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d372ecc20b
std::conditional_t was added in C++14, is_trivially_copyable_v in C++17, both do the same as the previous implementation and are a bit more compact.
117 lines
2.4 KiB
C++
117 lines
2.4 KiB
C++
/* Icinga 2 | (c) 2019 Icinga GmbH | GPLv2+ */
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#ifndef ATOMIC_H
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#define ATOMIC_H
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#include <atomic>
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#include <chrono>
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#include <mutex>
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#include <type_traits>
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#include <utility>
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namespace icinga
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{
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/**
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* Like std::atomic, but enforces usage of its only safe constructor.
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*
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* "The default-initialized std::atomic<T> does not contain a T object,
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* and its only valid uses are destruction and
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* initialization by std::atomic_init, see LWG issue 2334."
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* -- https://en.cppreference.com/w/cpp/atomic/atomic/atomic
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*
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* @ingroup base
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*/
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template<class T>
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class Atomic : public std::atomic<T> {
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public:
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/**
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* The only safe constructor of std::atomic#atomic
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*
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* @param desired Initial value
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*/
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inline Atomic(T desired) : std::atomic<T>(desired)
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{
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}
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};
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/**
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* Accumulates time durations atomically.
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*
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* @ingroup base
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*/
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class AtomicDuration
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{
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public:
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using Clock = std::chrono::steady_clock;
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/**
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* Adds the elapsedTime to this instance.
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*
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* May be called multiple times to accumulate time.
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*
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* @param elapsedTime The distance between two time points
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*
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* @return This instance for method chaining
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*/
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AtomicDuration& operator+=(const Clock::duration& elapsedTime) noexcept
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{
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m_Sum.fetch_add(elapsedTime.count(), std::memory_order_relaxed);
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return *this;
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}
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/**
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* @return The total accumulated time in seconds
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*/
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operator double() const noexcept
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{
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return std::chrono::duration<double>(Clock::duration(m_Sum.load(std::memory_order_relaxed))).count();
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}
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private:
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Atomic<Clock::duration::rep> m_Sum {0};
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};
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/**
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* Wraps any T into a std::atomic<T>-like interface that locks using a mutex.
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*
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* In contrast to std::atomic<T>, Locked<T> is also valid for types that are not trivially copyable.
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* In case T is trivially copyable, std::atomic<T> is almost certainly the better choice.
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*
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* @ingroup base
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*/
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template<typename T>
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class Locked
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{
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public:
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inline T load() const
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{
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std::unique_lock<std::mutex> lock(m_Mutex);
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return m_Value;
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}
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inline void store(T desired)
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{
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std::unique_lock<std::mutex> lock(m_Mutex);
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m_Value = std::move(desired);
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}
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private:
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mutable std::mutex m_Mutex;
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T m_Value;
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};
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/**
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* Type alias for std::atomic<T> if possible, otherwise Locked<T> is used as a fallback.
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*
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* @ingroup base
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*/
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template <typename T>
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using AtomicOrLocked = std::conditional_t<std::is_trivially_copyable_v<T>, std::atomic<T>, Locked<T>>;
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}
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#endif /* ATOMIC_H */
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