c-libevent:使计时器持久化

Question

我有以下代码：

#include <stdio.h>
#include <sys/time.h>
#include <event.h>
void say_hello(int fd, short event, void *arg){
printf("Hellon");
}
int main(int argc, const char* argv[])
{
struct event ev;
struct timeval tv;
tv.tv_sec = 3;
tv.tv_usec = 0;
event_init();
evtimer_set(&ev,say_hello,NULL);
evtimer_add(&ev, &tv);
event_dispatch();
return 0;
}

问题是"你好"被打印一次，然后程序退出。。。

我希望它无限期地输出"你好"。

如何做到这一点？非常感谢，

Answer 1

只是为了澄清Basile的解决方案：

我也很困惑，直到我意识到本文中的">计时器"指的是单次计时器隔计时器；这需要libevent中的EV_PERSIST标志。

struct timeval time;
time.tv_sec = 1;
time.tv_usec = 0;
event_set(&my_event, 0, EV_PERSIST, my_function, NULL);
evtimer_add(&my_event, &time);

Answer 2

将main中的代码更改为读取

evtimer_set(&ev,say_hello,&ev);

并使您的say_hello函数

void say_hello(int fd, short event, void *arg){
struct event *ev = arg;
struct timeval tv;

printf("Hellon");
tv.tv_sec = 3;
tv.tv_usec = 0;
evtimer_add(ev, &tv);
}

Answer 3

以下是libevent2:的示例

#include <event2/event.h>
static int n_calls = 0;
void cb_func(evutil_socket_t fd, short what, void *arg)
{
struct event *me = arg;
printf("cb_func called %d times so far.n", ++n_calls);
if (n_calls > 100)
event_del(me);
}
void run(struct event_base *base)
{
struct timeval one_sec = { 1, 0 };
struct event *ev;
/* We're going to set up a repeating timer to get called called 100
times. */
ev = event_new(base, -1, EV_PERSIST, cb_func, event_self_cbarg());
event_add(ev, &one_sec);
event_base_dispatch(base);
}

Answer 4

您读过evtimer_set(3)手册页吗？请再读一遍。

您可能想要使用标志EV_PERSIST或从say_hello回调中调用evtimer_add。

Answer 5

#include <stdio.h>
#include "ev.h"
static void timer_cback_caller(EV_P_ ev_timer* w, int revents)
{
const int new_timeout_in_ms = 1200; // new delay between timer ticks
printf("timer tickn");
w->repeat = new_timeout_in_ms / 1000.;
ev_timer_again(EV_A_ w);
}

int main()
{
struct ev_loop *loop = ev_default_loop(0);
ev_timer timer;
const int start_delay_in_ms = 1000; // delay before first timer tick
const int timeout_in_ms = 1500; // delay between every timer tick
ev_timer_init(&timer, timer_cback_caller, start_delay_in_ms/1000., timeout_in_ms/1000.);
ev_timer_start(loop, &timer);
ev_run(loop, 0); // will never return
return 0;
}

libev文档中的更多示例