散列表hashtable · STL源碼剖析

### 前言 ? 前面介紹的關聯容器set、multiset、map和multimap的底層機制都是基于RB-Tree紅黑樹，雖然能夠實現在插入、刪除和搜素操作能夠達到對數平均時間，可是要求輸入數據有足夠的隨機性。本文介紹的hash table不需要要求輸入數據具有隨機性，在插入、刪除和搜素操作都能達到常數平均時間。本文介紹的hash table是來自SGI STL中的<stl_hashtable.h>文件，在這里為了避免沖突（即不同元素映射到相同的鍵值位置），采用了拉鏈法來解決沖突問題。SGI中實現hash table的方式，在每個表格元素中維護一個鏈表, 然后在鏈表上執行元素的插入、搜尋、刪除等操作，該表格中的每個元素被稱為桶(bucket)。有關hash table的介紹可往前面博文《[散列表](http://blog.csdn.net/chenhanzhun/article/details/38091431)》查看。 ### hashtable散列表源碼剖析 ~~~ #ifndef __SGI_STL_INTERNAL_HASHTABLE_H #define __SGI_STL_INTERNAL_HASHTABLE_H // Hashtable class, used to implement the hashed associative containers // hash_set, hash_map, hash_multiset, and hash_multimap. //SGI STL的hashtable的實現方法是拉鏈法. //拉鏈法可以避免hashtable的沖突問題,即不同數據映射到同一的hash值 //有關hashtable的介紹見前文: //http://blog.csdn.net/chenhanzhun/article/details/38091431 #include <stl_algobase.h> #include <stl_alloc.h> #include <stl_construct.h> #include <stl_tempbuf.h> #include <stl_algo.h> #include <stl_uninitialized.h> #include <stl_function.h> #include <stl_vector.h> #include <stl_hash_fun.h> __STL_BEGIN_NAMESPACE //hashtable中鏈表的節點結構 //類似于單鏈表的節點結構 template <class _Val> struct _Hashtable_node { _Hashtable_node* _M_next;//指向下一節點 _Val _M_val;//節點元素值 }; //這里使用前置聲明, 避免在后面交叉引用會導致編譯錯誤 template <class _Val, class _Key, class _HashFcn, class _ExtractKey, class _EqualKey, class _Alloc = alloc> class hashtable; template <class _Val, class _Key, class _HashFcn, class _ExtractKey, class _EqualKey, class _Alloc> struct _Hashtable_iterator; template <class _Val, class _Key, class _HashFcn, class _ExtractKey, class _EqualKey, class _Alloc> struct _Hashtable_const_iterator; //hashtable迭代器定義 //注意：hash table迭代器沒有提供后退操作operator-- //也沒用提供逆向迭代器reverse iterator template <class _Val, class _Key, class _HashFcn, class _ExtractKey, class _EqualKey, class _Alloc> struct _Hashtable_iterator { //內嵌類型別名 typedef hashtable<_Val,_Key,_HashFcn,_ExtractKey,_EqualKey,_Alloc> _Hashtable; typedef _Hashtable_iterator<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc> iterator; typedef _Hashtable_const_iterator<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc> const_iterator; typedef _Hashtable_node<_Val> _Node; typedef forward_iterator_tag iterator_category;//采用正向迭代器 typedef _Val value_type; typedef ptrdiff_t difference_type; typedef size_t size_type; typedef _Val& reference; typedef _Val* pointer; _Node* _M_cur;//當前迭代器所指位置 _Hashtable* _M_ht;//hashtable中的位置,控制訪問桶子連續性 _Hashtable_iterator(_Node* __n, _Hashtable* __tab) : _M_cur(__n), _M_ht(__tab) {} _Hashtable_iterator() {} //返回當前節點元素值的引用 reference operator*() const { return _M_cur->_M_val; } #ifndef __SGI_STL_NO_ARROW_OPERATOR pointer operator->() const { return &(operator*()); } #endif /* __SGI_STL_NO_ARROW_OPERATOR */ //操作符重載定義在后面定義 iterator& operator++(); iterator operator++(int); //比較兩個迭代器是否指向同一個節點 bool operator==(const iterator& __it) const { return _M_cur == __it._M_cur; } bool operator!=(const iterator& __it) const { return _M_cur != __it._M_cur; } }; //下面是const iterator的定義，基本和上面相同 template <class _Val, class _Key, class _HashFcn, class _ExtractKey, class _EqualKey, class _Alloc> struct _Hashtable_const_iterator { typedef hashtable<_Val,_Key,_HashFcn,_ExtractKey,_EqualKey,_Alloc> _Hashtable; typedef _Hashtable_iterator<_Val,_Key,_HashFcn, _ExtractKey,_EqualKey,_Alloc> iterator; typedef _Hashtable_const_iterator<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc> const_iterator; typedef _Hashtable_node<_Val> _Node; typedef forward_iterator_tag iterator_category; typedef _Val value_type; typedef ptrdiff_t difference_type; typedef size_t size_type; typedef const _Val& reference; typedef const _Val* pointer; const _Node* _M_cur; const _Hashtable* _M_ht; _Hashtable_const_iterator(const _Node* __n, const _Hashtable* __tab) : _M_cur(__n), _M_ht(__tab) {} _Hashtable_const_iterator() {} _Hashtable_const_iterator(const iterator& __it) : _M_cur(__it._M_cur), _M_ht(__it._M_ht) {} reference operator*() const { return _M_cur->_M_val; } #ifndef __SGI_STL_NO_ARROW_OPERATOR pointer operator->() const { return &(operator*()); } #endif /* __SGI_STL_NO_ARROW_OPERATOR */ const_iterator& operator++(); const_iterator operator++(int); bool operator==(const const_iterator& __it) const { return _M_cur == __it._M_cur; } bool operator!=(const const_iterator& __it) const { return _M_cur != __it._M_cur; } }; // Note: assumes long is at least 32 bits. // 注意：假設long至少為32-bits, 可以根據自己需要修改 //定義28個素數用作hashtable的大小 enum { __stl_num_primes = 28 }; static const unsigned long __stl_prime_list[__stl_num_primes] = { 53ul, 97ul, 193ul, 389ul, 769ul, 1543ul, 3079ul, 6151ul, 12289ul, 24593ul, 49157ul, 98317ul, 196613ul, 393241ul, 786433ul, 1572869ul, 3145739ul, 6291469ul, 12582917ul, 25165843ul, 50331653ul, 100663319ul, 201326611ul, 402653189ul, 805306457ul, 1610612741ul, 3221225473ul, 4294967291ul }; //返回大于n的最小素數 inline unsigned long __stl_next_prime(unsigned long __n) { const unsigned long* __first = __stl_prime_list; const unsigned long* __last = __stl_prime_list + (int)__stl_num_primes; const unsigned long* pos = lower_bound(__first, __last, __n); /* 上面的lower_bound調用的是STL中的算法lower_bound(); 該算法的功能： Returns an iterator pointing to the first element in the range [first,last) which does not compare less than val. The elements in the range shall already be sorted according to this same criterion (operator< or comp) 即返回在[first,last)范圍內第一個不小于val的位置注意：調用該算法之前，[first,last)范圍里面的元素必須已排序該算法的原型如下：第一個版本：采用默認比較準則operator< template <class ForwardIterator, class T> ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last, const T& val); 第二版本：采用用戶指定的比較函數comp template <class ForwardIterator, class T, class Compare> ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last, const T& val, Compare comp); 其實該算法的實現機制使用二分查找法進行查找元素val： template <class ForwardIterator, class T> ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last, const T& val) { ForwardIterator it; iterator_traits<ForwardIterator>::difference_type count, step; count = distance(first,last); while (count>0) { it = first; step=count/2; advance (it,step); if (*it<val) { // or: if (comp(*it,val)), for version (2) first=++it; count-=step+1; } else count=step; } return first; } 下面給出例子：lower_bound/upper_bound example #include <iostream> // std::cout #include <algorithm> // std::lower_bound, std::upper_bound, std::sort #include <vector> // std::vector int main () { int myints[] = {10,20,30,30,20,10,10,20}; std::vector<int> v(myints,myints+8); // 10 20 30 30 20 10 10 20 std::sort (v.begin(), v.end()); // 10 10 10 20 20 20 30 30 std::vector<int>::iterator low,up; low=std::lower_bound (v.begin(), v.end(), 20); // ^ up= std::upper_bound (v.begin(), v.end(), 20); // ^ std::cout << "lower_bound at position " << (low- v.begin()) << '\n'; std::cout << "upper_bound at position " << (up - v.begin()) << '\n'; return 0; } Output: lower_bound at position 3 upper_bound at position 6 */ return pos == __last ? *(__last - 1) : *pos; } // Forward declaration of operator==. template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> class hashtable; template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> bool operator==(const hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>& __ht1, const hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>& __ht2); // Hashtables handle allocators a bit differently than other containers // do. If we're using standard-conforming allocators, then a hashtable // unconditionally has a member variable to hold its allocator, even if // it so happens that all instances of the allocator type are identical. // This is because, for hashtables, this extra storage is negligible. // Additionally, a base class wouldn't serve any other purposes; it // wouldn't, for example, simplify the exception-handling code. //hash table的定義 //模板參數定義 /* Value：節點的實值類型 Key：節點的鍵值類型 HashFcn： hash function的類型 ExtractKey：從節點中取出鍵值的方法（函數或仿函數） EqualKey：判斷鍵值是否相同的方法（函數或仿函數） Alloc：空間配置器 */ //hash table的線性表是用vector容器維護 template <class _Val, class _Key, class _HashFcn, class _ExtractKey, class _EqualKey, class _Alloc> class hashtable { public: typedef _Key key_type; typedef _Val value_type; typedef _HashFcn hasher; typedef _EqualKey key_equal; typedef size_t size_type; typedef ptrdiff_t difference_type; typedef value_type* pointer; typedef const value_type* const_pointer; typedef value_type& reference; typedef const value_type& const_reference; hasher hash_funct() const { return _M_hash; } key_equal key_eq() const { return _M_equals; } private: typedef _Hashtable_node<_Val> _Node; #ifdef __STL_USE_STD_ALLOCATORS public: typedef typename _Alloc_traits<_Val,_Alloc>::allocator_type allocator_type; allocator_type get_allocator() const { return _M_node_allocator; } private: typename _Alloc_traits<_Node, _Alloc>::allocator_type _M_node_allocator; _Node* _M_get_node() { return _M_node_allocator.allocate(1); } void _M_put_node(_Node* __p) { _M_node_allocator.deallocate(__p, 1); } # define __HASH_ALLOC_INIT(__a) _M_node_allocator(__a), #else /* __STL_USE_STD_ALLOCATORS */ public: typedef _Alloc allocator_type; allocator_type get_allocator() const { return allocator_type(); } private: typedef simple_alloc<_Node, _Alloc> _M_node_allocator_type; _Node* _M_get_node() { return _M_node_allocator_type::allocate(1); } void _M_put_node(_Node* __p) { _M_node_allocator_type::deallocate(__p, 1); } # define __HASH_ALLOC_INIT(__a) #endif /* __STL_USE_STD_ALLOCATORS */ //以下是hash table的成員變量 private: hasher _M_hash; key_equal _M_equals; _ExtractKey _M_get_key; vector<_Node*,_Alloc> _M_buckets;//用vector維護buckets size_type _M_num_elements;//hashtable中list節點個數 public: typedef _Hashtable_iterator<_Val,_Key,_HashFcn,_ExtractKey,_EqualKey,_Alloc> iterator; typedef _Hashtable_const_iterator<_Val,_Key,_HashFcn,_ExtractKey,_EqualKey, _Alloc> const_iterator; friend struct _Hashtable_iterator<_Val,_Key,_HashFcn,_ExtractKey,_EqualKey,_Alloc>; friend struct _Hashtable_const_iterator<_Val,_Key,_HashFcn,_ExtractKey,_EqualKey,_Alloc>; public: //構造函數 hashtable(size_type __n, const _HashFcn& __hf, const _EqualKey& __eql, const _ExtractKey& __ext, const allocator_type& __a = allocator_type()) : __HASH_ALLOC_INIT(__a) _M_hash(__hf), _M_equals(__eql), _M_get_key(__ext), _M_buckets(__a), _M_num_elements(0) { _M_initialize_buckets(__n);//預留空間,并將其初始化為空0 //預留空間大小為大于n的最小素數 } hashtable(size_type __n, const _HashFcn& __hf, const _EqualKey& __eql, const allocator_type& __a = allocator_type()) : __HASH_ALLOC_INIT(__a) _M_hash(__hf), _M_equals(__eql), _M_get_key(_ExtractKey()), _M_buckets(__a), _M_num_elements(0) { _M_initialize_buckets(__n); } //拷貝構造函數 hashtable(const hashtable& __ht) : __HASH_ALLOC_INIT(__ht.get_allocator()) _M_hash(__ht._M_hash), _M_equals(__ht._M_equals), _M_get_key(__ht._M_get_key), _M_buckets(__ht.get_allocator()), _M_num_elements(0) { _M_copy_from(__ht);//復制hashtable內容 } #undef __HASH_ALLOC_INIT //可以通過operator=初始化hashtable對象 hashtable& operator= (const hashtable& __ht) { if (&__ht != this) { clear(); _M_hash = __ht._M_hash; _M_equals = __ht._M_equals; _M_get_key = __ht._M_get_key; _M_copy_from(__ht); } return *this; } ~hashtable() { clear(); } //返回hashtable元素的個數 size_type size() const { return _M_num_elements; } size_type max_size() const { return size_type(-1); } bool empty() const { return size() == 0; } //交換兩個hashtable的內容 void swap(hashtable& __ht) { __STD::swap(_M_hash, __ht._M_hash); __STD::swap(_M_equals, __ht._M_equals); __STD::swap(_M_get_key, __ht._M_get_key); _M_buckets.swap(__ht._M_buckets); __STD::swap(_M_num_elements, __ht._M_num_elements); } iterator begin() { for (size_type __n = 0; __n < _M_buckets.size(); ++__n) if (_M_buckets[__n])//若hashtable中的桶子_M_buckets有鏈表list return iterator(_M_buckets[__n], this);//返回鏈表的第一個節點位置 return end();//若list鏈表為空,則返回尾端end(),其實這里尾端和起始端一樣 } iterator end() { return iterator(0, this); }//返回桶子list鏈表的null指針,即尾端 const_iterator begin() const { for (size_type __n = 0; __n < _M_buckets.size(); ++__n) if (_M_buckets[__n]) return const_iterator(_M_buckets[__n], this); return end(); } const_iterator end() const { return const_iterator(0, this); } #ifdef __STL_MEMBER_TEMPLATES template <class _Vl, class _Ky, class _HF, class _Ex, class _Eq, class _Al> friend bool operator== (const hashtable<_Vl, _Ky, _HF, _Ex, _Eq, _Al>&, const hashtable<_Vl, _Ky, _HF, _Ex, _Eq, _Al>&); #else /* __STL_MEMBER_TEMPLATES */ friend bool __STD_QUALIFIER operator== __STL_NULL_TMPL_ARGS (const hashtable&, const hashtable&); #endif /* __STL_MEMBER_TEMPLATES */ public: //返回桶子個數,即線性表中節點數 size_type bucket_count() const { return _M_buckets.size(); } //線性表最多分配節點數 size_type max_bucket_count() const { return __stl_prime_list[(int)__stl_num_primes - 1]; } //指定桶子鍵值key中list鏈表的元素個數 size_type elems_in_bucket(size_type __bucket) const { size_type __result = 0; for (_Node* __cur = _M_buckets[__bucket]; __cur; __cur = __cur->_M_next) __result += 1; return __result; } //插入元素節點,不允許存在重復元素 pair<iterator, bool> insert_unique(const value_type& __obj) { //判斷容量是否夠用, 否則就重新配置 resize(_M_num_elements + 1); //插入元素,不允許存在重復元素 return insert_unique_noresize(__obj); } //插入元素節點,允許存在重復元素 iterator insert_equal(const value_type& __obj) {//判斷容量是否夠用, 否則就重新配置 resize(_M_num_elements + 1); //插入元素,允許存在重復元素 return insert_equal_noresize(__obj); } //具體定義見hashtable類外后面的剖析 pair<iterator, bool> insert_unique_noresize(const value_type& __obj); iterator insert_equal_noresize(const value_type& __obj); #ifdef __STL_MEMBER_TEMPLATES template <class _InputIterator> void insert_unique(_InputIterator __f, _InputIterator __l) { insert_unique(__f, __l, __ITERATOR_CATEGORY(__f)); } template <class _InputIterator> void insert_equal(_InputIterator __f, _InputIterator __l) { insert_equal(__f, __l, __ITERATOR_CATEGORY(__f)); } template <class _InputIterator> void insert_unique(_InputIterator __f, _InputIterator __l, input_iterator_tag) { for ( ; __f != __l; ++__f) insert_unique(*__f); } template <class _InputIterator> void insert_equal(_InputIterator __f, _InputIterator __l, input_iterator_tag) { for ( ; __f != __l; ++__f) insert_equal(*__f); } template <class _ForwardIterator> void insert_unique(_ForwardIterator __f, _ForwardIterator __l, forward_iterator_tag) { size_type __n = 0; distance(__f, __l, __n); resize(_M_num_elements + __n); for ( ; __n > 0; --__n, ++__f) insert_unique_noresize(*__f); } template <class _ForwardIterator> void insert_equal(_ForwardIterator __f, _ForwardIterator __l, forward_iterator_tag) { size_type __n = 0; distance(__f, __l, __n); resize(_M_num_elements + __n); for ( ; __n > 0; --__n, ++__f) insert_equal_noresize(*__f); } #else /* __STL_MEMBER_TEMPLATES */ void insert_unique(const value_type* __f, const value_type* __l) { size_type __n = __l - __f; resize(_M_num_elements + __n); for ( ; __n > 0; --__n, ++__f) insert_unique_noresize(*__f); } void insert_equal(const value_type* __f, const value_type* __l) { size_type __n = __l - __f; resize(_M_num_elements + __n); for ( ; __n > 0; --__n, ++__f) insert_equal_noresize(*__f); } void insert_unique(const_iterator __f, const_iterator __l) { size_type __n = 0; distance(__f, __l, __n); resize(_M_num_elements + __n); for ( ; __n > 0; --__n, ++__f) insert_unique_noresize(*__f); } void insert_equal(const_iterator __f, const_iterator __l) { size_type __n = 0; distance(__f, __l, __n); resize(_M_num_elements + __n); for ( ; __n > 0; --__n, ++__f) insert_equal_noresize(*__f); } #endif /*__STL_MEMBER_TEMPLATES */ reference find_or_insert(const value_type& __obj); //查找指定鍵值的元素 iterator find(const key_type& __key) { size_type __n = _M_bkt_num_key(__key);//獲取鍵值 _Node* __first; for ( __first = _M_buckets[__n]; __first && !_M_equals(_M_get_key(__first->_M_val), __key); __first = __first->_M_next) {} return iterator(__first, this); } const_iterator find(const key_type& __key) const { size_type __n = _M_bkt_num_key(__key); const _Node* __first; for ( __first = _M_buckets[__n]; __first && !_M_equals(_M_get_key(__first->_M_val), __key); __first = __first->_M_next) {} return const_iterator(__first, this); } //返回鍵值為key的元素的個數 size_type count(const key_type& __key) const { const size_type __n = _M_bkt_num_key(__key); size_type __result = 0; for (const _Node* __cur = _M_buckets[__n]; __cur; __cur = __cur->_M_next) if (_M_equals(_M_get_key(__cur->_M_val), __key)) ++__result; return __result; } pair<iterator, iterator> equal_range(const key_type& __key); pair<const_iterator, const_iterator> equal_range(const key_type& __key) const; //擦除元素 size_type erase(const key_type& __key); void erase(const iterator& __it); void erase(iterator __first, iterator __last); void erase(const const_iterator& __it); void erase(const_iterator __first, const_iterator __last); void resize(size_type __num_elements_hint); void clear(); private: //返回大于n的最小素數 //實際上調用__stl_next_prime(__n); size_type _M_next_size(size_type __n) const { return __stl_next_prime(__n); } //預留空間,并將其初始化為0 void _M_initialize_buckets(size_type __n) { //返回大于n的最小素數__n_buckets const size_type __n_buckets = _M_next_size(__n); //這里調用vector的成員函數reserve //reserve該函數功能是改變可用空間的大小 //Requests that the vector capacity be at least enough to contain __n_buckets elements. _M_buckets.reserve(__n_buckets); //調用vector的插入函數insert //在原始end后面連續插入__n_buckets個0 _M_buckets.insert(_M_buckets.end(), __n_buckets, (_Node*) 0); _M_num_elements = 0; } //獲取鍵值key在桶子的位置 size_type _M_bkt_num_key(const key_type& __key) const { return _M_bkt_num_key(__key, _M_buckets.size()); } //獲取在桶子的序號，也就是鍵值 //輸入參數是實值value size_type _M_bkt_num(const value_type& __obj) const { return _M_bkt_num_key(_M_get_key(__obj)); } size_type _M_bkt_num_key(const key_type& __key, size_t __n) const { return _M_hash(__key) % __n;//采用除法取余hash函數 } size_type _M_bkt_num(const value_type& __obj, size_t __n) const { return _M_bkt_num_key(_M_get_key(__obj), __n); } //分配節點空間，并構造對象 _Node* _M_new_node(const value_type& __obj) { _Node* __n = _M_get_node(); __n->_M_next = 0; __STL_TRY { construct(&__n->_M_val, __obj); return __n; } __STL_UNWIND(_M_put_node(__n)); } //析構對象，并釋放空間 void _M_delete_node(_Node* __n) { destroy(&__n->_M_val); _M_put_node(__n); } void _M_erase_bucket(const size_type __n, _Node* __first, _Node* __last); void _M_erase_bucket(const size_type __n, _Node* __last); void _M_copy_from(const hashtable& __ht); }; //前綴operator++重載，前進一個list節點 template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> _Hashtable_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>& _Hashtable_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>::operator++() { const _Node* __old = _M_cur; _M_cur = _M_cur->_M_next;//若存在，則返回 //若當前節點為空，則需前進到下一個桶子的節點 if (!_M_cur) { //根據元素值，定位出下一個bucket的位置，其起始位置就是我們的目的地 size_type __bucket = _M_ht->_M_bkt_num(__old->_M_val); while (!_M_cur && ++__bucket < _M_ht->_M_buckets.size()) _M_cur = _M_ht->_M_buckets[__bucket]; } return *this; } //后綴operator++重載 template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline _Hashtable_iterator<_Val,_Key,_HF,_ExK,_EqK,_All> _Hashtable_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>::operator++(int) { iterator __tmp = *this; ++*this;//調用operator++ return __tmp; } template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> _Hashtable_const_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>& _Hashtable_const_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>::operator++() { const _Node* __old = _M_cur; _M_cur = _M_cur->_M_next; if (!_M_cur) { size_type __bucket = _M_ht->_M_bkt_num(__old->_M_val); while (!_M_cur && ++__bucket < _M_ht->_M_buckets.size()) _M_cur = _M_ht->_M_buckets[__bucket]; } return *this; } template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline _Hashtable_const_iterator<_Val,_Key,_HF,_ExK,_EqK,_All> _Hashtable_const_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>::operator++(int) { const_iterator __tmp = *this; ++*this; return __tmp; } #ifndef __STL_CLASS_PARTIAL_SPECIALIZATION template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline forward_iterator_tag iterator_category(const _Hashtable_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>&) { return forward_iterator_tag(); } template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline _Val* value_type(const _Hashtable_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>&) { return (_Val*) 0; } template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline hashtable<_Val,_Key,_HF,_ExK,_EqK,_All>::difference_type* distance_type(const _Hashtable_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>&) { return (hashtable<_Val,_Key,_HF,_ExK,_EqK,_All>::difference_type*) 0; } template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline forward_iterator_tag iterator_category(const _Hashtable_const_iterator<_Val,_Key,_HF, _ExK,_EqK,_All>&) { return forward_iterator_tag(); } template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline _Val* value_type(const _Hashtable_const_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>&) { return (_Val*) 0; } template <class _Val, class _Key, class _HF, class _ExK, class _EqK, class _All> inline hashtable<_Val,_Key,_HF,_ExK,_EqK,_All>::difference_type* distance_type(const _Hashtable_const_iterator<_Val,_Key,_HF,_ExK,_EqK,_All>&) { return (hashtable<_Val,_Key,_HF,_ExK,_EqK,_All>::difference_type*) 0; } #endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */ template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> bool operator==(const hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>& __ht1, const hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>& __ht2) { typedef typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::_Node _Node; if (__ht1._M_buckets.size() != __ht2._M_buckets.size()) return false; for (int __n = 0; __n < __ht1._M_buckets.size(); ++__n) { _Node* __cur1 = __ht1._M_buckets[__n]; _Node* __cur2 = __ht2._M_buckets[__n]; for ( ; __cur1 && __cur2 && __cur1->_M_val == __cur2->_M_val; __cur1 = __cur1->_M_next, __cur2 = __cur2->_M_next) {} if (__cur1 || __cur2) return false; } return true; } #ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> inline bool operator!=(const hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>& __ht1, const hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>& __ht2) { return !(__ht1 == __ht2); } template <class _Val, class _Key, class _HF, class _Extract, class _EqKey, class _All> inline void swap(hashtable<_Val, _Key, _HF, _Extract, _EqKey, _All>& __ht1, hashtable<_Val, _Key, _HF, _Extract, _EqKey, _All>& __ht2) { __ht1.swap(__ht2); } #endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */ //插入元素，不需要重新調整內存空間,不允許存在重復元素 template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> pair<typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::iterator, bool> hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::insert_unique_noresize(const value_type& __obj) { //獲取待插入元素在hashtable中的桶子位置 const size_type __n = _M_bkt_num(__obj); _Node* __first = _M_buckets[__n]; //判斷hashtable中是否存在與之相等的鍵值元素 //若存在則不插入 //否則插入該元素 for (_Node* __cur = __first; __cur; __cur = __cur->_M_next) if (_M_equals(_M_get_key(__cur->_M_val), _M_get_key(__obj))) return pair<iterator, bool>(iterator(__cur, this), false); //把元素插入到第一個節點位置 _Node* __tmp = _M_new_node(__obj); __tmp->_M_next = __first; _M_buckets[__n] = __tmp; ++_M_num_elements; return pair<iterator, bool>(iterator(__tmp, this), true); } //插入元素，允許重復,不需要分配新的空間 //也就是說有足夠的空間 template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::iterator hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::insert_equal_noresize(const value_type& __obj) { //獲取待插入元素在hashtable中的桶子位置 const size_type __n = _M_bkt_num(__obj); _Node* __first = _M_buckets[__n]; for (_Node* __cur = __first; __cur; __cur = __cur->_M_next) //若存在鍵值相同的元素，則插在相同元素下一個位置 if (_M_equals(_M_get_key(__cur->_M_val), _M_get_key(__obj))) { _Node* __tmp = _M_new_node(__obj);//創建新節點 __tmp->_M_next = __cur->_M_next;//將新節點插在當前節點之后 __cur->_M_next = __tmp; ++_M_num_elements;//節點數加1 return iterator(__tmp, this);//返回指向新增節點迭代器 } //若不存在相同鍵值的元素,則插在第一個位置 _Node* __tmp = _M_new_node(__obj);//創建新節點 __tmp->_M_next = __first;//插入在鏈表表頭 _M_buckets[__n] = __tmp; ++_M_num_elements;//節點數加1 return iterator(__tmp, this);//返回指向新增節點的迭代器 } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::reference hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::find_or_insert(const value_type& __obj) { resize(_M_num_elements + 1); size_type __n = _M_bkt_num(__obj); _Node* __first = _M_buckets[__n]; for (_Node* __cur = __first; __cur; __cur = __cur->_M_next) if (_M_equals(_M_get_key(__cur->_M_val), _M_get_key(__obj))) return __cur->_M_val; _Node* __tmp = _M_new_node(__obj); __tmp->_M_next = __first; _M_buckets[__n] = __tmp; ++_M_num_elements; return __tmp->_M_val; } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> pair<typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::iterator, typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::iterator> hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::equal_range(const key_type& __key) { typedef pair<iterator, iterator> _Pii; const size_type __n = _M_bkt_num_key(__key); for (_Node* __first = _M_buckets[__n]; __first; __first = __first->_M_next) if (_M_equals(_M_get_key(__first->_M_val), __key)) { for (_Node* __cur = __first->_M_next; __cur; __cur = __cur->_M_next) if (!_M_equals(_M_get_key(__cur->_M_val), __key)) return _Pii(iterator(__first, this), iterator(__cur, this)); for (size_type __m = __n + 1; __m < _M_buckets.size(); ++__m) if (_M_buckets[__m]) return _Pii(iterator(__first, this), iterator(_M_buckets[__m], this)); return _Pii(iterator(__first, this), end()); } return _Pii(end(), end()); } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> pair<typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::const_iterator, typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::const_iterator> hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::equal_range(const key_type& __key) const { typedef pair<const_iterator, const_iterator> _Pii; const size_type __n = _M_bkt_num_key(__key); for (const _Node* __first = _M_buckets[__n] ; __first; __first = __first->_M_next) { if (_M_equals(_M_get_key(__first->_M_val), __key)) { for (const _Node* __cur = __first->_M_next; __cur; __cur = __cur->_M_next) if (!_M_equals(_M_get_key(__cur->_M_val), __key)) return _Pii(const_iterator(__first, this), const_iterator(__cur, this)); for (size_type __m = __n + 1; __m < _M_buckets.size(); ++__m) if (_M_buckets[__m]) return _Pii(const_iterator(__first, this), const_iterator(_M_buckets[__m], this)); return _Pii(const_iterator(__first, this), end()); } } return _Pii(end(), end()); } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> typename hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::size_type hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::erase(const key_type& __key) { const size_type __n = _M_bkt_num_key(__key); _Node* __first = _M_buckets[__n]; size_type __erased = 0; if (__first) { _Node* __cur = __first; _Node* __next = __cur->_M_next; while (__next) { if (_M_equals(_M_get_key(__next->_M_val), __key)) { __cur->_M_next = __next->_M_next; _M_delete_node(__next); __next = __cur->_M_next; ++__erased; --_M_num_elements; } else { __cur = __next; __next = __cur->_M_next; } } if (_M_equals(_M_get_key(__first->_M_val), __key)) { _M_buckets[__n] = __first->_M_next; _M_delete_node(__first); ++__erased; --_M_num_elements; } } return __erased; } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::erase(const iterator& __it) { _Node* __p = __it._M_cur; if (__p) { const size_type __n = _M_bkt_num(__p->_M_val); _Node* __cur = _M_buckets[__n]; if (__cur == __p) { _M_buckets[__n] = __cur->_M_next; _M_delete_node(__cur); --_M_num_elements; } else { _Node* __next = __cur->_M_next; while (__next) { if (__next == __p) { __cur->_M_next = __next->_M_next; _M_delete_node(__next); --_M_num_elements; break; } else { __cur = __next; __next = __cur->_M_next; } } } } } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::erase(iterator __first, iterator __last) { size_type __f_bucket = __first._M_cur ? _M_bkt_num(__first._M_cur->_M_val) : _M_buckets.size(); size_type __l_bucket = __last._M_cur ? _M_bkt_num(__last._M_cur->_M_val) : _M_buckets.size(); if (__first._M_cur == __last._M_cur) return; else if (__f_bucket == __l_bucket) _M_erase_bucket(__f_bucket, __first._M_cur, __last._M_cur); else { _M_erase_bucket(__f_bucket, __first._M_cur, 0); for (size_type __n = __f_bucket + 1; __n < __l_bucket; ++__n) _M_erase_bucket(__n, 0); if (__l_bucket != _M_buckets.size()) _M_erase_bucket(__l_bucket, __last._M_cur); } } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> inline void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::erase(const_iterator __first, const_iterator __last) { erase(iterator(const_cast<_Node*>(__first._M_cur), const_cast<hashtable*>(__first._M_ht)), iterator(const_cast<_Node*>(__last._M_cur), const_cast<hashtable*>(__last._M_ht))); } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> inline void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::erase(const const_iterator& __it) { erase(iterator(const_cast<_Node*>(__it._M_cur), const_cast<hashtable*>(__it._M_ht))); } //調整hashtable的容量 //新的容量大小為__num_elements_hint template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::resize(size_type __num_elements_hint) { //hashtable原始大小 const size_type __old_n = _M_buckets.size(); if (__num_elements_hint > __old_n) {//若新的容量大小比原始的大 //查找不低于__num_elements_hint的最小素數 const size_type __n = _M_next_size(__num_elements_hint); if (__n > __old_n) { //創建新的線性表,容量為__n，只是起到中介作用 vector<_Node*, _All> __tmp(__n, (_Node*)(0), _M_buckets.get_allocator()); __STL_TRY {//以下是復制數據 for (size_type __bucket = 0; __bucket < __old_n; ++__bucket) { _Node* __first = _M_buckets[__bucket]; while (__first) { //獲取實值在新桶子的鍵值位置 size_type __new_bucket = _M_bkt_num(__first->_M_val, __n); //這個只是為了方便while循環里面__first的迭代 _M_buckets[__bucket] = __first->_M_next; //將當前節點插入到新的桶子__new_bucket里面,成為list的第一個節點 __first->_M_next = __tmp[__new_bucket];//__first->_M_next指向null指針,因為新桶子是空的 __tmp[__new_bucket] = __first;//新桶子對應鍵值指向第一個節點 __first = _M_buckets[__bucket];//更新當前指針 } } _M_buckets.swap(__tmp);//交換內容 } # ifdef __STL_USE_EXCEPTIONS catch(...) {//釋放臨時hashtable的線性表tmp for (size_type __bucket = 0; __bucket < __tmp.size(); ++__bucket) { while (__tmp[__bucket]) { _Node* __next = __tmp[__bucket]->_M_next; _M_delete_node(__tmp[__bucket]); __tmp[__bucket] = __next; } } throw; } # endif /* __STL_USE_EXCEPTIONS */ } } } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::_M_erase_bucket(const size_type __n, _Node* __first, _Node* __last) { _Node* __cur = _M_buckets[__n]; if (__cur == __first) _M_erase_bucket(__n, __last); else { _Node* __next; for (__next = __cur->_M_next; __next != __first; __cur = __next, __next = __cur->_M_next) ; while (__next != __last) { __cur->_M_next = __next->_M_next; _M_delete_node(__next); __next = __cur->_M_next; --_M_num_elements; } } } template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::_M_erase_bucket(const size_type __n, _Node* __last) { _Node* __cur = _M_buckets[__n]; while (__cur != __last) { _Node* __next = __cur->_M_next; _M_delete_node(__cur); __cur = __next; _M_buckets[__n] = __cur; --_M_num_elements; } } //清空hashtable，但是沒有釋放bucket vector空間 template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All>::clear() { for (size_type __i = 0; __i < _M_buckets.size(); ++__i) {//遍歷每個桶子 _Node* __cur = _M_buckets[__i];//當前節點為桶子的第一個節點 while (__cur != 0) {//遍歷桶子維護的鏈表，并釋放每個鏈表節點 _Node* __next = __cur->_M_next; _M_delete_node(__cur); __cur = __next; } _M_buckets[__i] = 0;//桶子鏈表為空 } _M_num_elements = 0;//鏈表節點數為0 } //拷貝hashtable對象 //實現機制：首先把原始對象清空，再把空間變成被復制對象__ht一樣的大小 //最后把__ht的內容復制到目標對象 template <class _Val, class _Key, class _HF, class _Ex, class _Eq, class _All> void hashtable<_Val,_Key,_HF,_Ex,_Eq,_All> ::_M_copy_from(const hashtable& __ht) {//_M_buckets是vector維護的，可以調用vector的成員函數 _M_buckets.clear();//清空線性表調用vector::clear() _M_buckets.reserve(__ht._M_buckets.size());//把線性表內存空間變成與__ht一樣大 //在_M_buckets vector尾端插入size個元素，初始值為空指針 //注意：此時_M_buckets vector為空，即尾端也是起始端 _M_buckets.insert(_M_buckets.end(), __ht._M_buckets.size(), (_Node*) 0); __STL_TRY {//開始復制操作 for (size_type __i = 0; __i < __ht._M_buckets.size(); ++__i) { //復制vector的每一個元素(是指向hashtable節點指針) const _Node* __cur = __ht._M_buckets[__i]; if (__cur) { _Node* __copy = _M_new_node(__cur->_M_val); _M_buckets[__i] = __copy; //針對每一個hashtable節點對應的list，復制list的每一個節點 for (_Node* __next = __cur->_M_next; __next; __cur = __next, __next = __cur->_M_next) { __copy->_M_next = _M_new_node(__next->_M_val); __copy = __copy->_M_next; } } } _M_num_elements = __ht._M_num_elements;//更新節點個數 } __STL_UNWIND(clear()); } __STL_END_NAMESPACE #endif /* __SGI_STL_INTERNAL_HASHTABLE_H */ // Local Variables: // mode:C++ // End: ~~~ 參考資料：《STL源碼剖析》侯捷