shared_ptr_atomic.h
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// shared_ptr atomic access -*- C++ -*-
// Copyright (C) 2014-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file bits/shared_ptr_atomic.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{memory}
*/
#ifndef _SHARED_PTR_ATOMIC_H
#define _SHARED_PTR_ATOMIC_H 1
#include <bits/atomic_base.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @addtogroup pointer_abstractions
* @{
*/
/// @relates shared_ptr @{
/// @cond undocumented
struct _Sp_locker
{
_Sp_locker(const _Sp_locker&) = delete;
_Sp_locker& operator=(const _Sp_locker&) = delete;
#ifdef __GTHREADS
explicit
_Sp_locker(const void*) noexcept;
_Sp_locker(const void*, const void*) noexcept;
~_Sp_locker();
private:
unsigned char _M_key1;
unsigned char _M_key2;
#else
explicit _Sp_locker(const void*, const void* = nullptr) { }
#endif
};
/// @endcond
/**
* @brief Report whether shared_ptr atomic operations are lock-free.
* @param __p A non-null pointer to a shared_ptr object.
* @return True if atomic access to @c *__p is lock-free, false otherwise.
* @{
*/
template<typename _Tp, _Lock_policy _Lp>
inline bool
atomic_is_lock_free(const __shared_ptr<_Tp, _Lp>* __p)
{
#ifdef __GTHREADS
return __gthread_active_p() == 0;
#else
return true;
#endif
}
template<typename _Tp>
inline bool
atomic_is_lock_free(const shared_ptr<_Tp>* __p)
{ return std::atomic_is_lock_free<_Tp, __default_lock_policy>(__p); }
/// @}
/**
* @brief Atomic load for shared_ptr objects.
* @param __p A non-null pointer to a shared_ptr object.
* @return @c *__p
*
* The memory order shall not be @c memory_order_release or
* @c memory_order_acq_rel.
* @{
*/
template<typename _Tp>
inline shared_ptr<_Tp>
atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order)
{
_Sp_locker __lock{__p};
return *__p;
}
template<typename _Tp>
inline shared_ptr<_Tp>
atomic_load(const shared_ptr<_Tp>* __p)
{ return std::atomic_load_explicit(__p, memory_order_seq_cst); }
template<typename _Tp, _Lock_policy _Lp>
inline __shared_ptr<_Tp, _Lp>
atomic_load_explicit(const __shared_ptr<_Tp, _Lp>* __p, memory_order)
{
_Sp_locker __lock{__p};
return *__p;
}
template<typename _Tp, _Lock_policy _Lp>
inline __shared_ptr<_Tp, _Lp>
atomic_load(const __shared_ptr<_Tp, _Lp>* __p)
{ return std::atomic_load_explicit(__p, memory_order_seq_cst); }
/// @}
/**
* @brief Atomic store for shared_ptr objects.
* @param __p A non-null pointer to a shared_ptr object.
* @param __r The value to store.
*
* The memory order shall not be @c memory_order_acquire or
* @c memory_order_acq_rel.
* @{
*/
template<typename _Tp>
inline void
atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r,
memory_order)
{
_Sp_locker __lock{__p};
__p->swap(__r); // use swap so that **__p not destroyed while lock held
}
template<typename _Tp>
inline void
atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
{ std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }
template<typename _Tp, _Lock_policy _Lp>
inline void
atomic_store_explicit(__shared_ptr<_Tp, _Lp>* __p,
__shared_ptr<_Tp, _Lp> __r,
memory_order)
{
_Sp_locker __lock{__p};
__p->swap(__r); // use swap so that **__p not destroyed while lock held
}
template<typename _Tp, _Lock_policy _Lp>
inline void
atomic_store(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r)
{ std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }
/// @}
/**
* @brief Atomic exchange for shared_ptr objects.
* @param __p A non-null pointer to a shared_ptr object.
* @param __r New value to store in @c *__p.
* @return The original value of @c *__p
* @{
*/
template<typename _Tp>
inline shared_ptr<_Tp>
atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r,
memory_order)
{
_Sp_locker __lock{__p};
__p->swap(__r);
return __r;
}
template<typename _Tp>
inline shared_ptr<_Tp>
atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
{
return std::atomic_exchange_explicit(__p, std::move(__r),
memory_order_seq_cst);
}
template<typename _Tp, _Lock_policy _Lp>
inline __shared_ptr<_Tp, _Lp>
atomic_exchange_explicit(__shared_ptr<_Tp, _Lp>* __p,
__shared_ptr<_Tp, _Lp> __r,
memory_order)
{
_Sp_locker __lock{__p};
__p->swap(__r);
return __r;
}
template<typename _Tp, _Lock_policy _Lp>
inline __shared_ptr<_Tp, _Lp>
atomic_exchange(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r)
{
return std::atomic_exchange_explicit(__p, std::move(__r),
memory_order_seq_cst);
}
/// @}
/**
* @brief Atomic compare-and-swap for shared_ptr objects.
* @param __p A non-null pointer to a shared_ptr object.
* @param __v A non-null pointer to a shared_ptr object.
* @param __w A non-null pointer to a shared_ptr object.
* @return True if @c *__p was equivalent to @c *__v, false otherwise.
*
* The memory order for failure shall not be @c memory_order_release or
* @c memory_order_acq_rel, or stronger than the memory order for success.
* @{
*/
template<typename _Tp>
bool
atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p,
shared_ptr<_Tp>* __v,
shared_ptr<_Tp> __w,
memory_order,
memory_order)
{
shared_ptr<_Tp> __x; // goes out of scope after __lock
_Sp_locker __lock{__p, __v};
owner_less<shared_ptr<_Tp>> __less;
if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p))
{
__x = std::move(*__p);
*__p = std::move(__w);
return true;
}
__x = std::move(*__v);
*__v = *__p;
return false;
}
template<typename _Tp>
inline bool
atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
shared_ptr<_Tp> __w)
{
return std::atomic_compare_exchange_strong_explicit(__p, __v,
std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
}
template<typename _Tp>
inline bool
atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p,
shared_ptr<_Tp>* __v,
shared_ptr<_Tp> __w,
memory_order __success,
memory_order __failure)
{
return std::atomic_compare_exchange_strong_explicit(__p, __v,
std::move(__w), __success, __failure);
}
template<typename _Tp>
inline bool
atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
shared_ptr<_Tp> __w)
{
return std::atomic_compare_exchange_weak_explicit(__p, __v,
std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
}
template<typename _Tp, _Lock_policy _Lp>
bool
atomic_compare_exchange_strong_explicit(__shared_ptr<_Tp, _Lp>* __p,
__shared_ptr<_Tp, _Lp>* __v,
__shared_ptr<_Tp, _Lp> __w,
memory_order,
memory_order)
{
__shared_ptr<_Tp, _Lp> __x; // goes out of scope after __lock
_Sp_locker __lock{__p, __v};
owner_less<__shared_ptr<_Tp, _Lp>> __less;
if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p))
{
__x = std::move(*__p);
*__p = std::move(__w);
return true;
}
__x = std::move(*__v);
*__v = *__p;
return false;
}
template<typename _Tp, _Lock_policy _Lp>
inline bool
atomic_compare_exchange_strong(__shared_ptr<_Tp, _Lp>* __p,
__shared_ptr<_Tp, _Lp>* __v,
__shared_ptr<_Tp, _Lp> __w)
{
return std::atomic_compare_exchange_strong_explicit(__p, __v,
std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
}
template<typename _Tp, _Lock_policy _Lp>
inline bool
atomic_compare_exchange_weak_explicit(__shared_ptr<_Tp, _Lp>* __p,
__shared_ptr<_Tp, _Lp>* __v,
__shared_ptr<_Tp, _Lp> __w,
memory_order __success,
memory_order __failure)
{
return std::atomic_compare_exchange_strong_explicit(__p, __v,
std::move(__w), __success, __failure);
}
template<typename _Tp, _Lock_policy _Lp>
inline bool
atomic_compare_exchange_weak(__shared_ptr<_Tp, _Lp>* __p,
__shared_ptr<_Tp, _Lp>* __v,
__shared_ptr<_Tp, _Lp> __w)
{
return std::atomic_compare_exchange_weak_explicit(__p, __v,
std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
}
/// @}
/// @} relates shared_ptr
/// @} group pointer_abstractions
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif // _SHARED_PTR_ATOMIC_H
atomic_base.h
std::shared_ptr::atomic_exchange_explicit
shared_ptr< _Tp > atomic_exchange_explicit(shared_ptr< _Tp > *__p, shared_ptr< _Tp > __r, memory_order)
Atomic exchange for shared_ptr objects.
Definition: shared_ptr_atomic.h:176
std::shared_ptr::atomic_compare_exchange_strong_explicit
bool atomic_compare_exchange_strong_explicit(shared_ptr< _Tp > *__p, shared_ptr< _Tp > *__v, shared_ptr< _Tp > __w, memory_order, memory_order)
Atomic compare-and-swap for shared_ptr objects.
Definition: shared_ptr_atomic.h:225
std::shared_ptr::atomic_store_explicit
void atomic_store_explicit(shared_ptr< _Tp > *__p, shared_ptr< _Tp > __r, memory_order)
Atomic store for shared_ptr objects.
Definition: shared_ptr_atomic.h:139
std::shared_ptr::atomic_is_lock_free
bool atomic_is_lock_free(const __shared_ptr< _Tp, _Lp > *__p)
Report whether shared_ptr atomic operations are lock-free.
Definition: shared_ptr_atomic.h:76
std::shared_ptr::swap
void swap(shared_ptr< _Tp > &__a, shared_ptr< _Tp > &__b) noexcept
Swap overload for shared_ptr.
Definition: bits/shared_ptr.h:574
std::shared_ptr::atomic_load_explicit
shared_ptr< _Tp > atomic_load_explicit(const shared_ptr< _Tp > *__p, memory_order)
Atomic load for shared_ptr objects.
Definition: shared_ptr_atomic.h:103
std::move
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:104
std::memory_order
memory_order
Enumeration for memory_order.
Definition: atomic_base.h:79
std
ISO C++ entities toplevel namespace is std.
std::shared_ptr
A smart pointer with reference-counted copy semantics.
Definition: bits/shared_ptr.h:123
std::owner_less
Primary template owner_less.
Definition: bits/shared_ptr.h:769