c++引用計數實現

#include <iostream>#include <stdio.h>using namespace std;class String {public:    String(const char *pdata);    String(const String &rhs);    String &operator = (const String &rhs);    ~String();private:    class StringValue {    public:        int refCount;        char *data;        StringValue(const char *pdata);        ~StringValue();    };    StringValue *value;//所有的引用對象均共用唯一一個value，value裡面實際儲存data和引用次數};String::StringValue::StringValue(const char *pdata):refCount(1) {    data = new char[strlen(pdata) + 1];    strcpy(data,pdata);}String::StringValue::~StringValue() {    delete [] data;}String::String(const char *pdata):value(new StringValue(pdata)){}String::String(const String &rhs) {//要對引用加1    value = rhs.value;    value->refCount++;//所有指向同一段data的對象的引用加1}String &String::operator =(const String &rhs) {    if (value == rhs.value)//注意，不是this == &rhs        return *this;    if(--value->refCount == 0)        delete value;    value = rhs.value;    ++value->refCount;    return *this;}String::~String() {    if (--value->refCount == 0)        delete value;}void test() {    String ss("ssss");    String s1 = ss;    String s2("dddd");    s2 = ss;}int main() {    test();}