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stl_deque.h
// Deque implementation -*- C++ -*-

// Copyright (C) 2001-2014 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/>.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file bits/stl_deque.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{deque}
 */

#ifndef _STL_DEQUE_H
#define _STL_DEQUE_H 1

#include <bits/concept_check.h>
#include <bits/stl_iterator_base_types.h>
#include <bits/stl_iterator_base_funcs.h>
#if __cplusplus >= 201103L
#include <initializer_list>
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_CONTAINER

  /**
   *  @brief This function controls the size of memory nodes.
   *  @param  __size  The size of an element.
   *  @return   The number (not byte size) of elements per node.
   *
   *  This function started off as a compiler kludge from SGI, but
   *  seems to be a useful wrapper around a repeated constant
   *  expression.  The @b 512 is tunable (and no other code needs to
   *  change), but no investigation has been done since inheriting the
   *  SGI code.  Touch _GLIBCXX_DEQUE_BUF_SIZE only if you know what
   *  you are doing, however: changing it breaks the binary
   *  compatibility!!
  */

#ifndef _GLIBCXX_DEQUE_BUF_SIZE
#define _GLIBCXX_DEQUE_BUF_SIZE 512
#endif

  inline size_t
  __deque_buf_size(size_t __size)
  { return (__size < _GLIBCXX_DEQUE_BUF_SIZE
	    ? size_t(_GLIBCXX_DEQUE_BUF_SIZE / __size) : size_t(1)); }


  /**
   *  @brief A deque::iterator.
   *
   *  Quite a bit of intelligence here.  Much of the functionality of
   *  deque is actually passed off to this class.  A deque holds two
   *  of these internally, marking its valid range.  Access to
   *  elements is done as offsets of either of those two, relying on
   *  operator overloading in this class.
   *
   *  All the functions are op overloads except for _M_set_node.
  */
  template<typename _Tp, typename _Ref, typename _Ptr>
    struct _Deque_iterator
    {
      typedef _Deque_iterator<_Tp, _Tp&, _Tp*>             iterator;
      typedef _Deque_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;

      static size_t _S_buffer_size() _GLIBCXX_NOEXCEPT
      { return __deque_buf_size(sizeof(_Tp)); }

      typedef std::random_access_iterator_tag iterator_category;
      typedef _Tp                             value_type;
      typedef _Ptr                            pointer;
      typedef _Ref                            reference;
      typedef size_t                          size_type;
      typedef ptrdiff_t                       difference_type;
      typedef _Tp**                           _Map_pointer;
      typedef _Deque_iterator                 _Self;

      _Tp* _M_cur;
      _Tp* _M_first;
      _Tp* _M_last;
      _Map_pointer _M_node;

      _Deque_iterator(_Tp* __x, _Map_pointer __y) _GLIBCXX_NOEXCEPT
      : _M_cur(__x), _M_first(*__y),
        _M_last(*__y + _S_buffer_size()), _M_node(__y) { }

      _Deque_iterator() _GLIBCXX_NOEXCEPT
      : _M_cur(0), _M_first(0), _M_last(0), _M_node(0) { }

      _Deque_iterator(const iterator& __x) _GLIBCXX_NOEXCEPT
      : _M_cur(__x._M_cur), _M_first(__x._M_first),
        _M_last(__x._M_last), _M_node(__x._M_node) { }

      iterator
      _M_const_cast() const _GLIBCXX_NOEXCEPT
      { return iterator(_M_cur, _M_node); }

      reference
      operator*() const _GLIBCXX_NOEXCEPT
      { return *_M_cur; }

      pointer
      operator->() const _GLIBCXX_NOEXCEPT
      { return _M_cur; }

      _Self&
      operator++() _GLIBCXX_NOEXCEPT
      {
	++_M_cur;
	if (_M_cur == _M_last)
	  {
	    _M_set_node(_M_node + 1);
	    _M_cur = _M_first;
	  }
	return *this;
      }

      _Self
      operator++(int) _GLIBCXX_NOEXCEPT
      {
	_Self __tmp = *this;
	++*this;
	return __tmp;
      }

      _Self&
      operator--() _GLIBCXX_NOEXCEPT
      {
	if (_M_cur == _M_first)
	  {
	    _M_set_node(_M_node - 1);
	    _M_cur = _M_last;
	  }
	--_M_cur;
	return *this;
      }

      _Self
      operator--(int) _GLIBCXX_NOEXCEPT
      {
	_Self __tmp = *this;
	--*this;
	return __tmp;
      }

      _Self&
      operator+=(difference_type __n) _GLIBCXX_NOEXCEPT
      {
	const difference_type __offset = __n + (_M_cur - _M_first);
	if (__offset >= 0 && __offset < difference_type(_S_buffer_size()))
	  _M_cur += __n;
	else
	  {
	    const difference_type __node_offset =
	      __offset > 0 ? __offset / difference_type(_S_buffer_size())
	                   : -difference_type((-__offset - 1)
					      / _S_buffer_size()) - 1;
	    _M_set_node(_M_node + __node_offset);
	    _M_cur = _M_first + (__offset - __node_offset
				 * difference_type(_S_buffer_size()));
	  }
	return *this;
      }

      _Self
      operator+(difference_type __n) const _GLIBCXX_NOEXCEPT
      {
	_Self __tmp = *this;
	return __tmp += __n;
      }

      _Self&
      operator-=(difference_type __n) _GLIBCXX_NOEXCEPT
      { return *this += -__n; }

      _Self
      operator-(difference_type __n) const _GLIBCXX_NOEXCEPT
      {
	_Self __tmp = *this;
	return __tmp -= __n;
      }

      reference
      operator[](difference_type __n) const _GLIBCXX_NOEXCEPT
      { return *(*this + __n); }

      /** 
       *  Prepares to traverse new_node.  Sets everything except
       *  _M_cur, which should therefore be set by the caller
       *  immediately afterwards, based on _M_first and _M_last.
       */
      void
      _M_set_node(_Map_pointer __new_node) _GLIBCXX_NOEXCEPT
      {
	_M_node = __new_node;
	_M_first = *__new_node;
	_M_last = _M_first + difference_type(_S_buffer_size());
      }
    };

  // Note: we also provide overloads whose operands are of the same type in
  // order to avoid ambiguous overload resolution when std::rel_ops operators
  // are in scope (for additional details, see libstdc++/3628)
  template<typename _Tp, typename _Ref, typename _Ptr>
    inline bool
    operator==(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y) _GLIBCXX_NOEXCEPT
    { return __x._M_cur == __y._M_cur; }

  template<typename _Tp, typename _RefL, typename _PtrL,
	   typename _RefR, typename _PtrR>
    inline bool
    operator==(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y) _GLIBCXX_NOEXCEPT
    { return __x._M_cur == __y._M_cur; }

  template<typename _Tp, typename _Ref, typename _Ptr>
    inline bool
    operator!=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y) _GLIBCXX_NOEXCEPT
    { return !(__x == __y); }

  template<typename _Tp, typename _RefL, typename _PtrL,
	   typename _RefR, typename _PtrR>
    inline bool
    operator!=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y) _GLIBCXX_NOEXCEPT
    { return !(__x == __y); }

  template<typename _Tp, typename _Ref, typename _Ptr>
    inline bool
    operator<(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
	      const _Deque_iterator<_Tp, _Ref, _Ptr>& __y) _GLIBCXX_NOEXCEPT
    { return (__x._M_node == __y._M_node) ? (__x._M_cur < __y._M_cur)
                                          : (__x._M_node < __y._M_node); }

  template<typename _Tp, typename _RefL, typename _PtrL,
	   typename _RefR, typename _PtrR>
    inline bool
    operator<(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
	      const _Deque_iterator<_Tp, _RefR, _PtrR>& __y) _GLIBCXX_NOEXCEPT
    { return (__x._M_node == __y._M_node) ? (__x._M_cur < __y._M_cur)
	                                  : (__x._M_node < __y._M_node); }

  template<typename _Tp, typename _Ref, typename _Ptr>
    inline bool
    operator>(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
	      const _Deque_iterator<_Tp, _Ref, _Ptr>& __y) _GLIBCXX_NOEXCEPT
    { return __y < __x; }

  template<typename _Tp, typename _RefL, typename _PtrL,
	   typename _RefR, typename _PtrR>
    inline bool
    operator>(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
	      const _Deque_iterator<_Tp, _RefR, _PtrR>& __y) _GLIBCXX_NOEXCEPT
    { return __y < __x; }

  template<typename _Tp, typename _Ref, typename _Ptr>
    inline bool
    operator<=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y) _GLIBCXX_NOEXCEPT
    { return !(__y < __x); }

  template<typename _Tp, typename _RefL, typename _PtrL,
	   typename _RefR, typename _PtrR>
    inline bool
    operator<=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y) _GLIBCXX_NOEXCEPT
    { return !(__y < __x); }

  template<typename _Tp, typename _Ref, typename _Ptr>
    inline bool
    operator>=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y) _GLIBCXX_NOEXCEPT
    { return !(__x < __y); }

  template<typename _Tp, typename _RefL, typename _PtrL,
	   typename _RefR, typename _PtrR>
    inline bool
    operator>=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y) _GLIBCXX_NOEXCEPT
    { return !(__x < __y); }

  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // According to the resolution of DR179 not only the various comparison
  // operators but also operator- must accept mixed iterator/const_iterator
  // parameters.
  template<typename _Tp, typename _Ref, typename _Ptr>
    inline typename _Deque_iterator<_Tp, _Ref, _Ptr>::difference_type
    operator-(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
	      const _Deque_iterator<_Tp, _Ref, _Ptr>& __y) _GLIBCXX_NOEXCEPT
    {
      return typename _Deque_iterator<_Tp, _Ref, _Ptr>::difference_type
	(_Deque_iterator<_Tp, _Ref, _Ptr>::_S_buffer_size())
	* (__x._M_node - __y._M_node - 1) + (__x._M_cur - __x._M_first)
	+ (__y._M_last - __y._M_cur);
    }

  template<typename _Tp, typename _RefL, typename _PtrL,
	   typename _RefR, typename _PtrR>
    inline typename _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
    operator-(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
	      const _Deque_iterator<_Tp, _RefR, _PtrR>& __y) _GLIBCXX_NOEXCEPT
    {
      return typename _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
	(_Deque_iterator<_Tp, _RefL, _PtrL>::_S_buffer_size())
	* (__x._M_node - __y._M_node - 1) + (__x._M_cur - __x._M_first)
	+ (__y._M_last - __y._M_cur);
    }

  template<typename _Tp, typename _Ref, typename _Ptr>
    inline _Deque_iterator<_Tp, _Ref, _Ptr>
    operator+(ptrdiff_t __n, const _Deque_iterator<_Tp, _Ref, _Ptr>& __x)
    _GLIBCXX_NOEXCEPT
    { return __x + __n; }

  template<typename _Tp>
    void
    fill(const _Deque_iterator<_Tp, _Tp&, _Tp*>&,
	 const _Deque_iterator<_Tp, _Tp&, _Tp*>&, const _Tp&);

  template<typename _Tp>
    _Deque_iterator<_Tp, _Tp&, _Tp*>
    copy(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
	 _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
	 _Deque_iterator<_Tp, _Tp&, _Tp*>);

  template<typename _Tp>
    inline _Deque_iterator<_Tp, _Tp&, _Tp*>
    copy(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
	 _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
	 _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
    { return std::copy(_Deque_iterator<_Tp, const _Tp&, const _Tp*>(__first),
		       _Deque_iterator<_Tp, const _Tp&, const _Tp*>(__last),
		       __result); }

  template<typename _Tp>
    _Deque_iterator<_Tp, _Tp&, _Tp*>
    copy_backward(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
		  _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
		  _Deque_iterator<_Tp, _Tp&, _Tp*>);

  template<typename _Tp>
    inline _Deque_iterator<_Tp, _Tp&, _Tp*>
    copy_backward(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
		  _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
		  _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
    { return std::copy_backward(_Deque_iterator<_Tp,
				const _Tp&, const _Tp*>(__first),
				_Deque_iterator<_Tp,
				const _Tp&, const _Tp*>(__last),
				__result); }

#if __cplusplus >= 201103L
  template<typename _Tp>
    _Deque_iterator<_Tp, _Tp&, _Tp*>
    move(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
	 _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
	 _Deque_iterator<_Tp, _Tp&, _Tp*>);

  template<typename _Tp>
    inline _Deque_iterator<_Tp, _Tp&, _Tp*>
    move(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
	 _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
	 _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
    { return std::move(_Deque_iterator<_Tp, const _Tp&, const _Tp*>(__first),
		       _Deque_iterator<_Tp, const _Tp&, const _Tp*>(__last),
		       __result); }

  template<typename _Tp>
    _Deque_iterator<_Tp, _Tp&, _Tp*>
    move_backward(_Deque_iterator<_Tp, const _Tp&, const _Tp*>,
		  _Deque_iterator<_Tp, const _Tp&, const _Tp*>,
		  _Deque_iterator<_Tp, _Tp&, _Tp*>);

  template<typename _Tp>
    inline _Deque_iterator<_Tp, _Tp&, _Tp*>
    move_backward(_Deque_iterator<_Tp, _Tp&, _Tp*> __first,
		  _Deque_iterator<_Tp, _Tp&, _Tp*> __last,
		  _Deque_iterator<_Tp, _Tp&, _Tp*> __result)
    { return std::move_backward(_Deque_iterator<_Tp,
				const _Tp&, const _Tp*>(__first),
				_Deque_iterator<_Tp,
				const _Tp&, const _Tp*>(__last),
				__result); }
#endif

  /**
   *  Deque base class.  This class provides the unified face for %deque's
   *  allocation.  This class's constructor and destructor allocate and
   *  deallocate (but do not initialize) storage.  This makes %exception
   *  safety easier.
   *
   *  Nothing in this class ever constructs or destroys an actual Tp element.
   *  (Deque handles that itself.)  Only/All memory management is performed
   *  here.
  */
  template<typename _Tp, typename _Alloc>
    class _Deque_base
    {
    public:
      typedef _Alloc                  allocator_type;

      allocator_type
      get_allocator() const _GLIBCXX_NOEXCEPT
      { return allocator_type(_M_get_Tp_allocator()); }

      typedef _Deque_iterator<_Tp, _Tp&, _Tp*>             iterator;
      typedef _Deque_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;

      _Deque_base()
      : _M_impl()
      { _M_initialize_map(0); }

      _Deque_base(size_t __num_elements)
      : _M_impl()
      { _M_initialize_map(__num_elements); }

      _Deque_base(const allocator_type& __a, size_t __num_elements)
      : _M_impl(__a)
      { _M_initialize_map(__num_elements); }

      _Deque_base(const allocator_type& __a)
      : _M_impl(__a)
      { }

#if __cplusplus >= 201103L
      _Deque_base(_Deque_base&& __x)
      : _M_impl(std::move(__x._M_get_Tp_allocator()))
      {
	_M_initialize_map(0);
	if (__x._M_impl._M_map)
	  {
	    std::swap(this->_M_impl._M_start, __x._M_impl._M_start);
	    std::swap(this->_M_impl._M_finish, __x._M_impl._M_finish);
	    std::swap(this->_M_impl._M_map, __x._M_impl._M_map);
	    std::swap(this->_M_impl._M_map_size, __x._M_impl._M_map_size);
	  }
      }
#endif

      ~_Deque_base() _GLIBCXX_NOEXCEPT;

    protected:
      typedef typename _Alloc::template rebind<_Tp*>::other _Map_alloc_type;

      typedef typename _Alloc::template rebind<_Tp>::other  _Tp_alloc_type;

      //This struct encapsulates the implementation of the std::deque
      //standard container and at the same time makes use of the EBO
      //for empty allocators.
      struct _Deque_impl
      : public _Tp_alloc_type
      {
	_Tp** _M_map;
	size_t _M_map_size;
	iterator _M_start;
	iterator _M_finish;

	_Deque_impl()
	: _Tp_alloc_type(), _M_map(0), _M_map_size(0),
	  _M_start(), _M_finish()
	{ }

	_Deque_impl(const _Tp_alloc_type& __a) _GLIBCXX_NOEXCEPT
	: _Tp_alloc_type(__a), _M_map(0), _M_map_size(0),
	  _M_start(), _M_finish()
	{ }

#if __cplusplus >= 201103L
	_Deque_impl(_Tp_alloc_type&& __a) _GLIBCXX_NOEXCEPT
	: _Tp_alloc_type(std::move(__a)), _M_map(0), _M_map_size(0),
	  _M_start(), _M_finish()
	{ }
#endif
      };

      _Tp_alloc_type&
      _M_get_Tp_allocator() _GLIBCXX_NOEXCEPT
      { return *static_cast<_Tp_alloc_type*>(&this->_M_impl); }

      const _Tp_alloc_type&
      _M_get_Tp_allocator() const _GLIBCXX_NOEXCEPT
      { return *static_cast<const _Tp_alloc_type*>(&this->_M_impl); }

      _Map_alloc_type
      _M_get_map_allocator() const _GLIBCXX_NOEXCEPT
      { return _Map_alloc_type(_M_get_Tp_allocator()); }

      _Tp*
      _M_allocate_node()
      { 
	return _M_impl._Tp_alloc_type::allocate(__deque_buf_size(sizeof(_Tp)));
      }

      void
      _M_deallocate_node(_Tp* __p) _GLIBCXX_NOEXCEPT
      {
	_M_impl._Tp_alloc_type::deallocate(__p, __deque_buf_size(sizeof(_Tp)));
      }

      _Tp**
      _M_allocate_map(size_t __n)
      { return _M_get_map_allocator().allocate(__n); }

      void
      _M_deallocate_map(_Tp** __p, size_t __n) _GLIBCXX_NOEXCEPT
      { _M_get_map_allocator().deallocate(__p, __n); }

    protected:
      void _M_initialize_map(size_t);
      void _M_create_nodes(_Tp** __nstart, _Tp** __nfinish);
      void _M_destroy_nodes(_Tp** __nstart, _Tp** __nfinish) _GLIBCXX_NOEXCEPT;
      enum { _S_initial_map_size = 8 };

      _Deque_impl _M_impl;
    };

  template<typename _Tp, typename _Alloc>
    _Deque_base<_Tp, _Alloc>::
    ~_Deque_base() _GLIBCXX_NOEXCEPT
    {
      if (this->_M_impl._M_map)
	{
	  _M_destroy_nodes(this->_M_impl._M_start._M_node,
			   this->_M_impl._M_finish._M_node + 1);
	  _M_deallocate_map(this->_M_impl._M_map, this->_M_impl._M_map_size);
	}
    }

  /**
   *  @brief Layout storage.
   *  @param  __num_elements  The count of T's for which to allocate space
   *                        at first.
   *  @return   Nothing.
   *
   *  The initial underlying memory layout is a bit complicated...
  */
  template<typename _Tp, typename _Alloc>
    void
    _Deque_base<_Tp, _Alloc>::
    _M_initialize_map(size_t __num_elements)
    {
      const size_t __num_nodes = (__num_elements/ __deque_buf_size(sizeof(_Tp))
				  + 1);

      this->_M_impl._M_map_size = std::max((size_t) _S_initial_map_size,
					   size_t(__num_nodes + 2));
      this->_M_impl._M_map = _M_allocate_map(this->_M_impl._M_map_size);

      // For "small" maps (needing less than _M_map_size nodes), allocation
      // starts in the middle elements and grows outwards.  So nstart may be
      // the beginning of _M_map, but for small maps it may be as far in as
      // _M_map+3.

      _Tp** __nstart = (this->_M_impl._M_map
			+ (this->_M_impl._M_map_size - __num_nodes) / 2);
      _Tp** __nfinish = __nstart + __num_nodes;

      __try
	{ _M_create_nodes(__nstart, __nfinish); }
      __catch(...)
	{
	  _M_deallocate_map(this->_M_impl._M_map, this->_M_impl._M_map_size);
	  this->_M_impl._M_map = 0;
	  this->_M_impl._M_map_size = 0;
	  __throw_exception_again;
	}

      this->_M_impl._M_start._M_set_node(__nstart);
      this->_M_impl._M_finish._M_set_node(__nfinish - 1);
      this->_M_impl._M_start._M_cur = _M_impl._M_start._M_first;
      this->_M_impl._M_finish._M_cur = (this->_M_impl._M_finish._M_first
					+ __num_elements
					% __deque_buf_size(sizeof(_Tp)));
    }

  template<typename _Tp, typename _Alloc>
    void
    _Deque_base<_Tp, _Alloc>::
    _M_create_nodes(_Tp** __nstart, _Tp** __nfinish)
    {
      _Tp** __cur;
      __try
	{
	  for (__cur = __nstart; __cur < __nfinish; ++__cur)
	    *__cur = this->_M_allocate_node();
	}
      __catch(...)
	{
	  _M_destroy_nodes(__nstart, __cur);
	  __throw_exception_again;
	}
    }

  template<typename _Tp, typename _Alloc>
    void
    _Deque_base<_Tp, _Alloc>::
    _M_destroy_nodes(_Tp** __nstart, _Tp** __nfinish) _GLIBCXX_NOEXCEPT
    {
      for (_Tp** __n = __nstart; __n < __nfinish; ++__n)
	_M_deallocate_node(*__n);
    }

  /**
   *  @brief  A standard container using fixed-size memory allocation and
   *  constant-time manipulation of elements at either end.
   *
   *  @ingroup sequences
   *
   *  @tparam _Tp  Type of element.
   *  @tparam _Alloc  Allocator type, defaults to allocator<_Tp>.
   *
   *  Meets the requirements of a <a href="tables.html#65">container</a>, a
   *  <a href="tables.html#66">reversible container</a>, and a
   *  <a href="tables.html#67">sequence</a>, including the
   *  <a href="tables.html#68">optional sequence requirements</a>.
   *
   *  In previous HP/SGI versions of deque, there was an extra template
   *  parameter so users could control the node size.  This extension turned
   *  out to violate the C++ standard (it can be detected using template
   *  template parameters), and it was removed.
   *
   *  Here's how a deque<Tp> manages memory.  Each deque has 4 members:
   *
   *  - Tp**        _M_map
   *  - size_t      _M_map_size
   *  - iterator    _M_start, _M_finish
   *
   *  map_size is at least 8.  %map is an array of map_size
   *  pointers-to-@a nodes.  (The name %map has nothing to do with the
   *  std::map class, and @b nodes should not be confused with
   *  std::list's usage of @a node.)
   *
   *  A @a node has no specific type name as such, but it is referred
   *  to as @a node in this file.  It is a simple array-of-Tp.  If Tp
   *  is very large, there will be one Tp element per node (i.e., an
   *  @a array of one).  For non-huge Tp's, node size is inversely
   *  related to Tp size: the larger the Tp, the fewer Tp's will fit
   *  in a node.  The goal here is to keep the total size of a node
   *  relatively small and constant over different Tp's, to improve
   *  allocator efficiency.
   *
   *  Not every pointer in the %map array will point to a node.  If
   *  the initial number of elements in the deque is small, the
   *  /middle/ %map pointers will be valid, and the ones at the edges
   *  will be unused.  This same situation will arise as the %map
   *  grows: available %map pointers, if any, will be on the ends.  As
   *  new nodes are created, only a subset of the %map's pointers need
   *  to be copied @a outward.
   *
   *  Class invariants:
   * - For any nonsingular iterator i:
   *    - i.node points to a member of the %map array.  (Yes, you read that
   *      correctly:  i.node does not actually point to a node.)  The member of
   *      the %map array is what actually points to the node.
   *    - i.first == *(i.node)    (This points to the node (first Tp element).)
   *    - i.last  == i.first + node_size
   *    - i.cur is a pointer in the range [i.first, i.last).  NOTE:
   *      the implication of this is that i.cur is always a dereferenceable
   *      pointer, even if i is a past-the-end iterator.
   * - Start and Finish are always nonsingular iterators.  NOTE: this
   * means that an empty deque must have one node, a deque with <N
   * elements (where N is the node buffer size) must have one node, a
   * deque with N through (2N-1) elements must have two nodes, etc.
   * - For every node other than start.node and finish.node, every
   * element in the node is an initialized object.  If start.node ==
   * finish.node, then [start.cur, finish.cur) are initialized
   * objects, and the elements outside that range are uninitialized
   * storage.  Otherwise, [start.cur, start.last) and [finish.first,
   * finish.cur) are initialized objects, and [start.first, start.cur)
   * and [finish.cur, finish.last) are uninitialized storage.
   * - [%map, %map + map_size) is a valid, non-empty range.
   * - [start.node, finish.node] is a valid range contained within
   *   [%map, %map + map_size).
   * - A pointer in the range [%map, %map + map_size) points to an allocated
   *   node if and only if the pointer is in the range
   *   [start.node, finish.node].
   *
   *  Here's the magic:  nothing in deque is @b aware of the discontiguous
   *  storage!
   *
   *  The memory setup and layout occurs in the parent, _Base, and the iterator
   *  class is entirely responsible for @a leaping from one node to the next.
   *  All the implementation routines for deque itself work only through the
   *  start and finish iterators.  This keeps the routines simple and sane,
   *  and we can use other standard algorithms as well.
  */
  template<typename _Tp, typename _Alloc = std::allocator<_Tp> >
    class deque : protected _Deque_base<_Tp, _Alloc>
    {
      // concept requirements
      typedef typename _Alloc::value_type        _Alloc_value_type;
      __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
      __glibcxx_class_requires2(_Tp, _Alloc_value_type, _SameTypeConcept)

      typedef _Deque_base<_Tp, _Alloc>           _Base;
      typedef typename _Base::_Tp_alloc_type	 _Tp_alloc_type;

    public:
      typedef _Tp                                        value_type;
      typedef typename _Tp_alloc_type::pointer           pointer;
      typedef typename _Tp_alloc_type::const_pointer     const_pointer;
      typedef typename _Tp_alloc_type::reference         reference;
      typedef typename _Tp_alloc_type::const_reference   const_reference;
      typedef typename _Base::iterator                   iterator;
      typedef typename _Base::const_iterator             const_iterator;
      typedef std::reverse_iterator<const_iterator>      const_reverse_iterator;
      typedef std::reverse_iterator<iterator>            reverse_iterator;
      typedef size_t                             size_type;
      typedef ptrdiff_t                          difference_type;
      typedef _Alloc                             allocator_type;

    protected:
      typedef pointer*                           _Map_pointer;

      static size_t _S_buffer_size() _GLIBCXX_NOEXCEPT
      { return __deque_buf_size(sizeof(_Tp)); }

      // Functions controlling memory layout, and nothing else.
      using _Base::_M_initialize_map;
      using _Base::_M_create_nodes;
      using _Base::_M_destroy_nodes;
      using _Base::_M_allocate_node;
      using _Base::_M_deallocate_node;
      using _Base::_M_allocate_map;
      using _Base::_M_deallocate_map;
      using _Base::_M_get_Tp_allocator;

      /** 
       *  A total of four data members accumulated down the hierarchy.
       *  May be accessed via _M_impl.*
       */
      using _Base::_M_impl;

    public:
      // [23.2.1.1] construct/copy/destroy
      // (assign() and get_allocator() are also listed in this section)

      /**
       *  @brief  Creates a %deque with no elements.
       */
      deque() : _Base() { }

      /**
       *  @brief  Creates a %deque with no elements.
       *  @param  __a  An allocator object.
       */
      explicit
      deque(const allocator_type& __a)
      : _Base(__a, 0) { }

#if __cplusplus >= 201103L
      /**
       *  @brief  Creates a %deque with default constructed elements.
       *  @param  __n  The number of elements to initially create.
       *
       *  This constructor fills the %deque with @a n default
       *  constructed elements.
       */
      explicit
      deque(size_type __n)
      : _Base(__n)
      { _M_default_initialize(); }

      /**
       *  @brief  Creates a %deque with copies of an exemplar element.
       *  @param  __n  The number of elements to initially create.
       *  @param  __value  An element to copy.
       *  @param  __a  An allocator.
       *
       *  This constructor fills the %deque with @a __n copies of @a __value.
       */
      deque(size_type __n, const value_type& __value,
	    const allocator_type& __a = allocator_type())
      : _Base(__a, __n)
      { _M_fill_initialize(__value); }
#else
      /**
       *  @brief  Creates a %deque with copies of an exemplar element.
       *  @param  __n  The number of elements to initially create.
       *  @param  __value  An element to copy.
       *  @param  __a  An allocator.
       *
       *  This constructor fills the %deque with @a __n copies of @a __value.
       */
      explicit
      deque(size_type __n, const value_type& __value = value_type(),
	    const allocator_type& __a = allocator_type())
      : _Base(__a, __n)
      { _M_fill_initialize(__value); }
#endif

      /**
       *  @brief  %Deque copy constructor.
       *  @param  __x  A %deque of identical element and allocator types.
       *
       *  The newly-created %deque uses a copy of the allocation object used
       *  by @a __x.
       */
      deque(const deque& __x)
      : _Base(__x._M_get_Tp_allocator(), __x.size())
      { std::__uninitialized_copy_a(__x.begin(), __x.end(), 
				    this->_M_impl._M_start,
				    _M_get_Tp_allocator()); }

#if __cplusplus >= 201103L
      /**
       *  @brief  %Deque move constructor.
       *  @param  __x  A %deque of identical element and allocator types.
       *
       *  The newly-created %deque contains the exact contents of @a __x.
       *  The contents of @a __x are a valid, but unspecified %deque.
       */
      deque(deque&& __x)
      : _Base(std::move(__x)) { }

      /**
       *  @brief  Builds a %deque from an initializer list.
       *  @param  __l  An initializer_list.
       *  @param  __a  An allocator object.
       *
       *  Create a %deque consisting of copies of the elements in the
       *  initializer_list @a __l.
       *
       *  This will call the element type's copy constructor N times
       *  (where N is __l.size()) and do no memory reallocation.
       */
      deque(initializer_list<value_type> __l,
	    const allocator_type& __a = allocator_type())
      : _Base(__a)
      {
	_M_range_initialize(__l.begin(), __l.end(),
			    random_access_iterator_tag());
      }
#endif

      /**
       *  @brief  Builds a %deque from a range.
       *  @param  __first  An input iterator.
       *  @param  __last  An input iterator.
       *  @param  __a  An allocator object.
       *
       *  Create a %deque consisting of copies of the elements from [__first,
       *  __last).
       *
       *  If the iterators are forward, bidirectional, or random-access, then
       *  this will call the elements' copy constructor N times (where N is
       *  distance(__first,__last)) and do no memory reallocation.  But if only
       *  input iterators are used, then this will do at most 2N calls to the
       *  copy constructor, and logN memory reallocations.
       */
#if __cplusplus >= 201103L
      template<typename _InputIterator,
	       typename = std::_RequireInputIter<_InputIterator>>
        deque(_InputIterator __first, _InputIterator __last,
	      const allocator_type& __a = allocator_type())
	: _Base(__a)
        { _M_initialize_dispatch(__first, __last, __false_type()); }
#else
      template<typename _InputIterator>
        deque(_InputIterator __first, _InputIterator __last,
	      const allocator_type& __a = allocator_type())
	: _Base(__a)
        {
	  // Check whether it's an integral type.  If so, it's not an iterator.
	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
	  _M_initialize_dispatch(__first, __last, _Integral());
	}
#endif

      /**
       *  The dtor only erases the elements, and note that if the elements
       *  themselves are pointers, the pointed-to memory is not touched in any
       *  way.  Managing the pointer is the user's responsibility.
       */
      ~deque() _GLIBCXX_NOEXCEPT
      { _M_destroy_data(begin(), end(), _M_get_Tp_allocator()); }

      /**
       *  @brief  %Deque assignment operator.
       *  @param  __x  A %deque of identical element and allocator types.
       *
       *  All the elements of @a x are copied, but unlike the copy constructor,
       *  the allocator object is not copied.
       */
      deque&
      operator=(const deque& __x);

#if __cplusplus >= 201103L
      /**
       *  @brief  %Deque move assignment operator.
       *  @param  __x  A %deque of identical element and allocator types.
       *
       *  The contents of @a __x are moved into this deque (without copying).
       *  @a __x is a valid, but unspecified %deque.
       */
      deque&
      operator=(deque&& __x) noexcept
      {
	// NB: DR 1204.
	// NB: DR 675.
	this->clear();
	this->swap(__x);
	return *this;
      }

      /**
       *  @brief  Assigns an initializer list to a %deque.
       *  @param  __l  An initializer_list.
       *
       *  This function fills a %deque with copies of the elements in the
       *  initializer_list @a __l.
       *
       *  Note that the assignment completely changes the %deque and that the
       *  resulting %deque's size is the same as the number of elements
       *  assigned.  Old data may be lost.
       */
      deque&
      operator=(initializer_list<value_type> __l)
      {
	this->assign(__l.begin(), __l.end());
	return *this;
      }
#endif

      /**
       *  @brief  Assigns a given value to a %deque.
       *  @param  __n  Number of elements to be assigned.
       *  @param  __val  Value to be assigned.
       *
       *  This function fills a %deque with @a n copies of the given
       *  value.  Note that the assignment completely changes the
       *  %deque and that the resulting %deque's size is the same as
       *  the number of elements assigned.  Old data may be lost.
       */
      void
      assign(size_type __n, const value_type& __val)
      { _M_fill_assign(__n, __val); }

      /**
       *  @brief  Assigns a range to a %deque.
       *  @param  __first  An input iterator.
       *  @param  __last   An input iterator.
       *
       *  This function fills a %deque with copies of the elements in the
       *  range [__first,__last).
       *
       *  Note that the assignment completely changes the %deque and that the
       *  resulting %deque's size is the same as the number of elements
       *  assigned.  Old data may be lost.
       */
#if __cplusplus >= 201103L
      template<typename _InputIterator,
	       typename = std::_RequireInputIter<_InputIterator>>
        void
        assign(_InputIterator __first, _InputIterator __last)
        { _M_assign_dispatch(__first, __last, __false_type()); }
#else
      template<typename _InputIterator>
        void
        assign(_InputIterator __first, _InputIterator __last)
        {
	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
	  _M_assign_dispatch(__first, __last, _Integral());
	}
#endif

#if __cplusplus >= 201103L
      /**
       *  @brief  Assigns an initializer list to a %deque.
       *  @param  __l  An initializer_list.
       *
       *  This function fills a %deque with copies of the elements in the
       *  initializer_list @a __l.
       *
       *  Note that the assignment completely changes the %deque and that the
       *  resulting %deque's size is the same as the number of elements
       *  assigned.  Old data may be lost.
       */
      void
      assign(initializer_list<value_type> __l)
      { this->assign(__l.begin(), __l.end()); }
#endif

      /// Get a copy of the memory allocation object.
      allocator_type
      get_allocator() const _GLIBCXX_NOEXCEPT
      { return _Base::get_allocator(); }

      // iterators
      /**
       *  Returns a read/write iterator that points to the first element in the
       *  %deque.  Iteration is done in ordinary element order.
       */
      iterator
      begin() _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_start; }

      /**
       *  Returns a read-only (constant) iterator that points to the first
       *  element in the %deque.  Iteration is done in ordinary element order.
       */
      const_iterator
      begin() const _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_start; }

      /**
       *  Returns a read/write iterator that points one past the last
       *  element in the %deque.  Iteration is done in ordinary
       *  element order.
       */
      iterator
      end() _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_finish; }

      /**
       *  Returns a read-only (constant) iterator that points one past
       *  the last element in the %deque.  Iteration is done in
       *  ordinary element order.
       */
      const_iterator
      end() const _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_finish; }

      /**
       *  Returns a read/write reverse iterator that points to the
       *  last element in the %deque.  Iteration is done in reverse
       *  element order.
       */
      reverse_iterator
      rbegin() _GLIBCXX_NOEXCEPT
      { return reverse_iterator(this->_M_impl._M_finish); }

      /**
       *  Returns a read-only (constant) reverse iterator that points
       *  to the last element in the %deque.  Iteration is done in
       *  reverse element order.
       */
      const_reverse_iterator
      rbegin() const _GLIBCXX_NOEXCEPT
      { return const_reverse_iterator(this->_M_impl._M_finish); }

      /**
       *  Returns a read/write reverse iterator that points to one
       *  before the first element in the %deque.  Iteration is done
       *  in reverse element order.
       */
      reverse_iterator
      rend() _GLIBCXX_NOEXCEPT
      { return reverse_iterator(this->_M_impl._M_start); }

      /**
       *  Returns a read-only (constant) reverse iterator that points
       *  to one before the first element in the %deque.  Iteration is
       *  done in reverse element order.
       */
      const_reverse_iterator
      rend() const _GLIBCXX_NOEXCEPT
      { return const_reverse_iterator(this->_M_impl._M_start); }

#if __cplusplus >= 201103L
      /**
       *  Returns a read-only (constant) iterator that points to the first
       *  element in the %deque.  Iteration is done in ordinary element order.
       */
      const_iterator
      cbegin() const noexcept
      { return this->_M_impl._M_start; }

      /**
       *  Returns a read-only (constant) iterator that points one past
       *  the last element in the %deque.  Iteration is done in
       *  ordinary element order.
       */
      const_iterator
      cend() const noexcept
      { return this->_M_impl._M_finish; }

      /**
       *  Returns a read-only (constant) reverse iterator that points
       *  to the last element in the %deque.  Iteration is done in
       *  reverse element order.
       */
      const_reverse_iterator
      crbegin() const noexcept
      { return const_reverse_iterator(this->_M_impl._M_finish); }

      /**
       *  Returns a read-only (constant) reverse iterator that points
       *  to one before the first element in the %deque.  Iteration is
       *  done in reverse element order.
       */
      const_reverse_iterator
      crend() const noexcept
      { return const_reverse_iterator(this->_M_impl._M_start); }
#endif

      // [23.2.1.2] capacity
      /**  Returns the number of elements in the %deque.  */
      size_type
      size() const _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_finish - this->_M_impl._M_start; }

      /**  Returns the size() of the largest possible %deque.  */
      size_type
      max_size() const _GLIBCXX_NOEXCEPT
      { return _M_get_Tp_allocator().max_size(); }

#if __cplusplus >= 201103L
      /**
       *  @brief  Resizes the %deque to the specified number of elements.
       *  @param  __new_size  Number of elements the %deque should contain.
       *
       *  This function will %resize the %deque to the specified
       *  number of elements.  If the number is smaller than the
       *  %deque's current size the %deque is truncated, otherwise
       *  default constructed elements are appended.
       */
      void
      resize(size_type __new_size)
      {
	const size_type __len = size();
	if (__new_size > __len)
	  _M_default_append(__new_size - __len);
	else if (__new_size < __len)
	  _M_erase_at_end(this->_M_impl._M_start
			  + difference_type(__new_size));
      }

      /**
       *  @brief  Resizes the %deque to the specified number of elements.
       *  @param  __new_size  Number of elements the %deque should contain.
       *  @param  __x  Data with which new elements should be populated.
       *
       *  This function will %resize the %deque to the specified
       *  number of elements.  If the number is smaller than the
       *  %deque's current size the %deque is truncated, otherwise the
       *  %deque is extended and new elements are populated with given
       *  data.
       */
      void
      resize(size_type __new_size, const value_type& __x)
      {
	const size_type __len = size();
	if (__new_size > __len)
	  insert(this->_M_impl._M_finish, __new_size - __len, __x);
	else if (__new_size < __len)
	  _M_erase_at_end(this->_M_impl._M_start
			  + difference_type(__new_size));
      }
#else
      /**
       *  @brief  Resizes the %deque to the specified number of elements.
       *  @param  __new_size  Number of elements the %deque should contain.
       *  @param  __x  Data with which new elements should be populated.
       *
       *  This function will %resize the %deque to the specified
       *  number of elements.  If the number is smaller than the
       *  %deque's current size the %deque is truncated, otherwise the
       *  %deque is extended and new elements are populated with given
       *  data.
       */
      void
      resize(size_type __new_size, value_type __x = value_type())
      {
	const size_type __len = size();
	if (__new_size > __len)
	  insert(this->_M_impl._M_finish, __new_size - __len, __x);
	else if (__new_size < __len)
	  _M_erase_at_end(this->_M_impl._M_start
			  + difference_type(__new_size));
      }
#endif

#if __cplusplus >= 201103L
      /**  A non-binding request to reduce memory use.  */
      void
      shrink_to_fit() noexcept
      { _M_shrink_to_fit(); }
#endif

      /**
       *  Returns true if the %deque is empty.  (Thus begin() would
       *  equal end().)
       */
      bool
      empty() const _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_finish == this->_M_impl._M_start; }

      // element access
      /**
       *  @brief Subscript access to the data contained in the %deque.
       *  @param __n The index of the element for which data should be
       *  accessed.
       *  @return  Read/write reference to data.
       *
       *  This operator allows for easy, array-style, data access.
       *  Note that data access with this operator is unchecked and
       *  out_of_range lookups are not defined. (For checked lookups
       *  see at().)
       */
      reference
      operator[](size_type __n) _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_start[difference_type(__n)]; }

      /**
       *  @brief Subscript access to the data contained in the %deque.
       *  @param __n The index of the element for which data should be
       *  accessed.
       *  @return  Read-only (constant) reference to data.
       *
       *  This operator allows for easy, array-style, data access.
       *  Note that data access with this operator is unchecked and
       *  out_of_range lookups are not defined. (For checked lookups
       *  see at().)
       */
      const_reference
      operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      { return this->_M_impl._M_start[difference_type(__n)]; }

    protected:
      /// Safety check used only from at().
      void
      _M_range_check(size_type __n) const
      {
	if (__n >= this->size())
	  __throw_out_of_range_fmt(__N("deque::_M_range_check: __n "
				       "(which is %zu)>= this->size() "
				       "(which is %zu)"),
				   __n, this->size());
      }

    public:
      /**
       *  @brief  Provides access to the data contained in the %deque.
       *  @param __n The index of the element for which data should be
       *  accessed.
       *  @return  Read/write reference to data.
       *  @throw  std::out_of_range  If @a __n is an invalid index.
       *
       *  This function provides for safer data access.  The parameter
       *  is first checked that it is in the range of the deque.  The
       *  function throws out_of_range if the check fails.
       */
      reference
      at(size_type __n)
      {
	_M_range_check(__n);
	return (*this)[__n];
      }

      /**
       *  @brief  Provides access to the data contained in the %deque.
       *  @param __n The index of the element for which data should be
       *  accessed.
       *  @return  Read-only (constant) reference to data.
       *  @throw  std::out_of_range  If @a __n is an invalid index.
       *
       *  This function provides for safer data access.  The parameter is first
       *  checked that it is in the range of the deque.  The function throws
       *  out_of_range if the check fails.
       */
      const_reference
      at(size_type __n) const
      {
	_M_range_check(__n);
	return (*this)[__n];
      }

      /**
       *  Returns a read/write reference to the data at the first
       *  element of the %deque.
       */
      reference
      front() _GLIBCXX_NOEXCEPT
      { return *begin(); }

      /**
       *  Returns a read-only (constant) reference to the data at the first
       *  element of the %deque.
       */
      const_reference
      front() const _GLIBCXX_NOEXCEPT
      { return *begin(); }

      /**
       *  Returns a read/write reference to the data at the last element of the
       *  %deque.
       */
      reference
      back() _GLIBCXX_NOEXCEPT
      {
	iterator __tmp = end();
	--__tmp;
	return *__tmp;
      }

      /**
       *  Returns a read-only (constant) reference to the data at the last
       *  element of the %deque.
       */
      const_reference
      back() const _GLIBCXX_NOEXCEPT
      {
	const_iterator __tmp = end();
	--__tmp;
	return *__tmp;
      }

      // [23.2.1.2] modifiers
      /**
       *  @brief  Add data to the front of the %deque.
       *  @param  __x  Data to be added.
       *
       *  This is a typical stack operation.  The function creates an
       *  element at the front of the %deque and assigns the given
       *  data to it.  Due to the nature of a %deque this operation
       *  can be done in constant time.
       */
      void
      push_front(const value_type& __x)
      {
	if (this->_M_impl._M_start._M_cur != this->_M_impl._M_start._M_first)
	  {
	    this->_M_impl.construct(this->_M_impl._M_start._M_cur - 1, __x);
	    --this->_M_impl._M_start._M_cur;
	  }
	else
	  _M_push_front_aux(__x);
      }

#if __cplusplus >= 201103L
      void
      push_front(value_type&& __x)
      { emplace_front(std::move(__x)); }

      template<typename... _Args>
        void
        emplace_front(_Args&&... __args);
#endif

      /**
       *  @brief  Add data to the end of the %deque.
       *  @param  __x  Data to be added.
       *
       *  This is a typical stack operation.  The function creates an
       *  element at the end of the %deque and assigns the given data
       *  to it.  Due to the nature of a %deque this operation can be
       *  done in constant time.
       */
      void
      push_back(const value_type& __x)
      {
	if (this->_M_impl._M_finish._M_cur
	    != this->_M_impl._M_finish._M_last - 1)
	  {
	    this->_M_impl.construct(this->_M_impl._M_finish._M_cur, __x);
	    ++this->_M_impl._M_finish._M_cur;
	  }
	else
	  _M_push_back_aux(__x);
      }

#if __cplusplus >= 201103L
      void
      push_back(value_type&& __x)
      { emplace_back(std::move(__x)); }

      template<typename... _Args>
        void
        emplace_back(_Args&&... __args);
#endif

      /**
       *  @brief  Removes first element.
       *
       *  This is a typical stack operation.  It shrinks the %deque by one.
       *
       *  Note that no data is returned, and if the first element's data is
       *  needed, it should be retrieved before pop_front() is called.
       */
      void
      pop_front() _GLIBCXX_NOEXCEPT
      {
	if (this->_M_impl._M_start._M_cur
	    != this->_M_impl._M_start._M_last - 1)
	  {
	    this->_M_impl.destroy(this->_M_impl._M_start._M_cur);
	    ++this->_M_impl._M_start._M_cur;
	  }
	else
	  _M_pop_front_aux();
      }

      /**
       *  @brief  Removes last element.
       *
       *  This is a typical stack operation.  It shrinks the %deque by one.
       *
       *  Note that no data is returned, and if the last element's data is
       *  needed, it should be retrieved before pop_back() is called.
       */
      void
      pop_back() _GLIBCXX_NOEXCEPT
      {
	if (this->_M_impl._M_finish._M_cur
	    != this->_M_impl._M_finish._M_first)
	  {
	    --this->_M_impl._M_finish._M_cur;
	    this->_M_impl.destroy(this->_M_impl._M_finish._M_cur);
	  }
	else
	  _M_pop_back_aux();
      }

#if __cplusplus >= 201103L
      /**
       *  @brief  Inserts an object in %deque before specified iterator.
       *  @param  __position  A const_iterator into the %deque.
       *  @param  __args  Arguments.
       *  @return  An iterator that points to the inserted data.
       *
       *  This function will insert an object of type T constructed
       *  with T(std::forward<Args>(args)...) before the specified location.
       */
      template<typename... _Args>
        iterator
        emplace(const_iterator __position, _Args&&... __args);

      /**
       *  @brief  Inserts given value into %deque before specified iterator.
       *  @param  __position  A const_iterator into the %deque.
       *  @param  __x  Data to be inserted.
       *  @return  An iterator that points to the inserted data.
       *
       *  This function will insert a copy of the given value before the
       *  specified location.
       */
      iterator
      insert(const_iterator __position, const value_type& __x);
#else
      /**
       *  @brief  Inserts given value into %deque before specified iterator.
       *  @param  __position  An iterator into the %deque.
       *  @param  __x  Data to be inserted.
       *  @return  An iterator that points to the inserted data.
       *
       *  This function will insert a copy of the given value before the
       *  specified location.
       */
      iterator
      insert(iterator __position, const value_type& __x);
#endif

#if __cplusplus >= 201103L
      /**
       *  @brief  Inserts given rvalue into %deque before specified iterator.
       *  @param  __position  A const_iterator into the %deque.
       *  @param  __x  Data to be inserted.
       *  @return  An iterator that points to the inserted data.
       *
       *  This function will insert a copy of the given rvalue before the
       *  specified location.
       */
      iterator
      insert(const_iterator __position, value_type&& __x)
      { return emplace(__position, std::move(__x)); }

      /**
       *  @brief  Inserts an initializer list into the %deque.
       *  @param  __p  An iterator into the %deque.
       *  @param  __l  An initializer_list.
       *
       *  This function will insert copies of the data in the
       *  initializer_list @a __l into the %deque before the location
       *  specified by @a __p.  This is known as <em>list insert</em>.
       */
      iterator
      insert(const_iterator __p, initializer_list<value_type> __l)
      { return this->insert(__p, __l.begin(), __l.end()); }
#endif

#if __cplusplus >= 201103L
      /**
       *  @brief  Inserts a number of copies of given data into the %deque.
       *  @param  __position  A const_iterator into the %deque.
       *  @param  __n  Number of elements to be inserted.
       *  @param  __x  Data to be inserted.
       *  @return  An iterator that points to the inserted data.
       *
       *  This function will insert a specified number of copies of the given
       *  data before the location specified by @a __position.
       */
      iterator
      insert(const_iterator __position, size_type __n, const value_type& __x)
      {
	difference_type __offset = __position - cbegin();
	_M_fill_insert(__position._M_const_cast(), __n, __x);
	return begin() + __offset;
      }
#else
      /**
       *  @brief  Inserts a number of copies of given data into the %deque.
       *  @param  __position  An iterator into the %deque.
       *  @param  __n  Number of elements to be inserted.
       *  @param  __x  Data to be inserted.
       *
       *  This function will insert a specified number of copies of the given
       *  data before the location specified by @a __position.
       */
      void
      insert(iterator __position, size_type __n, const value_type& __x)
      { _M_fill_insert(__position, __n, __x); }
#endif

#if __cplusplus >= 201103L
      /**
       *  @brief  Inserts a range into the %deque.
       *  @param  __position  A const_iterator into the %deque.
       *  @param  __first  An input iterator.
       *  @param  __last   An input iterator.
       *  @return  An iterator that points to the inserted data.
       *
       *  This function will insert copies of the data in the range
       *  [__first,__last) into the %deque before the location specified
       *  by @a __position.  This is known as <em>range insert</em>.
       */
      template<typename _InputIterator,
	       typename = std::_RequireInputIter<_InputIterator>>
        iterator
        insert(const_iterator __position, _InputIterator __first,
	       _InputIterator __last)
        {
	  difference_type __offset = __position - cbegin();
	  _M_insert_dispatch(__position._M_const_cast(),
			     __first, __last, __false_type());
	  return begin() + __offset;
	}
#else
      /**
       *  @brief  Inserts a range into the %deque.
       *  @param  __position  An iterator into the %deque.
       *  @param  __first  An input iterator.
       *  @param  __last   An input iterator.
       *
       *  This function will insert copies of the data in the range
       *  [__first,__last) into the %deque before the location specified
       *  by @a __position.  This is known as <em>range insert</em>.
       */
      template<typename _InputIterator>
        void
        insert(iterator __position, _InputIterator __first,
	       _InputIterator __last)
        {
	  // Check whether it's an integral type.  If so, it's not an iterator.
	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
	  _M_insert_dispatch(__position, __first, __last, _Integral());
	}
#endif

      /**
       *  @brief  Remove element at given position.
       *  @param  __position  Iterator pointing to element to be erased.
       *  @return  An iterator pointing to the next element (or end()).
       *
       *  This function will erase the element at the given position and thus
       *  shorten the %deque by one.
       *
       *  The user is cautioned that
       *  this function only erases the element, and that if the element is
       *  itself a pointer, the pointed-to memory is not touched in any way.
       *  Managing the pointer is the user's responsibility.
       */
      iterator
#if __cplusplus >= 201103L
      erase(const_iterator __position)
#else
      erase(iterator __position)
#endif
      { return _M_erase(__position._M_const_cast()); }

      /**
       *  @brief  Remove a range of elements.
       *  @param  __first  Iterator pointing to the first element to be erased.
       *  @param  __last  Iterator pointing to one past the last element to be
       *                erased.
       *  @return  An iterator pointing to the element pointed to by @a last
       *           prior to erasing (or end()).
       *
       *  This function will erase the elements in the range
       *  [__first,__last) and shorten the %deque accordingly.
       *
       *  The user is cautioned that
       *  this function only erases the elements, and that if the elements
       *  themselves are pointers, the pointed-to memory is not touched in any
       *  way.  Managing the pointer is the user's responsibility.
       */
      iterator
#if __cplusplus >= 201103L
      erase(const_iterator __first, const_iterator __last)
#else
      erase(iterator __first, iterator __last)
#endif
      { return _M_erase(__first._M_const_cast(), __last._M_const_cast()); }

      /**
       *  @brief  Swaps data with another %deque.
       *  @param  __x  A %deque of the same element and allocator types.
       *
       *  This exchanges the elements between two deques in constant time.
       *  (Four pointers, so it should be quite fast.)
       *  Note that the global std::swap() function is specialized such that
       *  std::swap(d1,d2) will feed to this function.
       */
      void
      swap(deque& __x) _GLIBCXX_NOEXCEPT
      {
	std::swap(this->_M_impl._M_start, __x._M_impl._M_start);
	std::swap(this->_M_impl._M_finish, __x._M_impl._M_finish);
	std::swap(this->_M_impl._M_map, __x._M_impl._M_map);
	std::swap(this->_M_impl._M_map_size, __x._M_impl._M_map_size);

	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// 431. Swapping containers with unequal allocators.
	std::__alloc_swap<_Tp_alloc_type>::_S_do_it(_M_get_Tp_allocator(),
						    __x._M_get_Tp_allocator());
      }

      /**
       *  Erases all the elements.  Note that this function only erases the
       *  elements, and that if the elements themselves are pointers, the
       *  pointed-to memory is not touched in any way.  Managing the pointer is
       *  the user's responsibility.
       */
      void
      clear() _GLIBCXX_NOEXCEPT
      { _M_erase_at_end(begin()); }

    protected:
      // Internal constructor functions follow.

      // called by the range constructor to implement [23.1.1]/9

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 438. Ambiguity in the "do the right thing" clause
      template<typename _Integer>
        void
        _M_initialize_dispatch(_Integer __n, _Integer __x, __true_type)
        {
	  _M_initialize_map(static_cast<size_type>(__n));
	  _M_fill_initialize(__x);
	}

      // called by the range constructor to implement [23.1.1]/9
      template<typename _InputIterator>
        void
        _M_initialize_dispatch(_InputIterator __first, _InputIterator __last,
			       __false_type)
        {
	  typedef typename std::iterator_traits<_InputIterator>::
	    iterator_category _IterCategory;
	  _M_range_initialize(__first, __last, _IterCategory());
	}

      // called by the second initialize_dispatch above
      //@{
      /**
       *  @brief Fills the deque with whatever is in [first,last).
       *  @param  __first  An input iterator.
       *  @param  __last  An input iterator.
       *  @return   Nothing.
       *
       *  If the iterators are actually forward iterators (or better), then the
       *  memory layout can be done all at once.  Else we move forward using
       *  push_back on each value from the iterator.
       */
      template<typename _InputIterator>
        void
        _M_range_initialize(_InputIterator __first, _InputIterator __last,
			    std::input_iterator_tag);

      // called by the second initialize_dispatch above
      template<typename _ForwardIterator>
        void
        _M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
			    std::forward_iterator_tag);
      //@}

      /**
       *  @brief Fills the %deque with copies of value.
       *  @param  __value  Initial value.
       *  @return   Nothing.
       *  @pre _M_start and _M_finish have already been initialized,
       *  but none of the %deque's elements have yet been constructed.
       *
       *  This function is called only when the user provides an explicit size
       *  (with or without an explicit exemplar value).
       */
      void
      _M_fill_initialize(const value_type& __value);

#if __cplusplus >= 201103L
      // called by deque(n).
      void
      _M_default_initialize();
#endif

      // Internal assign functions follow.  The *_aux functions do the actual
      // assignment work for the range versions.

      // called by the range assign to implement [23.1.1]/9

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 438. Ambiguity in the "do the right thing" clause
      template<typename _Integer>
        void
        _M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
        { _M_fill_assign(__n, __val); }

      // called by the range assign to implement [23.1.1]/9
      template<typename _InputIterator>
        void
        _M_assign_dispatch(_InputIterator __first, _InputIterator __last,
			   __false_type)
        {
	  typedef typename std::iterator_traits<_InputIterator>::
	    iterator_category _IterCategory;
	  _M_assign_aux(__first, __last, _IterCategory());
	}

      // called by the second assign_dispatch above
      template<typename _InputIterator>
        void
        _M_assign_aux(_InputIterator __first, _InputIterator __last,
		      std::input_iterator_tag);

      // called by the second assign_dispatch above
      template<typename _ForwardIterator>
        void
        _M_assign_aux(_ForwardIterator __first, _ForwardIterator __last,
		      std::forward_iterator_tag)
        {
	  const size_type __len = std::distance(__first, __last);
	  if (__len > size())
	    {
	      _ForwardIterator __mid = __first;
	      std::advance(__mid, size());
	      std::copy(__first, __mid, begin());
	      insert(end(), __mid, __last);
	    }
	  else
	    _M_erase_at_end(std::copy(__first, __last, begin()));
	}

      // Called by assign(n,t), and the range assign when it turns out
      // to be the same thing.
      void
      _M_fill_assign(size_type __n, const value_type& __val)
      {
	if (__n > size())
	  {
	    std::fill(begin(), end(), __val);
	    insert(end(), __n - size(), __val);
	  }
	else
	  {
	    _M_erase_at_end(begin() + difference_type(__n));
	    std::fill(begin(), end(), __val);
	  }
      }

      //@{
      /// Helper functions for push_* and pop_*.
#if __cplusplus < 201103L
      void _M_push_back_aux(const value_type&);

      void _M_push_front_aux(const value_type&);
#else
      template<typename... _Args>
        void _M_push_back_aux(_Args&&... __args);

      template<typename... _Args>
        void _M_push_front_aux(_Args&&... __args);
#endif

      void _M_pop_back_aux();

      void _M_pop_front_aux();
      //@}

      // Internal insert functions follow.  The *_aux functions do the actual
      // insertion work when all shortcuts fail.

      // called by the range insert to implement [23.1.1]/9

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 438. Ambiguity in the "do the right thing" clause
      template<typename _Integer>
        void
        _M_insert_dispatch(iterator __pos,
			   _Integer __n, _Integer __x, __true_type)
        { _M_fill_insert(__pos, __n, __x); }

      // called by the range insert to implement [23.1.1]/9
      template<typename _InputIterator>
        void
        _M_insert_dispatch(iterator __pos,
			   _InputIterator __first, _InputIterator __last,
			   __false_type)
        {
	  typedef typename std::iterator_traits<_InputIterator>::
	    iterator_category _IterCategory;
          _M_range_insert_aux(__pos, __first, __last, _IterCategory());
	}

      // called by the second insert_dispatch above
      template<typename _InputIterator>
        void
        _M_range_insert_aux(iterator __pos, _InputIterator __first,
			    _InputIterator __last, std::input_iterator_tag);

      // called by the second insert_dispatch above
      template<typename _ForwardIterator>
        void
        _M_range_insert_aux(iterator __pos, _ForwardIterator __first,
			    _ForwardIterator __last, std::forward_iterator_tag);

      // Called by insert(p,n,x), and the range insert when it turns out to be
      // the same thing.  Can use fill functions in optimal situations,
      // otherwise passes off to insert_aux(p,n,x).
      void
      _M_fill_insert(iterator __pos, size_type __n, const value_type& __x);

      // called by insert(p,x)
#if __cplusplus < 201103L
      iterator
      _M_insert_aux(iterator __pos, const value_type& __x);
#else
      template<typename... _Args>
        iterator
        _M_insert_aux(iterator __pos, _Args&&... __args);
#endif

      // called by insert(p,n,x) via fill_insert
      void
      _M_insert_aux(iterator __pos, size_type __n, const value_type& __x);

      // called by range_insert_aux for forward iterators
      template<typename _ForwardIterator>
        void
        _M_insert_aux(iterator __pos,
		      _ForwardIterator __first, _ForwardIterator __last,
		      size_type __n);


      // Internal erase functions follow.

      void
      _M_destroy_data_aux(iterator __first, iterator __last);

      // Called by ~deque().
      // NB: Doesn't deallocate the nodes.
      template<typename _Alloc1>
        void
        _M_destroy_data(iterator __first, iterator __last, const _Alloc1&)
        { _M_destroy_data_aux(__first, __last); }

      void
      _M_destroy_data(iterator __first, iterator __last,
		      const std::allocator<_Tp>&)
      {
	if (!__has_trivial_destructor(value_type))
	  _M_destroy_data_aux(__first, __last);
      }

      // Called by erase(q1, q2).
      void
      _M_erase_at_begin(iterator __pos)
      {
	_M_destroy_data(begin(), __pos, _M_get_Tp_allocator());
	_M_destroy_nodes(this->_M_impl._M_start._M_node, __pos._M_node);
	this->_M_impl._M_start = __pos;
      }

      // Called by erase(q1, q2), resize(), clear(), _M_assign_aux,
      // _M_fill_assign, operator=.
      void
      _M_erase_at_end(iterator __pos)
      {
	_M_destroy_data(__pos, end(), _M_get_Tp_allocator());
	_M_destroy_nodes(__pos._M_node + 1,
			 this->_M_impl._M_finish._M_node + 1);
	this->_M_impl._M_finish = __pos;
      }

      iterator
      _M_erase(iterator __pos);

      iterator
      _M_erase(iterator __first, iterator __last);

#if __cplusplus >= 201103L
      // Called by resize(sz).
      void
      _M_default_append(size_type __n);

      bool
      _M_shrink_to_fit();
#endif

      //@{
      /// Memory-handling helpers for the previous internal insert functions.
      iterator
      _M_reserve_elements_at_front(size_type __n)
      {
	const size_type __vacancies = this->_M_impl._M_start._M_cur
	                              - this->_M_impl._M_start._M_first;
	if (__n > __vacancies)
	  _M_new_elements_at_front(__n - __vacancies);
	return this->_M_impl._M_start - difference_type(__n);
      }

      iterator
      _M_reserve_elements_at_back(size_type __n)
      {
	const size_type __vacancies = (this->_M_impl._M_finish._M_last
				       - this->_M_impl._M_finish._M_cur) - 1;
	if (__n > __vacancies)
	  _M_new_elements_at_back(__n - __vacancies);
	return this->_M_impl._M_finish + difference_type(__n);
      }

      void
      _M_new_elements_at_front(size_type __new_elements);

      void
      _M_new_elements_at_back(size_type __new_elements);
      //@}


      //@{
      /**
       *  @brief Memory-handling helpers for the major %map.
       *
       *  Makes sure the _M_map has space for new nodes.  Does not
       *  actually add the nodes.  Can invalidate _M_map pointers.
       *  (And consequently, %deque iterators.)
       */
      void
      _M_reserve_map_at_back(size_type __nodes_to_add = 1)
      {
	if (__nodes_to_add + 1 > this->_M_impl._M_map_size
	    - (this->_M_impl._M_finish._M_node - this->_M_impl._M_map))
	  _M_reallocate_map(__nodes_to_add, false);
      }

      void
      _M_reserve_map_at_front(size_type __nodes_to_add = 1)
      {
	if (__nodes_to_add > size_type(this->_M_impl._M_start._M_node
				       - this->_M_impl._M_map))
	  _M_reallocate_map(__nodes_to_add, true);
      }

      void
      _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front);
      //@}
    };


  /**
   *  @brief  Deque equality comparison.
   *  @param  __x  A %deque.
   *  @param  __y  A %deque of the same type as @a __x.
   *  @return  True iff the size and elements of the deques are equal.
   *
   *  This is an equivalence relation.  It is linear in the size of the
   *  deques.  Deques are considered equivalent if their sizes are equal,
   *  and if corresponding elements compare equal.
  */
  template<typename _Tp, typename _Alloc>
    inline bool
    operator==(const deque<_Tp, _Alloc>& __x,
                         const deque<_Tp, _Alloc>& __y)
    { return __x.size() == __y.size()
             && std::equal(__x.begin(), __x.end(), __y.begin()); }

  /**
   *  @brief  Deque ordering relation.
   *  @param  __x  A %deque.
   *  @param  __y  A %deque of the same type as @a __x.
   *  @return  True iff @a x is lexicographically less than @a __y.
   *
   *  This is a total ordering relation.  It is linear in the size of the
   *  deques.  The elements must be comparable with @c <.
   *
   *  See std::lexicographical_compare() for how the determination is made.
  */
  template<typename _Tp, typename _Alloc>
    inline bool
    operator<(const deque<_Tp, _Alloc>& __x,
	      const deque<_Tp, _Alloc>& __y)
    { return std::lexicographical_compare(__x.begin(), __x.end(),
					  __y.begin(), __y.end()); }

  /// Based on operator==
  template<typename _Tp, typename _Alloc>
    inline bool
    operator!=(const deque<_Tp, _Alloc>& __x,
	       const deque<_Tp, _Alloc>& __y)
    { return !(__x == __y); }

  /// Based on operator<
  template<typename _Tp, typename _Alloc>
    inline bool
    operator>(const deque<_Tp, _Alloc>& __x,
	      const deque<_Tp, _Alloc>& __y)
    { return __y < __x; }

  /// Based on operator<
  template<typename _Tp, typename _Alloc>
    inline bool
    operator<=(const deque<_Tp, _Alloc>& __x,
	       const deque<_Tp, _Alloc>& __y)
    { return !(__y < __x); }

  /// Based on operator<
  template<typename _Tp, typename _Alloc>
    inline bool
    operator>=(const deque<_Tp, _Alloc>& __x,
	       const deque<_Tp, _Alloc>& __y)
    { return !(__x < __y); }

  /// See std::deque::swap().
  template<typename _Tp, typename _Alloc>
    inline void
    swap(deque<_Tp,_Alloc>& __x, deque<_Tp,_Alloc>& __y)
    { __x.swap(__y); }

#undef _GLIBCXX_DEQUE_BUF_SIZE

_GLIBCXX_END_NAMESPACE_CONTAINER
} // namespace std

#endif /* _STL_DEQUE_H */
deque.tcc
// Deque implementation (out of line) -*- C++ -*-

// Copyright (C) 2001-2024 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/>.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file bits/deque.tcc
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{deque}
 */

#ifndef _DEQUE_TCC
#define _DEQUE_TCC 1

#include <bits/stl_algobase.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_BEGIN_NAMESPACE_CONTAINER

#if __cplusplus >= 201103L
  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_default_initialize()
    {
      _Map_pointer __cur;
      __try
	{
	  for (__cur = this->_M_impl._M_start._M_node;
	       __cur < this->_M_impl._M_finish._M_node;
	       ++__cur)
	    std::__uninitialized_default_a(*__cur, *__cur + _S_buffer_size(),
					   _M_get_Tp_allocator());
	  std::__uninitialized_default_a(this->_M_impl._M_finish._M_first,
					 this->_M_impl._M_finish._M_cur,
					 _M_get_Tp_allocator());
	}
      __catch(...)
	{
	  std::_Destroy(this->_M_impl._M_start, iterator(*__cur, __cur),
			_M_get_Tp_allocator());
	  __throw_exception_again;
	}
    }
#endif

  template <typename _Tp, typename _Alloc>
    deque<_Tp, _Alloc>&
    deque<_Tp, _Alloc>::
    operator=(const deque& __x)
    {
      if (std::__addressof(__x) != this)
	{
#if __cplusplus >= 201103L
	  if (_Alloc_traits::_S_propagate_on_copy_assign())
	    {
	      if (!_Alloc_traits::_S_always_equal()
		  && _M_get_Tp_allocator() != __x._M_get_Tp_allocator())
		{
		  // Replacement allocator cannot free existing storage,
		  // so deallocate everything and take copy of __x's data.
		  _M_replace_map(__x, __x.get_allocator());
		  std::__alloc_on_copy(_M_get_Tp_allocator(),
				       __x._M_get_Tp_allocator());
		  return *this;
		}
	      std::__alloc_on_copy(_M_get_Tp_allocator(),
				   __x._M_get_Tp_allocator());
	    }
#endif
	  const size_type __len = size();
	  if (__len >= __x.size())
	    _M_erase_at_end(std::copy(__x.begin(), __x.end(),
				      this->_M_impl._M_start));
	  else
	    {
	      const_iterator __mid = __x.begin() + difference_type(__len);
	      std::copy(__x.begin(), __mid, this->_M_impl._M_start);
	      _M_range_insert_aux(this->_M_impl._M_finish, __mid, __x.end(),
				  std::random_access_iterator_tag());
	    }
	}
      return *this;
    }

#if __cplusplus >= 201103L
  template<typename _Tp, typename _Alloc>
    template<typename... _Args>
#if __cplusplus > 201402L
      typename deque<_Tp, _Alloc>::reference
#else
      void
#endif
      deque<_Tp, _Alloc>::
      emplace_front(_Args&&... __args)
      {
	if (this->_M_impl._M_start._M_cur != this->_M_impl._M_start._M_first)
	  {
	    _Alloc_traits::construct(this->_M_impl,
				     this->_M_impl._M_start._M_cur - 1,
				     std::forward<_Args>(__args)...);
	    --this->_M_impl._M_start._M_cur;
	  }
	else
	  _M_push_front_aux(std::forward<_Args>(__args)...);
#if __cplusplus > 201402L
	return front();
#endif
      }

  template<typename _Tp, typename _Alloc>
    template<typename... _Args>
#if __cplusplus > 201402L
      typename deque<_Tp, _Alloc>::reference
#else
      void
#endif
      deque<_Tp, _Alloc>::
      emplace_back(_Args&&... __args)
      {
	if (this->_M_impl._M_finish._M_cur
	    != this->_M_impl._M_finish._M_last - 1)
	  {
	    _Alloc_traits::construct(this->_M_impl,
				     this->_M_impl._M_finish._M_cur,
				     std::forward<_Args>(__args)...);
	    ++this->_M_impl._M_finish._M_cur;
	  }
	else
	  _M_push_back_aux(std::forward<_Args>(__args)...);
#if __cplusplus > 201402L
	return back();
#endif
      }
#endif

#if __cplusplus >= 201103L
  template<typename _Tp, typename _Alloc>
    template<typename... _Args>
      typename deque<_Tp, _Alloc>::iterator
      deque<_Tp, _Alloc>::
      emplace(const_iterator __position, _Args&&... __args)
      {
	if (__position._M_cur == this->_M_impl._M_start._M_cur)
	  {
	    emplace_front(std::forward<_Args>(__args)...);
	    return this->_M_impl._M_start;
	  }
	else if (__position._M_cur == this->_M_impl._M_finish._M_cur)
	  {
	    emplace_back(std::forward<_Args>(__args)...);
	    iterator __tmp = this->_M_impl._M_finish;
	    --__tmp;
	    return __tmp;
	  }
	else
	  return _M_insert_aux(__position._M_const_cast(),
			       std::forward<_Args>(__args)...);
      }
#endif

  template <typename _Tp, typename _Alloc>
    typename deque<_Tp, _Alloc>::iterator
    deque<_Tp, _Alloc>::
#if __cplusplus >= 201103L
    insert(const_iterator __position, const value_type& __x)
#else
    insert(iterator __position, const value_type& __x)
#endif
    {
      if (__position._M_cur == this->_M_impl._M_start._M_cur)
	{
	  push_front(__x);
	  return this->_M_impl._M_start;
	}
      else if (__position._M_cur == this->_M_impl._M_finish._M_cur)
	{
	  push_back(__x);
	  iterator __tmp = this->_M_impl._M_finish;
	  --__tmp;
	  return __tmp;
	}
      else
	return _M_insert_aux(__position._M_const_cast(), __x);
   }

  template <typename _Tp, typename _Alloc>
    typename deque<_Tp, _Alloc>::iterator
    deque<_Tp, _Alloc>::
    _M_erase(iterator __position)
    {
      iterator __next = __position;
      ++__next;
      const difference_type __index = __position - begin();
      if (static_cast<size_type>(__index) < (size() >> 1))
	{
	  if (__position != begin())
	    _GLIBCXX_MOVE_BACKWARD3(begin(), __position, __next);
	  pop_front();
	}
      else
	{
	  if (__next != end())
	    _GLIBCXX_MOVE3(__next, end(), __position);
	  pop_back();
	}
      return begin() + __index;
    }

  template <typename _Tp, typename _Alloc>
    typename deque<_Tp, _Alloc>::iterator
    deque<_Tp, _Alloc>::
    _M_erase(iterator __first, iterator __last)
    {
      if (__first == __last)
	return __first;
      else if (__first == begin() && __last == end())
	{
	  clear();
	  return end();
	}
      else
	{
	  const difference_type __n = __last - __first;
	  const difference_type __elems_before = __first - begin();
	  if (static_cast<size_type>(__elems_before) <= (size() - __n) / 2)
	    {
	      if (__first != begin())
		_GLIBCXX_MOVE_BACKWARD3(begin(), __first, __last);
	      _M_erase_at_begin(begin() + __n);
	    }
	  else
	    {
	      if (__last != end())
		_GLIBCXX_MOVE3(__last, end(), __first);
	      _M_erase_at_end(end() - __n);
	    }
	  return begin() + __elems_before;
	}
    }

  template <typename _Tp, class _Alloc>
    template <typename _InputIterator>
      void
      deque<_Tp, _Alloc>::
      _M_assign_aux(_InputIterator __first, _InputIterator __last,
		    std::input_iterator_tag)
      {
	iterator __cur = begin();
	for (; __first != __last && __cur != end(); ++__cur, (void)++__first)
	  *__cur = *__first;
	if (__first == __last)
	  _M_erase_at_end(__cur);
	else
	  _M_range_insert_aux(end(), __first, __last,
			      std::__iterator_category(__first));
      }

  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_fill_insert(iterator __pos, size_type __n, const value_type& __x)
    {
      if (__pos._M_cur == this->_M_impl._M_start._M_cur)
	{
	  iterator __new_start = _M_reserve_elements_at_front(__n);
	  __try
	    {
	      std::__uninitialized_fill_a(__new_start, this->_M_impl._M_start,
					  __x, _M_get_Tp_allocator());
	      this->_M_impl._M_start = __new_start;
	    }
	  __catch(...)
	    {
	      _M_destroy_nodes(__new_start._M_node,
			       this->_M_impl._M_start._M_node);
	      __throw_exception_again;
	    }
	}
      else if (__pos._M_cur == this->_M_impl._M_finish._M_cur)
	{
	  iterator __new_finish = _M_reserve_elements_at_back(__n);
	  __try
	    {
	      std::__uninitialized_fill_a(this->_M_impl._M_finish,
					  __new_finish, __x,
					  _M_get_Tp_allocator());
	      this->_M_impl._M_finish = __new_finish;
	    }
	  __catch(...)
	    {
	      _M_destroy_nodes(this->_M_impl._M_finish._M_node + 1,
			       __new_finish._M_node + 1);
	      __throw_exception_again;
	    }
	}
      else
	_M_insert_aux(__pos, __n, __x);
    }

#if __cplusplus >= 201103L
  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_default_append(size_type __n)
    {
      if (__n)
	{
	  iterator __new_finish = _M_reserve_elements_at_back(__n);
	  __try
	    {
	      std::__uninitialized_default_a(this->_M_impl._M_finish,
					     __new_finish,
					     _M_get_Tp_allocator());
	      this->_M_impl._M_finish = __new_finish;
	    }
	  __catch(...)
	    {
	      _M_destroy_nodes(this->_M_impl._M_finish._M_node + 1,
			       __new_finish._M_node + 1);
	      __throw_exception_again;
	    }
	}
    }

  template <typename _Tp, typename _Alloc>
    bool
    deque<_Tp, _Alloc>::
    _M_shrink_to_fit()
    {
      const difference_type __front_capacity
	= (this->_M_impl._M_start._M_cur - this->_M_impl._M_start._M_first);
      if (__front_capacity == 0)
	return false;

      const difference_type __back_capacity
	= (this->_M_impl._M_finish._M_last - this->_M_impl._M_finish._M_cur);
      if (__front_capacity + __back_capacity < _S_buffer_size())
	return false;

      return std::__shrink_to_fit_aux<deque>::_S_do_it(*this);
    }
#endif

  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_fill_initialize(const value_type& __value)
    {
      _Map_pointer __cur;
      __try
	{
	  for (__cur = this->_M_impl._M_start._M_node;
	       __cur < this->_M_impl._M_finish._M_node;
	       ++__cur)
	    std::__uninitialized_fill_a(*__cur, *__cur + _S_buffer_size(),
					__value, _M_get_Tp_allocator());
	  std::__uninitialized_fill_a(this->_M_impl._M_finish._M_first,
				      this->_M_impl._M_finish._M_cur,
				      __value, _M_get_Tp_allocator());
	}
      __catch(...)
	{
	  std::_Destroy(this->_M_impl._M_start, iterator(*__cur, __cur),
			_M_get_Tp_allocator());
	  __throw_exception_again;
	}
    }

  template <typename _Tp, typename _Alloc>
    template <typename _InputIterator>
      void
      deque<_Tp, _Alloc>::
      _M_range_initialize(_InputIterator __first, _InputIterator __last,
			  std::input_iterator_tag)
      {
	this->_M_initialize_map(0);
	__try
	  {
	    for (; __first != __last; ++__first)
#if __cplusplus >= 201103L
	      emplace_back(*__first);
#else
	      push_back(*__first);
#endif
	  }
	__catch(...)
	  {
	    clear();
	    __throw_exception_again;
	  }
      }

  template <typename _Tp, typename _Alloc>
    template <typename _ForwardIterator>
      void
      deque<_Tp, _Alloc>::
      _M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
			  std::forward_iterator_tag)
      {
	const size_type __n = std::distance(__first, __last);
	this->_M_initialize_map(_S_check_init_len(__n, _M_get_Tp_allocator()));

	_Map_pointer __cur_node;
	__try
	  {
	    for (__cur_node = this->_M_impl._M_start._M_node;
		 __cur_node < this->_M_impl._M_finish._M_node;
		 ++__cur_node)
	      {
		if (__n < _S_buffer_size())
		  __builtin_unreachable(); // See PR 100516

		_ForwardIterator __mid = __first;
		std::advance(__mid, _S_buffer_size());
		std::__uninitialized_copy_a(__first, __mid, *__cur_node,
					    _M_get_Tp_allocator());
		__first = __mid;
	      }
	    std::__uninitialized_copy_a(__first, __last,
					this->_M_impl._M_finish._M_first,
					_M_get_Tp_allocator());
	  }
	__catch(...)
	  {
	    std::_Destroy(this->_M_impl._M_start,
			  iterator(*__cur_node, __cur_node),
			  _M_get_Tp_allocator());
	    __throw_exception_again;
	  }
      }

  // Called only if _M_impl._M_finish._M_cur == _M_impl._M_finish._M_last - 1.
  template<typename _Tp, typename _Alloc>
#if __cplusplus >= 201103L
    template<typename... _Args>
      void
      deque<_Tp, _Alloc>::
      _M_push_back_aux(_Args&&... __args)
#else
      void
      deque<_Tp, _Alloc>::
      _M_push_back_aux(const value_type& __t)
#endif
      {
	if (size() == max_size())
	  __throw_length_error(
	      __N("cannot create std::deque larger than max_size()"));

	_M_reserve_map_at_back();
	*(this->_M_impl._M_finish._M_node + 1) = this->_M_allocate_node();
	__try
	  {
#if __cplusplus >= 201103L
	    _Alloc_traits::construct(this->_M_impl,
				     this->_M_impl._M_finish._M_cur,
				     std::forward<_Args>(__args)...);
#else
	    this->_M_impl.construct(this->_M_impl._M_finish._M_cur, __t);
#endif
	    this->_M_impl._M_finish._M_set_node(this->_M_impl._M_finish._M_node
						+ 1);
	    this->_M_impl._M_finish._M_cur = this->_M_impl._M_finish._M_first;
	  }
	__catch(...)
	  {
	    _M_deallocate_node(*(this->_M_impl._M_finish._M_node + 1));
	    __throw_exception_again;
	  }
      }

  // Called only if _M_impl._M_start._M_cur == _M_impl._M_start._M_first.
  template<typename _Tp, typename _Alloc>
#if __cplusplus >= 201103L
    template<typename... _Args>
      void
      deque<_Tp, _Alloc>::
      _M_push_front_aux(_Args&&... __args)
#else
      void
      deque<_Tp, _Alloc>::
      _M_push_front_aux(const value_type& __t)
#endif
      {
	if (size() == max_size())
	  __throw_length_error(
	      __N("cannot create std::deque larger than max_size()"));

	_M_reserve_map_at_front();
	*(this->_M_impl._M_start._M_node - 1) = this->_M_allocate_node();
	__try
	  {
	    this->_M_impl._M_start._M_set_node(this->_M_impl._M_start._M_node
					       - 1);
	    this->_M_impl._M_start._M_cur = this->_M_impl._M_start._M_last - 1;
#if __cplusplus >= 201103L
	    _Alloc_traits::construct(this->_M_impl,
				     this->_M_impl._M_start._M_cur,
				     std::forward<_Args>(__args)...);
#else
	    this->_M_impl.construct(this->_M_impl._M_start._M_cur, __t);
#endif
	  }
	__catch(...)
	  {
	    ++this->_M_impl._M_start;
	    _M_deallocate_node(*(this->_M_impl._M_start._M_node - 1));
	    __throw_exception_again;
	  }
      }

  // Called only if _M_impl._M_finish._M_cur == _M_impl._M_finish._M_first.
  template <typename _Tp, typename _Alloc>
    void deque<_Tp, _Alloc>::
    _M_pop_back_aux()
    {
      _M_deallocate_node(this->_M_impl._M_finish._M_first);
      this->_M_impl._M_finish._M_set_node(this->_M_impl._M_finish._M_node - 1);
      this->_M_impl._M_finish._M_cur = this->_M_impl._M_finish._M_last - 1;
      _Alloc_traits::destroy(_M_get_Tp_allocator(),
			     this->_M_impl._M_finish._M_cur);
    }

  // Called only if _M_impl._M_start._M_cur == _M_impl._M_start._M_last - 1.
  // Note that if the deque has at least one element (a precondition for this
  // member function), and if
  //   _M_impl._M_start._M_cur == _M_impl._M_start._M_last,
  // then the deque must have at least two nodes.
  template <typename _Tp, typename _Alloc>
    void deque<_Tp, _Alloc>::
    _M_pop_front_aux()
    {
      _Alloc_traits::destroy(_M_get_Tp_allocator(),
			     this->_M_impl._M_start._M_cur);
      _M_deallocate_node(this->_M_impl._M_start._M_first);
      this->_M_impl._M_start._M_set_node(this->_M_impl._M_start._M_node + 1);
      this->_M_impl._M_start._M_cur = this->_M_impl._M_start._M_first;
    }

  template <typename _Tp, typename _Alloc>
    template <typename _InputIterator>
      void
      deque<_Tp, _Alloc>::
      _M_range_insert_aux(iterator __pos,
			  _InputIterator __first, _InputIterator __last,
			  std::input_iterator_tag)
      { std::copy(__first, __last, std::inserter(*this, __pos)); }

  template <typename _Tp, typename _Alloc>
    template <typename _ForwardIterator>
      void
      deque<_Tp, _Alloc>::
      _M_range_insert_aux(iterator __pos,
			  _ForwardIterator __first, _ForwardIterator __last,
			  std::forward_iterator_tag)
      {
	const size_type __n = std::distance(__first, __last);
	if (__pos._M_cur == this->_M_impl._M_start._M_cur)
	  {
	    iterator __new_start = _M_reserve_elements_at_front(__n);
	    __try
	      {
		std::__uninitialized_copy_a(__first, __last, __new_start,
					    _M_get_Tp_allocator());
		this->_M_impl._M_start = __new_start;
	      }
	    __catch(...)
	      {
		_M_destroy_nodes(__new_start._M_node,
				 this->_M_impl._M_start._M_node);
		__throw_exception_again;
	      }
	  }
	else if (__pos._M_cur == this->_M_impl._M_finish._M_cur)
	  {
	    iterator __new_finish = _M_reserve_elements_at_back(__n);
	    __try
	      {
		std::__uninitialized_copy_a(__first, __last,
					    this->_M_impl._M_finish,
					    _M_get_Tp_allocator());
		this->_M_impl._M_finish = __new_finish;
	      }
	    __catch(...)
	      {
		_M_destroy_nodes(this->_M_impl._M_finish._M_node + 1,
				 __new_finish._M_node + 1);
		__throw_exception_again;
	      }
	  }
	else
	  _M_insert_aux(__pos, __first, __last, __n);
      }

  template<typename _Tp, typename _Alloc>
#if __cplusplus >= 201103L
    template<typename... _Args>
      typename deque<_Tp, _Alloc>::iterator
      deque<_Tp, _Alloc>::
      _M_insert_aux(iterator __pos, _Args&&... __args)
      {
	value_type __x_copy(std::forward<_Args>(__args)...); // XXX copy
#else
    typename deque<_Tp, _Alloc>::iterator
      deque<_Tp, _Alloc>::
      _M_insert_aux(iterator __pos, const value_type& __x)
      {
	value_type __x_copy = __x; // XXX copy
#endif
	difference_type __index = __pos - this->_M_impl._M_start;
	if (static_cast<size_type>(__index) < size() / 2)
	  {
	    push_front(_GLIBCXX_MOVE(front()));
	    iterator __front1 = this->_M_impl._M_start;
	    ++__front1;
	    iterator __front2 = __front1;
	    ++__front2;
	    __pos = this->_M_impl._M_start + __index;
	    iterator __pos1 = __pos;
	    ++__pos1;
	    _GLIBCXX_MOVE3(__front2, __pos1, __front1);
	  }
	else
	  {
	    push_back(_GLIBCXX_MOVE(back()));
	    iterator __back1 = this->_M_impl._M_finish;
	    --__back1;
	    iterator __back2 = __back1;
	    --__back2;
	    __pos = this->_M_impl._M_start + __index;
	    _GLIBCXX_MOVE_BACKWARD3(__pos, __back2, __back1);
	  }
	*__pos = _GLIBCXX_MOVE(__x_copy);
	return __pos;
      }

  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_insert_aux(iterator __pos, size_type __n, const value_type& __x)
    {
      const difference_type __elems_before = __pos - this->_M_impl._M_start;
      const size_type __length = this->size();
      value_type __x_copy = __x;
      if (__elems_before < difference_type(__length / 2))
	{
	  iterator __new_start = _M_reserve_elements_at_front(__n);
	  iterator __old_start = this->_M_impl._M_start;
	  __pos = this->_M_impl._M_start + __elems_before;
	  __try
	    {
	      if (__elems_before >= difference_type(__n))
		{
		  iterator __start_n = (this->_M_impl._M_start
					+ difference_type(__n));
		  std::__uninitialized_move_a(this->_M_impl._M_start,
					      __start_n, __new_start,
					      _M_get_Tp_allocator());
		  this->_M_impl._M_start = __new_start;
		  _GLIBCXX_MOVE3(__start_n, __pos, __old_start);
		  std::fill(__pos - difference_type(__n), __pos, __x_copy);
		}
	      else
		{
		  std::__uninitialized_move_fill(this->_M_impl._M_start,
						 __pos, __new_start,
						 this->_M_impl._M_start,
						 __x_copy,
						 _M_get_Tp_allocator());
		  this->_M_impl._M_start = __new_start;
		  std::fill(__old_start, __pos, __x_copy);
		}
	    }
	  __catch(...)
	    {
	      _M_destroy_nodes(__new_start._M_node,
			       this->_M_impl._M_start._M_node);
	      __throw_exception_again;
	    }
	}
      else
	{
	  iterator __new_finish = _M_reserve_elements_at_back(__n);
	  iterator __old_finish = this->_M_impl._M_finish;
	  const difference_type __elems_after =
	    difference_type(__length) - __elems_before;
	  __pos = this->_M_impl._M_finish - __elems_after;
	  __try
	    {
	      if (__elems_after > difference_type(__n))
		{
		  iterator __finish_n = (this->_M_impl._M_finish
					 - difference_type(__n));
		  std::__uninitialized_move_a(__finish_n,
					      this->_M_impl._M_finish,
					      this->_M_impl._M_finish,
					      _M_get_Tp_allocator());
		  this->_M_impl._M_finish = __new_finish;
		  _GLIBCXX_MOVE_BACKWARD3(__pos, __finish_n, __old_finish);
		  std::fill(__pos, __pos + difference_type(__n), __x_copy);
		}
	      else
		{
		  std::__uninitialized_fill_move(this->_M_impl._M_finish,
						 __pos + difference_type(__n),
						 __x_copy, __pos,
						 this->_M_impl._M_finish,
						 _M_get_Tp_allocator());
		  this->_M_impl._M_finish = __new_finish;
		  std::fill(__pos, __old_finish, __x_copy);
		}
	    }
	  __catch(...)
	    {
	      _M_destroy_nodes(this->_M_impl._M_finish._M_node + 1,
			       __new_finish._M_node + 1);
	      __throw_exception_again;
	    }
	}
    }

  template <typename _Tp, typename _Alloc>
    template <typename _ForwardIterator>
      void
      deque<_Tp, _Alloc>::
      _M_insert_aux(iterator __pos,
		    _ForwardIterator __first, _ForwardIterator __last,
		    size_type __n)
      {
	const difference_type __elemsbefore = __pos - this->_M_impl._M_start;
	const size_type __length = size();
	if (static_cast<size_type>(__elemsbefore) < __length / 2)
	  {
	    iterator __new_start = _M_reserve_elements_at_front(__n);
	    iterator __old_start = this->_M_impl._M_start;
	    __pos = this->_M_impl._M_start + __elemsbefore;
	    __try
	      {
		if (__elemsbefore >= difference_type(__n))
		  {
		    iterator __start_n = (this->_M_impl._M_start
					  + difference_type(__n));
		    std::__uninitialized_move_a(this->_M_impl._M_start,
						__start_n, __new_start,
						_M_get_Tp_allocator());
		    this->_M_impl._M_start = __new_start;
		    _GLIBCXX_MOVE3(__start_n, __pos, __old_start);
		    std::copy(__first, __last, __pos - difference_type(__n));
		  }
		else
		  {
		    _ForwardIterator __mid = __first;
		    std::advance(__mid, difference_type(__n) - __elemsbefore);
		    std::__uninitialized_move_copy(this->_M_impl._M_start,
						   __pos, __first, __mid,
						   __new_start,
						   _M_get_Tp_allocator());
		    this->_M_impl._M_start = __new_start;
		    std::copy(__mid, __last, __old_start);
		  }
	      }
	    __catch(...)
	      {
		_M_destroy_nodes(__new_start._M_node,
				 this->_M_impl._M_start._M_node);
		__throw_exception_again;
	      }
	  }
	else
	{
	  iterator __new_finish = _M_reserve_elements_at_back(__n);
	  iterator __old_finish = this->_M_impl._M_finish;
	  const difference_type __elemsafter =
	    difference_type(__length) - __elemsbefore;
	  __pos = this->_M_impl._M_finish - __elemsafter;
	  __try
	    {
	      if (__elemsafter > difference_type(__n))
		{
		  iterator __finish_n = (this->_M_impl._M_finish
					 - difference_type(__n));
		  std::__uninitialized_move_a(__finish_n,
					      this->_M_impl._M_finish,
					      this->_M_impl._M_finish,
					      _M_get_Tp_allocator());
		  this->_M_impl._M_finish = __new_finish;
		  _GLIBCXX_MOVE_BACKWARD3(__pos, __finish_n, __old_finish);
		  std::copy(__first, __last, __pos);
		}
	      else
		{
		  _ForwardIterator __mid = __first;
		  std::advance(__mid, __elemsafter);
		  std::__uninitialized_copy_move(__mid, __last, __pos,
						 this->_M_impl._M_finish,
						 this->_M_impl._M_finish,
						 _M_get_Tp_allocator());
		  this->_M_impl._M_finish = __new_finish;
		  std::copy(__first, __mid, __pos);
		}
	    }
	  __catch(...)
	    {
	      _M_destroy_nodes(this->_M_impl._M_finish._M_node + 1,
			       __new_finish._M_node + 1);
	      __throw_exception_again;
	    }
	}
      }

   template<typename _Tp, typename _Alloc>
     void
     deque<_Tp, _Alloc>::
     _M_destroy_data_aux(iterator __first, iterator __last)
     {
       for (_Map_pointer __node = __first._M_node + 1;
	    __node < __last._M_node; ++__node)
	 std::_Destroy(*__node, *__node + _S_buffer_size(),
		       _M_get_Tp_allocator());

       if (__first._M_node != __last._M_node)
	 {
	   std::_Destroy(__first._M_cur, __first._M_last,
			 _M_get_Tp_allocator());
	   std::_Destroy(__last._M_first, __last._M_cur,
			 _M_get_Tp_allocator());
	 }
       else
	 std::_Destroy(__first._M_cur, __last._M_cur,
		       _M_get_Tp_allocator());
     }

  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_new_elements_at_front(size_type __new_elems)
    {
      if (this->max_size() - this->size() < __new_elems)
	__throw_length_error(__N("deque::_M_new_elements_at_front"));

      const size_type __new_nodes = ((__new_elems + _S_buffer_size() - 1)
				     / _S_buffer_size());
      _M_reserve_map_at_front(__new_nodes);
      size_type __i;
      __try
	{
	  for (__i = 1; __i <= __new_nodes; ++__i)
	    *(this->_M_impl._M_start._M_node - __i) = this->_M_allocate_node();
	}
      __catch(...)
	{
	  for (size_type __j = 1; __j < __i; ++__j)
	    _M_deallocate_node(*(this->_M_impl._M_start._M_node - __j));
	  __throw_exception_again;
	}
    }

  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_new_elements_at_back(size_type __new_elems)
    {
      if (this->max_size() - this->size() < __new_elems)
	__throw_length_error(__N("deque::_M_new_elements_at_back"));

      const size_type __new_nodes = ((__new_elems + _S_buffer_size() - 1)
				     / _S_buffer_size());
      _M_reserve_map_at_back(__new_nodes);
      size_type __i;
      __try
	{
	  for (__i = 1; __i <= __new_nodes; ++__i)
	    *(this->_M_impl._M_finish._M_node + __i) = this->_M_allocate_node();
	}
      __catch(...)
	{
	  for (size_type __j = 1; __j < __i; ++__j)
	    _M_deallocate_node(*(this->_M_impl._M_finish._M_node + __j));
	  __throw_exception_again;
	}
    }

  template <typename _Tp, typename _Alloc>
    void
    deque<_Tp, _Alloc>::
    _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front)
    {
      const size_type __old_num_nodes
	= this->_M_impl._M_finish._M_node - this->_M_impl._M_start._M_node + 1;
      const size_type __new_num_nodes = __old_num_nodes + __nodes_to_add;

      _Map_pointer __new_nstart;
      if (this->_M_impl._M_map_size > 2 * __new_num_nodes)
	{
	  __new_nstart = this->_M_impl._M_map + (this->_M_impl._M_map_size
					 - __new_num_nodes) / 2
			 + (__add_at_front ? __nodes_to_add : 0);
	  if (__new_nstart < this->_M_impl._M_start._M_node)
	    std::copy(this->_M_impl._M_start._M_node,
		      this->_M_impl._M_finish._M_node + 1,
		      __new_nstart);
	  else
	    std::copy_backward(this->_M_impl._M_start._M_node,
			       this->_M_impl._M_finish._M_node + 1,
			       __new_nstart + __old_num_nodes);
	}
      else
	{
	  size_type __new_map_size = this->_M_impl._M_map_size
				     + std::max(this->_M_impl._M_map_size,
						__nodes_to_add) + 2;

	  _Map_pointer __new_map = this->_M_allocate_map(__new_map_size);
	  __new_nstart = __new_map + (__new_map_size - __new_num_nodes) / 2
			 + (__add_at_front ? __nodes_to_add : 0);
	  std::copy(this->_M_impl._M_start._M_node,
		    this->_M_impl._M_finish._M_node + 1,
		    __new_nstart);
	  _M_deallocate_map(this->_M_impl._M_map, this->_M_impl._M_map_size);

	  this->_M_impl._M_map = __new_map;
	  this->_M_impl._M_map_size = __new_map_size;
	}

      this->_M_impl._M_start._M_set_node(__new_nstart);
      this->_M_impl._M_finish._M_set_node(__new_nstart + __old_num_nodes - 1);
    }

_GLIBCXX_END_NAMESPACE_CONTAINER

  // Overload for deque::iterators, exploiting the "segmented-iterator
  // optimization".
  template<typename _Tp, typename _VTp>
    void
    __fill_a1(const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>& __first,
	      const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>& __last,
	      const _VTp& __value)
    {
      typedef _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> _Iter;
      if (__first._M_node != __last._M_node)
	{
	  std::__fill_a1(__first._M_cur, __first._M_last, __value);

	  for (typename _Iter::_Map_pointer __node = __first._M_node + 1;
	       __node < __last._M_node; ++__node)
	    std::__fill_a1(*__node, *__node + _Iter::_S_buffer_size(), __value);

	  std::__fill_a1(__last._M_first, __last._M_cur, __value);
	}
      else
	std::__fill_a1(__first._M_cur, __last._M_cur, __value);
    }

  template<bool _IsMove,
	   typename _Tp, typename _Ref, typename _Ptr, typename _OI>
    _OI
    __copy_move_dit(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
		    _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
		    _OI __result)
    {
      typedef _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> _Iter;
      if (__first._M_node != __last._M_node)
	{
	  __result
	    = std::__copy_move_a1<_IsMove>(__first._M_cur, __first._M_last,
					   __result);

	  for (typename _Iter::_Map_pointer __node = __first._M_node + 1;
	       __node != __last._M_node; ++__node)
	    __result
	      = std::__copy_move_a1<_IsMove>(*__node,
					     *__node + _Iter::_S_buffer_size(),
					     __result);

	  return std::__copy_move_a1<_IsMove>(__last._M_first, __last._M_cur,
					      __result);
	}

      return std::__copy_move_a1<_IsMove>(__first._M_cur, __last._M_cur,
					  __result);
    }

  template<bool _IsMove,
	   typename _Tp, typename _Ref, typename _Ptr, typename _OI>
    _OI
    __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
		   _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
		   _OI __result)
    { return __copy_move_dit<_IsMove>(__first, __last, __result); }

  template<bool _IsMove,
	   typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
    _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
    __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
		   _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __last,
		   _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*> __result)
    { return __copy_move_dit<_IsMove>(__first, __last, __result); }

  template<bool _IsMove, typename _II, typename _Tp>
    typename __gnu_cxx::__enable_if<
      __is_random_access_iter<_II>::__value,
      _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
    __copy_move_a1(_II __first, _II __last,
		   _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> __result)
    {
      typedef _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> _Iter;
      typedef typename _Iter::difference_type difference_type;

      difference_type __len = __last - __first;
      while (__len > 0)
	{
	  const difference_type __clen
	    = std::min(__len, __result._M_last - __result._M_cur);
	  std::__copy_move_a1<_IsMove>(__first, __first + __clen,
				       __result._M_cur);

	  __first += __clen;
	  __result += __clen;
	  __len -= __clen;
	}

      return __result;
    }

  template<bool _IsMove, typename _CharT>
    typename __gnu_cxx::__enable_if<
      __is_char<_CharT>::__value,
      _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
    __copy_move_a2(
	istreambuf_iterator<_CharT, char_traits<_CharT> > __first,
	istreambuf_iterator<_CharT, char_traits<_CharT> > __last,
	_GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> __result)
    {
      if (__first == __last)
	return __result;

      for (;;)
	{
	  const std::ptrdiff_t __len = __result._M_last - __result._M_cur;
	  const std::ptrdiff_t __nb
	    = std::__copy_n_a(__first, __len, __result._M_cur, false)
	    - __result._M_cur;
	  __result += __nb;

	  if (__nb != __len)
	    break;
	}

      return __result;
    }

  template<typename _CharT, typename _Size>
    typename __gnu_cxx::__enable_if<
      __is_char<_CharT>::__value,
      _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
    __copy_n_a(
      istreambuf_iterator<_CharT, char_traits<_CharT> > __it, _Size __size,
      _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> __result,
      bool __strict)
    {
      if (__size == 0)
	return __result;

      do
	{
	  const _Size __len
	    = std::min<_Size>(__result._M_last - __result._M_cur, __size);
	  std::__copy_n_a(__it, __len, __result._M_cur, __strict);
	  __result += __len;
	  __size -= __len;
	}
      while (__size != 0);
      return __result;
    }

  template<bool _IsMove,
	   typename _Tp, typename _Ref, typename _Ptr, typename _OI>
    _OI
    __copy_move_backward_dit(
		_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
		_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
		_OI __result)
    {
      typedef _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> _Iter;
      if (__first._M_node != __last._M_node)
	{
	  __result = std::__copy_move_backward_a1<_IsMove>(
		__last._M_first, __last._M_cur, __result);

	  for (typename _Iter::_Map_pointer __node = __last._M_node - 1;
	       __node != __first._M_node; --__node)
	    __result = std::__copy_move_backward_a1<_IsMove>(
		*__node, *__node + _Iter::_S_buffer_size(), __result);

	  return std::__copy_move_backward_a1<_IsMove>(
			__first._M_cur, __first._M_last, __result);
	}

      return std::__copy_move_backward_a1<_IsMove>(
		__first._M_cur, __last._M_cur, __result);
    }

  template<bool _IsMove,
	   typename _Tp, typename _Ref, typename _Ptr, typename _OI>
    _OI
    __copy_move_backward_a1(
		_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
		_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
		_OI __result)
    { return __copy_move_backward_dit<_IsMove>(__first, __last, __result); }

  template<bool _IsMove,
	   typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
    _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
    __copy_move_backward_a1(
		_GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
		_GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __last,
		_GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*> __result)
    { return __copy_move_backward_dit<_IsMove>(__first, __last, __result); }

  template<bool _IsMove, typename _II, typename _Tp>
    typename __gnu_cxx::__enable_if<
      __is_random_access_iter<_II>::__value,
      _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
    __copy_move_backward_a1(_II __first, _II __last,
		_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> __result)
    {
      typedef _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> _Iter;
      typedef typename _Iter::difference_type difference_type;

      difference_type __len = __last - __first;
      while (__len > 0)
	{
	  difference_type __rlen = __result._M_cur - __result._M_first;
	  _Tp* __rend = __result._M_cur;
	  if (!__rlen)
	    {
	      __rlen = _Iter::_S_buffer_size();
	      __rend = *(__result._M_node - 1) + __rlen;
	    }

	  const difference_type __clen = std::min(__len, __rlen);
	  std::__copy_move_backward_a1<_IsMove>(__last - __clen, __last, __rend);

	  __last -= __clen;
	  __result -= __clen;
	  __len -= __clen;
	}

      return __result;
    }

  template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
    bool
    __equal_dit(
	const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>& __first1,
	const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>& __last1,
	_II __first2)
    {
      typedef _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> _Iter;
      if (__first1._M_node != __last1._M_node)
	{
	  if (!std::__equal_aux1(__first1._M_cur, __first1._M_last, __first2))
	    return false;

	  __first2 += __first1._M_last - __first1._M_cur;
	  for (typename _Iter::_Map_pointer __node = __first1._M_node + 1;
	       __node != __last1._M_node;
	       __first2 += _Iter::_S_buffer_size(), ++__node)
	    if (!std::__equal_aux1(*__node, *__node + _Iter::_S_buffer_size(),
				  __first2))
	      return false;

	  return std::__equal_aux1(__last1._M_first, __last1._M_cur, __first2);
	}

      return std::__equal_aux1(__first1._M_cur, __last1._M_cur, __first2);
    }

  template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
    typename __gnu_cxx::__enable_if<
      __is_random_access_iter<_II>::__value, bool>::__type
    __equal_aux1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first1,
		 _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last1,
		 _II __first2)
    { return std::__equal_dit(__first1, __last1, __first2); }

  template<typename _Tp1, typename _Ref1, typename _Ptr1,
	   typename _Tp2, typename _Ref2, typename _Ptr2>
    bool
    __equal_aux1(_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
		 _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __last1,
		 _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __first2)
    { return std::__equal_dit(__first1, __last1, __first2); }

  template<typename _II, typename _Tp, typename _Ref, typename _Ptr>
    typename __gnu_cxx::__enable_if<
      __is_random_access_iter<_II>::__value, bool>::__type
    __equal_aux1(_II __first1, _II __last1,
		_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first2)
    {
      typedef _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> _Iter;
      typedef typename _Iter::difference_type difference_type;

      difference_type __len = __last1 - __first1;
      while (__len > 0)
	{
	  const difference_type __clen
	    = std::min(__len, __first2._M_last - __first2._M_cur);
	  if (!std::__equal_aux1(__first1, __first1 + __clen, __first2._M_cur))
	    return false;

	  __first1 += __clen;
	  __len -= __clen;
	  __first2 += __clen;
	}

      return true;
    }

  template<typename _Tp1, typename _Ref, typename _Ptr, typename _Tp2>
    int
    __lex_cmp_dit(
	_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref, _Ptr> __first1,
	_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref, _Ptr> __last1,
	const _Tp2* __first2, const _Tp2* __last2)
    {
      const bool __simple =
	(__is_memcmp_ordered_with<_Tp1, _Tp2>::__value
	 && __is_pointer<_Ptr>::__value
#if __cplusplus > 201703L && __cpp_lib_concepts
	 // For C++20 iterator_traits<volatile T*>::value_type is non-volatile
	 // so __is_byte<T> could be true, but we can't use memcmp with
	 // volatile data.
	 && !is_volatile_v<_Tp1>
	 && !is_volatile_v<_Tp2>
#endif
	 );
      typedef std::__lexicographical_compare<__simple> _Lc;

      while (__first1._M_node != __last1._M_node)
	{
	  const ptrdiff_t __len1 = __first1._M_last - __first1._M_cur;
	  const ptrdiff_t __len2 = __last2 - __first2;
	  const ptrdiff_t __len = std::min(__len1, __len2);
	  // if __len1 > __len2 this will return a positive value:
	  if (int __ret = _Lc::__3way(__first1._M_cur, __first1._M_last,
				      __first2, __first2 + __len))
	    return __ret;

	  __first1 += __len;
	  __first2 += __len;
	}
      return _Lc::__3way(__first1._M_cur, __last1._M_cur,
			 __first2, __last2);
    }

  template<typename _Tp1, typename _Ref1, typename _Ptr1,
	   typename _Tp2>
    inline bool
    __lexicographical_compare_aux1(
	_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
	_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __last1,
	_Tp2* __first2, _Tp2* __last2)
    { return std::__lex_cmp_dit(__first1, __last1, __first2, __last2) < 0; }

  template<typename _Tp1,
	   typename _Tp2, typename _Ref2, typename _Ptr2>
    inline  bool
    __lexicographical_compare_aux1(_Tp1* __first1, _Tp1* __last1,
	_GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __first2,
	_GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __last2)
    { return std::__lex_cmp_dit(__first2, __last2, __first1, __last1) > 0; }

  template<typename _Tp1, typename _Ref1, typename _Ptr1,
	   typename _Tp2, typename _Ref2, typename _Ptr2>
    inline bool
    __lexicographical_compare_aux1(
		_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
		_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __last1,
		_GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __first2,
		_GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __last2)
    {
      const bool __simple =
	(__is_memcmp_ordered_with<_Tp1, _Tp2>::__value
	 && __is_pointer<_Ptr1>::__value
	 && __is_pointer<_Ptr2>::__value
#if __cplusplus > 201703L && __cpp_lib_concepts
	 // For C++20 iterator_traits<volatile T*>::value_type is non-volatile
	 // so __is_byte<T> could be true, but we can't use memcmp with
	 // volatile data.
	 && !is_volatile_v<_Tp1>
	 && !is_volatile_v<_Tp2>
#endif
	 );
      typedef std::__lexicographical_compare<__simple> _Lc;

      while (__first1 != __last1)
	{
	  const ptrdiff_t __len2 = __first2._M_node == __last2._M_node
	    ? __last2._M_cur - __first2._M_cur
	    : __first2._M_last - __first2._M_cur;
	  if (__len2 == 0)
	    return false;
	  const ptrdiff_t __len1 = __first1._M_node == __last1._M_node
	    ? __last1._M_cur - __first1._M_cur
	    : __first1._M_last - __first1._M_cur;
	  const ptrdiff_t __len = std::min(__len1, __len2);
	  if (int __ret = _Lc::__3way(__first1._M_cur, __first1._M_cur + __len,
				      __first2._M_cur, __first2._M_cur + __len))
	    return __ret < 0;

	  __first1 += __len;
	  __first2 += __len;
	}

      return __last2 != __first2;
    }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif

阅读报告:

  1. L70-L82 & L650-L733
    这一部分整体概括了STL deque的结构。

    @brief  A standard container using fixed-size memory allocation and constant-time manipulation of elements at either end.
    

    第一段是STL deque的一句话概括:使用固定大小的空间实现对首尾操作可达均摊O(1)的标准容器。

    In previous HP/SGI versions of deque, there was an extra template parameter so users could control the node size.  This extension turned out to violate the C++ standard (it can be detected using template template parameters), and it was removed.
    

    以及

    *  This function started off as a compiler kludge from SGI, but
    *  seems to be a useful wrapper around a repeated constant
    *  expression.  The @b 512 is tunable (and no other code needs to
    *  change), but no investigation has been done since inheriting the
    *  SGI code.  Touch _GLIBCXX_DEQUE_BUF_SIZE only if you know what
    *  you are doing, however: changing it breaks the binary
    *  compatibility!!
    

    第二段是对块长能否改变的解释。块长是 _GLIBCXX_DEQUE_BUF_SIZE / size_t,其中_GLIBCXX_DEQUE_BUF_SIZE的默认值是512。
    然后大意是说SGI写这部分的时候写得就很笨拙,如果改_GLIBCXX_DEQUE_BUF_SIZE的话会导致二进制兼容被破坏。不过在实操的时候由于该编译的都会重新编译,所以如果想改块长的话可以直接重新define _GLIBCXX_DEQUE_BUF_SIZE的值。
    而STL之所以不提供修改块长的函数(之前是有的,之后被删掉了),是因为这么做会破坏C++标准,所以就没有这个东西了。

    *  Here's how a deque<Tp> manages memory.  Each deque has 4 members:
    *
    *  - Tp**        _M_map
    *  - size_t      _M_map_size
    *  - iterator    _M_start, _M_finish
    *
    *  map_size is at least 8.  %map is an array of map_size
    *  pointers-to-@a nodes.  (The name %map has nothing to do with the
    *  std::map class, and @b nodes should not be confused with
    *  std::list's usage of @a node.)
    *
    *  A @a node has no specific type name as such, but it is referred
    *  to as @a node in this file.  It is a simple array-of-Tp.  If Tp
    *  is very large, there will be one Tp element per node (i.e., an
    *  @a array of one).  For non-huge Tp's, node size is inversely
    *  related to Tp size: the larger the Tp, the fewer Tp's will fit
    *  in a node.  The goal here is to keep the total size of a node
    *  relatively small and constant over different Tp's, to improve
    *  allocator efficiency.
    *
    *  Not every pointer in the %map array will point to a node.  If
    *  the initial number of elements in the deque is small, the
    *  /middle/ %map pointers will be valid, and the ones at the edges
    *  will be unused.  This same situation will arise as the %map
    *  grows: available %map pointers, if any, will be on the ends.  As
    *  new nodes are created, only a subset of the %map's pointers need
    *  to be copied @a outward.
    

    第三段是对map(我称之为中控器)的结构的描述。Tp**表示map的实现是二级指针,理解上map更像是“没有split和merge的块状链表”。map并不是所有的节点都指向buffer,换言之,map的存储形式很像一个“能双向扩展的STL vector”,即有预留空间以保证不会频繁地重构整个map。有效节点每次重构后都位于预留空间的中间,从而保证了扩展均摊是O(1)的(证明方法同vector)。
    map维护两个迭代器分别指向首尾两块,会在下面的段落解释其功用。

    * - For any nonsingular iterator i:
    *    - i.node points to a member of the %map array.  (Yes, you read that
    *      correctly:  i.node does not actually point to a node.)  The member of
    *      the %map array is what actually points to the node.
    *    - i.first == *(i.node)    (This points to the node (first Tp element).)
    *    - i.last  == i.first + node_size
    *    - i.cur is a pointer in the range [i.first, i.last).  NOTE:
    *      the implication of this is that i.cur is always a dereferenceable
    *      pointer, even if i is a past-the-end iterator.
    

    第四段是对buffer内维护的四个迭代器的定义。node指回map中指向buffer的节点,first是buffer块的头,last是buffer块的尾的下一个元素(本身还是在buffer内的,所以不必对这个“下一个元素”过于担忧),cur指向现在buffer块内存储多少元素了(cur只对首尾块是有意义的,其余块都是满的)。

    * - Start and Finish are always nonsingular iterators.  NOTE: this
    * means that an empty deque must have one node, a deque with <N
    * elements (where N is the node buffer size) must have one node, a
    * deque with N through (2N-1) elements must have two nodes, etc.
    * - For every node other than start.node and finish.node, every
    * element in the node is an initialized object.  If start.node ==
    * finish.node, then [start.cur, finish.cur) are initialized
    * objects, and the elements outside that range are uninitialized
    * storage.  Otherwise, [start.cur, start.last) and [finish.first,
    * finish.cur) are initialized objects, and [start.first, start.cur)
    * and [finish.cur, finish.last) are uninitialized storage.
    

    第五段是一些细节问题的解释。
    首先是说,即使是什么也没有存储的deque也会至少有一个buffer块(这是导致deque“最小空间开销很大”的原因)。
    然后对于首尾块内的元素存储特性的解释。首块在cur-last内存储元素,而尾块在first-cur内存储元素。

    Here's the magic:  nothing in deque is @b aware of the discontiguous storage!
    

    最后一段是一句精辟的总结。deque用分段连续的空间虽然在整体上是分段的,但是细节上依然维持地址连续的优良性质。

  2. L237-L244
    这一部分是map新建下一个buffer块的代码,可以说是map最关键的操作。

      /** 
       *  Prepares to traverse new_node.  Sets everything except
       *  _M_cur, which should therefore be set by the caller
       *  immediately afterwards, based on _M_first and _M_last.
       */
      void
      _M_set_node(_Map_pointer __new_node) _GLIBCXX_NOEXCEPT
      {
    _M_node = __new_node;
    _M_first = *__new_node;
    _M_last = _M_first + difference_type(_S_buffer_size());
      }
    

    缩进很奇怪,但原文如此。
    difference_type()是求两个迭代器之间的距离,deque在很多地方都是用的这一操作。
    first和last在建立时就确定了,而cur在call的时候才确定。

  3. L191-L230
    这一部分是buffer块内访问的实现。

    _Self&
      operator+=(difference_type __n) _GLIBCXX_NOEXCEPT
      {
    const difference_type __offset = __n + (_M_cur - _M_first);
    if (__offset >= 0 && __offset < difference_type(_S_buffer_size()))
      _M_cur += __n;
    else
      {
        const difference_type __node_offset =
          __offset > 0 ? __offset / difference_type(_S_buffer_size())
                       : -difference_type((-__offset - 1)
    				      / _S_buffer_size()) - 1;
        _M_set_node(_M_node + __node_offset);
        _M_cur = _M_first + (__offset - __node_offset
    			 * difference_type(_S_buffer_size()));
      }
    return *this;
      }
    

    其中最基本的是+=

posted @ 2025-03-19 19:02  Gokix  阅读(44)  评论(0)    收藏  举报