更新教案

1. 修改第二、第三章的部分微小措辞以及代码格式。
2. 更新项目文件中的代码示例，用作视频学习。

Author: Mq-b

code/ModernCpp-ConcurrentProgramming-Tutorial/09-实现joining_thread.cpp

@@ -0,0 +1,69 @@
+#include <iostream>
+#include <thread>
+#include <type_traits>
+#include <vector>
+#include <mutex>
+
+class joining_thread {
+    std::thread t;
+public:
+    joining_thread()noexcept = default;
+
+    template<typename Callable, typename... Args>
+    explicit joining_thread(Callable&& func, Args&&...args) :
+        t{ std::forward<Callable>(func), std::forward<Args>(args)... } {}
+
+    explicit joining_thread(std::thread t_)noexcept : t{ std::move(t_) } {}
+
+    joining_thread(joining_thread&& other)noexcept : t{ std::move(other.t) } {}
+
+    joining_thread& operator=(std::thread&& other)noexcept {
+        if (joinable()) { // 如果当前有活跃线程（判断当前对象是否持有资源），那就先执行完（先释放）
+            join(); // 就相当于释放资源一样的意思
+        }
+        t = std::move(other);
+        return *this;
+    }
+    ~joining_thread() {
+        if (joinable()) {
+            join();
+        }
+    }
+    void swap(joining_thread& other)noexcept {
+        t.swap(other.t);
+    }
+    std::thread::id get_id()const noexcept {
+        return t.get_id();
+    }
+    bool joinable()const noexcept {
+        return t.joinable();
+    }
+    void join() {
+        t.join();
+    }
+    void detach() {
+        t.detach();
+    }
+    std::thread& data()noexcept {
+        return t;
+    }
+    const std::thread& data()const noexcept {
+        return t;
+    }
+};
+
+int main(){
+    auto func = []{
+        std::cout << std::this_thread::get_id() << '\n';
+    };
+
+    std::vector<std::thread> vec;
+
+    for (int i = 0; i < 10; ++i){
+        vec.emplace_back(func);
+    }
+
+    for(auto& thread : vec){
+        thread.join();
+    }
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/10-C++20jthread.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <thread>
+
+using namespace std::literals::chrono_literals;
+
+void f(std::stop_token stop_token, int value) {
+    while (!stop_token.stop_requested()) { // 检查是否已经收到停止请求
+        std::cout << value++ << ' ' << std::flush;
+        std::this_thread::sleep_for(200ms);
+    }
+    std::cout << std::endl;
+}
+
+int main() {
+    std::jthread thread{ f, 1 }; // 打印 1..15 大约 3 秒
+    std::this_thread::sleep_for(3s);
+    thread.request_stop(); // 发送信息，线程终止
+    std::cout << "乐\n";
+    // jthread 的析构函数调用 request_stop() 和 join()。
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/11-数据竞争.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+#include <thread>
+#include <vector>
+
+std::vector<int> v;
+
+int n = 1;
+
+int main() {
+    int cnt = 0;
+    auto f = [&] { cnt++; };
+    std::thread t1{ f }, t2{ f }, t3{ f }; // ub 未定义行为
+    t1.join();
+    t2.join();
+    t3.join();
+    std::cout << cnt << '\n';
+}
+// 数据竞争它是未定义行为，但是 C++ 的编译器，它会假设你的程序(假设程序是对的，代码是对的)没有任何的未定义行为再去进行优化
+// 输出 n，优化，直接缓存这个值

code/ModernCpp-ConcurrentProgramming-Tutorial/12-使用互斥量.cpp

@@ -0,0 +1,44 @@
+#include <iostream>
+#include <thread>
+#include <vector>
+#include <mutex>
+#include <algorithm>
+#include <list>
+#include <numeric>
+
+std::mutex m;
+
+// 写
+void add_to_list(int n, std::list<int>& list) {
+    std::vector<int> numbers(n + 1);
+    std::iota(numbers.begin(), numbers.end(), 0);
+    int sum = std::accumulate(numbers.begin(), numbers.end(), 0);
+
+    {
+        std::scoped_lock lc{ m };
+        list.push_back(sum);
+    }
+}
+
+// 读
+void print_list(const std::list<int>& list) {
+    std::scoped_lock lc{ m };
+    for (const auto& i : list) {
+        std::cout << i << ' ';
+    }
+    std::cout << '\n';
+}
+
+int main(){
+    std::list<int> list;
+    std::thread t1{ add_to_list,10,std::ref(list) };
+    std::thread t2{ add_to_list,10,std::ref(list) };
+    std::thread t3{ print_list,std::cref(list) };
+    std::thread t4{ print_list,std::cref(list) };
+    t1.join();
+    t2.join();
+    t3.join();
+    t4.join();
+    std::cout << "---------------------\n";
+    print_list(list);
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/13-try_lock.cpp

@@ -0,0 +1,33 @@
+#include <iostream>
+#include <thread>
+#include <vector>
+#include <mutex>
+#include <string>
+using namespace std::string_literals;
+
+std::mutex mtx;
+
+void thread_function(int id) {
+    // 尝试加锁
+    if (mtx.try_lock()) {
+        std::string s = "线程："s + std::to_string(id) + " 获得锁"s + "\n";
+        std::string s2 = "线程："s + std::to_string(id) + " 释放锁"s + "\n";
+        std::cout << s;
+        // 临界区代码
+        std::this_thread::sleep_for(std::chrono::milliseconds(100)); // 模拟临界区操作
+        mtx.unlock(); // 解锁
+        std::cout << s2;
+    }
+    else {
+        std::string s = "线程："s + std::to_string(id) + " 获取锁失败 处理步骤"s + "\n";
+        std::cout << s;
+    }
+}
+
+int main(){
+    std::thread t1(thread_function, 1);
+    std::thread t2(thread_function, 2);
+
+    t1.join();
+    t2.join();
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/14-保护共享数据.cpp

@@ -0,0 +1,40 @@
+#include <iostream>
+#include <thread>
+#include <mutex>
+
+class Data {
+    int a{};
+    std::string b{};
+public:
+    void do_something() {
+        // 修改数据成员等...
+    }
+};
+
+class Data_wrapper {
+    Data data;
+    std::mutex m;
+public:
+    template<class Func>
+    void process_data(Func func) {
+        std::lock_guard<std::mutex> lc{ m };
+        func(data);  // 受保护数据传递给函数
+    }
+};
+
+Data* p = nullptr;
+
+void malicious_function(Data& protected_data) {
+    p = &protected_data; // 受保护的数据被传递到外部
+}
+
+Data_wrapper d;
+
+void foo() {
+    d.process_data(malicious_function);  // 传递了一个恶意的函数
+    p->do_something();                   // 在无保护的情况下访问保护数据
+}
+
+int main(){
+    
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/15-死锁：问题与解决.cpp

@@ -0,0 +1,28 @@
+#include <iostream>
+#include <thread>
+#include <mutex>
+#include <chrono>
+using namespace std::chrono_literals;
+
+struct X {
+    X(const std::string& str) :object{ str } {}
+
+    friend void swap(X& lhs, X& rhs);
+private:
+    std::string object;
+    std::mutex m;
+};
+
+void swap(X& lhs, X& rhs) {
+    if (&lhs == &rhs) return;
+    std::scoped_lock guard{ lhs.m,rhs.m };
+    swap(lhs.object, rhs.object);
+}
+
+int main(){
+    X a{ "🤣" }, b{ "😅" };
+    std::thread t{ [&] {swap(a, b); } };  // 1
+    std::thread t2{ [&] {swap(b, a); } }; // 2
+    t.join();
+    t2.join();
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/16-unique_lock.cpp

@@ -0,0 +1,32 @@
+#include <iostream>
+#include <thread>
+#include <mutex>
+#include <chrono>
+using namespace std::chrono_literals;
+
+struct X {
+    X(const std::string& str) :object{ str } {}
+
+    friend void swap(X& lhs, X& rhs);
+private:
+    std::string object;
+    std::mutex m;
+};
+
+void swap(X& lhs, X& rhs) {
+    if (&lhs == &rhs) return;
+    std::lock(rhs.m, lhs.m);
+
+    std::unique_lock<std::mutex> lock1{ lhs.m, std::adopt_lock };
+    std::unique_lock<std::mutex> lock2{ rhs.m, std::adopt_lock };
+    // std::lock(lock1, lock2);
+    swap(lhs.object, rhs.object);
+}
+
+int main() {
+    X a{ "🤣" }, b{ "😅" };
+    std::thread t{ [&] {swap(a, b); } };  // 1
+    std::thread t2{ [&] {swap(b, a); } }; // 2
+    t.join();
+    t2.join();
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/17-在不同作用域传递互斥量.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+#include <thread>
+#include <mutex>
+#include <chrono>
+#include <memory>
+
+std::unique_lock<std::mutex> get_lock() {
+    extern std::mutex some_mutex;
+    std::unique_lock<std::mutex> lk{ some_mutex };
+    return lk; // 选择到 unique_lock 的移动构造，转移所有权
+}
+void process_data() {
+    std::unique_lock<std::mutex> lk{ get_lock() }; // 转移到了主函数的 lk 中
+    // 执行一些任务...
+}// 最后才会 unlock 解锁
+
+int main(){
+    process_data();
+}

code/ModernCpp-ConcurrentProgramming-Tutorial/18-保护共享数据的初始化过程.cpp

@@ -0,0 +1,51 @@
+#include <iostream>
+#include <thread>
+#include <mutex>
+#include <chrono>
+#include <memory>
+
+struct some{
+    void do_something(){}
+};
+
+std::shared_ptr<some> ptr;
+std::once_flag resource_flag;
+
+void init_resource() {
+    ptr.reset(new some);
+}
+
+void foo() {
+    std::call_once(resource_flag, []{ptr.reset(new some); }); // 线程安全的一次初始化
+    ptr->do_something();
+}
+
+void test(){
+    std::call_once(resource_flag, [] {std::cout << "f init\n"; });
+}
+
+std::once_flag flag;
+int n = 0;
+
+void f() {
+    std::call_once(flag, [] {
+        ++n;
+        std::cout << "第 " << n << " 次调用\n";
+        throw std::runtime_error("异常");
+    });
+}
+
+class my_class{};
+
+inline my_class& get_my_class_instance() {
+    static my_class instance;  // 线程安全的初始化过程 初始化严格发生一次
+    return instance;
+}
+
+int main() {
+    get_my_class_instance();
+    get_my_class_instance();
+    get_my_class_instance();
+    get_my_class_instance();
+    get_my_class_instance();
+}