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The C and C++ Include Header Files
/usr/include/c++/11/ext/pool_allocator.h
$ cat -n /usr/include/c++/11/ext/pool_allocator.h 1 // Allocators -*- C++ -*- 2 3 // Copyright (C) 2001-2021 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/c++config.h> 46 #include <cstdlib> 47 #include <new> 48 #include <bits/functexcept.h> 49 #include <ext/atomicity.h> 50 #include <ext/concurrence.h> 51 #include <bits/move.h> 52 #if __cplusplus >= 201103L 53 #include <type_traits> 54 #endif 55 56 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 57 { 58 _GLIBCXX_BEGIN_NAMESPACE_VERSION 59 60 /** 61 * @brief Base class for __pool_alloc. 62 * 63 * Uses various allocators to fulfill underlying requests (and makes as 64 * few requests as possible when in default high-speed pool mode). 65 * 66 * Important implementation properties: 67 * 0. If globally mandated, then allocate objects from new 68 * 1. If the clients request an object of size > _S_max_bytes, the resulting 69 * object will be obtained directly from new 70 * 2. In all other cases, we allocate an object of size exactly 71 * _S_round_up(requested_size). Thus the client has enough size 72 * information that we can return the object to the proper free list 73 * without permanently losing part of the object. 74 */ 75 class __pool_alloc_base 76 { 77 typedef std::size_t size_t; 78 protected: 79 80 enum { _S_align = 8 }; 81 enum { _S_max_bytes = 128 }; 82 enum { _S_free_list_size = (size_t)_S_max_bytes / (size_t)_S_align }; 83 84 union _Obj 85 { 86 union _Obj* _M_free_list_link; 87 char _M_client_data[1]; // The client sees this. 88 }; 89 90 static _Obj* volatile _S_free_list[_S_free_list_size]; 91 92 // Chunk allocation state. 93 static char* _S_start_free; 94 static char* _S_end_free; 95 static size_t _S_heap_size; 96 97 size_t 98 _M_round_up(size_t __bytes) 99 { return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); } 100 101 _GLIBCXX_CONST _Obj* volatile* 102 _M_get_free_list(size_t __bytes) throw (); 103 104 __mutex& 105 _M_get_mutex() throw (); 106 107 // Returns an object of size __n, and optionally adds to size __n 108 // free list. 109 void* 110 _M_refill(size_t __n); 111 112 // Allocates a chunk for nobjs of size size. nobjs may be reduced 113 // if it is inconvenient to allocate the requested number. 114 char* 115 _M_allocate_chunk(size_t __n, int& __nobjs); 116 }; 117 118 119 /** 120 * @brief Allocator using a memory pool with a single lock. 121 * @ingroup allocators 122 */ 123 template<typename _Tp> 124 class __pool_alloc : private __pool_alloc_base 125 { 126 private: 127 static _Atomic_word _S_force_new; 128 129 public: 130 typedef std::size_t size_type; 131 typedef std::ptrdiff_t difference_type; 132 typedef _Tp* pointer; 133 typedef const _Tp* const_pointer; 134 typedef _Tp& reference; 135 typedef const _Tp& const_reference; 136 typedef _Tp value_type; 137 138 template<typename _Tp1> 139 struct rebind 140 { typedef __pool_alloc<_Tp1> other; }; 141 142 #if __cplusplus >= 201103L 143 // _GLIBCXX_RESOLVE_LIB_DEFECTS 144 // 2103. propagate_on_container_move_assignment 145 typedef std::true_type propagate_on_container_move_assignment; 146 #endif 147 148 __pool_alloc() _GLIBCXX_USE_NOEXCEPT { } 149 150 __pool_alloc(const __pool_alloc&) _GLIBCXX_USE_NOEXCEPT { } 151 152 template<typename _Tp1> 153 __pool_alloc(const __pool_alloc<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { } 154 155 ~__pool_alloc() _GLIBCXX_USE_NOEXCEPT { } 156 157 pointer 158 address(reference __x) const _GLIBCXX_NOEXCEPT 159 { return std::__addressof(__x); } 160 161 const_pointer 162 address(const_reference __x) const _GLIBCXX_NOEXCEPT 163 { return std::__addressof(__x); } 164 165 size_type 166 max_size() const _GLIBCXX_USE_NOEXCEPT 167 { return std::size_t(-1) / sizeof(_Tp); } 168 169 #if __cplusplus >= 201103L 170 template<typename _Up, typename... _Args> 171 void 172 construct(_Up* __p, _Args&&... __args) 173 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } 174 175 template<typename _Up> 176 void 177 destroy(_Up* __p) { __p->~_Up(); } 178 #else 179 // _GLIBCXX_RESOLVE_LIB_DEFECTS 180 // 402. wrong new expression in [some_] allocator::construct 181 void 182 construct(pointer __p, const _Tp& __val) 183 { ::new((void *)__p) _Tp(__val); } 184 185 void 186 destroy(pointer __p) { __p->~_Tp(); } 187 #endif 188 189 _GLIBCXX_NODISCARD pointer 190 allocate(size_type __n, const void* = 0); 191 192 void 193 deallocate(pointer __p, size_type __n); 194 }; 195 196 template<typename _Tp> 197 inline bool 198 operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 199 { return true; } 200 201 #if __cpp_impl_three_way_comparison < 201907L 202 template<typename _Tp> 203 inline bool 204 operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 205 { return false; } 206 #endif 207 208 template<typename _Tp> 209 _Atomic_word 210 __pool_alloc<_Tp>::_S_force_new; 211 212 template<typename _Tp> 213 _GLIBCXX_NODISCARD _Tp* 214 __pool_alloc<_Tp>::allocate(size_type __n, const void*) 215 { 216 using std::size_t; 217 pointer __ret = 0; 218 if (__builtin_expect(__n != 0, true)) 219 { 220 if (__n > this->max_size()) 221 std::__throw_bad_alloc(); 222 223 const size_t __bytes = __n * sizeof(_Tp); 224 225 #if __cpp_aligned_new 226 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 227 { 228 std::align_val_t __al = std::align_val_t(alignof(_Tp)); 229 return static_cast<_Tp*>(::operator new(__bytes, __al)); 230 } 231 #endif 232 233 // If there is a race through here, assume answer from getenv 234 // will resolve in same direction. Inspired by techniques 235 // to efficiently support threading found in basic_string.h. 236 if (_S_force_new == 0) 237 { 238 if (std::getenv("GLIBCXX_FORCE_NEW")) 239 __atomic_add_dispatch(&_S_force_new, 1); 240 else 241 __atomic_add_dispatch(&_S_force_new, -1); 242 } 243 244 if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0) 245 __ret = static_cast<_Tp*>(::operator new(__bytes)); 246 else 247 { 248 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 249 250 __scoped_lock sentry(_M_get_mutex()); 251 _Obj* __restrict__ __result = *__free_list; 252 if (__builtin_expect(__result == 0, 0)) 253 __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes))); 254 else 255 { 256 *__free_list = __result->_M_free_list_link; 257 __ret = reinterpret_cast<_Tp*>(__result); 258 } 259 if (__ret == 0) 260 std::__throw_bad_alloc(); 261 } 262 } 263 return __ret; 264 } 265 266 template<typename _Tp> 267 void 268 __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n) 269 { 270 using std::size_t; 271 if (__builtin_expect(__n != 0 && __p != 0, true)) 272 { 273 #if __cpp_aligned_new 274 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 275 { 276 ::operator delete(__p, std::align_val_t(alignof(_Tp))); 277 return; 278 } 279 #endif 280 const size_t __bytes = __n * sizeof(_Tp); 281 if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0) 282 ::operator delete(__p); 283 else 284 { 285 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 286 _Obj* __q = reinterpret_cast<_Obj*>(__p); 287 288 __scoped_lock sentry(_M_get_mutex()); 289 __q ->_M_free_list_link = *__free_list; 290 *__free_list = __q; 291 } 292 } 293 } 294 295 _GLIBCXX_END_NAMESPACE_VERSION 296 } // namespace 297 298 #endif
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