1// Deque implementation -*- C++ -*-
2
3// Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 2, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// You should have received a copy of the GNU General Public License along
17// with this library; see the file COPYING.  If not, write to the Free
18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
19// USA.
20
21// As a special exception, you may use this file as part of a free software
22// library without restriction.  Specifically, if other files instantiate
23// templates or use macros or inline functions from this file, or you compile
24// this file and link it with other files to produce an executable, this
25// file does not by itself cause the resulting executable to be covered by
26// the GNU General Public License.  This exception does not however
27// invalidate any other reasons why the executable file might be covered by
28// the GNU General Public License.
29
30/*
31 *
32 * Copyright (c) 1994
33 * Hewlett-Packard Company
34 *
35 * Permission to use, copy, modify, distribute and sell this software
36 * and its documentation for any purpose is hereby granted without fee,
37 * provided that the above copyright notice appear in all copies and
38 * that both that copyright notice and this permission notice appear
39 * in supporting documentation.  Hewlett-Packard Company makes no
40 * representations about the suitability of this software for any
41 * purpose.  It is provided "as is" without express or implied warranty.
42 *
43 *
44 * Copyright (c) 1997
45 * Silicon Graphics Computer Systems, Inc.
46 *
47 * Permission to use, copy, modify, distribute and sell this software
48 * and its documentation for any purpose is hereby granted without fee,
49 * provided that the above copyright notice appear in all copies and
50 * that both that copyright notice and this permission notice appear
51 * in supporting documentation.  Silicon Graphics makes no
52 * representations about the suitability of this software for any
53 * purpose.  It is provided "as is" without express or implied warranty.
54 */
55
56/** @file stl_deque.h
57 *  This is an internal header file, included by other library headers.
58 *  You should not attempt to use it directly.
59 */
60
61#ifndef _DEQUE_H
62#define _DEQUE_H 1
63
64#include <bits/concept_check.h>
65#include <bits/stl_iterator_base_types.h>
66#include <bits/stl_iterator_base_funcs.h>
67
68namespace _GLIBCXX_STD
69{
70  /**
71   *  @if maint
72   *  @brief This function controls the size of memory nodes.
73   *  @param  size  The size of an element.
74   *  @return   The number (not byte size) of elements per node.
75   *
76   *  This function started off as a compiler kludge from SGI, but seems to
77   *  be a useful wrapper around a repeated constant expression.  The '512' is
78   *  tuneable (and no other code needs to change), but no investigation has
79   *  been done since inheriting the SGI code.
80   *  @endif
81  */
82  inline size_t
83  __deque_buf_size(size_t __size)
84  { return __size < 512 ? size_t(512 / __size) : size_t(1); }
85
86
87  /**
88   *  @brief A deque::iterator.
89   *
90   *  Quite a bit of intelligence here.  Much of the functionality of
91   *  deque is actually passed off to this class.  A deque holds two
92   *  of these internally, marking its valid range.  Access to
93   *  elements is done as offsets of either of those two, relying on
94   *  operator overloading in this class.
95   *
96   *  @if maint
97   *  All the functions are op overloads except for _M_set_node.
98   *  @endif
99  */
100  template<typename _Tp, typename _Ref, typename _Ptr>
101    struct _Deque_iterator
102    {
103      typedef _Deque_iterator<_Tp, _Tp&, _Tp*>             iterator;
104      typedef _Deque_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;
105
106      static size_t _S_buffer_size()
107      { return __deque_buf_size(sizeof(_Tp)); }
108
109      typedef std::random_access_iterator_tag iterator_category;
110      typedef _Tp                             value_type;
111      typedef _Ptr                            pointer;
112      typedef _Ref                            reference;
113      typedef size_t                          size_type;
114      typedef ptrdiff_t                       difference_type;
115      typedef _Tp**                           _Map_pointer;
116      typedef _Deque_iterator                 _Self;
117
118      _Tp* _M_cur;
119      _Tp* _M_first;
120      _Tp* _M_last;
121      _Map_pointer _M_node;
122
123      _Deque_iterator(_Tp* __x, _Map_pointer __y)
124      : _M_cur(__x), _M_first(*__y),
125        _M_last(*__y + _S_buffer_size()), _M_node(__y) {}
126
127      _Deque_iterator() : _M_cur(0), _M_first(0), _M_last(0), _M_node(0) {}
128
129      _Deque_iterator(const iterator& __x)
130      : _M_cur(__x._M_cur), _M_first(__x._M_first),
131        _M_last(__x._M_last), _M_node(__x._M_node) {}
132
133      reference
134      operator*() const
135      { return *_M_cur; }
136
137      pointer
138      operator->() const
139      { return _M_cur; }
140
141      _Self&
142      operator++()
143      {
144	++_M_cur;
145	if (_M_cur == _M_last)
146	  {
147	    _M_set_node(_M_node + 1);
148	    _M_cur = _M_first;
149	  }
150	return *this;
151      }
152
153      _Self
154      operator++(int)
155      {
156	_Self __tmp = *this;
157	++*this;
158	return __tmp;
159      }
160
161      _Self&
162      operator--()
163      {
164	if (_M_cur == _M_first)
165	  {
166	    _M_set_node(_M_node - 1);
167	    _M_cur = _M_last;
168	  }
169	--_M_cur;
170	return *this;
171      }
172
173      _Self
174      operator--(int)
175      {
176	_Self __tmp = *this;
177	--*this;
178	return __tmp;
179      }
180
181      _Self&
182      operator+=(difference_type __n)
183      {
184	const difference_type __offset = __n + (_M_cur - _M_first);
185	if (__offset >= 0 && __offset < difference_type(_S_buffer_size()))
186	  _M_cur += __n;
187	else
188	  {
189	    const difference_type __node_offset =
190	      __offset > 0 ? __offset / difference_type(_S_buffer_size())
191	                   : -difference_type((-__offset - 1)
192					      / _S_buffer_size()) - 1;
193	    _M_set_node(_M_node + __node_offset);
194	    _M_cur = _M_first + (__offset - __node_offset
195				 * difference_type(_S_buffer_size()));
196	  }
197	return *this;
198      }
199
200      _Self
201      operator+(difference_type __n) const
202      {
203	_Self __tmp = *this;
204	return __tmp += __n;
205      }
206
207      _Self&
208      operator-=(difference_type __n)
209      { return *this += -__n; }
210
211      _Self
212      operator-(difference_type __n) const
213      {
214	_Self __tmp = *this;
215	return __tmp -= __n;
216      }
217
218      reference
219      operator[](difference_type __n) const
220      { return *(*this + __n); }
221
222      /** @if maint
223       *  Prepares to traverse new_node.  Sets everything except
224       *  _M_cur, which should therefore be set by the caller
225       *  immediately afterwards, based on _M_first and _M_last.
226       *  @endif
227       */
228      void
229      _M_set_node(_Map_pointer __new_node)
230      {
231	_M_node = __new_node;
232	_M_first = *__new_node;
233	_M_last = _M_first + difference_type(_S_buffer_size());
234      }
235    };
236
237  // Note: we also provide overloads whose operands are of the same type in
238  // order to avoid ambiguous overload resolution when std::rel_ops operators
239  // are in scope (for additional details, see libstdc++/3628)
240  template<typename _Tp, typename _Ref, typename _Ptr>
241    inline bool
242    operator==(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
243	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
244    { return __x._M_cur == __y._M_cur; }
245
246  template<typename _Tp, typename _RefL, typename _PtrL,
247	   typename _RefR, typename _PtrR>
248    inline bool
249    operator==(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
250	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
251    { return __x._M_cur == __y._M_cur; }
252
253  template<typename _Tp, typename _Ref, typename _Ptr>
254    inline bool
255    operator!=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
256	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
257    { return !(__x == __y); }
258
259  template<typename _Tp, typename _RefL, typename _PtrL,
260	   typename _RefR, typename _PtrR>
261    inline bool
262    operator!=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
263	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
264    { return !(__x == __y); }
265
266  template<typename _Tp, typename _Ref, typename _Ptr>
267    inline bool
268    operator<(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
269	      const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
270    { return (__x._M_node == __y._M_node) ? (__x._M_cur < __y._M_cur)
271                                          : (__x._M_node < __y._M_node); }
272
273  template<typename _Tp, typename _RefL, typename _PtrL,
274	   typename _RefR, typename _PtrR>
275    inline bool
276    operator<(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
277	      const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
278    { return (__x._M_node == __y._M_node) ? (__x._M_cur < __y._M_cur)
279	                                  : (__x._M_node < __y._M_node); }
280
281  template<typename _Tp, typename _Ref, typename _Ptr>
282    inline bool
283    operator>(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
284	      const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
285    { return __y < __x; }
286
287  template<typename _Tp, typename _RefL, typename _PtrL,
288	   typename _RefR, typename _PtrR>
289    inline bool
290    operator>(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
291	      const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
292    { return __y < __x; }
293
294  template<typename _Tp, typename _Ref, typename _Ptr>
295    inline bool
296    operator<=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
297	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
298    { return !(__y < __x); }
299
300  template<typename _Tp, typename _RefL, typename _PtrL,
301	   typename _RefR, typename _PtrR>
302    inline bool
303    operator<=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
304	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
305    { return !(__y < __x); }
306
307  template<typename _Tp, typename _Ref, typename _Ptr>
308    inline bool
309    operator>=(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x,
310	       const _Deque_iterator<_Tp, _Ref, _Ptr>& __y)
311    { return !(__x < __y); }
312
313  template<typename _Tp, typename _RefL, typename _PtrL,
314	   typename _RefR, typename _PtrR>
315    inline bool
316    operator>=(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
317	       const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
318    { return !(__x < __y); }
319
320  // _GLIBCXX_RESOLVE_LIB_DEFECTS
321  // According to the resolution of DR179 not only the various comparison
322  // operators but also operator- must accept mixed iterator/const_iterator
323  // parameters.
324  template<typename _Tp, typename _RefL, typename _PtrL,
325	   typename _RefR, typename _PtrR>
326    inline typename _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
327    operator-(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
328	      const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
329    {
330      return typename _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
331	(_Deque_iterator<_Tp, _RefL, _PtrL>::_S_buffer_size())
332	* (__x._M_node - __y._M_node - 1) + (__x._M_cur - __x._M_first)
333	+ (__y._M_last - __y._M_cur);
334    }
335
336  template<typename _Tp, typename _Ref, typename _Ptr>
337    inline _Deque_iterator<_Tp, _Ref, _Ptr>
338    operator+(ptrdiff_t __n, const _Deque_iterator<_Tp, _Ref, _Ptr>& __x)
339    { return __x + __n; }
340
341  /**
342   *  @if maint
343   *  Deque base class.  This class provides the unified face for %deque's
344   *  allocation.  This class's constructor and destructor allocate and
345   *  deallocate (but do not initialize) storage.  This makes %exception
346   *  safety easier.
347   *
348   *  Nothing in this class ever constructs or destroys an actual Tp element.
349   *  (Deque handles that itself.)  Only/All memory management is performed
350   *  here.
351   *  @endif
352  */
353  template<typename _Tp, typename _Alloc>
354    class _Deque_base
355    {
356    public:
357      typedef _Alloc                  allocator_type;
358
359      allocator_type
360      get_allocator() const
361      { return _M_get_Tp_allocator(); }
362
363      typedef _Deque_iterator<_Tp, _Tp&, _Tp*>             iterator;
364      typedef _Deque_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;
365
366      _Deque_base(const allocator_type& __a, size_t __num_elements)
367      : _M_impl(__a)
368      { _M_initialize_map(__num_elements); }
369
370      _Deque_base(const allocator_type& __a)
371      : _M_impl(__a)
372      { }
373
374      ~_Deque_base();
375
376    protected:
377      //This struct encapsulates the implementation of the std::deque
378      //standard container and at the same time makes use of the EBO
379      //for empty allocators.
380      typedef typename _Alloc::template rebind<_Tp*>::other _Map_alloc_type;
381
382      typedef typename _Alloc::template rebind<_Tp>::other  _Tp_alloc_type;
383
384      struct _Deque_impl
385      : public _Tp_alloc_type
386      {
387	_Tp** _M_map;
388	size_t _M_map_size;
389	iterator _M_start;
390	iterator _M_finish;
391
392	_Deque_impl(const _Tp_alloc_type& __a)
393	: _Tp_alloc_type(__a), _M_map(0), _M_map_size(0),
394	  _M_start(), _M_finish()
395	{ }
396      };
397
398      _Tp_alloc_type&
399      _M_get_Tp_allocator()
400      { return *static_cast<_Tp_alloc_type*>(&this->_M_impl); }
401
402      const _Tp_alloc_type&
403      _M_get_Tp_allocator() const
404      { return *static_cast<const _Tp_alloc_type*>(&this->_M_impl); }
405
406      _Map_alloc_type
407      _M_get_map_allocator() const
408      { return _M_get_Tp_allocator(); }
409
410      _Tp*
411      _M_allocate_node()
412      {
413	return _M_impl._Tp_alloc_type::allocate(__deque_buf_size(sizeof(_Tp)));
414      }
415
416      void
417      _M_deallocate_node(_Tp* __p)
418      {
419	_M_impl._Tp_alloc_type::deallocate(__p, __deque_buf_size(sizeof(_Tp)));
420      }
421
422      _Tp**
423      _M_allocate_map(size_t __n)
424      { return _M_get_map_allocator().allocate(__n); }
425
426      void
427      _M_deallocate_map(_Tp** __p, size_t __n)
428      { _M_get_map_allocator().deallocate(__p, __n); }
429
430    protected:
431      void _M_initialize_map(size_t);
432      void _M_create_nodes(_Tp** __nstart, _Tp** __nfinish);
433      void _M_destroy_nodes(_Tp** __nstart, _Tp** __nfinish);
434      enum { _S_initial_map_size = 8 };
435
436      _Deque_impl _M_impl;
437    };
438
439  template<typename _Tp, typename _Alloc>
440    _Deque_base<_Tp, _Alloc>::
441    ~_Deque_base()
442    {
443      if (this->_M_impl._M_map)
444	{
445	  _M_destroy_nodes(this->_M_impl._M_start._M_node,
446			   this->_M_impl._M_finish._M_node + 1);
447	  _M_deallocate_map(this->_M_impl._M_map, this->_M_impl._M_map_size);
448	}
449    }
450
451  /**
452   *  @if maint
453   *  @brief Layout storage.
454   *  @param  num_elements  The count of T's for which to allocate space
455   *                        at first.
456   *  @return   Nothing.
457   *
458   *  The initial underlying memory layout is a bit complicated...
459   *  @endif
460  */
461  template<typename _Tp, typename _Alloc>
462    void
463    _Deque_base<_Tp, _Alloc>::
464    _M_initialize_map(size_t __num_elements)
465    {
466      const size_t __num_nodes = (__num_elements/ __deque_buf_size(sizeof(_Tp))
467				  + 1);
468
469      this->_M_impl._M_map_size = std::max((size_t) _S_initial_map_size,
470					   size_t(__num_nodes + 2));
471      this->_M_impl._M_map = _M_allocate_map(this->_M_impl._M_map_size);
472
473      // For "small" maps (needing less than _M_map_size nodes), allocation
474      // starts in the middle elements and grows outwards.  So nstart may be
475      // the beginning of _M_map, but for small maps it may be as far in as
476      // _M_map+3.
477
478      _Tp** __nstart = (this->_M_impl._M_map
479			+ (this->_M_impl._M_map_size - __num_nodes) / 2);
480      _Tp** __nfinish = __nstart + __num_nodes;
481
482      try
483	{ _M_create_nodes(__nstart, __nfinish); }
484      catch(...)
485	{
486	  _M_deallocate_map(this->_M_impl._M_map, this->_M_impl._M_map_size);
487	  this->_M_impl._M_map = 0;
488	  this->_M_impl._M_map_size = 0;
489	  __throw_exception_again;
490	}
491
492      this->_M_impl._M_start._M_set_node(__nstart);
493      this->_M_impl._M_finish._M_set_node(__nfinish - 1);
494      this->_M_impl._M_start._M_cur = _M_impl._M_start._M_first;
495      this->_M_impl._M_finish._M_cur = (this->_M_impl._M_finish._M_first
496					+ __num_elements
497					% __deque_buf_size(sizeof(_Tp)));
498    }
499
500  template<typename _Tp, typename _Alloc>
501    void
502    _Deque_base<_Tp, _Alloc>::
503    _M_create_nodes(_Tp** __nstart, _Tp** __nfinish)
504    {
505      _Tp** __cur;
506      try
507	{
508	  for (__cur = __nstart; __cur < __nfinish; ++__cur)
509	    *__cur = this->_M_allocate_node();
510	}
511      catch(...)
512	{
513	  _M_destroy_nodes(__nstart, __cur);
514	  __throw_exception_again;
515	}
516    }
517
518  template<typename _Tp, typename _Alloc>
519    void
520    _Deque_base<_Tp, _Alloc>::
521    _M_destroy_nodes(_Tp** __nstart, _Tp** __nfinish)
522    {
523      for (_Tp** __n = __nstart; __n < __nfinish; ++__n)
524	_M_deallocate_node(*__n);
525    }
526
527  /**
528   *  @brief  A standard container using fixed-size memory allocation and
529   *  constant-time manipulation of elements at either end.
530   *
531   *  @ingroup Containers
532   *  @ingroup Sequences
533   *
534   *  Meets the requirements of a <a href="tables.html#65">container</a>, a
535   *  <a href="tables.html#66">reversible container</a>, and a
536   *  <a href="tables.html#67">sequence</a>, including the
537   *  <a href="tables.html#68">optional sequence requirements</a>.
538   *
539   *  In previous HP/SGI versions of deque, there was an extra template
540   *  parameter so users could control the node size.  This extension turned
541   *  out to violate the C++ standard (it can be detected using template
542   *  template parameters), and it was removed.
543   *
544   *  @if maint
545   *  Here's how a deque<Tp> manages memory.  Each deque has 4 members:
546   *
547   *  - Tp**        _M_map
548   *  - size_t      _M_map_size
549   *  - iterator    _M_start, _M_finish
550   *
551   *  map_size is at least 8.  %map is an array of map_size
552   *  pointers-to-"nodes".  (The name %map has nothing to do with the
553   *  std::map class, and "nodes" should not be confused with
554   *  std::list's usage of "node".)
555   *
556   *  A "node" has no specific type name as such, but it is referred
557   *  to as "node" in this file.  It is a simple array-of-Tp.  If Tp
558   *  is very large, there will be one Tp element per node (i.e., an
559   *  "array" of one).  For non-huge Tp's, node size is inversely
560   *  related to Tp size: the larger the Tp, the fewer Tp's will fit
561   *  in a node.  The goal here is to keep the total size of a node
562   *  relatively small and constant over different Tp's, to improve
563   *  allocator efficiency.
564   *
565   *  Not every pointer in the %map array will point to a node.  If
566   *  the initial number of elements in the deque is small, the
567   *  /middle/ %map pointers will be valid, and the ones at the edges
568   *  will be unused.  This same situation will arise as the %map
569   *  grows: available %map pointers, if any, will be on the ends.  As
570   *  new nodes are created, only a subset of the %map's pointers need
571   *  to be copied "outward".
572   *
573   *  Class invariants:
574   * - For any nonsingular iterator i:
575   *    - i.node points to a member of the %map array.  (Yes, you read that
576   *      correctly:  i.node does not actually point to a node.)  The member of
577   *      the %map array is what actually points to the node.
578   *    - i.first == *(i.node)    (This points to the node (first Tp element).)
579   *    - i.last  == i.first + node_size
580   *    - i.cur is a pointer in the range [i.first, i.last).  NOTE:
581   *      the implication of this is that i.cur is always a dereferenceable
582   *      pointer, even if i is a past-the-end iterator.
583   * - Start and Finish are always nonsingular iterators.  NOTE: this
584   * means that an empty deque must have one node, a deque with <N
585   * elements (where N is the node buffer size) must have one node, a
586   * deque with N through (2N-1) elements must have two nodes, etc.
587   * - For every node other than start.node and finish.node, every
588   * element in the node is an initialized object.  If start.node ==
589   * finish.node, then [start.cur, finish.cur) are initialized
590   * objects, and the elements outside that range are uninitialized
591   * storage.  Otherwise, [start.cur, start.last) and [finish.first,
592   * finish.cur) are initialized objects, and [start.first, start.cur)
593   * and [finish.cur, finish.last) are uninitialized storage.
594   * - [%map, %map + map_size) is a valid, non-empty range.
595   * - [start.node, finish.node] is a valid range contained within
596   *   [%map, %map + map_size).
597   * - A pointer in the range [%map, %map + map_size) points to an allocated
598   *   node if and only if the pointer is in the range
599   *   [start.node, finish.node].
600   *
601   *  Here's the magic:  nothing in deque is "aware" of the discontiguous
602   *  storage!
603   *
604   *  The memory setup and layout occurs in the parent, _Base, and the iterator
605   *  class is entirely responsible for "leaping" from one node to the next.
606   *  All the implementation routines for deque itself work only through the
607   *  start and finish iterators.  This keeps the routines simple and sane,
608   *  and we can use other standard algorithms as well.
609   *  @endif
610  */
611  template<typename _Tp, typename _Alloc = std::allocator<_Tp> >
612    class deque : protected _Deque_base<_Tp, _Alloc>
613    {
614      // concept requirements
615      typedef typename _Alloc::value_type        _Alloc_value_type;
616      __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
617      __glibcxx_class_requires2(_Tp, _Alloc_value_type, _SameTypeConcept)
618
619      typedef _Deque_base<_Tp, _Alloc>           _Base;
620      typedef typename _Base::_Tp_alloc_type	 _Tp_alloc_type;
621
622    public:
623      typedef _Tp                                        value_type;
624      typedef typename _Tp_alloc_type::pointer           pointer;
625      typedef typename _Tp_alloc_type::const_pointer     const_pointer;
626      typedef typename _Tp_alloc_type::reference         reference;
627      typedef typename _Tp_alloc_type::const_reference   const_reference;
628      typedef typename _Base::iterator                   iterator;
629      typedef typename _Base::const_iterator             const_iterator;
630      typedef std::reverse_iterator<const_iterator>      const_reverse_iterator;
631      typedef std::reverse_iterator<iterator>            reverse_iterator;
632      typedef size_t                             size_type;
633      typedef ptrdiff_t                          difference_type;
634      typedef _Alloc                             allocator_type;
635
636    protected:
637      typedef pointer*                           _Map_pointer;
638
639      static size_t _S_buffer_size()
640      { return __deque_buf_size(sizeof(_Tp)); }
641
642      // Functions controlling memory layout, and nothing else.
643      using _Base::_M_initialize_map;
644      using _Base::_M_create_nodes;
645      using _Base::_M_destroy_nodes;
646      using _Base::_M_allocate_node;
647      using _Base::_M_deallocate_node;
648      using _Base::_M_allocate_map;
649      using _Base::_M_deallocate_map;
650      using _Base::_M_get_Tp_allocator;
651
652      /** @if maint
653       *  A total of four data members accumulated down the heirarchy.
654       *  May be accessed via _M_impl.*
655       *  @endif
656       */
657      using _Base::_M_impl;
658
659    public:
660      // [23.2.1.1] construct/copy/destroy
661      // (assign() and get_allocator() are also listed in this section)
662      /**
663       *  @brief  Default constructor creates no elements.
664       */
665      explicit
666      deque(const allocator_type& __a = allocator_type())
667      : _Base(__a, 0) {}
668
669      /**
670       *  @brief  Create a %deque with copies of an exemplar element.
671       *  @param  n  The number of elements to initially create.
672       *  @param  value  An element to copy.
673       *
674       *  This constructor fills the %deque with @a n copies of @a value.
675       */
676      explicit
677      deque(size_type __n, const value_type& __value = value_type(),
678	    const allocator_type& __a = allocator_type())
679      : _Base(__a, __n)
680      { _M_fill_initialize(__value); }
681
682      /**
683       *  @brief  %Deque copy constructor.
684       *  @param  x  A %deque of identical element and allocator types.
685       *
686       *  The newly-created %deque uses a copy of the allocation object used
687       *  by @a x.
688       */
689      deque(const deque& __x)
690      : _Base(__x.get_allocator(), __x.size())
691      { std::__uninitialized_copy_a(__x.begin(), __x.end(),
692				    this->_M_impl._M_start,
693				    _M_get_Tp_allocator()); }
694
695      /**
696       *  @brief  Builds a %deque from a range.
697       *  @param  first  An input iterator.
698       *  @param  last  An input iterator.
699       *
700       *  Create a %deque consisting of copies of the elements from [first,
701       *  last).
702       *
703       *  If the iterators are forward, bidirectional, or random-access, then
704       *  this will call the elements' copy constructor N times (where N is
705       *  distance(first,last)) and do no memory reallocation.  But if only
706       *  input iterators are used, then this will do at most 2N calls to the
707       *  copy constructor, and logN memory reallocations.
708       */
709      template<typename _InputIterator>
710        deque(_InputIterator __first, _InputIterator __last,
711	      const allocator_type& __a = allocator_type())
712	: _Base(__a)
713        {
714	  // Check whether it's an integral type.  If so, it's not an iterator.
715	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
716	  _M_initialize_dispatch(__first, __last, _Integral());
717	}
718
719      /**
720       *  The dtor only erases the elements, and note that if the elements
721       *  themselves are pointers, the pointed-to memory is not touched in any
722       *  way.  Managing the pointer is the user's responsibilty.
723       */
724      ~deque()
725      { std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
726		      _M_get_Tp_allocator()); }
727
728      /**
729       *  @brief  %Deque assignment operator.
730       *  @param  x  A %deque of identical element and allocator types.
731       *
732       *  All the elements of @a x are copied, but unlike the copy constructor,
733       *  the allocator object is not copied.
734       */
735      deque&
736      operator=(const deque& __x);
737
738      /**
739       *  @brief  Assigns a given value to a %deque.
740       *  @param  n  Number of elements to be assigned.
741       *  @param  val  Value to be assigned.
742       *
743       *  This function fills a %deque with @a n copies of the given
744       *  value.  Note that the assignment completely changes the
745       *  %deque and that the resulting %deque's size is the same as
746       *  the number of elements assigned.  Old data may be lost.
747       */
748      void
749      assign(size_type __n, const value_type& __val)
750      { _M_fill_assign(__n, __val); }
751
752      /**
753       *  @brief  Assigns a range to a %deque.
754       *  @param  first  An input iterator.
755       *  @param  last   An input iterator.
756       *
757       *  This function fills a %deque with copies of the elements in the
758       *  range [first,last).
759       *
760       *  Note that the assignment completely changes the %deque and that the
761       *  resulting %deque's size is the same as the number of elements
762       *  assigned.  Old data may be lost.
763       */
764      template<typename _InputIterator>
765        void
766        assign(_InputIterator __first, _InputIterator __last)
767        {
768	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
769	  _M_assign_dispatch(__first, __last, _Integral());
770	}
771
772      /// Get a copy of the memory allocation object.
773      allocator_type
774      get_allocator() const
775      { return _Base::get_allocator(); }
776
777      // iterators
778      /**
779       *  Returns a read/write iterator that points to the first element in the
780       *  %deque.  Iteration is done in ordinary element order.
781       */
782      iterator
783      begin()
784      { return this->_M_impl._M_start; }
785
786      /**
787       *  Returns a read-only (constant) iterator that points to the first
788       *  element in the %deque.  Iteration is done in ordinary element order.
789       */
790      const_iterator
791      begin() const
792      { return this->_M_impl._M_start; }
793
794      /**
795       *  Returns a read/write iterator that points one past the last
796       *  element in the %deque.  Iteration is done in ordinary
797       *  element order.
798       */
799      iterator
800      end()
801      { return this->_M_impl._M_finish; }
802
803      /**
804       *  Returns a read-only (constant) iterator that points one past
805       *  the last element in the %deque.  Iteration is done in
806       *  ordinary element order.
807       */
808      const_iterator
809      end() const
810      { return this->_M_impl._M_finish; }
811
812      /**
813       *  Returns a read/write reverse iterator that points to the
814       *  last element in the %deque.  Iteration is done in reverse
815       *  element order.
816       */
817      reverse_iterator
818      rbegin()
819      { return reverse_iterator(this->_M_impl._M_finish); }
820
821      /**
822       *  Returns a read-only (constant) reverse iterator that points
823       *  to the last element in the %deque.  Iteration is done in
824       *  reverse element order.
825       */
826      const_reverse_iterator
827      rbegin() const
828      { return const_reverse_iterator(this->_M_impl._M_finish); }
829
830      /**
831       *  Returns a read/write reverse iterator that points to one
832       *  before the first element in the %deque.  Iteration is done
833       *  in reverse element order.
834       */
835      reverse_iterator
836      rend() { return reverse_iterator(this->_M_impl._M_start); }
837
838      /**
839       *  Returns a read-only (constant) reverse iterator that points
840       *  to one before the first element in the %deque.  Iteration is
841       *  done in reverse element order.
842       */
843      const_reverse_iterator
844      rend() const
845      { return const_reverse_iterator(this->_M_impl._M_start); }
846
847      // [23.2.1.2] capacity
848      /**  Returns the number of elements in the %deque.  */
849      size_type
850      size() const
851      { return this->_M_impl._M_finish - this->_M_impl._M_start; }
852
853      /**  Returns the size() of the largest possible %deque.  */
854      size_type
855      max_size() const
856      { return size_type(-1); }
857
858      /**
859       *  @brief  Resizes the %deque to the specified number of elements.
860       *  @param  new_size  Number of elements the %deque should contain.
861       *  @param  x  Data with which new elements should be populated.
862       *
863       *  This function will %resize the %deque to the specified
864       *  number of elements.  If the number is smaller than the
865       *  %deque's current size the %deque is truncated, otherwise the
866       *  %deque is extended and new elements are populated with given
867       *  data.
868       */
869      void
870      resize(size_type __new_size, value_type __x = value_type())
871      {
872	const size_type __len = size();
873	if (__new_size < __len)
874	  erase(this->_M_impl._M_start + __new_size, this->_M_impl._M_finish);
875	else
876	  insert(this->_M_impl._M_finish, __new_size - __len, __x);
877      }
878
879      /**
880       *  Returns true if the %deque is empty.  (Thus begin() would
881       *  equal end().)
882       */
883      bool
884      empty() const
885      { return this->_M_impl._M_finish == this->_M_impl._M_start; }
886
887      // element access
888      /**
889       *  @brief Subscript access to the data contained in the %deque.
890       *  @param n The index of the element for which data should be
891       *  accessed.
892       *  @return  Read/write reference to data.
893       *
894       *  This operator allows for easy, array-style, data access.
895       *  Note that data access with this operator is unchecked and
896       *  out_of_range lookups are not defined. (For checked lookups
897       *  see at().)
898       */
899      reference
900      operator[](size_type __n)
901      { return this->_M_impl._M_start[difference_type(__n)]; }
902
903      /**
904       *  @brief Subscript access to the data contained in the %deque.
905       *  @param n The index of the element for which data should be
906       *  accessed.
907       *  @return  Read-only (constant) reference to data.
908       *
909       *  This operator allows for easy, array-style, data access.
910       *  Note that data access with this operator is unchecked and
911       *  out_of_range lookups are not defined. (For checked lookups
912       *  see at().)
913       */
914      const_reference
915      operator[](size_type __n) const
916      { return this->_M_impl._M_start[difference_type(__n)]; }
917
918    protected:
919      /// @if maint Safety check used only from at().  @endif
920      void
921      _M_range_check(size_type __n) const
922      {
923	if (__n >= this->size())
924	  __throw_out_of_range(__N("deque::_M_range_check"));
925      }
926
927    public:
928      /**
929       *  @brief  Provides access to the data contained in the %deque.
930       *  @param n The index of the element for which data should be
931       *  accessed.
932       *  @return  Read/write reference to data.
933       *  @throw  std::out_of_range  If @a n is an invalid index.
934       *
935       *  This function provides for safer data access.  The parameter
936       *  is first checked that it is in the range of the deque.  The
937       *  function throws out_of_range if the check fails.
938       */
939      reference
940      at(size_type __n)
941      {
942	_M_range_check(__n);
943	return (*this)[__n];
944      }
945
946      /**
947       *  @brief  Provides access to the data contained in the %deque.
948       *  @param n The index of the element for which data should be
949       *  accessed.
950       *  @return  Read-only (constant) reference to data.
951       *  @throw  std::out_of_range  If @a n is an invalid index.
952       *
953       *  This function provides for safer data access.  The parameter is first
954       *  checked that it is in the range of the deque.  The function throws
955       *  out_of_range if the check fails.
956       */
957      const_reference
958      at(size_type __n) const
959      {
960	_M_range_check(__n);
961	return (*this)[__n];
962      }
963
964      /**
965       *  Returns a read/write reference to the data at the first
966       *  element of the %deque.
967       */
968      reference
969      front()
970      { return *begin(); }
971
972      /**
973       *  Returns a read-only (constant) reference to the data at the first
974       *  element of the %deque.
975       */
976      const_reference
977      front() const
978      { return *begin(); }
979
980      /**
981       *  Returns a read/write reference to the data at the last element of the
982       *  %deque.
983       */
984      reference
985      back()
986      {
987	iterator __tmp = end();
988	--__tmp;
989	return *__tmp;
990      }
991
992      /**
993       *  Returns a read-only (constant) reference to the data at the last
994       *  element of the %deque.
995       */
996      const_reference
997      back() const
998      {
999	const_iterator __tmp = end();
1000	--__tmp;
1001	return *__tmp;
1002      }
1003
1004      // [23.2.1.2] modifiers
1005      /**
1006       *  @brief  Add data to the front of the %deque.
1007       *  @param  x  Data to be added.
1008       *
1009       *  This is a typical stack operation.  The function creates an
1010       *  element at the front of the %deque and assigns the given
1011       *  data to it.  Due to the nature of a %deque this operation
1012       *  can be done in constant time.
1013       */
1014      void
1015      push_front(const value_type& __x)
1016      {
1017	if (this->_M_impl._M_start._M_cur != this->_M_impl._M_start._M_first)
1018	  {
1019	    this->_M_impl.construct(this->_M_impl._M_start._M_cur - 1, __x);
1020	    --this->_M_impl._M_start._M_cur;
1021	  }
1022	else
1023	  _M_push_front_aux(__x);
1024      }
1025
1026      /**
1027       *  @brief  Add data to the end of the %deque.
1028       *  @param  x  Data to be added.
1029       *
1030       *  This is a typical stack operation.  The function creates an
1031       *  element at the end of the %deque and assigns the given data
1032       *  to it.  Due to the nature of a %deque this operation can be
1033       *  done in constant time.
1034       */
1035      void
1036      push_back(const value_type& __x)
1037      {
1038	if (this->_M_impl._M_finish._M_cur
1039	    != this->_M_impl._M_finish._M_last - 1)
1040	  {
1041	    this->_M_impl.construct(this->_M_impl._M_finish._M_cur, __x);
1042	    ++this->_M_impl._M_finish._M_cur;
1043	  }
1044	else
1045	  _M_push_back_aux(__x);
1046      }
1047
1048      /**
1049       *  @brief  Removes first element.
1050       *
1051       *  This is a typical stack operation.  It shrinks the %deque by one.
1052       *
1053       *  Note that no data is returned, and if the first element's data is
1054       *  needed, it should be retrieved before pop_front() is called.
1055       */
1056      void
1057      pop_front()
1058      {
1059	if (this->_M_impl._M_start._M_cur
1060	    != this->_M_impl._M_start._M_last - 1)
1061	  {
1062	    this->_M_impl.destroy(this->_M_impl._M_start._M_cur);
1063	    ++this->_M_impl._M_start._M_cur;
1064	  }
1065	else
1066	  _M_pop_front_aux();
1067      }
1068
1069      /**
1070       *  @brief  Removes last element.
1071       *
1072       *  This is a typical stack operation.  It shrinks the %deque by one.
1073       *
1074       *  Note that no data is returned, and if the last element's data is
1075       *  needed, it should be retrieved before pop_back() is called.
1076       */
1077      void
1078      pop_back()
1079      {
1080	if (this->_M_impl._M_finish._M_cur
1081	    != this->_M_impl._M_finish._M_first)
1082	  {
1083	    --this->_M_impl._M_finish._M_cur;
1084	    this->_M_impl.destroy(this->_M_impl._M_finish._M_cur);
1085	  }
1086	else
1087	  _M_pop_back_aux();
1088      }
1089
1090      /**
1091       *  @brief  Inserts given value into %deque before specified iterator.
1092       *  @param  position  An iterator into the %deque.
1093       *  @param  x  Data to be inserted.
1094       *  @return  An iterator that points to the inserted data.
1095       *
1096       *  This function will insert a copy of the given value before the
1097       *  specified location.
1098       */
1099      iterator
1100      insert(iterator position, const value_type& __x);
1101
1102      /**
1103       *  @brief  Inserts a number of copies of given data into the %deque.
1104       *  @param  position  An iterator into the %deque.
1105       *  @param  n  Number of elements to be inserted.
1106       *  @param  x  Data to be inserted.
1107       *
1108       *  This function will insert a specified number of copies of the given
1109       *  data before the location specified by @a position.
1110       */
1111      void
1112      insert(iterator __position, size_type __n, const value_type& __x)
1113      { _M_fill_insert(__position, __n, __x); }
1114
1115      /**
1116       *  @brief  Inserts a range into the %deque.
1117       *  @param  position  An iterator into the %deque.
1118       *  @param  first  An input iterator.
1119       *  @param  last   An input iterator.
1120       *
1121       *  This function will insert copies of the data in the range
1122       *  [first,last) into the %deque before the location specified
1123       *  by @a pos.  This is known as "range insert."
1124       */
1125      template<typename _InputIterator>
1126        void
1127        insert(iterator __position, _InputIterator __first,
1128	       _InputIterator __last)
1129        {
1130	  // Check whether it's an integral type.  If so, it's not an iterator.
1131	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
1132	  _M_insert_dispatch(__position, __first, __last, _Integral());
1133	}
1134
1135      /**
1136       *  @brief  Remove element at given position.
1137       *  @param  position  Iterator pointing to element to be erased.
1138       *  @return  An iterator pointing to the next element (or end()).
1139       *
1140       *  This function will erase the element at the given position and thus
1141       *  shorten the %deque by one.
1142       *
1143       *  The user is cautioned that
1144       *  this function only erases the element, and that if the element is
1145       *  itself a pointer, the pointed-to memory is not touched in any way.
1146       *  Managing the pointer is the user's responsibilty.
1147       */
1148      iterator
1149      erase(iterator __position);
1150
1151      /**
1152       *  @brief  Remove a range of elements.
1153       *  @param  first  Iterator pointing to the first element to be erased.
1154       *  @param  last  Iterator pointing to one past the last element to be
1155       *                erased.
1156       *  @return  An iterator pointing to the element pointed to by @a last
1157       *           prior to erasing (or end()).
1158       *
1159       *  This function will erase the elements in the range [first,last) and
1160       *  shorten the %deque accordingly.
1161       *
1162       *  The user is cautioned that
1163       *  this function only erases the elements, and that if the elements
1164       *  themselves are pointers, the pointed-to memory is not touched in any
1165       *  way.  Managing the pointer is the user's responsibilty.
1166       */
1167      iterator
1168      erase(iterator __first, iterator __last);
1169
1170      /**
1171       *  @brief  Swaps data with another %deque.
1172       *  @param  x  A %deque of the same element and allocator types.
1173       *
1174       *  This exchanges the elements between two deques in constant time.
1175       *  (Four pointers, so it should be quite fast.)
1176       *  Note that the global std::swap() function is specialized such that
1177       *  std::swap(d1,d2) will feed to this function.
1178       */
1179      void
1180      swap(deque& __x)
1181      {
1182	std::swap(this->_M_impl._M_start, __x._M_impl._M_start);
1183	std::swap(this->_M_impl._M_finish, __x._M_impl._M_finish);
1184	std::swap(this->_M_impl._M_map, __x._M_impl._M_map);
1185	std::swap(this->_M_impl._M_map_size, __x._M_impl._M_map_size);
1186      }
1187
1188      /**
1189       *  Erases all the elements.  Note that this function only erases the
1190       *  elements, and that if the elements themselves are pointers, the
1191       *  pointed-to memory is not touched in any way.  Managing the pointer is
1192       *  the user's responsibilty.
1193       */
1194      void clear();
1195
1196    protected:
1197      // Internal constructor functions follow.
1198
1199      // called by the range constructor to implement [23.1.1]/9
1200      template<typename _Integer>
1201        void
1202        _M_initialize_dispatch(_Integer __n, _Integer __x, __true_type)
1203        {
1204	  _M_initialize_map(__n);
1205	  _M_fill_initialize(__x);
1206	}
1207
1208      // called by the range constructor to implement [23.1.1]/9
1209      template<typename _InputIterator>
1210        void
1211        _M_initialize_dispatch(_InputIterator __first, _InputIterator __last,
1212			       __false_type)
1213        {
1214	  typedef typename std::iterator_traits<_InputIterator>::
1215	    iterator_category _IterCategory;
1216	  _M_range_initialize(__first, __last, _IterCategory());
1217	}
1218
1219      // called by the second initialize_dispatch above
1220      //@{
1221      /**
1222       *  @if maint
1223       *  @brief Fills the deque with whatever is in [first,last).
1224       *  @param  first  An input iterator.
1225       *  @param  last  An input iterator.
1226       *  @return   Nothing.
1227       *
1228       *  If the iterators are actually forward iterators (or better), then the
1229       *  memory layout can be done all at once.  Else we move forward using
1230       *  push_back on each value from the iterator.
1231       *  @endif
1232       */
1233      template<typename _InputIterator>
1234        void
1235        _M_range_initialize(_InputIterator __first, _InputIterator __last,
1236			    std::input_iterator_tag);
1237
1238      // called by the second initialize_dispatch above
1239      template<typename _ForwardIterator>
1240        void
1241        _M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
1242			    std::forward_iterator_tag);
1243      //@}
1244
1245      /**
1246       *  @if maint
1247       *  @brief Fills the %deque with copies of value.
1248       *  @param  value  Initial value.
1249       *  @return   Nothing.
1250       *  @pre _M_start and _M_finish have already been initialized,
1251       *  but none of the %deque's elements have yet been constructed.
1252       *
1253       *  This function is called only when the user provides an explicit size
1254       *  (with or without an explicit exemplar value).
1255       *  @endif
1256       */
1257      void
1258      _M_fill_initialize(const value_type& __value);
1259
1260      // Internal assign functions follow.  The *_aux functions do the actual
1261      // assignment work for the range versions.
1262
1263      // called by the range assign to implement [23.1.1]/9
1264      template<typename _Integer>
1265        void
1266        _M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
1267        {
1268	  _M_fill_assign(static_cast<size_type>(__n),
1269			 static_cast<value_type>(__val));
1270	}
1271
1272      // called by the range assign to implement [23.1.1]/9
1273      template<typename _InputIterator>
1274        void
1275        _M_assign_dispatch(_InputIterator __first, _InputIterator __last,
1276			   __false_type)
1277        {
1278	  typedef typename std::iterator_traits<_InputIterator>::
1279	    iterator_category _IterCategory;
1280	  _M_assign_aux(__first, __last, _IterCategory());
1281	}
1282
1283      // called by the second assign_dispatch above
1284      template<typename _InputIterator>
1285        void
1286        _M_assign_aux(_InputIterator __first, _InputIterator __last,
1287		      std::input_iterator_tag);
1288
1289      // called by the second assign_dispatch above
1290      template<typename _ForwardIterator>
1291        void
1292        _M_assign_aux(_ForwardIterator __first, _ForwardIterator __last,
1293		      std::forward_iterator_tag)
1294        {
1295	  const size_type __len = std::distance(__first, __last);
1296	  if (__len > size())
1297	    {
1298	      _ForwardIterator __mid = __first;
1299	      std::advance(__mid, size());
1300	      std::copy(__first, __mid, begin());
1301	      insert(end(), __mid, __last);
1302	    }
1303	  else
1304	    erase(std::copy(__first, __last, begin()), end());
1305	}
1306
1307      // Called by assign(n,t), and the range assign when it turns out
1308      // to be the same thing.
1309      void
1310      _M_fill_assign(size_type __n, const value_type& __val)
1311      {
1312	if (__n > size())
1313	  {
1314	    std::fill(begin(), end(), __val);
1315	    insert(end(), __n - size(), __val);
1316	  }
1317	else
1318	  {
1319	    erase(begin() + __n, end());
1320	    std::fill(begin(), end(), __val);
1321	  }
1322      }
1323
1324      //@{
1325      /**
1326       *  @if maint
1327       *  @brief Helper functions for push_* and pop_*.
1328       *  @endif
1329       */
1330      void _M_push_back_aux(const value_type&);
1331      void _M_push_front_aux(const value_type&);
1332      void _M_pop_back_aux();
1333      void _M_pop_front_aux();
1334      //@}
1335
1336      // Internal insert functions follow.  The *_aux functions do the actual
1337      // insertion work when all shortcuts fail.
1338
1339      // called by the range insert to implement [23.1.1]/9
1340      template<typename _Integer>
1341        void
1342        _M_insert_dispatch(iterator __pos,
1343			   _Integer __n, _Integer __x, __true_type)
1344        {
1345	  _M_fill_insert(__pos, static_cast<size_type>(__n),
1346			 static_cast<value_type>(__x));
1347	}
1348
1349      // called by the range insert to implement [23.1.1]/9
1350      template<typename _InputIterator>
1351        void
1352        _M_insert_dispatch(iterator __pos,
1353			   _InputIterator __first, _InputIterator __last,
1354			   __false_type)
1355        {
1356	  typedef typename std::iterator_traits<_InputIterator>::
1357	    iterator_category _IterCategory;
1358          _M_range_insert_aux(__pos, __first, __last, _IterCategory());
1359	}
1360
1361      // called by the second insert_dispatch above
1362      template<typename _InputIterator>
1363        void
1364        _M_range_insert_aux(iterator __pos, _InputIterator __first,
1365			    _InputIterator __last, std::input_iterator_tag);
1366
1367      // called by the second insert_dispatch above
1368      template<typename _ForwardIterator>
1369        void
1370        _M_range_insert_aux(iterator __pos, _ForwardIterator __first,
1371			    _ForwardIterator __last, std::forward_iterator_tag);
1372
1373      // Called by insert(p,n,x), and the range insert when it turns out to be
1374      // the same thing.  Can use fill functions in optimal situations,
1375      // otherwise passes off to insert_aux(p,n,x).
1376      void
1377      _M_fill_insert(iterator __pos, size_type __n, const value_type& __x);
1378
1379      // called by insert(p,x)
1380      iterator
1381      _M_insert_aux(iterator __pos, const value_type& __x);
1382
1383      // called by insert(p,n,x) via fill_insert
1384      void
1385      _M_insert_aux(iterator __pos, size_type __n, const value_type& __x);
1386
1387      // called by range_insert_aux for forward iterators
1388      template<typename _ForwardIterator>
1389        void
1390        _M_insert_aux(iterator __pos,
1391		      _ForwardIterator __first, _ForwardIterator __last,
1392		      size_type __n);
1393
1394      //@{
1395      /**
1396       *  @if maint
1397       *  @brief Memory-handling helpers for the previous internal insert
1398       *         functions.
1399       *  @endif
1400       */
1401      iterator
1402      _M_reserve_elements_at_front(size_type __n)
1403      {
1404	const size_type __vacancies = this->_M_impl._M_start._M_cur
1405	                              - this->_M_impl._M_start._M_first;
1406	if (__n > __vacancies)
1407	  _M_new_elements_at_front(__n - __vacancies);
1408	return this->_M_impl._M_start - difference_type(__n);
1409      }
1410
1411      iterator
1412      _M_reserve_elements_at_back(size_type __n)
1413      {
1414	const size_type __vacancies = (this->_M_impl._M_finish._M_last
1415				       - this->_M_impl._M_finish._M_cur) - 1;
1416	if (__n > __vacancies)
1417	  _M_new_elements_at_back(__n - __vacancies);
1418	return this->_M_impl._M_finish + difference_type(__n);
1419      }
1420
1421      void
1422      _M_new_elements_at_front(size_type __new_elements);
1423
1424      void
1425      _M_new_elements_at_back(size_type __new_elements);
1426      //@}
1427
1428
1429      //@{
1430      /**
1431       *  @if maint
1432       *  @brief Memory-handling helpers for the major %map.
1433       *
1434       *  Makes sure the _M_map has space for new nodes.  Does not
1435       *  actually add the nodes.  Can invalidate _M_map pointers.
1436       *  (And consequently, %deque iterators.)
1437       *  @endif
1438       */
1439      void
1440      _M_reserve_map_at_back (size_type __nodes_to_add = 1)
1441      {
1442	if (__nodes_to_add + 1 > this->_M_impl._M_map_size
1443	    - (this->_M_impl._M_finish._M_node - this->_M_impl._M_map))
1444	  _M_reallocate_map(__nodes_to_add, false);
1445      }
1446
1447      void
1448      _M_reserve_map_at_front (size_type __nodes_to_add = 1)
1449      {
1450	if (__nodes_to_add > size_type(this->_M_impl._M_start._M_node
1451				       - this->_M_impl._M_map))
1452	  _M_reallocate_map(__nodes_to_add, true);
1453      }
1454
1455      void
1456      _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front);
1457      //@}
1458    };
1459
1460
1461  /**
1462   *  @brief  Deque equality comparison.
1463   *  @param  x  A %deque.
1464   *  @param  y  A %deque of the same type as @a x.
1465   *  @return  True iff the size and elements of the deques are equal.
1466   *
1467   *  This is an equivalence relation.  It is linear in the size of the
1468   *  deques.  Deques are considered equivalent if their sizes are equal,
1469   *  and if corresponding elements compare equal.
1470  */
1471  template<typename _Tp, typename _Alloc>
1472    inline bool
1473    operator==(const deque<_Tp, _Alloc>& __x,
1474                         const deque<_Tp, _Alloc>& __y)
1475    { return __x.size() == __y.size()
1476             && std::equal(__x.begin(), __x.end(), __y.begin()); }
1477
1478  /**
1479   *  @brief  Deque ordering relation.
1480   *  @param  x  A %deque.
1481   *  @param  y  A %deque of the same type as @a x.
1482   *  @return  True iff @a x is lexicographically less than @a y.
1483   *
1484   *  This is a total ordering relation.  It is linear in the size of the
1485   *  deques.  The elements must be comparable with @c <.
1486   *
1487   *  See std::lexicographical_compare() for how the determination is made.
1488  */
1489  template<typename _Tp, typename _Alloc>
1490    inline bool
1491    operator<(const deque<_Tp, _Alloc>& __x,
1492	      const deque<_Tp, _Alloc>& __y)
1493    { return lexicographical_compare(__x.begin(), __x.end(),
1494				     __y.begin(), __y.end()); }
1495
1496  /// Based on operator==
1497  template<typename _Tp, typename _Alloc>
1498    inline bool
1499    operator!=(const deque<_Tp, _Alloc>& __x,
1500	       const deque<_Tp, _Alloc>& __y)
1501    { return !(__x == __y); }
1502
1503  /// Based on operator<
1504  template<typename _Tp, typename _Alloc>
1505    inline bool
1506    operator>(const deque<_Tp, _Alloc>& __x,
1507	      const deque<_Tp, _Alloc>& __y)
1508    { return __y < __x; }
1509
1510  /// Based on operator<
1511  template<typename _Tp, typename _Alloc>
1512    inline bool
1513    operator<=(const deque<_Tp, _Alloc>& __x,
1514	       const deque<_Tp, _Alloc>& __y)
1515    { return !(__y < __x); }
1516
1517  /// Based on operator<
1518  template<typename _Tp, typename _Alloc>
1519    inline bool
1520    operator>=(const deque<_Tp, _Alloc>& __x,
1521	       const deque<_Tp, _Alloc>& __y)
1522    { return !(__x < __y); }
1523
1524  /// See std::deque::swap().
1525  template<typename _Tp, typename _Alloc>
1526    inline void
1527    swap(deque<_Tp,_Alloc>& __x, deque<_Tp,_Alloc>& __y)
1528    { __x.swap(__y); }
1529} // namespace std
1530
1531#endif /* _DEQUE_H */
1532