libstdc++
safe_base.h
Go to the documentation of this file.
1// Safe sequence/iterator base implementation -*- C++ -*-
2
3// Copyright (C) 2003-2024 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/** @file debug/safe_base.h
26 * This file is a GNU debug extension to the Standard C++ Library.
27 */
28
29#ifndef _GLIBCXX_DEBUG_SAFE_BASE_H
30#define _GLIBCXX_DEBUG_SAFE_BASE_H 1
31
32#include <ext/concurrence.h>
33
34namespace __gnu_debug
35{
36 class _Safe_sequence_base;
37
38 /** \brief Basic functionality for a @a safe iterator.
39 *
40 * The %_Safe_iterator_base base class implements the functionality
41 * of a safe iterator that is not specific to a particular iterator
42 * type. It contains a pointer back to the sequence it references
43 * along with iterator version information and pointers to form a
44 * doubly-linked list of iterators referenced by the container.
45 *
46 * This class must not perform any operations that can throw an
47 * exception, or the exception guarantees of derived iterators will
48 * be broken.
49 */
51 {
52 friend class _Safe_sequence_base;
53
54 public:
55 /** The sequence this iterator references; may be NULL to indicate
56 a singular iterator. */
58
59 /** The version number of this iterator. The sentinel value 0 is
60 * used to indicate an invalidated iterator (i.e., one that is
61 * singular because of an operation on the container). This
62 * version number must equal the version number in the sequence
63 * referenced by _M_sequence for the iterator to be
64 * non-singular.
65 */
66 unsigned int _M_version;
67
68 /** Pointer to the previous iterator in the sequence's list of
69 iterators. Only valid when _M_sequence != NULL. */
71
72 /** Pointer to the next iterator in the sequence's list of
73 iterators. Only valid when _M_sequence != NULL. */
75
76 protected:
77 /** Initializes the iterator and makes it singular. */
78 _GLIBCXX20_CONSTEXPR
82
83 /** Initialize the iterator to reference the sequence pointed to
84 * by @p __seq. @p __constant is true when we are initializing a
85 * constant iterator, and false if it is a mutable iterator. Note
86 * that @p __seq may be NULL, in which case the iterator will be
87 * singular. Otherwise, the iterator will reference @p __seq and
88 * be nonsingular.
89 */
90 _GLIBCXX20_CONSTEXPR
91 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
92 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
93 {
94 if (!std::__is_constant_evaluated())
95 this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant);
96 }
97
98 /** Initializes the iterator to reference the same sequence that
99 @p __x does. @p __constant is true if this is a constant
100 iterator, and false if it is mutable. */
101 _GLIBCXX20_CONSTEXPR
102 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
103 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
104 {
105 if (!std::__is_constant_evaluated())
106 this->_M_attach(__x._M_sequence, __constant);
107 }
108
109 _GLIBCXX20_CONSTEXPR
111 {
112 if (!std::__is_constant_evaluated())
113 this->_M_detach();
114 }
115
116 /** For use in _Safe_iterator. */
117 __gnu_cxx::__mutex&
118 _M_get_mutex() throw ();
119
120 /** Attaches this iterator to the given sequence, detaching it
121 * from whatever sequence it was attached to originally. If the
122 * new sequence is the NULL pointer, the iterator is left
123 * unattached.
124 */
125 void
126 _M_attach(_Safe_sequence_base* __seq, bool __constant);
127
128 /** Likewise, but not thread-safe. */
129 void
130 _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
131
132 /** Detach the iterator for whatever sequence it is attached to,
133 * if any.
134 */
135 void
137
138 public:
139 /** Likewise, but not thread-safe. */
140 void
142
143 /** Determines if we are attached to the given sequence. */
144 bool
146 { return _M_sequence == __seq; }
147
148 /** Is this iterator singular? */
149 _GLIBCXX_PURE bool
150 _M_singular() const throw ();
151
152 /** Can we compare this iterator to the given iterator @p __x?
153 Returns true if both iterators are nonsingular and reference
154 the same sequence. */
155 _GLIBCXX_PURE bool
156 _M_can_compare(const _Safe_iterator_base& __x) const throw ();
157
158 /** Invalidate the iterator, making it singular. */
159 void
161 { _M_version = 0; }
162
163 /** Reset all member variables */
164 void
165 _M_reset() throw ();
166
167 /** Unlink itself */
168 void
169 _M_unlink() throw ()
170 {
171 if (_M_prior)
173 if (_M_next)
175 }
176 };
177
178 /** Iterators that derive from _Safe_iterator_base can be determined singular
179 * or non-singular.
180 **/
181 inline bool
182 __check_singular_aux(const _Safe_iterator_base* __x)
183 { return __x->_M_singular(); }
184
185 /**
186 * @brief Base class that supports tracking of iterators that
187 * reference a sequence.
188 *
189 * The %_Safe_sequence_base class provides basic support for
190 * tracking iterators into a sequence. Sequences that track
191 * iterators must derived from %_Safe_sequence_base publicly, so
192 * that safe iterators (which inherit _Safe_iterator_base) can
193 * attach to them. This class contains two linked lists of
194 * iterators, one for constant iterators and one for mutable
195 * iterators, and a version number that allows very fast
196 * invalidation of all iterators that reference the container.
197 *
198 * This class must ensure that no operation on it may throw an
199 * exception, otherwise @a safe sequences may fail to provide the
200 * exception-safety guarantees required by the C++ standard.
201 */
203 {
204 friend class _Safe_iterator_base;
205
206 public:
207 /// The list of mutable iterators that reference this container
209
210 /// The list of constant iterators that reference this container
212
213 /// The container version number. This number may never be 0.
214 mutable unsigned int _M_version;
215
216 protected:
217 // Initialize with a version number of 1 and no iterators
218 _GLIBCXX20_CONSTEXPR
219 _Safe_sequence_base() _GLIBCXX_NOEXCEPT
221 { }
222
223#if __cplusplus >= 201103L
224 _GLIBCXX20_CONSTEXPR
226 : _Safe_sequence_base() { }
227
228 // Move constructor swap iterators.
229 _GLIBCXX20_CONSTEXPR
230 _Safe_sequence_base(_Safe_sequence_base&& __seq) noexcept
231 : _Safe_sequence_base()
232 {
233 if (!std::__is_constant_evaluated())
234 _M_swap(__seq);
235 }
236#endif
237
238 /** Notify all iterators that reference this sequence that the
239 sequence is being destroyed. */
240 _GLIBCXX20_CONSTEXPR
242 {
243 if (!std::__is_constant_evaluated())
244 this->_M_detach_all();
245 }
246
247 /** Detach all iterators, leaving them singular. */
248 void
250
251 /** Detach all singular iterators.
252 * @post for all iterators i attached to this sequence,
253 * i->_M_version == _M_version.
254 */
255 void
257
258 /** Revalidates all attached singular iterators. This method may
259 * be used to validate iterators that were invalidated before
260 * (but for some reason, such as an exception, need to become
261 * valid again).
262 */
263 void
265
266 /** Swap this sequence with the given sequence. This operation
267 * also swaps ownership of the iterators, so that when the
268 * operation is complete all iterators that originally referenced
269 * one container now reference the other container.
270 */
271 void
272 _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT;
273
274 /** For use in _Safe_sequence. */
275 __gnu_cxx::__mutex&
276 _M_get_mutex() throw ();
277
278 /** Invalidates all iterators. */
279 void
281 { if (++_M_version == 0) _M_version = 1; }
282
283 private:
284 /** Attach an iterator to this sequence. */
285 void
286 _M_attach(_Safe_iterator_base* __it, bool __constant);
287
288 /** Likewise but not thread safe. */
289 void
290 _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
291
292 /** Detach an iterator from this sequence */
293 void
294 _M_detach(_Safe_iterator_base* __it);
295
296 /** Likewise but not thread safe. */
297 void
298 _M_detach_single(_Safe_iterator_base* __it) throw ();
299 };
300} // namespace __gnu_debug
301
302#endif
GNU debug classes for public use.
Basic functionality for a safe iterator.
Definition safe_base.h:51
_Safe_sequence_base * _M_sequence
Definition safe_base.h:57
constexpr _Safe_iterator_base(const _Safe_sequence_base *__seq, bool __constant)
Definition safe_base.h:91
__gnu_cxx::__mutex & _M_get_mutex()
void _M_attach_single(_Safe_sequence_base *__seq, bool __constant)
void _M_attach(_Safe_sequence_base *__seq, bool __constant)
bool _M_attached_to(const _Safe_sequence_base *__seq) const
Definition safe_base.h:145
_Safe_iterator_base * _M_prior
Definition safe_base.h:70
bool _M_can_compare(const _Safe_iterator_base &__x) const
_Safe_iterator_base * _M_next
Definition safe_base.h:74
constexpr _Safe_iterator_base(const _Safe_iterator_base &__x, bool __constant)
Definition safe_base.h:102
Base class that supports tracking of iterators that reference a sequence.
Definition safe_base.h:203
void _M_swap(_Safe_sequence_base &__x) noexcept
_Safe_iterator_base * _M_const_iterators
The list of constant iterators that reference this container.
Definition safe_base.h:211
__gnu_cxx::__mutex & _M_get_mutex()
_Safe_iterator_base * _M_iterators
The list of mutable iterators that reference this container.
Definition safe_base.h:208
unsigned int _M_version
The container version number. This number may never be 0.
Definition safe_base.h:214