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  1. // Deque implementation -*- C++ -*-
  2.  
  3. // Copyright (C) 2001-2013 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. /*
  26.  *
  27.  * Copyright (c) 1994
  28.  * Hewlett-Packard Company
  29.  *
  30.  * Permission to use, copy, modify, distribute and sell this software
  31.  * and its documentation for any purpose is hereby granted without fee,
  32.  * provided that the above copyright notice appear in all copies and
  33.  * that both that copyright notice and this permission notice appear
  34.  * in supporting documentation.  Hewlett-Packard Company makes no
  35.  * representations about the suitability of this software for any
  36.  * purpose.  It is provided "as is" without express or implied warranty.
  37.  *
  38.  *
  39.  * Copyright (c) 1997
  40.  * Silicon Graphics Computer Systems, Inc.
  41.  *
  42.  * Permission to use, copy, modify, distribute and sell this software
  43.  * and its documentation for any purpose is hereby granted without fee,
  44.  * provided that the above copyright notice appear in all copies and
  45.  * that both that copyright notice and this permission notice appear
  46.  * in supporting documentation.  Silicon Graphics makes no
  47.  * representations about the suitability of this software for any
  48.  * purpose.  It is provided "as is" without express or implied warranty.
  49.  */
  50.  
  51. /** @file bits/stl_deque.h
  52.  *  This is an internal header file, included by other library headers.
  53.  *  Do not attempt to use it directly. @headername{deque}
  54.  */
  55.  
  56. #ifndef _STL_DEQUE_H
  57. #define _STL_DEQUE_H 1
  58.  
  59. #include <bits/concept_check.h>
  60. #include <bits/stl_iterator_base_types.h>
  61. #include <bits/stl_iterator_base_funcs.h>
  62. #if __cplusplus >= 201103L
  63. #include <initializer_list>
  64. #endif
  65.  
  66. namespace std _GLIBCXX_VISIBILITY(default)
  67. {
  68. _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
  69.  
  70.   /**
  71.    *  @brief This function controls the size of memory nodes.
  72.    *  @param  __size  The size of an element.
  73.    *  @return   The number (not byte size) of elements per node.
  74.    *
  75.    *  This function started off as a compiler kludge from SGI, but
  76.    *  seems to be a useful wrapper around a repeated constant
  77.    *  expression.  The @b 512 is tunable (and no other code needs to
  78.    *  change), but no investigation has been done since inheriting the
  79.    *  SGI code.  Touch _GLIBCXX_DEQUE_BUF_SIZE only if you know what
  80.    *  you are doing, however: changing it breaks the binary
  81.    *  compatibility!!
  82.   */
  83.  
  84. #ifndef _GLIBCXX_DEQUE_BUF_SIZE
  85. #define _GLIBCXX_DEQUE_BUF_SIZE 512
  86. #endif
  87.  
  88.   inline size_t
  89.   __deque_buf_size(size_t __size)
  90.   { return (__size < _GLIBCXX_DEQUE_BUF_SIZE
  91.             ? size_t(_GLIBCXX_DEQUE_BUF_SIZE / __size) : size_t(1)); }
  92.  
  93.  
  94.   /**
  95.    *  @brief A deque::iterator.
  96.    *
  97.    *  Quite a bit of intelligence here.  Much of the functionality of
  98.    *  deque is actually passed off to this class.  A deque holds two
  99.    *  of these internally, marking its valid range.  Access to
  100.    *  elements is done as offsets of either of those two, relying on
  101.    *  operator overloading in this class.
  102.    *
  103.    *  All the functions are op overloads except for _M_set_node.
  104.   */
  105.   template<typename _Tp, typename _Ref, typename _Ptr>
  106.     struct _Deque_iterator
  107.     {
  108.       typedef _Deque_iterator<_Tp, _Tp&, _Tp*>             iterator;
  109.       typedef _Deque_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;
  110.  
  111.       static size_t _S_buffer_size()
  112.       { return __deque_buf_size(sizeof(_Tp)); }
  113.  
  114.       typedef std::random_access_iterator_tag iterator_category;
  115.       typedef _Tp                             value_type;
  116.       typedef _Ptr                            pointer;
  117.       typedef _Ref                            reference;
  118.       typedef size_t                          size_type;
  119.       typedef ptrdiff_t                       difference_type;
  120.       typedef _Tp**                           _Map_pointer;
  121.       typedef _Deque_iterator                 _Self;
  122.  
  123.       _Tp* _M_cur;
  124.       _Tp* _M_first;
  125.       _Tp* _M_last;
  126.       _Map_pointer _M_node;
  127.  
  128.       _Deque_iterator(_Tp* __x, _Map_pointer __y)
  129.       : _M_cur(__x), _M_first(*__y),
  130.         _M_last(*__y + _S_buffer_size()), _M_node(__y) { }
  131.  
  132.       _Deque_iterator()
  133.       : _M_cur(0), _M_first(0), _M_last(0), _M_node(0) { }
  134.  
  135.       _Deque_iterator(const iterator& __x)
  136.       : _M_cur(__x._M_cur), _M_first(__x._M_first),
  137.         _M_last(__x._M_last), _M_node(__x._M_node) { }
  138.  
  139.       reference
  140.       operator*() const
  141.       { return *_M_cur; }
  142.  
  143.       pointer
  144.       operator->() const
  145.       { return _M_cur; }
  146.  
  147.       _Self&
  148.       operator++()
  149.       {
  150.         ++_M_cur;
  151.         if (_M_cur == _M_last)
  152.           {
  153.             _M_set_node(_M_node + 1);
  154.             _M_cur = _M_first;
  155.           }
  156.         return *this;
  157.       }
  158.  
  159.       _Self
  160.       operator++(int)
  161.       {
  162.         _Self __tmp = *this;
  163.         ++*this;
  164.         return __tmp;
  165.       }
  166.  
  167.       _Self&
  168.       operator--()
  169.       {
  170.         if (_M_cur == _M_first)
  171.           {
  172.             _M_set_node(_M_node - 1);
  173.             _M_cur = _M_last;
  174.           }
  175.         --_M_cur;
  176.         return *this;
  177.       }
  178.  
  179.       _Self
  180.       operator--(int)
  181.       {
  182.         _Self __tmp = *this;
  183.         --*this;
  184.         return __tmp;
  185.       }
  186.  
  187.       _Self&
  188.       operator+=(difference_type __n)
  189.       {
  190.         const difference_type __offset = __n + (_M_cur - _M_first);
  191.         if (__offset >= 0 && __offset < difference_type(_S_buffer_size()))
  192.           _M_cur += __n;
  193.         else
  194.           {
  195.             const difference_type __node_offset =
  196.               __offset > 0 ? __offset / difference_type(_S_buffer_size())
  197.                            : -difference_type((-__offset - 1)
  198.                                               / _S_buffer_size()) - 1;
  199.             _M_set_node(_M_node + __node_offset);
  200.             _M_cur = _M_first + (__offset - __node_offset
  201.                                  * difference_type(_S_buffer_size()));
  202.           }
  203.         return *this;
  204.       }
  205.  
  206.       _Self
  207.       operator+(difference_type __n) const
  208.       {
  209.         _Self __tmp = *this;
  210.         return __tmp += __n;
  211.       }
  212.  
  213.       _Self&
  214.       operator-=(difference_type __n)
  215.       { return *this += -__n; }
  216.  
  217.       _Self
  218.       operator-(difference_type __n) const
  219.       {
  220.         _Self __tmp = *this;
  221.         return __tmp -= __n;
  222.       }
  223.  
  224.       reference
  225.       operator[](difference_type __n) const
  226.       { return *(*this + __n); }
  227.  
  228.       /**
  229.        *  Prepares to traverse new_node.  Sets everything except
  230.        *  _M_cur, which should therefore be set by the caller
  231.        *  immediately afterwards, based on _M_first and _M_last.
  232.        */
  233.       void
  234.       _M_set_node(_Map_pointer __new_node)
  235.       {
  236.         _M_node = __new_node;
  237.         _M_first = *__new_node;
  238.         _M_last = _M_first + difference_type(_S_buffer_size());
  239.       }
  240.     };
  241.  
  242.   // Note: we also provide overloads whose operands are of the same type in
  243.   // order to avoid ambiguous overload resolution when std::rel_ops operators
  244.   // are in scope (for additional details, see libstdc++/3628)
  245.   template<typename _Tp, typename _Ref, typename _Ptr>
  246.     inline bool
  247.     operator==(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
  248.                const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
  249.     { return __x._M_cur == __y._M_cur; }
  250.  
  251.   template<typename _Tp, typename _RefL, typename _PtrL,
  252.            typename _RefR, typename _PtrR>
  253.     inline bool
  254.     operator==(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
  255.                const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
  256.     { return __x._M_cur == __y._M_cur; }
  257.  
  258.   template<typename _Tp, typename _Ref, typename _Ptr>
  259.     inline bool
  260.     operator!=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
  261.                const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
  262.     { return !(__x == __y); }
  263.  
  264.   template<typename _Tp, typename _RefL, typename _PtrL,
  265.            typename _RefR, typename _PtrR>
  266.     inline bool
  267.     operator!=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
  268.                const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
  269.     { return !(__x == __y); }
  270.  
  271.   template<typename _Tp, typename _Ref, typename _Ptr>
  272.     inline bool
  273.     operator<(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
  274.               const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
  275.     { return (__x._M_node == __y._M_node) ? (__x._M_cur < __y._M_cur)
  276.                                           : (__x._M_node < __y._M_node); }
  277.  
  278.   template<typename _Tp, typename _RefL, typename _PtrL,
  279.            typename _RefR, typename _PtrR>
  280.     inline bool
  281.     operator<(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
  282.               const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
  283.     { return (__x._M_node == __y._M_node) ? (__x._M_cur < __y._M_cur)
  284.                                           : (__x._M_node < __y._M_node); }
  285.  
  286.   template<typename _Tp, typename _Ref, typename _Ptr>
  287.     inline bool
  288.     operator>(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
  289.               const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
  290.     { return __y < __x; }
  291.  
  292.   template<typename _Tp, typename _RefL, typename _PtrL,
  293.            typename _RefR, typename _PtrR>
  294.     inline bool
  295.     operator>(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
  296.               const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
  297.     { return __y < __x; }
  298.  
  299.   template<typename _Tp, typename _Ref, typename _Ptr>
  300.     inline bool
  301.     operator<=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
  302.                const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
  303.     { return !(__y < __x); }
  304.  
  305.   template<typename _Tp, typename _RefL, typename _PtrL,
  306.            typename _RefR, typename _PtrR>
  307.     inline bool
  308.     operator<=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
  309.                const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
  310.     { return !(__y < __x); }
  311.  
  312.   template<typename _Tp, typename _Ref, typename _Ptr>
  313.     inline bool
  314.     operator>=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
  315.                const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
  316.     { return !(__x < __y); }
  317.  
  318.   template<typename _Tp, typename _RefL, typename _PtrL,
  319.            typename _RefR, typename _PtrR>
  320.     inline bool
  321.     operator>=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
  322.                const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
  323.     { return !(__x < __y); }
  324.  
  325.   // _GLIBCXX_RESOLVE_LIB_DEFECTS
  326.   // According to the resolution of DR179 not only the various comparison
  327.   // operators but also operator- must accept mixed iterator/const_iterator
  328.   // parameters.
  329.   template<typename _Tp, typename _Ref, typename _Ptr>
  330.     inline typename _Deque_iterator<_Tp, _Ref, _Ptr>::difference_type
  331.     operator-(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
  332.               const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
  333.     {
  334.       return typename _Deque_iterator<_Tp, _Ref, _Ptr>::difference_type
  335.         (_Deque_iterator<_Tp, _Ref, _Ptr>::_S_buffer_size())
  336.         * (__x._M_node - __y._M_node - 1) + (__x._M_cur - __x._M_first)
  337.         + (__y._M_last - __y._M_cur);
  338.     }
  339.  
  340.   template<typename _Tp, typename _RefL, typename _PtrL,
  341.            typename _RefR, typename _PtrR>
  342.     inline typename _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
  343.     operator-(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
  344.               const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
  345.     {
  346.       return typename _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
  347.         (_Deque_iterator<_Tp, _RefL, _PtrL>::_S_buffer_size())
  348.         * (__x._M_node - __y._M_node - 1) + (__x._M_cur - __x._M_first)
  349.         + (__y._M_last - __y._M_cur);
  350.     }
  351.  
  352.   template<typename _Tp, typename _Ref, typename _Ptr>
  353.     inline _Deque_iterator<_Tp, _Ref, _Ptr>
  354.     operator+(ptrdiff_t __n, const _Deque_iterator<_Tp, _Ref, _Ptr>& __x)
  355.     { return __x + __n; }
  356.  
  357.   template<typename _Tp>
  358.     void
  359.     fill(const _Deque_iterator<_Tp, _Tp&, _Tp*>&,
  360.          const _Deque_iterator<_Tp, _Tp&, _Tp*>&, const _Tp&);
  361.  
  362.   template<typename _Tp>
  363.     _Deque_iterator<_Tp, _Tp&, _Tp*>
  364.     copy(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  365.          _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  366.          _Deque_iterator<_Tp, _Tp&, _Tp*>);
  367.  
  368.   template<typename _Tp>
  369.     inline _Deque_iterator<_Tp, _Tp&, _Tp*>
  370.     copy(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
  371.          _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
  372.          _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
  373.     { return std::copy(_Deque_iterator<_Tp, const _Tp&, const _Tp*>(__first),
  374.                        _Deque_iterator<_Tp, const _Tp&, const _Tp*>(__last),
  375.                        __result); }
  376.  
  377.   template<typename _Tp>
  378.     _Deque_iterator<_Tp, _Tp&, _Tp*>
  379.     copy_backward(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  380.                   _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  381.                   _Deque_iterator<_Tp, _Tp&, _Tp*>);
  382.  
  383.   template<typename _Tp>
  384.     inline _Deque_iterator<_Tp, _Tp&, _Tp*>
  385.     copy_backward(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
  386.                   _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
  387.                   _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
  388.     { return std::copy_backward(_Deque_iterator<_Tp,
  389.                                 const _Tp&, const _Tp*>(__first),
  390.                                 _Deque_iterator<_Tp,
  391.                                 const _Tp&, const _Tp*>(__last),
  392.                                 __result); }
  393.  
  394. #if __cplusplus >= 201103L
  395.   template<typename _Tp>
  396.     _Deque_iterator<_Tp, _Tp&, _Tp*>
  397.     move(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  398.          _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  399.          _Deque_iterator<_Tp, _Tp&, _Tp*>);
  400.  
  401.   template<typename _Tp>
  402.     inline _Deque_iterator<_Tp, _Tp&, _Tp*>
  403.     move(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
  404.          _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
  405.          _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
  406.     { return std::move(_Deque_iterator<_Tp, const _Tp&, const _Tp*>(__first),
  407.                        _Deque_iterator<_Tp, const _Tp&, const _Tp*>(__last),
  408.                        __result); }
  409.  
  410.   template<typename _Tp>
  411.     _Deque_iterator<_Tp, _Tp&, _Tp*>
  412.     move_backward(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  413.                   _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
  414.                   _Deque_iterator<_Tp, _Tp&, _Tp*>);
  415.  
  416.   template<typename _Tp>
  417.     inline _Deque_iterator<_Tp, _Tp&, _Tp*>
  418.     move_backward(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
  419.                   _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
  420.                   _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
  421.     { return std::move_backward(_Deque_iterator<_Tp,
  422.                                 const _Tp&, const _Tp*>(__first),
  423.                                 _Deque_iterator<_Tp,
  424.                                 const _Tp&, const _Tp*>(__last),
  425.                                 __result); }
  426. #endif
  427.  
  428.   /**
  429.    *  Deque base class.  This class provides the unified face for %deque's
  430.    *  allocation.  This class's constructor and destructor allocate and
  431.    *  deallocate (but do not initialize) storage.  This makes %exception
  432.    *  safety easier.
  433.    *
  434.    *  Nothing in this class ever constructs or destroys an actual Tp element.
  435.    *  (Deque handles that itself.)  Only/All memory management is performed
  436.    *  here.
  437.   */
  438.   template<typename _Tp, typename _Alloc>
  439.     class _Deque_base
  440.     {
  441.     public:
  442.       typedef _Alloc                  allocator_type;
  443.  
  444.       allocator_type
  445.       get_allocator() const _GLIBCXX_NOEXCEPT
  446.       { return allocator_type(_M_get_Tp_allocator()); }
  447.  
  448.       typedef _Deque_iterator<_Tp, _Tp&, _Tp*>             iterator;
  449.       typedef _Deque_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;
  450.  
  451.       _Deque_base()
  452.       : _M_impl()
  453.       { _M_initialize_map(0); }
  454.  
  455.       _Deque_base(size_t __num_elements)
  456.       : _M_impl()
  457.       { _M_initialize_map(__num_elements); }
  458.  
  459.       _Deque_base(const allocator_type& __a, size_t __num_elements)
  460.       : _M_impl(__a)
  461.       { _M_initialize_map(__num_elements); }
  462.  
  463.       _Deque_base(const allocator_type& __a)
  464.       : _M_impl(__a)
  465.       { }
  466.  
  467. #if __cplusplus >= 201103L
  468.       _Deque_base(_Deque_base&& __x)
  469.       : _M_impl(std::move(__x._M_get_Tp_allocator()))
  470.       {
  471.         _M_initialize_map(0);
  472.         if (__x._M_impl._M_map)
  473.           {
  474.             std::swap(this->_M_impl._M_start, __x._M_impl._M_start);
  475.             std::swap(this->_M_impl._M_finish, __x._M_impl._M_finish);
  476.             std::swap(this->_M_impl._M_map, __x._M_impl._M_map);
  477.             std::swap(this->_M_impl._M_map_size, __x._M_impl._M_map_size);
  478.           }
  479.       }
  480. #endif
  481.  
  482.       ~_Deque_base();
  483.  
  484.     protected:
  485.       //This struct encapsulates the implementation of the std::deque
  486.       //standard container and at the same time makes use of the EBO
  487.       //for empty allocators.
  488.       typedef typename _Alloc::template rebind<_Tp*>::other _Map_alloc_type;
  489.  
  490.       typedef typename _Alloc::template rebind<_Tp>::other  _Tp_alloc_type;
  491.  
  492.       struct _Deque_impl
  493.       : public _Tp_alloc_type
  494.       {
  495.         _Tp** _M_map;
  496.         size_t _M_map_size;
  497.         iterator _M_start;
  498.         iterator _M_finish;
  499.  
  500.         _Deque_impl()
  501.         : _Tp_alloc_type(), _M_map(0), _M_map_size(0),
  502.           _M_start(), _M_finish()
  503.         { }
  504.  
  505.         _Deque_impl(const _Tp_alloc_type& __a)
  506.         : _Tp_alloc_type(__a), _M_map(0), _M_map_size(0),
  507.           _M_start(), _M_finish()
  508.         { }
  509.  
  510. #if __cplusplus >= 201103L
  511.         _Deque_impl(_Tp_alloc_type&& __a)
  512.         : _Tp_alloc_type(std::move(__a)), _M_map(0), _M_map_size(0),
  513.           _M_start(), _M_finish()
  514.         { }
  515. #endif
  516.       };
  517.  
  518.       _Tp_alloc_type&
  519.       _M_get_Tp_allocator() _GLIBCXX_NOEXCEPT
  520.       { return *static_cast<_Tp_alloc_type*>(&this->_M_impl); }
  521.  
  522.       const _Tp_alloc_type&
  523.       _M_get_Tp_allocator() const _GLIBCXX_NOEXCEPT
  524.       { return *static_cast<const _Tp_alloc_type*>(&this->_M_impl); }
  525.  
  526.       _Map_alloc_type
  527.       _M_get_map_allocator() const _GLIBCXX_NOEXCEPT
  528.       { return _Map_alloc_type(_M_get_Tp_allocator()); }
  529.  
  530.       _Tp*
  531.       _M_allocate_node()
  532.       {
  533.         return _M_impl._Tp_alloc_type::allocate(__deque_buf_size(sizeof(_Tp)));
  534.       }
  535.  
  536.       void
  537.       _M_deallocate_node(_Tp* __p)
  538.       {
  539.         _M_impl._Tp_alloc_type::deallocate(__p, __deque_buf_size(sizeof(_Tp)));
  540.       }
  541.  
  542.       _Tp**
  543.       _M_allocate_map(size_t __n)
  544.       { return _M_get_map_allocator().allocate(__n); }
  545.  
  546.       void
  547.       _M_deallocate_map(_Tp** __p, size_t __n)
  548.       { _M_get_map_allocator().deallocate(__p, __n); }
  549.  
  550.     protected:
  551.       void _M_initialize_map(size_t);
  552.       void _M_create_nodes(_Tp** __nstart, _Tp** __nfinish);
  553.       void _M_destroy_nodes(_Tp** __nstart, _Tp** __nfinish);
  554.       enum { _S_initial_map_size = 8 };
  555.  
  556.       _Deque_impl _M_impl;
  557.     };
  558.  
  559.   template<typename _Tp, typename _Alloc>
  560.     _Deque_base<_Tp, _Alloc>::
  561.     ~_Deque_base()
  562.     {
  563.       if (this->_M_impl._M_map)
  564.         {
  565.           _M_destroy_nodes(this->_M_impl._M_start._M_node,
  566.                            this->_M_impl._M_finish._M_node + 1);
  567.           _M_deallocate_map(this->_M_impl._M_map, this->_M_impl._M_map_size);
  568.         }
  569.     }
  570.  
  571.   /**
  572.    *  @brief Layout storage.
  573.    *  @param  __num_elements  The count of T's for which to allocate space
  574.    *                        at first.
  575.    *  @return   Nothing.
  576.    *
  577.    *  The initial underlying memory layout is a bit complicated...
  578.   */
  579.   template<typename _Tp, typename _Alloc>
  580.     void
  581.     _Deque_base<_Tp, _Alloc>::
  582.     _M_initialize_map(size_t __num_elements)
  583.     {
  584.       const size_t __num_nodes = (__num_elements/ __deque_buf_size(sizeof(_Tp))
  585.                                   + 1);
  586.  
  587.       this->_M_impl._M_map_size = std::max((size_t) _S_initial_map_size,
  588.                                            size_t(__num_nodes + 2));
  589.       this->_M_impl._M_map = _M_allocate_map(this->_M_impl._M_map_size);
  590.  
  591.       // For "small" maps (needing less than _M_map_size nodes), allocation
  592.       // starts in the middle elements and grows outwards.  So nstart may be
  593.       // the beginning of _M_map, but for small maps it may be as far in as
  594.       // _M_map+3.
  595.  
  596.       _Tp** __nstart = (this->_M_impl._M_map
  597.                         + (this->_M_impl._M_map_size - __num_nodes) / 2);
  598.       _Tp** __nfinish = __nstart + __num_nodes;
  599.  
  600.       __try
  601.         { _M_create_nodes(__nstart, __nfinish); }
  602.       __catch(...)
  603.         {
  604.           _M_deallocate_map(this->_M_impl._M_map, this->_M_impl._M_map_size);
  605.           this->_M_impl._M_map = 0;
  606.           this->_M_impl._M_map_size = 0;
  607.           __throw_exception_again;
  608.         }
  609.  
  610.       this->_M_impl._M_start._M_set_node(__nstart);
  611.       this->_M_impl._M_finish._M_set_node(__nfinish - 1);
  612.       this->_M_impl._M_start._M_cur = _M_impl._M_start._M_first;
  613.       this->_M_impl._M_finish._M_cur = (this->_M_impl._M_finish._M_first
  614.                                         + __num_elements
  615.                                         % __deque_buf_size(sizeof(_Tp)));
  616.     }
  617.  
  618.   template<typename _Tp, typename _Alloc>
  619.     void
  620.     _Deque_base<_Tp, _Alloc>::
  621.     _M_create_nodes(_Tp** __nstart, _Tp** __nfinish)
  622.     {
  623.       _Tp** __cur;
  624.       __try
  625.         {
  626.           for (__cur = __nstart; __cur < __nfinish; ++__cur)
  627.             *__cur = this->_M_allocate_node();
  628.         }
  629.       __catch(...)
  630.         {
  631.           _M_destroy_nodes(__nstart, __cur);
  632.           __throw_exception_again;
  633.         }
  634.     }
  635.  
  636.   template<typename _Tp, typename _Alloc>
  637.     void
  638.     _Deque_base<_Tp, _Alloc>::
  639.     _M_destroy_nodes(_Tp** __nstart, _Tp** __nfinish)
  640.     {
  641.       for (_Tp** __n = __nstart; __n < __nfinish; ++__n)
  642.         _M_deallocate_node(*__n);
  643.     }
  644.  
  645.   /**
  646.    *  @brief  A standard container using fixed-size memory allocation and
  647.    *  constant-time manipulation of elements at either end.
  648.    *
  649.    *  @ingroup sequences
  650.    *
  651.    *  @tparam _Tp  Type of element.
  652.    *  @tparam _Alloc  Allocator type, defaults to allocator<_Tp>.
  653.    *
  654.    *  Meets the requirements of a <a href="tables.html#65">container</a>, a
  655.    *  <a href="tables.html#66">reversible container</a>, and a
  656.    *  <a href="tables.html#67">sequence</a>, including the
  657.    *  <a href="tables.html#68">optional sequence requirements</a>.
  658.    *
  659.    *  In previous HP/SGI versions of deque, there was an extra template
  660.    *  parameter so users could control the node size.  This extension turned
  661.    *  out to violate the C++ standard (it can be detected using template
  662.    *  template parameters), and it was removed.
  663.    *
  664.    *  Here's how a deque<Tp> manages memory.  Each deque has 4 members:
  665.    *
  666.    *  - Tp**        _M_map
  667.    *  - size_t      _M_map_size
  668.    *  - iterator    _M_start, _M_finish
  669.    *
  670.    *  map_size is at least 8.  %map is an array of map_size
  671.    *  pointers-to-@a nodes.  (The name %map has nothing to do with the
  672.    *  std::map class, and @b nodes should not be confused with
  673.    *  std::list's usage of @a node.)
  674.    *
  675.    *  A @a node has no specific type name as such, but it is referred
  676.    *  to as @a node in this file.  It is a simple array-of-Tp.  If Tp
  677.    *  is very large, there will be one Tp element per node (i.e., an
  678.    *  @a array of one).  For non-huge Tp's, node size is inversely
  679.    *  related to Tp size: the larger the Tp, the fewer Tp's will fit
  680.    *  in a node.  The goal here is to keep the total size of a node
  681.    *  relatively small and constant over different Tp's, to improve
  682.    *  allocator efficiency.
  683.    *
  684.    *  Not every pointer in the %map array will point to a node.  If
  685.    *  the initial number of elements in the deque is small, the
  686.    *  /middle/ %map pointers will be valid, and the ones at the edges
  687.    *  will be unused.  This same situation will arise as the %map
  688.    *  grows: available %map pointers, if any, will be on the ends.  As
  689.    *  new nodes are created, only a subset of the %map's pointers need
  690.    *  to be copied @a outward.
  691.    *
  692.    *  Class invariants:
  693.    * - For any nonsingular iterator i:
  694.    *    - i.node points to a member of the %map array.  (Yes, you read that
  695.    *      correctly:  i.node does not actually point to a node.)  The member of
  696.    *      the %map array is what actually points to the node.
  697.    *    - i.first == *(i.node)    (This points to the node (first Tp element).)
  698.    *    - i.last  == i.first + node_size
  699.    *    - i.cur is a pointer in the range [i.first, i.last).  NOTE:
  700.    *      the implication of this is that i.cur is always a dereferenceable
  701.    *      pointer, even if i is a past-the-end iterator.
  702.    * - Start and Finish are always nonsingular iterators.  NOTE: this
  703.    * means that an empty deque must have one node, a deque with <N
  704.    * elements (where N is the node buffer size) must have one node, a
  705.    * deque with N through (2N-1) elements must have two nodes, etc.
  706.    * - For every node other than start.node and finish.node, every
  707.    * element in the node is an initialized object.  If start.node ==
  708.    * finish.node, then [start.cur, finish.cur) are initialized
  709.    * objects, and the elements outside that range are uninitialized
  710.    * storage.  Otherwise, [start.cur, start.last) and [finish.first,
  711.    * finish.cur) are initialized objects, and [start.first, start.cur)
  712.    * and [finish.cur, finish.last) are uninitialized storage.
  713.    * - [%map, %map + map_size) is a valid, non-empty range.
  714.    * - [start.node, finish.node] is a valid range contained within
  715.    *   [%map, %map + map_size).
  716.    * - A pointer in the range [%map, %map + map_size) points to an allocated
  717.    *   node if and only if the pointer is in the range
  718.    *   [start.node, finish.node].
  719.    *
  720.    *  Here's the magic:  nothing in deque is @b aware of the discontiguous
  721.    *  storage!
  722.    *
  723.    *  The memory setup and layout occurs in the parent, _Base, and the iterator
  724.    *  class is entirely responsible for @a leaping from one node to the next.
  725.    *  All the implementation routines for deque itself work only through the
  726.    *  start and finish iterators.  This keeps the routines simple and sane,
  727.    *  and we can use other standard algorithms as well.
  728.   */
  729.   template<typename _Tp, typename _Alloc = std::allocator<_Tp> >
  730.     class deque : protected _Deque_base<_Tp, _Alloc>
  731.     {
  732.       // concept requirements
  733.       typedef typename _Alloc::value_type        _Alloc_value_type;
  734.       __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
  735.       __glibcxx_class_requires2(_Tp, _Alloc_value_type, _SameTypeConcept)
  736.  
  737.       typedef _Deque_base<_Tp, _Alloc>           _Base;
  738.       typedef typename _Base::_Tp_alloc_type     _Tp_alloc_type;
  739.  
  740.     public:
  741.       typedef _Tp                                        value_type;
  742.       typedef typename _Tp_alloc_type::pointer           pointer;
  743.       typedef typename _Tp_alloc_type::const_pointer     const_pointer;
  744.       typedef typename _Tp_alloc_type::reference         reference;
  745.       typedef typename _Tp_alloc_type::const_reference   const_reference;
  746.       typedef typename _Base::iterator                   iterator;
  747.       typedef typename _Base::const_iterator             const_iterator;
  748.       typedef std::reverse_iterator<const_iterator>      const_reverse_iterator;
  749.       typedef std::reverse_iterator<iterator>            reverse_iterator;
  750.       typedef size_t                             size_type;
  751.       typedef ptrdiff_t                          difference_type;
  752.       typedef _Alloc                             allocator_type;
  753.  
  754.     protected:
  755.       typedef pointer*                           _Map_pointer;
  756.  
  757.       static size_t _S_buffer_size()
  758.       { return __deque_buf_size(sizeof(_Tp)); }
  759.  
  760.       // Functions controlling memory layout, and nothing else.
  761.       using _Base::_M_initialize_map;
  762.       using _Base::_M_create_nodes;
  763.       using _Base::_M_destroy_nodes;
  764.       using _Base::_M_allocate_node;
  765.       using _Base::_M_deallocate_node;
  766.       using _Base::_M_allocate_map;
  767.       using _Base::_M_deallocate_map;
  768.       using _Base::_M_get_Tp_allocator;
  769.  
  770.       /**
  771.        *  A total of four data members accumulated down the hierarchy.
  772.        *  May be accessed via _M_impl.*
  773.        */
  774.       using _Base::_M_impl;
  775.  
  776.     public:
  777.       // [23.2.1.1] construct/copy/destroy
  778.       // (assign() and get_allocator() are also listed in this section)
  779.       /**
  780.        *  @brief  Default constructor creates no elements.
  781.        */
  782.       deque()
  783.       : _Base() { }
  784.  
  785.       /**
  786.        *  @brief  Creates a %deque with no elements.
  787.        *  @param  __a  An allocator object.
  788.        */
  789.       explicit
  790.       deque(const allocator_type& __a)
  791.       : _Base(__a, 0) { }
  792.  
  793. #if __cplusplus >= 201103L
  794.       /**
  795.        *  @brief  Creates a %deque with default constructed elements.
  796.        *  @param  __n  The number of elements to initially create.
  797.        *
  798.        *  This constructor fills the %deque with @a n default
  799.        *  constructed elements.
  800.        */
  801.       explicit
  802.       deque(size_type __n)
  803.       : _Base(__n)
  804.       { _M_default_initialize(); }
  805.  
  806.       /**
  807.        *  @brief  Creates a %deque with copies of an exemplar element.
  808.        *  @param  __n  The number of elements to initially create.
  809.        *  @param  __value  An element to copy.
  810.        *  @param  __a  An allocator.
  811.        *
  812.        *  This constructor fills the %deque with @a __n copies of @a __value.
  813.        */
  814.       deque(size_type __n, const value_type& __value,
  815.             const allocator_type& __a = allocator_type())
  816.       : _Base(__a, __n)
  817.       { _M_fill_initialize(__value); }
  818. #else
  819.       /**
  820.        *  @brief  Creates a %deque with copies of an exemplar element.
  821.        *  @param  __n  The number of elements to initially create.
  822.        *  @param  __value  An element to copy.
  823.        *  @param  __a  An allocator.
  824.        *
  825.        *  This constructor fills the %deque with @a __n copies of @a __value.
  826.        */
  827.       explicit
  828.       deque(size_type __n, const value_type& __value = value_type(),
  829.             const allocator_type& __a = allocator_type())
  830.       : _Base(__a, __n)
  831.       { _M_fill_initialize(__value); }
  832. #endif
  833.  
  834.       /**
  835.        *  @brief  %Deque copy constructor.
  836.        *  @param  __x  A %deque of identical element and allocator types.
  837.        *
  838.        *  The newly-created %deque uses a copy of the allocation object used
  839.        *  by @a __x.
  840.        */
  841.       deque(const deque& __x)
  842.       : _Base(__x._M_get_Tp_allocator(), __x.size())
  843.       { std::__uninitialized_copy_a(__x.begin(), __x.end(),
  844.                                     this->_M_impl._M_start,
  845.                                     _M_get_Tp_allocator()); }
  846.  
  847. #if __cplusplus >= 201103L
  848.       /**
  849.        *  @brief  %Deque move constructor.
  850.        *  @param  __x  A %deque of identical element and allocator types.
  851.        *
  852.        *  The newly-created %deque contains the exact contents of @a __x.
  853.        *  The contents of @a __x are a valid, but unspecified %deque.
  854.        */
  855.       deque(deque&& __x)
  856.       : _Base(std::move(__x)) { }
  857.  
  858.       /**
  859.        *  @brief  Builds a %deque from an initializer list.
  860.        *  @param  __l  An initializer_list.
  861.        *  @param  __a  An allocator object.
  862.        *
  863.        *  Create a %deque consisting of copies of the elements in the
  864.        *  initializer_list @a __l.
  865.        *
  866.        *  This will call the element type's copy constructor N times
  867.        *  (where N is __l.size()) and do no memory reallocation.
  868.        */
  869.       deque(initializer_list<value_type> __l,
  870.             const allocator_type& __a = allocator_type())
  871.       : _Base(__a)
  872.       {
  873.         _M_range_initialize(__l.begin(), __l.end(),
  874.                             random_access_iterator_tag());
  875.       }
  876. #endif
  877.  
  878.       /**
  879.        *  @brief  Builds a %deque from a range.
  880.        *  @param  __first  An input iterator.
  881.        *  @param  __last  An input iterator.
  882.        *  @param  __a  An allocator object.
  883.        *
  884.        *  Create a %deque consisting of copies of the elements from [__first,
  885.        *  __last).
  886.        *
  887.        *  If the iterators are forward, bidirectional, or random-access, then
  888.        *  this will call the elements' copy constructor N times (where N is
  889.        *  distance(__first,__last)) and do no memory reallocation.  But if only
  890.        *  input iterators are used, then this will do at most 2N calls to the
  891.        *  copy constructor, and logN memory reallocations.
  892.        */
  893. #if __cplusplus >= 201103L
  894.       template<typename _InputIterator,
  895.                typename = std::_RequireInputIter<_InputIterator>>
  896.         deque(_InputIterator __first, _InputIterator __last,
  897.               const allocator_type& __a = allocator_type())
  898.         : _Base(__a)
  899.         { _M_initialize_dispatch(__first, __last, __false_type()); }
  900. #else
  901.       template<typename _InputIterator>
  902.         deque(_InputIterator __first, _InputIterator __last,
  903.               const allocator_type& __a = allocator_type())
  904.         : _Base(__a)
  905.         {
  906.           // Check whether it's an integral type.  If so, it's not an iterator.
  907.           typedef typename std::__is_integer<_InputIterator>::__type _Integral;
  908.           _M_initialize_dispatch(__first, __last, _Integral());
  909.         }
  910. #endif
  911.  
  912.       /**
  913.        *  The dtor only erases the elements, and note that if the elements
  914.        *  themselves are pointers, the pointed-to memory is not touched in any
  915.        *  way.  Managing the pointer is the user's responsibility.
  916.        */
  917.       ~deque() _GLIBCXX_NOEXCEPT
  918.       { _M_destroy_data(begin(), end(), _M_get_Tp_allocator()); }
  919.  
  920.       /**
  921.        *  @brief  %Deque assignment operator.
  922.        *  @param  __x  A %deque of identical element and allocator types.
  923.        *
  924.        *  All the elements of @a x are copied, but unlike the copy constructor,
  925.        *  the allocator object is not copied.
  926.        */
  927.       deque&
  928.       operator=(const deque& __x);
  929.  
  930. #if __cplusplus >= 201103L
  931.       /**
  932.        *  @brief  %Deque move assignment operator.
  933.        *  @param  __x  A %deque of identical element and allocator types.
  934.        *
  935.        *  The contents of @a __x are moved into this deque (without copying).
  936.        *  @a __x is a valid, but unspecified %deque.
  937.        */
  938.       deque&
  939.       operator=(deque&& __x)
  940.       {
  941.         // NB: DR 1204.
  942.         // NB: DR 675.
  943.         this->clear();
  944.         this->swap(__x);
  945.         return *this;
  946.       }
  947.  
  948.       /**
  949.        *  @brief  Assigns an initializer list to a %deque.
  950.        *  @param  __l  An initializer_list.
  951.        *
  952.        *  This function fills a %deque with copies of the elements in the
  953.        *  initializer_list @a __l.
  954.        *
  955.        *  Note that the assignment completely changes the %deque and that the
  956.        *  resulting %deque's size is the same as the number of elements
  957.        *  assigned.  Old data may be lost.
  958.        */
  959.       deque&
  960.       operator=(initializer_list<value_type> __l)
  961.       {
  962.         this->assign(__l.begin(), __l.end());
  963.         return *this;
  964.       }
  965. #endif
  966.  
  967.       /**
  968.        *  @brief  Assigns a given value to a %deque.
  969.        *  @param  __n  Number of elements to be assigned.
  970.        *  @param  __val  Value to be assigned.
  971.        *
  972.        *  This function fills a %deque with @a n copies of the given
  973.        *  value.  Note that the assignment completely changes the
  974.        *  %deque and that the resulting %deque's size is the same as
  975.        *  the number of elements assigned.  Old data may be lost.
  976.        */
  977.       void
  978.       assign(size_type __n, const value_type& __val)
  979.       { _M_fill_assign(__n, __val); }
  980.  
  981.       /**
  982.        *  @brief  Assigns a range to a %deque.
  983.        *  @param  __first  An input iterator.
  984.        *  @param  __last   An input iterator.
  985.        *
  986.        *  This function fills a %deque with copies of the elements in the
  987.        *  range [__first,__last).
  988.        *
  989.        *  Note that the assignment completely changes the %deque and that the
  990.        *  resulting %deque's size is the same as the number of elements
  991.        *  assigned.  Old data may be lost.
  992.        */
  993. #if __cplusplus >= 201103L
  994.       template<typename _InputIterator,
  995.                typename = std::_RequireInputIter<_InputIterator>>
  996.         void
  997.         assign(_InputIterator __first, _InputIterator __last)
  998.         { _M_assign_dispatch(__first, __last, __false_type()); }
  999. #else
  1000.       template<typename _InputIterator>
  1001.         void
  1002.         assign(_InputIterator __first, _InputIterator __last)
  1003.         {
  1004.           typedef typename std::__is_integer<_InputIterator>::__type _Integral;
  1005.           _M_assign_dispatch(__first, __last, _Integral());
  1006.         }
  1007. #endif
  1008.  
  1009. #if __cplusplus >= 201103L
  1010.       /**
  1011.        *  @brief  Assigns an initializer list to a %deque.
  1012.        *  @param  __l  An initializer_list.
  1013.        *
  1014.        *  This function fills a %deque with copies of the elements in the
  1015.        *  initializer_list @a __l.
  1016.        *
  1017.        *  Note that the assignment completely changes the %deque and that the
  1018.        *  resulting %deque's size is the same as the number of elements
  1019.        *  assigned.  Old data may be lost.
  1020.        */
  1021.       void
  1022.       assign(initializer_list<value_type> __l)
  1023.       { this->assign(__l.begin(), __l.end()); }
  1024. #endif
  1025.  
  1026.       /// Get a copy of the memory allocation object.
  1027.       allocator_type
  1028.       get_allocator() const _GLIBCXX_NOEXCEPT
  1029.       { return _Base::get_allocator(); }
  1030.  
  1031.       // iterators
  1032.       /**
  1033.        *  Returns a read/write iterator that points to the first element in the
  1034.        *  %deque.  Iteration is done in ordinary element order.
  1035.        */
  1036.       iterator
  1037.       begin() _GLIBCXX_NOEXCEPT
  1038.       { return this->_M_impl._M_start; }
  1039.  
  1040.       /**
  1041.        *  Returns a read-only (constant) iterator that points to the first
  1042.        *  element in the %deque.  Iteration is done in ordinary element order.
  1043.        */
  1044.       const_iterator
  1045.       begin() const _GLIBCXX_NOEXCEPT
  1046.       { return this->_M_impl._M_start; }
  1047.  
  1048.       /**
  1049.        *  Returns a read/write iterator that points one past the last
  1050.        *  element in the %deque.  Iteration is done in ordinary
  1051.        *  element order.
  1052.        */
  1053.       iterator
  1054.       end() _GLIBCXX_NOEXCEPT
  1055.       { return this->_M_impl._M_finish; }
  1056.  
  1057.       /**
  1058.        *  Returns a read-only (constant) iterator that points one past
  1059.        *  the last element in the %deque.  Iteration is done in
  1060.        *  ordinary element order.
  1061.        */
  1062.       const_iterator
  1063.       end() const _GLIBCXX_NOEXCEPT
  1064.       { return this->_M_impl._M_finish; }
  1065.  
  1066.       /**
  1067.        *  Returns a read/write reverse iterator that points to the
  1068.        *  last element in the %deque.  Iteration is done in reverse
  1069.        *  element order.
  1070.        */
  1071.       reverse_iterator
  1072.       rbegin() _GLIBCXX_NOEXCEPT
  1073.       { return reverse_iterator(this->_M_impl._M_finish); }
  1074.  
  1075.       /**
  1076.        *  Returns a read-only (constant) reverse iterator that points
  1077.        *  to the last element in the %deque.  Iteration is done in
  1078.        *  reverse element order.
  1079.        */
  1080.       const_reverse_iterator
  1081.       rbegin() const _GLIBCXX_NOEXCEPT
  1082.       { return const_reverse_iterator(this->_M_impl._M_finish); }
  1083.  
  1084.       /**
  1085.        *  Returns a read/write reverse iterator that points to one
  1086.        *  before the first element in the %deque.  Iteration is done
  1087.        *  in reverse element order.
  1088.        */
  1089.       reverse_iterator
  1090.       rend() _GLIBCXX_NOEXCEPT
  1091.       { return reverse_iterator(this->_M_impl._M_start); }
  1092.  
  1093.       /**
  1094.        *  Returns a read-only (constant) reverse iterator that points
  1095.        *  to one before the first element in the %deque.  Iteration is
  1096.        *  done in reverse element order.
  1097.        */
  1098.       const_reverse_iterator
  1099.       rend() const _GLIBCXX_NOEXCEPT
  1100.       { return const_reverse_iterator(this->_M_impl._M_start); }
  1101.  
  1102. #if __cplusplus >= 201103L
  1103.       /**
  1104.        *  Returns a read-only (constant) iterator that points to the first
  1105.        *  element in the %deque.  Iteration is done in ordinary element order.
  1106.        */
  1107.       const_iterator
  1108.       cbegin() const noexcept
  1109.       { return this->_M_impl._M_start; }
  1110.  
  1111.       /**
  1112.        *  Returns a read-only (constant) iterator that points one past
  1113.        *  the last element in the %deque.  Iteration is done in
  1114.        *  ordinary element order.
  1115.        */
  1116.       const_iterator
  1117.       cend() const noexcept
  1118.       { return this->_M_impl._M_finish; }
  1119.  
  1120.       /**
  1121.        *  Returns a read-only (constant) reverse iterator that points
  1122.        *  to the last element in the %deque.  Iteration is done in
  1123.        *  reverse element order.
  1124.        */
  1125.       const_reverse_iterator
  1126.       crbegin() const noexcept
  1127.       { return const_reverse_iterator(this->_M_impl._M_finish); }
  1128.  
  1129.       /**
  1130.        *  Returns a read-only (constant) reverse iterator that points
  1131.        *  to one before the first element in the %deque.  Iteration is
  1132.        *  done in reverse element order.
  1133.        */
  1134.       const_reverse_iterator
  1135.       crend() const noexcept
  1136.       { return const_reverse_iterator(this->_M_impl._M_start); }
  1137. #endif
  1138.  
  1139.       // [23.2.1.2] capacity
  1140.       /**  Returns the number of elements in the %deque.  */
  1141.       size_type
  1142.       size() const _GLIBCXX_NOEXCEPT
  1143.       { return this->_M_impl._M_finish - this->_M_impl._M_start; }
  1144.  
  1145.       /**  Returns the size() of the largest possible %deque.  */
  1146.       size_type
  1147.       max_size() const _GLIBCXX_NOEXCEPT
  1148.       { return _M_get_Tp_allocator().max_size(); }
  1149.  
  1150. #if __cplusplus >= 201103L
  1151.       /**
  1152.        *  @brief  Resizes the %deque to the specified number of elements.
  1153.        *  @param  __new_size  Number of elements the %deque should contain.
  1154.        *
  1155.        *  This function will %resize the %deque to the specified
  1156.        *  number of elements.  If the number is smaller than the
  1157.        *  %deque's current size the %deque is truncated, otherwise
  1158.        *  default constructed elements are appended.
  1159.        */
  1160.       void
  1161.       resize(size_type __new_size)
  1162.       {
  1163.         const size_type __len = size();
  1164.         if (__new_size > __len)
  1165.           _M_default_append(__new_size - __len);
  1166.         else if (__new_size < __len)
  1167.           _M_erase_at_end(this->_M_impl._M_start
  1168.                           + difference_type(__new_size));
  1169.       }
  1170.  
  1171.       /**
  1172.        *  @brief  Resizes the %deque to the specified number of elements.
  1173.        *  @param  __new_size  Number of elements the %deque should contain.
  1174.        *  @param  __x  Data with which new elements should be populated.
  1175.        *
  1176.        *  This function will %resize the %deque to the specified
  1177.        *  number of elements.  If the number is smaller than the
  1178.        *  %deque's current size the %deque is truncated, otherwise the
  1179.        *  %deque is extended and new elements are populated with given
  1180.        *  data.
  1181.        */
  1182.       void
  1183.       resize(size_type __new_size, const value_type& __x)
  1184.       {
  1185.         const size_type __len = size();
  1186.         if (__new_size > __len)
  1187.           insert(this->_M_impl._M_finish, __new_size - __len, __x);
  1188.         else if (__new_size < __len)
  1189.           _M_erase_at_end(this->_M_impl._M_start
  1190.                           + difference_type(__new_size));
  1191.       }
  1192. #else
  1193.       /**
  1194.        *  @brief  Resizes the %deque to the specified number of elements.
  1195.        *  @param  __new_size  Number of elements the %deque should contain.
  1196.        *  @param  __x  Data with which new elements should be populated.
  1197.        *
  1198.        *  This function will %resize the %deque to the specified
  1199.        *  number of elements.  If the number is smaller than the
  1200.        *  %deque's current size the %deque is truncated, otherwise the
  1201.        *  %deque is extended and new elements are populated with given
  1202.        *  data.
  1203.        */
  1204.       void
  1205.       resize(size_type __new_size, value_type __x = value_type())
  1206.       {
  1207.         const size_type __len = size();
  1208.         if (__new_size > __len)
  1209.           insert(this->_M_impl._M_finish, __new_size - __len, __x);
  1210.         else if (__new_size < __len)
  1211.           _M_erase_at_end(this->_M_impl._M_start
  1212.                           + difference_type(__new_size));
  1213.       }
  1214. #endif
  1215.  
  1216. #if __cplusplus >= 201103L
  1217.       /**  A non-binding request to reduce memory use.  */
  1218.       void
  1219.       shrink_to_fit()
  1220.       { _M_shrink_to_fit(); }
  1221. #endif
  1222.  
  1223.       /**
  1224.        *  Returns true if the %deque is empty.  (Thus begin() would
  1225.        *  equal end().)
  1226.        */
  1227.       bool
  1228.       empty() const _GLIBCXX_NOEXCEPT
  1229.       { return this->_M_impl._M_finish == this->_M_impl._M_start; }
  1230.  
  1231.       // element access
  1232.       /**
  1233.        *  @brief Subscript access to the data contained in the %deque.
  1234.        *  @param __n The index of the element for which data should be
  1235.        *  accessed.
  1236.        *  @return  Read/write reference to data.
  1237.        *
  1238.        *  This operator allows for easy, array-style, data access.
  1239.        *  Note that data access with this operator is unchecked and
  1240.        *  out_of_range lookups are not defined. (For checked lookups
  1241.        *  see at().)
  1242.        */
  1243.       reference
  1244.       operator[](size_type __n)
  1245.       { return this->_M_impl._M_start[difference_type(__n)]; }
  1246.  
  1247.       /**
  1248.        *  @brief Subscript access to the data contained in the %deque.
  1249.        *  @param __n The index of the element for which data should be
  1250.        *  accessed.
  1251.        *  @return  Read-only (constant) reference to data.
  1252.        *
  1253.        *  This operator allows for easy, array-style, data access.
  1254.        *  Note that data access with this operator is unchecked and
  1255.        *  out_of_range lookups are not defined. (For checked lookups
  1256.        *  see at().)
  1257.        */
  1258.       const_reference
  1259.       operator[](size_type __n) const
  1260.       { return this->_M_impl._M_start[difference_type(__n)]; }
  1261.  
  1262.     protected:
  1263.       /// Safety check used only from at().
  1264.       void
  1265.       _M_range_check(size_type __n) const
  1266.       {
  1267.         if (__n >= this->size())
  1268.           __throw_out_of_range(__N("deque::_M_range_check"));
  1269.       }
  1270.  
  1271.     public:
  1272.       /**
  1273.        *  @brief  Provides access to the data contained in the %deque.
  1274.        *  @param __n The index of the element for which data should be
  1275.        *  accessed.
  1276.        *  @return  Read/write reference to data.
  1277.        *  @throw  std::out_of_range  If @a __n is an invalid index.
  1278.        *
  1279.        *  This function provides for safer data access.  The parameter
  1280.        *  is first checked that it is in the range of the deque.  The
  1281.        *  function throws out_of_range if the check fails.
  1282.        */
  1283.       reference
  1284.       at(size_type __n)
  1285.       {
  1286.         _M_range_check(__n);
  1287.         return (*this)[__n];
  1288.       }
  1289.  
  1290.       /**
  1291.        *  @brief  Provides access to the data contained in the %deque.
  1292.        *  @param __n The index of the element for which data should be
  1293.        *  accessed.
  1294.        *  @return  Read-only (constant) reference to data.
  1295.        *  @throw  std::out_of_range  If @a __n is an invalid index.
  1296.        *
  1297.        *  This function provides for safer data access.  The parameter is first
  1298.        *  checked that it is in the range of the deque.  The function throws
  1299.        *  out_of_range if the check fails.
  1300.        */
  1301.       const_reference
  1302.       at(size_type __n) const
  1303.       {
  1304.         _M_range_check(__n);
  1305.         return (*this)[__n];
  1306.       }
  1307.  
  1308.       /**
  1309.        *  Returns a read/write reference to the data at the first
  1310.        *  element of the %deque.
  1311.        */
  1312.       reference
  1313.       front()
  1314.       { return *begin(); }
  1315.  
  1316.       /**
  1317.        *  Returns a read-only (constant) reference to the data at the first
  1318.        *  element of the %deque.
  1319.        */
  1320.       const_reference
  1321.       front() const
  1322.       { return *begin(); }
  1323.  
  1324.       /**
  1325.        *  Returns a read/write reference to the data at the last element of the
  1326.        *  %deque.
  1327.        */
  1328.       reference
  1329.       back()
  1330.       {
  1331.         iterator __tmp = end();
  1332.         --__tmp;
  1333.         return *__tmp;
  1334.       }
  1335.  
  1336.       /**
  1337.        *  Returns a read-only (constant) reference to the data at the last
  1338.        *  element of the %deque.
  1339.        */
  1340.       const_reference
  1341.       back() const
  1342.       {
  1343.         const_iterator __tmp = end();
  1344.         --__tmp;
  1345.         return *__tmp;
  1346.       }
  1347.  
  1348.       // [23.2.1.2] modifiers
  1349.       /**
  1350.        *  @brief  Add data to the front of the %deque.
  1351.        *  @param  __x  Data to be added.
  1352.        *
  1353.        *  This is a typical stack operation.  The function creates an
  1354.        *  element at the front of the %deque and assigns the given
  1355.        *  data to it.  Due to the nature of a %deque this operation
  1356.        *  can be done in constant time.
  1357.        */
  1358.       void
  1359.       push_front(const value_type& __x)
  1360.       {
  1361.         if (this->_M_impl._M_start._M_cur != this->_M_impl._M_start._M_first)
  1362.           {
  1363.             this->_M_impl.construct(this->_M_impl._M_start._M_cur - 1, __x);
  1364.             --this->_M_impl._M_start._M_cur;
  1365.           }
  1366.         else
  1367.           _M_push_front_aux(__x);
  1368.       }
  1369.  
  1370. #if __cplusplus >= 201103L
  1371.       void
  1372.       push_front(value_type&& __x)
  1373.       { emplace_front(std::move(__x)); }
  1374.  
  1375.       template<typename... _Args>
  1376.         void
  1377.         emplace_front(_Args&&... __args);
  1378. #endif
  1379.  
  1380.       /**
  1381.        *  @brief  Add data to the end of the %deque.
  1382.        *  @param  __x  Data to be added.
  1383.        *
  1384.        *  This is a typical stack operation.  The function creates an
  1385.        *  element at the end of the %deque and assigns the given data
  1386.        *  to it.  Due to the nature of a %deque this operation can be
  1387.        *  done in constant time.
  1388.        */
  1389.       void
  1390.       push_back(const value_type& __x)
  1391.       {
  1392.         if (this->_M_impl._M_finish._M_cur
  1393.             != this->_M_impl._M_finish._M_last - 1)
  1394.           {
  1395.             this->_M_impl.construct(this->_M_impl._M_finish._M_cur, __x);
  1396.             ++this->_M_impl._M_finish._M_cur;
  1397.           }
  1398.         else
  1399.           _M_push_back_aux(__x);
  1400.       }
  1401.  
  1402. #if __cplusplus >= 201103L
  1403.       void
  1404.       push_back(value_type&& __x)
  1405.       { emplace_back(std::move(__x)); }
  1406.  
  1407.       template<typename... _Args>
  1408.         void
  1409.         emplace_back(_Args&&... __args);
  1410. #endif
  1411.  
  1412.       /**
  1413.        *  @brief  Removes first element.
  1414.        *
  1415.        *  This is a typical stack operation.  It shrinks the %deque by one.
  1416.        *
  1417.        *  Note that no data is returned, and if the first element's data is
  1418.        *  needed, it should be retrieved before pop_front() is called.
  1419.        */
  1420.       void
  1421.       pop_front()
  1422.       {
  1423.         if (this->_M_impl._M_start._M_cur
  1424.             != this->_M_impl._M_start._M_last - 1)
  1425.           {
  1426.             this->_M_impl.destroy(this->_M_impl._M_start._M_cur);
  1427.             ++this->_M_impl._M_start._M_cur;
  1428.           }
  1429.         else
  1430.           _M_pop_front_aux();
  1431.       }
  1432.  
  1433.       /**
  1434.        *  @brief  Removes last element.
  1435.        *
  1436.        *  This is a typical stack operation.  It shrinks the %deque by one.
  1437.        *
  1438.        *  Note that no data is returned, and if the last element's data is
  1439.        *  needed, it should be retrieved before pop_back() is called.
  1440.        */
  1441.       void
  1442.       pop_back()
  1443.       {
  1444.         if (this->_M_impl._M_finish._M_cur
  1445.             != this->_M_impl._M_finish._M_first)
  1446.           {
  1447.             --this->_M_impl._M_finish._M_cur;
  1448.             this->_M_impl.destroy(this->_M_impl._M_finish._M_cur);
  1449.           }
  1450.         else
  1451.           _M_pop_back_aux();
  1452.       }
  1453.  
  1454. #if __cplusplus >= 201103L
  1455.       /**
  1456.        *  @brief  Inserts an object in %deque before specified iterator.
  1457.        *  @param  __position  An iterator into the %deque.
  1458.        *  @param  __args  Arguments.
  1459.        *  @return  An iterator that points to the inserted data.
  1460.        *
  1461.        *  This function will insert an object of type T constructed
  1462.        *  with T(std::forward<Args>(args)...) before the specified location.
  1463.        */
  1464.       template<typename... _Args>
  1465.         iterator
  1466.         emplace(iterator __position, _Args&&... __args);
  1467. #endif
  1468.  
  1469.       /**
  1470.        *  @brief  Inserts given value into %deque before specified iterator.
  1471.        *  @param  __position  An iterator into the %deque.
  1472.        *  @param  __x  Data to be inserted.
  1473.        *  @return  An iterator that points to the inserted data.
  1474.        *
  1475.        *  This function will insert a copy of the given value before the
  1476.        *  specified location.
  1477.        */
  1478.       iterator
  1479.       insert(iterator __position, const value_type& __x);
  1480.  
  1481. #if __cplusplus >= 201103L
  1482.       /**
  1483.        *  @brief  Inserts given rvalue into %deque before specified iterator.
  1484.        *  @param  __position  An iterator into the %deque.
  1485.        *  @param  __x  Data to be inserted.
  1486.        *  @return  An iterator that points to the inserted data.
  1487.        *
  1488.        *  This function will insert a copy of the given rvalue before the
  1489.        *  specified location.
  1490.        */
  1491.       iterator
  1492.       insert(iterator __position, value_type&& __x)
  1493.       { return emplace(__position, std::move(__x)); }
  1494.  
  1495.       /**
  1496.        *  @brief  Inserts an initializer list into the %deque.
  1497.        *  @param  __p  An iterator into the %deque.
  1498.        *  @param  __l  An initializer_list.
  1499.        *
  1500.        *  This function will insert copies of the data in the
  1501.        *  initializer_list @a __l into the %deque before the location
  1502.        *  specified by @a __p.  This is known as <em>list insert</em>.
  1503.        */
  1504.       void
  1505.       insert(iterator __p, initializer_list<value_type> __l)
  1506.       { this->insert(__p, __l.begin(), __l.end()); }
  1507. #endif
  1508.  
  1509.       /**
  1510.        *  @brief  Inserts a number of copies of given data into the %deque.
  1511.        *  @param  __position  An iterator into the %deque.
  1512.        *  @param  __n  Number of elements to be inserted.
  1513.        *  @param  __x  Data to be inserted.
  1514.        *
  1515.        *  This function will insert a specified number of copies of the given
  1516.        *  data before the location specified by @a __position.
  1517.        */
  1518.       void
  1519.       insert(iterator __position, size_type __n, const value_type& __x)
  1520.       { _M_fill_insert(__position, __n, __x); }
  1521.  
  1522.       /**
  1523.        *  @brief  Inserts a range into the %deque.
  1524.        *  @param  __position  An iterator into the %deque.
  1525.        *  @param  __first  An input iterator.
  1526.        *  @param  __last   An input iterator.
  1527.        *
  1528.        *  This function will insert copies of the data in the range
  1529.        *  [__first,__last) into the %deque before the location specified
  1530.        *  by @a __position.  This is known as <em>range insert</em>.
  1531.        */
  1532. #if __cplusplus >= 201103L
  1533.       template<typename _InputIterator,
  1534.                typename = std::_RequireInputIter<_InputIterator>>
  1535.         void
  1536.         insert(iterator __position, _InputIterator __first,
  1537.                _InputIterator __last)
  1538.         { _M_insert_dispatch(__position, __first, __last, __false_type()); }
  1539. #else
  1540.       template<typename _InputIterator>
  1541.         void
  1542.         insert(iterator __position, _InputIterator __first,
  1543.                _InputIterator __last)
  1544.         {
  1545.           // Check whether it's an integral type.  If so, it's not an iterator.
  1546.           typedef typename std::__is_integer<_InputIterator>::__type _Integral;
  1547.           _M_insert_dispatch(__position, __first, __last, _Integral());
  1548.         }
  1549. #endif
  1550.  
  1551.       /**
  1552.        *  @brief  Remove element at given position.
  1553.        *  @param  __position  Iterator pointing to element to be erased.
  1554.        *  @return  An iterator pointing to the next element (or end()).
  1555.        *
  1556.        *  This function will erase the element at the given position and thus
  1557.        *  shorten the %deque by one.
  1558.        *
  1559.        *  The user is cautioned that
  1560.        *  this function only erases the element, and that if the element is
  1561.        *  itself a pointer, the pointed-to memory is not touched in any way.
  1562.        *  Managing the pointer is the user's responsibility.
  1563.        */
  1564.       iterator
  1565.       erase(iterator __position);
  1566.  
  1567.       /**
  1568.        *  @brief  Remove a range of elements.
  1569.        *  @param  __first  Iterator pointing to the first element to be erased.
  1570.        *  @param  __last  Iterator pointing to one past the last element to be
  1571.        *                erased.
  1572.        *  @return  An iterator pointing to the element pointed to by @a last
  1573.        *           prior to erasing (or end()).
  1574.        *
  1575.        *  This function will erase the elements in the range
  1576.        *  [__first,__last) and shorten the %deque accordingly.
  1577.        *
  1578.        *  The user is cautioned that
  1579.        *  this function only erases the elements, and that if the elements
  1580.        *  themselves are pointers, the pointed-to memory is not touched in any
  1581.        *  way.  Managing the pointer is the user's responsibility.
  1582.        */
  1583.       iterator
  1584.       erase(iterator __first, iterator __last);
  1585.  
  1586.       /**
  1587.        *  @brief  Swaps data with another %deque.
  1588.        *  @param  __x  A %deque of the same element and allocator types.
  1589.        *
  1590.        *  This exchanges the elements between two deques in constant time.
  1591.        *  (Four pointers, so it should be quite fast.)
  1592.        *  Note that the global std::swap() function is specialized such that
  1593.        *  std::swap(d1,d2) will feed to this function.
  1594.        */
  1595.       void
  1596.       swap(deque& __x)
  1597.       {
  1598.         std::swap(this->_M_impl._M_start, __x._M_impl._M_start);
  1599.         std::swap(this->_M_impl._M_finish, __x._M_impl._M_finish);
  1600.         std::swap(this->_M_impl._M_map, __x._M_impl._M_map);
  1601.         std::swap(this->_M_impl._M_map_size, __x._M_impl._M_map_size);
  1602.  
  1603.         // _GLIBCXX_RESOLVE_LIB_DEFECTS
  1604.         // 431. Swapping containers with unequal allocators.
  1605.         std::__alloc_swap<_Tp_alloc_type>::_S_do_it(_M_get_Tp_allocator(),
  1606.                                                     __x._M_get_Tp_allocator());
  1607.       }
  1608.  
  1609.       /**
  1610.        *  Erases all the elements.  Note that this function only erases the
  1611.        *  elements, and that if the elements themselves are pointers, the
  1612.        *  pointed-to memory is not touched in any way.  Managing the pointer is
  1613.        *  the user's responsibility.
  1614.        */
  1615.       void
  1616.       clear() _GLIBCXX_NOEXCEPT
  1617.       { _M_erase_at_end(begin()); }
  1618.  
  1619.     protected:
  1620.       // Internal constructor functions follow.
  1621.  
  1622.       // called by the range constructor to implement [23.1.1]/9
  1623.  
  1624.       // _GLIBCXX_RESOLVE_LIB_DEFECTS
  1625.       // 438. Ambiguity in the "do the right thing" clause
  1626.       template<typename _Integer>
  1627.         void
  1628.         _M_initialize_dispatch(_Integer __n, _Integer __x, __true_type)
  1629.         {
  1630.           _M_initialize_map(static_cast<size_type>(__n));
  1631.           _M_fill_initialize(__x);
  1632.         }
  1633.  
  1634.       // called by the range constructor to implement [23.1.1]/9
  1635.       template<typename _InputIterator>
  1636.         void
  1637.         _M_initialize_dispatch(_InputIterator __first, _InputIterator __last,
  1638.                                __false_type)
  1639.         {
  1640.           typedef typename std::iterator_traits<_InputIterator>::
  1641.             iterator_category _IterCategory;
  1642.           _M_range_initialize(__first, __last, _IterCategory());
  1643.         }
  1644.  
  1645.       // called by the second initialize_dispatch above
  1646.       //@{
  1647.       /**
  1648.        *  @brief Fills the deque with whatever is in [first,last).
  1649.        *  @param  __first  An input iterator.
  1650.        *  @param  __last  An input iterator.
  1651.        *  @return   Nothing.
  1652.        *
  1653.        *  If the iterators are actually forward iterators (or better), then the
  1654.        *  memory layout can be done all at once.  Else we move forward using
  1655.        *  push_back on each value from the iterator.
  1656.        */
  1657.       template<typename _InputIterator>
  1658.         void
  1659.         _M_range_initialize(_InputIterator __first, _InputIterator __last,
  1660.                             std::input_iterator_tag);
  1661.  
  1662.       // called by the second initialize_dispatch above
  1663.       template<typename _ForwardIterator>
  1664.         void
  1665.         _M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
  1666.                             std::forward_iterator_tag);
  1667.       //@}
  1668.  
  1669.       /**
  1670.        *  @brief Fills the %deque with copies of value.
  1671.        *  @param  __value  Initial value.
  1672.        *  @return   Nothing.
  1673.        *  @pre _M_start and _M_finish have already been initialized,
  1674.        *  but none of the %deque's elements have yet been constructed.
  1675.        *
  1676.        *  This function is called only when the user provides an explicit size
  1677.        *  (with or without an explicit exemplar value).
  1678.        */
  1679.       void
  1680.       _M_fill_initialize(const value_type& __value);
  1681.  
  1682. #if __cplusplus >= 201103L
  1683.       // called by deque(n).
  1684.       void
  1685.       _M_default_initialize();
  1686. #endif
  1687.  
  1688.       // Internal assign functions follow.  The *_aux functions do the actual
  1689.       // assignment work for the range versions.
  1690.  
  1691.       // called by the range assign to implement [23.1.1]/9
  1692.  
  1693.       // _GLIBCXX_RESOLVE_LIB_DEFECTS
  1694.       // 438. Ambiguity in the "do the right thing" clause
  1695.       template<typename _Integer>
  1696.         void
  1697.         _M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
  1698.         { _M_fill_assign(__n, __val); }
  1699.  
  1700.       // called by the range assign to implement [23.1.1]/9
  1701.       template<typename _InputIterator>
  1702.         void
  1703.         _M_assign_dispatch(_InputIterator __first, _InputIterator __last,
  1704.                            __false_type)
  1705.         {
  1706.           typedef typename std::iterator_traits<_InputIterator>::
  1707.             iterator_category _IterCategory;
  1708.           _M_assign_aux(__first, __last, _IterCategory());
  1709.         }
  1710.  
  1711.       // called by the second assign_dispatch above
  1712.       template<typename _InputIterator>
  1713.         void
  1714.         _M_assign_aux(_InputIterator __first, _InputIterator __last,
  1715.                       std::input_iterator_tag);
  1716.  
  1717.       // called by the second assign_dispatch above
  1718.       template<typename _ForwardIterator>
  1719.         void
  1720.         _M_assign_aux(_ForwardIterator __first, _ForwardIterator __last,
  1721.                       std::forward_iterator_tag)
  1722.         {
  1723.           const size_type __len = std::distance(__first, __last);
  1724.           if (__len > size())
  1725.             {
  1726.               _ForwardIterator __mid = __first;
  1727.               std::advance(__mid, size());
  1728.               std::copy(__first, __mid, begin());
  1729.               insert(end(), __mid, __last);
  1730.             }
  1731.           else
  1732.             _M_erase_at_end(std::copy(__first, __last, begin()));
  1733.         }
  1734.  
  1735.       // Called by assign(n,t), and the range assign when it turns out
  1736.       // to be the same thing.
  1737.       void
  1738.       _M_fill_assign(size_type __n, const value_type& __val)
  1739.       {
  1740.         if (__n > size())
  1741.           {
  1742.             std::fill(begin(), end(), __val);
  1743.             insert(end(), __n - size(), __val);
  1744.           }
  1745.         else
  1746.           {
  1747.             _M_erase_at_end(begin() + difference_type(__n));
  1748.             std::fill(begin(), end(), __val);
  1749.           }
  1750.       }
  1751.  
  1752.       //@{
  1753.       /// Helper functions for push_* and pop_*.
  1754. #if __cplusplus < 201103L
  1755.       void _M_push_back_aux(const value_type&);
  1756.  
  1757.       void _M_push_front_aux(const value_type&);
  1758. #else
  1759.       template<typename... _Args>
  1760.         void _M_push_back_aux(_Args&&... __args);
  1761.  
  1762.       template<typename... _Args>
  1763.         void _M_push_front_aux(_Args&&... __args);
  1764. #endif
  1765.  
  1766.       void _M_pop_back_aux();
  1767.  
  1768.       void _M_pop_front_aux();
  1769.       //@}
  1770.  
  1771.       // Internal insert functions follow.  The *_aux functions do the actual
  1772.       // insertion work when all shortcuts fail.
  1773.  
  1774.       // called by the range insert to implement [23.1.1]/9
  1775.  
  1776.       // _GLIBCXX_RESOLVE_LIB_DEFECTS
  1777.       // 438. Ambiguity in the "do the right thing" clause
  1778.       template<typename _Integer>
  1779.         void
  1780.         _M_insert_dispatch(iterator __pos,
  1781.                            _Integer __n, _Integer __x, __true_type)
  1782.         { _M_fill_insert(__pos, __n, __x); }
  1783.  
  1784.       // called by the range insert to implement [23.1.1]/9
  1785.       template<typename _InputIterator>
  1786.         void
  1787.         _M_insert_dispatch(iterator __pos,
  1788.                            _InputIterator __first, _InputIterator __last,
  1789.                            __false_type)
  1790.         {
  1791.           typedef typename std::iterator_traits<_InputIterator>::
  1792.             iterator_category _IterCategory;
  1793.           _M_range_insert_aux(__pos, __first, __last, _IterCategory());
  1794.         }
  1795.  
  1796.       // called by the second insert_dispatch above
  1797.       template<typename _InputIterator>
  1798.         void
  1799.         _M_range_insert_aux(iterator __pos, _InputIterator __first,
  1800.                             _InputIterator __last, std::input_iterator_tag);
  1801.  
  1802.       // called by the second insert_dispatch above
  1803.       template<typename _ForwardIterator>
  1804.         void
  1805.         _M_range_insert_aux(iterator __pos, _ForwardIterator __first,
  1806.                             _ForwardIterator __last, std::forward_iterator_tag);
  1807.  
  1808.       // Called by insert(p,n,x), and the range insert when it turns out to be
  1809.       // the same thing.  Can use fill functions in optimal situations,
  1810.       // otherwise passes off to insert_aux(p,n,x).
  1811.       void
  1812.       _M_fill_insert(iterator __pos, size_type __n, const value_type& __x);
  1813.  
  1814.       // called by insert(p,x)
  1815. #if __cplusplus < 201103L
  1816.       iterator
  1817.       _M_insert_aux(iterator __pos, const value_type& __x);
  1818. #else
  1819.       template<typename... _Args>
  1820.         iterator
  1821.         _M_insert_aux(iterator __pos, _Args&&... __args);
  1822. #endif
  1823.  
  1824.       // called by insert(p,n,x) via fill_insert
  1825.       void
  1826.       _M_insert_aux(iterator __pos, size_type __n, const value_type& __x);
  1827.  
  1828.       // called by range_insert_aux for forward iterators
  1829.       template<typename _ForwardIterator>
  1830.         void
  1831.         _M_insert_aux(iterator __pos,
  1832.                       _ForwardIterator __first, _ForwardIterator __last,
  1833.                       size_type __n);
  1834.  
  1835.  
  1836.       // Internal erase functions follow.
  1837.  
  1838.       void
  1839.       _M_destroy_data_aux(iterator __first, iterator __last);
  1840.  
  1841.       // Called by ~deque().
  1842.       // NB: Doesn't deallocate the nodes.
  1843.       template<typename _Alloc1>
  1844.         void
  1845.         _M_destroy_data(iterator __first, iterator __last, const _Alloc1&)
  1846.         { _M_destroy_data_aux(__first, __last); }
  1847.  
  1848.       void
  1849.       _M_destroy_data(iterator __first, iterator __last,
  1850.                       const std::allocator<_Tp>&)
  1851.       {
  1852.         if (!__has_trivial_destructor(value_type))
  1853.           _M_destroy_data_aux(__first, __last);
  1854.       }
  1855.  
  1856.       // Called by erase(q1, q2).
  1857.       void
  1858.       _M_erase_at_begin(iterator __pos)
  1859.       {
  1860.         _M_destroy_data(begin(), __pos, _M_get_Tp_allocator());
  1861.         _M_destroy_nodes(this->_M_impl._M_start._M_node, __pos._M_node);
  1862.         this->_M_impl._M_start = __pos;
  1863.       }
  1864.  
  1865.       // Called by erase(q1, q2), resize(), clear(), _M_assign_aux,
  1866.       // _M_fill_assign, operator=.
  1867.       void
  1868.       _M_erase_at_end(iterator __pos)
  1869.       {
  1870.         _M_destroy_data(__pos, end(), _M_get_Tp_allocator());
  1871.         _M_destroy_nodes(__pos._M_node + 1,
  1872.                          this->_M_impl._M_finish._M_node + 1);
  1873.         this->_M_impl._M_finish = __pos;
  1874.       }
  1875.  
  1876. #if __cplusplus >= 201103L
  1877.       // Called by resize(sz).
  1878.       void
  1879.       _M_default_append(size_type __n);
  1880.  
  1881.       bool
  1882.       _M_shrink_to_fit();
  1883. #endif
  1884.  
  1885.       //@{
  1886.       /// Memory-handling helpers for the previous internal insert functions.
  1887.       iterator
  1888.       _M_reserve_elements_at_front(size_type __n)
  1889.       {
  1890.         const size_type __vacancies = this->_M_impl._M_start._M_cur
  1891.                                       - this->_M_impl._M_start._M_first;
  1892.         if (__n > __vacancies)
  1893.           _M_new_elements_at_front(__n - __vacancies);
  1894.         return this->_M_impl._M_start - difference_type(__n);
  1895.       }
  1896.  
  1897.       iterator
  1898.       _M_reserve_elements_at_back(size_type __n)
  1899.       {
  1900.         const size_type __vacancies = (this->_M_impl._M_finish._M_last
  1901.                                        - this->_M_impl._M_finish._M_cur) - 1;
  1902.         if (__n > __vacancies)
  1903.           _M_new_elements_at_back(__n - __vacancies);
  1904.         return this->_M_impl._M_finish + difference_type(__n);
  1905.       }
  1906.  
  1907.       void
  1908.       _M_new_elements_at_front(size_type __new_elements);
  1909.  
  1910.       void
  1911.       _M_new_elements_at_back(size_type __new_elements);
  1912.       //@}
  1913.  
  1914.  
  1915.       //@{
  1916.       /**
  1917.        *  @brief Memory-handling helpers for the major %map.
  1918.        *
  1919.        *  Makes sure the _M_map has space for new nodes.  Does not
  1920.        *  actually add the nodes.  Can invalidate _M_map pointers.
  1921.        *  (And consequently, %deque iterators.)
  1922.        */
  1923.       void
  1924.       _M_reserve_map_at_back(size_type __nodes_to_add = 1)
  1925.       {
  1926.         if (__nodes_to_add + 1 > this->_M_impl._M_map_size
  1927.             - (this->_M_impl._M_finish._M_node - this->_M_impl._M_map))
  1928.           _M_reallocate_map(__nodes_to_add, false);
  1929.       }
  1930.  
  1931.       void
  1932.       _M_reserve_map_at_front(size_type __nodes_to_add = 1)
  1933.       {
  1934.         if (__nodes_to_add > size_type(this->_M_impl._M_start._M_node
  1935.                                        - this->_M_impl._M_map))
  1936.           _M_reallocate_map(__nodes_to_add, true);
  1937.       }
  1938.  
  1939.       void
  1940.       _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front);
  1941.       //@}
  1942.     };
  1943.  
  1944.  
  1945.   /**
  1946.    *  @brief  Deque equality comparison.
  1947.    *  @param  __x  A %deque.
  1948.    *  @param  __y  A %deque of the same type as @a __x.
  1949.    *  @return  True iff the size and elements of the deques are equal.
  1950.    *
  1951.    *  This is an equivalence relation.  It is linear in the size of the
  1952.    *  deques.  Deques are considered equivalent if their sizes are equal,
  1953.    *  and if corresponding elements compare equal.
  1954.   */
  1955.   template<typename _Tp, typename _Alloc>
  1956.     inline bool
  1957.     operator==(const deque<_Tp, _Alloc>& __x,
  1958.                          const deque<_Tp, _Alloc>& __y)
  1959.     { return __x.size() == __y.size()
  1960.              && std::equal(__x.begin(), __x.end(), __y.begin()); }
  1961.  
  1962.   /**
  1963.    *  @brief  Deque ordering relation.
  1964.    *  @param  __x  A %deque.
  1965.    *  @param  __y  A %deque of the same type as @a __x.
  1966.    *  @return  True iff @a x is lexicographically less than @a __y.
  1967.    *
  1968.    *  This is a total ordering relation.  It is linear in the size of the
  1969.    *  deques.  The elements must be comparable with @c <.
  1970.    *
  1971.    *  See std::lexicographical_compare() for how the determination is made.
  1972.   */
  1973.   template<typename _Tp, typename _Alloc>
  1974.     inline bool
  1975.     operator<(const deque<_Tp, _Alloc>& __x,
  1976.               const deque<_Tp, _Alloc>& __y)
  1977.     { return std::lexicographical_compare(__x.begin(), __x.end(),
  1978.                                           __y.begin(), __y.end()); }
  1979.  
  1980.   /// Based on operator==
  1981.   template<typename _Tp, typename _Alloc>
  1982.     inline bool
  1983.     operator!=(const deque<_Tp, _Alloc>& __x,
  1984.                const deque<_Tp, _Alloc>& __y)
  1985.     { return !(__x == __y); }
  1986.  
  1987.   /// Based on operator<
  1988.   template<typename _Tp, typename _Alloc>
  1989.     inline bool
  1990.     operator>(const deque<_Tp, _Alloc>& __x,
  1991.               const deque<_Tp, _Alloc>& __y)
  1992.     { return __y < __x; }
  1993.  
  1994.   /// Based on operator<
  1995.   template<typename _Tp, typename _Alloc>
  1996.     inline bool
  1997.     operator<=(const deque<_Tp, _Alloc>& __x,
  1998.                const deque<_Tp, _Alloc>& __y)
  1999.     { return !(__y < __x); }
  2000.  
  2001.   /// Based on operator<
  2002.   template<typename _Tp, typename _Alloc>
  2003.     inline bool
  2004.     operator>=(const deque<_Tp, _Alloc>& __x,
  2005.                const deque<_Tp, _Alloc>& __y)
  2006.     { return !(__x < __y); }
  2007.  
  2008.   /// See std::deque::swap().
  2009.   template<typename _Tp, typename _Alloc>
  2010.     inline void
  2011.     swap(deque<_Tp,_Alloc>& __x, deque<_Tp,_Alloc>& __y)
  2012.     { __x.swap(__y); }
  2013.  
  2014. #undef _GLIBCXX_DEQUE_BUF_SIZE
  2015.  
  2016. _GLIBCXX_END_NAMESPACE_CONTAINER
  2017. } // namespace std
  2018.  
  2019. #endif /* _STL_DEQUE_H */
  2020.