contrib/gcc-8.0/libstdc++-v3/include/debug/safe_base.h

   1 // Safe sequence/iterator base implementation  -*- C++ -*-
   2
   3 // Copyright (C) 2003-2018 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     friend class _Safe_sequence_base;
  53
  54   public:
  55     /** The sequence this iterator references; may be NULL to indicate
  56         a singular iterator. */
  57     _Safe_sequence_base*        _M_sequence;
  58
  59     /** The version number of this iterator. The sentinel value 0 is
  60      *  used to indicate an invalidated iterator (i.e., one that is
  61      *  singular because of an operation on the container). This
  62      *  version number must equal the version number in the sequence
  63      *  referenced by _M_sequence for the iterator to be
  64      *  non-singular.
  65      */
  66     unsigned int                _M_version;
  67
  68     /** Pointer to the previous iterator in the sequence's list of
  69         iterators. Only valid when _M_sequence != NULL. */
  70     _Safe_iterator_base*        _M_prior;
  71
  72     /** Pointer to the next iterator in the sequence's list of
  73         iterators. Only valid when _M_sequence != NULL. */
  74     _Safe_iterator_base*        _M_next;
  75
  76   protected:
  77     /** Initializes the iterator and makes it singular. */
  78     _Safe_iterator_base()
  79     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
  80     { }
  81
  82     /** Initialize the iterator to reference the sequence pointed to
  83      *  by @p __seq. @p __constant is true when we are initializing a
  84      *  constant iterator, and false if it is a mutable iterator. Note
  85      *  that @p __seq may be NULL, in which case the iterator will be
  86      *  singular. Otherwise, the iterator will reference @p __seq and
  87      *  be nonsingular.
  88      */
  89     _Safe_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
  90     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
  91     { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
  92
  93     /** Initializes the iterator to reference the same sequence that
  94         @p __x does. @p __constant is true if this is a constant
  95         iterator, and false if it is mutable. */
  96     _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)
  97     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
  98     { this->_M_attach(__x._M_sequence, __constant); }
  99
 100     ~_Safe_iterator_base() { this->_M_detach(); }
 101
 102     /** For use in _Safe_iterator. */
 103     __gnu_cxx::__mutex&
 104     _M_get_mutex() throw ();
 105
 106     /** Attaches this iterator to the given sequence, detaching it
 107      *  from whatever sequence it was attached to originally. If the
 108      *  new sequence is the NULL pointer, the iterator is left
 109      *  unattached.
 110      */
 111     void
 112     _M_attach(_Safe_sequence_base* __seq, bool __constant);
 113
 114     /** Likewise, but not thread-safe. */
 115     void
 116     _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
 117
 118     /** Detach the iterator for whatever sequence it is attached to,
 119      *  if any.
 120     */
 121     void
 122     _M_detach();
 123
 124   public:
 125     /** Likewise, but not thread-safe. */
 126     void
 127     _M_detach_single() throw ();
 128
 129     /** Determines if we are attached to the given sequence. */
 130     bool
 131     _M_attached_to(const _Safe_sequence_base* __seq) const
 132     { return _M_sequence == __seq; }
 133
 134     /** Is this iterator singular? */
 135     _GLIBCXX_PURE bool
 136     _M_singular() const throw ();
 137
 138     /** Can we compare this iterator to the given iterator @p __x?
 139         Returns true if both iterators are nonsingular and reference
 140         the same sequence. */
 141     _GLIBCXX_PURE bool
 142     _M_can_compare(const _Safe_iterator_base& __x) const throw ();
 143
 144     /** Invalidate the iterator, making it singular. */
 145     void
 146     _M_invalidate()
 147     { _M_version = 0; }
 148
 149     /** Reset all member variables */
 150     void
 151     _M_reset() throw ();
 152
 153     /** Unlink itself */
 154     void
 155     _M_unlink() throw ()
 156     {
 157       if (_M_prior)
 158         _M_prior->_M_next = _M_next;
 159       if (_M_next)
 160         _M_next->_M_prior = _M_prior;
 161     }
 162   };
 163
 164   /** Iterators that derive from _Safe_iterator_base can be determined singular
 165    *  or non-singular.
 166    **/
 167   inline bool
 168   __check_singular_aux(const _Safe_iterator_base* __x)
 169   { return __x->_M_singular(); }
 170
 171   /**
 172    * @brief Base class that supports tracking of iterators that
 173    * reference a sequence.
 174    *
 175    * The %_Safe_sequence_base class provides basic support for
 176    * tracking iterators into a sequence. Sequences that track
 177    * iterators must derived from %_Safe_sequence_base publicly, so
 178    * that safe iterators (which inherit _Safe_iterator_base) can
 179    * attach to them. This class contains two linked lists of
 180    * iterators, one for constant iterators and one for mutable
 181    * iterators, and a version number that allows very fast
 182    * invalidation of all iterators that reference the container.
 183    *
 184    * This class must ensure that no operation on it may throw an
 185    * exception, otherwise @a safe sequences may fail to provide the
 186    * exception-safety guarantees required by the C++ standard.
 187    */
 188   class _Safe_sequence_base
 189   {
 190     friend class _Safe_iterator_base;
 191
 192   public:
 193     /// The list of mutable iterators that reference this container
 194     _Safe_iterator_base* _M_iterators;
 195
 196     /// The list of constant iterators that reference this container
 197     _Safe_iterator_base* _M_const_iterators;
 198
 199     /// The container version number. This number may never be 0.
 200     mutable unsigned int _M_version;
 201
 202   protected:
 203     // Initialize with a version number of 1 and no iterators
 204     _Safe_sequence_base() _GLIBCXX_NOEXCEPT
 205     : _M_iterators(0), _M_const_iterators(0), _M_version(1)
 206     { }
 207
 208 #if __cplusplus >= 201103L
 209     _Safe_sequence_base(const _Safe_sequence_base&) noexcept
 210     : _Safe_sequence_base() { }
 211
 212     // Move constructor swap iterators.
 213     _Safe_sequence_base(_Safe_sequence_base&& __seq) noexcept
 214     : _Safe_sequence_base()
 215     { _M_swap(__seq); }
 216 #endif
 217
 218     /** Notify all iterators that reference this sequence that the
 219         sequence is being destroyed. */
 220     ~_Safe_sequence_base()
 221     { this->_M_detach_all(); }
 222
 223     /** Detach all iterators, leaving them singular. */
 224     void
 225     _M_detach_all();
 226
 227     /** Detach all singular iterators.
 228      *  @post for all iterators i attached to this sequence,
 229      *   i->_M_version == _M_version.
 230      */
 231     void
 232     _M_detach_singular();
 233
 234     /** Revalidates all attached singular iterators.  This method may
 235      *  be used to validate iterators that were invalidated before
 236      *  (but for some reason, such as an exception, need to become
 237      *  valid again).
 238      */
 239     void
 240     _M_revalidate_singular();
 241
 242     /** Swap this sequence with the given sequence. This operation
 243      *  also swaps ownership of the iterators, so that when the
 244      *  operation is complete all iterators that originally referenced
 245      *  one container now reference the other container.
 246      */
 247     void
 248     _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT;
 249
 250     /** For use in _Safe_sequence. */
 251     __gnu_cxx::__mutex&
 252     _M_get_mutex() throw ();
 253
 254     /** Invalidates all iterators. */
 255     void
 256     _M_invalidate_all() const
 257     { if (++_M_version == 0) _M_version = 1; }
 258
 259   private:
 260     /** Attach an iterator to this sequence. */
 261     void
 262     _M_attach(_Safe_iterator_base* __it, bool __constant);
 263
 264     /** Likewise but not thread safe. */
 265     void
 266     _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
 267
 268     /** Detach an iterator from this sequence */
 269     void
 270     _M_detach(_Safe_iterator_base* __it);
 271
 272     /** Likewise but not thread safe. */
 273     void
 274     _M_detach_single(_Safe_iterator_base* __it) throw ();
 275   };
 276 } // namespace __gnu_debug
 277
 278 #endif