memory_resource
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// <experimental/memory_resource> -*- C++ -*-
// Copyright (C) 2015-2018 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 experimental/memory_resource
* This is a TS C++ Library header.
*/
#ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
#define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1
#include <memory>
#include <new>
#include <atomic>
#include <cstddef>
#include <bits/alloc_traits.h>
#include <experimental/bits/lfts_config.h>
namespace std {
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace experimental {
inline namespace fundamentals_v2 {
namespace pmr {
#define __cpp_lib_experimental_memory_resources 201402L
class memory_resource;
template <typename _Tp>
class polymorphic_allocator;
template <typename _Alloc>
class __resource_adaptor_imp;
template <typename _Alloc>
using resource_adaptor = __resource_adaptor_imp<
typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
template <typename _Tp>
struct __uses_allocator_construction_helper;
// Global memory resources
memory_resource* new_delete_resource() noexcept;
memory_resource* null_memory_resource() noexcept;
// The default memory resource
memory_resource* get_default_resource() noexcept;
memory_resource* set_default_resource(memory_resource* __r) noexcept;
// Standard memory resources
// 8.5 Class memory_resource
class memory_resource
{
protected:
static constexpr size_t _S_max_align = alignof(max_align_t);
public:
virtual ~memory_resource() { }
void*
allocate(size_t __bytes, size_t __alignment = _S_max_align)
{ return do_allocate(__bytes, __alignment); }
void
deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
{ return do_deallocate(__p, __bytes, __alignment); }
bool
is_equal(const memory_resource& __other) const noexcept
{ return do_is_equal(__other); }
protected:
virtual void*
do_allocate(size_t __bytes, size_t __alignment) = 0;
virtual void
do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
virtual bool
do_is_equal(const memory_resource& __other) const noexcept = 0;
};
inline bool
operator==(const memory_resource& __a,
const memory_resource& __b) noexcept
{ return &__a == &__b || __a.is_equal(__b); }
inline bool
operator!=(const memory_resource& __a,
const memory_resource& __b) noexcept
{ return !(__a == __b); }
// 8.6 Class template polymorphic_allocator
template <class _Tp>
class polymorphic_allocator
{
using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
using __uses_alloc2_ = __uses_alloc2<memory_resource*>;
template<typename _Tp1, typename... _Args>
void
_M_construct(__uses_alloc0, _Tp1* __p, _Args&&... __args)
{ ::new(__p) _Tp1(std::forward<_Args>(__args)...); }
template<typename _Tp1, typename... _Args>
void
_M_construct(__uses_alloc1_, _Tp1* __p, _Args&&... __args)
{ ::new(__p) _Tp1(allocator_arg, this->resource(),
std::forward<_Args>(__args)...); }
template<typename _Tp1, typename... _Args>
void
_M_construct(__uses_alloc2_, _Tp1* __p, _Args&&... __args)
{ ::new(__p) _Tp1(std::forward<_Args>(__args)...,
this->resource()); }
public:
using value_type = _Tp;
polymorphic_allocator() noexcept
: _M_resource(get_default_resource())
{ }
polymorphic_allocator(memory_resource* __r)
: _M_resource(__r)
{ _GLIBCXX_DEBUG_ASSERT(__r); }
polymorphic_allocator(const polymorphic_allocator& __other) = default;
template <typename _Up>
polymorphic_allocator(const polymorphic_allocator<_Up>&
__other) noexcept
: _M_resource(__other.resource())
{ }
polymorphic_allocator&
operator=(const polymorphic_allocator& __rhs) = default;
_Tp* allocate(size_t __n)
{ return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
alignof(_Tp))); }
void deallocate(_Tp* __p, size_t __n)
{ _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
template <typename _Tp1, typename... _Args> //used here
void construct(_Tp1* __p, _Args&&... __args)
{
memory_resource* const __resource = this->resource();
auto __use_tag
= __use_alloc<_Tp1, memory_resource*, _Args...>(__resource);
_M_construct(__use_tag, __p, std::forward<_Args>(__args)...);
}
// Specializations for pair using piecewise construction
template <typename _Tp1, typename _Tp2,
typename... _Args1, typename... _Args2>
void construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
tuple<_Args1...> __x,
tuple<_Args2...> __y)
{
memory_resource* const __resource = this->resource();
auto __x_use_tag =
__use_alloc<_Tp1, memory_resource*, _Args1...>(__resource);
auto __y_use_tag =
__use_alloc<_Tp2, memory_resource*, _Args2...>(__resource);
::new(__p) std::pair<_Tp1, _Tp2>(piecewise_construct,
_M_construct_p(__x_use_tag, __x),
_M_construct_p(__y_use_tag, __y));
}
template <typename _Tp1, typename _Tp2>
void construct(pair<_Tp1,_Tp2>* __p)
{ this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
void construct(pair<_Tp1,_Tp2>* __p, _Up&& __x, _Vp&& __y)
{ this->construct(__p, piecewise_construct,
forward_as_tuple(std::forward<_Up>(__x)),
forward_as_tuple(std::forward<_Vp>(__y))); }
template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
void construct(pair<_Tp1,_Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
{ this->construct(__p, piecewise_construct, forward_as_tuple(__pr.first),
forward_as_tuple(__pr.second)); }
template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
void construct(pair<_Tp1,_Tp2>* __p, pair<_Up, _Vp>&& __pr)
{ this->construct(__p, piecewise_construct,
forward_as_tuple(std::forward<_Up>(__pr.first)),
forward_as_tuple(std::forward<_Vp>(__pr.second))); }
template <typename _Up>
void destroy(_Up* __p)
{ __p->~_Up(); }
// Return a default-constructed allocator (no allocator propagation)
polymorphic_allocator select_on_container_copy_construction() const
{ return polymorphic_allocator(); }
memory_resource* resource() const
{ return _M_resource; }
private:
template<typename _Tuple>
_Tuple&&
_M_construct_p(__uses_alloc0, _Tuple& __t)
{ return std::move(__t); }
template<typename... _Args>
decltype(auto)
_M_construct_p(__uses_alloc1_ __ua, tuple<_Args...>& __t)
{ return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
std::move(__t)); }
template<typename... _Args>
decltype(auto)
_M_construct_p(__uses_alloc2_ __ua, tuple<_Args...>& __t)
{ return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }
memory_resource* _M_resource;
};
template <class _Tp1, class _Tp2>
bool operator==(const polymorphic_allocator<_Tp1>& __a,
const polymorphic_allocator<_Tp2>& __b) noexcept
{ return *__a.resource() == *__b.resource(); }
template <class _Tp1, class _Tp2>
bool operator!=(const polymorphic_allocator<_Tp1>& __a,
const polymorphic_allocator<_Tp2>& __b) noexcept
{ return !(__a == __b); }
// 8.7.1 __resource_adaptor_imp
template <typename _Alloc>
class __resource_adaptor_imp : public memory_resource
{
public:
using allocator_type = _Alloc;
__resource_adaptor_imp() = default;
__resource_adaptor_imp(const __resource_adaptor_imp&) = default;
__resource_adaptor_imp(__resource_adaptor_imp&&) = default;
explicit __resource_adaptor_imp(const _Alloc& __a2)
: _M_alloc(__a2)
{ }
explicit __resource_adaptor_imp(_Alloc&& __a2)
: _M_alloc(std::move(__a2))
{ }
__resource_adaptor_imp&
operator=(const __resource_adaptor_imp&) = default;
allocator_type get_allocator() const { return _M_alloc; }
protected:
virtual void*
do_allocate(size_t __bytes, size_t __alignment)
{
using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
size_t __new_size = _S_aligned_size(__bytes,
_S_supported(__alignment) ?
__alignment : _S_max_align);
return _Aligned_alloc(_M_alloc).allocate(__new_size);
}
virtual void
do_deallocate(void* __p, size_t __bytes, size_t __alignment)
{
using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
size_t __new_size = _S_aligned_size(__bytes,
_S_supported(__alignment) ?
__alignment : _S_max_align);
using _Ptr = typename allocator_traits<_Aligned_alloc>::pointer;
_Aligned_alloc(_M_alloc).deallocate(static_cast<_Ptr>(__p),
__new_size);
}
virtual bool
do_is_equal(const memory_resource& __other) const noexcept
{
auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other);
return __p ? (_M_alloc == __p->_M_alloc) : false;
}
private:
// Calculate Aligned Size
// Returns a size that is larger than or equal to __size and divisible
// by __alignment, where __alignment is required to be the power of 2.
static size_t
_S_aligned_size(size_t __size, size_t __alignment)
{ return ((__size - 1)|(__alignment - 1)) + 1; }
// Determine whether alignment meets one of those preconditions:
// 1. Equals to Zero
// 2. Is power of two
static bool
_S_supported (size_t __x)
{ return ((__x != 0) && !(__x & (__x - 1))); }
_Alloc _M_alloc;
};
// Global memory resources
inline std::atomic<memory_resource*>&
__get_default_resource()
{
static atomic<memory_resource*> _S_default_resource(new_delete_resource());
return _S_default_resource;
}
inline memory_resource*
new_delete_resource() noexcept
{
static resource_adaptor<std::allocator<char>> __r;
return static_cast<memory_resource*>(&__r);
}
template <typename _Alloc>
class __null_memory_resource : private memory_resource
{
protected:
void*
do_allocate(size_t, size_t)
{ std::__throw_bad_alloc(); }
void
do_deallocate(void*, size_t, size_t) noexcept
{ }
bool
do_is_equal(const memory_resource& __other) const noexcept
{ return this == &__other; }
friend memory_resource* null_memory_resource() noexcept;
};
inline memory_resource*
null_memory_resource() noexcept
{
static __null_memory_resource<void> __r;
return static_cast<memory_resource*>(&__r);
}
// The default memory resource
inline memory_resource*
get_default_resource() noexcept
{ return __get_default_resource().load(); }
inline memory_resource*
set_default_resource(memory_resource* __r) noexcept
{
if (__r == nullptr)
__r = new_delete_resource();
return __get_default_resource().exchange(__r);
}
} // namespace pmr
} // namespace fundamentals_v2
} // namespace experimental
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif
std::atomic
Generic atomic type, primary class template.
Definition: atomic:58
memory
atomic
alloc_traits.h
std::pair::second
_T2 second
first is a copy of the first object
Definition: stl_pair.h:204
std::pair::first
_T1 first
second_type is the second bound type
Definition: stl_pair.h:203
lfts_config.h
std::piecewise_construct
_GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
std
ISO C++ entities toplevel namespace is std.
new
std::tuple_cat
constexpr auto tuple_cat(_Tpls &&... __tpls) -> typename __tuple_cat_result< _Tpls... >::__type
tuple_cat
Definition: tuple:1591
cstddef
std::allocator_traits::pointer
__detected_or_t< value_type *, __pointer, _Alloc > pointer
The allocator&#39;s pointer type.
Definition: bits/alloc_traits.h:95
std::pair
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:198