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The C and C++ Include Header Files
/usr/include/c++/13/ext/pool_allocator.h
$ cat -n /usr/include/c++/13/ext/pool_allocator.h 1 // Allocators -*- C++ -*- 2 3 // Copyright (C) 2001-2023 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 * Copyright (c) 1996-1997 27 * Silicon Graphics Computer Systems, Inc. 28 * 29 * Permission to use, copy, modify, distribute and sell this software 30 * and its documentation for any purpose is hereby granted without fee, 31 * provided that the above copyright notice appear in all copies and 32 * that both that copyright notice and this permission notice appear 33 * in supporting documentation. Silicon Graphics makes no 34 * representations about the suitability of this software for any 35 * purpose. It is provided "as is" without express or implied warranty. 36 */ 37 38 /** @file ext/pool_allocator.h 39 * This file is a GNU extension to the Standard C++ Library. 40 */ 41 42 #ifndef _POOL_ALLOCATOR_H 43 #define _POOL_ALLOCATOR_H 1 44 45 #include <bits/requires_hosted.h> // GNU extensions are currently omitted 46 47 #include <bits/c++config.h> 48 #include <cstdlib> 49 #include <new> 50 #include <bits/functexcept.h> 51 #include <ext/atomicity.h> 52 #include <ext/concurrence.h> 53 #include <bits/move.h> 54 #if __cplusplus >= 201103L 55 #include <type_traits> 56 #endif 57 58 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 59 { 60 _GLIBCXX_BEGIN_NAMESPACE_VERSION 61 62 /** 63 * @brief Base class for __pool_alloc. 64 * 65 * Uses various allocators to fulfill underlying requests (and makes as 66 * few requests as possible when in default high-speed pool mode). 67 * 68 * Important implementation properties: 69 * 0. If globally mandated, then allocate objects from new 70 * 1. If the clients request an object of size > _S_max_bytes, the resulting 71 * object will be obtained directly from new 72 * 2. In all other cases, we allocate an object of size exactly 73 * _S_round_up(requested_size). Thus the client has enough size 74 * information that we can return the object to the proper free list 75 * without permanently losing part of the object. 76 */ 77 class __pool_alloc_base 78 { 79 typedef std::size_t size_t; 80 protected: 81 82 enum { _S_align = 8 }; 83 enum { _S_max_bytes = 128 }; 84 enum { _S_free_list_size = (size_t)_S_max_bytes / (size_t)_S_align }; 85 86 union _Obj 87 { 88 union _Obj* _M_free_list_link; 89 char _M_client_data[1]; // The client sees this. 90 }; 91 92 static _Obj* volatile _S_free_list[_S_free_list_size]; 93 94 // Chunk allocation state. 95 static char* _S_start_free; 96 static char* _S_end_free; 97 static size_t _S_heap_size; 98 99 size_t 100 _M_round_up(size_t __bytes) 101 { return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); } 102 103 _GLIBCXX_CONST _Obj* volatile* 104 _M_get_free_list(size_t __bytes) throw (); 105 106 __mutex& 107 _M_get_mutex() throw (); 108 109 // Returns an object of size __n, and optionally adds to size __n 110 // free list. 111 void* 112 _M_refill(size_t __n); 113 114 // Allocates a chunk for nobjs of size size. nobjs may be reduced 115 // if it is inconvenient to allocate the requested number. 116 char* 117 _M_allocate_chunk(size_t __n, int& __nobjs); 118 }; 119 120 121 /** 122 * @brief Allocator using a memory pool with a single lock. 123 * @ingroup allocators 124 */ 125 template<typename _Tp> 126 class __pool_alloc : private __pool_alloc_base 127 { 128 private: 129 static _Atomic_word _S_force_new; 130 131 public: 132 typedef std::size_t size_type; 133 typedef std::ptrdiff_t difference_type; 134 typedef _Tp* pointer; 135 typedef const _Tp* const_pointer; 136 typedef _Tp& reference; 137 typedef const _Tp& const_reference; 138 typedef _Tp value_type; 139 140 template<typename _Tp1> 141 struct rebind 142 { typedef __pool_alloc<_Tp1> other; }; 143 144 #if __cplusplus >= 201103L 145 // _GLIBCXX_RESOLVE_LIB_DEFECTS 146 // 2103. propagate_on_container_move_assignment 147 typedef std::true_type propagate_on_container_move_assignment; 148 #endif 149 150 __pool_alloc() _GLIBCXX_USE_NOEXCEPT { } 151 152 __pool_alloc(const __pool_alloc&) _GLIBCXX_USE_NOEXCEPT { } 153 154 template<typename _Tp1> 155 __pool_alloc(const __pool_alloc<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { } 156 157 ~__pool_alloc() _GLIBCXX_USE_NOEXCEPT { } 158 159 pointer 160 address(reference __x) const _GLIBCXX_NOEXCEPT 161 { return std::__addressof(__x); } 162 163 const_pointer 164 address(const_reference __x) const _GLIBCXX_NOEXCEPT 165 { return std::__addressof(__x); } 166 167 size_type 168 max_size() const _GLIBCXX_USE_NOEXCEPT 169 { return std::size_t(-1) / sizeof(_Tp); } 170 171 #if __cplusplus >= 201103L 172 template<typename _Up, typename... _Args> 173 void 174 construct(_Up* __p, _Args&&... __args) 175 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } 176 177 template<typename _Up> 178 void 179 destroy(_Up* __p) { __p->~_Up(); } 180 #else 181 // _GLIBCXX_RESOLVE_LIB_DEFECTS 182 // 402. wrong new expression in [some_] allocator::construct 183 void 184 construct(pointer __p, const _Tp& __val) 185 { ::new((void *)__p) _Tp(__val); } 186 187 void 188 destroy(pointer __p) { __p->~_Tp(); } 189 #endif 190 191 _GLIBCXX_NODISCARD pointer 192 allocate(size_type __n, const void* = 0); 193 194 void 195 deallocate(pointer __p, size_type __n); 196 }; 197 198 template<typename _Tp> 199 inline bool 200 operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 201 { return true; } 202 203 #if __cpp_impl_three_way_comparison < 201907L 204 template<typename _Tp> 205 inline bool 206 operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 207 { return false; } 208 #endif 209 210 template<typename _Tp> 211 _Atomic_word 212 __pool_alloc<_Tp>::_S_force_new; 213 214 template<typename _Tp> 215 _GLIBCXX_NODISCARD _Tp* 216 __pool_alloc<_Tp>::allocate(size_type __n, const void*) 217 { 218 using std::size_t; 219 pointer __ret = 0; 220 if (__builtin_expect(__n != 0, true)) 221 { 222 if (__n > this->max_size()) 223 std::__throw_bad_alloc(); 224 225 const size_t __bytes = __n * sizeof(_Tp); 226 227 #if __cpp_aligned_new 228 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 229 { 230 std::align_val_t __al = std::align_val_t(alignof(_Tp)); 231 return static_cast<_Tp*>(::operator new(__bytes, __al)); 232 } 233 #endif 234 235 // If there is a race through here, assume answer from getenv 236 // will resolve in same direction. Inspired by techniques 237 // to efficiently support threading found in basic_string.h. 238 if (_S_force_new == 0) 239 { 240 if (std::getenv("GLIBCXX_FORCE_NEW")) 241 __atomic_add_dispatch(&_S_force_new, 1); 242 else 243 __atomic_add_dispatch(&_S_force_new, -1); 244 } 245 246 if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0) 247 __ret = static_cast<_Tp*>(::operator new(__bytes)); 248 else 249 { 250 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 251 252 __scoped_lock sentry(_M_get_mutex()); 253 _Obj* __restrict__ __result = *__free_list; 254 if (__builtin_expect(__result == 0, 0)) 255 __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes))); 256 else 257 { 258 *__free_list = __result->_M_free_list_link; 259 __ret = reinterpret_cast<_Tp*>(__result); 260 } 261 if (__ret == 0) 262 std::__throw_bad_alloc(); 263 } 264 } 265 return __ret; 266 } 267 268 template<typename _Tp> 269 void 270 __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n) 271 { 272 using std::size_t; 273 if (__builtin_expect(__n != 0 && __p != 0, true)) 274 { 275 #if __cpp_aligned_new 276 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 277 { 278 ::operator delete(__p, std::align_val_t(alignof(_Tp))); 279 return; 280 } 281 #endif 282 const size_t __bytes = __n * sizeof(_Tp); 283 if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0) 284 ::operator delete(__p); 285 else 286 { 287 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 288 _Obj* __q = reinterpret_cast<_Obj*>(__p); 289 290 __scoped_lock sentry(_M_get_mutex()); 291 __q ->_M_free_list_link = *__free_list; 292 *__free_list = __q; 293 } 294 } 295 } 296 297 _GLIBCXX_END_NAMESPACE_VERSION 298 } // namespace 299 300 #endif
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