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[EDIT] FILE: safe_iterator.tcc

// Debugging iterator implementation (out of line) -*- C++ -*-

// Copyright (C) 2003-2018 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_iterator.tcc
 *  This file is a GNU debug extension to the Standard C++ Library.
 */

#ifndef _GLIBCXX_DEBUG_SAFE_ITERATOR_TCC
#define _GLIBCXX_DEBUG_SAFE_ITERATOR_TCC 1

namespace __gnu_debug
{
  template<typename _Iterator, typename _Sequence>
    bool
    _Safe_iterator<_Iterator, _Sequence>::
    _M_can_advance(const difference_type& __n) const
    {
      if (this->_M_singular())
	return false;

if (__n == 0)
	return true;

if (__n < 0)
	{
	  std::pair<difference_type, _Distance_precision> __dist =
	    __get_distance_from_begin(*this);
	  bool __ok =  ((__dist.second == __dp_exact && __dist.first >= -__n)
			|| (__dist.second != __dp_exact && __dist.first > 0));
	  return __ok;
	}
      else
	{
	  std::pair<difference_type, _Distance_precision> __dist =
	    __get_distance_to_end(*this);
	  bool __ok = ((__dist.second == __dp_exact && __dist.first >= __n)
		       || (__dist.second != __dp_exact && __dist.first > 0));
	  return __ok;
	}
    }

template<typename _Iterator, typename _Sequence>
    bool
    _Safe_iterator<_Iterator, _Sequence>::
    _M_valid_range(const _Safe_iterator& __rhs,
		   std::pair<difference_type, _Distance_precision>& __dist,
		   bool __check_dereferenceable) const
    {
      if (!_M_can_compare(__rhs))
	return false;

/* Determine iterators order */
      __dist = __get_distance(*this, __rhs);
      switch (__dist.second)
	{
	case __dp_equality:
	  if (__dist.first == 0)
	    return true;
	  break;

case __dp_sign:
	case __dp_exact:
	  // If range is not empty first iterator must be dereferenceable.
	  if (__dist.first > 0)
	    return !__check_dereferenceable || _M_dereferenceable();
	  return __dist.first == 0;
	}

// Assume that this is a valid range; we can't check anything else.
      return true;
    }
} // namespace __gnu_debug

#endif

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