1 // Allocators -*- C++ -*- 2 3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 4 // 2010, 2011 5 // Free Software Foundation, Inc. 6 // 7 // This file is part of the GNU ISO C++ Library. This library is free 8 // software; you can redistribute it and/or modify it under the 9 // terms of the GNU General Public License as published by the 10 // Free Software Foundation; either version 3, or (at your option) 11 // any later version. 12 13 // This library is distributed in the hope that it will be useful, 14 // but WITHOUT ANY WARRANTY; without even the implied warranty of 15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 // GNU General Public License for more details. 17 18 // Under Section 7 of GPL version 3, you are granted additional 19 // permissions described in the GCC Runtime Library Exception, version 20 // 3.1, as published by the Free Software Foundation. 21 22 // You should have received a copy of the GNU General Public License and 23 // a copy of the GCC Runtime Library Exception along with this program; 24 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 25 // <http://www.gnu.org/licenses/>. 26 27 /* 28 * Copyright (c) 1996-1997 29 * Silicon Graphics Computer Systems, Inc. 30 * 31 * Permission to use, copy, modify, distribute and sell this software 32 * and its documentation for any purpose is hereby granted without fee, 33 * provided that the above copyright notice appear in all copies and 34 * that both that copyright notice and this permission notice appear 35 * in supporting documentation. Silicon Graphics makes no 36 * representations about the suitability of this software for any 37 * purpose. It is provided "as is" without express or implied warranty. 38 */ 39 40 /** @file ext/pool_allocator.h 41 * This file is a GNU extension to the Standard C++ Library. 42 */ 43 44 #ifndef _POOL_ALLOCATOR_H 45 #define _POOL_ALLOCATOR_H 1 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 55 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 56 { 57 _GLIBCXX_BEGIN_NAMESPACE_VERSION 58 59 using std::size_t; 60 using std::ptrdiff_t; 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 protected: 80 81 enum { _S_align = 8 }; 82 enum { _S_max_bytes = 128 }; 83 enum { _S_free_list_size = (size_t)_S_max_bytes / (size_t)_S_align }; 84 85 union _Obj 86 { 87 union _Obj* _M_free_list_link; 88 char _M_client_data[1]; // The client sees this. 89 }; 90 91 static _Obj* volatile _S_free_list[_S_free_list_size]; 92 93 // Chunk allocation state. 94 static char* _S_start_free; 95 static char* _S_end_free; 96 static size_t _S_heap_size; 97 98 size_t 99 _M_round_up(size_t __bytes) 100 { return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); } 101 102 _GLIBCXX_CONST _Obj* volatile* 103 _M_get_free_list(size_t __bytes) throw (); 104 105 __mutex& 106 _M_get_mutex() throw (); 107 108 // Returns an object of size __n, and optionally adds to size __n 109 // free list. 110 void* 111 _M_refill(size_t __n); 112 113 // Allocates a chunk for nobjs of size size. nobjs may be reduced 114 // if it is inconvenient to allocate the requested number. 115 char* 116 _M_allocate_chunk(size_t __n, int& __nobjs); 117 }; 118 119 120 /** 121 * @brief Allocator using a memory pool with a single lock. 122 * @ingroup allocators 123 */ 124 template<typename _Tp> 125 class __pool_alloc : private __pool_alloc_base 126 { 127 private: 128 static _Atomic_word _S_force_new; 129 130 public: 131 typedef size_t size_type; 132 typedef ptrdiff_t difference_type; 133 typedef _Tp* pointer; 134 typedef const _Tp* const_pointer; 135 typedef _Tp& reference; 136 typedef const _Tp& const_reference; 137 typedef _Tp value_type; 138 139 template<typename _Tp1> 140 struct rebind 141 { typedef __pool_alloc<_Tp1> other; }; 142 143 __pool_alloc() _GLIBCXX_USE_NOEXCEPT { } 144 145 __pool_alloc(const __pool_alloc&) _GLIBCXX_USE_NOEXCEPT { } 146 147 template<typename _Tp1> 148 __pool_alloc(const __pool_alloc<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { } 149 150 ~__pool_alloc() _GLIBCXX_USE_NOEXCEPT { } 151 152 pointer 153 address(reference __x) const _GLIBCXX_NOEXCEPT 154 { return std::__addressof(__x); } 155 156 const_pointer 157 address(const_reference __x) const _GLIBCXX_NOEXCEPT 158 { return std::__addressof(__x); } 159 160 size_type 161 max_size() const _GLIBCXX_USE_NOEXCEPT 162 { return size_t(-1) / sizeof(_Tp); } 163 164 #ifdef __GXX_EXPERIMENTAL_CXX0X__ 165 template<typename _Up, typename... _Args> 166 void 167 construct(_Up* __p, _Args&&... __args) 168 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } 169 170 template<typename _Up> 171 void 172 destroy(_Up* __p) { __p->~_Up(); } 173 #else 174 // _GLIBCXX_RESOLVE_LIB_DEFECTS 175 // 402. wrong new expression in [some_] allocator::construct 176 void 177 construct(pointer __p, const _Tp& __val) 178 { ::new((void *)__p) _Tp(__val); } 179 180 void 181 destroy(pointer __p) { __p->~_Tp(); } 182 #endif 183 184 pointer 185 allocate(size_type __n, const void* = 0); 186 187 void 188 deallocate(pointer __p, size_type __n); 189 }; 190 191 template<typename _Tp> 192 inline bool 193 operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 194 { return true; } 195 196 template<typename _Tp> 197 inline bool 198 operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 199 { return false; } 200 201 template<typename _Tp> 202 _Atomic_word 203 __pool_alloc<_Tp>::_S_force_new; 204 205 template<typename _Tp> 206 _Tp* 207 __pool_alloc<_Tp>::allocate(size_type __n, const void*) 208 { 209 pointer __ret = 0; 210 if (__builtin_expect(__n != 0, true)) 211 { 212 if (__n > this->max_size()) 213 std::__throw_bad_alloc(); 214 215 // If there is a race through here, assume answer from getenv 216 // will resolve in same direction. Inspired by techniques 217 // to efficiently support threading found in basic_string.h. 218 if (_S_force_new == 0) 219 { 220 if (std::getenv("GLIBCXX_FORCE_NEW")) 221 __atomic_add_dispatch(&_S_force_new, 1); 222 else 223 __atomic_add_dispatch(&_S_force_new, -1); 224 } 225 226 const size_t __bytes = __n * sizeof(_Tp); 227 if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0) 228 __ret = static_cast<_Tp*>(::operator new(__bytes)); 229 else 230 { 231 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 232 233 __scoped_lock sentry(_M_get_mutex()); 234 _Obj* __restrict__ __result = *__free_list; 235 if (__builtin_expect(__result == 0, 0)) 236 __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes))); 237 else 238 { 239 *__free_list = __result->_M_free_list_link; 240 __ret = reinterpret_cast<_Tp*>(__result); 241 } 242 if (__ret == 0) 243 std::__throw_bad_alloc(); 244 } 245 } 246 return __ret; 247 } 248 249 template<typename _Tp> 250 void 251 __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n) 252 { 253 if (__builtin_expect(__n != 0 && __p != 0, true)) 254 { 255 const size_t __bytes = __n * sizeof(_Tp); 256 if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0) 257 ::operator delete(__p); 258 else 259 { 260 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 261 _Obj* __q = reinterpret_cast<_Obj*>(__p); 262 263 __scoped_lock sentry(_M_get_mutex()); 264 __q ->_M_free_list_link = *__free_list; 265 *__free_list = __q; 266 } 267 } 268 } 269 270 _GLIBCXX_END_NAMESPACE_VERSION 271 } // namespace 272 273 #endif 274