DOKK / manpages / debian 12 / libio-async-perl / IO::Async::Loop::Poll.3pm.en
IO::Async::Loop::Poll(3pm) User Contributed Perl Documentation IO::Async::Loop::Poll(3pm)

"IO::Async::Loop::Poll" - use "IO::Async" with "poll(2)"

Normally an instance of this class would not be directly constructed by a program. It may however, be useful for runinng IO::Async with an existing program already using an "IO::Poll" object.

   use IO::Poll;
   use IO::Async::Loop::Poll;
   my $poll = IO::Poll->new;
   my $loop = IO::Async::Loop::Poll->new( poll => $poll );
   $loop->add( ... );
   while(1) {
      my $timeout = ...
      my $ret = $poll->poll( $timeout );
      $loop->post_poll;
   }

This subclass of IO::Async::Loop uses the poll(2) system call to perform read-ready and write-ready tests.

By default, this loop will use the underlying "poll()" system call directly, bypassing the usual IO::Poll object wrapper around it because of a number of bugs and design flaws in that class; namely

  • <https://rt.cpan.org/Ticket/Display.html?id=93107> - IO::Poll relies on stable stringification of IO handles
  • <https://rt.cpan.org/Ticket/Display.html?id=25049> - IO::Poll->poll() with no handles always returns immediately

However, to integrate with existing code that uses an "IO::Poll" object, a "post_poll" can be called immediately after the "poll" method that "IO::Poll" object. The appropriate mask bits are maintained on the "IO::Poll" object when notifiers are added or removed from the loop, or when they change their "want_*" status. The "post_poll" method inspects the result bits and invokes the "on_read_ready" or "on_write_ready" methods on the notifiers.

   $loop = IO::Async::Loop::Poll->new( %args )

This function returns a new instance of a "IO::Async::Loop::Poll" object. It takes the following named arguments:

"poll"
The "IO::Poll" object to use for notification. Optional; if a value is not given, the underlying "IO::Poll::_poll()" function is invoked directly, outside of the object wrapping.

   $count = $loop->post_poll

This method checks the returned event list from a "IO::Poll::poll" call, and calls any of the notification methods or callbacks that are appropriate. It returns the total number of callbacks that were invoked; that is, the total number of "on_read_ready" and "on_write_ready" callbacks for "watch_io", and "watch_time" event callbacks.

   $count = $loop->loop_once( $timeout )

This method calls the "poll" method on the stored "IO::Poll" object, passing in the value of $timeout, and then runs the "post_poll" method on itself. It returns the total number of callbacks invoked by the "post_poll" method, or "undef" if the underlying "poll" method returned an error.

Paul Evans <leonerd@leonerd.org.uk>

2022-08-19 perl v5.34.0