---
name: "IO::Async::Loop::Poll"
section: "3pm"
platform: "linux"
package: "libio-async-perl"
version: "0.804-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/IO::Async::Loop::Poll"
---

# IO::Async::Loop::Poll(3pm)

use "IO::Async" with "poll(2)"

## NAME

"IO::Async::Loop::Poll" - use "IO::Async" with "[poll(2)](/poll/2.md)"

## SYNOPSIS

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;
   }
```

## DESCRIPTION

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.

## CONSTRUCTOR

### new

```
   $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.

## METHODS

### post\_poll

```
   $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.

### loop\_once

```
   $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.

## AUTHOR

Paul Evans \<leonerd@leonerd.org.uk\>