Android 智能指针学习 一

Android5.1 中智能指针涉及的文件如下：

system/core/include/utils/RefBase.h

system/core/libutils/RefBase.cpp

system/core/include/utils/StrongPointer.h

在学习Android的智能指针时，对于模板的使用不太清楚，于是我将sp类精简了一下，大概看一下在赋值和初始化的时候的函数调用关系：

 #include <iostream>

 using namespace std;

 template<typename T>
 class sp {
 public:
     inline sp() {};
     sp(T* other);
     sp(const sp<T>& other);
     template<typename U> sp(U* other);
     template<typename U> sp(const sp<U>& other);

     ~sp();

     sp& operator = (T* other);
     sp& operator = (const sp<T>& other);
     template<typename U> sp& operator = (const sp<U>& other);
     template<typename U> sp& operator = (U* other);
 };

 template<typename T>
 sp<T>::sp(T* other) {
             cout << "enter sp(T* other) " << endl;
 }

 template<typename T>
 sp<T>::sp(const sp<T>& other) {
         cout << "enter sp(const sp<T>& other) " << endl;
 }

 template<typename T> template<typename U>
 sp<T>::sp(U* other) {
         cout << "enter sp(U *other) " << endl;
 }

 template<typename T> template<typename U>
 sp<T>::sp(const sp<U>& other) {
     cout << "sp(const sp<U& other>)" << endl;
 }

 template<typename T>
 sp<T>::~sp() {
 }

 template<typename T>
 sp<T>& sp<T>::operator =(T* other) {
     cout << "enter operator =(T* other) " << endl;
     return *this;
 }

 template<typename T>
 sp<T>& sp<T>::operator =(const sp<T>& other) {
     cout << "enter operator = (const sp<T>& other)" << endl;
     return *this;
 }

 template<typename T> template<typename U>
 sp<T>& sp<T>::operator =(const sp<U>& other) {
     cout << "operator = (const sp<U>& other)" << endl;
     return *this;
 }

 template<typename T> template<typename U>
 sp<T>& sp<T>::operator =(U* other) {
     cout << "operator = (U* other)" << endl;
     return *this;
 }

 class Peng{
 };

 class Dong {
 };

 int main(int argc, const char *argv[])
 {
     Peng *p = new Peng();
     Dong *d = new Dong();

     cout << "---- sp<Peng> q = p ----" << endl;
     sp<Peng> q = p;

     cout << "\n---- sp<Peng> r(p) ----" << endl;
     sp<Peng> r(p);

     cout << "\n---- sp<Peng> b(r) ----" << endl;
     sp<Peng> b(r);

     cout << "\n---- sp<Peng> t; ----" << endl;
     sp<Peng> t;
     cout << "\n---- t = p ----" << endl;
     t = p;

     cout << "\n---- sp<Peng> a; ----" << endl;
     sp<Peng> a;
     cout << "\n---- a = t ----" << endl;
     a = t;

     Dong *c = new Dong();
     cout << "\n---- sp<Dong> e = c ----" << endl;
     sp<Dong> e = c;
     cout << "\n---- a = e ----" << endl;
     a = e;
     cout << "\n---- a = c ----" << endl;
     a = c;

     cout << "\n---- sp<Dong> e1(e) ----" << endl;
     sp<Peng> e1(e);

     cout << endl << endl;
     return ;
 }

下面是在PC机上的运行结果：

pengdl@pengdl-HP:~/work/study/c++$ ./a.out
---- sp<Peng> q = p ----
enter sp(T* other) 

---- sp<Peng> r(p) ----
enter sp(T* other) 

---- sp<Peng> b(r) ----
enter sp(const sp<T>& other) 

---- sp<Peng> t; ----

---- t = p ----
enter operator =(T* other) 

---- sp<Peng> a; ----

---- a = t ----
enter operator = (const sp<T>& other)

---- sp<Dong> e = c ----
enter sp(T* other) 

---- a = e ----
operator = (const sp<U>& other)

---- a = c ----
operator = (U* other)

---- sp<Dong> e1(e) ----
sp(const sp<U& other>)

完。