experimental/memory_resource
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// <experimental/memory_resource> -*- C++ -*-
// Copyright (C) 2015-2021 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 experimental/memory_resource
* This is a TS C++ Library header.
* @ingroup libfund-ts
*/
#ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
#define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1
#pragma GCC system_header
#if __cplusplus >= 201402L
#include <memory> // align, uses_allocator, __uses_alloc
#include <experimental/utility> // pair, experimental::erased_type
#include <tuple> // tuple, forward_as_tuple
#include <atomic> // atomic
#include <new> // placement new
#include <cstddef> // max_align_t
#include <ext/new_allocator.h>
#include <debug/assertions.h>
/// @cond
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp> class malloc_allocator;
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace __gnu_cxx
/// @endcond
namespace std {
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace experimental {
inline namespace fundamentals_v2 {
namespace pmr {
#define __cpp_lib_experimental_memory_resources 201402L
// Standard memory resources
// 8.5 Class memory_resource
class memory_resource;
// 8.6 Class template polymorphic_allocator
template<typename _Tp>
class polymorphic_allocator;
template<typename _Alloc, typename _Resource = memory_resource>
class __resource_adaptor_imp;
// 8.7 Alias template resource_adaptor
template<typename _Alloc>
using resource_adaptor = __resource_adaptor_imp<
typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
// 8.8 Global memory resources
memory_resource* new_delete_resource() noexcept;
memory_resource* null_memory_resource() noexcept;
memory_resource* get_default_resource() noexcept;
memory_resource* set_default_resource(memory_resource* __r) noexcept;
// TODO 8.9 Pool resource classes
class memory_resource
{
static constexpr size_t _S_max_align = alignof(max_align_t);
public:
memory_resource() = default;
memory_resource(const memory_resource&) = default;
virtual ~memory_resource() = default;
memory_resource& operator=(const memory_resource&) = default;
_GLIBCXX_NODISCARD 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); }
template<typename _Tp>
class polymorphic_allocator
{
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;
_GLIBCXX_NODISCARD _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)
{
std::__uses_allocator_construct(this->resource(), __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 =
std::__use_alloc<_Tp1, memory_resource*, _Args1...>(__resource);
auto __y_use_tag =
std::__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,
std::forward_as_tuple(std::forward<_Up>(__x)),
std::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,
std::forward_as_tuple(__pr.first),
std::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,
std::forward_as_tuple(std::forward<_Up>(__pr.first)),
std::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:
using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
using __uses_alloc2_ = __uses_alloc2<memory_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_ __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); }
/// @cond undocumented
class __resource_adaptor_common
{
template<typename, typename> friend class __resource_adaptor_imp;
struct _AlignMgr
{
_AlignMgr(size_t __nbytes, size_t __align)
: _M_nbytes(__nbytes), _M_align(__align)
{ }
// Total size that needs to be allocated.
size_t
_M_alloc_size() const { return _M_buf_size() + _M_token_size(); }
void*
_M_adjust(void* __ptr) const
{
const auto __orig_ptr = static_cast<char*>(__ptr);
size_t __space = _M_buf_size();
// Align the pointer within the buffer:
std::align(_M_align, _M_nbytes, __ptr, __space);
const auto __aligned_ptr = static_cast<char*>(__ptr);
const auto __token_size = _M_token_size();
// Store token immediately after the aligned block:
char* const __end = __aligned_ptr + _M_nbytes;
if (__token_size == 1)
_S_write<unsigned char>(__end, __aligned_ptr - __orig_ptr);
else if (__token_size == sizeof(short))
_S_write<unsigned short>(__end, __aligned_ptr - __orig_ptr);
else if (__token_size == sizeof(int) && sizeof(int) < sizeof(char*))
_S_write<unsigned int>(__end, __aligned_ptr - __orig_ptr);
else // (__token_size == sizeof(char*))
// Just store the original pointer:
_S_write<char*>(__end, __orig_ptr);
return __aligned_ptr;
}
char*
_M_unadjust(char* __ptr) const
{
const char* const __end = __ptr + _M_nbytes;
char* __orig_ptr;
const auto __token_size = _M_token_size();
// Read the token and restore the original pointer:
if (__token_size == 1)
__orig_ptr = __ptr - _S_read<unsigned char>(__end);
else if (__token_size == sizeof(short))
__orig_ptr = __ptr - _S_read<unsigned short>(__end);
else if (__token_size == sizeof(int)
&& sizeof(int) < sizeof(char*))
__orig_ptr = __ptr - _S_read<unsigned int>(__end);
else // (__token_size == sizeof(char*))
__orig_ptr = _S_read<char*>(__end);
// The adjustment is always less than the requested alignment,
// so if that isn't true now then either the wrong size was passed
// to deallocate or the token was overwritten by a buffer overflow:
__glibcxx_assert(static_cast<size_t>(__ptr - __orig_ptr) < _M_align);
return __orig_ptr;
}
private:
size_t _M_nbytes;
size_t _M_align;
// Number of bytes needed to fit block of given size and alignment.
size_t
_M_buf_size() const { return _M_nbytes + _M_align - 1; }
// Number of additional bytes needed to write the token.
int
_M_token_size() const
{
if (_M_align <= (1ul << __CHAR_BIT__))
return 1;
if (_M_align <= (1ul << (sizeof(short) * __CHAR_BIT__)))
return sizeof(short);
if (_M_align <= (1ull << (sizeof(int) * __CHAR_BIT__)))
return sizeof(int);
return sizeof(char*);
}
template<typename _Tp>
static void
_S_write(void* __to, _Tp __val)
{ __builtin_memcpy(__to, &__val, sizeof(_Tp)); }
template<typename _Tp>
static _Tp
_S_read(const void* __from)
{
_Tp __val;
__builtin_memcpy(&__val, __from, sizeof(_Tp));
return __val;
}
};
};
/// @endcond
// 8.7.1 __resource_adaptor_imp
template<typename _Alloc, typename _Resource>
class __resource_adaptor_imp
: public _Resource, private __resource_adaptor_common
{
using memory_resource = _Resource;
static_assert(is_same<char,
typename allocator_traits<_Alloc>::value_type>::value,
"Allocator's value_type is char");
static_assert(is_same<char*,
typename allocator_traits<_Alloc>::pointer>::value,
"Allocator's pointer type is value_type*");
static_assert(is_same<const char*,
typename allocator_traits<_Alloc>::const_pointer>::value,
"Allocator's const_pointer type is value_type const*");
static_assert(is_same<void*,
typename allocator_traits<_Alloc>::void_pointer>::value,
"Allocator's void_pointer type is void*");
static_assert(is_same<const void*,
typename allocator_traits<_Alloc>::const_void_pointer>::value,
"Allocator's const_void_pointer type is void const*");
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 noexcept { return _M_alloc; }
protected:
virtual void*
do_allocate(size_t __bytes, size_t __alignment) override
{
// Cannot use max_align_t on 32-bit Solaris x86, see PR libstdc++/77691
#if ! ((defined __sun__ || defined __VXWORKS__) && defined __i386__)
if (__alignment == alignof(max_align_t))
return _M_allocate<alignof(max_align_t)>(__bytes);
#endif
switch (__alignment)
{
case 1:
return _M_alloc.allocate(__bytes);
case 2:
return _M_allocate<2>(__bytes);
case 4:
return _M_allocate<4>(__bytes);
case 8:
return _M_allocate<8>(__bytes);
}
const _AlignMgr __mgr(__bytes, __alignment);
// Assume _M_alloc returns 1-byte aligned memory, so allocate enough
// space to fit a block of the right size and alignment, plus some
// extra bytes to store a token for retrieving the original pointer.
return __mgr._M_adjust(_M_alloc.allocate(__mgr._M_alloc_size()));
}
virtual void
do_deallocate(void* __ptr, size_t __bytes, size_t __alignment) noexcept
override
{
#if ! ((defined __sun__ || defined __VXWORKS__) && defined __i386__)
if (__alignment == alignof(max_align_t))
return (void) _M_deallocate<alignof(max_align_t)>(__ptr, __bytes);
#endif
switch (__alignment)
{
case 1:
return (void) _M_alloc.deallocate((char*)__ptr, __bytes);
case 2:
return (void) _M_deallocate<2>(__ptr, __bytes);
case 4:
return (void) _M_deallocate<4>(__ptr, __bytes);
case 8:
return (void) _M_deallocate<8>(__ptr, __bytes);
}
const _AlignMgr __mgr(__bytes, __alignment);
// Use the stored token to retrieve the original pointer.
_M_alloc.deallocate(__mgr._M_unadjust((char*)__ptr),
__mgr._M_alloc_size());
}
virtual bool
do_is_equal(const memory_resource& __other) const noexcept override
{
if (auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other))
return _M_alloc == __p->_M_alloc;
return false;
}
private:
template<size_t _Num>
struct _Aligned_type { alignas(_Num) char __c[_Num]; };
// Rebind the allocator to the specified type and use it to allocate.
template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
void*
_M_allocate(size_t __bytes)
{
typename allocator_traits<_Alloc>::template
rebind_alloc<_Tp> __a2(_M_alloc);
const size_t __n = (__bytes + _Num - 1) / _Num;
return __a2.allocate(__n);
}
// Rebind the allocator to the specified type and use it to deallocate.
template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
void
_M_deallocate(void* __ptr, size_t __bytes) noexcept
{
typename allocator_traits<_Alloc>::template
rebind_alloc<_Tp> __a2(_M_alloc);
const size_t __n = (__bytes + _Num - 1) / _Num;
__a2.deallocate((_Tp*)__ptr, __n);
}
_Alloc _M_alloc{};
};
// Global memory resources
inline memory_resource*
new_delete_resource() noexcept
{
using type = resource_adaptor<__gnu_cxx::new_allocator<char>>;
alignas(type) static unsigned char __buf[sizeof(type)];
static type* __r = new(__buf) type;
return __r;
}
inline memory_resource*
null_memory_resource() noexcept
{
class type final : public memory_resource
{
void*
do_allocate(size_t, size_t) override
{ std::__throw_bad_alloc(); }
void
do_deallocate(void*, size_t, size_t) noexcept override
{ }
bool
do_is_equal(const memory_resource& __other) const noexcept override
{ return this == &__other; }
};
alignas(type) static unsigned char __buf[sizeof(type)];
static type* __r = new(__buf) type;
return __r;
}
// The default memory resource
/// @cond undocumented
inline std::atomic<memory_resource*>&
__get_default_resource()
{
using type = atomic<memory_resource*>;
alignas(type) static unsigned char __buf[sizeof(type)];
static type* __r = new(__buf) type(new_delete_resource());
return *__r;
}
/// @endcond
/// Get the current default resource.
inline memory_resource*
get_default_resource() noexcept
{ return __get_default_resource().load(); }
/// Change the default resource and return the previous one.
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 // C++14
#endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE