STL源码剖析——关联容器之hash_multiset

前言

       hash_multiset和hash_set的区别就像multiset与set的区别一样，hash_multiset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_multiset和hash_set一样，容器的内容不自动排序。本文源码出自SGI STL的<stl_hash_set.h>文件。

hash_multiset源码剖析

//以下是hash_multiset的定义/*hash_multiset是基于底层机制为hash table,hash_multiset的元素不会自动排序，其他功能与multiset类似,hash_multiset与hash_set的区别和multiset与set区别一样，hash_multiset的插入函数是hash table的insert_equal()*/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);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://_Identity获取value值，在hash_set中也是键值，_Identity<>定义在<stl_function.h>/*template <class _Arg, class _Result>struct unary_function {  typedef _Arg argument_type;  typedef _Result result_type;};template <class _Tp>struct _Identity : public unary_function<_Tp,_Tp> {const _Tp& operator()(const _Tp& __x) const { return __x; }};*/  typedef hashtable<_Value, _Value, _HashFcn, _Identity<_Value>,                     _EqualKey, _Alloc> _Ht;  _Ht _M_ht;//底层机制是hashtablepublic:  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;   // 注意: 不能修改hash table内部的元素,reference, pointer, iterator都为const  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;  //返回hash函数  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://构造函数和hash_set一样,具体可以参照hash_set的讲解//唯一的区别就是插入函数是insert_equal()  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  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://Returns the number of elements in the hash_multiset container  size_type size() const { return _M_ht.size(); }  //Returns the maximum number of elements that the hash_multiset container can hold.  size_type max_size() const { return _M_ht.max_size(); }  //Returns a bool value indicating whether the hash_multiset container is empty,  //i.e. whether its size is 0.  bool empty() const { return _M_ht.empty(); }  //交换两个hash_multiset的内容  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://插入元素/*iterator insert ( const value_type& val );template <class InputIterator>void insert ( InputIterator first, InputIterator last );*/  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); }      //Searches the container for an element with k as key and returns an iterator to it if found,   //otherwise it returns an iterator to hash_multiset::end (the element past the end of the container).  iterator find(const key_type& __key) const { return _M_ht.find(__key); }  //Searches the container for elements with a value of k and returns the number of elements found  size_type count(const key_type& __key) const { return _M_ht.count(__key); }    //Returns the bounds of a range that includes all the elements in the container that compare equal to k.  pair<iterator, iterator> equal_range(const key_type& __key) const    { return _M_ht.equal_range(__key); }  //删除元素  /*by position (1):iterator erase ( const_iterator position );by key (2):size_type erase ( const key_type& k );range (3):iterator erase ( const_iterator first, const_iterator last );  */  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); }  //清空容器  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_ORDERtemplate <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 */

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