stl_deque.h

Go to the documentation of this file.

// Deque implementation -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004, 2005 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 2, 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.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 *
 * 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.
 */

#ifndef _DEQUE_H
#define _DEQUE_H 1

#include <bits/concept_check.h>
#include <bits/stl_iterator_base_types.h>
#include <bits/stl_iterator_base_funcs.h>

namespace _GLIBCXX_STD
{
  inline size_t
  __deque_buf_size(size_t __size)
  { return __size < 512 ? size_t(512 / __size) : size_t(1); }


  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()
      { 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)
      : _M_cur(__x), _M_first(*__y),
        _M_last(*__y + _S_buffer_size()), _M_node(__y) {}

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

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

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

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

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

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

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

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

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

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

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

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

      void
      _M_set_node(_Map_pointer __new_node)
      {
    _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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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)
    { 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 _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)
    {
      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)
    { return __x + __n; }

  template<typename _Tp, typename _Alloc>
    class _Deque_base
    {
    public:
      typedef _Alloc                  allocator_type;

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

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

      _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)
      { }

      ~_Deque_base();

    protected:
      //This struct encapsulates the implementation of the std::deque
      //standard container and at the same time makes use of the EBO
      //for empty allocators.
      typedef typename _Alloc::template rebind<_Tp*>::other _Map_alloc_type;

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

      struct _Deque_impl
      : public _Tp_alloc_type
      {
    _Tp** _M_map;
    size_t _M_map_size;
    iterator _M_start;
    iterator _M_finish;

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

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

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

      _Map_alloc_type
      _M_get_map_allocator() const
      { return _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)
      {
    _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)
      { _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);
      enum { _S_initial_map_size = 8 };

      _Deque_impl _M_impl;
    };

  template<typename _Tp, typename _Alloc>
    _Deque_base<_Tp, _Alloc>::
    ~_Deque_base()
    {
      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);
    }
    }

  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)
    {
      for (_Tp** __n = __nstart; __n < __nfinish; ++__n)
    _M_deallocate_node(*__n);
    }

  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()
      { 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;

      using _Base::_M_impl;

    public:
      // [23.2.1.1] construct/copy/destroy
      // (assign() and get_allocator() are also listed in this section)
      explicit
      deque(const allocator_type& __a = allocator_type())
      : _Base(__a, 0) {}

      explicit
      deque(size_type __n, const value_type& __value = value_type(),
        const allocator_type& __a = allocator_type())
      : _Base(__a, __n)
      { _M_fill_initialize(__value); }

      deque(const deque& __x)
      : _Base(__x.get_allocator(), __x.size())
      { std::__uninitialized_copy_a(__x.begin(), __x.end(), 
                    this->_M_impl._M_start,
                    _M_get_Tp_allocator()); }

      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());
    }

      ~deque()
      { std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
              _M_get_Tp_allocator()); }

      deque&
      operator=(const deque& __x);

      void
      assign(size_type __n, const value_type& __val)
      { _M_fill_assign(__n, __val); }

      template<typename _InputIterator>
        void
        assign(_InputIterator __first, _InputIterator __last)
        {
      typedef typename std::__is_integer<_InputIterator>::__type _Integral;
      _M_assign_dispatch(__first, __last, _Integral());
    }

      allocator_type
      get_allocator() const
      { return _Base::get_allocator(); }

      // iterators
      iterator
      begin()
      { return this->_M_impl._M_start; }

      const_iterator
      begin() const
      { return this->_M_impl._M_start; }

      iterator
      end()
      { return this->_M_impl._M_finish; }

      const_iterator
      end() const
      { return this->_M_impl._M_finish; }

      reverse_iterator
      rbegin()
      { return reverse_iterator(this->_M_impl._M_finish); }

      const_reverse_iterator
      rbegin() const
      { return const_reverse_iterator(this->_M_impl._M_finish); }

      reverse_iterator
      rend() { return reverse_iterator(this->_M_impl._M_start); }

      const_reverse_iterator
      rend() const
      { return const_reverse_iterator(this->_M_impl._M_start); }

      // [23.2.1.2] capacity
      size_type
      size() const
      { return this->_M_impl._M_finish - this->_M_impl._M_start; }

      size_type
      max_size() const
      { return size_type(-1); }

      void
      resize(size_type __new_size, value_type __x = value_type())
      {
    const size_type __len = size();
    if (__new_size < __len)
      erase(this->_M_impl._M_start + __new_size, this->_M_impl._M_finish);
    else
      insert(this->_M_impl._M_finish, __new_size - __len, __x);
      }

      bool
      empty() const
      { return this->_M_impl._M_finish == this->_M_impl._M_start; }

      // element access
      reference
      operator[](size_type __n)
      { return this->_M_impl._M_start[difference_type(__n)]; }

      const_reference
      operator[](size_type __n) const
      { return this->_M_impl._M_start[difference_type(__n)]; }

    protected:
      void
      _M_range_check(size_type __n) const
      {
    if (__n >= this->size())
      __throw_out_of_range(__N("deque::_M_range_check"));
      }

    public:
      reference
      at(size_type __n)
      {
    _M_range_check(__n);
    return (*this)[__n];
      }

      const_reference
      at(size_type __n) const
      {
    _M_range_check(__n);
    return (*this)[__n];
      }

      reference
      front()
      { return *begin(); }

      const_reference
      front() const
      { return *begin(); }

      reference
      back()
      {
    iterator __tmp = end();
    --__tmp;
    return *__tmp;
      }

      const_reference
      back() const
      {
    const_iterator __tmp = end();
    --__tmp;
    return *__tmp;
      }

      // [23.2.1.2] modifiers
      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);
      }

      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);
      }

      void
      pop_front()
      {
    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();
      }

      void
      pop_back()
      {
    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();
      }

      iterator
      insert(iterator position, const value_type& __x);

      void
      insert(iterator __position, size_type __n, const value_type& __x)
      { _M_fill_insert(__position, __n, __x); }

      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());
    }

      iterator
      erase(iterator __position);

      iterator
      erase(iterator __first, iterator __last);

      void
      swap(deque& __x)
      {
    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);
      }

      void clear();

    protected:
      // Internal constructor functions follow.

      // called by the range constructor to implement [23.1.1]/9
      template<typename _Integer>
        void
        _M_initialize_dispatch(_Integer __n, _Integer __x, __true_type)
        {
      _M_initialize_map(__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

      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);

      void
      _M_fill_initialize(const value_type& __value);

      // 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
      template<typename _Integer>
        void
        _M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
        {
      _M_fill_assign(static_cast<size_type>(__n),
             static_cast<value_type>(__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
        erase(std::copy(__first, __last, begin()), end());
    }

      // 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
      {
        erase(begin() + __n, end());
        std::fill(begin(), end(), __val);
      }
      }


      void _M_push_back_aux(const value_type&);
      void _M_push_front_aux(const value_type&);
      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
      template<typename _Integer>
        void
        _M_insert_dispatch(iterator __pos,
               _Integer __n, _Integer __x, __true_type)
        {
      _M_fill_insert(__pos, static_cast<size_type>(__n),
             static_cast<value_type>(__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)
      iterator
      _M_insert_aux(iterator __pos, const value_type& __x);

      // 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);


      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);



      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);
    };


  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()); }

  template<typename _Tp, typename _Alloc>
    inline bool
    operator<(const deque<_Tp, _Alloc>& __x,
          const deque<_Tp, _Alloc>& __y)
    { return lexicographical_compare(__x.begin(), __x.end(),
                     __y.begin(), __y.end()); }

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

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

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

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

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

#endif /* _DEQUE_H */

---