macros of evtimer evsignal

event2/event.h中定义了evtimer和evsignal各六个宏定义，方便使用

/**   @name evtimer_* macros    Aliases for working with one-shot timer events *//**@{*/#define evtimer_assign(ev, b, cb, arg) \    event_assign((ev), (b), -1, 0, (cb), (arg))#define evtimer_new(b, cb, arg)        event_new((b), -1, 0, (cb), (arg))#define evtimer_add(ev, tv)     event_add((ev), (tv))#define evtimer_del(ev)         event_del(ev)#define evtimer_pending(ev, tv)     event_pending((ev), EV_TIMEOUT, (tv))#define evtimer_initialized(ev)     event_initialized(ev)/**@}*/

/**   @name evsignal_* macros   Aliases for working with signal events *//**@{*/#define evsignal_add(ev, tv)        event_add((ev), (tv))#define evsignal_assign(ev, b, x, cb, arg)          \    event_assign((ev), (b), (x), EV_SIGNAL|EV_PERSIST, cb, (arg))#define evsignal_new(b, x, cb, arg)             \    event_new((b), (x), EV_SIGNAL|EV_PERSIST, (cb), (arg))#define evsignal_del(ev)        event_del(ev)#define evsignal_pending(ev, tv)    event_pending((ev), EV_SIGNAL, (tv))#define evsignal_initialized(ev)    event_initialized(ev)/**@}*/

/**   A callback function for an event.   It receives three arguments:   @param fd An fd or signal   @param events One or more EV_* flags   @param arg A user-supplied argument.   @see event_new() */typedef void (*event_callback_fn)(evutil_socket_t, short, void *);

/**  Return a value used to specify that the event itself must be used as the callback argument.  The function event_new() takes a callback argument which is passed  to the event's callback function. To specify that the argument to be  passed to the callback function is the event that event_new() returns,  pass in the return value of event_self_cbarg() as the callback argument  for event_new().  For example:  <pre>      struct event *ev = event_new(base, sock, events, callback, %event_self_cbarg());  </pre>  For consistency with event_new(), it is possible to pass the return value  of this function as the callback argument for event_assign() &ndash; this  achieves the same result as passing the event in directly.  @return a value to be passed as the callback argument to event_new() or  event_assign().  @see event_new(), event_assign() */EVENT2_EXPORT_SYMBOLvoid *event_self_cbarg(void);