libstdc++-v3/src/pool_allocator.cc

   1 // Allocator details.
   2
   3 // Copyright (C) 2004, 2005, 2006, 2009 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  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 // ISO C++ 14882:
  32 //
  33
  34 #include <bits/c++config.h>
  35 #include <cstdlib>
  36 #include <ext/pool_allocator.h>
  37
  38 namespace
  39 {
  40   __gnu_cxx::__mutex&
  41   get_palloc_mutex()
  42   {
  43     static __gnu_cxx::__mutex palloc_mutex;
  44     return palloc_mutex;
  45   }
  46 } // anonymous namespace
  47
  48 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
  49
  50   // Definitions for __pool_alloc_base.
  51   __pool_alloc_base::_Obj* volatile*
  52   __pool_alloc_base::_M_get_free_list(size_t __bytes)
  53   {
  54     size_t __i = ((__bytes + (size_t)_S_align - 1) / (size_t)_S_align - 1);
  55     return _S_free_list + __i;
  56   }
  57
  58   __mutex&
  59   __pool_alloc_base::_M_get_mutex()
  60   { return get_palloc_mutex(); }
  61
  62   // Allocate memory in large chunks in order to avoid fragmenting the
  63   // heap too much.  Assume that __n is properly aligned.  We hold the
  64   // allocation lock.
  65   char*
  66   __pool_alloc_base::_M_allocate_chunk(size_t __n, int& __nobjs)
  67   {
  68     char* __result;
  69     size_t __total_bytes = __n * __nobjs;
  70     size_t __bytes_left = _S_end_free - _S_start_free;
  71
  72     if (__bytes_left >= __total_bytes)
  73       {
  74         __result = _S_start_free;
  75         _S_start_free += __total_bytes;
  76         return __result ;
  77       }
  78     else if (__bytes_left >= __n)
  79       {
  80         __nobjs = (int)(__bytes_left / __n);
  81         __total_bytes = __n * __nobjs;
  82         __result = _S_start_free;
  83         _S_start_free += __total_bytes;
  84         return __result;
  85       }
  86     else
  87       {
  88         // Try to make use of the left-over piece.
  89         if (__bytes_left > 0)
  90           {
  91             _Obj* volatile* __free_list = _M_get_free_list(__bytes_left);
  92             ((_Obj*)(void*)_S_start_free)->_M_free_list_link = *__free_list;
  93             *__free_list = (_Obj*)(void*)_S_start_free;
  94           }
  95
  96         size_t __bytes_to_get = (2 * __total_bytes
  97                                  + _M_round_up(_S_heap_size >> 4));
  98         try
  99           {
 100             _S_start_free = static_cast<char*>(::operator new(__bytes_to_get));
 101           }
 102         catch (...)
 103           {
 104             // Try to make do with what we have.  That can't hurt.  We
 105             // do not try smaller requests, since that tends to result
 106             // in disaster on multi-process machines.
 107             size_t __i = __n;
 108             for (; __i <= (size_t) _S_max_bytes; __i += (size_t) _S_align)
 109               {
 110                 _Obj* volatile* __free_list = _M_get_free_list(__i);
 111                 _Obj* __p = *__free_list;
 112                 if (__p != 0)
 113                   {
 114                     *__free_list = __p->_M_free_list_link;
 115                     _S_start_free = (char*)__p;
 116                     _S_end_free = _S_start_free + __i;
 117                     return _M_allocate_chunk(__n, __nobjs);
 118                     // Any leftover piece will eventually make it to the
 119                     // right free list.
 120                   }
 121               }
 122             // What we have wasn't enough.  Rethrow.
 123             _S_start_free = _S_end_free = 0;   // We have no chunk.
 124             __throw_exception_again;
 125           }
 126         _S_heap_size += __bytes_to_get;
 127         _S_end_free = _S_start_free + __bytes_to_get;
 128         return _M_allocate_chunk(__n, __nobjs);
 129       }
 130   }
 131
 132   // Returns an object of size __n, and optionally adds to "size
 133   // __n"'s free list.  We assume that __n is properly aligned.  We
 134   // hold the allocation lock.
 135   void*
 136   __pool_alloc_base::_M_refill(size_t __n)
 137   {
 138     int __nobjs = 20;
 139     char* __chunk = _M_allocate_chunk(__n, __nobjs);
 140     _Obj* volatile* __free_list;
 141     _Obj* __result;
 142     _Obj* __current_obj;
 143     _Obj* __next_obj;
 144
 145     if (__nobjs == 1)
 146       return __chunk;
 147     __free_list = _M_get_free_list(__n);
 148
 149     // Build free list in chunk.
 150     __result = (_Obj*)(void*)__chunk;
 151     *__free_list = __next_obj = (_Obj*)(void*)(__chunk + __n);
 152     for (int __i = 1; ; __i++)
 153       {
 154         __current_obj = __next_obj;
 155         __next_obj = (_Obj*)(void*)((char*)__next_obj + __n);
 156         if (__nobjs - 1 == __i)
 157           {
 158             __current_obj->_M_free_list_link = 0;
 159             break;
 160           }
 161         else
 162           __current_obj->_M_free_list_link = __next_obj;
 163       }
 164     return __result;
 165   }
 166
 167   __pool_alloc_base::_Obj* volatile __pool_alloc_base::_S_free_list[_S_free_list_size];
 168
 169   char* __pool_alloc_base::_S_start_free = 0;
 170
 171   char* __pool_alloc_base::_S_end_free = 0;
 172
 173   size_t __pool_alloc_base::_S_heap_size = 0;
 174
 175   // Instantiations.
 176   template class __pool_alloc<char>;
 177   template class __pool_alloc<wchar_t>;
 178
 179 _GLIBCXX_END_NAMESPACE