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&
  99     operator=(const _Safe_iterator_base&);
 100
 101     explicit
 102     _Safe_iterator_base(const _Safe_iterator_base&);
 103
 104     ~_Safe_iterator_base() { this->_M_detach(); }
 105
 106     /** For use in _Safe_iterator. */
 107     __gnu_cxx::__mutex&
 108     _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
 117     _M_attach(_Safe_sequence_base* __seq, bool __constant);
 118
 119     /** Likewise, but not thread-safe. */
 120     void
 121     _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
 122
 123     /** Detach the iterator for whatever sequence it is attached to,
 124      *  if any.
 125     */
 126     void
 127     _M_detach();
 128
 129     /** Likewise, but not thread-safe. */
 130     void
 131     _M_detach_single() throw ();
 132
 133     /** Determines if we are attached to the given sequence. */
 134     bool
 135     _M_attached_to(const _Safe_sequence_base* __seq) const
 136     { return _M_sequence == __seq; }
 137
 138     /** Is this iterator singular? */
 139     _GLIBCXX_PURE bool
 140     _M_singular() const throw ();
 141
 142     /** Can we compare this iterator to the given iterator @p __x?
 143         Returns true if both iterators are nonsingular and reference
 144         the same sequence. */
 145     _GLIBCXX_PURE bool
 146     _M_can_compare(const _Safe_iterator_base& __x) const throw ();
 147
 148     /** Invalidate the iterator, making it singular. */
 149     void
 150     _M_invalidate()
 151     { _M_version = 0; }
 152
 153     /** Reset all member variables */
 154     void
 155     _M_reset() throw ();
 156
 157     /** Unlink itself */
 158     void
 159     _M_unlink() throw ()
 160     {
 161       if (_M_prior)
 162         _M_prior->_M_next = _M_next;
 163       if (_M_next)
 164         _M_next->_M_prior = _M_prior;
 165     }
 166   };
 167
 168   /**
 169    * @brief Base class that supports tracking of iterators that
 170    * reference a sequence.
 171    *
 172    * The %_Safe_sequence_base class provides basic support for
 173    * tracking iterators into a sequence. Sequences that track
 174    * iterators must derived from %_Safe_sequence_base publicly, so
 175    * that safe iterators (which inherit _Safe_iterator_base) can
 176    * attach to them. This class contains two linked lists of
 177    * iterators, one for constant iterators and one for mutable
 178    * iterators, and a version number that allows very fast
 179    * invalidation of all iterators that reference the container.
 180    *
 181    * This class must ensure that no operation on it may throw an
 182    * exception, otherwise @a safe sequences may fail to provide the
 183    * exception-safety guarantees required by the C++ standard.
 184    */
 185   class _Safe_sequence_base
 186   {
 187   public:
 188     /// The list of mutable iterators that reference this container
 189     _Safe_iterator_base* _M_iterators;
 190
 191     /// The list of constant iterators that reference this container
 192     _Safe_iterator_base* _M_const_iterators;
 193
 194     /// The container version number. This number may never be 0.
 195     mutable unsigned int _M_version;
 196
 197   protected:
 198     // Initialize with a version number of 1 and no iterators
 199     _Safe_sequence_base() _GLIBCXX_NOEXCEPT
 200     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
 201     { }
 202
 203 #if __cplusplus >= 201103L
 204     _Safe_sequence_base(const _Safe_sequence_base&) noexcept
 205     : _Safe_sequence_base() { }
 206 #endif
 207
 208     /** Notify all iterators that reference this sequence that the
 209         sequence is being destroyed. */
 210     ~_Safe_sequence_base()
 211     { this->_M_detach_all(); }
 212
 213     /** Detach all iterators, leaving them singular. */
 214     void
 215     _M_detach_all();
 216
 217     /** Detach all singular iterators.
 218      *  @post for all iterators i attached to this sequence,
 219      *   i->_M_version == _M_version.
 220      */
 221     void
 222     _M_detach_singular();
 223
 224     /** Revalidates all attached singular iterators.  This method may
 225      *  be used to validate iterators that were invalidated before
 226      *  (but for some reason, such as an exception, need to become
 227      *  valid again).
 228      */
 229     void
 230     _M_revalidate_singular();
 231
 232     /** Swap this sequence with the given sequence. This operation
 233      *  also swaps ownership of the iterators, so that when the
 234      *  operation is complete all iterators that originally referenced
 235      *  one container now reference the other container.
 236      */
 237     void
 238     _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT;
 239
 240     /** For use in _Safe_sequence. */
 241     __gnu_cxx::__mutex&
 242     _M_get_mutex() throw ();
 243
 244   public:
 245     /** Invalidates all iterators. */
 246     void
 247     _M_invalidate_all() const
 248     { if (++_M_version == 0) _M_version = 1; }
 249
 250     /** Attach an iterator to this sequence. */
 251     void
 252     _M_attach(_Safe_iterator_base* __it, bool __constant);
 253
 254     /** Likewise but not thread safe. */
 255     void
 256     _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
 257
 258     /** Detach an iterator from this sequence */
 259     void
 260     _M_detach(_Safe_iterator_base* __it);
 261
 262     /** Likewise but not thread safe. */
 263     void
 264     _M_detach_single(_Safe_iterator_base* __it) throw ();
 265   };
 266 } // namespace __gnu_debug
 267
 268 #endif