对象保护计数类

作为CSDN第一篇，对Guard类代码进行研读和debug，总结以下几点：

1.Guard类内包含core struct，该struct提供实际存入其中的Guard对象的方法，并提供引用计数管理

2.Guard类中重载多个构造函数，只有不带参的默认构造函数申明为explicit，即不允许编译器隐式调用该函数

3.调用 BJGuard& operator=(const BJGuard& other)后，调用该函数的对象通过this指针被销毁；其core指针被重新赋值；引用计数增加

调用前

调用后

4.bool操作符重载，使用方法直接在if语句内判断对象名即可。debug后发现该程序应用于多线程场合，虽然引用计数是原子操作，但是operator=语句可能不是。因此需要valid判断。

最后上代码

#include <cstdio>#include <stddef.h>#include <stdio.h>class BJGuard{public:explicitBJGuard(char* str, bool isMaster = true) : m_BJCore(new BJCore(isMaster ? this : NULL)), m_str(str){printf("BJGuard:BJGuard(bool isMaster = true) called========%s\n", m_str);m_BJCore->AddRef();}BJGuard(char* str, const BJGuard& other) : m_BJCore(other.m_BJCore), m_str(str) {printf("BJGuard:BJGuard(const BJGuard& other) called========%s\n", m_str);m_BJCore->AddRef();}BJGuard(char* str, BJGuard& other) : m_BJCore(other.m_BJCore), m_str(str) {printf("BJGuard:BJGuard(BJGuard& other) called========%s\n", m_str);m_BJCore->AddRef();}~BJGuard() {m_BJCore->Release(this);}BJGuard& operator=(const BJGuard& other) {printf("BJGuard:operator=(const BJGuard& other) called\n");printf("BJGuard:operator=(const BJGuard& other) called, %s will be release\n", m_str);m_BJCore->Release(this);m_BJCore = other.m_BJCore;m_BJCore->AddRef();return *this;}void reset(bool isMaster = true) {m_BJCore->Release(this);m_BJCore = new BJCore(isMaster ? this : NULL);m_BJCore->AddRef();}inline operator bool() const { printf("BJGuard:operator bool() called\n"); return m_BJCore->valid(); }private:struct BJCore{explicit BJCore(BJGuard* _master) : m_master(_master), m_refCount(0) {printf("BJCore(BJGuard* _master) called\n");printf("BJCore(BJGuard* _master) called\n");}inline void AddRef() {__sync_add_and_fetch(&m_refCount, 1);}inline void Release(BJGuard* guard) {if (m_master == guard) {m_master = NULL;printf("BJCore:Release(BJGuard* guard) called, m_master is NULL\n");}if (0 == __sync_sub_and_fetch(&m_refCount, 1)) {delete this;}}inline bool valid()    const { if (m_master) {return true;}else {return false;}}inline BJGuard* master() const { return m_master; }private:BJCore(BJCore& other);BJCore operator =(BJCore& other);private:BJGuard* m_master;int    m_refCount;};private:BJCore* m_BJCore;char* m_str;};

希望能保持下去。