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108 lines
3.2 KiB
C++
108 lines
3.2 KiB
C++
#include <Common/COW.h>
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#include <iostream>
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class IColumn : public COW<IColumn>
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{
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private:
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friend class COW<IColumn>;
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virtual MutablePtr clone() const = 0;
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virtual MutablePtr deepMutate() const { return shallowMutate(); }
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public:
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IColumn() = default;
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IColumn(const IColumn &) = default;
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virtual ~IColumn() = default;
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virtual int get() const = 0;
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virtual void set(int value) = 0;
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MutablePtr mutate() const && { return deepMutate(); }
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};
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using ColumnPtr = IColumn::Ptr;
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using MutableColumnPtr = IColumn::MutablePtr;
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class ConcreteColumn : public COWHelper<IColumn, ConcreteColumn>
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{
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private:
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friend class COWHelper<IColumn, ConcreteColumn>;
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int data;
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explicit ConcreteColumn(int data_) : data(data_) {}
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ConcreteColumn(const ConcreteColumn &) = default;
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public:
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int get() const override { return data; }
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void set(int value) override { data = value; }
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};
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class ColumnComposition : public COWHelper<IColumn, ColumnComposition>
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{
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private:
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friend class COWHelper<IColumn, ColumnComposition>;
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ConcreteColumn::WrappedPtr wrapped;
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explicit ColumnComposition(int data) : wrapped(ConcreteColumn::create(data)) {}
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ColumnComposition(const ColumnComposition &) = default;
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IColumn::MutablePtr deepMutate() const override
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{
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std::cerr << "Mutating\n";
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auto res = shallowMutate();
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res->wrapped = std::move(*wrapped).mutate();
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return res;
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}
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public:
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int get() const override { return wrapped->get(); }
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void set(int value) override { wrapped->set(value); }
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};
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int main(int, char **)
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{
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ColumnPtr x = ColumnComposition::create(1);
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ColumnPtr y = x;
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std::cerr << "values: " << x->get() << ", " << y->get() << "\n";
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std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n";
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std::cerr << "addresses: " << x.get() << ", " << y.get() << "\n";
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{
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MutableColumnPtr mut = std::move(*y).mutate();
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mut->set(2);
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std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << ", " << mut->use_count() << "\n";
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std::cerr << "addresses: " << x.get() << ", " << y.get() << ", " << mut.get() << "\n";
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y = std::move(mut);
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}
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std::cerr << "values: " << x->get() << ", " << y->get() << "\n";
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std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n";
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std::cerr << "addresses: " << x.get() << ", " << y.get() << "\n";
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x = ColumnComposition::create(0);
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std::cerr << "values: " << x->get() << ", " << y->get() << "\n";
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std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n";
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std::cerr << "addresses: " << x.get() << ", " << y.get() << "\n";
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{
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MutableColumnPtr mut = std::move(*y).mutate();
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mut->set(3);
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std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << ", " << mut->use_count() << "\n";
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std::cerr << "addresses: " << x.get() << ", " << y.get() << ", " << mut.get() << "\n";
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y = std::move(mut);
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}
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std::cerr << "values: " << x->get() << ", " << y->get() << "\n";
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std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n";
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return 0;
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}
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