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STL学习（自学手册+源码分析）之deque、queue、stack

程序员文章站 2022-03-31 10:21:51
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1.1 deque

1.1.1 deque的主体实现

其实现结构图：
在内存中实现的形式是分段串接的形式。（分段连续）STL学习（自学手册+源码分析）之deque、queue、stack
其中的map是一个T**(vector)实现,其中包含了指向各个内存块buffer的指针，若deque需要扩充内存的话，则使map中前面或后面的指针指向这块内存即可。

源码实现：
STL学习（自学手册+源码分析）之deque、queue、stack
PS:我这里找的和ppt上的不一样，但是基本能看…

template <class _Tp, class _Alloc>
class _Deque_base
  : public _Deque_alloc_base<_Tp,_Alloc,
                              _Alloc_traits<_Tp, _Alloc>::_S_instanceless>
{
public:
  typedef _Deque_alloc_base<_Tp,_Alloc,
                             _Alloc_traits<_Tp, _Alloc>::_S_instanceless>
          _Base;
  typedef typename _Base::allocator_type allocator_type;
  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)
    : _Base(__a), _M_start(), _M_finish()
    { _M_initialize_map(__num_elements); }
  _Deque_base(const allocator_type& __a) 
    : _Base(__a), _M_start(), _M_finish() {}
  ~_Deque_base();    

protected:
  void _M_initialize_map(size_t);//中控中心map 是一个二级指针
  void _M_create_nodes(_Tp** __nstart, _Tp** __nfinish);
  void _M_destroy_nodes(_Tp** __nstart, _Tp** __nfinish);
  enum { _S_initial_map_size = 8 };

protected:
  iterator _M_start;//图中start 迭代器
  iterator _M_finish;//图中 finish 迭代器
};

template <class _Tp, class _Alloc = __STL_DEFAULT_ALLOCATOR(_Tp) >
class deque : protected _Deque_base<_Tp, _Alloc> {

  // requirements:

  __STL_CLASS_REQUIRES(_Tp, _Assignable);

  typedef _Deque_base<_Tp, _Alloc> _Base;
public:                         // Basic types
  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 typename _Base::allocator_type allocator_type;
  allocator_type get_allocator() const { return _Base::get_allocator(); }

public:                         // Iterators
  typedef typename _Base::iterator       iterator;
  typedef typename _Base::const_iterator const_iterator;

protected:                      // Internal typedefs
  typedef pointer* _Map_pointer;
  static size_t _S_buffer_size() { return __deque_buf_size(sizeof(_Tp)); }
  
public:                         // Basic accessors
  iterator begin() { return _M_start; }
  iterator end() { return _M_finish; }
  const_iterator begin() const { return _M_start; }
  const_iterator end() const { return _M_finish; }

  reverse_iterator rbegin() { return reverse_iterator(_M_finish); }
  reverse_iterator rend() { return reverse_iterator(_M_start); }
  const_reverse_iterator rbegin() const 
    { return const_reverse_iterator(_M_finish); }
  const_reverse_iterator rend() const 
    { return const_reverse_iterator(_M_start); }

  reference operator[](size_type __n)
    { return _M_start[difference_type(__n)]; }
  const_reference operator[](size_type __n) const 
    { return _M_start[difference_type(__n)]; }
    ....省略

1.1.2 deque iterator

STL学习（自学手册+源码分析）之deque、queue、stack
源码：

template <class _Tp, class _Ref, class _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 random_access_iterator_tag iterator_category;//（1）随机访问迭代器
  typedef _Tp value_type;//（2）
  typedef _Ptr pointer;//（3）
  typedef _Ref reference;//（4）
  typedef size_t size_type;
  typedef ptrdiff_t difference_type;//（5）
  typedef _Tp** _Map_pointer;

  typedef _Deque_iterator _Self;

  _Tp* _M_cur;//指向当前位置
  _Tp* _M_first;//指向本段最开始
  _Tp* _M_last;//指向本段最末尾
  _Map_pointer _M_node;//指向控制中心

  _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; }
#ifndef __SGI_STL_NO_ARROW_OPERATOR
  pointer operator->() const { return _M_cur; }
#endif /* __SGI_STL_NO_ARROW_OPERATOR */

  difference_type operator-(const _Self& __x) const {
    return difference_type(_S_buffer_size()) * (_M_node - __x._M_node - 1) +
      (_M_cur - _M_first) + (__x._M_last - __x._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)
  {
    difference_type __offset = __n + (_M_cur - _M_first);
    //目标位置在同一缓冲区内
    if (__offset >= 0 && __offset < difference_type(_S_buffer_size()))
      _M_cur += __n;
      //不在同一缓冲区内
    else {
      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); }

  bool operator==(const _Self& __x) const { return _M_cur == __x._M_cur; }
  bool operator!=(const _Self& __x) const { return !(*this == __x); }
  bool operator<(const _Self& __x) const {
    return (_M_node == __x._M_node) ? 
      (_M_cur < __x._M_cur) : (_M_node < __x._M_node);
  }
  bool operator>(const _Self& __x) const  { return __x < *this; }
  bool operator<=(const _Self& __x) const { return !(__x < *this); }
  bool operator>=(const _Self& __x) const { return !(*this < __x); }

  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());
  }
};

所以deque的连续空间的“假象”，都是利用deque的iterator实现出来的。

1.2 queue（队列）

template <class _Tp, 
          class _Sequence = deque<_Tp> >

template <class _Tp, class _Sequence>
class queue {

  // requirements:

  __STL_CLASS_REQUIRES(_Tp, _Assignable);
  __STL_CLASS_REQUIRES(_Sequence, _FrontInsertionSequence);
  __STL_CLASS_REQUIRES(_Sequence, _BackInsertionSequence);
  typedef typename _Sequence::value_type _Sequence_value_type;
  __STL_CLASS_REQUIRES_SAME_TYPE(_Tp, _Sequence_value_type);


#ifdef __STL_MEMBER_TEMPLATES 
  template <class _Tp1, class _Seq1>
  friend bool operator== (const queue<_Tp1, _Seq1>&,
                          const queue<_Tp1, _Seq1>&);
  template <class _Tp1, class _Seq1>
  friend bool operator< (const queue<_Tp1, _Seq1>&,
                         const queue<_Tp1, _Seq1>&);
#else /* __STL_MEMBER_TEMPLATES */
  friend bool __STD_QUALIFIER
  operator== __STL_NULL_TMPL_ARGS (const queue&, const queue&);
  friend bool __STD_QUALIFIER
  operator<  __STL_NULL_TMPL_ARGS (const queue&, const queue&);
#endif /* __STL_MEMBER_TEMPLATES */

public:
  typedef typename _Sequence::value_type      value_type;
  typedef typename _Sequence::size_type       size_type;
  typedef          _Sequence                  container_type;

  typedef typename _Sequence::reference       reference;
  typedef typename _Sequence::const_reference const_reference;
protected:
  _Sequence c;
public:
  queue() : c() {}
  explicit queue(const _Sequence& __c) : c(__c) {}

  bool empty() const { return c.empty(); }
  size_type size() const { return c.size(); }
  reference front() { return c.front(); }
  const_reference front() const { return c.front(); }
  reference back() { return c.back(); }
  const_reference back() const { return c.back(); }
  void push(const value_type& __x) { c.push_back(__x); }
  void pop() { c.pop_front(); }
};

这里的_Sequence即deque，所以queue的底层实现用的是deque。

1.3 stack（栈）

template <class _Tp, 
          class _Sequence = deque<_Tp> >

template <class _Tp, class _Sequence>
class stack {

  // requirements:

  __STL_CLASS_REQUIRES(_Tp, _Assignable);
  __STL_CLASS_REQUIRES(_Sequence, _BackInsertionSequence);
  typedef typename _Sequence::value_type _Sequence_value_type;
  __STL_CLASS_REQUIRES_SAME_TYPE(_Tp, _Sequence_value_type);


#ifdef __STL_MEMBER_TEMPLATES
  template <class _Tp1, class _Seq1>
  friend bool operator== (const stack<_Tp1, _Seq1>&,
                          const stack<_Tp1, _Seq1>&);
  template <class _Tp1, class _Seq1>
  friend bool operator< (const stack<_Tp1, _Seq1>&,
                         const stack<_Tp1, _Seq1>&);
#else /* __STL_MEMBER_TEMPLATES */
  friend bool __STD_QUALIFIER
  operator== __STL_NULL_TMPL_ARGS (const stack&, const stack&);
  friend bool __STD_QUALIFIER
  operator< __STL_NULL_TMPL_ARGS (const stack&, const stack&);
#endif /* __STL_MEMBER_TEMPLATES */

public:
  typedef typename _Sequence::value_type      value_type;
  typedef typename _Sequence::size_type       size_type;
  typedef          _Sequence                  container_type;

  typedef typename _Sequence::reference       reference;
  typedef typename _Sequence::const_reference const_reference;
protected:
  _Sequence c;
public:
  stack() : c() {}
  explicit stack(const _Sequence& __s) : c(__s) {}

  bool empty() const { return c.empty(); }
  size_type size() const { return c.size(); }
  reference top() { return c.back(); }
  const_reference top() const { return c.back(); }
  void push(const value_type& __x) { c.push_back(__x); }
  void pop() { c.pop_back(); }
};

这里的_Sequence即deque，所以stack的底层实现用的是deque。

相关标签： STL源码剖析

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