关联容器之hash_multimap
最后更新于：2022-04-01 15:51:16
### 前言
hash_multimap和hash_map的区别就像multimap与map的区别一样，hash_multimap的底层机制是基于hash table，它可以存在重复的键值，所以插入函数使用insert_equal()，hash_multimap和hash_map一样，容器的内容不自动排序。由于hash_multimap和hash_map的源码剖析是一样的，这里就不对hash_multimap进行剖析，可以参照《[关联容器之](http://blog.csdn.net/chenhanzhun/article/details/39609093)[hash_map](http://blog.csdn.net/chenhanzhun/article/details/39609093)》。本文源码出自SGI STL的<stl_hash_map.h>文件。
### hash_multimap源码
~~~
// Forward declaration of equality operator; needed for friend declaration.
//hash_multimap与hash_map的差别就是插入函数，前者的插入函数是采用底层机制hash table的insert_equal()
//后者则采用insert_unique()
//其他的功能都和hash_map类似
//hash_multimap允许key重复
//这里就不再进行注释了，可以参考hash_map的解析
template <class _Key, class _Tp,
class _HashFcn __STL_DEPENDENT_DEFAULT_TMPL(hash<_Key>),
class _EqualKey __STL_DEPENDENT_DEFAULT_TMPL(equal_to<_Key>),
class _Alloc = __STL_DEFAULT_ALLOCATOR(_Tp) >
class hash_multimap;
template <class _Key, class _Tp, class _HF, class _EqKey, class _Alloc>
inline bool
operator==(const hash_multimap<_Key,_Tp,_HF,_EqKey,_Alloc>& __hm1,
const hash_multimap<_Key,_Tp,_HF,_EqKey,_Alloc>& __hm2);
template <class _Key, class _Tp, class _HashFcn, class _EqualKey,
class _Alloc>
class hash_multimap
{
// requirements:
__STL_CLASS_REQUIRES(_Key, _Assignable);
__STL_CLASS_REQUIRES(_Tp, _Assignable);
__STL_CLASS_UNARY_FUNCTION_CHECK(_HashFcn, size_t, _Key);
__STL_CLASS_BINARY_FUNCTION_CHECK(_EqualKey, bool, _Key, _Key);
private:
typedef hashtable<pair<const _Key, _Tp>, _Key, _HashFcn,
_Select1st<pair<const _Key, _Tp> >, _EqualKey, _Alloc>
_Ht;
_Ht _M_ht;
public:
typedef typename _Ht::key_type key_type;
typedef _Tp data_type;
typedef _Tp mapped_type;
typedef typename _Ht::value_type value_type;
typedef typename _Ht::hasher hasher;
typedef typename _Ht::key_equal key_equal;
typedef typename _Ht::size_type size_type;
typedef typename _Ht::difference_type difference_type;
typedef typename _Ht::pointer pointer;
typedef typename _Ht::const_pointer const_pointer;
typedef typename _Ht::reference reference;
typedef typename _Ht::const_reference const_reference;
typedef typename _Ht::iterator iterator;
typedef typename _Ht::const_iterator const_iterator;
typedef typename _Ht::allocator_type allocator_type;
hasher hash_funct() const { return _M_ht.hash_funct(); }
key_equal key_eq() const { return _M_ht.key_eq(); }
allocator_type get_allocator() const { return _M_ht.get_allocator(); }
public:
hash_multimap() : _M_ht(100, hasher(), key_equal(), allocator_type()) {}
explicit hash_multimap(size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type()) {}
hash_multimap(size_type __n, const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type()) {}
hash_multimap(size_type __n, const hasher& __hf, const key_equal& __eql,
const allocator_type& __a = allocator_type())
: _M_ht(__n, __hf, __eql, __a) {}
#ifdef __STL_MEMBER_TEMPLATES
template <class _InputIterator>
hash_multimap(_InputIterator __f, _InputIterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
template <class _InputIterator>
hash_multimap(_InputIterator __f, _InputIterator __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
template <class _InputIterator>
hash_multimap(_InputIterator __f, _InputIterator __l, size_type __n,
const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
template <class _InputIterator>
hash_multimap(_InputIterator __f, _InputIterator __l, size_type __n,
const hasher& __hf, const key_equal& __eql,
const allocator_type& __a = allocator_type())
: _M_ht(__n, __hf, __eql, __a)
{ _M_ht.insert_equal(__f, __l); }
#else
hash_multimap(const value_type* __f, const value_type* __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multimap(const value_type* __f, const value_type* __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multimap(const value_type* __f, const value_type* __l, size_type __n,
const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multimap(const value_type* __f, const value_type* __l, size_type __n,
const hasher& __hf, const key_equal& __eql,
const allocator_type& __a = allocator_type())
: _M_ht(__n, __hf, __eql, __a)
{ _M_ht.insert_equal(__f, __l); }
hash_multimap(const_iterator __f, const_iterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multimap(const_iterator __f, const_iterator __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multimap(const_iterator __f, const_iterator __l, size_type __n,
const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multimap(const_iterator __f, const_iterator __l, size_type __n,
const hasher& __hf, const key_equal& __eql,
const allocator_type& __a = allocator_type())
: _M_ht(__n, __hf, __eql, __a)
{ _M_ht.insert_equal(__f, __l); }
#endif /*__STL_MEMBER_TEMPLATES */
public:
size_type size() const { return _M_ht.size(); }
size_type max_size() const { return _M_ht.max_size(); }
bool empty() const { return _M_ht.empty(); }
void swap(hash_multimap& __hs) { _M_ht.swap(__hs._M_ht); }
#ifdef __STL_MEMBER_TEMPLATES
template <class _K1, class _T1, class _HF, class _EqK, class _Al>
friend bool operator== (const hash_multimap<_K1, _T1, _HF, _EqK, _Al>&,
const hash_multimap<_K1, _T1, _HF, _EqK, _Al>&);
#else /* __STL_MEMBER_TEMPLATES */
friend bool __STD_QUALIFIER
operator== __STL_NULL_TMPL_ARGS (const hash_multimap&,const hash_multimap&);
#endif /* __STL_MEMBER_TEMPLATES */
iterator begin() { return _M_ht.begin(); }
iterator end() { return _M_ht.end(); }
const_iterator begin() const { return _M_ht.begin(); }
const_iterator end() const { return _M_ht.end(); }
public:
iterator insert(const value_type& __obj)
{ return _M_ht.insert_equal(__obj); }
#ifdef __STL_MEMBER_TEMPLATES
template <class _InputIterator>
void insert(_InputIterator __f, _InputIterator __l)
{ _M_ht.insert_equal(__f,__l); }
#else
void insert(const value_type* __f, const value_type* __l) {
_M_ht.insert_equal(__f,__l);
}
void insert(const_iterator __f, const_iterator __l)
{ _M_ht.insert_equal(__f, __l); }
#endif /*__STL_MEMBER_TEMPLATES */
iterator insert_noresize(const value_type& __obj)
{ return _M_ht.insert_equal_noresize(__obj); }
iterator find(const key_type& __key) { return _M_ht.find(__key); }
const_iterator find(const key_type& __key) const
{ return _M_ht.find(__key); }
size_type count(const key_type& __key) const { return _M_ht.count(__key); }
pair<iterator, iterator> equal_range(const key_type& __key)
{ return _M_ht.equal_range(__key); }
pair<const_iterator, const_iterator>
equal_range(const key_type& __key) const
{ return _M_ht.equal_range(__key); }
size_type erase(const key_type& __key) {return _M_ht.erase(__key); }
void erase(iterator __it) { _M_ht.erase(__it); }
void erase(iterator __f, iterator __l) { _M_ht.erase(__f, __l); }
void clear() { _M_ht.clear(); }
public:
void resize(size_type __hint) { _M_ht.resize(__hint); }
size_type bucket_count() const { return _M_ht.bucket_count(); }
size_type max_bucket_count() const { return _M_ht.max_bucket_count(); }
size_type elems_in_bucket(size_type __n) const
{ return _M_ht.elems_in_bucket(__n); }
};
template <class _Key, class _Tp, class _HF, class _EqKey, class _Alloc>
inline bool
operator==(const hash_multimap<_Key,_Tp,_HF,_EqKey,_Alloc>& __hm1,
const hash_multimap<_Key,_Tp,_HF,_EqKey,_Alloc>& __hm2)
{
return __hm1._M_ht == __hm2._M_ht;
}
#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER
template <class _Key, class _Tp, class _HF, class _EqKey, class _Alloc>
inline bool
operator!=(const hash_multimap<_Key,_Tp,_HF,_EqKey,_Alloc>& __hm1,
const hash_multimap<_Key,_Tp,_HF,_EqKey,_Alloc>& __hm2) {
return !(__hm1 == __hm2);
}
template <class _Key, class _Tp, class _HashFcn, class _EqlKey, class _Alloc>
inline void
swap(hash_multimap<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm1,
hash_multimap<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm2)
{
__hm1.swap(__hm2);
}
#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */
// Specialization of insert_iterator so that it will work for hash_map
// and hash_multimap.
#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
template <class _Key, class _Tp, class _HashFn, class _EqKey, class _Alloc>
class insert_iterator<hash_map<_Key, _Tp, _HashFn, _EqKey, _Alloc> > {
protected:
typedef hash_map<_Key, _Tp, _HashFn, _EqKey, _Alloc> _Container;
_Container* container;
public:
typedef _Container container_type;
typedef output_iterator_tag iterator_category;
typedef void value_type;
typedef void difference_type;
typedef void pointer;
typedef void reference;
insert_iterator(_Container& __x) : container(&__x) {}
insert_iterator(_Container& __x, typename _Container::iterator)
: container(&__x) {}
insert_iterator<_Container>&
operator=(const typename _Container::value_type& __value) {
container->insert(__value);
return *this;
}
insert_iterator<_Container>& operator*() { return *this; }
insert_iterator<_Container>& operator++() { return *this; }
insert_iterator<_Container>& operator++(int) { return *this; }
};
template <class _Key, class _Tp, class _HashFn, class _EqKey, class _Alloc>
class insert_iterator<hash_multimap<_Key, _Tp, _HashFn, _EqKey, _Alloc> > {
protected:
typedef hash_multimap<_Key, _Tp, _HashFn, _EqKey, _Alloc> _Container;
_Container* container;
typename _Container::iterator iter;
public:
typedef _Container container_type;
typedef output_iterator_tag iterator_category;
typedef void value_type;
typedef void difference_type;
typedef void pointer;
typedef void reference;
insert_iterator(_Container& __x) : container(&__x) {}
insert_iterator(_Container& __x, typename _Container::iterator)
: container(&__x) {}
insert_iterator<_Container>&
operator=(const typename _Container::value_type& __value) {
container->insert(__value);
return *this;
}
insert_iterator<_Container>& operator*() { return *this; }
insert_iterator<_Container>& operator++() { return *this; }
insert_iterator<_Container>& operator++(int) { return *this; }
};
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
#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_HASH_MAP_H */
// Local Variables:
// mode:C++
// End:
~~~
参考资料：
《STL源码剖析》侯捷