1 // Allocators -*- C++ -*- 2 3 // Copyright (C) 2001, 2002, 2003, 2004 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 2, 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 // You should have received a copy of the GNU General Public License along 17 // with this library; see the file COPYING. If not, write to the Free 18 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, 19 // USA. 20 21 // As a special exception, you may use this file as part of a free software 22 // library without restriction. Specifically, if other files instantiate 23 // templates or use macros or inline functions from this file, or you compile 24 // this file and link it with other files to produce an executable, this 25 // file does not by itself cause the resulting executable to be covered by 26 // the GNU General Public License. This exception does not however 27 // invalidate any other reasons why the executable file might be covered by 28 // the GNU General Public License. 29 30 /* 31 * Copyright (c) 1996-1997 32 * Silicon Graphics Computer Systems, Inc. 33 * 34 * Permission to use, copy, modify, distribute and sell this software 35 * and its documentation for any purpose is hereby granted without fee, 36 * provided that the above copyright notice appear in all copies and 37 * that both that copyright notice and this permission notice appear 38 * in supporting documentation. Silicon Graphics makes no 39 * representations about the suitability of this software for any 40 * purpose. It is provided "as is" without express or implied warranty. 41 */ 42 43 /** @file ext/pool_allocator.h 44 * This file is a GNU extension to the Standard C++ Library. 45 * You should only include this header if you are using GCC 3 or later. 46 */ 47 #ifndef _POOL_ALLOCATOR_H 48 #define _POOL_ALLOCATOR_H 1 49 50 #include <bits/c++config.h> 51 #include <cstdlib> 52 #include <new> 53 #include <bits/functexcept.h> 54 #include <bits/atomicity.h> 55 #include <bits/concurrence.h> 56 57 namespace __gnu_cxx 58 { 59 /** 60 * @if maint 61 * Uses various allocators to fulfill underlying requests (and makes as 62 * few requests as possible when in default high-speed pool mode). 63 * 64 * Important implementation properties: 65 * 0. If globally mandated, then allocate objects from new 66 * 1. If the clients request an object of size > _S_max_bytes, the resulting 67 * object will be obtained directly from new 68 * 2. In all other cases, we allocate an object of size exactly 69 * _S_round_up(requested_size). Thus the client has enough size 70 * information that we can return the object to the proper free list 71 * without permanently losing part of the object. 72 * 73 * @endif 74 * (See @link Allocators allocators info @endlink for more.) 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 = _S_max_bytes / _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 _Obj* volatile* 102 _M_get_free_list(size_t __bytes); 103 104 mutex_type& 105 _M_get_mutex(); 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 template<typename _Tp> 120 class __pool_alloc : private __pool_alloc_base 121 { 122 private: 123 static _Atomic_word _S_force_new; 124 125 public: 126 typedef size_t size_type; 127 typedef ptrdiff_t difference_type; 128 typedef _Tp* pointer; 129 typedef const _Tp* const_pointer; 130 typedef _Tp& reference; 131 typedef const _Tp& const_reference; 132 typedef _Tp value_type; 133 134 template<typename _Tp1> 135 struct rebind 136 { typedef __pool_alloc<_Tp1> other; }; 137 138 __pool_alloc() throw() { } 139 140 __pool_alloc(const __pool_alloc&) throw() { } 141 142 template<typename _Tp1> 143 __pool_alloc(const __pool_alloc<_Tp1>&) throw() { } 144 145 ~__pool_alloc() throw() { } 146 147 pointer 148 address(reference __x) const { return &__x; } 149 150 const_pointer 151 address(const_reference __x) const { return &__x; } 152 153 size_type 154 max_size() const throw() 155 { return size_t(-1) / sizeof(_Tp); } 156 157 // _GLIBCXX_RESOLVE_LIB_DEFECTS 158 // 402. wrong new expression in [some_] allocator::construct 159 void 160 construct(pointer __p, const _Tp& __val) 161 { ::new(__p) _Tp(__val); } 162 163 void 164 destroy(pointer __p) { __p->~_Tp(); } 165 166 pointer 167 allocate(size_type __n, const void* = 0); 168 169 void 170 deallocate(pointer __p, size_type __n); 171 }; 172 173 template<typename _Tp> 174 inline bool 175 operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 176 { return true; } 177 178 template<typename _Tp> 179 inline bool 180 operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) 181 { return false; } 182 183 template<typename _Tp> 184 _Atomic_word 185 __pool_alloc<_Tp>::_S_force_new; 186 187 template<typename _Tp> 188 _Tp* 189 __pool_alloc<_Tp>::allocate(size_type __n, const void*) 190 { 191 pointer __ret = 0; 192 if (__n) 193 { 194 if (__n <= max_size()) 195 { 196 // If there is a race through here, assume answer from getenv 197 // will resolve in same direction. Inspired by techniques 198 // to efficiently support threading found in basic_string.h. 199 if (_S_force_new == 0) 200 { 201 if (getenv("GLIBCXX_FORCE_NEW")) 202 __atomic_add(&_S_force_new, 1); 203 else 204 __atomic_add(&_S_force_new, -1); 205 } 206 207 const size_t __bytes = __n * sizeof(_Tp); 208 if (__bytes > size_t(_S_max_bytes) || _S_force_new == 1) 209 __ret = static_cast<_Tp*>(::operator new(__bytes)); 210 else 211 { 212 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 213 214 lock sentry(_M_get_mutex()); 215 _Obj* __restrict__ __result = *__free_list; 216 if (__builtin_expect(__result == 0, 0)) 217 __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes))); 218 else 219 { 220 *__free_list = __result->_M_free_list_link; 221 __ret = reinterpret_cast<_Tp*>(__result); 222 } 223 if (__builtin_expect(__ret == 0, 0)) 224 std::__throw_bad_alloc(); 225 } 226 } 227 else 228 std::__throw_bad_alloc(); 229 } 230 return __ret; 231 } 232 233 template<typename _Tp> 234 void 235 __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n) 236 { 237 if (__n) 238 { 239 const size_t __bytes = __n * sizeof(_Tp); 240 if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new == 1) 241 ::operator delete(__p); 242 else 243 { 244 _Obj* volatile* __free_list = _M_get_free_list(__bytes); 245 _Obj* __q = reinterpret_cast<_Obj*>(__p); 246 247 lock sentry(_M_get_mutex()); 248 __q ->_M_free_list_link = *__free_list; 249 *__free_list = __q; 250 } 251 } 252 } 253 } // namespace __gnu_cxx 254 255 #endif 256