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#pragma once
#include "defs.h"
template<typename TValue>
class TIndirectReferable {
friend class TPtr;
TValue *Current;
public:
class TPtr {
const TValue *Object = nullptr;
public:
TPtr() = default;
TPtr(const TValue *object)
: Object(object)
{}
operator const TValue*() const {
return Get();
}
const TValue *operator ->() const {
return *this;
}
const TValue& operator *() const {
const TValue *ptr = Get();
Y_VERIFY_DEBUG(ptr);
return *ptr;
}
// MUST be called from OnCommit() only
TValue& Mutable() const {
TValue *ptr = Get();
Y_VERIFY_DEBUG(ptr);
return *ptr;
}
private:
TValue *Get() const {
return Object ? Object->Current : nullptr;
}
};
public:
TIndirectReferable()
: Current(static_cast<TValue*>(this))
{}
TIndirectReferable(const TIndirectReferable&)
: TIndirectReferable() // prevent from copying link -- set it up for outselves
{}
TIndirectReferable& operator =(const TIndirectReferable&) = delete;
TIndirectReferable& operator =(TIndirectReferable&&) = delete;
// TOverlayMap machinery
void OnClone(const THolder<TValue>& clone) {
Y_VERIFY_DEBUG(Current == this);
Current = clone.Get();
}
std::pair<void**, void*> Preserve() {
Y_VERIFY_DEBUG(Current != this);
return std::make_pair((void**)&Current, (void*)std::exchange(Current, static_cast<TValue*>(this)));
}
void OnRollback() {
Current = static_cast<TValue*>(this);
}
};
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