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

   1 // <extptr_allocator.h> -*- C++ -*-
   2
   3 // Copyright (C) 2008-2020 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 <memory>
  40 #include <ext/numeric_traits.h>
  41 #include <ext/pointer.h>
  42
  43 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  44 {
  45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  46
  47   /**
  48    * @brief An example allocator which uses a non-standard pointer type.
  49    * @ingroup allocators
  50    *
  51    * This allocator specifies that containers use a 'relative pointer' as it's
  52    * pointer type.  (See ext/pointer.h)  Memory allocation in this example
  53    * is still performed using std::allocator.
  54    */
  55   template<typename _Tp>
  56     class _ExtPtr_allocator
  57     {
  58     public:
  59       typedef std::size_t     size_type;
  60       typedef std::ptrdiff_t  difference_type;
  61
  62       // Note the non-standard pointer types.
  63       typedef _Pointer_adapter<_Relative_pointer_impl<_Tp> >       pointer;
  64       typedef _Pointer_adapter<_Relative_pointer_impl<const _Tp> >
  65                                                              const_pointer;
  66
  67       typedef _Tp&       reference;
  68       typedef const _Tp& const_reference;
  69       typedef _Tp        value_type;
  70
  71       template<typename _Up>
  72         struct rebind
  73         { typedef _ExtPtr_allocator<_Up> other; };
  74
  75       _ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
  76       : _M_real_alloc() { }
  77
  78       _ExtPtr_allocator(const _ExtPtr_allocator& __rarg) _GLIBCXX_USE_NOEXCEPT
  79       : _M_real_alloc(__rarg._M_real_alloc) { }
  80
  81       template<typename _Up>
  82         _ExtPtr_allocator(const _ExtPtr_allocator<_Up>& __rarg)
  83         _GLIBCXX_USE_NOEXCEPT
  84         : _M_real_alloc(__rarg._M_getUnderlyingImp()) { }
  85
  86       ~_ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
  87       { }
  88
  89       pointer address(reference __x) const _GLIBCXX_NOEXCEPT
  90       { return std::__addressof(__x); }
  91
  92       const_pointer address(const_reference __x) const _GLIBCXX_NOEXCEPT
  93       { return std::__addressof(__x); }
  94
  95       _GLIBCXX_NODISCARD pointer allocate(size_type __n, const void* = 0)
  96       { return _M_real_alloc.allocate(__n); }
  97
  98       void deallocate(pointer __p, size_type __n)
  99       { _M_real_alloc.deallocate(__p.get(), __n); }
 100
 101       size_type max_size() const _GLIBCXX_USE_NOEXCEPT
 102       { return __numeric_traits<size_type>::__max / sizeof(_Tp); }
 103
 104 #if __cplusplus >= 201103L
 105       template<typename _Up, typename... _Args>
 106         void
 107         construct(_Up* __p, _Args&&... __args)
 108         { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 109
 110       template<typename... _Args>
 111         void
 112         construct(pointer __p, _Args&&... __args)
 113         { construct(__p.get(), std::forward<_Args>(__args)...); }
 114
 115       template<typename _Up>
 116         void
 117         destroy(_Up* __p)
 118         { __p->~_Up(); }
 119
 120       void destroy(pointer __p)
 121       { destroy(__p.get()); }
 122
 123 #else
 124
 125       void construct(pointer __p, const _Tp& __val)
 126       { ::new(__p.get()) _Tp(__val); }
 127
 128       void destroy(pointer __p)
 129       { __p->~_Tp(); }
 130 #endif
 131
 132       template<typename _Up>
 133         inline bool
 134         operator==(const _ExtPtr_allocator<_Up>& __rarg)
 135         { return _M_real_alloc == __rarg._M_getUnderlyingImp(); }
 136
 137       inline bool
 138       operator==(const _ExtPtr_allocator& __rarg)
 139       { return _M_real_alloc == __rarg._M_real_alloc; }
 140
 141       template<typename _Up>
 142         inline bool
 143         operator!=(const _ExtPtr_allocator<_Up>& __rarg)
 144         { return _M_real_alloc != __rarg._M_getUnderlyingImp(); }
 145
 146       inline bool
 147       operator!=(const _ExtPtr_allocator& __rarg)
 148       { return _M_real_alloc != __rarg._M_real_alloc; }
 149
 150       template<typename _Up>
 151         inline friend void
 152         swap(_ExtPtr_allocator<_Up>&, _ExtPtr_allocator<_Up>&);
 153
 154       // A method specific to this implementation.
 155       const std::allocator<_Tp>&
 156       _M_getUnderlyingImp() const
 157       { return _M_real_alloc; }
 158
 159     private:
 160       std::allocator<_Tp>  _M_real_alloc;
 161     };
 162
 163   // _ExtPtr_allocator<void> specialization.
 164   template<>
 165     class _ExtPtr_allocator<void>
 166     {
 167     public:
 168       typedef std::size_t      size_type;
 169       typedef std::ptrdiff_t   difference_type;
 170       typedef void             value_type;
 171
 172       // Note the non-standard pointer types
 173       typedef _Pointer_adapter<_Relative_pointer_impl<void> >       pointer;
 174       typedef _Pointer_adapter<_Relative_pointer_impl<const void> >
 175                                                               const_pointer;
 176
 177       template<typename _Up>
 178         struct rebind
 179         { typedef _ExtPtr_allocator<_Up> other; };
 180
 181     private:
 182       std::allocator<void>  _M_real_alloc;
 183     };
 184
 185   template<typename _Tp>
 186     inline void
 187     swap(_ExtPtr_allocator<_Tp>& __larg, _ExtPtr_allocator<_Tp>& __rarg)
 188     {
 189       std::allocator<_Tp> __tmp( __rarg._M_real_alloc );
 190       __rarg._M_real_alloc = __larg._M_real_alloc;
 191       __larg._M_real_alloc = __tmp;
 192     }
 193
 194 _GLIBCXX_END_NAMESPACE_VERSION
 195 } // namespace
 196
 197 #endif /* _EXTPTR_ALLOCATOR_H */