C++....................4

1.

using namespace std;                 class mystring {
private:char* p;int len;// 辅助函数：复制字符串void copy(const char* source) {len = strlen(source);p = new char[len + 1];strcpy(p, source);}// 辅助函数：释放内存void release() {if (p) {delete[] p;}}public:// 构造函数mystring(const char* s = "") {copy(s);}// 拷贝构造函数mystring(const mystring& other) {copy(other.p);}// 析构函数~mystring() {release();}// 赋值运算符重载mystring& operator=(const mystring& other) {if (this != &other) {release();copy(other.p);}return *this;}// 加法运算符重载mystring operator+(const mystring& other) const {char* temp = new char[len + other.len + 1];strcpy(temp, p);strcat(temp, other.p);mystring result(temp);delete[] temp;return result;}// 复合赋值运算符重载mystring& operator+=(const mystring& other) {char* temp = new char[len + other.len + 1];strcpy(temp, p);strcat(temp, other.p);release();copy(temp);delete[] temp;return *this;}// 下标运算符重载char& operator[](int index) {
#include <cstring>return p[index];}// 输出字符串void show() const {cout << p << endl;}
};int main() {mystring str = "hello";mystring ptr = "world";str.show();ptr.show();str = str + ptr;str.show();str += ptr;str.show();str[0] = 'H';str.show();return 0;
}

2.

// 定义消息结构体
struct buf{long mtype;       // 消息类型，用于区分不同的频道char mtext[1024]; // 消息内容
};// 定义 Channel 类，用于表示消息队列中的特定频道
class Channel {
private:int msgid;long channel;public:Channel(int id, long ch) : msgid(id), channel(ch) {}// 发送消息到指定频道void send(const std::string& data) {buf message;message.mtype = channel;strncpy(message.mtext, data.c_str(), sizeof(message.mtext) - 1);message.mtext[sizeof(message.mtext) - 1] = '\0';if (msgsnd(msgid, &message, strlen(message.mtext) + 1, 0) == -1) {perror("msgsnd");}}// 从指定频道读取消息std::string read(int size) {buf message;if (msgrcv(msgid, &message, size, channel, 0) == -1) {perror("msgrcv");return "";}return std::string(message.mtext);}
};// 定义 Msg 类，用于封装消息队列的操作
class Msg {
private:key_t key;int msgid;public:// 构造函数，根据文件名生成消息队列的键值并创建消息队列Msg(const std::string& filename) {key = ftok(filename.c_str(), 'a');if (key == -1) {perror("ftok");}msgid = msgget(key, IPC_CREAT | 0666);if (msgid == -1) {perror("msgget");}}// 重载 [] 运算符，返回指定频道的 Channel 对象Channel operator[](long channel) {return Channel(msgid, channel);}
};int main() {// 创建 Msg 对象，指定文件名Msg m("o.txt");// 向 1 号频道发送消息m[1].send("Hello, World!");// 从 1 号频道读取消息std::string str = m[1].read(1024);std::cout << "1号频道: " << str << std::endl;return 0;
}

3.

class Sem {
private:key_t key;int id;// 辅助函数：执行信号量操作void do_semop(int sem_num, int sem_op) {struct sembuf sops = {static_cast<unsigned short>(sem_num), static_cast<short>(sem_op), 0};if (::semop(id, &sops, 1) == -1) {  // 使用 ::semop 调用系统函数throw std::runtime_error("semop failed");}}public:// 构造函数：创建信号灯集，信号灯集中存在 x 个信号量，并且将所有信号量初始化为 ySem(int num_semaphores, int initial_value) {key = ftok(".", 'a');if (key == -1) {throw std::runtime_error("ftok failed");}id = semget(key, num_semaphores, IPC_CREAT | 0666);if (id == -1) {throw std::runtime_error("semget failed");}for (int i = 0; i < num_semaphores; ++i) {if (semctl(id, i, SETVAL, initial_value) == -1) {throw std::runtime_error("semctl failed");}}}// 手动初始化信号灯集中的第 index 个信号量，初始化成 valuevoid init(int index, int value) {if (semctl(id, index - 1, SETVAL, value) == -1) {throw std::runtime_error("semctl failed");}}// 重载 [] 运算符，返回一个可用于操作信号量的对象class SemProxy {private:Sem& sem;int index;public:SemProxy(Sem& s, int idx) : sem(s), index(idx - 1) {}// 重载 + 和 - 运算符，让信号灯集中的第 index 个信号量的值增加或减少SemProxy& operator+(int val) {sem.do_semop(index, val); return *this;}SemProxy& operator-(int val) {sem.do_semop(index, -val); return *this;}};SemProxy operator[](int index) {return SemProxy(*this, index);}// 析构函数：删除信号灯集~Sem() {if (semctl(id, 0, IPC_RMID) == -1) {std::cerr << "Warning: semctl IPC_RMID failed" << std::endl;}}
};int main() {try {// 创建信号灯集，包含 2 个信号量，初始值都为 5Sem s(2, 5);// 手动初始化信号灯集中的第 1 个信号量，初始化成 10s.init(1, 10);// 让信号灯集中的第 1 个信号量的值 +1s[1] + 1;// 让信号灯集中的第 1 个信号量的值 -1s[1] - 1;std::cout << "信号量操作成功" << std::endl;} catch (const std::exception& e) {std::cerr << "Error: " << e.what() << std::endl;}return 0;