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

   1 // Safe sequence/iterator base implementation  -*- C++ -*-
   2
   3 // Copyright (C) 2003
   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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  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 __gnu_debug
  35 {
  36   class _Safe_sequence_base;
  37
  38   /** \brief Basic functionality for 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() { this->_M_detach(); }
  99
 100   public:
 101     /** Attaches this iterator to the given sequence, detaching it
 102      *  from whatever sequence it was attached to originally. If the
 103      *  new sequence is the NULL pointer, the iterator is left
 104      *  unattached.
 105      */
 106     void _M_attach(_Safe_sequence_base* __seq, bool __constant);
 107
 108     /** Detach the iterator for whatever sequence it is attached to,
 109      *  if any.
 110     */
 111     void _M_detach();
 112
 113     /** Determines if we are attached to the given sequence. */
 114     bool _M_attached_to(const _Safe_sequence_base* __seq) const
 115     { return _M_sequence == __seq; }
 116
 117     /** Is this iterator singular? */
 118     bool _M_singular() const;
 119
 120     /** Can we compare this iterator to the given iterator @p __x?
 121         Returns true if both iterators are nonsingular and reference
 122         the same sequence. */
 123     bool _M_can_compare(const _Safe_iterator_base& __x) const;
 124   };
 125
 126   /**
 127    * @brief Base class that supports tracking of iterators that
 128    * reference a sequence.
 129    *
 130    * The %_Safe_sequence_base class provides basic support for
 131    * tracking iterators into a sequence. Sequences that track
 132    * iterators must derived from %_Safe_sequence_base publicly, so
 133    * that safe iterators (which inherit _Safe_iterator_base) can
 134    * attach to them. This class contains two linked lists of
 135    * iterators, one for constant iterators and one for mutable
 136    * iterators, and a version number that allows very fast
 137    * invalidation of all iterators that reference the container.
 138    *
 139    * This class must ensure that no operation on it may throw an
 140    * exception, otherwise "safe" sequences may fail to provide the
 141    * exception-safety guarantees required by the C++ standard.
 142    */
 143   class _Safe_sequence_base
 144   {
 145   public:
 146     /// The list of mutable iterators that reference this container
 147     _Safe_iterator_base* _M_iterators;
 148
 149     /// The list of constant iterators that reference this container
 150     _Safe_iterator_base* _M_const_iterators;
 151
 152     /// The container version number. This number may never be 0.
 153     mutable unsigned int _M_version;
 154
 155   protected:
 156     // Initialize with a version number of 1 and no iterators
 157     _Safe_sequence_base()
 158     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
 159     { }
 160
 161     /** Notify all iterators that reference this sequence that the
 162         sequence is being destroyed. */
 163     ~_Safe_sequence_base()
 164     { this->_M_detach_all(); }
 165
 166     /** Detach all iterators, leaving them singular. */
 167     void
 168     _M_detach_all();
 169
 170     /** Detach all singular iterators.
 171      *  @post for all iterators i attached to this sequence,
 172      *   i->_M_version == _M_version.
 173      */
 174     void
 175     _M_detach_singular();
 176
 177     /** Revalidates all attached singular iterators.  This method may
 178      *  be used to validate iterators that were invalidated before
 179      *  (but for some reasion, such as an exception, need to become
 180      *  valid again).
 181      */
 182     void
 183     _M_revalidate_singular();
 184
 185     /** Swap this sequence with the given sequence. This operation
 186      *  also swaps ownership of the iterators, so that when the
 187      *  operation is complete all iterators that originally referenced
 188      *  one container now reference the other container.
 189      */
 190     void
 191     _M_swap(_Safe_sequence_base& __x);
 192
 193   public:
 194     /** Invalidates all iterators. */
 195     void
 196     _M_invalidate_all() const
 197     { if (++_M_version == 0) _M_version = 1; }
 198   };
 199 } // namespace __gnu_debug
 200
 201 #endif