timerfd_create/timerfd_settime/timerfd_gettime函数
一、timerfd系列的定时函数
#include <sys/timerfd.h>
int timerfd_create(int clockid, int flags);
int timerfd_settime(int fd, int flags, const struct itimerspec *new_value, struct itimerspec *old_value);
int timerfd_gettime(int fd, struct itimerspec *curr_value);① timerfd_create函数创建定时器对象，这个定时器对象与返回值timerfd进行绑定。
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第一个参数clockid如果指定为 CLOCK_REALTIME 时表示定时器为实时系统时钟，如果指定为CLOCK_MONOTONIC 表示一个相对单调递增的时钟； 第二个参数flags可以指定为TFD_NONBLOCK或者 TFD_CLOEXEC。 |
② timerfd_settime函数可以设置定时器对象
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第一个参数就是timerfd_create函数的返回值 第二个参数指定为0时表示启动相对定时器（此时第三个参数new_value.it_value就要指定为相对时间，假如当前时间为8:00，希望定时器在8:10响的话就设置new_value.it_value为10分钟） 当指定为TFD_TIMER_ABSTIME表示绝对定时器（第三个参数new_value.it_value要指定为绝对时间，希望定时器在8:10响的话就指定new_value.it_value为8:10） |
③ timerfd_gettime函数的第1个参数是timerfd_create函数的返回值，第二个参数curr_value.it_value表示当前时间到第一次触发剩余的时间。
1、 timerfd_create, timerfd_settime 和 read函数举例：首先设置单次触发定时器，就是设置 struct itimerspec new_value 结构体的成员new_value.it_interval.tv_sec 和 new_value.it_interval.tv_nsec 的值为0
#define _POSIX_C_SOURCE 199309L
#include <sys/timerfd.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#define handle_error(msg) \
do { perror(msg); exit(EXIT_FAILURE); } while (0)
int main(void)
{
uint64_t exp = 0;
int timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK);
if (timerfd == -1)
{
handle_error("timerfd_create");
}
struct itimerspec new_value = {};
new_value.it_value.tv_sec = 10; // 2s
new_value.it_value.tv_nsec = 0;
new_value.it_interval.tv_sec = 0; // one shot
new_value.it_interval.tv_nsec = 0;
/*启动timerfd绑定的定时器，0表示启动相对定时器，时间=当前时间+new_value.it_value，NULL表示旧的定时值*/
if (timerfd_settime(timerfd, 0, &new_value, NULL) == -1)
{
handle_error("timerfd_settime");
}
printf("timer started\n");
while (1)
{
int ret = read(timerfd, &exp, sizeof(uint64_t));
if (ret == sizeof(uint64_t)) //
{
printf("ret: %d\n", ret);
printf("expired times: %llu\n", exp);
break;
}
}
return 0;
}2、如果设置 struct itimerspec new_value 结构体的成员new_value.it_interval.tv_sec = 5, new_value.it_interval.tv_nsec = 0，使得第一次触发后每隔5s再触发一次。
二、Epoll和Timerfd组合使用
#include <sys/epoll.h>
#include <sys/timerfd.h>
#include <time.h>
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#define MX_EVNTS 10
#define EPL_TOUT 3000
#define MX_CNT 5
struct param{
struct itimerspec its;
int tfd;
};
void *strt_eplth(void *arg)
{
struct epoll_event evnts[MX_EVNTS];
int *eplfd = (int *)arg;
int n = -1;
size_t i,cnt = 0;
while(1){
n = epoll_wait(*eplfd,evnts,MX_EVNTS,EPL_TOUT);
if(n == -1){
perror("epoll_wait() error");
break;
}else if(n == 0){
printf("time out %d sec expired\n",EPL_TOUT / 1000);
break;
}
for(i = 0; i < n;i++){
struct param *pm = (struct param *)(evnts[i].data.ptr);
printf("tfd: %d\ninitial expiration: %ld\ninterval: %ld\n\n",
pm->tfd,
(long)(pm->its.it_value.tv_sec),
(long)(pm->its.it_interval.tv_sec));
if(epoll_ctl(*eplfd,EPOLL_CTL_DEL,pm->tfd,NULL) != 0){
perror("epoll_ctl(DEL) error in thread");
break;
}
struct epoll_event ev;
ev.events = EPOLLIN | EPOLLET;
pm->its.it_value.tv_sec =
pm->its.it_value.tv_sec +
pm->its.it_interval.tv_sec;
ev.data.ptr = pm;
if(timerfd_settime(pm->tfd,TFD_TIMER_ABSTIME,&(pm->its),NULL) != 0){
perror("timerfd_settime() error in thread");
break;
}
if(epoll_ctl(*eplfd,EPOLL_CTL_ADD,pm->tfd,&ev) != 0){
perror("epoll_ctl(ADD) error in thread");
break;
}
}
if(++cnt == MX_CNT){
printf("cnt reached MX_CNT, %d\n",MX_CNT);
break;
}
}
close(*eplfd);
pthread_exit(NULL);
}
int create_timerfd(struct itimerspec *its,time_t interval)
{
int tfd = timerfd_create(CLOCK_MONOTONIC,TFD_NONBLOCK);
if(tfd < 0){
perror("timerfd_create() error");
return -2;
}
struct timespec nw;
if(clock_gettime(CLOCK_MONOTONIC,&nw) != 0){
perror("clock_gettime() error");
return -1;
}
its->it_value.tv_sec = nw.tv_sec + interval;
its->it_value.tv_nsec = 0;
its->it_interval.tv_sec = interval;
its->it_interval.tv_nsec = 0;
return tfd;
}
int main()
{
time_t INTERVAL = 2;
struct itimerspec its;
int tfd = create_timerfd(&its,INTERVAL);
if(tfd < 0)
return -1;
int eplfd = epoll_create1(0);
if(eplfd < 0){
perror("epoll_create1() error");
return -1;
}
struct param pm;
pm.its = its;
pm.tfd = tfd;
if(timerfd_settime(pm.tfd,TFD_TIMER_ABSTIME,&(pm.its),NULL) != 0){
perror("timerfd_settime() error");
return -1;
}
struct epoll_event ev;
ev.events = EPOLLIN | EPOLLET;
ev.data.ptr = ±
if(epoll_ctl(eplfd,EPOLL_CTL_ADD,pm.tfd,&ev) != 0){
perror("epoll_ctl() error");
return -1;
}
pthread_t pid;
if(pthread_create(&pid,NULL,strt_eplth,(void *)&eplfd) != 0){
perror("pthread_create() error");
return -1;
}
//// add another timerfd.
INTERVAL = 1;
struct itimerspec its2;
int tfd2 = create_timerfd(&its2,INTERVAL);
if(tfd2 < 0)
return -1;
struct param pm2;
pm2.its = its2;
pm2.tfd = tfd2;
if(timerfd_settime(pm2.tfd,TFD_TIMER_ABSTIME,&(pm2.its),NULL) != 0){
perror("timerfd_settime() error");
return -1;
}
struct epoll_event ev2;
ev2.events = EPOLLIN | EPOLLET;
ev2.data.ptr = &pm2;
if(epoll_ctl(eplfd,EPOLL_CTL_ADD,pm2.tfd,&ev2) != 0){
perror("epoll_ctl() error");
return -1;
}
if(pthread_join(pid,NULL) != 0){
perror("pthread_join() error");
return -1;
}
close(tfd);
close(tfd2);
return 0;
}
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