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// Safe sequence/iterator base implementation  -*- C++ -*-

// Copyright (C) 2003, 2004, 2005, 2006, 2009, 2010

// 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_base.h

 *  This file is a GNU debug extension to the Standard C++ Library.

 */

#ifndef _GLIBCXX_DEBUG_SAFE_BASE_H

#define _GLIBCXX_DEBUG_SAFE_BASE_H 1

#include <ext/concurrence.h>

namespace __gnu_debug

{

  class _Safe_sequence_base;

  /** \brief Basic functionality for a @a safe iterator.

   *

   *  The %_Safe_iterator_base base class implements the functionality

   *  of a safe iterator that is not specific to a particular iterator

   *  type. It contains a pointer back to the sequence it references

   *  along with iterator version information and pointers to form a

   *  doubly-linked list of 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_iterator_base

  {

  public:

    /** The sequence this iterator references; may be NULL to indicate

        a singular iterator. */

    _Safe_sequence_base* _M_sequence;

    /** The version number of this iterator. The sentinel value 0 is

     *  used to indicate an invalidated iterator (i.e., one that is

     *  singular because of an operation on the container). This

     *  version number must equal the version number in the sequence

     *  referenced by _M_sequence for the iterator to be

     *  non-singular.

     */

    unsigned int         _M_version;

    /** Pointer to the previous iterator in the sequence's list of

        iterators. Only valid when _M_sequence != NULL. */

    _Safe_iterator_base* _M_prior;

    /** Pointer to the next iterator in the sequence's list of

        iterators. Only valid when _M_sequence != NULL. */

    _Safe_iterator_base* _M_next;

  protected:

    /** Initializes the iterator and makes it singular. */

    _Safe_iterator_base()

    : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)

    { }

    /** Initialize the iterator to reference the sequence pointed to

     *  by @p __seq. @p __constant is true when we are initializing a

     *  constant iterator, and false if it is a mutable 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_iterator_base(const _Safe_sequence_base* __seq, bool __constant)

    : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)

    { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }

    /** Initializes the iterator to reference the same sequence that

        @p __x does. @p __constant is true if this is a constant

        iterator, and false if it is mutable. */

    _Safe_iterator_base(const _Safe_iterator_base& __x, bool __constant)

    : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)

    { this->_M_attach(__x._M_sequence, __constant); }

    _Safe_iterator_base&

    operator=(const _Safe_iterator_base&);

    explicit

    _Safe_iterator_base(const _Safe_iterator_base&);

    ~_Safe_iterator_base() { this->_M_detach(); }

    /** For use in _Safe_iterator. */

    __gnu_cxx::__mutex& _M_get_mutex() throw ();

  public:

    /** Attaches this iterator to the given sequence, detaching it

     *  from whatever sequence it was attached to originally. If the

     *  new sequence 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 sequence it is attached to,

     *  if any.

    */

    void _M_detach();

    /** Likewise, but not thread-safe. */

    void _M_detach_single() throw ();

    /** Determines if we are attached to the given sequence. */

    bool _M_attached_to(const _Safe_sequence_base* __seq) const

    { return _M_sequence == __seq; }

    /** Is this iterator singular? */

    _GLIBCXX_PURE bool _M_singular() const throw ();

    /** Can we compare this iterator to the given iterator @p __x?

        Returns true if both iterators are nonsingular and reference

        the same sequence. */

    _GLIBCXX_PURE bool _M_can_compare(const _Safe_iterator_base& __x) const throw ();

    /** Invalidate the iterator, making it singular. */

    void

    _M_invalidate()

    { _M_version = 0; }

    /** Reset all member variables */

    void

    _M_reset() throw ();

    /** Unlink itself */

    void

    _M_unlink() throw ()

    {

      if (_M_prior)

        _M_prior->_M_next = _M_next;

      if (_M_next)

        _M_next->_M_prior = _M_prior;

    }

  };

  /**

   * @brief Base class that supports tracking of iterators that

   * reference a sequence.

   *

   * The %_Safe_sequence_base class provides basic support for

   * tracking iterators into a sequence. Sequences that track

   * iterators must derived from %_Safe_sequence_base publicly, so

   * that safe iterators (which inherit _Safe_iterator_base) can

   * attach to them. This class contains two linked lists of

   * iterators, one for constant iterators and one for mutable

   * 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 sequences may fail to provide the

   * exception-safety guarantees required by the C++ standard.

   */

  class _Safe_sequence_base

  {

  public:

    /// The list of mutable iterators that reference this container

    _Safe_iterator_base* _M_iterators;

    /// The list of constant iterators that reference this container

    _Safe_iterator_base* _M_const_iterators;

    /// The container version number. This number may never be 0.

    mutable unsigned int _M_version;

  protected:

    // Initialize with a version number of 1 and no iterators

    _Safe_sequence_base()

    : _M_iterators(0), _M_const_iterators(0), _M_version(1)

    { }

    /** Notify all iterators that reference this sequence that the

        sequence is being destroyed. */

    ~_Safe_sequence_base()

    { this->_M_detach_all(); }

    /** Detach all iterators, leaving them singular. */

    void

    _M_detach_all();

    /** Detach all singular iterators.

     *  @post for all iterators i attached to this sequence,

     *   i->_M_version == _M_version.

     */

    void

    _M_detach_singular();

    /** Revalidates all attached singular iterators.  This method may

     *  be used to validate iterators that were invalidated before

     *  (but for some reason, such as an exception, need to become

     *  valid again).

     */

    void

    _M_revalidate_singular();

    /** Swap this sequence with the given sequence. 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_sequence_base& __x);

    /** For use in _Safe_sequence. */

    __gnu_cxx::__mutex& _M_get_mutex() throw ();

  public:

    /** Invalidates all iterators. */

    void

    _M_invalidate_all() const

    { if (++_M_version == 0) _M_version = 1; }

    /** Attach an iterator to this sequence. */

    void

    _M_attach(_Safe_iterator_base* __it, bool __constant);

    /** Likewise but not thread safe. */

    void

    _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();

    /** Detach an iterator from this sequence */

    void

    _M_detach(_Safe_iterator_base* __it);

    /** Likewise but not thread safe. */

    void

    _M_detach_single(_Safe_iterator_base* __it) throw ();

  };

} // namespace __gnu_debug

#endif