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 multimap
public:
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: