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/* Icinga 2 | (c) 2019 Icinga GmbH | GPLv2+ */
#ifndef ATOMIC_H
#define ATOMIC_H
#include <atomic>
#include <mutex>
#include <type_traits>
#include <utility>
namespace icinga
{
/**
* Extends std::atomic with an atomic constructor.
*
* @ingroup base
*/
template<class T>
class Atomic : public std::atomic<T> {
public:
/**
* Like std::atomic#atomic, but operates atomically
*
* @param desired Initial value
*/
inline Atomic(T desired)
{
this->store(desired);
}
/**
* Like std::atomic#atomic, but operates atomically
*
* @param desired Initial value
* @param order Initial store operation's memory order
*/
inline Atomic(T desired, std::memory_order order)
{
this->store(desired, order);
}
};
/**
* Wraps any T into a std::atomic<T>-like interface that locks using a mutex.
*
* In contrast to std::atomic<T>, Locked<T> is also valid for types that are not trivially copyable.
* In case T is trivially copyable, std::atomic<T> is almost certainly the better choice.
*
* @ingroup base
*/
template<typename T>
class Locked
{
public:
inline T load() const
{
std::unique_lock<std::mutex> lock(m_Mutex);
return m_Value;
}
inline void store(T desired)
{
std::unique_lock<std::mutex> lock(m_Mutex);
m_Value = std::move(desired);
}
private:
mutable std::mutex m_Mutex;
T m_Value;
};
/**
* Type alias for std::atomic<T> if possible, otherwise Locked<T> is used as a fallback.
*
* @ingroup base
*/
template <typename T>
using AtomicOrLocked =
#if defined(__GNUC__) && __GNUC__ < 5
// GCC does not implement std::is_trivially_copyable until version 5.
typename std::conditional<std::is_fundamental<T>::value || std::is_pointer<T>::value, std::atomic<T>, Locked<T>>::type;
#else /* defined(__GNUC__) && __GNUC__ < 5 */
typename std::conditional<std::is_trivially_copyable<T>::value, std::atomic<T>, Locked<T>>::type;
#endif /* defined(__GNUC__) && __GNUC__ < 5 */
}
#endif /* ATOMIC_H */
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