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_SYMBOL
void *event_self_cbarg(void);