Re: [Libevent-users] fd=-1 events

[Alexander Smirnov <alexander@xxxxxxxxxx>]

Thank you, Nick.

Is it possible to achieve immediate action by using pipes ? Are they supported ?

On 13 Jan 2014, at 08:43, Nick Mathewson <nickm@xxxxxxxxxxxxx> wrote:

> On Fri, Jan 10, 2014 at 4:24 PM, Александр Смирнов <alexander@xxxxxxxxxx> wrote:
>> Greetings!
>> 
>> Thanks in advance for any help you are able to provide! I'm on my very start
>> with libevent.
>> 
>> As far as I understand libevent will instantly notify me about any event on
>> file descriptor.
>> 
>> But what with events which has no file descriptor (fd = -1) ?
>> 
>> Do I understand right that in blocking mode event_base_loop() will block
>> only on real events (based on existing fds) ? So event_active() will not
>> have any effect until some real event triggered ?
>> 
>> What I've managed to find out by myself:
>> * event_active() does nothing beside placing event on queue to process. so
>> it not assumes "immediate" action.
>> * event_add calls evmap_io_add which does nothing in case of fd<0
>> 
>> So there is no way to get immediate response for fd=-1 events ?
> 
> fd==-1 is used in libevent to indicate an event that has no fd --
> either because it is a timer-only event, or because it's used only
> with event_active().  It should not have EV_READ or EV_WRITE set.
> 
> In general, libevent doesn't have a good notion of "run immediately"
> -- the closest that it has is "run this event as part of processing
> active events" -- which causes the event to get invoked right away if
> the event loop is running, but not otherwise.
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