52 lines
789 B
C
52 lines
789 B
C
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#pragma once
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#include <memory>
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#include <mutex>
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template<typename T>
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class Lazy {
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public:
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using value_type = T;
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explicit Lazy(std::function<T()> createValue) :
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createValue(createValue)
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{}
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explicit operator bool() const {
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return static_cast<bool>(_value);
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}
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T& value() {
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init();
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return *_value;
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}
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const T& value() const {
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init();
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return *_value;
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}
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T* operator->() {
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return &value();
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}
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const T* operator->() const {
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return &value();
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}
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T& operator*() {
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return value();
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}
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const T& operator*() const {
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return value();
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}
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private:
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void init() const {
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std::call_once(initialized, [&] { _value = std::make_unique<T>(createValue()); });
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}
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std::function<T()> createValue;
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mutable std::once_flag initialized;
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mutable std::unique_ptr<T> _value;
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};
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