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
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   */
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
255