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