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Commit d4af5ed

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更新视频代码以及CMake设置,引入三方库设置。
教案还未完成,先编写测试示例,后台播放音乐。
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-4
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‎.gitignore

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.vs/
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x64/
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out/
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bin/
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*.ilk
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*.pdb
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#include <iostream>
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#include <thread>
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#include <mutex>
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struct X {
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X(int v) { // 主要防止有人认为构造函数、析构函数啊,是线程安全的
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std::cout << v << " 🤣\n";
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}
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};
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void f() {
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X* p = new X{ 1 }; // 存在数据竞争
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delete p;
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}
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int main()
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{
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for (int i = 0; i < 10; ++i) {
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std::thread t{ f };
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std::thread t2{ f };
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t.join();
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t2.join();
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}
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// C++ 保证的是内存的申请和释放 这种全局状态 是线程安全的
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}
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#include <iostream>
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#include <thread>
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int global_counter = 0;
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__declspec(thread) int thread_local_counter = 0;
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void print_counters() {
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std::cout << "global:" << global_counter++ << '\n';
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std::cout << "thread_local:" << thread_local_counter++ << '\n';
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}
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int main() {
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std::thread{ print_counters }.join();
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std::thread{ print_counters }.join();
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}
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#include <iostream>
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#include <thread>
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thread_local int n = (std::puts("thread_local init"), 0);
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void f(){
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(void)n; // 防止 gcc 与 clang 优化
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std::puts("f");
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}
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void f2(){
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thread_local static int n = (std::puts("f2 init"), 0);
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}
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int main(){
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(void)n; // 防止 gcc 与 clang 优化
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std::cout << "main\n";
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std::thread{ f }.join();
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f2();
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f2();
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f2();
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}
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// gcc 与 clang 存在优化,会出现与 msvc 不同的结果,它们直接将线程变量优化掉了
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// 这应该视作 bug。
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// 视频中想到 std::async 是下一章的内容跳过了(想到的是 msvc 的一个问题),忘记了 gcc 与 clang 此处也存在问题。
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// https://godbolt.org/z/qa6YfMqP7
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#include <iostream>
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#include <thread>
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#include <condition_variable>
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#include <mutex>
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#include <chrono>
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using namespace std::chrono_literals;
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std::mutex mtx; // 互斥量
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std::condition_variable_any cv; // 条件变量
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bool arrived = false;
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void wait_for_arrival() {
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std::unique_lock<std::mutex> lck(mtx); // 上锁
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cv.wait(lck, [] { return arrived; }); // 等待 arrived 变为 true 会解锁的 再次上锁
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std::cout << "到达目的地,可以下车了!" << std::endl;
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}
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void simulate_arrival() {
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std::this_thread::sleep_for(std::chrono::seconds(5)); // 模拟地铁到站,假设5秒后到达目的地
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{
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std::lock_guard<std::mutex> lck(mtx);
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arrived = true; // 设置条件变量为 true,表示到达目的地
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}
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cv.notify_one(); // 通知等待的线程
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}
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int main(){
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std::thread t{ wait_for_arrival };
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std::thread t2{ simulate_arrival };
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t.join();
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t2.join();
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}
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#include <iostream>
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#include <thread>
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#include <condition_variable>
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#include <mutex>
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#include <chrono>
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#include <queue>
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using namespace std::chrono_literals;
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template<typename T>
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class threadsafe_queue {
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mutable std::mutex m; // M&M 原则 互斥量,用于保护队列操作的独占访问
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std::condition_variable data_cond; // 条件变量,用于在队列为空时等待
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std::queue<T> data_queue; // 实际存储数据的队列
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public:
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threadsafe_queue() {}
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void push(T new_value) {
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{
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std::lock_guard<std::mutex> lk{ m };
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std::cout << "push:" << new_value << std::endl;
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data_queue.push(new_value);
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}
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data_cond.notify_one();
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}
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// 从队列中弹出元素(阻塞直到队列不为空)
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void pop(T& value) {
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std::unique_lock<std::mutex> lk{ m };
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data_cond.wait(lk, [this] {return !data_queue.empty(); }); // 解除阻塞 重新获取锁 lock
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value = data_queue.front();
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std::cout << "pop:" << value << std::endl;
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data_queue.pop();
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}
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// 从队列中弹出元素(阻塞直到队列不为空),并返回一个指向弹出元素的 shared_ptr
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std::shared_ptr<T> pop() {
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std::unique_lock<std::mutex> lk{ m };
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data_cond.wait(lk, [this] {return !data_queue.empty(); });
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std::shared_ptr<T>res{ std::make_shared<T>(data_queue.front()) };
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data_queue.pop();
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return res;
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}
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bool empty()const {
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std::lock_guard<std::mutex> lk(m);
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return data_queue.empty();
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}
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};
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void producer(threadsafe_queue<int>& q) {
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for (int i = 0; i < 5; ++i) {
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q.push(i);
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}
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}
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void consumer(threadsafe_queue<int>& q) {
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for (int i = 0; i < 5; ++i) {
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int value{};
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q.pop(value);
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}
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}
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int main() {
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threadsafe_queue<int> q;
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std::thread producer_thread(producer, std::ref(q));
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std::thread consumer_thread(consumer, std::ref(q));
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producer_thread.join();
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consumer_thread.join();
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}

‎code/ModernCpp-ConcurrentProgramming-Tutorial/CMakeLists.txt

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SET(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/bin)
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if(MSVC)
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add_compile_options("/utf-8" "/permissive-" "/Zc:nrvo""/Od")
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add_compile_options("/utf-8" "/permissive-" "/Zc:nrvo")
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elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
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add_compile_options("-finput-charset=UTF-8" "-fexec-charset=UTF-8")
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endif()
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add_executable(ModernCpp-ConcurrentProgramming-Tutorial "20recursive_mutex.cpp")
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add_executable(${PROJECT_NAME} "25线程安全的队列.cpp")
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# 设置 SFML 的 CMake 路径
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set(SFML_DIR "D:/lib/SFML-2.6.1-windows-vc17-64-bit/SFML-2.6.1/lib/cmake/SFML")
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# 查找 SFML 库并设置链接选项
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find_package(SFML 2.6.1 COMPONENTS system window graphics audio network REQUIRED)
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# 链接 SFML 库到项目
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target_link_libraries(${PROJECT_NAME} sfml-system sfml-window sfml-graphics sfml-audio sfml-network)
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#include "test/AduioPlayer.h"
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AudioPlayer audioPlayer;
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int main(){
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audioPlayer.addAudioPath(AudioPlayer::soundResources[4]);
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audioPlayer.addAudioPath(AudioPlayer::soundResources[5]);
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audioPlayer.addAudioPath(AudioPlayer::soundResources[6]);
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audioPlayer.addAudioPath(AudioPlayer::soundResources[7]);
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std::thread t{ []{
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std::this_thread::sleep_for(1s);
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audioPlayer.addAudioPath(AudioPlayer::soundResources[1]);
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} };
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std::thread t2{ []{
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audioPlayer.addAudioPath(AudioPlayer::soundResources[0]);
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} };
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std::cout << "乐\n";
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t.join();
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t2.join();
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std::cout << "end\n";
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}
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#ifndef AUDIOPLAYER_H
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#define AUDIOPLAYER_H
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#include <iostream>
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#include <thread>
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#include <mutex>
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#include <condition_variable>
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#include <queue>
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#include <string>
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#include <atomic>
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#include <array>
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#include <SFML/Audio.hpp>
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using namespace std::chrono_literals;
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class AudioPlayer {
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public:
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AudioPlayer() : stop{ false }, player_thread{ &AudioPlayer::playMusic, this }
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{}
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~AudioPlayer() {
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// 等待队列中所有音乐播放完毕
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while (!audio_queue.empty()) {
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std::this_thread::sleep_for(50ms);
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}
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stop = true;
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cond.notify_all();
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if (player_thread.joinable()) {
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player_thread.join();
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}
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}
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void addAudioPath(const std::string& path) {
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std::lock_guard<std::mutex> lock{ mtx };
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audio_queue.push(path);
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cond.notify_one(); // 通知线程新的音频
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}
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private:
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void playMusic() {
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while (!stop) {
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std::string path;
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{
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std::unique_lock<std::mutex> lock{ mtx };
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cond.wait(lock, [this] { return !audio_queue.empty() || stop; });
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if (audio_queue.empty()) return; // 防止在对象为空时析构出错
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path = audio_queue.front();
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audio_queue.pop();
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}
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if (!music.openFromFile(path)) {
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std::cerr << "无法加载音频文件: " << path << std::endl;
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continue; // 继续播放下一个音频
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}
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music.play();
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// 等待音频播放完毕
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while (music.getStatus() == sf::SoundSource::Playing) {
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sf::sleep(sf::seconds(0.1f)); // sleep 避免忙等占用CPU
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}
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}
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}
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std::atomic<bool> stop;
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std::thread player_thread;
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std::mutex mtx;
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std::condition_variable cond;
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std::queue<std::string> audio_queue;
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sf::Music music;
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public:
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static constexpr std::array soundResources{
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"./sound/01初始化失败.ogg",
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"./sound/02初始化成功.ogg",
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"./sound/03试剂不足,请添加.ogg",
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"./sound/04试剂已失效,请更新.ogg",
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"./sound/05清洗液不足,请添加.ogg",
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"./sound/06废液桶即将装满,请及时清空.ogg",
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"./sound/07废料箱即将装满,请及时清空.ogg",
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"./sound/08激发液A液不足,请添加.ogg",
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"./sound/09激发液B液不足,请添加.ogg",
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"./sound/10反应杯不足,请添加.ogg",
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"./sound/11检测全部完成.ogg"
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};
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enum SoundIndex {
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InitializationFailed,
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InitializationSuccessful,
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ReagentInsufficient,
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ReagentExpired,
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CleaningAgentInsufficient,
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WasteBinAlmostFull,
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WasteContainerAlmostFull,
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LiquidAInsufficient,
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LiquidBInsufficient,
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ReactionCupInsufficient,
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DetectionCompleted,
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SoundCount // 总音频数量,用于计数
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};
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};
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#endif // AUDIOPLAYER_H

‎md/04同步操作.md

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# 同步操作
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"同步操作"是指在计算机科学和信息技术中的一种操作方式,其中不同的任务或操作按顺序执行,一个操作完成后才能开始下一个操作。在多线程编程中,各个任务通常需要通过同步操作进行相互**协调和等待**,以确保数据的**一致性**和**正确性**。
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"同步操作"是指在计算机科学和信息技术中的一种操作方式,其中不同的任务或操作按顺序执行,一个操作完成后才能开始下一个操作。在多线程编程中,各个任务通常需要通过**同步设施**进行相互**协调和等待**,以确保数据的**一致性**和**正确性**。
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本章的主要内容有:
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## 线程安全的队列
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在本节中,我们介绍了一个更为复杂的示例,以巩固我们对条件变量的学习。为了实现一个线程安全的队列,我们需要考虑以下两个关键点:
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在本节中,我们介将绍一个更为复杂的示例,以巩固我们对条件变量的学习。为了实现一个线程安全的队列,我们需要考虑以下两个关键点:
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1. 当执行 `push` 操作时,需要确保没有其他线程正在执行 `push` 或 `pop` 操作;同样,在执行 `pop` 操作时,也需要确保没有其他线程正在执行 `push` 或 `pop` 操作。
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到此,也就可以了。
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## 使用条件变量实现后台音乐播放
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## 使用 `future`
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举个例子:我们在车站等车,你可能会做一些别的事情打发时间,比如学习[现代 C++ 模板教程](https://github.com/Mq-b/Modern-Cpp-templates-tutorial)、观看 [mq白](https://space.bilibili.com/1292761396) 的视频教程、玩手机等。不过,你始终在等待一件事情:***车到站***。

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