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

   1 // Safe sequence/iterator base implementation  -*- C++ -*-
   2
   3 // Copyright (C) 2003, 2004, 2005, 2006, 2009, 2010, 2011
   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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
  18 // permissions described in the GCC Runtime Library Exception, version
  19 // 3.1, as published by the Free Software Foundation.
  20
  21 // You should have received a copy of the GNU General Public License and
  22 // a copy of the GCC Runtime Library Exception along with this program;
  23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 // <http://www.gnu.org/licenses/>.
  25
  26 /** @file debug/safe_base.h
  27  *  This file is a GNU debug extension to the Standard C++ Library.
  28  */
  29
  30 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H
  31 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1
  32
  33 #include <ext/concurrence.h>
  34
  35 namespace __gnu_debug
  36 {
  37   class _Safe_sequence_base;
  38
  39   /** \brief Basic functionality for a @a safe iterator.
  40    *
  41    *  The %_Safe_iterator_base base class implements the functionality
  42    *  of a safe iterator that is not specific to a particular iterator
  43    *  type. It contains a pointer back to the sequence it references
  44    *  along with iterator version information and pointers to form a
  45    *  doubly-linked list of iterators referenced by the container.
  46    *
  47    *  This class must not perform any operations that can throw an
  48    *  exception, or the exception guarantees of derived iterators will
  49    *  be broken.
  50    */
  51   class _Safe_iterator_base
  52   {
  53   public:
  54     /** The sequence this iterator references; may be NULL to indicate
  55         a singular iterator. */
  56     _Safe_sequence_base* _M_sequence;
  57
  58     /** The version number of this iterator. The sentinel value 0 is
  59      *  used to indicate an invalidated iterator (i.e., one that is
  60      *  singular because of an operation on the container). This
  61      *  version number must equal the version number in the sequence
  62      *  referenced by _M_sequence for the iterator to be
  63      *  non-singular.
  64      */
  65     unsigned int         _M_version;
  66
  67     /** Pointer to the previous iterator in the sequence's list of
  68         iterators. Only valid when _M_sequence != NULL. */
  69     _Safe_iterator_base* _M_prior;
  70
  71     /** Pointer to the next iterator in the sequence's list of
  72         iterators. Only valid when _M_sequence != NULL. */
  73     _Safe_iterator_base* _M_next;
  74
  75   protected:
  76     /** Initializes the iterator and makes it singular. */
  77     _Safe_iterator_base()
  78     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
  79     { }
  80
  81     /** Initialize the iterator to reference the sequence pointed to
  82      *  by @p __seq. @p __constant is true when we are initializing a
  83      *  constant iterator, and false if it is a mutable iterator. Note
  84      *  that @p __seq may be NULL, in which case the iterator will be
  85      *  singular. Otherwise, the iterator will reference @p __seq and
  86      *  be nonsingular.
  87      */
  88     _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
  89     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
  90     { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
  91
  92     /** Initializes the iterator to reference the same sequence that
  93         @p __x does. @p __constant is true if this is a constant
  94         iterator, and false if it is mutable. */
  95     _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
  96     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
  97     { this->_M_attach(__x._M_sequence, __constant); }
  98
  99     _Safe_iterator_base&
 100     operator=(const _Safe_iterator_base&);
 101
 102     explicit
 103     _Safe_iterator_base(const _Safe_iterator_base&);
 104
 105     ~_Safe_iterator_base() { this->_M_detach(); }
 106
 107     /** For use in _Safe_iterator. */
 108     __gnu_cxx::__mutex& _M_get_mutex() throw ();
 109
 110   public:
 111     /** Attaches this iterator to the given sequence, detaching it
 112      *  from whatever sequence it was attached to originally. If the
 113      *  new sequence is the NULL pointer, the iterator is left
 114      *  unattached.
 115      */
 116     void _M_attach(_Safe_sequence_base* __seq, bool __constant);
 117
 118     /** Likewise, but not thread-safe. */
 119     void _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
 120
 121     /** Detach the iterator for whatever sequence it is attached to,
 122      *  if any.
 123     */
 124     void _M_detach();
 125
 126     /** Likewise, but not thread-safe. */
 127     void _M_detach_single() throw ();
 128
 129     /** Determines if we are attached to the given sequence. */
 130     bool _M_attached_to(const _Safe_sequence_base* __seq) const
 131     { return _M_sequence == __seq; }
 132
 133     /** Is this iterator singular? */
 134     _GLIBCXX_PURE bool _M_singular() const throw ();
 135
 136     /** Can we compare this iterator to the given iterator @p __x?
 137         Returns true if both iterators are nonsingular and reference
 138         the same sequence. */
 139     _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw ();
 140
 141     /** Invalidate the iterator, making it singular. */
 142     void
 143     _M_invalidate()
 144     { _M_version = 0; }
 145
 146     /** Reset all member variables */
 147     void
 148     _M_reset() throw ();
 149
 150     /** Unlink itself */
 151     void
 152     _M_unlink() throw ()
 153     {
 154       if (_M_prior)
 155         _M_prior->_M_next = _M_next;
 156       if (_M_next)
 157         _M_next->_M_prior = _M_prior;
 158     }
 159   };
 160
 161   /**
 162    * @brief Base class that supports tracking of iterators that
 163    * reference a sequence.
 164    *
 165    * The %_Safe_sequence_base class provides basic support for
 166    * tracking iterators into a sequence. Sequences that track
 167    * iterators must derived from %_Safe_sequence_base publicly, so
 168    * that safe iterators (which inherit _Safe_iterator_base) can
 169    * attach to them. This class contains two linked lists of
 170    * iterators, one for constant iterators and one for mutable
 171    * iterators, and a version number that allows very fast
 172    * invalidation of all iterators that reference the container.
 173    *
 174    * This class must ensure that no operation on it may throw an
 175    * exception, otherwise @a safe sequences may fail to provide the
 176    * exception-safety guarantees required by the C++ standard.
 177    */
 178   class _Safe_sequence_base
 179   {
 180   public:
 181     /// The list of mutable iterators that reference this container
 182     _Safe_iterator_base* _M_iterators;
 183
 184     /// The list of constant iterators that reference this container
 185     _Safe_iterator_base* _M_const_iterators;
 186
 187     /// The container version number. This number may never be 0.
 188     mutable unsigned int _M_version;
 189
 190   protected:
 191     // Initialize with a version number of 1 and no iterators
 192     _Safe_sequence_base()
 193     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
 194     { }
 195
 196     /** Notify all iterators that reference this sequence that the
 197         sequence is being destroyed. */
 198     ~_Safe_sequence_base()
 199     { this->_M_detach_all(); }
 200
 201     /** Detach all iterators, leaving them singular. */
 202     void
 203     _M_detach_all();
 204
 205     /** Detach all singular iterators.
 206      *  @post for all iterators i attached to this sequence,
 207      *   i->_M_version == _M_version.
 208      */
 209     void
 210     _M_detach_singular();
 211
 212     /** Revalidates all attached singular iterators.  This method may
 213      *  be used to validate iterators that were invalidated before
 214      *  (but for some reason, such as an exception, need to become
 215      *  valid again).
 216      */
 217     void
 218     _M_revalidate_singular();
 219
 220     /** Swap this sequence with the given sequence. This operation
 221      *  also swaps ownership of the iterators, so that when the
 222      *  operation is complete all iterators that originally referenced
 223      *  one container now reference the other container.
 224      */
 225     void
 226     _M_swap(_Safe_sequence_base& __x);
 227
 228     /** For use in _Safe_sequence. */
 229     __gnu_cxx::__mutex& _M_get_mutex() throw ();
 230
 231   public:
 232     /** Invalidates all iterators. */
 233     void
 234     _M_invalidate_all() const
 235     { if (++_M_version == 0) _M_version = 1; }
 236
 237     /** Attach an iterator to this sequence. */
 238     void
 239     _M_attach(_Safe_iterator_base* __it, bool __constant);
 240
 241     /** Likewise but not thread safe. */
 242     void
 243     _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
 244
 245     /** Detach an iterator from this sequence */
 246     void
 247     _M_detach(_Safe_iterator_base* __it);
 248
 249     /** Likewise but not thread safe. */
 250     void
 251     _M_detach_single(_Safe_iterator_base* __it) throw ();
 252   };
 253 } // namespace __gnu_debug
 254
 255 #endif