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1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___MEMORY_SHARED_COUNT_H10#define _LIBCPP___MEMORY_SHARED_COUNT_H11 12#include <__config>13#include <__memory/addressof.h>14#include <typeinfo>15 16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)17# pragma GCC system_header18#endif19 20_LIBCPP_BEGIN_NAMESPACE_STD21 22// NOTE: Relaxed and acq/rel atomics (for increment and decrement respectively)23// should be sufficient for thread safety.24// See https://llvm.org/PR2280325 26template <class _Tp>27inline _LIBCPP_HIDE_FROM_ABI _Tp __libcpp_atomic_refcount_increment(_Tp& __t) _NOEXCEPT {28#if _LIBCPP_HAS_THREADS29 return __atomic_add_fetch(std::addressof(__t), 1, __ATOMIC_RELAXED);30#else31 return __t += 1;32#endif33}34 35template <class _Tp>36inline _LIBCPP_HIDE_FROM_ABI _Tp __libcpp_atomic_refcount_decrement(_Tp& __t) _NOEXCEPT {37#if _LIBCPP_HAS_THREADS38 return __atomic_add_fetch(std::addressof(__t), -1, __ATOMIC_ACQ_REL);39#else40 return __t -= 1;41#endif42}43 44class _LIBCPP_EXPORTED_FROM_ABI __shared_count {45 __shared_count(const __shared_count&);46 __shared_count& operator=(const __shared_count&);47 48protected:49 long __shared_owners_;50 virtual ~__shared_count();51 52private:53 virtual void __on_zero_shared() _NOEXCEPT = 0;54 55public:56 _LIBCPP_HIDE_FROM_ABI explicit __shared_count(long __refs = 0) _NOEXCEPT : __shared_owners_(__refs) {}57 58#if defined(_LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS)59 void __add_shared() noexcept;60 bool __release_shared() noexcept;61#else62 _LIBCPP_HIDE_FROM_ABI void __add_shared() _NOEXCEPT { __libcpp_atomic_refcount_increment(__shared_owners_); }63 _LIBCPP_HIDE_FROM_ABI bool __release_shared() _NOEXCEPT {64 if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1) {65 __on_zero_shared();66 return true;67 }68 return false;69 }70#endif71 _LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT {72#if _LIBCPP_HAS_THREADS73 return __atomic_load_n(&__shared_owners_, __ATOMIC_RELAXED) + 1;74#else75 return __shared_owners_ + 1;76#endif77 }78};79 80class _LIBCPP_EXPORTED_FROM_ABI __shared_weak_count : private __shared_count {81 long __shared_weak_owners_;82 83public:84 _LIBCPP_HIDE_FROM_ABI explicit __shared_weak_count(long __refs = 0) _NOEXCEPT85 : __shared_count(__refs),86 __shared_weak_owners_(__refs) {}87 88protected:89 ~__shared_weak_count() override;90 91public:92#if defined(_LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS)93 void __add_shared() noexcept;94 void __add_weak() noexcept;95 void __release_shared() noexcept;96#else97 _LIBCPP_HIDE_FROM_ABI void __add_shared() _NOEXCEPT { __shared_count::__add_shared(); }98 _LIBCPP_HIDE_FROM_ABI void __add_weak() _NOEXCEPT { __libcpp_atomic_refcount_increment(__shared_weak_owners_); }99 _LIBCPP_HIDE_FROM_ABI void __release_shared() _NOEXCEPT {100 if (__shared_count::__release_shared())101 __release_weak();102 }103#endif104 void __release_weak() _NOEXCEPT;105 _LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT { return __shared_count::use_count(); }106 __shared_weak_count* lock() _NOEXCEPT;107 108 virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;109 110private:111 virtual void __on_zero_shared_weak() _NOEXCEPT = 0;112};113 114_LIBCPP_END_NAMESPACE_STD115 116#endif // _LIBCPP___MEMORY_SHARED_COUNT_H117