vector源码剖析

一、vector定义摘要：

template <class T, class Alloc = alloc>
class vector {
public:typedef T                   value_type;typedef value_type*         pointer;typedef const value_type*   const_pointer;typedef value_type*         iterator;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;
protected:typedef simple_alloc<value_type, Alloc> data_allocator;iterator start;iterator finish;iterator end_of_storage;
public:iterator begin() { return start; }const_iterator begin() const { return start; }iterator end() { return finish; }const_iterator end() const { return finish; }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) {}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()); }
};

二、构造函数：

vector() : start(0), finish(0), end_of_storage(0) {}
vector(size_type n, const T& value) { fill_initialize(n, value); }template <class T, class Alloc>
void vector<T, Alloc>::::fill_initialize(size_type n, const T& value)
{start = allocate_and_fill(n, value);finish = start + n;end_of_storage = finish;
}template <class T, class Alloc>
iterator vector<T, Alloc>::allocate_and_fill(size_type n, const T& x)
{iterator result = data_allocator::allocate(n);uninitialized_fill_n(result, n, x);return result;
}vector(const vector<T, Alloc>& x)
{start = allocate_and_copy(x.end() - x.begin(), x.begin(), x.end());finish = start + (x.end() - x.begin());end_of_storage = finish;
}iterator allocate_and_copy(size_type n, const_iterator first, const_iterator last)
{iterator result = data_allocator::allocate(n);uninitialized_copy(first, last, result);return result;
}

三、析构函数：

template <class T, class Alloc>
vector<T, Alloc>::~vector()
{destroy(start, finish);deallocate();
}template <class T, class Alloc>
void vector<T, Alloc>::deallocate()
{if (start)data_allocator::deallocate(start, end_of_storage - start);
}

四、push_back

template <class T, class Alloc>
void vector<T>::push_back(const T& x) //重点函数
{if (finish != end_of_storage) //还有备用空间{construct(finish, x);  //全局函数++finish;}elseinsert_aux(end(), x); //已经没有备用空间
}template <class T, class Alloc>
void vector<T>::insert_aux(iterator position, const T& x)
{if (finish != end_of_storage) //还有备用空间{construct(finish, *(finish - 1));++finish;T x_copy = x;std::copy_backward(position, finish - 2, finish - 1);*position = x_copy;}else //没有备用空间了{const size_type old_size = size();const size_type len = old_size != 0 ? 2 * old_size : 1;//以上配置原则：如果原大小为0，则配置1//如果原大小不为0，则配置原大小2倍//前半段用来放置原数据，后半段放置新数据iterator new_start = data_allocator::allocate(len);iterator new_finish = new_start;new_finish = uninitialized_copy(start, position, new_start);construct(new_finish, x);++new_finish;new_finish = uninitialized_copy(position, finish, new_finish);destroy(begin(), end());deallocate();start = new_start;finish = new_finish;end_of_storage = new_start + len;}
}

vetor的元素操作：pop_back、erase、clear、insert

void pop_back()
{--finish;         //将尾标记往前移动一格，表示将放弃尾端元素destroy(finish); //析构函数
}iterator erase(iterator first, iterator last)
{iterator i = copy(last, finish, first);destroy(i, finish);finish = finish - (last - first);return first;
}iterator erase(iterator position)
{if (position + 1 != end())copy(position + 1, finish, position);--finish;destroy(finish);return position;
}void clear() { erase(begin(), end()); }template <class T, class Alloc>
void vector<T, Alloc>::insert(iterator position, size_type n, const T & x)
{if (n != 0) //当n！= 0才进行以下所有操作{if (size_type(end_of_storage - finish) >= n) //备用空间大于等于新增元素{T x_copy = x;const size_type elems_after = finish - position; //计算插入点之后的现有元素个数iterator old_finish = finish;if (elems_after > n) //"插入点之后的现有元素个数"大于"新增元素个数"{uninitialized_copy(finish - n, finish, finish);finish += n;copy_backward(position, old_finish - n, old_finish);fill(position, position + n, x_copy);}else //"插入点之后的现有元素个数"小于等于"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"(那就必须配置额外的内存)//首先决定新长度：旧长度的两倍，或旧长度+新增元素个数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;new_finish = uninitialized_copy(start, position, new_start);new_finish = uninitialized_fill_n(new_finish, n, x);new_finish = uninitialized_copy(position, finish, new_finish);destroy(start, finish);deallocate();start = new_start;finish = new_finish;end_of_storage = new_start + len;}}
}

五、resize、reverse

void resize(size_type new_size, const T& x)
{if (new_size < size())erase(begin() + new_size, end());elseinsert(end(), new_size - size(), x);
}
void resize(size_type new_size) { resize(new_size, T()); }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;}
}iterator allocate_and_copy(size_type n, const_iterator first, const_iterator last)
{iterator result = data_allocator::allocate(n);uninitialized_copy(first, last, result);return result;
}

六、 swap

 void swap(vector<T, Alloc>& x)
{__STD::swap(start, x.start);__STD::swap(finish, x.finish);__STD::swap(end_of_storage, x.end_of_storage);}

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vector源码剖析

一、vector定义摘要：

二、构造函数：

三、析构函数：

四、push_back

vetor的元素操作：pop_back、erase、clear、insert

五、resize、reverse

六、 swap

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vector源码剖析

一、vector定义摘要：

二、构造函数 ：

三、析构函数：

四、push_back

vetor的元素操作：pop_back、erase、clear、insert

五、resize、reverse

六、 swap

vector源码剖析相关推荐

最新文章

热门文章

二、构造函数：