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#ifndef AL_ATOMIC_H
#define AL_ATOMIC_H
#include <atomic>
using RefCount = std::atomic<unsigned int>;
inline void InitRef(RefCount *ptr, unsigned int value)
{ ptr->store(value, std::memory_order_relaxed); }
inline unsigned int ReadRef(RefCount *ptr)
{ return ptr->load(std::memory_order_acquire); }
inline unsigned int IncrementRef(RefCount *ptr)
{ return ptr->fetch_add(1u, std::memory_order_acq_rel)+1u; }
inline unsigned int DecrementRef(RefCount *ptr)
{ return ptr->fetch_sub(1u, std::memory_order_acq_rel)-1u; }
/* WARNING: A livelock is theoretically possible if another thread keeps
* changing the head without giving this a chance to actually swap in the new
* one (practically impossible with this little code, but...).
*/
template<typename T>
inline void AtomicReplaceHead(std::atomic<T> &head, T newhead)
{
T first_ = head.load(std::memory_order_acquire);
do {
newhead->next.store(first_, std::memory_order_relaxed);
} while(!head.compare_exchange_weak(first_, newhead,
std::memory_order_acq_rel, std::memory_order_acquire));
}
#endif /* AL_ATOMIC_H */
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