1 struct event {
 2     TAILQ_ENTRY(event) ev_active_next;
 3     TAILQ_ENTRY(event) ev_next;
 4     /* for managing timeouts */
 5     union {
 6         TAILQ_ENTRY(event) ev_next_with_common_timeout;
 7         int min_heap_idx;
 8     } ev_timeout_pos;
 9     evutil_socket_t ev_fd;
10 
11     struct event_base *ev_base;
12 
13     union {　　　　　　　　　　　　　　　　// I/O事件和信号事件不能同时设置
14         /* used for io events */
15         struct {
16             TAILQ_ENTRY(event) ev_io_next;
17             struct timeval ev_timeout;
18         } ev_io;
19 
20         /* used by signal events */
21         struct {
22             TAILQ_ENTRY(event) ev_signal_next;
23             short ev_ncalls;
24             /* Allows deletes in callback */
25             short *ev_pncalls;
26         } ev_signal;
27     } _ev;
28 
29     short ev_events;
30     short ev_res;        /* result passed to event callback */
31     short ev_flags;
32     ev_uint8_t ev_pri;    /* smaller numbers are higher priority */
33     ev_uint8_t ev_closure;
34     struct timeval ev_timeout;
35 
36     /* allows us to adopt for different types of events */
37     void (*ev_callback)(evutil_socket_t, short, void *arg);
38     void *ev_arg;
39 };

 1 /**
 2  * @name event flags
 3  *
 4  * Flags to pass to event_new(), event_assign(), event_pending(), and
 5  * anything else with an argument of the form "short events"
 6  */
 7 /**@{*/
 8 /** Indicates that a timeout has occurred.  It‘s not necessary to pass
 9  * this flag to event_for new()/event_assign() to get a timeout. */
10 #define EV_TIMEOUT    0x01
11 /** Wait for a socket or FD to become readable */
12 #define EV_READ       0x02
13 /** Wait for a socket or FD to become writeable */
14 #define EV_WRITE      0x04
15 /** Wait for a POSIX signal to be raised*/
16 #define EV_SIGNAL     0x08
17 /**
18  * Persistent event: won‘t get removed automatically when activated.
19  *
20  * When a persistent event with a timeout becomes activated, its timeout
21  * is reset to 0.
22  */
23 #define EV_PERSIST    0x10
24 /** Select edge-triggered behavior, if supported by the backend. */
25 #define EV_ET         0x20
26 /**@}*/

1 #define EVLIST_TIMEOUT  0x01 　// event在time堆中
2 #define EVLIST_INSERTED 0x02 　// event在已注册事件链表中
3 #define EVLIST_SIGNAL   0x04 　// 未见使用
4 #define EVLIST_ACTIVE   0x08 　// event在激活链表中
5 #define EVLIST_INTERNAL 0x10 　// 内部使用标记
6 #define EVLIST_INIT     0x80 　// event已被初始化

void (*ev_callback)(int fd, short events, void *arg)

1 void
2 event_set(struct event *ev, evutil_socket_t fd, short events,
3       void (*callback)(evutil_socket_t, short, void *), void *arg)
4 {
5     int r;
6     r = event_assign(ev, current_base, fd, events, callback, arg);
7     EVUTIL_ASSERT(r == 0);
8 }

 1 struct event *
 2 event_new(struct event_base *base, evutil_socket_t fd, short events, void (*cb)(evutil_socket_t, short, void *), void *arg)
 3 {
 4     struct event *ev;
 5     ev = mm_malloc(sizeof(struct event));
 6     if (ev == NULL)
 7         return (NULL);
 8     if (event_assign(ev, base, fd, events, cb, arg) < 0) {
 9         mm_free(ev);
10         return (NULL);
11     }
12 
13     return (ev);
14 }

 1 int
 2 event_base_set(struct event_base *base, struct event *ev)
 3 {
 4     /* Only innocent events may be assigned to a different base */
 5     if (ev->ev_flags != EVLIST_INIT)
 6         return (-1);
 7 
 8     _event_debug_assert_is_setup(ev);
 9 
10     ev->ev_base = base;
11     ev->ev_pri = base->nactivequeues/2;
12 
13     return (0);
14 }

 1 /*
 2  * Set‘s the priority of an event - if an event is already scheduled
 3  * changing the priority is going to fail.
 4  */
 5 
 6 int
 7 event_priority_set(struct event *ev, int pri)
 8 {
 9     _event_debug_assert_is_setup(ev);
10 
11     if (ev->ev_flags & EVLIST_ACTIVE)
12         return (-1);
13     if (pri < 0 || pri >= ev->ev_base->nactivequeues)
14         return (-1);
15 
16     ev->ev_pri = pri;
17 
18     return (0);
19 }

 1 void
 2 event_free(struct event *ev)
 3 {
 4     _event_debug_assert_is_setup(ev);
 5 
 6     /* make sure that this event won‘t be coming back to haunt us. */
 7     event_del(ev);
 8     _event_debug_note_teardown(ev);
 9     mm_free(ev);
10 
11 }

 1 /**
 2    A callback function for an event.
 3 
 4    It receives three arguments:
 5 
 6    @param fd An fd or signal
 7    @param events One or more EV_* flags
 8    @param arg A user-supplied argument.
 9 
10    @see event_new()
11  */
12 typedef void (*event_callback_fn)(evutil_socket_t, short, void *);

 1 /**
 2    @name evtimer_* macros
 3 
 4     Aliases for working with one-shot timer events */
 5 /**@{*/
 6 #define evtimer_assign(ev, b, cb, arg)  7     event_assign((ev), (b), -1, 0, (cb), (arg))
 8 #define evtimer_new(b, cb, arg)           event_new((b), -1, 0, (cb), (arg))
 9 #define evtimer_add(ev, tv)               event_add((ev), (tv))
10 #define evtimer_del(ev)                   event_del(ev)
11 #define evtimer_pending(ev, tv)           event_pending((ev), EV_TIMEOUT, (tv))
12 #define evtimer_initialized(ev)           event_initialized(ev)
13 /**@}*/

 1 /**
 2    @name evsignal_* macros
 3 
 4    Aliases for working with signal events
 5  */
 6 /**@{*/
 7 #define evsignal_add(ev, tv)        event_add((ev), (tv))
 8 #define evsignal_assign(ev, b, x, cb, arg)             9     event_assign((ev), (b), (x), EV_SIGNAL|EV_PERSIST, cb, (arg))
10 #define evsignal_new(b, x, cb, arg)                11     event_new((b), (x), EV_SIGNAL|EV_PERSIST, (cb), (arg))
12 #define evsignal_del(ev)            event_del(ev)
13 #define evsignal_pending(ev, tv)    event_pending((ev), EV_SIGNAL, (tv))
14 #define evsignal_initialized(ev)    event_initialized(ev)
15 /**@}*/