ckground-color: #ccffcc">实例如下：
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#include<iostream>using namespace std; class String;ostream& operator<<(ostream &out, const String&s);//引用计数器类class String_rep { friend class String; friend ostream& operator<<(ostream &out, const String&s);public: String_rep(const char *str ) :use_count(0) { if (str == NULL) { data = new char[1]; data[0] = '\0'; } else { data = new char[strlen(str) + 1]; strcpy(data, str); } } String_rep(const String_rep &rep) :use_count(0) { data = new char[strlen(rep.data) + 1]; strcpy(data, rep.data); } String_rep& operator=(const String_rep &rep) { if (this != &rep) { delete[]data; data = new char[strlen(rep.data) + 1]; strcpy(data, rep.data); } return *this; } ~String_rep() { delete[]data; data = NULL; }public: void increase() { ++use_count; } void decrease() { if (use_count == 0) { delete this; //自杀行为 释放this所指的空间，在释放之前调动这个类的析构函数 } }private: char *data; int use_count;};////////////////////////////////////////////////////////////////////////////////////////class String{ friend ostream& operator<<(ostream &out, const String&s);public: String(const char* str = " ") { rep = new String_rep(str); rep->increase(); } String(const String &s) { rep->increase(); } String& operator=(const String &s) { if (this != &s) { rep->decrease(); //模拟delete rep = s.rep; //模拟new rep->increase(); //模拟strcpy /*rep = s.rep; //这会更改引用计数器指针 ，造成s内存泄漏 rep->increase();*/ } return *this; } ~String() { rep->decrease(); }public: void to_upper() { if (rep->use_count > 1) { String_rep* new_rep = new String_rep(rep->data); rep->decrease(); rep = new_rep; rep->increase(); } char* ch = rep->data; while (*ch != '\0') { *ch -= 32; ++ch; } }private: String_rep *rep; //引用计数器};ostream& operator<<(ostream &out, const String&s){ out << s.rep->data; return out;}void main(){ String s1("hello"); String s2(s1); String s3; s3 = s2; cout << "s1=" << s1 << endl; cout << "s2=" << s2 << endl; cout << "s3=" << s3 << endl; s2.to_upper(); cout << "-----------------------------------------------" << endl; cout << "s1=" << s1 << endl; cout << "s2=" << s2 << endl; cout << "s3=" << s3 << endl;} |
以上这篇String类的写时拷贝实例就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持服务器之家。
