Hi, According to <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4335.html#memory.smartptr>
Here is my implementation of [8.2] Extend shared_ptr to support arrays [8.3] Type-Erased allocator Thanks, Fan
#ifndef _GLIBCXX_MEMORY_RESOURCE
#define _GLIBCXX_MEMORY_RESOURCE 1
#include <memory>
#include <new>
#include <atomic>
#include <cstddef>
#include <bits/alloc_traits.h>
namespace std {
namespace experimental {
inline namespace fundamentals_v1 {
namespace pmr {
// Decleartion
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>>;
// 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
{
static constexpr size_t __max_align = alignof(max_align_t);
public:
virtual ~memory_resource() { }
void* allocate(size_t __bytes,
size_t __alignment = __max_align)
{ return do_allocate(__bytes, __alignment); }
void deallocate(void* __p, size_t __bytes,
size_t __alignment = __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;
private:
friend memory_resource* set_default_resource(memory_resource*);
friend memory_resource* get_default_resource();
static std::atomic<memory_resource*> s_default_resource;
};
bool operator==(const memory_resource& __a,
const memory_resource& __b) noexcept
{ return &__a == &__b || __a.is_equal(__b); }
bool operator!=(const memory_resource& __a,
const memory_resource& __b) noexcept
{ return !(__a == __b); }
template <typename _Tp>
class __constructor_helper_imp
{
using dont_care_type = bool;
public:
// Construct with no allocator
template <typename... _Args>
__constructor_helper_imp(false_type, _Args&&... __args)
: _M_tp(std::forward<_Args>(__args)...) { }
// Construct with allocator
// 1. uses_allocator == false
// 1.1 no pair construction - ignore allocator
template <typename _Alloc, typename... _Args>
__constructor_helper_imp(allocator_arg_t,
const _Alloc& __a,
false_type,
dont_care_type,
dont_care_type,
_Args&&... __args)
: _M_tp(std::forward<_Args>(__args)...) { }
// 2. uses_allocator == true && prepend allocator argument
template <typename _Alloc, typename... _Args>
__constructor_helper_imp(allocator_arg_t,
const _Alloc& __a,
true_type,
dont_care_type,
true_type,
_Args&&... __args)
: _M_tp(allocator_arg, __a, std::forward<_Args>(__args)...) { }
// 3. uses_allocator == true && append allocator argument
template <typename _Alloc, typename... _Args>
__constructor_helper_imp(allocator_arg_t,
const _Alloc& __a,
true_type,
true_type,
dont_care_type,
_Args&&... __args)
: _M_tp(std::forward<_Args>(__args)..., __a) { }
// 4. ill-formed
template <typename _Alloc, typename... _Args>
__constructor_helper_imp(allocator_arg_t,
const _Alloc& __a,
true_type,
false_type,
false_type,
_Args&&... __args)
: _M_tp(std::forward<_Args>(__args)...)
{
static_assert(sizeof(_Alloc) == 0,
"Type uses an allocator but "
"allocator-aware constructor "
"is missing");
}
private:
_Tp _M_tp;
};
template <typename _Tp>
class __constructor_helper : private __constructor_helper_imp<_Tp>
{
using _Base = __constructor_helper_imp<_Tp>;
public:
template <typename _Alloc, typename... _Args>
__constructor_helper(allocator_arg_t, _Alloc&& __a, _Args&&... __args)
: _Base(allocator_arg, __a,
uses_allocator<_Tp, _Alloc>(),
is_constructible<_Tp, _Args..., _Alloc>(),
is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>(),
std::forward<_Args>(__args)...)
{ }
template <typename... _Args>
__constructor_helper(_Args&&... __args)
: _Base(false_type(), std::forward<_Args>(__args)...)
{ }
};
// 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*>;
public:
using value_type = _Tp;
polymorphic_allocator() noexcept
: _M_resource(get_default_resource())
{ } // used here
polymorphic_allocator(memory_resource* __r)
: _M_resource(__r ? __r : get_default_resource())
{ }
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) // used here
{ 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)
{
using _Ctor_imp = __constructor_helper<_Tp1>;
::new ((void*)__p) _Ctor_imp(allocator_arg,
this->resource(),
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)
{
auto __x_use_tag =
__use_alloc<_Tp1, memory_resource*, _Args1...>(this->resource());
auto __y_use_tag =
__use_alloc<_Tp2, memory_resource*, _Args2...>(this->resource());
using _Ctor_imp = __constructor_helper<pair<_Tp1, _Tp2>>;
::new ((void*)__p) _Ctor_imp(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:
memory_resource* _M_resource;
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_, tuple<_Args...>& __t)
{ return tuple_cat(make_tuple(allocator_arg, this->resources()),
std::move(__t)); }
template<typename... _Args>
decltype(auto)
_M_construct_p(__uses_alloc2_, tuple<_Args...>& __t)
{ return tuple_cat(std::move(__t), make_tuple(this->resources())); }
};
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 = typename _Alloc::template rebind<char>::other;
size_t __new_size = _Aligned_size(__bytes,
_M_supported(__alignment) ?
__alignment : __max_align);
return _Aligned_alloc().allocate(__new_size);
}
virtual void
do_deallocate(void* __p, size_t __bytes, size_t __alignment)
{
using _Aligned_alloc = typename _Alloc::template rebind<char>::other;
size_t __new_size = _Aligned_size(__bytes,
_M_supported(__alignment) ?
__alignment : __max_align);
_Aligned_alloc().deallocate(static_cast<typename
_Aligned_alloc::pointer>(__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
size_t _Aligned_size(size_t __size, size_t __alignment)
{ return ((__size - 1)|(__alignment - 1)) + 1; }
bool _M_supported (size_t __x)
{ return ((__x != 0) && (__x != 0) && !(__x & (__x - 1))); }
_Alloc _M_alloc;
};
// Global memory resources
atomic<memory_resource*> memory_resource::s_default_resource;
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 __bytes, size_t __alignment)
{ std::__throw_bad_alloc(); }
void do_deallocate(void* __p, size_t __bytes, size_t __alignment)
{ }
bool do_is_equal(const memory_resource& __other) const noexcept
{ }
friend memory_resource* null_memory_resource();
};
memory_resource* null_memory_resource() noexcept
{
static __null_memory_resource<void> __r;
return static_cast<memory_resource*>(&__r);
}
// The default memory resource
memory_resource* get_default_resource() noexcept
{
memory_resource *__ret
= memory_resource::s_default_resource.load();
if (__ret == nullptr) { __ret = new_delete_resource(); }
return __ret;
}
memory_resource* set_default_resource(memory_resource* __r) noexcept
{
if ( __r == nullptr)
{ __r = new_delete_resource(); }
memory_resource* __prev = get_default_resource();
memory_resource::s_default_resource.store(__r);
return __prev;
}
}
}
}
}
#endif
shared_ptr_array.patch
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