IO::Async::Loop::Select - use IO::Async with select(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 a select() call.

 use IO::Async::Loop::Select;

 my $loop = IO::Async::Loop::Select->new();

 $loop->add( ... );

 while(1) {
    my ( $rvec, $wvec, $evec ) = ('') x 3;
    my $timeout;

    $loop->pre_select( \$rvec, \$wvec, \$evec, \$timeout );
    my $ret = select( $rvec, $wvec, $evec, $timeout );
    $loop->post_select( $rvec, $evec, $wvec );


This subclass of IO::Async::Loop uses the select() syscall to perform read-ready and write-ready tests.

To integrate with an existing select()-based event loop, a pair of methods pre_select() and post_select() can be called immediately before and after a select() call. The relevant bit in the read-ready bitvector is always set by the pre_select() method, but the corresponding bit in write-ready vector is set depending on the state of the 'want_writeready' property. The post_select() method will invoke the on_read_ready() or on_write_ready() methods or callbacks as appropriate.


$loop = IO::Async::Loop::Select->new()

This function returns a new instance of a IO::Async::Loop::Select object. It takes no special arguments.


$loop->pre_select( \$readvec, \$writevec, \$exceptvec, \$timeout )

This method prepares the bitvectors for a select() call, setting the bits that notifiers registered by this loop are interested in. It will always set the appropriate bits in the read vector, but will only set them in the write vector if the notifier's want_writeready() property is true. Neither the exception vector nor the timeout are affected.


Scalar references to the reading, writing and exception bitvectors


Scalar reference to the timeout value

$loop->post_select( $readvec, $writevec, $exceptvec )

This method checks the returned bitvectors from a select() call, and calls any of the notification methods or callbacks that are appropriate.


Scalars containing the read-ready, write-ready and exception bitvectors

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

This method calls the pre_select() method to prepare the bitvectors for a select() syscall, performs it, then calls post_select() to process the result. It returns the total number of callbacks invoked by the post_select() method, or undef if the underlying select() syscall returned an error.



Paul Evans <>