C++STL源碼學習（之slist篇）

C++STL源碼學習（之slist篇）

///stl_slist.h

///list為雙向循環鏈表,slist為單向鏈表，某些操作效率更高

///slist是SGI額外提供的單向鏈表,不屬於C++標准

struct _Slist_node_base
{
  _Slist_node_base* _M_next;
};

///將__new_node鏈在__prev_node後面
inline _Slist_node_base*
__slist_make_link(_Slist_node_base* __prev_node,
                  _Slist_node_base* __new_node)
{
  __new_node->_M_next = __prev_node->_M_next;
  __prev_node->_M_next = __new_node;
  return __new_node;
}

///查找__node的前一個結點
inline _Slist_node_base*
__slist_previous(_Slist_node_base* __head,
                 const _Slist_node_base* __node)
{
  while (__head && __head->_M_next != __node)
    __head = __head->_M_next;
  return __head;
}

inline const _Slist_node_base*
__slist_previous(const _Slist_node_base* __head,
                 const _Slist_node_base* __node)
{
  while (__head && __head->_M_next != __node)
    __head = __head->_M_next;
  return __head;
}

///將(__before_first,__before_last]從原位置摘下來,插入到__pos之後
inline void __slist_splice_after(_Slist_node_base* __pos,
                                 _Slist_node_base* __before_first,
                                 _Slist_node_base* __before_last)
{
  if (__pos != __before_first && __pos != __before_last) {
    _Slist_node_base* __first = __before_first->_M_next;
    _Slist_node_base* __after = __pos->_M_next;
    __before_first->_M_next = __before_last->_M_next;
    __pos->_M_next = __first;
    __before_last->_M_next = __after;
  }
}

///將(__head,0)從原位置摘下來,插入__pos之後+
inline void
__slist_splice_after(_Slist_node_base* __pos, _Slist_node_base* __head)
{
  _Slist_node_base* __before_last = __slist_previous(__head, 0);-
  if (__before_last != __head) {
    _Slist_node_base* __after = __pos->_M_next;
    __pos->_M_next = __head->_M_next;
    __head->_M_next = 0;
    __before_last->_M_next = __after;
  }
}

///從node開始,將整個鏈表翻轉
inline _Slist_node_base* __slist_reverse(_Slist_node_base* __node)
{
  _Slist_node_base* __result = __node;
  __node = __node->_M_next;
  __result->_M_next = 0;
  while(__node) {
    _Slist_node_base* __next = __node->_M_next;
    __node->_M_next = __result;   ///將_M_next指向其前一個結點
    __result = __node;
    __node = __next;
  }
  return __result;
}

///計算[__node,0)的節點數
inline size_t __slist_size(_Slist_node_base* __node)
{
  size_t __result = 0;
  for ( ; __node != 0; __node = __node->_M_next)
    ++__result;
  return __result;
}

template 
struct _Slist_node : public _Slist_node_base
{
  _Tp _M_data;
};

struct _Slist_iterator_base
{
  typedef size_t               size_type;
  typedef ptrdiff_t            difference_type;
  typedef forward_iterator_tag iterator_category;   ///前向迭代器

  _Slist_node_base* _M_node;

  _Slist_iterator_base(_Slist_node_base* __x) : _M_node(__x) {}
  void _M_incr() { _M_node = _M_node->_M_next; }

  bool operator==(const _Slist_iterator_base& __x) const {
    return _M_node == __x._M_node;
  }
  bool operator!=(const _Slist_iterator_base& __x) const {
    return _M_node != __x._M_node;
  }
};

template 
struct _Slist_iterator : public _Slist_iterator_base
{
  typedef _Slist_iterator<_Tp, _Tp&, _Tp*>             iterator;
  typedef _Slist_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;
  typedef _Slist_iterator<_Tp, _Ref, _Ptr>             _Self;

  typedef _Tp              value_type;
  typedef _Ptr             pointer;
  typedef _Ref             reference;
  typedef _Slist_node<_Tp> _Node;

  _Slist_iterator(_Node* __x) : _Slist_iterator_base(__x) {}
  _Slist_iterator() : _Slist_iterator_base(0) {}
  _Slist_iterator(const iterator& __x) : _Slist_iterator_base(__x._M_node) {}

  reference operator*() const { return ((_Node*) _M_node)->_M_data; }
  pointer operator->() const { return &(operator*()); }

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

inline ptrdiff_t* distance_type(const _Slist_iterator_base&) {
  return 0;
}

inline forward_iterator_tag iterator_category(const _Slist_iterator_base&) {
  return forward_iterator_tag();
}

template 
inline _Tp* value_type(const _Slist_iterator<_Tp, _Ref, _Ptr>&) {
  return 0;
}

template 
struct _Slist_base {
  typedef _Alloc allocator_type;
  allocator_type get_allocator() const { return allocator_type(); }

  _Slist_base(const allocator_type&) { _M_head._M_next = 0; }
  ~_Slist_base() { _M_erase_after(&_M_head, 0); }  ///清空鏈表

protected:
  typedef simple_alloc<_Slist_node<_Tp>, _Alloc> _Alloc_type;

  _Slist_node<_Tp>* _M_get_node() { return _Alloc_type::allocate(1); }
  void _M_put_node(_Slist_node<_Tp>* __p) { _Alloc_type::deallocate(__p, 1); }

  ///刪除__pos->_M_next
  _Slist_node_base* _M_erase_after(_Slist_node_base* __pos)
  {
    _Slist_node<_Tp>* __next = (_Slist_node<_Tp>*) (__pos->_M_next);
    _Slist_node_base* __next_next = __next->_M_next;
    __pos->_M_next = __next_next;
    destroy(&__next->_M_data);
    _M_put_node(__next);
    return __next_next;
  }

  _Slist_node_base* _M_erase_after(_Slist_node_base*, _Slist_node_base*);

protected:
  _Slist_node_base _M_head;  ///不存儲任何數據元素的頭結點
};

///刪除(__before_first,__last_node)
template 
_Slist_node_base*
_Slist_base<_Tp,_Alloc>::_M_erase_after(_Slist_node_base* __before_first,
                                        _Slist_node_base* __last_node) {
  _Slist_node<_Tp>* __cur = (_Slist_node<_Tp>*) (__before_first->_M_next);
  while (__cur != __last_node) {
    _Slist_node<_Tp>* __tmp = __cur;
    __cur = (_Slist_node<_Tp>*) __cur->_M_next;
    destroy(&__tmp->_M_data);
    _M_put_node(__tmp);
  }
  __before_first->_M_next = __last_node;
  return __last_node;
}

template 
class slist : private _Slist_base<_Tp,_Alloc>
{
  __STL_CLASS_REQUIRES(_Tp, _Assignable);

private:
  typedef _Slist_base<_Tp,_Alloc> _Base;
public:
  typedef _Tp                value_type;
  typedef value_type*       pointer;
  typedef const value_type* const_pointer;
  typedef value_type&       reference;
  typedef const value_type& const_reference;
  typedef size_t            size_type;
  typedef ptrdiff_t         difference_type;

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

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

private:
  typedef _Slist_node<_Tp>      _Node;
  typedef _Slist_node_base      _Node_base;
  typedef _Slist_iterator_base  _Iterator_base;

    ///構造一個數據元素為x的結點
  _Node* _M_create_node(const value_type& __x) {
    _Node* __node = this->_M_get_node();
    try {
      construct(&__node->_M_data, __x);
      __node->_M_next = 0;
    }catch(...){
        this->_M_put_node(__node);
    }

    return __node;
  }

  _Node* _M_create_node() {
    _Node* __node = this->_M_get_node();
    try {
      construct(&__node->_M_data);
      __node->_M_next = 0;
    }catch(...){
        this->_M_put_node(__node);
    }

    return __node;
  }

public:
  explicit slist(const allocator_type& __a = allocator_type()) : _Base(__a) {}

  slist(size_type __n, const value_type& __x,
        const allocator_type& __a =  allocator_type()) : _Base(__a)
    { _M_insert_after_fill(&this->_M_head, __n, __x); }

  explicit slist(size_type __n) : _Base(allocator_type())
    { _M_insert_after_fill(&this->_M_head, __n, value_type()); }


  /// We don't need any dispatching tricks here, because _M_insert_after_range
  /// already does them.
  template 
  slist(_InputIterator __first, _InputIterator __last,
        const allocator_type& __a =  allocator_type()) : _Base(__a)
    { _M_insert_after_range(&this->_M_head, __first, __last); }


  slist(const slist& __x) : _Base(__x.get_allocator())
    { _M_insert_after_range(&this->_M_head, __x.begin(), __x.end()); }

  slist& operator= (const slist& __x);

  ~slist() {}    ///善後留給基類析構函數

public:

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

  void _M_fill_assign(size_type __n, const _Tp& __val);

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

  template 
  void _M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
    { _M_fill_assign((size_type) __n, (_Tp) __val); }

  template 
  void _M_assign_dispatch(_InputIterator __first, _InputIterator __last,
                          __false_type);

public:

  iterator begin() { return iterator((_Node*)this->_M_head._M_next); }
  const_iterator begin() const
    { return const_iterator((_Node*)this->_M_head._M_next);}

  iterator end() { return iterator(0); }
  const_iterator end() const { return const_iterator(0); }

  /// Experimental new feature: before_begin() returns a
  /// non-dereferenceable iterator that, when incremented, yields
  /// begin().  This iterator may be used as the argument to
  /// insert_after, erase_after, etc.  Note that even for an empty
  /// slist, before_begin() is not the same iterator as end().  It
  /// is always necessary to increment before_begin() at least once to
  /// obtain end().
  iterator before_begin() { return iterator((_Node*) &this->_M_head); }
  const_iterator before_begin() const
    { return const_iterator((_Node*) &this->_M_head); }

  size_type size() const { return __slist_size(this->_M_head._M_next); }

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

  bool empty() const { return this->_M_head._M_next == 0; }

  ///交換指針完成
  void swap(slist& __x)
    { __STD::swap(this->_M_head._M_next, __x._M_head._M_next); }

public:

  reference front() { return ((_Node*) this->_M_head._M_next)->_M_data; }
  const_reference front() const
    { return ((_Node*) this->_M_head._M_next)->_M_data; }

  void push_front(const value_type& __x)   {
    __slist_make_link(&this->_M_head, _M_create_node(__x));
  }
  void push_front() { __slist_make_link(&this->_M_head, _M_create_node()); }

  void pop_front() {
    _Node* __node = (_Node*) this->_M_head._M_next;
    this->_M_head._M_next = __node->_M_next;
    destroy(&__node->_M_data);
    this->_M_put_node(__node);
  }

  iterator previous(const_iterator __pos) {
    return iterator((_Node*) __slist_previous(&this->_M_head, __pos._M_node));
  }
  const_iterator previous(const_iterator __pos) const {
    return const_iterator((_Node*) __slist_previous(&this->_M_head,
                                                    __pos._M_node));
  }

private:
  _Node* _M_insert_after(_Node_base* __pos, const value_type& __x) {
    return (_Node*) (__slist_make_link(__pos, _M_create_node(__x)));
  }

  _Node* _M_insert_after(_Node_base* __pos) {
    return (_Node*) (__slist_make_link(__pos, _M_create_node()));
  }

  ///在__pos之後插入__n個數據值為__x的結點
  void _M_insert_after_fill(_Node_base* __pos,
                            size_type __n, const value_type& __x) {
    for (size_type __i = 0; __i < __n; ++__i)
      __pos = __slist_make_link(__pos, _M_create_node(__x));
  }



  /// Check whether it's an integral type.  If so, it's not an iterator.
  template 
  void _M_insert_after_range(_Node_base* __pos,
                             _InIter __first, _InIter __last) {
    typedef typename _Is_integer<_InIter>::_Integral _Integral;
    _M_insert_after_range(__pos, __first, __last, _Integral());
  }

  template 
  void _M_insert_after_range(_Node_base* __pos, _Integer __n, _Integer __x,
                             __true_type) {
    _M_insert_after_fill(__pos, __n, __x);
}

  ///在__pos之後插入[__first,__last)之間的值
  template 
  void _M_insert_after_range(_Node_base* __pos,
                             _InIter __first, _InIter __last,
                             __false_type) {
    while (__first != __last) {
      __pos = __slist_make_link(__pos, _M_create_node(*__first));
      ++__first;
    }
}

public:

  iterator insert_after(iterator __pos, const value_type& __x) {
    return iterator(_M_insert_after(__pos._M_node, __x));
  }

  iterator insert_after(iterator __pos) {
    return insert_after(__pos, value_type());
  }

  void insert_after(iterator __pos, size_type __n, const value_type& __x) {
    _M_insert_after_fill(__pos._M_node, __n, __x);
  }

  /// We don't need any dispatching tricks here, because _M_insert_after_range
  /// already does them.
  template 
  void insert_after(iterator __pos, _InIter __first, _InIter __last) {
    _M_insert_after_range(__pos._M_node, __first, __last);
  }
     ///由於slist是單向鏈表,因此多采用insert_after來實現插入
     ///提供的insert函數也實現找到插入位置的前驅結點,然後調用insert_after來實現的
  iterator insert(iterator __pos, const value_type& __x) {
    return iterator(_M_insert_after(__slist_previous(&this->_M_head,
                                                     __pos._M_node),
                    __x));
  }

  iterator insert(iterator __pos) {
    return iterator(_M_insert_after(__slist_previous(&this->_M_head,
                                                     __pos._M_node),
                                    value_type()));
  }

  void insert(iterator __pos, size_type __n, const value_type& __x) {
    _M_insert_after_fill(__slist_previous(&this->_M_head, __pos._M_node),
                         __n, __x);
  }

  /// We don't need any dispatching tricks here, because _M_insert_after_range
  /// already does them.
  template 
  void insert(iterator __pos, _InIter __first, _InIter __last) {
    _M_insert_after_range(__slist_previous(&this->_M_head, __pos._M_node),
                          __first, __last);
  }

public:
  iterator erase_after(iterator __pos) {
    return iterator((_Node*) this->_M_erase_after(__pos._M_node));
  }
  iterator erase_after(iterator __before_first, iterator __last) {
    return iterator((_Node*) this->_M_erase_after(__before_first._M_node,
                                                  __last._M_node));
  }

  ///由於slist是單向鏈表,因此多采用erase_after來實現刪除
 ///提供的erase函數也實現找到刪除位置的前驅結點,然後調用erase_after來實現的
  iterator erase(iterator __pos) {
    return (_Node*) this->_M_erase_after(__slist_previous(&this->_M_head,
                                                          __pos._M_node));
  }
  iterator erase(iterator __first, iterator __last) {
    return (_Node*) this->_M_erase_after(
      __slist_previous(&this->_M_head, __first._M_node), __last._M_node);
  }

  void resize(size_type new_size, const _Tp& __x);
  void resize(size_type new_size) { resize(new_size, _Tp()); }
  void clear() { this->_M_erase_after(&this->_M_head, 0); }

public:
  /// Moves the range (__before_first, __before_last ] to *this,
  ///  inserting it immediately after __pos.  This is constant time.
  void splice_after(iterator __pos,
                    iterator __before_first, iterator __before_last)
  {
    if (__before_first != __before_last)
      __slist_splice_after(__pos._M_node, __before_first._M_node,
                           __before_last._M_node);
  }

  /// Moves the element that follows __prev to *this, inserting it immediately
  ///  after __pos.  This is constant time.
  void splice_after(iterator __pos, iterator __prev)
  {
    __slist_splice_after(__pos._M_node,
                         __prev._M_node, __prev._M_node->_M_next);
  }


  /// Removes all of the elements from the list __x to *this, inserting
  /// them immediately after __pos.  __x must not be *this.  Complexity:
  /// linear in __x.size().
  void splice_after(iterator __pos, slist& __x)
  {
    __slist_splice_after(__pos._M_node, &__x._M_head);
  }

  /// Linear in distance(begin(), __pos), and linear in __x.size().
  void splice(iterator __pos, slist& __x) {
    if (__x._M_head._M_next)
      __slist_splice_after(__slist_previous(&this->_M_head, __pos._M_node),
                           &__x._M_head, __slist_previous(&__x._M_head, 0));
  }

  /// Linear in distance(begin(), __pos), and in distance(__x.begin(), __i).
  void splice(iterator __pos, slist& __x, iterator __i) {
    __slist_splice_after(__slist_previous(&this->_M_head, __pos._M_node),
                         __slist_previous(&__x._M_head, __i._M_node),
                         __i._M_node);
  }

  /// Linear in distance(begin(), __pos), in distance(__x.begin(), __first),
  /// and in distance(__first, __last).
  void splice(iterator __pos, slist& __x, iterator __first, iterator __last)
  {
    if (__first != __last)
      __slist_splice_after(__slist_previous(&this->_M_head, __pos._M_node),
                           __slist_previous(&__x._M_head, __first._M_node),
                           __slist_previous(__first._M_node, __last._M_node));
  }

public:
  void reverse() {
    if (this->_M_head._M_next)
      this->_M_head._M_next = __slist_reverse(this->_M_head._M_next);
  }

  void remove(const _Tp& __val);
  void unique();
  void merge(slist& __x);
  void sort();

  template 
  void remove_if(_Predicate __pred);

  template 
  void unique(_BinaryPredicate __pred);

  template 
  void merge(slist&, _StrictWeakOrdering);

  template 
  void sort(_StrictWeakOrdering __comp);

};

template 
slist<_Tp,_Alloc>& slist<_Tp,_Alloc>::operator=(const slist<_Tp,_Alloc>& __x)
{
  if (&__x != this) {

    _Node_base* __p1 = &this->_M_head;
    _Node* __n1 = (_Node*) this->_M_head._M_next;
    const _Node* __n2 = (const _Node*) __x._M_head._M_next;

    while (__n1 && __n2) {
      __n1->_M_data = __n2->_M_data;
      __p1 = __n1;      ///賦值過程中記錄前一個節點指針,方便後面的處理
      __n1 = (_Node*) __n1->_M_next;
      __n2 = (const _Node*) __n2->_M_next;
    }

    if (__n2 == 0)
      this->_M_erase_after(__p1, 0);
    else
      _M_insert_after_range(__p1, const_iterator((_Node*)__n2),
                                  const_iterator(0));
  }
  return *this;
}

template 
void slist<_Tp, _Alloc>::_M_fill_assign(size_type __n, const _Tp& __val) {

  _Node_base* __prev = &this->_M_head;
  _Node* __node = (_Node*) this->_M_head._M_next;

  for ( ; __node != 0 && __n > 0 ; --__n) {
    __node->_M_data = __val;
    __prev = __node;
    __node = (_Node*) __node->_M_next;
  }

  if (__n > 0)
    _M_insert_after_fill(__prev, __n, __val);
  else
    this->_M_erase_after(__prev, 0);
}


template  template 
void
slist<_Tp, _Alloc>::_M_assign_dispatch(_InputIter __first, _InputIter __last,
                                       __false_type)
{
  _Node_base* __prev = &this->_M_head;
  _Node* __node = (_Node*) this->_M_head._M_next;

  while (__node != 0 && __first != __last) {
    __node->_M_data = *__first;
    __prev = __node;
    __node = (_Node*) __node->_M_next;
    ++__first;
  }

  if (__first != __last)
    _M_insert_after_range(__prev, __first, __last);
  else
    this->_M_erase_after(__prev, 0);
}

template 
inline bool
operator==(const slist<_Tp,_Alloc>& _SL1, const slist<_Tp,_Alloc>& _SL2)
{
  typedef typename slist<_Tp,_Alloc>::const_iterator const_iterator;
  const_iterator __end1 = _SL1.end();
  const_iterator __end2 = _SL2.end();

  const_iterator __i1 = _SL1.begin();
  const_iterator __i2 = _SL2.begin();
  while (__i1 != __end1 && __i2 != __end2 && *__i1 == *__i2) {
    ++__i1;
    ++__i2;
  }

  return __i1 == __end1 && __i2 == __end2;
}


template 
inline bool
operator<(const slist<_Tp,_Alloc>& _SL1, const slist<_Tp,_Alloc>& _SL2)
{
  return lexicographical_compare(_SL1.begin(), _SL1.end(),
                                 _SL2.begin(), _SL2.end());
}

template 
void slist<_Tp,_Alloc>::resize(size_type __len, const _Tp& __x)
{
  _Node_base* __cur = &this->_M_head;
  while (__cur->_M_next != 0 && __len > 0) {
    --__len;
    __cur = __cur->_M_next;
  }
  if (__cur->_M_next)
    this->_M_erase_after(__cur, 0);
  else
    _M_insert_after_fill(__cur, __len, __x);
}

template 
void slist<_Tp,_Alloc>::remove(const _Tp& __val)
{
  _Node_base* __cur = &this->_M_head;
  while (__cur && __cur->_M_next) {

    if (((_Node*) __cur->_M_next)->_M_data == __val)   ///比較下一個結點的值和val是否相等
      this->_M_erase_after(__cur);
    else
      __cur = __cur->_M_next;
  }
}

template 
void slist<_Tp,_Alloc>::unique()
{
  _Node_base* __cur = this->_M_head._M_next;
  if (__cur) {
    while (__cur->_M_next) {

      if (((_Node*)__cur)->_M_data == ((_Node*)(__cur->_M_next))->_M_data)
        this->_M_erase_after(__cur);
      else
        __cur = __cur->_M_next;
    }
  }
}

template 
void slist<_Tp,_Alloc>::merge(slist<_Tp,_Alloc>& __x)
{
  _Node_base* __n1 = &this->_M_head;
  while (__n1->_M_next && __x._M_head._M_next) {

    if (((_Node*) __x._M_head._M_next)->_M_data <
        ((_Node*)       __n1->_M_next)->_M_data)

      __slist_splice_after(__n1, &__x._M_head, __x._M_head._M_next);
    __n1 = __n1->_M_next;
  }

  if (__x._M_head._M_next) {
    __n1->_M_next = __x._M_head._M_next;
    __x._M_head._M_next = 0;
  }
}

///和list采用相同的算法
template 
void slist<_Tp,_Alloc>::sort()
{
  if (this->_M_head._M_next && this->_M_head._M_next->_M_next) {
    slist __carry;
    slist __counter[64];
    int __fill = 0;
    while (!empty()) {
      __slist_splice_after(&__carry._M_head,
                           &this->_M_head, this->_M_head._M_next);
      int __i = 0;
      while (__i < __fill && !__counter[__i].empty()) {
        __counter[__i].merge(__carry);
        __carry.swap(__counter[__i]);
        ++__i;
      }
      __carry.swap(__counter[__i]);
      if (__i == __fill)
        ++__fill;
    }

    for (int __i = 1; __i < __fill; ++__i)
      __counter[__i].merge(__counter[__i-1]);
    this->swap(__counter[__fill-1]);
  }
}


template 
template 
void slist<_Tp,_Alloc>::remove_if(_Predicate __pred)
{
  _Node_base* __cur = &this->_M_head;
  while (__cur->_M_next) {
    if (__pred(((_Node*) __cur->_M_next)->_M_data))
      this->_M_erase_after(__cur);
    else
      __cur = __cur->_M_next;
  }
}

template  template 
void slist<_Tp,_Alloc>::unique(_BinaryPredicate __pred)
{
  _Node* __cur = (_Node*) this->_M_head._M_next;
  if (__cur) {
    while (__cur->_M_next) {
      if (__pred(((_Node*)__cur)->_M_data,
                 ((_Node*)(__cur->_M_next))->_M_data))
        this->_M_erase_after(__cur);
      else
        __cur = (_Node*) __cur->_M_next;
    }
  }
}

template  template 
void slist<_Tp,_Alloc>::merge(slist<_Tp,_Alloc>& __x,
                              _StrictWeakOrdering __comp)
{
  _Node_base* __n1 = &this->_M_head;
  while (__n1->_M_next && __x._M_head._M_next) {
    if (__comp(((_Node*) __x._M_head._M_next)->_M_data,
               ((_Node*)       __n1->_M_next)->_M_data))
      __slist_splice_after(__n1, &__x._M_head, __x._M_head._M_next);
    __n1 = __n1->_M_next;
  }
  if (__x._M_head._M_next) {
    __n1->_M_next = __x._M_head._M_next;
    __x._M_head._M_next = 0;
  }
}

template  template 
void slist<_Tp,_Alloc>::sort(_StrictWeakOrdering __comp)
{
  if (this->_M_head._M_next && this->_M_head._M_next->_M_next) {
    slist __carry;
    slist __counter[64];
    int __fill = 0;
    while (!empty()) {
      __slist_splice_after(&__carry._M_head,
                           &this->_M_head, this->_M_head._M_next);
      int __i = 0;
      while (__i < __fill && !__counter[__i].empty()) {
        __counter[__i].merge(__carry, __comp);
        __carry.swap(__counter[__i]);
        ++__i;
      }
      __carry.swap(__counter[__i]);
      if (__i == __fill)
        ++__fill;
    }

    for (int __i = 1; __i < __fill; ++__i)
      __counter[__i].merge(__counter[__i-1], __comp);
    this->swap(__counter[__fill-1]);
  }
}