summaryrefslogtreecommitdiff
path: root/libstdc++-v3/include/ext/pool_allocator.h
blob: 66ddced8054effbdddbd14cb7170569f8b96c77a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
// Allocators -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/*
 * Copyright (c) 1996-1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file ext/pool_allocator.h
 *  This file is a GNU extension to the Standard C++ Library.
 */

#ifndef _POOL_ALLOCATOR_H
#define _POOL_ALLOCATOR_H 1

#include <bits/c++config.h>
#include <cstdlib>
#include <new>
#include <bits/functexcept.h>
#include <ext/atomicity.h>
#include <ext/concurrence.h>
#include <bits/move.h>

namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  using std::size_t;
  using std::ptrdiff_t;

  /**
   *  @brief  Base class for __pool_alloc.
   *
   *  Uses various allocators to fulfill underlying requests (and makes as
   *  few requests as possible when in default high-speed pool mode).
   *
   *  Important implementation properties:
   *  0. If globally mandated, then allocate objects from new
   *  1. If the clients request an object of size > _S_max_bytes, the resulting
   *     object will be obtained directly from new
   *  2. In all other cases, we allocate an object of size exactly
   *     _S_round_up(requested_size).  Thus the client has enough size
   *     information that we can return the object to the proper free list
   *     without permanently losing part of the object.
   */
    class __pool_alloc_base
    {
    protected:

      enum { _S_align = 8 };
      enum { _S_max_bytes = 128 };
      enum { _S_free_list_size = (size_t)_S_max_bytes / (size_t)_S_align };
      
      union _Obj
      {
	union _Obj* _M_free_list_link;
	char        _M_client_data[1];    // The client sees this.
      };
      
      static _Obj* volatile         _S_free_list[_S_free_list_size];

      // Chunk allocation state.
      static char*                  _S_start_free;
      static char*                  _S_end_free;
      static size_t                 _S_heap_size;     
      
      size_t
      _M_round_up(size_t __bytes)
      { return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); }
      
      _GLIBCXX_CONST _Obj* volatile*
      _M_get_free_list(size_t __bytes) throw ();
    
      __mutex&
      _M_get_mutex() throw ();

      // Returns an object of size __n, and optionally adds to size __n
      // free list.
      void*
      _M_refill(size_t __n);
      
      // Allocates a chunk for nobjs of size size.  nobjs may be reduced
      // if it is inconvenient to allocate the requested number.
      char*
      _M_allocate_chunk(size_t __n, int& __nobjs);
    };


  /**
   * @brief  Allocator using a memory pool with a single lock.
   * @ingroup allocators
   */
  template<typename _Tp>
    class __pool_alloc : private __pool_alloc_base
    {
    private:
      static _Atomic_word	    _S_force_new;

    public:
      typedef size_t     size_type;
      typedef ptrdiff_t  difference_type;
      typedef _Tp*       pointer;
      typedef const _Tp* const_pointer;
      typedef _Tp&       reference;
      typedef const _Tp& const_reference;
      typedef _Tp        value_type;

      template<typename _Tp1>
        struct rebind
        { typedef __pool_alloc<_Tp1> other; };

      __pool_alloc() throw() { }

      __pool_alloc(const __pool_alloc&) throw() { }

      template<typename _Tp1>
        __pool_alloc(const __pool_alloc<_Tp1>&) throw() { }

      ~__pool_alloc() throw() { }

      pointer
      address(reference __x) const { return std::__addressof(__x); }

      const_pointer
      address(const_reference __x) const { return std::__addressof(__x); }

      size_type
      max_size() const throw() 
      { return size_t(-1) / sizeof(_Tp); }

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 402. wrong new expression in [some_] allocator::construct
      void 
      construct(pointer __p, const _Tp& __val) 
      { ::new((void *)__p) _Tp(__val); }

#ifdef __GXX_EXPERIMENTAL_CXX0X__
      template<typename... _Args>
        void
        construct(pointer __p, _Args&&... __args)
	{ ::new((void *)__p) _Tp(std::forward<_Args>(__args)...); }
#endif

      void 
      destroy(pointer __p) { __p->~_Tp(); }

      pointer
      allocate(size_type __n, const void* = 0);

      void
      deallocate(pointer __p, size_type __n);      
    };

  template<typename _Tp>
    inline bool
    operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
    { return true; }

  template<typename _Tp>
    inline bool
    operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
    { return false; }

  template<typename _Tp>
    _Atomic_word
    __pool_alloc<_Tp>::_S_force_new;

  template<typename _Tp>
    _Tp*
    __pool_alloc<_Tp>::allocate(size_type __n, const void*)
    {
      pointer __ret = 0;
      if (__builtin_expect(__n != 0, true))
	{
	  if (__n > this->max_size())
	    std::__throw_bad_alloc();

	  // If there is a race through here, assume answer from getenv
	  // will resolve in same direction.  Inspired by techniques
	  // to efficiently support threading found in basic_string.h.
	  if (_S_force_new == 0)
	    {
	      if (std::getenv("GLIBCXX_FORCE_NEW"))
		__atomic_add_dispatch(&_S_force_new, 1);
	      else
		__atomic_add_dispatch(&_S_force_new, -1);
	    }

	  const size_t __bytes = __n * sizeof(_Tp);	      
	  if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0)
	    __ret = static_cast<_Tp*>(::operator new(__bytes));
	  else
	    {
	      _Obj* volatile* __free_list = _M_get_free_list(__bytes);
	      
	      __scoped_lock sentry(_M_get_mutex());
	      _Obj* __restrict__ __result = *__free_list;
	      if (__builtin_expect(__result == 0, 0))
		__ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes)));
	      else
		{
		  *__free_list = __result->_M_free_list_link;
		  __ret = reinterpret_cast<_Tp*>(__result);
		}
	      if (__ret == 0)
		std::__throw_bad_alloc();
	    }
	}
      return __ret;
    }

  template<typename _Tp>
    void
    __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n)
    {
      if (__builtin_expect(__n != 0 && __p != 0, true))
	{
	  const size_t __bytes = __n * sizeof(_Tp);
	  if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0)
	    ::operator delete(__p);
	  else
	    {
	      _Obj* volatile* __free_list = _M_get_free_list(__bytes);
	      _Obj* __q = reinterpret_cast<_Obj*>(__p);

	      __scoped_lock sentry(_M_get_mutex());
	      __q ->_M_free_list_link = *__free_list;
	      *__free_list = __q;
	    }
	}
    }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif