libstdc++

safe_base.h
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1 // Safe sequence/iterator base implementation -*- C++ -*-
2
3 // Copyright (C) 2003-2013 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 */
50 class _Safe_iterator_base
51 {
52 public:
53 /** The sequence this iterator references; may be NULL to indicate
54 a singular iterator. */
55 _Safe_sequence_base* _M_sequence;
56
57 /** The version number of this iterator. The sentinel value 0 is
58 * used to indicate an invalidated iterator (i.e., one that is
59 * singular because of an operation on the container). This
60 * version number must equal the version number in the sequence
61 * referenced by _M_sequence for the iterator to be
62 * non-singular.
63 */
64 unsigned int _M_version;
65
66 /** Pointer to the previous iterator in the sequence's list of
67 iterators. Only valid when _M_sequence != NULL. */
68 _Safe_iterator_base* _M_prior;
69
70 /** Pointer to the next iterator in the sequence's list of
71 iterators. Only valid when _M_sequence != NULL. */
72 _Safe_iterator_base* _M_next;
73
74 protected:
75 /** Initializes the iterator and makes it singular. */
76 _Safe_iterator_base()
77 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
78 { }
79
80 /** Initialize the iterator to reference the sequence pointed to
81 * by @p __seq. @p __constant is true when we are initializing a
82 * constant iterator, and false if it is a mutable iterator. Note
83 * that @p __seq may be NULL, in which case the iterator will be
84 * singular. Otherwise, the iterator will reference @p __seq and
85 * be nonsingular.
86 */
87 _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
88 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
89 { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
90
91 /** Initializes the iterator to reference the same sequence that
92 @p __x does. @p __constant is true if this is a constant
93 iterator, and false if it is mutable. */
94 _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
95 : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
96 { this->_M_attach(__x._M_sequence, __constant); }
97
98 _Safe_iterator_base&
99 operator=(const _Safe_iterator_base&);
100
101 explicit
102 _Safe_iterator_base(const _Safe_iterator_base&);
103
104 ~_Safe_iterator_base() { this->_M_detach(); }
105
106 /** For use in _Safe_iterator. */
107 __gnu_cxx::__mutex& _M_get_mutex() throw ();
108
109 public:
110 /** Attaches this iterator to the given sequence, detaching it
111 * from whatever sequence it was attached to originally. If the
112 * new sequence is the NULL pointer, the iterator is left
113 * unattached.
114 */
115 void _M_attach(_Safe_sequence_base* __seq, bool __constant);
116
117 /** Likewise, but not thread-safe. */
118 void _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
119
120 /** Detach the iterator for whatever sequence it is attached to,
121 * if any.
122 */
123 void _M_detach();
124
125 /** Likewise, but not thread-safe. */
126 void _M_detach_single() throw ();
127
128 /** Determines if we are attached to the given sequence. */
129 bool _M_attached_to(const _Safe_sequence_base* __seq) const
130 { return _M_sequence == __seq; }
131
132 /** Is this iterator singular? */
133 _GLIBCXX_PURE bool _M_singular() const throw ();
134
135 /** Can we compare this iterator to the given iterator @p __x?
136 Returns true if both iterators are nonsingular and reference
137 the same sequence. */
138 _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw ();
139
140 /** Invalidate the iterator, making it singular. */
141 void
142 _M_invalidate()
143 { _M_version = 0; }
144
145 /** Reset all member variables */
146 void
147 _M_reset() throw ();
148
149 /** Unlink itself */
150 void
151 _M_unlink() throw ()
152 {
153 if (_M_prior)
154 _M_prior->_M_next = _M_next;
155 if (_M_next)
156 _M_next->_M_prior = _M_prior;
157 }
158 };
159
160 /**
161 * @brief Base class that supports tracking of iterators that
162 * reference a sequence.
163 *
164 * The %_Safe_sequence_base class provides basic support for
165 * tracking iterators into a sequence. Sequences that track
166 * iterators must derived from %_Safe_sequence_base publicly, so
167 * that safe iterators (which inherit _Safe_iterator_base) can
168 * attach to them. This class contains two linked lists of
169 * iterators, one for constant iterators and one for mutable
170 * iterators, and a version number that allows very fast
171 * invalidation of all iterators that reference the container.
172 *
173 * This class must ensure that no operation on it may throw an
174 * exception, otherwise @a safe sequences may fail to provide the
175 * exception-safety guarantees required by the C++ standard.
176 */
177 class _Safe_sequence_base
178 {
179 public:
180 /// The list of mutable iterators that reference this container
181 _Safe_iterator_base* _M_iterators;
182
183 /// The list of constant iterators that reference this container
184 _Safe_iterator_base* _M_const_iterators;
185
186 /// The container version number. This number may never be 0.
187 mutable unsigned int _M_version;
188
189 protected:
190 // Initialize with a version number of 1 and no iterators
191 _Safe_sequence_base()
192 : _M_iterators(0), _M_const_iterators(0), _M_version(1)
193 { }
194
195 /** Notify all iterators that reference this sequence that the
196 sequence is being destroyed. */
197 ~_Safe_sequence_base()
198 { this->_M_detach_all(); }
199
200 /** Detach all iterators, leaving them singular. */
201 void
202 _M_detach_all();
203
204 /** Detach all singular iterators.
205 * @post for all iterators i attached to this sequence,
206 * i->_M_version == _M_version.
207 */
208 void
209 _M_detach_singular();
210
211 /** Revalidates all attached singular iterators. This method may
212 * be used to validate iterators that were invalidated before
213 * (but for some reason, such as an exception, need to become
214 * valid again).
215 */
216 void
217 _M_revalidate_singular();
218
219 /** Swap this sequence with the given sequence. This operation
220 * also swaps ownership of the iterators, so that when the
221 * operation is complete all iterators that originally referenced
222 * one container now reference the other container.
223 */
224 void
225 _M_swap(_Safe_sequence_base& __x);
226
227 /** For use in _Safe_sequence. */
228 __gnu_cxx::__mutex& _M_get_mutex() throw ();
229
230 public:
231 /** Invalidates all iterators. */
232 void
233 _M_invalidate_all() const
234 { if (++_M_version == 0) _M_version = 1; }
235
236 /** Attach an iterator to this sequence. */
237 void
238 _M_attach(_Safe_iterator_base* __it, bool __constant);
239
240 /** Likewise but not thread safe. */
241 void
242 _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
243
244 /** Detach an iterator from this sequence */
245 void
246 _M_detach(_Safe_iterator_base* __it);
247
248 /** Likewise but not thread safe. */
249 void
250 _M_detach_single(_Safe_iterator_base* __it) throw ();
251 };
252 } // namespace __gnu_debug
253
254 #endif