shared_ptr 主要依赖一个引用计数指针和一个 mutex 锁来实现管理对象生命周期。
code
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#include <iostream>
#include <mutex>
using namespace std;
template<typename T>
class myshared_ptr {
public:
myshared_ptr(T* ptr)
: realPtr(ptr), refCount(new int(1)), lock(new mutex) {
cout << "construct, refCount: 1" << endl;
}
myshared_ptr(const myshared_ptr<T>& other)
: realPtr(other.realPtr), refCount(other.refCount), lock(other.lock) {
lock->lock();
++(*refCount);
cout << "refCount: " << *refCount << endl;
lock->unlock();
}
T& operator*() {
return *realPtr;
}
T* operator->() {
return realPtr;
}
~myshared_ptr() {
lock->lock();
--(*refCount);
if(*refCount == 0) {
delete realPtr;
cout << "delete realPtr" << endl;
lock->unlock();
delete lock;
return;
}
lock->unlock();
}
private:
const myshared_ptr<T>& operator=(const myshared_ptr<T> other) { }
private:
T* realPtr;
int* refCount;
mutex* lock;
};
class A {
public:
int val;
char c;
};
void fun() {
myshared_ptr<A> aPtr(new A);
myshared_ptr<A> bPtr = aPtr;
aPtr->val = 101;
aPtr->c = 'Y';
cout << (*aPtr).val << " " << (*bPtr).c << endl;
}
int main() {
fun();
}
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