STL源码剖析 - 第5章 关联式容器 - multimap

5.6 multimap

        multimap的特性及其用法和map完全相同，唯一的区别就是multimap允许键值key重复，因此multimap的插入操作采用的是底层RB-Tree的insert_equal()而非insert_unique()。本文的源码出自SGISTL中的<stl_multimap.h>文件。

#ifndef __SGI_STL_INTERNAL_MULTIMAP_H#define __SGI_STL_INTERNAL_MULTIMAP_H #include <concept_checks.h> __STL_BEGIN_NAMESPACE #if defined(__sgi) &&!defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)#pragma set woff 1174#pragma set woff 1375#endif // Forward declaration of operators <and ==, needed for friend declaration. //multimap的特性及其用法和map完全相同，唯一的区别就是multimap允许键值key重复//因此multimap的插入操作采用的是底层RB-Tree的insert_equal()而非insert_unique()//有关map容器的剖析见前面博文//map内部元素根据键值key默认使用递增排序less//用户可自行制定比较类型//内部维护的数据结构是红黑树, 具有非常优秀的最坏情况的时间复杂度//注意:multimap允许元素重复,即键值和实值都可以重复,这点与map不同template <class _Key, class _Tp,         class _Compare __STL_DEPENDENT_DEFAULT_TMPL(less<_Key>),         class _Alloc = __STL_DEFAULT_ALLOCATOR(_Tp) >class multimap; template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator==(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                       constmultimap<_Key,_Tp,_Compare,_Alloc>& __y); template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator<(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                      constmultimap<_Key,_Tp,_Compare,_Alloc>& __y); template <class _Key, class _Tp, class_Compare, class _Alloc>class multimap {  //requirements:  __STL_CLASS_REQUIRES(_Tp, _Assignable); __STL_CLASS_BINARY_FUNCTION_CHECK(_Compare, bool, _Key, _Key); public: // typedefs:   //下面的定义与map相同 typedef _Key                 key_type; typedef _Tp                  data_type; typedef _Tp                  mapped_type; typedef pair<const _Key, _Tp> value_type; typedef _Compare             key_compare;    //嵌套类,提供键值key比较函数接口  //继承自<stl_function.h>中的binary_function  /*         template<class _Arg1, class _Arg2, class _Result>         structbinary_function {                   typedef_Arg1 first_argument_type;                   typedef_Arg2 second_argument_type;                   typedef_Result result_type;         };  */ class value_compare : public binary_function<value_type, value_type,bool> { friend class multimap<_Key,_Tp,_Compare,_Alloc>; protected:   _Compare comp;   value_compare(_Compare __c) : comp(__c) {} public:   bool operator()(const value_type& __x, const value_type& __y)const {     return comp(__x.first, __y.first);    }  }; private:         //底层机制是RB-Tree typedef _Rb_tree<key_type, value_type,                  _Select1st<value_type>,key_compare, _Alloc> _Rep_type; _Rep_type _M_t;  // red-black treerepresenting multimappublic: typedef typename _Rep_type::pointer pointer; typedef typename _Rep_type::const_pointer const_pointer; typedef typename _Rep_type::reference reference; typedef typename _Rep_type::const_reference const_reference; //map的迭代器不直接定义为const_iterator,而是分别定义iterator,const_iterator  //是因为map的键值key不能被修改,因为必须遵守比较函数的排序规则,所以必须定义为const_iterator  //而map的实值value可以被修改,则定义为iterator typedef typename _Rep_type::iterator iterator; typedef typename _Rep_type::const_iterator const_iterator; typedef typename _Rep_type::reverse_iterator reverse_iterator; typedef typename _Rep_type::const_reverse_iteratorconst_reverse_iterator; typedef typename _Rep_type::size_type size_type; typedef typename _Rep_type::difference_type difference_type; typedef typename _Rep_type::allocator_type allocator_type; // allocation/deallocation  // 注意:multimap只能使用RB-tree的insert-equal(),不能使用insert-unique()   /*  构造函数                   multimap();                   explicitmultimap (const key_compare& comp = key_compare(),                                                  const allocator_type& alloc =allocator_type());                                     template<class InputIterator>                   multimap(InputIterator first, InputIterator last,                                     constkey_compare& comp = key_compare(),                                     constallocator_type& alloc = allocator_type());                           multimap(const multimap& x);  */  multimap() : _M_t(_Compare(), allocator_type()) { } explicit multimap(const _Compare& __comp,                    const allocator_type&__a = allocator_type())    :_M_t(__comp, __a) { } #ifdef __STL_MEMBER_TEMPLATES  template <class _InputIterator> multimap(_InputIterator __first, _InputIterator __last)    :_M_t(_Compare(), allocator_type())    {_M_t.insert_equal(__first, __last); }  template <class _InputIterator> multimap(_InputIterator __first, _InputIterator __last,          const _Compare& __comp,          const allocator_type& __a = allocator_type())    :_M_t(__comp, __a) { _M_t.insert_equal(__first, __last); }#else multimap(const value_type* __first, const value_type* __last)    :_M_t(_Compare(), allocator_type())    {_M_t.insert_equal(__first, __last); } multimap(const value_type* __first, const value_type* __last,          const _Compare& __comp,          const allocator_type& __a = allocator_type())    :_M_t(__comp, __a) { _M_t.insert_equal(__first, __last); }  multimap(const_iterator __first, const_iterator __last)    :_M_t(_Compare(), allocator_type())    {_M_t.insert_equal(__first, __last); } multimap(const_iterator __first, const_iterator __last,          const _Compare& __comp,          const allocator_type& __a = allocator_type())    :_M_t(__comp, __a) { _M_t.insert_equal(__first, __last); }#endif /* __STL_MEMBER_TEMPLATES */  //拷贝构造函数 multimap(const multimap<_Key,_Tp,_Compare,_Alloc>& __x) :_M_t(__x._M_t) { }  //这里提供了operator=,即可以通过=初始化对象 multimap<_Key,_Tp,_Compare,_Alloc>& operator=(const multimap<_Key,_Tp,_Compare,_Alloc>& __x) {   _M_t = __x._M_t;   return *this;  }   //accessors:   //返回键值的比较函数,这里是调用RB-Tree的key_comp() key_compare key_comp() const { return _M_t.key_comp(); }   //返回实值的比较函数  //这里调用的是map嵌套类中定义的比较函数  /*           class value_compare                   :public binary_function<value_type, value_type, bool> {           friend classmap<_Key,_Tp,_Compare,_Alloc>;           protected :                   _Comparecomp;                   value_compare(_Compare__c) : comp(__c) {}           public:                   booloperator()(const value_type& __x, const value_type& __y) const {                     return comp(__x.first, __y.first);//以键值调用比较函数                   }  */  //实际上最终还是调用键值key的比较函数，即他们是调用同一个比较函数 value_compare value_comp() const { returnvalue_compare(_M_t.key_comp()); } allocator_type get_allocator() const { return _M_t.get_allocator(); }  iterator begin() { return _M_t.begin(); } const_iterator begin() const { return _M_t.begin(); } iterator end() { return _M_t.end(); } const_iterator end() const { return _M_t.end(); } reverse_iterator rbegin() { return _M_t.rbegin(); } const_reverse_iterator rbegin() const { return _M_t.rbegin(); } reverse_iterator rend() { return _M_t.rend(); } const_reverse_iterator rend() const { return _M_t.rend(); }  //判断容器multimap是否为空 bool empty() const { return _M_t.empty(); }  //返回容器multimap的大小 size_type size() const { return _M_t.size(); } size_type max_size() const { return _M_t.max_size(); }  //交换multimap对象的内容 void swap(multimap<_Key,_Tp,_Compare,_Alloc>& __x) {_M_t.swap(__x._M_t); }   //insert/erase  /*         multimap只能使用RB-tree的insert-equal()         插入元素         iteratorinsert (const value_type& val);                 iteratorinsert (iterator position, const value_type& val);                 template<class InputIterator>         voidinsert (InputIterator first, InputIterator last);  */  //插入元素节点,调用RB-Tree的insert-equal();  //插入元素的键值key允许重复 iterator insert(const value_type& __x) { return_M_t.insert_equal(__x); }  //在指定位置插入元素 iterator insert(iterator __position, const value_type& __x) {   return _M_t.insert_equal(__position, __x);  }#ifdef __STL_MEMBER_TEMPLATES   //插入[first,last)元素 template <class _InputIterator> void insert(_InputIterator __first, _InputIterator __last) {   _M_t.insert_equal(__first, __last);  }#else void insert(const value_type* __first, const value_type* __last) {   _M_t.insert_equal(__first, __last);  } void insert(const_iterator __first, const_iterator __last) {   _M_t.insert_equal(__first, __last);  }#endif /* __STL_MEMBER_TEMPLATES */  /*         擦除元素         voiderase (iterator position);          size_typeerase (const key_type& k);           void erase (iterator first, iterator last);  */  //在指定位置擦除元素 void erase(iterator __position) { _M_t.erase(__position); }  //擦除指定键值的节点 size_type erase(const key_type& __x) { return _M_t.erase(__x); }  //擦除指定区间的节点 void erase(iterator __first, iterator __last)    {_M_t.erase(__first, __last); }  //清空容器 void clear() { _M_t.clear(); }   //multimap operations:   //查找指定键值的节点 iterator find(const key_type& __x) { return _M_t.find(__x); } const_iterator find(const key_type& __x) const { return_M_t.find(__x); }  //计算指定键值元素的个数 size_type count(const key_type& __x) const { return _M_t.count(__x);}  //Returns an iterator pointing to the first element in the container //whose key is not considered to go before k (i.e., either it isequivalent or goes after). //this->first is greater than or equivalent to __x. iterator lower_bound(const key_type& __x) {return_M_t.lower_bound(__x); } const_iterator lower_bound(const key_type& __x) const {   return _M_t.lower_bound(__x);  } //Returns an iterator pointing to the first element that is greater thankey. iterator upper_bound(const key_type& __x) {return_M_t.upper_bound(__x); } const_iterator upper_bound(const key_type& __x) const {   return _M_t.upper_bound(__x);  } //Returns the bounds of a range that includes all the elements in thecontainer //which have a key equivalent to k //Because the elements in a map container have unique keys, //the range returned will contain a single element at most.  pair<iterator,iterator> equal_range(const key_type& __x) {   return _M_t.equal_range(__x);  } pair<const_iterator,const_iterator> equal_range(constkey_type& __x) const {   return _M_t.equal_range(__x);  }    //以下是操作符重载#ifdef __STL_TEMPLATE_FRIENDS template <class _K1, class _T1, class _C1, class _A1> friend bool operator== (const multimap<_K1, _T1, _C1, _A1>&,                          constmultimap<_K1, _T1, _C1, _A1>&); template <class _K1, class _T1, class _C1, class _A1> friend bool operator< (const multimap<_K1, _T1, _C1, _A1>&,                         const multimap<_K1,_T1, _C1, _A1>&);#else /* __STL_TEMPLATE_FRIENDS */ friend bool __STD_QUALIFIER operator== __STL_NULL_TMPL_ARGS (const multimap&, constmultimap&); friend bool __STD_QUALIFIER operator< __STL_NULL_TMPL_ARGS (const multimap&, constmultimap&);#endif /* __STL_TEMPLATE_FRIENDS */}; template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator==(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                       constmultimap<_Key,_Tp,_Compare,_Alloc>& __y) { return __x._M_t == __y._M_t;} template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator<(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                      constmultimap<_Key,_Tp,_Compare,_Alloc>& __y) { return __x._M_t < __y._M_t;} #ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator!=(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                       constmultimap<_Key,_Tp,_Compare,_Alloc>& __y) { return !(__x == __y);} template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator>(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                      constmultimap<_Key,_Tp,_Compare,_Alloc>& __y) { return __y < __x;} template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator<=(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                       constmultimap<_Key,_Tp,_Compare,_Alloc>& __y) { return !(__y < __x);} template <class _Key, class _Tp, class_Compare, class _Alloc>inline bool operator>=(constmultimap<_Key,_Tp,_Compare,_Alloc>& __x,                       constmultimap<_Key,_Tp,_Compare,_Alloc>& __y) { return !(__x < __y);} template <class _Key, class _Tp, class_Compare, class _Alloc>inline void swap(multimap<_Key,_Tp,_Compare,_Alloc>&__x,                multimap<_Key,_Tp,_Compare,_Alloc>& __y) { __x.swap(__y);} #endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER*/ #if defined(__sgi) &&!defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)#pragma reset woff 1174#pragma reset woff 1375#endif __STL_END_NAMESPACE #endif /* __SGI_STL_INTERNAL_MULTIMAP_H */ // Local Variables:// mode:C++// End: