libstdc++-v3/include/ext/pool_allocator.h

   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  */
  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    *  @brief  Base class for __pool_alloc.
  61    *
  62    *  @if maint
  63    *  Uses various allocators to fulfill underlying requests (and makes as
  64    *  few requests as possible when in default high-speed pool mode).
  65    *
  66    *  Important implementation properties:
  67    *  0. If globally mandated, then allocate objects from new
  68    *  1. If the clients request an object of size > _S_max_bytes, the resulting
  69    *     object will be obtained directly from new
  70    *  2. In all other cases, we allocate an object of size exactly
  71    *     _S_round_up(requested_size).  Thus the client has enough size
  72    *     information that we can return the object to the proper free list
  73    *     without permanently losing part of the object.
  74    *
  75    *  @endif
  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 = _S_max_bytes / _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       _Obj* volatile*
 103       _M_get_free_list(size_t __bytes);
 104
 105       mutex_type&
 106       _M_get_mutex();
 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   /// @brief  class __pool_alloc.
 121   template<typename _Tp>
 122     class __pool_alloc : private __pool_alloc_base
 123     {
 124     private:
 125       static _Atomic_word           _S_force_new;
 126
 127     public:
 128       typedef size_t     size_type;
 129       typedef ptrdiff_t  difference_type;
 130       typedef _Tp*       pointer;
 131       typedef const _Tp* const_pointer;
 132       typedef _Tp&       reference;
 133       typedef const _Tp& const_reference;
 134       typedef _Tp        value_type;
 135
 136       template<typename _Tp1>
 137         struct rebind
 138         { typedef __pool_alloc<_Tp1> other; };
 139
 140       __pool_alloc() throw() { }
 141
 142       __pool_alloc(const __pool_alloc&) throw() { }
 143
 144       template<typename _Tp1>
 145         __pool_alloc(const __pool_alloc<_Tp1>&) throw() { }
 146
 147       ~__pool_alloc() throw() { }
 148
 149       pointer
 150       address(reference __x) const { return &__x; }
 151
 152       const_pointer
 153       address(const_reference __x) const { return &__x; }
 154
 155       size_type
 156       max_size() const throw()
 157       { return size_t(-1) / sizeof(_Tp); }
 158
 159       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 160       // 402. wrong new expression in [some_] allocator::construct
 161       void
 162       construct(pointer __p, const _Tp& __val)
 163       { ::new(__p) _Tp(__val); }
 164
 165       void
 166       destroy(pointer __p) { __p->~_Tp(); }
 167
 168       pointer
 169       allocate(size_type __n, const void* = 0);
 170
 171       void
 172       deallocate(pointer __p, size_type __n);
 173     };
 174
 175   template<typename _Tp>
 176     inline bool
 177     operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
 178     { return true; }
 179
 180   template<typename _Tp>
 181     inline bool
 182     operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)
 183     { return false; }
 184
 185   template<typename _Tp>
 186     _Atomic_word
 187     __pool_alloc<_Tp>::_S_force_new;
 188
 189   template<typename _Tp>
 190     _Tp*
 191     __pool_alloc<_Tp>::allocate(size_type __n, const void*)
 192     {
 193       pointer __ret = 0;
 194       if (__builtin_expect(__n != 0, true))
 195         {
 196           if (__builtin_expect(__n > this->max_size(), false))
 197             std::__throw_bad_alloc();
 198
 199           // If there is a race through here, assume answer from getenv
 200           // will resolve in same direction.  Inspired by techniques
 201           // to efficiently support threading found in basic_string.h.
 202           if (_S_force_new == 0)
 203             {
 204               if (getenv("GLIBCXX_FORCE_NEW"))
 205                 __atomic_add(&_S_force_new, 1);
 206               else
 207                 __atomic_add(&_S_force_new, -1);
 208             }
 209
 210           const size_t __bytes = __n * sizeof(_Tp);
 211           if (__bytes > size_t(_S_max_bytes) || _S_force_new == 1)
 212             __ret = static_cast<_Tp*>(::operator new(__bytes));
 213           else
 214             {
 215               _Obj* volatile* __free_list = _M_get_free_list(__bytes);
 216
 217               lock sentry(_M_get_mutex());
 218               _Obj* __restrict__ __result = *__free_list;
 219               if (__builtin_expect(__result == 0, 0))
 220                 __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes)));
 221               else
 222                 {
 223                   *__free_list = __result->_M_free_list_link;
 224                   __ret = reinterpret_cast<_Tp*>(__result);
 225                 }
 226               if (__builtin_expect(__ret == 0, 0))
 227                 std::__throw_bad_alloc();
 228             }
 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 (__builtin_expect(__n != 0 && __p != 0, true))
 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