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

   1 // Safe sequence/iterator base implementation  -*- C++ -*-
   2
   3 // Copyright (C) 2003-2014 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file debug/safe_base.h
  26  *  This file is a GNU debug extension to the Standard C++ Library.
  27  */
  28
  29 #ifndef _GLIBCXX_DEBUG_SAFE_BASE_H
  30 #define _GLIBCXX_DEBUG_SAFE_BASE_H 1
  31
  32 #include <ext/concurrence.h>
  33
  34 namespace __gnu_debug
  35 {
  36   class _Safe_sequence_base;
  37
  38   /** \brief Basic functionality for a @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     /** For use in _Safe_iterator. */
 101     __gnu_cxx::__mutex&
 102     _M_get_mutex() throw ();
 103
 104   public:
 105     /** Attaches this iterator to the given sequence, detaching it
 106      *  from whatever sequence it was attached to originally. If the
 107      *  new sequence is the NULL pointer, the iterator is left
 108      *  unattached.
 109      */
 110     void
 111     _M_attach(_Safe_sequence_base* __seq, bool __constant);
 112
 113     /** Likewise, but not thread-safe. */
 114     void
 115     _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
 116
 117     /** Detach the iterator for whatever sequence it is attached to,
 118      *  if any.
 119     */
 120     void
 121     _M_detach();
 122
 123     /** Likewise, but not thread-safe. */
 124     void
 125     _M_detach_single() throw ();
 126
 127     /** Determines if we are attached to the given sequence. */
 128     bool
 129     _M_attached_to(const _Safe_sequence_base* __seq) const
 130     { return _M_sequence == __seq; }
 131
 132     /** Is this iterator singular? */
 133     _GLIBCXX_PURE bool
 134     _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
 140     _M_can_compare(const _Safe_iterator_base& __x) const throw ();
 141
 142     /** Invalidate the iterator, making it singular. */
 143     void
 144     _M_invalidate()
 145     { _M_version = 0; }
 146
 147     /** Reset all member variables */
 148     void
 149     _M_reset() throw ();
 150
 151     /** Unlink itself */
 152     void
 153     _M_unlink() throw ()
 154     {
 155       if (_M_prior)
 156         _M_prior->_M_next = _M_next;
 157       if (_M_next)
 158         _M_next->_M_prior = _M_prior;
 159     }
 160   };
 161
 162   /**
 163    * @brief Base class that supports tracking of iterators that
 164    * reference a sequence.
 165    *
 166    * The %_Safe_sequence_base class provides basic support for
 167    * tracking iterators into a sequence. Sequences that track
 168    * iterators must derived from %_Safe_sequence_base publicly, so
 169    * that safe iterators (which inherit _Safe_iterator_base) can
 170    * attach to them. This class contains two linked lists of
 171    * iterators, one for constant iterators and one for mutable
 172    * iterators, and a version number that allows very fast
 173    * invalidation of all iterators that reference the container.
 174    *
 175    * This class must ensure that no operation on it may throw an
 176    * exception, otherwise @a safe sequences may fail to provide the
 177    * exception-safety guarantees required by the C++ standard.
 178    */
 179   class _Safe_sequence_base
 180   {
 181   public:
 182     /// The list of mutable iterators that reference this container
 183     _Safe_iterator_base* _M_iterators;
 184
 185     /// The list of constant iterators that reference this container
 186     _Safe_iterator_base* _M_const_iterators;
 187
 188     /// The container version number. This number may never be 0.
 189     mutable unsigned int _M_version;
 190
 191   protected:
 192     // Initialize with a version number of 1 and no iterators
 193     _Safe_sequence_base() _GLIBCXX_NOEXCEPT
 194     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
 195     { }
 196
 197 #if __cplusplus >= 201103L
 198     _Safe_sequence_base(const _Safe_sequence_base&) noexcept
 199     : _Safe_sequence_base() { }
 200 #endif
 201
 202     /** Notify all iterators that reference this sequence that the
 203         sequence is being destroyed. */
 204     ~_Safe_sequence_base()
 205     { this->_M_detach_all(); }
 206
 207     /** Detach all iterators, leaving them singular. */
 208     void
 209     _M_detach_all();
 210
 211     /** Detach all singular iterators.
 212      *  @post for all iterators i attached to this sequence,
 213      *   i->_M_version == _M_version.
 214      */
 215     void
 216     _M_detach_singular();
 217
 218     /** Revalidates all attached singular iterators.  This method may
 219      *  be used to validate iterators that were invalidated before
 220      *  (but for some reason, such as an exception, need to become
 221      *  valid again).
 222      */
 223     void
 224     _M_revalidate_singular();
 225
 226     /** Swap this sequence with the given sequence. This operation
 227      *  also swaps ownership of the iterators, so that when the
 228      *  operation is complete all iterators that originally referenced
 229      *  one container now reference the other container.
 230      */
 231     void
 232     _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT;
 233
 234     /** For use in _Safe_sequence. */
 235     __gnu_cxx::__mutex&
 236     _M_get_mutex() throw ();
 237
 238   public:
 239     /** Invalidates all iterators. */
 240     void
 241     _M_invalidate_all() const
 242     { if (++_M_version == 0) _M_version = 1; }
 243
 244     /** Attach an iterator to this sequence. */
 245     void
 246     _M_attach(_Safe_iterator_base* __it, bool __constant);
 247
 248     /** Likewise but not thread safe. */
 249     void
 250     _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
 251
 252     /** Detach an iterator from this sequence */
 253     void
 254     _M_detach(_Safe_iterator_base* __it);
 255
 256     /** Likewise but not thread safe. */
 257     void
 258     _M_detach_single(_Safe_iterator_base* __it) throw ();
 259   };
 260 } // namespace __gnu_debug
 261
 262 #endif