STL源码解析-04序列容器-01vector

#include <iostream>

#include <vector>

 

using namespace std;

 

*****************************************************

 * vector中的数据结构主要是三个指针：

 * start；空间的头

 * finish:使用空间的尾

 * end_of_storage:可用空间的尾

 * 指示的范围左闭右开,内存是一块连续的地址。

 * ************************************************

 

int main()

{

    vector<int> iv0;                                //初始几个，分配的capacity就是几个。

    cout << "max_size:" << iv0.max_size() << endl;  //只与系统等设备有关

    cout << "size:" << iv0.size() << endl;          //没有初始化值，为0.

    cout << "capacity:" <<iv0.capacity() << endl;   //0

 

    iv0.push_back(1);

    //如果有空余空间，直接增大finish指针；

    //没有，如果size是0，申请大小为1，如果大于0，则申请大小是该值的两倍,

    //申请结束之后，使用uninitialized_copy函数，将原内容拷贝到新地址，再将插入数据拷贝过来，

    //析构并释放原地址内容，调整start,finish,end_of_storage指针。

    cout << "max_size:" << iv0.max_size() << endl;  

    cout << "size:" << iv0.size() << endl;          //1

    cout << "capacity:" <<iv0.capacity() << endl;   //1

 

    iv0.push_back(2);

    cout << "max_size:" << iv0.max_size() << endl;  

    cout << "size:" << iv0.size() << endl;          //2

    cout << "capacity:" <<iv0.capacity() << endl;   //2

    

    iv0.push_back(3);

    cout << "max_size:" << iv0.max_size() << endl;

    cout << "size:" << iv0.size() << endl;          //3

    cout << "capacity:" <<iv0.capacity() << endl;   //4,不够变为原来的两倍

 

    iv0.push_back(4);

    cout << "max_size:" << iv0.max_size() << endl;

    cout << "size:" << iv0.size() << endl;          //4

    cout << "capacity:" <<iv0.capacity() << endl;   //4

 

    iv0.push_back(5);

    cout << "max_size:" << iv0.max_size() << endl;

    cout << "size:" << iv0.size() << endl;          //5

    cout << "capacity:" <<iv0.capacity() << endl;   //8

 

    vector<int> iv3(3,10);

    cout << "max_size:" << iv3.max_size() << endl;

    cout << "size:" << iv3.size() << endl;          //3

    cout << "capacity:" <<iv3.capacity() << endl;   //3 ,初始化时，空间与初始值一样。

    

    iv3.pop_back();

    //finish指针--,在调用destroy(finish);

    cout << "max_size:" << iv3.max_size() << endl;

    cout << "size:" << iv3.size() << endl;          //2

    cout << "capacity:" <<iv3.capacity() << endl;   //3,POP掉之后，capacity不变。

 

    iv3.clear();

    cout << "max_size:" << iv3.max_size() << endl;

    cout << "size:" << iv3.size() << endl;          //0,只是将size减小，capacity不变。

    cout << "capacity:" <<iv3.capacity() << endl;   //3

    

    //erase(iterator first, iterator last)

    //1,i = copy(last,finish,first),将后面的元素覆盖前面的元素；

    //2,destroy(i, finish)，销毁多余对象；

    //3,finish = finish- (last - first)，移动finish指针。

 

    //clear

    //erase(first(), end())

 

    //insert(iteraor, n, t),插入n个t。

    //由于vector是动态分配空间，所以必须考虑capacity是否满足新增加元素的要求。

    //if n!=0 进行下面操作，n==0不管

    //if end_of_storage-finish >= n,说明够

    //  计算插入点之后的元素个数:elems = finish - iterator

    //  if elems>n 后面的元素多

    //      uninitialized_copy(finish-n, finish, finish),将finishi之前的n个元素copy到finish之后。

    //      copy_backward(iteraor, old_finish-n, old_finish),将iterator开始的elems-n个元素，copy到finish之前。

    //      fill(iterator, iterator+n, t);

    //  else 后面的元素少

    //      uninitialized_fill_n(finish, n-elems, t)，先将多余的n-elems个元素在finishi之后构造

    //      uninitialized_copy(iterator,old_finish,finish),将elems个元素拷贝到新的finish之后。

    //      fill(iterator, iterator+n, t)

    //else 存储空间不够

    //  按照两倍开辟新的空间

    //  new_finish = uninitialized_copy(start, iterator, new_start);拷贝start到iterator的元素

    //  new_finish = uninitialized_fill_n(new_finish,n,t),填充插入的n个元素

    //  new_finish = uninitialized_cop(iterator, finish, new_finish)，拷贝iterator到finish的元素

    //

    //  destroy(start, finish),销毁原来的对象

    //  deallocate()，回收内存地址

    //

    //  设置start为新的start等。

    

    return 0;

}

转载于:https://www.cnblogs.com/shaotenghan/archive/2011/12/02/2272128.html