libstdc++
safe_base.h
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1 // Safe sequence/iterator base implementation -*- C++ -*-
2 
3 // Copyright (C) 2003-2021 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 
34 namespace __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. */
79  : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
80  { }
81 
82  /** Initialize the iterator to reference the sequence pointed to
83  * by @p __seq. @p __constant is true when we are initializing a
84  * constant iterator, and false if it is a mutable iterator. Note
85  * that @p __seq may be NULL, in which case the iterator will be
86  * singular. Otherwise, the iterator will reference @p __seq and
87  * be nonsingular.
88  */
89  _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
90  : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
91  { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
92 
93  /** Initializes the iterator to reference the same sequence that
94  @p __x does. @p __constant is true if this is a constant
95  iterator, and false if it is mutable. */
96  _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
97  : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
98  { this->_M_attach(__x._M_sequence, __constant); }
99 
100  ~_Safe_iterator_base() { this->_M_detach(); }
101 
102  /** For use in _Safe_iterator. */
103  __gnu_cxx::__mutex&
104  _M_get_mutex() throw ();
105 
106  /** Attaches this iterator to the given sequence, detaching it
107  * from whatever sequence it was attached to originally. If the
108  * new sequence is the NULL pointer, the iterator is left
109  * unattached.
110  */
111  void
112  _M_attach(_Safe_sequence_base* __seq, bool __constant);
113 
114  /** Likewise, but not thread-safe. */
115  void
116  _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
117 
118  /** Detach the iterator for whatever sequence it is attached to,
119  * if any.
120  */
121  void
123 
124  public:
125  /** Likewise, but not thread-safe. */
126  void
127  _M_detach_single() throw ();
128 
129  /** Determines if we are attached to the given sequence. */
130  bool
132  { return _M_sequence == __seq; }
133 
134  /** Is this iterator singular? */
135  _GLIBCXX_PURE bool
136  _M_singular() const throw ();
137 
138  /** Can we compare this iterator to the given iterator @p __x?
139  Returns true if both iterators are nonsingular and reference
140  the same sequence. */
141  _GLIBCXX_PURE bool
142  _M_can_compare(const _Safe_iterator_base& __x) const throw ();
143 
144  /** Invalidate the iterator, making it singular. */
145  void
147  { _M_version = 0; }
148 
149  /** Reset all member variables */
150  void
151  _M_reset() throw ();
152 
153  /** Unlink itself */
154  void
155  _M_unlink() throw ()
156  {
157  if (_M_prior)
159  if (_M_next)
161  }
162  };
163 
164  /** Iterators that derive from _Safe_iterator_base can be determined singular
165  * or non-singular.
166  **/
167  inline bool
169  { return __x->_M_singular(); }
170 
171  /**
172  * @brief Base class that supports tracking of iterators that
173  * reference a sequence.
174  *
175  * The %_Safe_sequence_base class provides basic support for
176  * tracking iterators into a sequence. Sequences that track
177  * iterators must derived from %_Safe_sequence_base publicly, so
178  * that safe iterators (which inherit _Safe_iterator_base) can
179  * attach to them. This class contains two linked lists of
180  * iterators, one for constant iterators and one for mutable
181  * iterators, and a version number that allows very fast
182  * invalidation of all iterators that reference the container.
183  *
184  * This class must ensure that no operation on it may throw an
185  * exception, otherwise @a safe sequences may fail to provide the
186  * exception-safety guarantees required by the C++ standard.
187  */
189  {
190  friend class _Safe_iterator_base;
191 
192  public:
193  /// The list of mutable iterators that reference this container
195 
196  /// The list of constant iterators that reference this container
198 
199  /// The container version number. This number may never be 0.
200  mutable unsigned int _M_version;
201 
202  protected:
203  // Initialize with a version number of 1 and no iterators
204  _Safe_sequence_base() _GLIBCXX_NOEXCEPT
206  { }
207 
208 #if __cplusplus >= 201103L
210  : _Safe_sequence_base() { }
211 
212  // Move constructor swap iterators.
213  _Safe_sequence_base(_Safe_sequence_base&& __seq) noexcept
214  : _Safe_sequence_base()
215  { _M_swap(__seq); }
216 #endif
217 
218  /** Notify all iterators that reference this sequence that the
219  sequence is being destroyed. */
221  { this->_M_detach_all(); }
222 
223  /** Detach all iterators, leaving them singular. */
224  void
226 
227  /** Detach all singular iterators.
228  * @post for all iterators i attached to this sequence,
229  * i->_M_version == _M_version.
230  */
231  void
233 
234  /** Revalidates all attached singular iterators. This method may
235  * be used to validate iterators that were invalidated before
236  * (but for some reason, such as an exception, need to become
237  * valid again).
238  */
239  void
241 
242  /** Swap this sequence with the given sequence. This operation
243  * also swaps ownership of the iterators, so that when the
244  * operation is complete all iterators that originally referenced
245  * one container now reference the other container.
246  */
247  void
248  _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT;
249 
250  /** For use in _Safe_sequence. */
251  __gnu_cxx::__mutex&
252  _M_get_mutex() throw ();
253 
254  /** Invalidates all iterators. */
255  void
257  { if (++_M_version == 0) _M_version = 1; }
258 
259  private:
260  /** Attach an iterator to this sequence. */
261  void
262  _M_attach(_Safe_iterator_base* __it, bool __constant);
263 
264  /** Likewise but not thread safe. */
265  void
266  _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
267 
268  /** Detach an iterator from this sequence */
269  void
270  _M_detach(_Safe_iterator_base* __it);
271 
272  /** Likewise but not thread safe. */
273  void
274  _M_detach_single(_Safe_iterator_base* __it) throw ();
275  };
276 } // namespace __gnu_debug
277 
278 #endif
GNU debug classes for public use.
bool __check_singular_aux(const _Safe_iterator_base *__x)
Definition: safe_base.h:168
Basic functionality for a safe iterator.
Definition: safe_base.h:51
_Safe_iterator_base(const _Safe_iterator_base &__x, bool __constant)
Definition: safe_base.h:96
_Safe_sequence_base * _M_sequence
Definition: safe_base.h:57
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:131
_Safe_iterator_base(const _Safe_sequence_base *__seq, bool __constant)
Definition: safe_base.h:89
__gnu_cxx::__mutex & _M_get_mutex()
_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
Base class that supports tracking of iterators that reference a sequence.
Definition: safe_base.h:189
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:197
_Safe_iterator_base * _M_iterators
The list of mutable iterators that reference this container.
Definition: safe_base.h:194
__gnu_cxx::__mutex & _M_get_mutex()
unsigned int _M_version
The container version number. This number may never be 0.
Definition: safe_base.h:200