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vector

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描写叙述：

1.迭代器

vector 维护的是一个连续线性空间。它的迭代器是普通指针。

能满足 RandomAccessIterator 全部必要条件：operator*, operator->,operator++,operator--,operator+,

operator-,operator+=,operator-=,operator[]

2.数据结构

vector所採用的数据结构是线性连续空间。

迭代器 start、finish分别表示配置得来的连续空间中眼下已经被使用的范围

迭代器 end_of_storage 指向整块连续空间的尾端

添加新元素时。假设走过当时的容量，则容量会扩充至两倍。

假设两倍容量仍不足，就扩张至足够大的容量。

扩充容量的过程为：又一次配置、元素移动、释放原空间

所谓动态添加大小，并非在原空间之后接续新空间，由于无法保证原空间之后

尚有可供配置的空间。因此。对 vector 的不论什么操作。一旦引起空间又一次配置，

指向原 vector 的全部迭代器就失效了。

演示样例：

vector
     
       V;V.insert(V.begin(), 3);assert(V.size() == 1 && V.capacity() >= 1 && V[0] == 3);
     

源代码：

#ifndef __SGI_STL_INTERNAL_VECTOR_H#define __SGI_STL_INTERNAL_VECTOR_H__STL_BEGIN_NAMESPACE #if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)#pragma set woff 1174#endiftemplate 
     
      class vector {public:  typedef T value_type;  typedef value_type* pointer;  typedef const value_type* const_pointer;  typedef value_type* iterator; //vector 的迭代器是个原生的指针  typedef const value_type* const_iterator;  typedef value_type& reference;  typedef const value_type& const_reference;  typedef size_t size_type;  typedef ptrdiff_t difference_type;#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION  typedef reverse_iterator
      
        const_reverse_iterator;  typedef reverse_iterator
       
         reverse_iterator;#else /* __STL_CLASS_PARTIAL_SPECIALIZATION */  typedef reverse_iterator
        
           const_reverse_iterator;  typedef reverse_iterator
         
                    reverse_iterator;#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */protected:  typedef simple_alloc
          
            data_allocator; //连续空间？ iterator start; //表示眼下使用空间的头 iterator finish; //表示眼下使用空间的尾 iterator end_of_storage; //表示眼下可用空间的尾 void insert_aux(iterator position, const T& x); void deallocate() { if (start) data_allocator::deallocate(start, end_of_storage - start); } // 填充并予以初始化 void fill_initialize(size_type n, const T& value) { start = allocate_and_fill(n, value); finish = start + n; end_of_storage = finish; }public: iterator begin() { return start; } const_iterator begin() const { return start; } iterator end() { return finish; } const_iterator end() const { return finish; } reverse_iterator rbegin() { return reverse_iterator(end()); } const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); } reverse_iterator rend() { return reverse_iterator(begin()); } const_reverse_iterator rend() const { return const_reverse_iterator(begin()); } size_type size() const { return size_type(end() - begin()); } size_type max_size() const { return size_type(-1) / sizeof(T); } size_type capacity() const { return size_type(end_of_storage - begin()); } bool empty() const { return begin() == end(); } reference operator[](size_type n) { return *(begin() + n); } const_reference operator[](size_type n) const { return *(begin() + n); } vector() : start(0), finish(0), end_of_storage(0) {} //构造函数，同意指定 vector 大小 n 和初值 value vector(size_type n, const T& value) { fill_initialize(n, value); } vector(int n, const T& value) { fill_initialize(n, value); } vector(long n, const T& value) { fill_initialize(n, value); } explicit vector(size_type n) { fill_initialize(n, T()); } vector(const vector
           
            & x) { start = allocate_and_copy(x.end() - x.begin(), x.begin(), x.end()); finish = start + (x.end() - x.begin()); end_of_storage = finish; }#ifdef __STL_MEMBER_TEMPLATES template 
            
              vector(InputIterator first, InputIterator last) : start(0), finish(0), end_of_storage(0) { range_initialize(first, last, iterator_category(first)); }#else /* __STL_MEMBER_TEMPLATES */ vector(const_iterator first, const_iterator last) { size_type n = 0; distance(first, last, n); start = allocate_and_copy(n, first, last); finish = start + n; end_of_storage = finish; }#endif /* __STL_MEMBER_TEMPLATES */ ~vector() { destroy(start, finish); deallocate(); } vector
             
              & operator=(const vector
              
               & x); void reserve(size_type n) { if (capacity() < n) { const size_type old_size = size(); iterator tmp = allocate_and_copy(n, start, finish); destroy(start, finish); deallocate(); start = tmp; finish = tmp + old_size; end_of_storage = start + n; } } reference front() { return *begin(); } const_reference front() const { return *begin(); } reference back() { return *(end() - 1); } const_reference back() const { return *(end() - 1); } // void push_back(const T& x) { if (finish != end_of_storage) { //检查是否还有备用空间 construct(finish, x); //有，直接在备用空间上构造元素 ++finish; //调整迭代器 finish } else insert_aux(end(), x); //没有，扩充空间(又一次配置、元素移动、释放原空间) } void swap(vector
               
                & x) { __STD::swap(start, x.start); __STD::swap(finish, x.finish); __STD::swap(end_of_storage, x.end_of_storage); } iterator insert(iterator position, const T& x) { size_type n = position - begin(); if (finish != end_of_storage && position == end()) { construct(finish, x); ++finish; } else insert_aux(position, x); return begin() + n; } iterator insert(iterator position) { return insert(position, T()); }#ifdef __STL_MEMBER_TEMPLATES template 
                
                  void insert(iterator position, InputIterator first, InputIterator last) { range_insert(position, first, last, iterator_category(first)); }#else /* __STL_MEMBER_TEMPLATES */ void insert(iterator position, const_iterator first, const_iterator last);#endif /* __STL_MEMBER_TEMPLATES */ void insert (iterator pos, size_type n, const T& x); void insert (iterator pos, int n, const T& x) { insert(pos, (size_type) n, x); } void insert (iterator pos, long n, const T& x) { insert(pos, (size_type) n, x); } void pop_back() { --finish; //将尾端标记往前移一格，表示将放弃尾端元素 destroy(finish); //析构尾端元素 } //清除 position 指向的元素 iterator erase(iterator position) { if (position + 1 != end()) copy(position + 1, finish, position); --finish; destroy(finish); return position; } //清除[first, last)中的全部元素 iterator erase(iterator first, iterator last) { iterator i = copy(last, finish, first); //将 [last, finish) 指示的元素拷贝至 first 迭代器开头的地方 destroy(i, finish); //析构[i, finish) 里的元素 finish = finish - (last - first); //调整 finish 指示的位置 last - first 表示清除掉了的元素个数 return first; } void resize(size_type new_size, const T& x) { if (new_size < size()) erase(begin() + new_size, end()); else insert(end(), new_size - size(), x); } void resize(size_type new_size) { resize(new_size, T()); } //调用 erase 清除全部元素 void clear() { erase(begin(), end()); }protected: //配置而后填充 iterator allocate_and_fill(size_type n, const T& x) { iterator result = data_allocator::allocate(n); //配置 n 个元素空间 __STL_TRY { uninitialized_fill_n(result, n, x); //全局函数。全依据 result 的类型特性(type traits)决定使用算法 fill_n() 或重复调用 construct() 来完毕任务 return result; } __STL_UNWIND(data_allocator::deallocate(result, n)); }#ifdef __STL_MEMBER_TEMPLATES template 
                 
                   iterator allocate_and_copy(size_type n, ForwardIterator first, ForwardIterator last) { iterator result = data_allocator::allocate(n); __STL_TRY { uninitialized_copy(first, last, result); return result; } __STL_UNWIND(data_allocator::deallocate(result, n)); }#else /* __STL_MEMBER_TEMPLATES */ iterator allocate_and_copy(size_type n, const_iterator first, const_iterator last) { iterator result = data_allocator::allocate(n); __STL_TRY { uninitialized_copy(first, last, result); return result; } __STL_UNWIND(data_allocator::deallocate(result, n)); }#endif /* __STL_MEMBER_TEMPLATES */#ifdef __STL_MEMBER_TEMPLATES template 
                  
                    void range_initialize(InputIterator first, InputIterator last, input_iterator_tag) { for ( ; first != last; ++first) push_back(*first); } // This function is only called by the constructor. We have to worry // about resource leaks, but not about maintaining invariants. template 
                   
                     void range_initialize(ForwardIterator first, ForwardIterator last, forward_iterator_tag) { size_type n = 0; distance(first, last, n); start = allocate_and_copy(n, first, last); finish = start + n; end_of_storage = finish; } template 
                    
                      void range_insert(iterator pos, InputIterator first, InputIterator last, input_iterator_tag); template 
                     
                       void range_insert(iterator pos, ForwardIterator first, ForwardIterator last, forward_iterator_tag);#endif /* __STL_MEMBER_TEMPLATES */};template 
                      
                       inline bool operator==(const vector
                       
                        & x, const vector
                        
                         & y) { return x.size() == y.size() && equal(x.begin(), x.end(), y.begin());}template 
                         
                          inline bool operator<(const vector
                          
                           & x, const vector
                           
                            & y) { return lexicographical_compare(x.begin(), x.end(), y.begin(), y.end());}#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDERtemplate 
                            
                             inline void swap(vector
                             
                              & x, vector
                              
                               & y) { x.swap(y);}#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */template 
                               
                                vector
                                
                                 & vector
                                 
                                  ::operator=(const vector
                                  
                                   & x) { if (&x != this) { if (x.size() > capacity()) { iterator tmp = allocate_and_copy(x.end() - x.begin(), x.begin(), x.end()); destroy(start, finish); deallocate(); start = tmp; end_of_storage = start + (x.end() - x.begin()); } else if (size() >= x.size()) { iterator i = copy(x.begin(), x.end(), begin()); destroy(i, finish); } else { copy(x.begin(), x.begin() + size(), start); uninitialized_copy(x.begin() + size(), x.end(), finish); } finish = start + x.size(); } return *this;}template 
                                   
                                    void vector
                                    
                                     ::insert_aux(iterator position, const T& x) { if (finish != end_of_storage) { // 不是备用空间不够才会调用 insert_aux 来插入元素吗？ 为什么还会出现 finish != end_of_storage 的情况 ？ // --> 除了 push_back 不够空间时会调用 insert_aux，正常的 insert 也是调用 insert_aux 实现的。
                                    
                                   
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

//为什么不直接 copy_backward(position, finish - 1, finish)。 然后 *position = x_copy 呢？ construct(finish, *(finish - 1)); ++finish; T x_copy = x; copy_backward(position, finish - 2, finish - 1); *position = x_copy; } else { //无备用空间 position == finish const size_type old_size = size(); const size_type len = old_size != 0 ? 2 * old_size : 1; //假设原大小为0。则配置1个元素大小的空间，否则配置原大小两倍的空间 iterator new_start = data_allocator::allocate(len); //实际配置 iterator new_finish = new_start; __STL_TRY { //将原空间的全部内容拷贝到新空间 positition new_finish = uninitialized_copy(start, position, new_start); //为新元素设定初值 x construct(new_finish, x); //调整迭代器 finish ++new_finish; //？？我认为以下这行代码没用。由于无备用空间的情况，position == finish new_finish = uninitialized_copy(position, finish, new_finish); } # ifdef __STL_USE_EXCEPTIONS catch(...) { //异常居然能够用三个小点 ... ?

?

//回滚 destroy(new_start, new_finish); data_allocator::deallocate(new_start, len); throw; } # endif /* __STL_USE_EXCEPTIONS */ //析构并释放原空间 destroy(begin(), end()); deallocate(); //调整迭代器。指向新 vector start = new_start; finish = new_finish; end_of_storage = new_start + len; } } template <class T, class Alloc> //从 position 開始，插入 n 个元素，元素初值为 x void vector<T, Alloc>::insert(iterator position, size_type n, const T& x) { if (n != 0) { // 当 n != 0 才进行以下全部操作 if (size_type(end_of_storage - finish) >= n) { //备用空间大于新增元素个数 T x_copy = x; const size_type elems_after = finish - position; //插入点之后的的现有元素个数 iterator old_finish = finish; if (elems_after > n) { //"插入点之后的的现有元素个数"大于"新增元素个数" //空间还没初始化时用 uninitialized_copy 。 已经初始化了用 copy_backward uninitialized_copy(finish - n, finish, finish); finish += n; copy_backward(position, old_finish - n, old_finish); fill(position, position + n, x_copy); //从插入点開始填入新值 } else { //"插入点之后的的现有元素个数"小于"新增元素个数" uninitialized_fill_n(finish, n - elems_after, x_copy); finish += n - elems_after; uninitialized_copy(position, old_finish, finish); finish += elems_after; fill(position, old_finish, x_copy); } } else {//备用空间小于新增元素个数 const size_type old_size = size(); // 首先决定新长度：旧长度的两倍或旧长度+新元素个数，这两个中取最大值 const size_type len = old_size + max(old_size, n); iterator new_start = data_allocator::allocate(len); iterator new_finish = new_start; __STL_TRY { //先用 uninitialized_copy 将旧 vector 的插入点之前的元素拷贝到新空间 new_finish = uninitialized_copy(start, position, new_start); //再用 uninitialized_fill_n 将新增元素填入新空间 new_finish = uninitialized_fill_n(new_finish, n, x); //最后再用 uninitialized_copy 将旧 vector 的插入点之后的元素拷贝到新空间 new_finish = uninitialized_copy(position, finish, new_finish); } # ifdef __STL_USE_EXCEPTIONS catch(...) { destroy(new_start, new_finish); data_allocator::deallocate(new_start, len); throw; } # endif /* __STL_USE_EXCEPTIONS */ //清除并释放旧的 vector destroy(start, finish); deallocate(); //调整标记 start = new_start; finish = new_finish; end_of_storage = new_start + len; } } } #ifdef __STL_MEMBER_TEMPLATES template <class T, class Alloc> template <class InputIterator> void vector<T, Alloc>::range_insert(iterator pos, InputIterator first, InputIterator last, input_iterator_tag) { for ( ; first != last; ++first) { pos = insert(pos, *first); ++pos; } } template <class T, class Alloc> template <class ForwardIterator> void vector<T, Alloc>::range_insert(iterator position, ForwardIterator first, ForwardIterator last, forward_iterator_tag) { if (first != last) { size_type n = 0; distance(first, last, n); if (size_type(end_of_storage - finish) >= n) { const size_type elems_after = finish - position; iterator old_finish = finish; if (elems_after > n) { uninitialized_copy(finish - n, finish, finish); finish += n; copy_backward(position, old_finish - n, old_finish); copy(first, last, position); } else { ForwardIterator mid = first; advance(mid, elems_after); uninitialized_copy(mid, last, finish); finish += n - elems_after; uninitialized_copy(position, old_finish, finish); finish += elems_after; copy(first, mid, position); } } else { const size_type old_size = size(); const size_type len = old_size + max(old_size, n); iterator new_start = data_allocator::allocate(len); iterator new_finish = new_start; __STL_TRY { new_finish = uninitialized_copy(start, position, new_start); new_finish = uninitialized_copy(first, last, new_finish); new_finish = uninitialized_copy(position, finish, new_finish); } # ifdef __STL_USE_EXCEPTIONS catch(...) { destroy(new_start, new_finish); data_allocator::deallocate(new_start, len); throw; } # endif /* __STL_USE_EXCEPTIONS */ destroy(start, finish); deallocate(); start = new_start; finish = new_finish; end_of_storage = new_start + len; } } } #else /* __STL_MEMBER_TEMPLATES */ template <class T, class Alloc> void vector<T, Alloc>::insert(iterator position, const_iterator first, const_iterator last) { if (first != last) { size_type n = 0; distance(first, last, n); if (size_type(end_of_storage - finish) >= n) { const size_type elems_after = finish - position; iterator old_finish = finish; if (elems_after > n) { uninitialized_copy(finish - n, finish, finish); finish += n; copy_backward(position, old_finish - n, old_finish); copy(first, last, position); } else { uninitialized_copy(first + elems_after, last, finish); finish += n - elems_after; uninitialized_copy(position, old_finish, finish); finish += elems_after; copy(first, first + elems_after, position); } } else { const size_type old_size = size(); const size_type len = old_size + max(old_size, n); iterator new_start = data_allocator::allocate(len); iterator new_finish = new_start; __STL_TRY { new_finish = uninitialized_copy(start, position, new_start); new_finish = uninitialized_copy(first, last, new_finish); new_finish = uninitialized_copy(position, finish, new_finish); } # ifdef __STL_USE_EXCEPTIONS catch(...) { destroy(new_start, new_finish); data_allocator::deallocate(new_start, len); throw; } # endif /* __STL_USE_EXCEPTIONS */ destroy(start, finish); deallocate(); start = new_start; finish = new_finish; end_of_storage = new_start + len; } } } #endif /* __STL_MEMBER_TEMPLATES */ #if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32) #pragma reset woff 1174 #endif __STL_END_NAMESPACE #endif /* __SGI_STL_INTERNAL_VECTOR_H */ // Local Variables: // mode:C++ // End: