需求：

实现异步定时器，不干扰其它线程

实现：

使用select作为超时API，但一定程度增加系统payload

代码：

select_timer.hpp

#ifndef SRC_SELECT_TIMER_HPP_
#define SRC_SELECT_TIMER_HPP_
#include <sys/time.h>
#include <iostream>
#include <functional>
#include <thread>
using namespace std;
class select_timer {
public:
  select_timer(function<void()>task, int seconds) {
    thd_ = thread([this, &task, seconds] {
      while (true) {
        task();
        do_select_timeout(seconds);
      }
    });
  }
  ~select_timer() {
    thd_.detach();
  }
private:
  void do_select_timeout(unsigned int seconds) {
    struct timeval tv = {0};
    tv.tv_sec = seconds;
    int err = 0;
    do {
      err = select(0, nullptr, nullptr, nullptr, &tv);
    }while (err < 0 && EINTR == errno);
  }
private:
  thread thd_;
};




#endif /* SRC_SELECT_TIMER_HPP_ */

main.cpp

#include "select_timer.hpp"
#include <iostream>
#include <chrono>
void fun() {
    cout << "I am fun()." << endl;
}
void fun1() {
    while (true) {
        cout << "I am fun1." << endl;
        this_thread::sleep_for(chrono::seconds(1));
    }
}
int main() {
    auto f = fun;
    select_timer(f, 1);
    thread th(fun1);
    if (th.joinable()) {
        th.join();
    }

    return 0;
}

make.sh

g++ -std=c++17 -g -o Test main.cpp  select_timer.hpp -pthread