STL学习——hash_set/hash_map/hash_multiset/hash_multimap篇

STL学习_hash_set/hash_map/hash_multiset/hash_multimap篇

hash_set与hash_multiset

简介

hash_set是以hashtable为底层机制实现的。故对hash_set的各种操作可以转调用hashtable来实现。

hash_set与set的不同：1）hash_set的底层机制是hashtable，而set的底层机制是RB-tree；2）set的元素能够自动排序，而hash_set的元素没有排序功能。hash_set中键值就是实值，实值就是键值。

hash_multiset的与hash_set有很大的相同性，其唯一差别就是hash_multiset中的元素可以重复。hash_set中的插入函数使用的是hashtable中的insert_unique()，而hash_multiset中的插入函数使用的是hashtable中的insert_equal()。

源码分析

// hash_set类定义
class hash_set
{
// requirements:
__STL_CLASS_REQUIRES(_Value, _Assignable);
__STL_CLASS_UNARY_FUNCTION_CHECK(_HashFcn, size_t, _Value);
__STL_CLASS_BINARY_FUNCTION_CHECK(_EqualKey, bool, _Value, _Value);

private:
typedef hashtable<_Value, _Value, _HashFcn, _Identity<_Value>,
_EqualKey, _Alloc> _Ht;
_Ht _M_ht;    // 底层机制为hashtable完成

public:
typedef typename _Ht::key_type key_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::const_pointer pointer;
typedef typename _Ht::const_pointer const_pointer;
typedef typename _Ht::const_reference reference;
typedef typename _Ht::const_reference const_reference;

typedef typename _Ht::const_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:
// 缺省使用大小为100的表格。将被hash table调整为最接近且较大之质数
hash_set()
: _M_ht(100, hasher(), key_equal(), allocator_type()) {}
explicit hash_set(size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type()) {}
hash_set(size_type __n, const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type()) {}
hash_set(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_set(_InputIterator __f, _InputIterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
template <class _InputIterator>
hash_set(_InputIterator __f, _InputIterator __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
template <class _InputIterator>
hash_set(_InputIterator __f, _InputIterator __l, size_type __n,
const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
template <class _InputIterator>
hash_set(_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_unique(__f, __l); }
#else
// 以下，插入操作全部使用insert_unique()，不允许键值重复
hash_set(const value_type* __f, const value_type* __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_set(const value_type* __f, const value_type* __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_set(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_unique(__f, __l); }
hash_set(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_unique(__f, __l); }

hash_set(const_iterator __f, const_iterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_set(const_iterator __f, const_iterator __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_set(const_iterator __f, const_iterator __l, size_type __n,
const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_set(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_unique(__f, __l); }
#endif /*__STL_MEMBER_TEMPLATES */

public:
// 所有操作几乎都是hash table对应版本。传递调用就行
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_set& __hs) { _M_ht.swap(__hs._M_ht); }

#ifdef __STL_MEMBER_TEMPLATES
template <class _Val, class _HF, class _EqK, class _Al>
friend bool operator== (const hash_set<_Val, _HF, _EqK, _Al>&,
const hash_set<_Val, _HF, _EqK, _Al>&);
#else /* __STL_MEMBER_TEMPLATES */
friend bool __STD_QUALIFIER
operator== __STL_NULL_TMPL_ARGS (const hash_set&, const hash_set&);
#endif /* __STL_MEMBER_TEMPLATES */

iterator begin() const { return _M_ht.begin(); }
iterator end() const { return _M_ht.end(); }

public:
pair<iterator, bool> insert(const value_type& __obj)
{
pair<typename _Ht::iterator, bool> __p = _M_ht.insert_unique(__obj);
return pair<iterator,bool>(__p.first, __p.second);
}
#ifdef __STL_MEMBER_TEMPLATES
template <class _InputIterator>
void insert(_InputIterator __f, _InputIterator __l)
{ _M_ht.insert_unique(__f,__l); }
#else
void insert(const value_type* __f, const value_type* __l) {
_M_ht.insert_unique(__f,__l);
}
void insert(const_iterator __f, const_iterator __l)
{_M_ht.insert_unique(__f, __l); }
#endif /*__STL_MEMBER_TEMPLATES */
pair<iterator, bool> insert_noresize(const value_type& __obj)
{
pair<typename _Ht::iterator, bool> __p =
_M_ht.insert_unique_noresize(__obj);
return pair<iterator, bool>(__p.first, __p.second);
}

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) 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 _Value, class _HashFcn, class _EqualKey, class _Alloc>
inline bool
operator==(const hash_set<_Value,_HashFcn,_EqualKey,_Alloc>& __hs1,
const hash_set<_Value,_HashFcn,_EqualKey,_Alloc>& __hs2)
{
return __hs1._M_ht == __hs2._M_ht;
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _Value, class _HashFcn, class _EqualKey, class _Alloc>
inline bool
operator!=(const hash_set<_Value,_HashFcn,_EqualKey,_Alloc>& __hs1,
const hash_set<_Value,_HashFcn,_EqualKey,_Alloc>& __hs2) {
return !(__hs1 == __hs2);
}

template <class _Val, class _HashFcn, class _EqualKey, class _Alloc>
inline void
swap(hash_set<_Val,_HashFcn,_EqualKey,_Alloc>& __hs1,
hash_set<_Val,_HashFcn,_EqualKey,_Alloc>& __hs2)
{
__hs1.swap(__hs2);
}

#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */

template <class _Value,
class _HashFcn  __STL_DEPENDENT_DEFAULT_TMPL(hash<_Value>),
class _EqualKey __STL_DEPENDENT_DEFAULT_TMPL(equal_to<_Value>),
class _Alloc =  __STL_DEFAULT_ALLOCATOR(_Value) >
class hash_multiset;

template <class _Val, class _HashFcn, class _EqualKey, class _Alloc>
inline bool
operator==(const hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs1,
const hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs2);

// hash_multiset类
template <class _Value, class _HashFcn, class _EqualKey, class _Alloc>
class hash_multiset
{
// requirements:

__STL_CLASS_REQUIRES(_Value, _Assignable);
__STL_CLASS_UNARY_FUNCTION_CHECK(_HashFcn, size_t, _Value);
__STL_CLASS_BINARY_FUNCTION_CHECK(_EqualKey, bool, _Value, _Value);

private:
typedef hashtable<_Value, _Value, _HashFcn, _Identity<_Value>,
_EqualKey, _Alloc> _Ht;
_Ht _M_ht;           // 底层实现机制为hashtable

public:
typedef typename _Ht::key_type key_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::const_pointer pointer;
typedef typename _Ht::const_pointer const_pointer;
typedef typename _Ht::const_reference reference;
typedef typename _Ht::const_reference const_reference;

typedef typename _Ht::const_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:
// 缺省使用大小为100的表格。将被hash table调整为最接近且较大之质数
hash_multiset()
: _M_ht(100, hasher(), key_equal(), allocator_type()) {}
explicit hash_multiset(size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type()) {}
hash_multiset(size_type __n, const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type()) {}
hash_multiset(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_multiset(_InputIterator __f, _InputIterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
template <class _InputIterator>
hash_multiset(_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_multiset(_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_multiset(_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

// 以下插入操作全部使用inset\_equal()，允许键值重复
hash_multiset(const value_type* __f, const value_type* __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multiset(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_multiset(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_multiset(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_multiset(const_iterator __f, const_iterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multiset(const_iterator __f, const_iterator __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_equal(__f, __l); }
hash_multiset(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_multiset(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:
// 所有操作几乎都是hash table的对应版本，传递调用即可。
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_multiset& hs) { _M_ht.swap(hs._M_ht); }

#ifdef __STL_MEMBER_TEMPLATES
template <class _Val, class _HF, class _EqK, class _Al>
friend bool operator== (const hash_multiset<_Val, _HF, _EqK, _Al>&,
const hash_multiset<_Val, _HF, _EqK, _Al>&);
#else /* __STL_MEMBER_TEMPLATES */
friend bool __STD_QUALIFIER
operator== __STL_NULL_TMPL_ARGS (const hash_multiset&,const hash_multiset&);
#endif /* __STL_MEMBER_TEMPLATES */

iterator begin() const { return _M_ht.begin(); }
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) 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) 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 _Val, class _HashFcn, class _EqualKey, class _Alloc>
inline bool
operator==(const hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs1,
const hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs2)
{
return __hs1._M_ht == __hs2._M_ht;
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _Val, class _HashFcn, class _EqualKey, class _Alloc>
inline bool
operator!=(const hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs1,
const hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs2) {
return !(__hs1 == __hs2);
}

template <class _Val, class _HashFcn, class _EqualKey, class _Alloc>
inline void
swap(hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs1,
hash_multiset<_Val,_HashFcn,_EqualKey,_Alloc>& __hs2) {
__hs1.swap(__hs2);
}

#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */

// Specialization of insert_iterator so that it will work for hash_set
// and hash_multiset.

#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION

template <class _Value, class _HashFcn, class _EqualKey, class _Alloc>
class insert_iterator<hash_set<_Value, _HashFcn, _EqualKey, _Alloc> > {
protected:
typedef hash_set<_Value, _HashFcn, _EqualKey, _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 _Value, class _HashFcn, class _EqualKey, class _Alloc>
class insert_iterator<hash_multiset<_Value, _HashFcn, _EqualKey, _Alloc> > {
protected:
typedef hash_multiset<_Value, _HashFcn, _EqualKey, _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; }
};

hash_map与hash_multimap

简介

hash_map的底层实现机制是hashtable。故hash_map的操作行为都可以转hashtable的操作实现。hash_map与map之间的区别：1）底层实现机制不同。hash_map的底层实现机制是hashtable，而map的底层实现机制是RB-tree。2）map具有自动排序功能，而hash_map不具有自动排序功能。hash_map中的每一个元素都同时拥有实值（value）和键值（key）。

hash_multimap与hash_map基本相似，二者主要的不同是hash_map中的元素不允许重复，但hash_multimap中的元素可以重复。故hash_mutimap中的插入函数使用的是hashtable中的insert_equal()，而hash_map中的插入函数使用的是hashtable中的insert_unique()函数。

源码分析

template <class _Key, class _Tp, class _HashFcn, class _EqualKey,
class _Alloc>
class hash_map
{
// 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;        // 底层机制以hash table完成

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:
// 缺省使用大小为100的表格。将由hash table调整为最接近且较大之质数
hash_map() : _M_ht(100, hasher(), key_equal(), allocator_type()) {}
explicit hash_map(size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type()) {}
hash_map(size_type __n, const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type()) {}
hash_map(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_map(_InputIterator __f, _InputIterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
template <class _InputIterator>
hash_map(_InputIterator __f, _InputIterator __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
template <class _InputIterator>
hash_map(_InputIterator __f, _InputIterator __l, size_type __n,
const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
template <class _InputIterator>
hash_map(_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_unique(__f, __l); }

#else
// 以下，插入操作全部使用insert_unique()，不允许键值重复
hash_map(const value_type* __f, const value_type* __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_map(const value_type* __f, const value_type* __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_map(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_unique(__f, __l); }
hash_map(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_unique(__f, __l); }

hash_map(const_iterator __f, const_iterator __l)
: _M_ht(100, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_map(const_iterator __f, const_iterator __l, size_type __n)
: _M_ht(__n, hasher(), key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_map(const_iterator __f, const_iterator __l, size_type __n,
const hasher& __hf)
: _M_ht(__n, __hf, key_equal(), allocator_type())
{ _M_ht.insert_unique(__f, __l); }
hash_map(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_unique(__f, __l); }
#endif /*__STL_MEMBER_TEMPLATES */

public:
// 所有操作几乎都有hash table对应版本。传递调用就行
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_map& __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_map<_K1, _T1, _HF, _EqK, _Al>&,
const hash_map<_K1, _T1, _HF, _EqK, _Al>&);
#else /* __STL_MEMBER_TEMPLATES */
friend bool __STD_QUALIFIER
operator== __STL_NULL_TMPL_ARGS (const hash_map&, const hash_map&);
#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:
pair<iterator,bool> insert(const value_type& __obj)
{ return _M_ht.insert_unique(__obj); }
#ifdef __STL_MEMBER_TEMPLATES
template <class _InputIterator>
void insert(_InputIterator __f, _InputIterator __l)
{ _M_ht.insert_unique(__f,__l); }
#else
void insert(const value_type* __f, const value_type* __l) {
_M_ht.insert_unique(__f,__l);
}
void insert(const_iterator __f, const_iterator __l)
{ _M_ht.insert_unique(__f, __l); }
#endif /*__STL_MEMBER_TEMPLATES */
pair<iterator,bool> insert_noresize(const value_type& __obj)
{ return _M_ht.insert_unique_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); }

_Tp& operator[](const key_type& __key) {
return _M_ht.find_or_insert(value_type(__key, _Tp())).second;
}

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(); }

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 _HashFcn, class _EqlKey, class _Alloc>
inline bool
operator==(const hash_map<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm1,
const hash_map<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm2)
{
return __hm1._M_ht == __hm2._M_ht;
}

#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER

template <class _Key, class _Tp, class _HashFcn, class _EqlKey, class _Alloc>
inline bool
operator!=(const hash_map<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm1,
const hash_map<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm2) {
return !(__hm1 == __hm2);
}

template <class _Key, class _Tp, class _HashFcn, class _EqlKey, class _Alloc>
inline void
swap(hash_map<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm1,
hash_map<_Key,_Tp,_HashFcn,_EqlKey,_Alloc>& __hm2)
{
__hm1.swap(__hm2);
}

#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */

// Forward declaration of equality operator; needed for friend declaration.

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>

// hash_multimap类
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;           // 底层实现机制为hashtable

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:
// 缺省使用大小为100的表格。将被hash table调整为最接近且较大之质数
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
// 以下，插入操作全部使用insert_equal()，允许键值重复
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:
// 所有操作几乎都有hash table的对应版本，传递调用即可。
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); }
};

参考文献

STL源码剖析——侯捷

STL源码