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 */ 207
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