libstdc++-v3/include/debug/safe_base.h

   1 // Safe sequence/iterator base implementation  -*- C++ -*-
   2
   3 // Copyright (C) 2003, 2004, 2005
   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 2, 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 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING.  If not, write to the Free
  19 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  20 // USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H
  32 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1
  33
  34 namespace std
  35 {
  36 namespace __gnu_debug
  37 {
  38   class _Safe_sequence_base;
  39
  40   /** \brief Basic functionality for a "safe" iterator.
  41    *
  42    *  The %_Safe_iterator_base base class implements the functionality
  43    *  of a safe iterator that is not specific to a particular iterator
  44    *  type. It contains a pointer back to the sequence it references
  45    *  along with iterator version information and pointers to form a
  46    *  doubly-linked list of iterators referenced by the container.
  47    *
  48    *  This class must not perform any operations that can throw an
  49    *  exception, or the exception guarantees of derived iterators will
  50    *  be broken.
  51    */
  52   class _Safe_iterator_base
  53   {
  54   public:
  55     /** The sequence this iterator references; may be NULL to indicate
  56         a singular iterator. */
  57     _Safe_sequence_base* _M_sequence;
  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. */
  70     _Safe_iterator_base* _M_prior;
  71
  72     /** Pointer to the next iterator in the sequence's list of
  73         iterators. Only valid when _M_sequence != NULL. */
  74     _Safe_iterator_base* _M_next;
  75
  76   protected:
  77     /** Initializes the iterator and makes it singular. */
  78     _Safe_iterator_base()
  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&
 101     operator=(const _Safe_iterator_base&);
 102
 103     explicit
 104     _Safe_iterator_base(const _Safe_iterator_base&);
 105
 106     ~_Safe_iterator_base() { this->_M_detach(); }
 107
 108   public:
 109     /** Attaches this iterator to the given sequence, detaching it
 110      *  from whatever sequence it was attached to originally. If the
 111      *  new sequence is the NULL pointer, the iterator is left
 112      *  unattached.
 113      */
 114     void _M_attach(_Safe_sequence_base* __seq, bool __constant);
 115
 116     /** Detach the iterator for whatever sequence it is attached to,
 117      *  if any.
 118     */
 119     void _M_detach();
 120
 121     /** Determines if we are attached to the given sequence. */
 122     bool _M_attached_to(const _Safe_sequence_base* __seq) const
 123     { return _M_sequence == __seq; }
 124
 125     /** Is this iterator singular? */
 126     bool _M_singular() const;
 127
 128     /** Can we compare this iterator to the given iterator @p __x?
 129         Returns true if both iterators are nonsingular and reference
 130         the same sequence. */
 131     bool _M_can_compare(const _Safe_iterator_base& __x) const;
 132   };
 133
 134   /**
 135    * @brief Base class that supports tracking of iterators that
 136    * reference a sequence.
 137    *
 138    * The %_Safe_sequence_base class provides basic support for
 139    * tracking iterators into a sequence. Sequences that track
 140    * iterators must derived from %_Safe_sequence_base publicly, so
 141    * that safe iterators (which inherit _Safe_iterator_base) can
 142    * attach to them. This class contains two linked lists of
 143    * iterators, one for constant iterators and one for mutable
 144    * iterators, and a version number that allows very fast
 145    * invalidation of all iterators that reference the container.
 146    *
 147    * This class must ensure that no operation on it may throw an
 148    * exception, otherwise "safe" sequences may fail to provide the
 149    * exception-safety guarantees required by the C++ standard.
 150    */
 151   class _Safe_sequence_base
 152   {
 153   public:
 154     /// The list of mutable iterators that reference this container
 155     _Safe_iterator_base* _M_iterators;
 156
 157     /// The list of constant iterators that reference this container
 158     _Safe_iterator_base* _M_const_iterators;
 159
 160     /// The container version number. This number may never be 0.
 161     mutable unsigned int _M_version;
 162
 163   protected:
 164     // Initialize with a version number of 1 and no iterators
 165     _Safe_sequence_base()
 166     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
 167     { }
 168
 169     /** Notify all iterators that reference this sequence that the
 170         sequence is being destroyed. */
 171     ~_Safe_sequence_base()
 172     { this->_M_detach_all(); }
 173
 174     /** Detach all iterators, leaving them singular. */
 175     void
 176     _M_detach_all();
 177
 178     /** Detach all singular iterators.
 179      *  @post for all iterators i attached to this sequence,
 180      *   i->_M_version == _M_version.
 181      */
 182     void
 183     _M_detach_singular();
 184
 185     /** Revalidates all attached singular iterators.  This method may
 186      *  be used to validate iterators that were invalidated before
 187      *  (but for some reasion, such as an exception, need to become
 188      *  valid again).
 189      */
 190     void
 191     _M_revalidate_singular();
 192
 193     /** Swap this sequence with the given sequence. This operation
 194      *  also swaps ownership of the iterators, so that when the
 195      *  operation is complete all iterators that originally referenced
 196      *  one container now reference the other container.
 197      */
 198     void
 199     _M_swap(_Safe_sequence_base& __x);
 200
 201   public:
 202     /** Invalidates all iterators. */
 203     void
 204     _M_invalidate_all() const
 205     { if (++_M_version == 0) _M_version = 1; }
 206   };
 207 } // namespace __gnu_debug
 208 } // namespace std
 209
 210 #endif