epoll 定时器

news2024/10/6 4:01:16

参考：

Linux下使用epoll监听定时器-CSDN博客

但是这个用的是gettimeofday。

本人使用的是

#include <stdlib.h>
#include<stdio.h>
#include <sys/timerfd.h>
#include <sys/epoll.h>
#include <unistd.h>
#include <sys/time.h>
#include <stdint.h>

void timer_expires(void)
{
    struct timespec curr;
    static struct timespec start;
    static int first_call = 1;
    if (first_call)
    {
        first_call = 0;
        if (clock_gettime(CLOCK_MONOTONIC, &start) == -1)
            perror("clock_gettime");
    }
    if (clock_gettime(CLOCK_MONOTONIC, &curr) == -1)
        perror("clock_gettime");
    int secs, nsecs;
    secs = curr.tv_sec - start.tv_sec;
    nsecs = curr.tv_nsec - start.tv_nsec;
    if (nsecs < 0)
    {
        secs--;
        nsecs += 1000000000;
    }
    printf("%d.%03d \n", secs, (nsecs + 500000) / 1000000);  //四舍五入纳秒转换为毫秒
}

int main(int argc, char const *argv[])
{
    int timefd = timerfd_create(CLOCK_MONOTONIC, 0);
    if (timefd == -1)
    {
        perror("timerfd_create failed");
    }

    struct itimerspec new_value = {};
    new_value.it_value.tv_sec = 1;
    new_value.it_value.tv_nsec = 0;

    new_value.it_interval.tv_sec = 5;
    new_value.it_interval.tv_nsec = 0;

    if (timerfd_settime(timefd, 0, &new_value, NULL) == -1)
    {
        perror("timerfd_settime failed");
    }
    printf("time start-----------\n");
    timer_expires();
    /*-------------------------------------------------------------------------*/
    struct epoll_event ev;
    ev.data.fd = timefd;
    ev.events = EPOLLIN; // 文件描述符可读的时候就触发

    int epollfd = epoll_create(EPOLL_CLOEXEC);
    if (epollfd == -1)
    {
        perror("epoll_create failed");
    }

    epoll_ctl(epollfd, EPOLL_CTL_ADD, timefd, &ev);

    /* int epoll_wait（int epfd，struct epoll_event * events， int maxevents，int timeout）;
         epfd ：epoll文件描述符
　　events ：接口的返回参数，一般都是一个数组，数组长度大于等于maxevents。
　　maxevents：期望捕获的事件的个数。
　　timeout ：超时时间(>=0)，单位是毫秒ms，-1表示阻塞，0表示不阻塞
   */
    const int maxEvents = 1; // 必须大于1
    struct epoll_event events[maxEvents];
    int buf[2];
    int ret = 0;
    int i =0;
    while (1)
    {
        int nfd = epoll_wait(epollfd, events, maxEvents, -1);
        if (nfd == -1)
            perror("epoll_wait failed");
        for (i = 0; i < nfd; ++i)
        {
            ret = read(events[i].data.fd, buf, sizeof(buf));
            if (ret < 0)
                perror("epoll callback read error");
            timer_expires();
        }
    }

    return 0;
}