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
38namespace
39{
40  __gnu_cxx::__mutex palloc_init_mutex;
41} // anonymous namespace
42
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&
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*
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*
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