libstdc++

pool_allocator.h
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1 // Allocators -*- C++ -*-
2
3 // Copyright (C) 2001-2013 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 using std::size_t;
61 using std::ptrdiff_t;
62
63 /**
64 * @brief Base class for __pool_alloc.
65 *
66 * Uses various allocators to fulfill underlying requests (and makes as
67 * few requests as possible when in default high-speed pool mode).
68 *
69 * Important implementation properties:
70 * 0. If globally mandated, then allocate objects from new
71 * 1. If the clients request an object of size > _S_max_bytes, the resulting
72 * object will be obtained directly from new
73 * 2. In all other cases, we allocate an object of size exactly
74 * _S_round_up(requested_size). Thus the client has enough size
75 * information that we can return the object to the proper free list
76 * without permanently losing part of the object.
77 */
78 class __pool_alloc_base
79 {
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 size_t size_type;
133 typedef 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 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 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 template<typename _Tp>
204 inline bool
205 operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
206 { return false; }
207
208 template<typename _Tp>
209 _Atomic_word
210 __pool_alloc<_Tp>::_S_force_new;
211
212 template<typename _Tp>
213 _Tp*
214 __pool_alloc<_Tp>::allocate(size_type __n, const void*)
215 {
216 pointer __ret = 0;
217 if (__builtin_expect(__n != 0, true))
218 {
219 if (__n > this->max_size())
220 std::__throw_bad_alloc();
221
222 // If there is a race through here, assume answer from getenv
223 // will resolve in same direction. Inspired by techniques
224 // to efficiently support threading found in basic_string.h.
225 if (_S_force_new == 0)
226 {
227 if (std::getenv("GLIBCXX_FORCE_NEW"))
228 __atomic_add_dispatch(&_S_force_new, 1);
229 else
230 __atomic_add_dispatch(&_S_force_new, -1);
231 }
232
233 const size_t __bytes = __n * sizeof(_Tp);
234 if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0)
235 __ret = static_cast<_Tp*>(::operator new(__bytes));
236 else
237 {
238 _Obj* volatile* __free_list = _M_get_free_list(__bytes);
239
240 __scoped_lock sentry(_M_get_mutex());
241 _Obj* __restrict__ __result = *__free_list;
242 if (__builtin_expect(__result == 0, 0))
243 __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes)));
244 else
245 {
246 *__free_list = __result->_M_free_list_link;
247 __ret = reinterpret_cast<_Tp*>(__result);
248 }
249 if (__ret == 0)
250 std::__throw_bad_alloc();
251 }
252 }
253 return __ret;
254 }
255
256 template<typename _Tp>
257 void
258 __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n)
259 {
260 if (__builtin_expect(__n != 0 && __p != 0, true))
261 {
262 const size_t __bytes = __n * sizeof(_Tp);
263 if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0)
264 ::operator delete(__p);
265 else
266 {
267 _Obj* volatile* __free_list = _M_get_free_list(__bytes);
268 _Obj* __q = reinterpret_cast<_Obj*>(__p);
269
270 __scoped_lock sentry(_M_get_mutex());
271 __q ->_M_free_list_link = *__free_list;
272 *__free_list = __q;
273 }
274 }
275 }
276
277 _GLIBCXX_END_NAMESPACE_VERSION
278 } // namespace
279
280 #endif