城市分站seo,做网站建设要学多久,档案网站建设图片,郑州艾特软件 网站建设参考引用 C11 14 17 20 多线程从原理到线程池实战代码运行环境#xff1a;Visual Studio 2019 1. 为什么要用多线程
任务分解 耗时的操作#xff0c;任务分解#xff0c;实时响应 数据分解 充分利用多核CPU处理数据 数据流分解 读写分离#xff0c;解耦合设计
2. 第一个… 参考引用 C11 14 17 20 多线程从原理到线程池实战代码运行环境Visual Studio 2019 1. 为什么要用多线程
任务分解 耗时的操作任务分解实时响应 数据分解 充分利用多核CPU处理数据 数据流分解 读写分离解耦合设计
2. 第一个子线程代码示例
first_thread.cpp#include iostream
#include threadusing namespace std;// 创建的子线程的入口函数
void ThreadMain() {// 获取子线程开始时刻的 ID 号cout begin sub thread ID this_thread::get_id() endl;for (int i 0; i 5; i) {cout in thread i endl;// 子线程睡眠释放CPU 资源 1000msthis_thread::sleep_for(chrono::seconds(1)); }cout end sub thread ID this_thread::get_id() endl;
}// 主线程的入口函数 main()
int main(int argc, char* argv[]) {cout main thread ID this_thread::get_id() endl;// 线程创建启动thread th(ThreadMain);cout begin wait sub thread endl;// 阻塞等待子线程退出th.join();cout end wait sub thread endl;return 0;
}控制台输出main thread ID 21580
begin wait sub thread
begin sub thread ID 22924
in thread 0
in thread 1
in thread 2
in thread 3
in thread 4
end sub thread ID 22924
end wait sub thread3. std::thread 对象生命周期、线程等待和分离 thread_detach.cpp #include iostream
#include threadusing namespace std;bool is_exit false;void ThreadMain() {cout begin sub thread ID this_thread::get_id() endl;for (int i 0; i 5; i) {if (!is_exit)break;cout in thread i endl;this_thread::sleep_for(chrono::seconds(1)); // 子线程睡眠释放CPU 资源 1000ms}cout end sub thread ID this_thread::get_id() endl;
}int main(int argc, char* argv[]) {{//thread th(ThreadMain); // 出错thread 对象被销毁 子线程还在运行}{thread th(ThreadMain);th.detach(); // 子线程与主线程分离 守护线程在后台运行// 但存在一个问题主线程退出后 子线程不一定退出}{thread th(ThreadMain);this_thread::sleep_for(chrono::seconds(1));//1000msis_exit true; // 通知子线程退出cout 主线程阻塞等待子线程退出 endl;th.join(); // 主线程阻塞等待子线程退出cout 子线程已经退出 endl;}getchar();return 0;
}控制台输出 begin sub thread ID 25520
end sub thread ID 25520
begin sub thread ID 23324
end sub thread ID 23324
主线程阻塞等待子线程退出
子线程已经退出4. 全局函数作为线程入口 thread_para.cpp #include iostream
#include thread
#include stringusing namespace std;class Para {
public:Para() {cout Create Para endl;}Para(const Para p) { // 拷贝构造函数cout Copy Para endl; }~Para() {cout Drop Para endl;}string name;
};void ThreadMain(int p1, float p2, string str, Para p4) {this_thread::sleep_for(100ms);cout ThreadMain p1 p2 str p4.name endl;
}int main(int argc, char* argv[]) {thread th;{float f1 12.1f;Para p;p.name test Para class;// 所有的参数做复制th thread(ThreadMain, 101, f1, test string para, p);}th.join();return 0;
}控制台输出 Create Para
Copy Para
Drop Para
Copy Para
ThreadMain 101 12.1 test string para
Drop Para
Drop Para5. 线程函数传递指针和引用 参数传递存在的问题 传递空间已经销毁多线程共享访问一块空间传递的指针变量的生命周期小于线程 thread_para.cpp
#include thread
#include iostream
#include stringusing namespace std;class Para {
public:Para() { cout Create Para endl; }Para(const Para p) { cout Copy Para endl; }~Para() { cout Drop Para endl; }string name;
};void ThreadMain(int p1, float p2, string str, Para p4) {this_thread::sleep_for(100ms);cout ThreadMain p1 p2 str p4.name endl;
}void ThreadMainPtr(Para* p) {this_thread::sleep_for(100ms);cout ThreadMainPtr name p-name endl;
}void ThreadMainRef(Para p) {this_thread::sleep_for(100ms);cout ThreadMainPtr name p.name endl;
}
int main(int argc, char* argv[]) {{// 传递引用Para p;p.name test ref;thread th(ThreadMainRef, ref(p));th.join();}getchar();{// 传递线程指针Para p;p.name test ThreadMainPtr name;thread th(ThreadMainPtr, p); th.detach(); // 错误线程访问的 p 空间会提前释放}getchar(); // Para 释放{ // 传递线程指针Para p;p.name test ThreadMainPtr name;thread th(ThreadMainPtr, p);th.join();getchar();}thread th;{float f1 12.1f;Para p;p.name test Para class;// 所有的参数做复制th thread(ThreadMain, 101, f1, test string para, p);}th.join();return 0;
}控制台输出Create Para
ThreadMainPtr name test ref
Drop Para6. 成员函数作为线程入口–封装线程基类接口 XThread.h 封装线程基类接口 #pragma once#include iostream
#include threadclass XThread {
public:virtual void Start() {is_exit_ false;th_ std::thread(XThread::Main, this);}virtual void Stop() {is_exit_ true;Wait();}virtual void Wait() {if (th_.joinable())th_.join();}bool is_exit() {return is_exit_;}private:virtual void Main() 0; // 纯虚函数必须要在基类中实现std::thread th_;bool is_exit_ false; // 符合谷歌代码风格私有成员变量后缀加 _
};thread_class.cpp #include iostream
#include thread
#include string
#include XThread.husing namespace std;/*
class MyThread {
public:// 入口线程函数void Main() {cout MyThread Main name : age;}string name;int age 0;
};
*/class TestXThread : public XThread {
public:void Main() override {cout TestXThread Main begin endl;while (!is_exit()) {this_thread::sleep_for(100ms);cout . flush; // 添加 flush 是为了确保 . 正常输出}cout \nTestXThread Main end endl;}string name;
};int main(int argc, char* argv[]) {TestXThread testth;testth.name TestXThread name ;testth.Start();this_thread::sleep_for(3s);testth.Stop();testth.Wait();getchar();/*MyThread myth;myth.name Test name;myth.age 20;thread th(MyThread::Main, myth);th.join();*/return 0;
}控制台输出 TestXThread Main begin
............................
TestXThread Main end7. lambda 临时函数作为线程入口 lambda 函数基本格式 [捕捉列表] (参数) mutable - 返回值类型 {函数体} thread_lambda.cpp #include iostream
#include thread
#include stringusing namespace std;class TestLambda {
public:void Start() {thread th([this]() {cout name name endl; });th.join();}string name Test Lambda;
};int main(int argc, char* argv[]) {thread th([](int i) {cout test lambda i endl;}, 123);th.join();TestLambda test;test.Start();return 0;
}控制台输出 test lambda 123
name Test Lambda8. call_once 多线程调用函数只进入一次 初始化函数可以在每一个类型的构造里都调用一遍不用明确区分代码可读性提升 call_once.cpp #include iostream
#include thread
#include string
#include mutexusing namespace std;void SystemInit() {cout Call SystemInit endl;
}void CallOnceSystemInit() {static std::once_flag flag; // 通过 flag 区分是否只调用一次std::call_once(flag, SystemInit);
}int main(int argc, char* argv[]) {CallOnceSystemInit();CallOnceSystemInit();for (int i 0; i 3; i) {thread th(CallOnceSystemInit);th.detach();}getchar();return 0;
}控制台输出 Call SystemInit
