libstdc++-v3/include/ext/extptr_allocator.h

   1 // <extptr_allocator.h> -*- C++ -*-
   2
   3 // Copyright (C) 2008-2024 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /**
  26  *  @file ext/extptr_allocator.h
  27  *  This file is a GNU extension to the Standard C++ Library.
  28  *
  29  *  @author Bob Walters
  30  *
  31  * An example allocator which uses an alternative pointer type from
  32  * bits/pointer.h.  Supports test cases which confirm container support
  33  * for alternative pointers.
  34  */
  35
  36 #ifndef _EXTPTR_ALLOCATOR_H
  37 #define _EXTPTR_ALLOCATOR_H 1
  38
  39 #include <bits/requires_hosted.h> // GNU extensions are currently omitted
  40
  41 #include <memory>
  42 #include <ext/numeric_traits.h>
  43 #include <ext/pointer.h>
  44
  45 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  46 {
  47 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  48
  49   /**
  50    * @brief An example allocator which uses a non-standard pointer type.
  51    * @ingroup allocators
  52    *
  53    * This allocator specifies that containers use a 'relative pointer' as it's
  54    * pointer type.  (See ext/pointer.h)  Memory allocation in this example
  55    * is still performed using std::allocator.
  56    */
  57   template<typename _Tp>
  58     class _ExtPtr_allocator
  59     {
  60     public:
  61       typedef std::size_t     size_type;
  62       typedef std::ptrdiff_t  difference_type;
  63
  64       // Note the non-standard pointer types.
  65       typedef _Pointer_adapter<_Relative_pointer_impl<_Tp> >       pointer;
  66       typedef _Pointer_adapter<_Relative_pointer_impl<const _Tp> >
  67                                                              const_pointer;
  68
  69       typedef _Tp&       reference;
  70       typedef const _Tp& const_reference;
  71       typedef _Tp        value_type;
  72
  73       template<typename _Up>
  74         struct rebind
  75         { typedef _ExtPtr_allocator<_Up> other; };
  76
  77       _ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
  78       : _M_real_alloc() { }
  79
  80       _ExtPtr_allocator(const _ExtPtr_allocator& __rarg) _GLIBCXX_USE_NOEXCEPT
  81       : _M_real_alloc(__rarg._M_real_alloc) { }
  82
  83       template<typename _Up>
  84         _ExtPtr_allocator(const _ExtPtr_allocator<_Up>& __rarg)
  85         _GLIBCXX_USE_NOEXCEPT
  86         : _M_real_alloc(__rarg._M_getUnderlyingImp()) { }
  87
  88       ~_ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
  89       { }
  90
  91       pointer address(reference __x) const _GLIBCXX_NOEXCEPT
  92       { return std::__addressof(__x); }
  93
  94       const_pointer address(const_reference __x) const _GLIBCXX_NOEXCEPT
  95       { return std::__addressof(__x); }
  96
  97       _GLIBCXX_NODISCARD pointer allocate(size_type __n, const void* = 0)
  98       { return _M_real_alloc.allocate(__n); }
  99
 100       void deallocate(pointer __p, size_type __n)
 101       { _M_real_alloc.deallocate(__p.get(), __n); }
 102
 103       size_type max_size() const _GLIBCXX_USE_NOEXCEPT
 104       { return __numeric_traits<size_type>::__max / sizeof(_Tp); }
 105
 106 #if __cplusplus >= 201103L
 107       template<typename _Up, typename... _Args>
 108         void
 109         construct(_Up* __p, _Args&&... __args)
 110         { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 111
 112       template<typename... _Args>
 113         void
 114         construct(pointer __p, _Args&&... __args)
 115         { construct(__p.get(), std::forward<_Args>(__args)...); }
 116
 117       template<typename _Up>
 118         void
 119         destroy(_Up* __p)
 120         { __p->~_Up(); }
 121
 122       void destroy(pointer __p)
 123       { destroy(__p.get()); }
 124
 125 #else
 126
 127       void construct(pointer __p, const _Tp& __val)
 128       { ::new(__p.get()) _Tp(__val); }
 129
 130       void destroy(pointer __p)
 131       { __p->~_Tp(); }
 132 #endif
 133
 134       template<typename _Up>
 135         inline bool
 136         operator==(const _ExtPtr_allocator<_Up>& __rarg) const
 137         { return _M_real_alloc == __rarg._M_getUnderlyingImp(); }
 138
 139       inline bool
 140       operator==(const _ExtPtr_allocator& __rarg) const
 141       { return _M_real_alloc == __rarg._M_real_alloc; }
 142
 143 #if __cpp_impl_three_way_comparison < 201907L
 144       template<typename _Up>
 145         inline bool
 146         operator!=(const _ExtPtr_allocator<_Up>& __rarg) const
 147         { return _M_real_alloc != __rarg._M_getUnderlyingImp(); }
 148
 149       inline bool
 150       operator!=(const _ExtPtr_allocator& __rarg) const
 151       { return _M_real_alloc != __rarg._M_real_alloc; }
 152 #endif
 153
 154       template<typename _Up>
 155         inline friend void
 156         swap(_ExtPtr_allocator<_Up>&, _ExtPtr_allocator<_Up>&);
 157
 158       // A method specific to this implementation.
 159       const std::allocator<_Tp>&
 160       _M_getUnderlyingImp() const
 161       { return _M_real_alloc; }
 162
 163     private:
 164       std::allocator<_Tp>  _M_real_alloc;
 165     };
 166
 167   // _ExtPtr_allocator<void> specialization.
 168   template<>
 169     class _ExtPtr_allocator<void>
 170     {
 171     public:
 172       typedef std::size_t      size_type;
 173       typedef std::ptrdiff_t   difference_type;
 174       typedef void             value_type;
 175
 176       // Note the non-standard pointer types
 177       typedef _Pointer_adapter<_Relative_pointer_impl<void> >       pointer;
 178       typedef _Pointer_adapter<_Relative_pointer_impl<const void> >
 179                                                               const_pointer;
 180
 181       _ExtPtr_allocator() { }
 182
 183       template<typename _Up>
 184         _ExtPtr_allocator(const _ExtPtr_allocator<_Up>&) { }
 185
 186       template<typename _Up>
 187         struct rebind
 188         { typedef _ExtPtr_allocator<_Up> other; };
 189
 190     private:
 191       std::allocator<void>  _M_real_alloc;
 192     };
 193
 194   template<typename _Tp>
 195     inline void
 196     swap(_ExtPtr_allocator<_Tp>& __larg, _ExtPtr_allocator<_Tp>& __rarg)
 197     {
 198       std::allocator<_Tp> __tmp( __rarg._M_real_alloc );
 199       __rarg._M_real_alloc = __larg._M_real_alloc;
 200       __larg._M_real_alloc = __tmp;
 201     }
 202
 203 _GLIBCXX_END_NAMESPACE_VERSION
 204 } // namespace
 205
 206 #endif /* _EXTPTR_ALLOCATOR_H */