# safe_base.h

    00001 // Safe sequence/iterator base implementation  -*- C++ -*-
    00002
    00003 // Copyright (C) 2003, 2004
    00004 // Free Software Foundation, Inc.
    00005 //
    00006 // This file is part of the GNU ISO C++ Library.  This library is free
    00007 // software; you can redistribute it and/or modify it under the
    00008 // terms of the GNU General Public License as published by the
    00009 // Free Software Foundation; either version 2, or (at your option)
    00010 // any later version.
    00011
    00012 // This library is distributed in the hope that it will be useful,
    00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00015 // GNU General Public License for more details.
    00016
    00017 // You should have received a copy of the GNU General Public License along
    00018 // with this library; see the file COPYING.  If not, write to the Free
    00019 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
    00020 // USA.
    00021
    00022 // As a special exception, you may use this file as part of a free software
    00023 // library without restriction.  Specifically, if other files instantiate
    00024 // templates or use macros or inline functions from this file, or you compile
    00025 // this file and link it with other files to produce an executable, this
    00026 // file does not by itself cause the resulting executable to be covered by
    00027 // the GNU General Public License.  This exception does not however
    00028 // invalidate any other reasons why the executable file might be covered by
    00029 // the GNU General Public License.
    00030
    00031 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H
    00032 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1
    00033
    00034 namespace __gnu_debug
    00035 {
    00036   class _Safe_sequence_base;
    00037
    00038   /** \brief Basic functionality for a "safe" iterator.
    00039    *
    00040    *  The %_Safe_iterator_base base class implements the functionality
    00041    *  of a safe iterator that is not specific to a particular iterator
    00042    *  type. It contains a pointer back to the sequence it references
    00043    *  along with iterator version information and pointers to form a
    00044    *  doubly-linked list of iterators referenced by the container.
    00045    *
    00046    *  This class must not perform any operations that can throw an
    00047    *  exception, or the exception guarantees of derived iterators will
    00048    *  be broken.
    00049    */
    00050   class _Safe_iterator_base
    00051   {
    00052   public:
    00053     /** The sequence this iterator references; may be NULL to indicate
    00054     a singular iterator. */
    00055     _Safe_sequence_base* _M_sequence;
    00056
    00057     /** The version number of this iterator. The sentinel value 0 is
    00058      *  used to indicate an invalidated iterator (i.e., one that is
    00059      *  singular because of an operation on the container). This
    00060      *  version number must equal the version number in the sequence
    00061      *  referenced by _M_sequence for the iterator to be
    00062      *  non-singular.
    00063      */
    00064     unsigned int         _M_version;
    00065
    00066     /** Pointer to the previous iterator in the sequence's list of
    00067     iterators. Only valid when _M_sequence != NULL. */
    00068     _Safe_iterator_base* _M_prior;
    00069
    00070     /** Pointer to the next iterator in the sequence's list of
    00071     iterators. Only valid when _M_sequence != NULL. */
    00072     _Safe_iterator_base* _M_next;
    00073
    00074   protected:
    00075     /** Initializes the iterator and makes it singular. */
    00076     _Safe_iterator_base()
    00077     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
    00078     { }
    00079
    00080     /** Initialize the iterator to reference the sequence pointed to
    00081      *  by @p__seq. @p __constant is true when we are initializing a
    00082      *  constant iterator, and false if it is a mutable iterator. Note
    00083      *  that @p __seq may be NULL, in which case the iterator will be
    00084      *  singular. Otherwise, the iterator will reference @p __seq and
    00085      *  be nonsingular.
    00086      */
    00087     _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
    00088     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
    00089     { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
    00090
    00091     /** Initializes the iterator to reference the same sequence that
    00092     @p __x does. @p __constant is true if this is a constant
    00093     iterator, and false if it is mutable. */
    00094     _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
    00095     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
    00096     { this->_M_attach(__x._M_sequence, __constant); }
    00097
    00098     _Safe_iterator_base&
    00099     operator=(const _Safe_iterator_base&);
    00100
    00101     explicit
    00102     _Safe_iterator_base(const _Safe_iterator_base&);
    00103
    00104     ~_Safe_iterator_base() { this->_M_detach(); }
    00105
    00106   public:
    00107     /** Attaches this iterator to the given sequence, detaching it
    00108      *  from whatever sequence it was attached to originally. If the
    00109      *  new sequence is the NULL pointer, the iterator is left
    00110      *  unattached.
    00111      */
    00112     void _M_attach(_Safe_sequence_base* __seq, bool __constant);
    00113
    00114     /** Detach the iterator for whatever sequence it is attached to,
    00115      *  if any.
    00116     */
    00117     void _M_detach();
    00118
    00119     /** Determines if we are attached to the given sequence. */
    00120     bool _M_attached_to(const _Safe_sequence_base* __seq) const
    00121     { return _M_sequence == __seq; }
    00122
    00123     /** Is this iterator singular? */
    00124     bool _M_singular() const;
    00125
    00126     /** Can we compare this iterator to the given iterator @p __x?
    00127     Returns true if both iterators are nonsingular and reference
    00128     the same sequence. */
    00129     bool _M_can_compare(const _Safe_iterator_base& __x) const;
    00130   };
    00131
    00132   /**
    00133    * @brief Base class that supports tracking of iterators that
    00134    * reference a sequence.
    00135    *
    00136    * The %_Safe_sequence_base class provides basic support for
    00137    * tracking iterators into a sequence. Sequences that track
    00138    * iterators must derived from %_Safe_sequence_base publicly, so
    00139    * that safe iterators (which inherit _Safe_iterator_base) can
    00140    * attach to them. This class contains two linked lists of
    00141    * iterators, one for constant iterators and one for mutable
    00142    * iterators, and a version number that allows very fast
    00143    * invalidation of all iterators that reference the container.
    00144    *
    00145    * This class must ensure that no operation on it may throw an
    00146    * exception, otherwise "safe" sequences may fail to provide the
    00147    * exception-safety guarantees required by the C++ standard.
    00148    */
    00149   class _Safe_sequence_base
    00150   {
    00151   public:
    00152     /// The list of mutable iterators that reference this container
    00153     _Safe_iterator_base* _M_iterators;
    00154
    00155     /// The list of constant iterators that reference this container
    00156     _Safe_iterator_base* _M_const_iterators;
    00157
    00158     /// The container version number. This number may never be 0.
    00159     mutable unsigned int _M_version;
    00160
    00161   protected:
    00162     // Initialize with a version number of 1 and no iterators
    00163     _Safe_sequence_base()
    00164     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
    00165     { }
    00166
    00167     explicit
    00168     _Safe_sequence_base(const _Safe_sequence_base&);
    00169
    00170     _Safe_sequence_base&
    00171     operator=(const _Safe_sequence_base&);
    00172
    00173     /** Notify all iterators that reference this sequence that the
    00174     sequence is being destroyed. */
    00175     ~_Safe_sequence_base()
    00176     { this->_M_detach_all(); }
    00177
    00178     /** Detach all iterators, leaving them singular. */
    00179     void
    00180     _M_detach_all();
    00181
    00182     /** Detach all singular iterators.
    00183      *  @post for all iterators i attached to this sequence,
    00184      *   i->_M_version == _M_version.
    00185      */
    00186     void
    00187     _M_detach_singular();
    00188
    00189     /** Revalidates all attached singular iterators.  This method may
    00190      *  be used to validate iterators that were invalidated before
    00191      *  (but for some reasion, such as an exception, need to become
    00192      *  valid again).
    00193      */
    00194     void
    00195     _M_revalidate_singular();
    00196
    00197     /** Swap this sequence with the given sequence. This operation
    00198      *  also swaps ownership of the iterators, so that when the
    00199      *  operation is complete all iterators that originally referenced
    00200      *  one container now reference the other container.
    00201      */
    00202     void
    00203     _M_swap(_Safe_sequence_base& __x);
    00204
    00205   public:
    00206     /** Invalidates all iterators. */
    00207     void
    00208     _M_invalidate_all() const
    00209     { if (++_M_version == 0) _M_version = 1; }
    00210   };
    00211 } // namespace __gnu_debug
    00212
    00213 #endif