text: // Safe container/iterator base implementation  -*- C++ -*-
  
  // Copyright (C) 2011-2013 Free Software Foundation, Inc.
  //
  // This file is part of the GNU ISO C++ Library.  This library is free
  // software; you can redistribute it and/or modify it under the
  // terms of the GNU General Public License as published by the
  // Free Software Foundation; either version 3, or (at your option)
  // any later version.
  
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  // GNU General Public License for more details.
  
  // Under Section 7 of GPL version 3, you are granted additional
  // permissions described in the GCC Runtime Library Exception, version
  // 3.1, as published by the Free Software Foundation.
  
  // You should have received a copy of the GNU General Public License and
  // a copy of the GCC Runtime Library Exception along with this program;
  // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  // <http://www.gnu.org/licenses/>.
  
  /** @file debug/safe_unordered_base.h
   *  This file is a GNU debug extension to the Standard C++ Library.
   */
  
  #ifndef _GLIBCXX_DEBUG_SAFE_UNORDERED_BASE_H
  #define _GLIBCXX_DEBUG_SAFE_UNORDERED_BASE_H 1
  
  #include <debug/safe_base.h>
  
  namespace __gnu_debug
  {
    class _Safe_unordered_container_base;
  
    /** \brief Basic functionality for a @a safe iterator.
     *
     *  The %_Safe_local_iterator_base base class implements the functionality
     *  of a safe local iterator that is not specific to a particular iterator
     *  type. It contains a pointer back to the container it references
     *  along with iterator version information and pointers to form a
     *  doubly-linked list of local iterators referenced by the container.
     *
     *  This class must not perform any operations that can throw an
     *  exception, or the exception guarantees of derived iterators will
     *  be broken.
     */
    class _Safe_local_iterator_base : public _Safe_iterator_base
    {
    protected:
      /** Initializes the iterator and makes it singular. */
      _Safe_local_iterator_base()
      { }
  
      /** Initialize the iterator to reference the container pointed to
       *  by @p __seq. @p __constant is true when we are initializing a
       *  constant local iterator, and false if it is a mutable local iterator.
       *  Note that @p __seq may be NULL, in which case the iterator will be
       *  singular. Otherwise, the iterator will reference @p __seq and
       *  be nonsingular.
       */
      _Safe_local_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
      { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
  
      /** Initializes the iterator to reference the same container that
  	@p __x does. @p __constant is true if this is a constant
  	iterator, and false if it is mutable. */
      _Safe_local_iterator_base(const _Safe_local_iterator_base& __x,
  			      bool __constant)
      { this->_M_attach(__x._M_sequence, __constant); }
  
      _Safe_local_iterator_base&
      operator=(const _Safe_local_iterator_base&);
  
      explicit
      _Safe_local_iterator_base(const _Safe_local_iterator_base&);
  
      ~_Safe_local_iterator_base() { this->_M_detach(); }
  
      _Safe_unordered_container_base*
      _M_get_container() const _GLIBCXX_NOEXCEPT;
  
    public:
      /** Attaches this iterator to the given container, detaching it
       *	from whatever container it was attached to originally. If the
       *	new container is the NULL pointer, the iterator is left
       *	unattached.
       */
      void _M_attach(_Safe_sequence_base* __seq, bool __constant);
  
      /** Likewise, but not thread-safe. */
      void _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
  
      /** Detach the iterator for whatever container it is attached to,
       *	if any.
      */
      void _M_detach();
  
      /** Likewise, but not thread-safe. */
      void _M_detach_single() throw ();
    };
  
    /**
     * @brief Base class that supports tracking of local iterators that
     * reference an unordered container.
     *
     * The %_Safe_unordered_container_base class provides basic support for
     * tracking iterators into an unordered container. Containers that track
     * iterators must derived from %_Safe_unordered_container_base publicly, so
     * that safe iterators (which inherit _Safe_iterator_base) can
     * attach to them. This class contains four linked lists of
     * iterators, one for constant iterators, one for mutable
     * iterators, one for constant local iterators, one for mutable local
     * iterators and a version number that allows very fast
     * invalidation of all iterators that reference the container.
     *
     * This class must ensure that no operation on it may throw an
     * exception, otherwise @a safe containers may fail to provide the
     * exception-safety guarantees required by the C++ standard.
     */
    class _Safe_unordered_container_base : public _Safe_sequence_base
    {
      typedef _Safe_sequence_base _Base;
    public:
      /// The list of mutable local iterators that reference this container
      _Safe_iterator_base* _M_local_iterators;
  
      /// The list of constant local iterators that reference this container
      _Safe_iterator_base* _M_const_local_iterators;
  
    protected:
      // Initialize with a version number of 1 and no iterators
      _Safe_unordered_container_base()
      : _M_local_iterators(nullptr), _M_const_local_iterators(nullptr)
      { }
  
      // Initialize with a version number of 1 and no iterators
      _Safe_unordered_container_base(const _Safe_unordered_container_base&)
      noexcept
      : _Safe_unordered_container_base() { }
  
      _Safe_unordered_container_base(_Safe_unordered_container_base&& __x)
      noexcept
      : _Safe_unordered_container_base()
      { this->_M_swap(__x); }
  
      /** Notify all iterators that reference this container that the
  	container is being destroyed. */
      ~_Safe_unordered_container_base()
      { this->_M_detach_all(); }
  
      /** Detach all iterators, leaving them singular. */
      void
      _M_detach_all();
  
      /** Swap this container with the given container. This operation
       *  also swaps ownership of the iterators, so that when the
       *  operation is complete all iterators that originally referenced
       *  one container now reference the other container.
       */
      void
      _M_swap(_Safe_unordered_container_base& __x);
  
    public:
      /** Attach an iterator to this container. */
      void
      _M_attach_local(_Safe_iterator_base* __it, bool __constant);
  
      /** Likewise but not thread safe. */
      void
      _M_attach_local_single(_Safe_iterator_base* __it, bool __constant) throw ();
  
      /** Detach an iterator from this container */
      void
      _M_detach_local(_Safe_iterator_base* __it);
  
      /** Likewise but not thread safe. */
      void
      _M_detach_local_single(_Safe_iterator_base* __it) throw ();
    };
  } // namespace __gnu_debug
  
  #endif
  