A timer based on timerfd and epoll

原始碼獲取

• github - HighPrecisionTimer

HighPrecisionTimer

This is a millisecond-level timer implemented with timerfd+epoll on Linux, and the demo is developed using Qt.

how to use

• I need to create a timer that runs periodically with millisecond precision. The timer supports setting the running period and a callback function for timeout. Additionally, the timer provides interfaces for starting the timer, stopping the timer, and setting the timer interval.
• follow this step

HighPrecisionTimer timer;
/// mill second: 40
timer.setInterval(40);

/// ... replace your call back func
timer.setCallback(...);

/// start timer
/// true - the timer timeout function execution is located in a separate thread
/// false - the timer timeout function execution is not in a separate thread.
timer.start(true);

/// do something
...

/// stop timer
timer.stop();

dmeo

• you can get the demo from TDDMUser header file and source file.

example

• results on Manjaro
  

enjoy the soure

#pragma once
#include <sys/epoll.h>
#include <sys/timerfd.h>
#include <unistd.h>
#include <iostream>
#include <fcntl.h>
#include <cstring>
#include <thread>
#include <functional>
#include <atomic>
#include <chrono>
#include <mutex>

class HighPrecisionTimer
{
    enum 
    {

        MAXNUM = 20,
    };
public:
    using Callback = std::function<void()>;

    HighPrecisionTimer() : m_running(false), m_interval(1000)
    {
        epoll_fd = epoll_create(1);
        timer_fd = timerfd_create(CLOCK_MONOTONIC, 0);
        fcntl(timer_fd, F_SETFL, O_NONBLOCK);
    }

    ~HighPrecisionTimer()
    {
        stop();
        close(timer_fd);
        close(epoll_fd);
    }

    void setInterval(uint64_t ms)
    {
        m_interval = ms;
    }

    void start(bool isInThread)
    {
        if(true == m_running)
        {
            return;
        }

        m_running = true;
        if (true == isInThread)
        {
            m_workerThread = new std::thread(&HighPrecisionTimer::run, this);
            return;
        }       

        run();
    }

    void stop()
    {
        m_running = false;
        if (m_workerThread)
        {
            if (m_workerThread->joinable())
            {
                m_workerThread->join();
            }
            delete m_workerThread;  
        }

        m_workerThread= nullptr;

    }

    /// uevi
    void setCallback(Callback cb)
    {
        m_onTimeoutFunc = std::move(cb);
    }

private:
    void run()
    {
        struct itimerspec new_value;
        new_value.it_value.tv_sec = m_interval / 1000;
        new_value.it_value.tv_nsec = (m_interval % 1000) * 1000000;
        new_value.it_interval.tv_sec = m_interval / 1000;
        new_value.it_interval.tv_nsec = (m_interval % 1000) * 1000000;

        timerfd_settime(timer_fd, 0, &new_value, nullptr);

        struct epoll_event ev;
        struct epoll_event events[MAXNUM];
        ev.data.fd = timer_fd;
        ev.events = EPOLLIN | EPOLLET;
        epoll_ctl(epoll_fd, EPOLL_CTL_ADD, timer_fd, &ev); // 新增到epoll事件集合

        uint64_t exp = 0;
        ssize_t s = 0;

        while (m_running)
        {
            int num = epoll_wait(epoll_fd, events, MAXNUM, -1);
            assert(num >= 0);

            for (int i = 0; i < num; ++i)
            {
                if (events[i].events & EPOLLIN)
                {
                    if (events[i].data.fd == timer_fd)
                    {
                        s = read(events[i].data.fd, &exp, sizeof(uint64_t)); // 需要讀出uint64_t大小, 不然會發生錯誤
                        assert(s == sizeof(uint64_t));
                        
                        if (m_onTimeoutFunc)
                        {
                            m_onTimeoutFunc();
                        }
                    }
                }
            }
        }

        epoll_ctl(epoll_fd, EPOLL_CTL_DEL, timer_fd, &ev);

        // 停止定時器
        stopTimer();
    }

    void stopTimer()
    {
        struct itimerspec new_value;
        memset(&new_value, 0, sizeof(new_value)); // 設定it_value為0
        timerfd_settime(timer_fd, 0, &new_value, nullptr); // 這將停止定時器
    }

    int epoll_fd{0};
    int timer_fd{0};
    std::thread* m_workerThread{nullptr};
    Callback m_onTimeoutFunc{nullptr};
    std::atomic<bool> m_running{false};
    /// 
    uint64_t m_interval{40};
};