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