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85 lines
1.9 KiB
C++
85 lines
1.9 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 <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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* 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 =
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#if defined(__GNUC__) && __GNUC__ < 5
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// GCC does not implement std::is_trivially_copyable until version 5.
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typename std::conditional<std::is_fundamental<T>::value || std::is_pointer<T>::value, std::atomic<T>, Locked<T>>::type;
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#else /* defined(__GNUC__) && __GNUC__ < 5 */
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typename std::conditional<std::is_trivially_copyable<T>::value, std::atomic<T>, Locked<T>>::type;
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#endif /* defined(__GNUC__) && __GNUC__ < 5 */
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}
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#endif /* ATOMIC_H */
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