Libevent，无需更改事件循环即可动态添加或删除事件

我正面临一个问题，可能会误解这句话的真正含义“应用程序只需调用event_dispatch（），然后添加或删除事件动态而不必更改事件循环。“或者我找不到如何做到这一点的正确文件。嗯，问题是我认为我应该可以在event_dispatch（）运行后将事件添加到事件循环中，但我无法使其工作。下面是代码：Libevent，无需更改事件循环即可动态添加或删除事件

#include <event2/event.h> 
#include <event2/buffer.h> 
#include <event2/bufferevent.h> 

#include <stdio.h> 

static int n_calls = 0; 
static int n_calls2 = 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 cb_func2(evutil_socket_t fd, short what, void *arg) 
{ 
    struct event *me = arg; 

    printf("cb_func2 called %d times so far.\n", ++n_calls2); 

    if (n_calls2 > 100) 
     event_del(me); 
} 

int main(int argc, char const *argv[]) 
{ 
    struct event_base *base; 
    enum event_method_feature f; 

    base = event_base_new(); 
    if (!base) { 
     puts("Couldn't get an event_base!"); 
    } else { 
     printf("Using Libevent with backend method %s.", 
      event_base_get_method(base)); 
     f = event_base_get_features(base); 
     if ((f & EV_FEATURE_ET)) 
      printf(" Edge-triggered events are supported."); 
     if ((f & EV_FEATURE_O1)) 
      printf(" O(1) event notification is supported."); 
     if ((f & EV_FEATURE_FDS)) 
      printf(" All FD types are supported."); 
     puts(""); 
    } 

    struct timeval one_sec = { 1, 0 }; 
    struct timeval two_sec = { 2, 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, NULL); 
    event_add(ev, &one_sec); 

    event_base_dispatch(base); 

    // This event (two_sec) is never fired if I add it after calling event_base_dispatch. 
    // If I add it before calling event_base_dispatch it works as the other event (one_sec) also does. 
    ev = event_new(base, -1, EV_PERSIST, cb_func2, NULL); 
    event_add(ev, &two_sec); 

    return 0; 
}

来源

2015-03-19 vicaba

现在我明白了...我不知道为什么，但我在想，在事件循环开始在另一个线程或类似的东西运行。我现在看到，我试图做的事情没有意义。您可以在回调中添加事件，即循环运行时。当你启动事件循环时，它永远不会返回，所以之后的所有事情都不会被调用（除非你停止事件循环）

来源

2015-03-19 21:26:13 vicaba

Libevent，无需更改事件循环即可动态添加或删除事件

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