1// Allocator details.
2
3// Copyright (C) 2004-2020 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
33namespace
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
43namespace __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