mirror of https://github.com/axmolengine/axmol.git
55 lines
1.8 KiB
C++
55 lines
1.8 KiB
C++
#ifndef AL_ATOMIC_H
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#define AL_ATOMIC_H
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#include <atomic>
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#include <utility>
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namespace al {
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struct atomic_invflag : protected std::atomic_flag {
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atomic_invflag() noexcept = default;
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template<typename T>
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atomic_invflag(T&& arg) noexcept : std::atomic_flag{std::forward<T>(arg)} { }
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inline bool test_and_clear(std::memory_order m=std::memory_order_seq_cst) noexcept
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{ return !test_and_set(m); }
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inline bool test_and_clear(std::memory_order m=std::memory_order_seq_cst) volatile noexcept
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{ return !test_and_set(m); }
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inline void set(std::memory_order m=std::memory_order_seq_cst) noexcept
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{ clear(m); }
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inline void set(std::memory_order m=std::memory_order_seq_cst) volatile noexcept
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{ clear(m); }
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};
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} // namespace al
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using RefCount = std::atomic<unsigned int>;
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inline void InitRef(RefCount &ref, unsigned int value)
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{ ref.store(value, std::memory_order_relaxed); }
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inline unsigned int ReadRef(RefCount &ref)
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{ return ref.load(std::memory_order_acquire); }
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inline unsigned int IncrementRef(RefCount &ref)
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{ return ref.fetch_add(1u, std::memory_order_acq_rel)+1u; }
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inline unsigned int DecrementRef(RefCount &ref)
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{ return ref.fetch_sub(1u, std::memory_order_acq_rel)-1u; }
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/* WARNING: A livelock is theoretically possible if another thread keeps
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* changing the head without giving this a chance to actually swap in the new
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* one (practically impossible with this little code, but...).
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*/
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template<typename T>
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inline void AtomicReplaceHead(std::atomic<T> &head, T newhead)
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{
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T first_ = head.load(std::memory_order_acquire);
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do {
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newhead->next.store(first_, std::memory_order_relaxed);
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} while(!head.compare_exchange_weak(first_, newhead,
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std::memory_order_acq_rel, std::memory_order_acquire));
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}
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#endif /* AL_ATOMIC_H */
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