1 // Allocators -*- C++ -*- 2 3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 4 // Free Software Foundation, Inc. 5 // 6 // This file is part of the GNU ISO C++ Library. This library is free 7 // software; you can redistribute it and/or modify it under the 8 // terms of the GNU General Public License as published by the 9 // Free Software Foundation; either version 3, or (at your option) 10 // any later version. 11 12 // This library is distributed in the hope that it will be useful, 13 // but WITHOUT ANY WARRANTY; without even the implied warranty of 14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 // GNU General Public License for more details. 16 17 // Under Section 7 of GPL version 3, you are granted additional 18 // permissions described in the GCC Runtime Library Exception, version 19 // 3.1, as published by the Free Software Foundation. 20 21 // You should have received a copy of the GNU General Public License and 22 // a copy of the GCC Runtime Library Exception along with this program; 23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 24 // <http://www.gnu.org/licenses/>. 25 26 /* 27 * Copyright (c) 1996-1997 28 * Silicon Graphics Computer Systems, Inc. 29 * 30 * Permission to use, copy, modify, distribute and sell this software 31 * and its documentation for any purpose is hereby granted without fee, 32 * provided that the above copyright notice appear in all copies and 33 * that both that copyright notice and this permission notice appear 34 * in supporting documentation. Silicon Graphics makes no 35 * representations about the suitability of this software for any 36 * purpose. It is provided "as is" without express or implied warranty. 37 */ 38 39 /** @file ext/pool_allocator.h 40 * This file is a GNU extension to the Standard C++ Library. 41 */ 42 43 #ifndef _POOL_ALLOCATOR_H 44 #define _POOL_ALLOCATOR_H 1 45 46 #include <bits/c++config.h> 47 #include <cstdlib> 48 #include <new> 49 #include <bits/functexcept.h> 50 #include <ext/atomicity.h> 51 #include <ext/concurrence.h> 52 #include <bits/move.h> 53 54 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 55 { 56 _GLIBCXX_BEGIN_NAMESPACE_VERSION 57 58 using std::size_t; 59 using std::ptrdiff_t; 60 61 /** 62 * @brief Base class for __pool_alloc. 63 * 64 * Uses various allocators to fulfill underlying requests (and makes as 65 * few requests as possible when in default high-speed pool mode). 66 * 67 * Important implementation properties: 68 * 0. If globally mandated, then allocate objects from new 69 * 1. If the clients request an object of size > _S_max_bytes, the resulting 70 * object will be obtained directly from new 71 * 2. In all other cases, we allocate an object of size exactly 72 * _S_round_up(requested_size). Thus the client has enough size 73 * information that we can return the object to the proper free list 74 * without permanently losing part of the object. 75 */ 76 class __pool_alloc_base 77 { 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 size_t size_type; 131 typedef 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 __pool_alloc() throw() { } 143 144 __pool_alloc(const __pool_alloc&) throw() { } 145 146 template<typename _Tp1> 147 __pool_alloc(const __pool_alloc<_Tp1>&) throw() { } 148 149 ~__pool_alloc() throw() { } 150 151 pointer 152 address(reference __x) const { return std::__addressof(__x); } 153 154 const_pointer 155 address(const_reference __x) const { return std::__addressof(__x); } 156 157 size_type 158 max_size() const throw() 159 { return size_t(-1) / sizeof(_Tp); } 160 161 // _GLIBCXX_RESOLVE_LIB_DEFECTS 162 // 402. wrong new expression in [some_] allocator::construct 163 void 164 construct(pointer __p, const _Tp& __val) 165 { ::new((void *)__p) _Tp(__val); } 166 167 #ifdef __GXX_EXPERIMENTAL_CXX0X__ 168 template<typename... _Args> 169 void 170 construct(pointer __p, _Args&&... __args) 171 { ::new((void *)__p) _Tp(std::forward<_Args>(__args)...); } 172 #endif 173 174 void 175 destroy(pointer __p) { __p->~_Tp(); } 176 177 pointer 178 allocate(size_type __n, const void* = 0); 179 180 void 181 deallocate(pointer __p, size_type __n); 182 }; 183 184 template<typename _Tp> 185 inline bool 186 operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 187 { return true; } 188 189 template<typename _Tp> 190 inline bool 191 operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 192 { return false; } 193 194 template<typename _Tp> 195 _Atomic_word 196 __pool_alloc<_Tp>::_S_force_new; 197 198 template<typename _Tp> 199 _Tp* 200 __pool_alloc<_Tp>::allocate(size_type __n, const void*) 201 { 202 pointer __ret = 0; 203 if (__builtin_expect(__n != 0, true)) 204 { 205 if (__n > this->max_size()) 206 std::__throw_bad_alloc(); 207 208 // If there is a race through here, assume answer from getenv 209 // will resolve in same direction. Inspired by techniques 210 // to efficiently support threading found in basic_string.h. 211 if (_S_force_new == 0) 212 { 213 if (std::getenv("GLIBCXX_FORCE_NEW")) 214 __atomic_add_dispatch(&_S_force_new, 1); 215 else 216 __atomic_add_dispatch(&_S_force_new, -1); 217 } 218 219 const size_t __bytes = __n * sizeof(_Tp); 220 if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0) 221 __ret = static_cast<_Tp*>(::operator new(__bytes)); 222 else 223 { 224 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 225 226 __scoped_lock sentry(_M_get_mutex()); 227 _Obj* __restrict__ __result = *__free_list; 228 if (__builtin_expect(__result == 0, 0)) 229 __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes))); 230 else 231 { 232 *__free_list = __result->_M_free_list_link; 233 __ret = reinterpret_cast<_Tp*>(__result); 234 } 235 if (__ret == 0) 236 std::__throw_bad_alloc(); 237 } 238 } 239 return __ret; 240 } 241 242 template<typename _Tp> 243 void 244 __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n) 245 { 246 if (__builtin_expect(__n != 0 && __p != 0, true)) 247 { 248 const size_t __bytes = __n * sizeof(_Tp); 249 if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0) 250 ::operator delete(__p); 251 else 252 { 253 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 254 _Obj* __q = reinterpret_cast<_Obj*>(__p); 255 256 __scoped_lock sentry(_M_get_mutex()); 257 __q ->_M_free_list_link = *__free_list; 258 *__free_list = __q; 259 } 260 } 261 } 262 263 _GLIBCXX_END_NAMESPACE_VERSION 264 } // namespace 265 266 #endif 267
