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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___MEMORY_SHARED_COUNT_H
#define _LIBCPP___MEMORY_SHARED_COUNT_H
#include <__config>
#include <__memory/addressof.h>
#include <typeinfo>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
// NOTE: Relaxed and acq/rel atomics (for increment and decrement respectively)
// should be sufficient for thread safety.
// See https://llvm.org/PR22803
template <class _Tp>
inline _LIBCPP_HIDE_FROM_ABI _Tp __libcpp_atomic_refcount_increment(_Tp& __t) _NOEXCEPT {
#if _LIBCPP_HAS_THREADS
return __atomic_add_fetch(std::addressof(__t), 1, __ATOMIC_RELAXED);
#else
return __t += 1;
#endif
}
template <class _Tp>
inline _LIBCPP_HIDE_FROM_ABI _Tp __libcpp_atomic_refcount_decrement(_Tp& __t) _NOEXCEPT {
#if _LIBCPP_HAS_THREADS
return __atomic_add_fetch(std::addressof(__t), -1, __ATOMIC_ACQ_REL);
#else
return __t -= 1;
#endif
}
class _LIBCPP_EXPORTED_FROM_ABI __shared_count {
__shared_count(const __shared_count&);
__shared_count& operator=(const __shared_count&);
protected:
long __shared_owners_;
virtual ~__shared_count();
private:
virtual void __on_zero_shared() _NOEXCEPT = 0;
public:
_LIBCPP_HIDE_FROM_ABI explicit __shared_count(long __refs = 0) _NOEXCEPT : __shared_owners_(__refs) {}
#if defined(_LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS)
void __add_shared() noexcept;
bool __release_shared() noexcept;
#else
_LIBCPP_HIDE_FROM_ABI void __add_shared() _NOEXCEPT { __libcpp_atomic_refcount_increment(__shared_owners_); }
_LIBCPP_HIDE_FROM_ABI bool __release_shared() _NOEXCEPT {
if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1) {
__on_zero_shared();
return true;
}
return false;
}
#endif
_LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT {
#if _LIBCPP_HAS_THREADS
return __atomic_load_n(&__shared_owners_, __ATOMIC_RELAXED) + 1;
#else
return __shared_owners_ + 1;
#endif
}
};
class _LIBCPP_EXPORTED_FROM_ABI __shared_weak_count : private __shared_count {
long __shared_weak_owners_;
public:
_LIBCPP_HIDE_FROM_ABI explicit __shared_weak_count(long __refs = 0) _NOEXCEPT
: __shared_count(__refs),
__shared_weak_owners_(__refs) {}
protected:
~__shared_weak_count() override;
public:
#if defined(_LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS)
void __add_shared() noexcept;
void __add_weak() noexcept;
void __release_shared() noexcept;
#else
_LIBCPP_HIDE_FROM_ABI void __add_shared() _NOEXCEPT { __shared_count::__add_shared(); }
_LIBCPP_HIDE_FROM_ABI void __add_weak() _NOEXCEPT { __libcpp_atomic_refcount_increment(__shared_weak_owners_); }
_LIBCPP_HIDE_FROM_ABI void __release_shared() _NOEXCEPT {
if (__shared_count::__release_shared())
__release_weak();
}
#endif
void __release_weak() _NOEXCEPT;
_LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT { return __shared_count::use_count(); }
__shared_weak_count* lock() _NOEXCEPT;
virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;
private:
virtual void __on_zero_shared_weak() _NOEXCEPT = 0;
};
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___MEMORY_SHARED_COUNT_H
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