235 lines
8.5 KiB
C++
235 lines
8.5 KiB
C++
/* @file StructMember.hpp */
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#pragma once
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#include "xo/reflect/TypeDescr.hpp"
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#include "xo/reflect/EstablishTypeDescr.hpp"
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#include "xo/reflect/TaggedPtr.hpp"
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#include <string>
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#include <memory>
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namespace xo {
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namespace reflect {
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class AbstractStructMemberAccessor {
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public:
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virtual ~AbstractStructMemberAccessor() = default;
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/* get tagged pointer referring to this member of the object at *struct_addr */
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TaggedPtr member_tp(void * struct_addr) const;
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/* get type-description object for struct
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* containing this member. useful for consistency checking.
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*/
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virtual TypeDescr struct_td() const = 0;
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/* get type-description object for this member
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* e.g. if this member represents Foo::bar_ in
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* struct Foo { int bar_; };
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* then
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* .member_td() => Reflect::require<int>();
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*/
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virtual TypeDescr member_td() const = 0;
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/* get address of a particular member, given parent address */
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virtual void * address(void * struct_addr) const = 0;
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virtual std::unique_ptr<AbstractStructMemberAccessor> clone() const = 0;
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}; /*AbstractStructMemberAccessor*/
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/* GeneralStructMemberAccessor
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*
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* Use this to handle access to possibly-inherited struct members:
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*
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* struct Foo { int x_; }
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* struct Bar { char * y_; }
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* struct Quux : public Foo, public Bar { bool z_; }
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*
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* want to be able to access Bar::y from a Quux instance.
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* in example, would use GenericStructMemberAccessor<>
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* with:
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* StructT = Quux,
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* OwnerT = Bar,
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* MemberT = char*
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*
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* Require:
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* StructT* is assignable to OwnerT* (because StructT --isa--> OwnerT)
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*/
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template <typename StructT, typename OwnerT, typename MemberT>
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class GeneralStructMemberAccessor : public AbstractStructMemberAccessor {
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public:
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/* pointer to a OwnerT member of type MemberT */
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using Memptr = MemberT OwnerT::*;
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public:
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GeneralStructMemberAccessor(Memptr memptr) : member_td_{EstablishTypeDescr::establish<MemberT>()},
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memptr_{memptr} {}
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GeneralStructMemberAccessor(GeneralStructMemberAccessor const & x) = default;
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virtual ~GeneralStructMemberAccessor() = default;
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static std::unique_ptr<GeneralStructMemberAccessor> make(Memptr memptr) {
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return std::unique_ptr<GeneralStructMemberAccessor>(new GeneralStructMemberAccessor(memptr)); }
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/* get member address given address of parent struct
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* (i.e. from Struct*, not from OwnerT*)
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*/
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MemberT * address_impl(StructT * self_addr) const {
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OwnerT * owner_addr = self_addr;
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return &(owner_addr->*memptr_);
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} /*address_impl*/
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// ----- Inherited from AbstractStructMemberAccessor -----
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#ifdef OBSOLETE
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virtual TaggedPtr member_tp(void * struct_addr) const override {
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/* FIXME: this reports declared type of member, instead of
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* (possibly narrower) actual type of member
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*/
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return this->member_td_->most_derived_self_tp(this->address(struct_addr));
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//return TaggedPtr(this->member_td_, this->address(struct_addr));
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} /*member_tp*/
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#endif
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virtual TypeDescr struct_td() const override { return EstablishTypeDescr::establish<StructT>(); }
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virtual TypeDescr member_td() const override { return this->member_td_; }
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virtual void * address(void * struct_addr) const override {
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return this->address_impl(reinterpret_cast<StructT *>(struct_addr));
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} /*address*/
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virtual std::unique_ptr<AbstractStructMemberAccessor> clone() const override {
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return std::unique_ptr<AbstractStructMemberAccessor>
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(new GeneralStructMemberAccessor(*this));
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} /*clone*/
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private:
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/* type description for MemberT; .memptr is pointer-to-member-of-OwnerT,
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* where that member has type MemberT
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*/
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TypeDescr member_td_ = nullptr;
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/* pointer to member of OwnerT */
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Memptr memptr_ = nullptr;
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}; /*GeneralStructMemberAccessor*/
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/* struct-member accessor via delegation,
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* to accessor of a parent (or some other ancestor) class.
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*
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* struct Foo { int x_; }
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* struct Bar { char * y_; }
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*
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* auto bar_x_access = GeneralStructMemberAccessor<Bar, Foo, int>::make(&Foo::x_);
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*
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* or equivalently:
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* auto foo_x_access = GeneralStructMemberAccessor<Foo, Foo, int>::make(&Foo::x_);
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* auto bar_x_access = AncestorStructMemberAccessor<Bar, Foo>::adopt(foo_x_access);
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*
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* can use the 2nd form to adopt accessors from an already-reflected ancestor class
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*
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* Require:
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* - StructT -isa-> AncestorT
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*/
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template <typename StructT, typename AncestorT>
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class AncestorStructMemberAccessor : public AbstractStructMemberAccessor {
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public:
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AncestorStructMemberAccessor(std::unique_ptr<AbstractStructMemberAccessor> ancestor_accessor)
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: ancestor_accessor_{std::move(ancestor_accessor)} {}
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AncestorStructMemberAccessor(AncestorStructMemberAccessor const & x) = default;
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virtual ~AncestorStructMemberAccessor() = default;
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static std::unique_ptr<AncestorStructMemberAccessor>
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adopt(std::unique_ptr<AbstractStructMemberAccessor> ancestor_accessor) {
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return std::unique_ptr<AncestorStructMemberAccessor>
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(new AncestorStructMemberAccessor(std::move(ancestor_accessor)));
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} /*adopt*/
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void * address_impl(StructT * self_addr) const {
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/* to use access-via-ancestor, need to convert to ancestor pointer */
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AncestorT * ancestor_addr = self_addr;
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return this->ancestor_accessor_->address(ancestor_addr);
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} /*address_impl*/
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// ----- inherited from AbstractStructMemberAccessor -----
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#ifdef OBSOLETE
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virtual TaggedPtr member_tp(void * struct_addr) const override {
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AncestorT * ancestor_addr = reinterpret_cast<StructT *>(struct_addr);
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return this->ancestor_accessor_->member_tp(ancestor_addr);
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} /*member_tp*/
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#endif
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virtual TypeDescr struct_td() const override { return EstablishTypeDescr::establish<StructT>(); }
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virtual TypeDescr member_td() const override { return this->ancestor_accessor_->member_td(); }
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virtual void * address(void * struct_addr) const override {
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return this->address_impl(reinterpret_cast<StructT *>(struct_addr));
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}
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virtual std::unique_ptr<AbstractStructMemberAccessor> clone() const override {
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return std::unique_ptr<AbstractStructMemberAccessor>
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(new AncestorStructMemberAccessor(std::move(this->ancestor_accessor_->clone())));
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} /*clone*/
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private:
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/* .ancestor_accessor fetches some particular member of AncestorT */
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std::unique_ptr<AbstractStructMemberAccessor> ancestor_accessor_;
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}; /*AncestorStructMemberAccessor*/
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/* describes a member of a struct/class
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* see [reflect/StructReflector.hpp]
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*/
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class StructMember {
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public:
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StructMember() = default;
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StructMember(std::string const & name,
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std::unique_ptr<AbstractStructMemberAccessor> accessor)
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: member_name_{name}, accessor_{std::move(accessor)} {}
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StructMember(StructMember && x)
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: member_name_{std::move(x.member_name_)},
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accessor_{std::move(x.accessor_)} {}
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static StructMember null();
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std::string const & member_name() const { return member_name_; }
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TaggedPtr get_member_tp(void * struct_addr) const { return this->accessor_->member_tp(struct_addr); }
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TypeDescr get_struct_td() const { return this->accessor_->struct_td(); }
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TypeDescr get_member_td() const { return this->accessor_->member_td(); }
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//void * get_member_addr(void * struct_addr) const { return this->accessor_->address(struct_addr); }
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/* make copy that accesses this member, but starting
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* from pointer to some derived class DescendantT,
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* instead of from container type StructT known to (but not exposed by) *this
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*/
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template <typename DescendantT, typename StructT>
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StructMember for_descendant() const {
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assert(EstablishTypeDescr::establish<StructT>() == this->get_struct_td());
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return StructMember(this->member_name(),
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std::move(AncestorStructMemberAccessor<DescendantT, StructT>::adopt
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(std::move(this->accessor_->clone()))));
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} /*for_descendant*/
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StructMember & operator=(StructMember && x) {
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member_name_ = std::move(x.member_name_);
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accessor_ = std::move(x.accessor_);
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return *this;
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}
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private:
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/* member name, e.g. foo if
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* struct StructT { MemberT foo; }
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*/
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std::string member_name_;
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/* T recd;
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* this->accessor_->address_impl(&recd) ==> &(recd.member)
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*/
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std::unique_ptr<AbstractStructMemberAccessor> accessor_;
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}; /*StructMember*/
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} /*namespace reflect*/
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} /*namespace xo*/
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/* end StructMember.hpp */
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