extptr_allocator.h
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// <extptr_allocator.h> -*- C++ -*-
// Copyright (C) 2008-2022 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 ext/extptr_allocator.h
* This file is a GNU extension to the Standard C++ Library.
*
* @author Bob Walters
*
* An example allocator which uses an alternative pointer type from
* bits/pointer.h. Supports test cases which confirm container support
* for alternative pointers.
*/
#ifndef _EXTPTR_ALLOCATOR_H
#define _EXTPTR_ALLOCATOR_H 1
#include <memory>
#include <ext/numeric_traits.h>
#include <ext/pointer.h>
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @brief An example allocator which uses a non-standard pointer type.
* @ingroup allocators
*
* This allocator specifies that containers use a 'relative pointer' as it's
* pointer type. (See ext/pointer.h) Memory allocation in this example
* is still performed using std::allocator.
*/
template<typename _Tp>
class _ExtPtr_allocator
{
public:
typedef std::size_t size_type;
typedef std::ptrdiff_t difference_type;
// Note the non-standard pointer types.
typedef _Pointer_adapter<_Relative_pointer_impl<_Tp> > pointer;
typedef _Pointer_adapter<_Relative_pointer_impl<const _Tp> >
const_pointer;
typedef _Tp& reference;
typedef const _Tp& const_reference;
typedef _Tp value_type;
template<typename _Up>
struct rebind
{ typedef _ExtPtr_allocator<_Up> other; };
_ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
: _M_real_alloc() { }
_ExtPtr_allocator(const _ExtPtr_allocator& __rarg) _GLIBCXX_USE_NOEXCEPT
: _M_real_alloc(__rarg._M_real_alloc) { }
template<typename _Up>
_ExtPtr_allocator(const _ExtPtr_allocator<_Up>& __rarg)
_GLIBCXX_USE_NOEXCEPT
: _M_real_alloc(__rarg._M_getUnderlyingImp()) { }
~_ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
{ }
pointer address(reference __x) const _GLIBCXX_NOEXCEPT
{ return std::__addressof(__x); }
const_pointer address(const_reference __x) const _GLIBCXX_NOEXCEPT
{ return std::__addressof(__x); }
_GLIBCXX_NODISCARD pointer allocate(size_type __n, const void* = 0)
{ return _M_real_alloc.allocate(__n); }
void deallocate(pointer __p, size_type __n)
{ _M_real_alloc.deallocate(__p.get(), __n); }
size_type max_size() const _GLIBCXX_USE_NOEXCEPT
{ return __numeric_traits<size_type>::__max / sizeof(_Tp); }
#if __cplusplus >= 201103L
template<typename _Up, typename... _Args>
void
construct(_Up* __p, _Args&&... __args)
{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
template<typename... _Args>
void
construct(pointer __p, _Args&&... __args)
{ construct(__p.get(), std::forward<_Args>(__args)...); }
template<typename _Up>
void
destroy(_Up* __p)
{ __p->~_Up(); }
void destroy(pointer __p)
{ destroy(__p.get()); }
#else
void construct(pointer __p, const _Tp& __val)
{ ::new(__p.get()) _Tp(__val); }
void destroy(pointer __p)
{ __p->~_Tp(); }
#endif
template<typename _Up>
inline bool
operator==(const _ExtPtr_allocator<_Up>& __rarg) const
{ return _M_real_alloc == __rarg._M_getUnderlyingImp(); }
inline bool
operator==(const _ExtPtr_allocator& __rarg) const
{ return _M_real_alloc == __rarg._M_real_alloc; }
#if __cpp_impl_three_way_comparison < 201907L
template<typename _Up>
inline bool
operator!=(const _ExtPtr_allocator<_Up>& __rarg) const
{ return _M_real_alloc != __rarg._M_getUnderlyingImp(); }
inline bool
operator!=(const _ExtPtr_allocator& __rarg) const
{ return _M_real_alloc != __rarg._M_real_alloc; }
#endif
template<typename _Up>
inline friend void
swap(_ExtPtr_allocator<_Up>&, _ExtPtr_allocator<_Up>&);
// A method specific to this implementation.
const std::allocator<_Tp>&
_M_getUnderlyingImp() const
{ return _M_real_alloc; }
private:
std::allocator<_Tp> _M_real_alloc;
};
// _ExtPtr_allocator<void> specialization.
template<>
class _ExtPtr_allocator<void>
{
public:
typedef std::size_t size_type;
typedef std::ptrdiff_t difference_type;
typedef void value_type;
// Note the non-standard pointer types
typedef _Pointer_adapter<_Relative_pointer_impl<void> > pointer;
typedef _Pointer_adapter<_Relative_pointer_impl<const void> >
const_pointer;
_ExtPtr_allocator() { }
template<typename _Up>
_ExtPtr_allocator(const _ExtPtr_allocator<_Up>&) { }
template<typename _Up>
struct rebind
{ typedef _ExtPtr_allocator<_Up> other; };
private:
std::allocator<void> _M_real_alloc;
};
template<typename _Tp>
inline void
swap(_ExtPtr_allocator<_Tp>& __larg, _ExtPtr_allocator<_Tp>& __rarg)
{
std::allocator<_Tp> __tmp( __rarg._M_real_alloc );
__rarg._M_real_alloc = __larg._M_real_alloc;
__larg._M_real_alloc = __tmp;
}
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif /* _EXTPTR_ALLOCATOR_H */
pointer.h
std::__addressof
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition move.h:49
std::forward
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition move.h:77
__gnu_cxx
GNU extensions for public use.
std::allocator
The standard allocator, as per C++03 [20.4.1].
Definition allocator.h:130
__gnu_cxx::other
__gnu_cxx::_ExtPtr_allocator
An example allocator which uses a non-standard pointer type.
Definition extptr_allocator.h:57
__gnu_cxx::_Pointer_adapter
Definition pointer.h:273
numeric_traits.h
memory