libstdc++
safe_base.h
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1 // Safe sequence/iterator base implementation -*- C++ -*-
2 
3 // Copyright (C) 2003, 2004, 2005, 2006, 2009, 2010
4 // Free Software Foundation, Inc.
5 //
6 // This file is part of the GNU ISO C++ Library. This library is free
7 // software; you can redistribute it and/or modify it under the
8 // terms of the GNU General Public License as published by the
9 // Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11 
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20 
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
25 
26 /** @file debug/safe_base.h
27  * This file is a GNU debug extension to the Standard C++ Library.
28  */
29 
30 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H
31 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1
32 
33 #include <ext/concurrence.h>
34 
35 namespace __gnu_debug
36 {
37  class _Safe_sequence_base;
38 
39  /** \brief Basic functionality for a @a safe iterator.
40  *
41  * The %_Safe_iterator_base base class implements the functionality
42  * of a safe iterator that is not specific to a particular iterator
43  * type. It contains a pointer back to the sequence it references
44  * along with iterator version information and pointers to form a
45  * doubly-linked list of iterators referenced by the container.
46  *
47  * This class must not perform any operations that can throw an
48  * exception, or the exception guarantees of derived iterators will
49  * be broken.
50  */
52  {
53  public:
54  /** The sequence this iterator references; may be NULL to indicate
55  a singular iterator. */
57 
58  /** The version number of this iterator. The sentinel value 0 is
59  * used to indicate an invalidated iterator (i.e., one that is
60  * singular because of an operation on the container). This
61  * version number must equal the version number in the sequence
62  * referenced by _M_sequence for the iterator to be
63  * non-singular.
64  */
65  unsigned int _M_version;
66 
67  /** Pointer to the previous iterator in the sequence's list of
68  iterators. Only valid when _M_sequence != NULL. */
70 
71  /** Pointer to the next iterator in the sequence's list of
72  iterators. Only valid when _M_sequence != NULL. */
74 
75  protected:
76  /** Initializes the iterator and makes it singular. */
78  : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
79  { }
80 
81  /** Initialize the iterator to reference the sequence pointed to
82  * by @p __seq. @p __constant is true when we are initializing a
83  * constant iterator, and false if it is a mutable iterator. Note
84  * that @p __seq may be NULL, in which case the iterator will be
85  * singular. Otherwise, the iterator will reference @p __seq and
86  * be nonsingular.
87  */
88  _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
89  : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
90  { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
91 
92  /** Initializes the iterator to reference the same sequence that
93  @p __x does. @p __constant is true if this is a constant
94  iterator, and false if it is mutable. */
95  _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
96  : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
97  { this->_M_attach(__x._M_sequence, __constant); }
98 
100  operator=(const _Safe_iterator_base&);
101 
102  explicit
104 
105  ~_Safe_iterator_base() { this->_M_detach(); }
106 
107  /** For use in _Safe_iterator. */
108  __gnu_cxx::__mutex& _M_get_mutex() throw ();
109 
110  public:
111  /** Attaches this iterator to the given sequence, detaching it
112  * from whatever sequence it was attached to originally. If the
113  * new sequence is the NULL pointer, the iterator is left
114  * unattached.
115  */
116  void _M_attach(_Safe_sequence_base* __seq, bool __constant);
117 
118  /** Likewise, but not thread-safe. */
119  void _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
120 
121  /** Detach the iterator for whatever sequence it is attached to,
122  * if any.
123  */
124  void _M_detach();
125 
126  /** Likewise, but not thread-safe. */
127  void _M_detach_single() throw ();
128 
129  /** Determines if we are attached to the given sequence. */
130  bool _M_attached_to(const _Safe_sequence_base* __seq) const
131  { return _M_sequence == __seq; }
132 
133  /** Is this iterator singular? */
134  _GLIBCXX_PURE bool _M_singular() const throw ();
135 
136  /** Can we compare this iterator to the given iterator @p __x?
137  Returns true if both iterators are nonsingular and reference
138  the same sequence. */
139  _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw ();
140 
141  /** Invalidate the iterator, making it singular. */
142  void
144  { _M_version = 0; }
145 
146  /** Reset all member variables */
147  void
148  _M_reset() throw ();
149 
150  /** Unlink itself */
151  void
152  _M_unlink() throw ()
153  {
154  if (_M_prior)
156  if (_M_next)
158  }
159  };
160 
161  /**
162  * @brief Base class that supports tracking of iterators that
163  * reference a sequence.
164  *
165  * The %_Safe_sequence_base class provides basic support for
166  * tracking iterators into a sequence. Sequences that track
167  * iterators must derived from %_Safe_sequence_base publicly, so
168  * that safe iterators (which inherit _Safe_iterator_base) can
169  * attach to them. This class contains two linked lists of
170  * iterators, one for constant iterators and one for mutable
171  * iterators, and a version number that allows very fast
172  * invalidation of all iterators that reference the container.
173  *
174  * This class must ensure that no operation on it may throw an
175  * exception, otherwise @a safe sequences may fail to provide the
176  * exception-safety guarantees required by the C++ standard.
177  */
179  {
180  public:
181  /// The list of mutable iterators that reference this container
183 
184  /// The list of constant iterators that reference this container
186 
187  /// The container version number. This number may never be 0.
188  mutable unsigned int _M_version;
189 
190  protected:
191  // Initialize with a version number of 1 and no iterators
194  { }
195 
196  /** Notify all iterators that reference this sequence that the
197  sequence is being destroyed. */
199  { this->_M_detach_all(); }
200 
201  /** Detach all iterators, leaving them singular. */
202  void
203  _M_detach_all();
204 
205  /** Detach all singular iterators.
206  * @post for all iterators i attached to this sequence,
207  * i->_M_version == _M_version.
208  */
209  void
211 
212  /** Revalidates all attached singular iterators. This method may
213  * be used to validate iterators that were invalidated before
214  * (but for some reason, such as an exception, need to become
215  * valid again).
216  */
217  void
219 
220  /** Swap this sequence with the given sequence. This operation
221  * also swaps ownership of the iterators, so that when the
222  * operation is complete all iterators that originally referenced
223  * one container now reference the other container.
224  */
225  void
227 
228  /** For use in _Safe_sequence. */
229  __gnu_cxx::__mutex& _M_get_mutex() throw ();
230 
231  public:
232  /** Invalidates all iterators. */
233  void
235  { if (++_M_version == 0) _M_version = 1; }
236 
237  /** Attach an iterator to this sequence. */
238  void
239  _M_attach(_Safe_iterator_base* __it, bool __constant);
240 
241  /** Likewise but not thread safe. */
242  void
243  _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
244 
245  /** Detach an iterator from this sequence */
246  void
248 
249  /** Likewise but not thread safe. */
250  void
251  _M_detach_single(_Safe_iterator_base* __it) throw ();
252  };
253 } // namespace __gnu_debug
254 
255 #endif