* swift Project Community / Contributors
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*
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* This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
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* directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
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* including this file, may be copied, modified, propagated, or distributed except according to the terms
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* contained in the LICENSE file.
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*/
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//! \file
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#ifndef BLACKMISC_METACLASS_H
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#define BLACKMISC_METACLASS_H
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#include "blackmisc/metaclassprivate.h"
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#include "blackmisc/invoke.h"
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/*!
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* \defgroup MetaClass Metaclass system
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* Compile-time reflection toolkit for iterating over
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* members of value classes.
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*/
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/*!
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* Macro to define a nested metaclass that describes the attributes of its
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* enclosing class. Use in the private section of the class.
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*
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* \tparam CLASS The name of the class containing the member.
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* \note A semicolon is needed at the end.
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* \ingroup MetaClass
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*/
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#define BLACK_METACLASS(CLASS, ...) \
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friend struct BlackMisc::Private::CMetaClassAccessor; \
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struct MetaClass : public BlackMisc::CMetaClass \
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{ \
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using Class = CLASS; \
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BLACK_NO_EXPORT_CONSTEXPR static auto getMemberList() \
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{ \
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return makeMetaMemberList(__VA_ARGS__); \
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} \
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}
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/*!
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* Macro to define an element within a metaclass.
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*
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* Additional arguments can be supplied in the variadic part, which will be
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* forwarded to CMetaClass::makeMetaMember.
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*
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* \tparam MEMBER The name of the member without m_ part.
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* \see BLACK_METACLASS
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* \see BLACK_METAMEMBER_NAMED
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* \see BlackMisc::CMetaClass::makeMetaMember
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* \ingroup MetaClass
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*/
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#define BLACK_METAMEMBER(MEMBER, ...) \
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makeMetaMember( \
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&Class::m_##MEMBER, #MEMBER BLACK_TRAILING_VA_ARGS(__VA_ARGS__) \
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)
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/*!
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* Same as BLACK_METAMEMBER but the second parameter is a string literal
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* containing the JSON name of the member.
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*
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* \ingroup MetaClass
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*/
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#define BLACK_METAMEMBER_NAMED(MEMBER, NAME, ...) \
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makeMetaMember( \
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&Class::m_##MEMBER, NAME BLACK_TRAILING_VA_ARGS(__VA_ARGS__) \
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)
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namespace BlackMisc
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{
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class CVariant;
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/*!
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* Type wrapper for passing MetaFlag to CMetaClassIntrospector::with and CMetaClassIntrospector::without.
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* \ingroup MetaClass
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*/
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template <quint64 F>
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struct MetaFlags : public std::integral_constant<quint64, F>
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{
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//! Implicit conversion to std::false_type (if F is zero) or std::true_type (if F is non-zero).
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constexpr operator std::integral_constant<bool, static_cast<bool>(F)>() const { return {}; }
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};
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/*!
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* Compile-time union of MetaFlags.
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* \ingroup MetaClass
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*/
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template <quint64 A, quint64 B>
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constexpr MetaFlags<A | B> operator |(MetaFlags<A>, MetaFlags<B>) { return {}; }
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/*!
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* Compile-time intersection of MetaFlags.
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* \ingroup MetaClass
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*/
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template <quint64 A, quint64 B>
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constexpr MetaFlags<A & B> operator &(MetaFlags<A>, MetaFlags<B>) { return {}; }
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/*!
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* Literal aggregate type representing attributes of one member of a value class.
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* \ingroup MetaClass
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*/
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template <typename M, quint64 Flags>
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struct CMetaMember
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{
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//! Pointer to the member.
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const M m_ptr;
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//! Member name.
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const char *const m_name;
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//! Property index of the member.
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//! \deprecated Reserved for future use.
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const int m_index;
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//! Any flags applying to the member.
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const MetaFlags<Flags> m_flags;
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//! True if m_flags contains all flags.
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template <typename Flags2>
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constexpr bool has(Flags2 flags) const { return (m_flags & flags) == flags; }
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//! Invoke the member on an instance of the value class.
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template <typename T, typename... Ts>
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decltype(auto) in(T &&object, Ts &&... args) const
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{
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return Private::invoke(m_ptr, std::forward<T>(object), std::forward<Ts>(args)...);
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}
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//! Return name as QLatin1String.
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Q_DECL_CONSTEXPR auto latin1Name() const { return QLatin1String(m_name); }
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};
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/*!
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* Literal aggregate type representing attributes of the members of a value class.
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* \ingroup MetaClass
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*/
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template <typename... Members>
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struct CMetaMemberList
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{
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//! Tuple of CMetaMember.
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const Private::tuple<Members...> m_members;
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//! Number of members.
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static constexpr size_t c_size = sizeof...(Members);
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//! Convenience method returning the member at index I.
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template <size_t I>
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constexpr auto at(std::integral_constant<size_t, I> = {}) const BLACK_TRAILING_RETURN(Private::get<I>(m_members))
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{
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return Private::get<I>(m_members);
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}
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};
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/*!
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* Metadata flags attached to members of a meta class.
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* \ingroup MetaClass
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*/
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enum MetaFlag
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{
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DisabledForComparison = 1 << 0, //!< Element will be ignored by compare() and comparison operators
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DisabledForMarshalling = 1 << 1, //!< Element will be ignored during DBus marshalling
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DisabledForDebugging = 1 << 2, //!< Element will be ignored when streaming to QDebug
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DisabledForHashing = 1 << 3, //!< Element will be ignored by qHash()
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DisabledForJson = 1 << 4, //!< Element will be ignored during JSON serialization
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CaseInsensitiveComparison = 1 << 5 //!< Element will be compared case insensitively (must be a QString)
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};
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/*!
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* Base class for meta classes.
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* Just static protected members to be used by derived meta classes.
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* \ingroup MetaClass
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*/
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class CMetaClass
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{
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protected:
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//! Flags wrapped as compile-time constants.
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//! @{
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constexpr static MetaFlags<MetaFlag::DisabledForComparison> DisabledForComparison {};
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constexpr static MetaFlags<MetaFlag::DisabledForMarshalling> DisabledForMarshalling {};
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constexpr static MetaFlags<MetaFlag::DisabledForDebugging> DisabledForDebugging {};
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constexpr static MetaFlags<MetaFlag::DisabledForHashing> DisabledForHashing {};
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constexpr static MetaFlags<MetaFlag::DisabledForJson> DisabledForJson {};
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constexpr static MetaFlags<MetaFlag::CaseInsensitiveComparison> CaseInsensitiveComparison {};
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//! @}
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//! Return a CMetaMemberList of type deduced from the types of the meta members.
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//! Usually not used directly, but via the macros.
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template <typename... Members>
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constexpr static CMetaMemberList<Members...> makeMetaMemberList(Members... members)
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{
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return { Private::tuple<Members...>(members...) };
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}
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//! Return a CMetaMethod of type deduced from the type of the member.
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//! Usually not used directly, but via the macros.
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template <typename M, quint64 Flags = 0>
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constexpr static CMetaMember<M, Flags> makeMetaMember(M ptrToMember, const char *name = nullptr, int index = 0, MetaFlags<Flags> flags = {})
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{
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static_assert(std::is_member_object_pointer<M>::value, "M must be a pointer to member object");
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return { ptrToMember, name, index, flags };
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}
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};
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/*!
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* Implementation of an introspector for the metaclass of T.
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* Obtain an instance of this class via BlackMisc::introspect.
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* \ingroup MetaClass
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*/
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template <typename T, typename MetaClass, size_t... Is>
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class CMetaClassIntrospector
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{
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public:
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//! Return a CMetaClassIntrospector<T> covering only those members which have the given flags.
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//! \see BlackMisc::MetaFlags
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template <typename Flags>
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static auto with(Flags) { return filter(MaskSequence<(members().at(index<Is>()).has(Flags()))...>()); }
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//! Return a CMetaClassIntrospector<T> covering only those members which do not have the given flags.
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//! \see BlackMisc::MetaFlags
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template <typename Flags>
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static auto without(Flags) { return filter(MaskSequence<(! members().at(index<Is>()).has(Flags()))...>()); }
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//! For each metamember in metaclass, pass metamember as argument to visitor function.
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template <typename F>
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static void forEachMember(F &&visitor)
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{
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// parameter pack swallow idiom
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static_cast<void>(std::initializer_list<int>
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{
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(static_cast<void>(std::forward<F>(visitor)(members().at(index<Is>()))), 0)...
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});
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}
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private:
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template <bool... Mask>
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using MaskSequence = Private::MaskSequence<Private::index_sequence<Is...>, Mask...>;
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template <size_t... Js>
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static auto filter(Private::index_sequence<Js...>) { return CMetaClassIntrospector<T, MetaClass, Js...>(); }
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template <size_t I>
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using index = std::integral_constant<size_t, I>;
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constexpr static auto members() BLACK_TRAILING_RETURN(MetaClass::getMemberList()) { return MetaClass::getMemberList(); }
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};
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namespace Private
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{
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//! \private Friend class of all value classes, so it can access the private nested class.
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struct CMetaClassAccessor
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{
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template <typename T, size_t... Is>
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static auto getIntrospector(index_sequence<Is...>)
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{
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return CMetaClassIntrospector<T, typename T::MetaClass, Is...>();
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}
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template <typename T>
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static auto getIntrospector()
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{
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return getIntrospector<T>(Private::make_index_sequence<T::MetaClass::getMemberList().c_size>());
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}
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template <typename T>
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static std::true_type hasMetaClass(int, typename T::MetaClass * = nullptr) { return {}; }
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template <typename T>
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static std::false_type hasMetaClass(...) { return {}; }
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};
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}
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/*!
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* Obtain the CMetaClassIntrospector for the metaclass of T.
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* \return BlackMisc::CMetaClassIntrospector
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* \ingroup MetaClass
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*/
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template <typename T>
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auto introspect()
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{
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return Private::CMetaClassAccessor::getIntrospector<T>();
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}
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/*!
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* Trait that is true if T has a metaclass.
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* \ingroup MetaClass
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*/
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template <typename T>
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struct THasMetaClass : public decltype(Private::CMetaClassAccessor::hasMetaClass<T>(0)) {};
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} // namespace
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#endif
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