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 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 // ISO C++ 14882: 27 // 28 29 #include <bits/c++config.h> 30 #include <cstdlib> 31 #include <ext/pool_allocator.h> 32 33 namespace 34 { 35 __gnu_cxx::__mutex& 36 get_palloc_mutex() 37 { 38 static __gnu_cxx::__mutex palloc_mutex; 39 return palloc_mutex; 40 } 41 } // anonymous namespace 42 43 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 44 { 45 _GLIBCXX_BEGIN_NAMESPACE_VERSION 46 47 // Definitions for __pool_alloc_base. 48 __pool_alloc_base::_Obj* volatile* 49 __pool_alloc_base::_M_get_free_list(size_t __bytes) throw () 50 { 51 size_t __i = ((__bytes + (size_t)_S_align - 1) / (size_t)_S_align - 1); 52 return _S_free_list + __i; 53 } 54 55 __mutex& 56 __pool_alloc_base::_M_get_mutex() throw () 57 { return get_palloc_mutex(); } 58 59 // Allocate memory in large chunks in order to avoid fragmenting the 60 // heap too much. Assume that __n is properly aligned. We hold the 61 // allocation lock. 62 char* 63 __pool_alloc_base::_M_allocate_chunk(size_t __n, int& __nobjs) 64 { 65 char* __result; 66 size_t __total_bytes = __n * __nobjs; 67 size_t __bytes_left = _S_end_free - _S_start_free; 68 69 if (__bytes_left >= __total_bytes) 70 { 71 __result = _S_start_free; 72 _S_start_free += __total_bytes; 73 return __result ; 74 } 75 else if (__bytes_left >= __n) 76 { 77 __nobjs = (int)(__bytes_left / __n); 78 __total_bytes = __n * __nobjs; 79 __result = _S_start_free; 80 _S_start_free += __total_bytes; 81 return __result; 82 } 83 else 84 { 85 // Try to make use of the left-over piece. 86 if (__bytes_left > 0) 87 { 88 _Obj* volatile* __free_list = _M_get_free_list(__bytes_left); 89 ((_Obj*)(void*)_S_start_free)->_M_free_list_link = *__free_list; 90 *__free_list = (_Obj*)(void*)_S_start_free; 91 } 92 93 size_t __bytes_to_get = (2 * __total_bytes 94 + _M_round_up(_S_heap_size >> 4)); 95 __try 96 { 97 _S_start_free = static_cast<char*>(::operator new(__bytes_to_get)); 98 } 99 __catch(const std::bad_alloc&) 100 { 101 // Try to make do with what we have. That can't hurt. We 102 // do not try smaller requests, since that tends to result 103 // in disaster on multi-process machines. 104 size_t __i = __n; 105 for (; __i <= (size_t) _S_max_bytes; __i += (size_t) _S_align) 106 { 107 _Obj* volatile* __free_list = _M_get_free_list(__i); 108 _Obj* __p = *__free_list; 109 if (__p != 0) 110 { 111 *__free_list = __p->_M_free_list_link; 112 _S_start_free = (char*)__p; 113 _S_end_free = _S_start_free + __i; 114 return _M_allocate_chunk(__n, __nobjs); 115 // Any leftover piece will eventually make it to the 116 // right free list. 117 } 118 } 119 // What we have wasn't enough. Rethrow. 120 _S_start_free = _S_end_free = 0; // We have no chunk. 121 __throw_exception_again; 122 } 123 _S_heap_size += __bytes_to_get; 124 _S_end_free = _S_start_free + __bytes_to_get; 125 return _M_allocate_chunk(__n, __nobjs); 126 } 127 } 128 129 // Returns an object of size __n, and optionally adds to "size 130 // __n"'s free list. We assume that __n is properly aligned. We 131 // hold the allocation lock. 132 void* 133 __pool_alloc_base::_M_refill(size_t __n) 134 { 135 int __nobjs = 20; 136 char* __chunk = _M_allocate_chunk(__n, __nobjs); 137 _Obj* volatile* __free_list; 138 _Obj* __result; 139 _Obj* __current_obj; 140 _Obj* __next_obj; 141 142 if (__nobjs == 1) 143 return __chunk; 144 __free_list = _M_get_free_list(__n); 145 146 // Build free list in chunk. 147 __result = (_Obj*)(void*)__chunk; 148 *__free_list = __next_obj = (_Obj*)(void*)(__chunk + __n); 149 for (int __i = 1; ; __i++) 150 { 151 __current_obj = __next_obj; 152 __next_obj = (_Obj*)(void*)((char*)__next_obj + __n); 153 if (__nobjs - 1 == __i) 154 { 155 __current_obj->_M_free_list_link = 0; 156 break; 157 } 158 else 159 __current_obj->_M_free_list_link = __next_obj; 160 } 161 return __result; 162 } 163 164 __pool_alloc_base::_Obj* volatile __pool_alloc_base::_S_free_list[_S_free_list_size]; 165 166 char* __pool_alloc_base::_S_start_free = 0; 167 168 char* __pool_alloc_base::_S_end_free = 0; 169 170 size_t __pool_alloc_base::_S_heap_size = 0; 171 172 // Instantiations. 173 template class __pool_alloc<char>; 174 template class __pool_alloc<wchar_t>; 175 176 _GLIBCXX_END_NAMESPACE_VERSION 177 } // namespace 178