STL源码解析-02配置器-01使用

#include <iostream>

 

using namespace std;

 

class test{ 

    public:

        int value;

        test() {cout << "construct value: none\n";}

        test(const test& mt) {value = mt.value;cout << "copy constructor value:" << value << endl;}

        ~test() {cout << "~test" << endl;}

};

 

int main()

{

    allocator<int> iall;//可以用已有allocator进行构造

    

    int temp1;

    cout << "the address of variable temp1: " << iall.address(temp1) << endl;       //传入变量的引用，返回变量的地址

    cout << "after the first value, the max_size of the allocator: " << iall.max_size() << endl; //返回allocator最大能分配的空间，不变

    int temp2;

    cout << "the address of variable temp2: " << iall.address(temp2) << endl;

    cout << "after the second value, the max_size of the allocator: " << iall.max_size() << endl;

 

    int *p = iall.allocate(3); //在堆中分配大小,不做其他初始化事情,大小为4的倍数。

    *(p+1) = 34;

    *(p+200) = 77;

    cout << "allocate 10, the second value is :" <<*(p+200)<< endl;

    cout << "the address of variable p: " << iall.address(*p) << endl;

    cout << "the address of variable p+9: " << iall.address(*(p+9)) << endl;

    cout << "after the third value, the max_size of the allocator: " << iall.max_size() << endl;

    iall.deallocate(p,1); //收回指定的大小，并没有释放空间，只是将大小放到相应的lsit下，指定的大小没啥用啊，按照申请时的大小回收。

    *(p+7) = 78;

    cout << "deallocate 5, the seven value is :" <<*(p+7)<< endl;

 

    int *q = iall.allocate(7);//如果p与q申请的地址相同，且p已经deallocate掉，此时q的地址是p的地址。

    cout << "the address of variable p: " << iall.address(*q) << endl;

 

    test *pt;

    test t;

    cout << "construct test object over.\n";

    t.value = 54;

    allocator<test> tall;

    pt = tall.allocate(1);//先给指针分配好空间，再调用construct函数,此时不对对象实例化。

    cout << "the address of variable pt: " << tall.address(*pt) << endl;

    tall.construct(pt,t);//给传入的指针，调用拷贝构造函数

    tall.destroy(pt);//调用指针的析构函数

    cout << "the second value is :" <<*(p)<< endl;

    

    cout << "~over\n"; 

    return 0;

}