1 | #include <Common/COW.h> |
2 | #include <iostream> |
3 | |
4 | |
5 | class IColumn : public COW<IColumn> |
6 | { |
7 | private: |
8 | friend class COW<IColumn>; |
9 | |
10 | virtual MutablePtr clone() const = 0; |
11 | virtual MutablePtr deepMutate() const { return shallowMutate(); } |
12 | |
13 | public: |
14 | IColumn() = default; |
15 | IColumn(const IColumn &) = default; |
16 | virtual ~IColumn() = default; |
17 | |
18 | virtual int get() const = 0; |
19 | virtual void set(int value) = 0; |
20 | |
21 | MutablePtr mutate() const && { return deepMutate(); } |
22 | }; |
23 | |
24 | using ColumnPtr = IColumn::Ptr; |
25 | using MutableColumnPtr = IColumn::MutablePtr; |
26 | |
27 | class ConcreteColumn : public COWHelper<IColumn, ConcreteColumn> |
28 | { |
29 | private: |
30 | friend class COWHelper<IColumn, ConcreteColumn>; |
31 | |
32 | int data; |
33 | ConcreteColumn(int data_) : data(data_) {} |
34 | ConcreteColumn(const ConcreteColumn &) = default; |
35 | |
36 | public: |
37 | int get() const override { return data; } |
38 | void set(int value) override { data = value; } |
39 | }; |
40 | |
41 | class ColumnComposition : public COWHelper<IColumn, ColumnComposition> |
42 | { |
43 | private: |
44 | friend class COWHelper<IColumn, ColumnComposition>; |
45 | |
46 | ConcreteColumn::WrappedPtr wrapped; |
47 | |
48 | ColumnComposition(int data) : wrapped(ConcreteColumn::create(data)) {} |
49 | ColumnComposition(const ColumnComposition &) = default; |
50 | |
51 | IColumn::MutablePtr deepMutate() const override |
52 | { |
53 | std::cerr << "Mutating\n" ; |
54 | auto res = shallowMutate(); |
55 | res->wrapped = std::move(*wrapped).mutate(); |
56 | return res; |
57 | } |
58 | |
59 | public: |
60 | int get() const override { return wrapped->get(); } |
61 | void set(int value) override { wrapped->set(value); } |
62 | }; |
63 | |
64 | |
65 | int main(int, char **) |
66 | { |
67 | ColumnPtr x = ColumnComposition::create(1); |
68 | ColumnPtr y = x; |
69 | |
70 | std::cerr << "values: " << x->get() << ", " << y->get() << "\n" ; |
71 | std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n" ; |
72 | std::cerr << "addresses: " << x.get() << ", " << y.get() << "\n" ; |
73 | |
74 | { |
75 | MutableColumnPtr mut = std::move(*y).mutate(); |
76 | mut->set(2); |
77 | |
78 | std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << ", " << mut->use_count() << "\n" ; |
79 | std::cerr << "addresses: " << x.get() << ", " << y.get() << ", " << mut.get() << "\n" ; |
80 | y = std::move(mut); |
81 | } |
82 | |
83 | std::cerr << "values: " << x->get() << ", " << y->get() << "\n" ; |
84 | std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n" ; |
85 | std::cerr << "addresses: " << x.get() << ", " << y.get() << "\n" ; |
86 | |
87 | x = ColumnComposition::create(0); |
88 | |
89 | std::cerr << "values: " << x->get() << ", " << y->get() << "\n" ; |
90 | std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n" ; |
91 | std::cerr << "addresses: " << x.get() << ", " << y.get() << "\n" ; |
92 | |
93 | { |
94 | MutableColumnPtr mut = std::move(*y).mutate(); |
95 | mut->set(3); |
96 | |
97 | std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << ", " << mut->use_count() << "\n" ; |
98 | std::cerr << "addresses: " << x.get() << ", " << y.get() << ", " << mut.get() << "\n" ; |
99 | y = std::move(mut); |
100 | } |
101 | |
102 | std::cerr << "values: " << x->get() << ", " << y->get() << "\n" ; |
103 | std::cerr << "refcounts: " << x->use_count() << ", " << y->use_count() << "\n" ; |
104 | |
105 | return 0; |
106 | } |
107 | |
108 | |