# safe_base.h

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    00001 // Safe sequence/iterator base implementation  -*- C++ -*-
    00002
    00003 // Copyright (C) 2003, 2004, 2005, 2006, 2009, 2010
    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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
    00018 // permissions described in the GCC Runtime Library Exception, version
    00019 // 3.1, as published by the Free Software Foundation.
    00020
    00021 // You should have received a copy of the GNU General Public License and
    00022 // a copy of the GCC Runtime Library Exception along with this program;
    00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    00024 // <http://www.gnu.org/licenses/>.
    00025
    00026 /** @file debug/safe_base.h
    00027  *  This file is a GNU debug extension to the Standard C++ Library.
    00028  */
    00029
    00030 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H
    00031 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1
    00032
    00033 #include <ext/concurrence.h>
    00034
    00035 namespace __gnu_debug
    00036 {
    00037   class _Safe_sequence_base;
    00038
    00039   /** \brief Basic functionality for a @a safe iterator.
    00040    *
    00041    *  The %_Safe_iterator_base base class implements the functionality
    00042    *  of a safe iterator that is not specific to a particular iterator
    00043    *  type. It contains a pointer back to the sequence it references
    00044    *  along with iterator version information and pointers to form a
    00045    *  doubly-linked list of iterators referenced by the container.
    00046    *
    00047    *  This class must not perform any operations that can throw an
    00048    *  exception, or the exception guarantees of derived iterators will
    00049    *  be broken.
    00050    */
    00051   class _Safe_iterator_base
    00052   {
    00053   public:
    00054     /** The sequence this iterator references; may be NULL to indicate
    00055     a singular iterator. */
    00056     _Safe_sequence_base* _M_sequence;
    00057
    00058     /** The version number of this iterator. The sentinel value 0 is
    00059      *  used to indicate an invalidated iterator (i.e., one that is
    00060      *  singular because of an operation on the container). This
    00061      *  version number must equal the version number in the sequence
    00062      *  referenced by _M_sequence for the iterator to be
    00063      *  non-singular.
    00064      */
    00065     unsigned int         _M_version;
    00066
    00067     /** Pointer to the previous iterator in the sequence's list of
    00068     iterators. Only valid when _M_sequence != NULL. */
    00069     _Safe_iterator_base* _M_prior;
    00070
    00071     /** Pointer to the next iterator in the sequence's list of
    00072     iterators. Only valid when _M_sequence != NULL. */
    00073     _Safe_iterator_base* _M_next;
    00074
    00075   protected:
    00076     /** Initializes the iterator and makes it singular. */
    00077     _Safe_iterator_base()
    00078     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
    00079     { }
    00080
    00081     /** Initialize the iterator to reference the sequence pointed to
    00082      *  by @p__seq. @p __constant is true when we are initializing a
    00083      *  constant iterator, and false if it is a mutable iterator. Note
    00084      *  that @p __seq may be NULL, in which case the iterator will be
    00085      *  singular. Otherwise, the iterator will reference @p __seq and
    00086      *  be nonsingular.
    00087      */
    00088     _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
    00089     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
    00090     { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
    00091
    00092     /** Initializes the iterator to reference the same sequence that
    00093     @p __x does. @p __constant is true if this is a constant
    00094     iterator, and false if it is mutable. */
    00095     _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
    00096     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
    00097     { this->_M_attach(__x._M_sequence, __constant); }
    00098
    00099     _Safe_iterator_base&
    00100     operator=(const _Safe_iterator_base&);
    00101
    00102     explicit
    00103     _Safe_iterator_base(const _Safe_iterator_base&);
    00104
    00105     ~_Safe_iterator_base() { this->_M_detach(); }
    00106
    00107     /** For use in _Safe_iterator. */
    00108     __gnu_cxx::__mutex& _M_get_mutex() throw ();
    00109
    00110   public:
    00111     /** Attaches this iterator to the given sequence, detaching it
    00112      *  from whatever sequence it was attached to originally. If the
    00113      *  new sequence is the NULL pointer, the iterator is left
    00114      *  unattached.
    00115      */
    00116     void _M_attach(_Safe_sequence_base* __seq, bool __constant);
    00117
    00118     /** Likewise, but not thread-safe. */
    00119     void _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
    00120
    00121     /** Detach the iterator for whatever sequence it is attached to,
    00122      *  if any.
    00123     */
    00124     void _M_detach();
    00125
    00126     /** Likewise, but not thread-safe. */
    00127     void _M_detach_single() throw ();
    00128
    00129     /** Determines if we are attached to the given sequence. */
    00130     bool _M_attached_to(const _Safe_sequence_base* __seq) const
    00131     { return _M_sequence == __seq; }
    00132
    00133     /** Is this iterator singular? */
    00134     _GLIBCXX_PURE bool _M_singular() const throw ();
    00135
    00136     /** Can we compare this iterator to the given iterator @p __x?
    00137     Returns true if both iterators are nonsingular and reference
    00138     the same sequence. */
    00139     _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw ();
    00140   };
    00141
    00142   /**
    00143    * @brief Base class that supports tracking of iterators that
    00144    * reference a sequence.
    00145    *
    00146    * The %_Safe_sequence_base class provides basic support for
    00147    * tracking iterators into a sequence. Sequences that track
    00148    * iterators must derived from %_Safe_sequence_base publicly, so
    00149    * that safe iterators (which inherit _Safe_iterator_base) can
    00150    * attach to them. This class contains two linked lists of
    00151    * iterators, one for constant iterators and one for mutable
    00152    * iterators, and a version number that allows very fast
    00153    * invalidation of all iterators that reference the container.
    00154    *
    00155    * This class must ensure that no operation on it may throw an
    00156    * exception, otherwise @a safe sequences may fail to provide the
    00157    * exception-safety guarantees required by the C++ standard.
    00158    */
    00159   class _Safe_sequence_base
    00160   {
    00161   public:
    00162     /// The list of mutable iterators that reference this container
    00163     _Safe_iterator_base* _M_iterators;
    00164
    00165     /// The list of constant iterators that reference this container
    00166     _Safe_iterator_base* _M_const_iterators;
    00167
    00168     /// The container version number. This number may never be 0.
    00169     mutable unsigned int _M_version;
    00170
    00171   protected:
    00172     // Initialize with a version number of 1 and no iterators
    00173     _Safe_sequence_base()
    00174     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
    00175     { }
    00176
    00177     /** Notify all iterators that reference this sequence that the
    00178     sequence is being destroyed. */
    00179     ~_Safe_sequence_base()
    00180     { this->_M_detach_all(); }
    00181
    00182     /** Detach all iterators, leaving them singular. */
    00183     void
    00184     _M_detach_all();
    00185
    00186     /** Detach all singular iterators.
    00187      *  @post for all iterators i attached to this sequence,
    00188      *   i->_M_version == _M_version.
    00189      */
    00190     void
    00191     _M_detach_singular();
    00192
    00193     /** Revalidates all attached singular iterators.  This method may
    00194      *  be used to validate iterators that were invalidated before
    00195      *  (but for some reason, such as an exception, need to become
    00196      *  valid again).
    00197      */
    00198     void
    00199     _M_revalidate_singular();
    00200
    00201     /** Swap this sequence with the given sequence. This operation
    00202      *  also swaps ownership of the iterators, so that when the
    00203      *  operation is complete all iterators that originally referenced
    00204      *  one container now reference the other container.
    00205      */
    00206     void
    00207     _M_swap(_Safe_sequence_base& __x);
    00208
    00209     /** For use in _Safe_sequence. */
    00210     __gnu_cxx::__mutex& _M_get_mutex() throw ();
    00211
    00212   public:
    00213     /** Invalidates all iterators. */
    00214     void
    00215     _M_invalidate_all() const
    00216     { if (++_M_version == 0) _M_version = 1; }
    00217   };
    00218 } // namespace __gnu_debug
    00219
    00220 #endif