#ifndef INTRUSIVE_PTR_H #define INTRUSIVE_PTR_H #include "atomic.h" #include "opthelpers.h" namespace al { template<typename T> class intrusive_ref { RefCount mRef{1u}; public: unsigned int add_ref() noexcept { return IncrementRef(mRef); } unsigned int release() noexcept { auto ref = DecrementRef(mRef); if UNLIKELY(ref == 0) delete static_cast<T*>(this); return ref; } /** * Release only if doing so would not bring the object to 0 references and * delete it. Returns false if the object could not be released. * * NOTE: The caller is responsible for handling a failed release, as it * means the object has no other references and needs to be be deleted * somehow. */ bool releaseIfNoDelete() noexcept { auto val = mRef.load(std::memory_order_acquire); while(val > 1 && !mRef.compare_exchange_strong(val, val-1, std::memory_order_acq_rel)) { /* val was updated with the current value on failure, so just try * again. */ } return val >= 2; } }; template<typename T> class intrusive_ptr { T *mPtr{nullptr}; public: intrusive_ptr() noexcept = default; intrusive_ptr(const intrusive_ptr &rhs) noexcept : mPtr{rhs.mPtr} { if(mPtr) mPtr->add_ref(); } intrusive_ptr(intrusive_ptr&& rhs) noexcept : mPtr{rhs.mPtr} { rhs.mPtr = nullptr; } intrusive_ptr(std::nullptr_t) noexcept { } explicit intrusive_ptr(T *ptr) noexcept : mPtr{ptr} { } ~intrusive_ptr() { reset(); } intrusive_ptr& operator=(const intrusive_ptr &rhs) noexcept { if(rhs.mPtr) rhs.mPtr->add_ref(); if(mPtr) mPtr->release(); mPtr = rhs.mPtr; return *this; } intrusive_ptr& operator=(intrusive_ptr&& rhs) noexcept { std::swap(mPtr, rhs.mPtr); return *this; } operator bool() const noexcept { return mPtr != nullptr; } T& operator*() const noexcept { return *mPtr; } T* operator->() const noexcept { return mPtr; } T* get() const noexcept { return mPtr; } void reset() noexcept { if(mPtr) mPtr->release(); mPtr = nullptr; } T* release() noexcept { T *ret{mPtr}; mPtr = nullptr; return ret; } void swap(intrusive_ptr &rhs) noexcept { std::swap(mPtr, rhs.mPtr); } void swap(intrusive_ptr&& rhs) noexcept { std::swap(mPtr, rhs.mPtr); } }; #define AL_DECL_OP(op) \ template<typename T> \ inline bool operator op(const intrusive_ptr<T> &lhs, const T *rhs) noexcept \ { return lhs.get() op rhs; } \ template<typename T> \ inline bool operator op(const T *lhs, const intrusive_ptr<T> &rhs) noexcept \ { return lhs op rhs.get(); } AL_DECL_OP(==) AL_DECL_OP(!=) AL_DECL_OP(<=) AL_DECL_OP(>=) AL_DECL_OP(<) AL_DECL_OP(>) #undef AL_DECL_OP } // namespace al #endif /* INTRUSIVE_PTR_H */