typedef enum { ... } SilcTaskEvent;

    SILC Task event types.  The event type indicates the occurred
    event of the task.  This type will be given as argument to the
    SilcTaskCallback function to indicate the event for the caller.
    The SILC_TASK_READ and SILC_TASK_WRITE may be set by the caller
    of the silc_schedule_set_listen_fd, if the caller needs to control
    the events for the task. The SILC_TASK_EXPIRE is set always only
    by the scheduler when timeout expires for timeout task.  The
    SILC_TASK_INTERRUPT is set for signal callback.

    typedef enum {
      SILC_TASK_READ         = 0x0001,               /* Reading */
      SILC_TASK_WRITE        = 0x0002,               /* Writing */
      SILC_TASK_EXPIRE       = 0x0004,               /* Timeout */
      SILC_TASK_INTERRUPT    = 0x0008,               /* Signal */
    } SilcTaskEvent;