| Note: these documents may be out of date. Do not use as reference! |
To see what is currently happening visit http://www.perl6.org/
Common Callback API for all AIO calls.
Maintainer: Uri Guttman <uri@sysarch.com> Date: 25 Sep 2000 Mailing List: perl6-language-flow@perl.org Number: 321 Version: 1 Status: Developing
This RFC addresses the way callbacks are requested in the Advanced I/O (AIO) system and how they get called. The goal is to have a common callback style across the board.
There are several places in Perl where callbacks are needed. These include socket I/O events, asynchonous file I/O, signals, timers, plain events, etc. This RFC proposes a common API for requesting those callbacks in order to keep this consistant in all those places.
A callback currently can be registered in %SIG with a code ref as do Perl/Tk and Event.pm. But there are time you want to have an object oriented callback and that requires an object and a method. Event.pm handles this with a anon list instead of the code ref. Its first element is the object and the second is the method.
A solution which simplifies this and make calback code more consistant is to allow either a code ref or an object as the single primary argument to the call back API. The method called with the object is defaulted to a name that is appropriate for the type of callback. That method can be overridden with an optional argument.
For example, a read event would default to a method named 'readable', and a socket connect event would default to 'connected'.
Here are two possible APIs, the first based on I/O handle objects from RFC 14 and the second on the AIO syntax:
$obj = bless {}, 'Foo' ;
# these are I/O handle object based calls
$fh->read_event( 'cb' => $obj ) ;
$fh->write_event( 'cb' => $obj, 'method' => 'my_write_method' ) ;
# this is an AIO class call
AIO::read_event( 'fh' => $fh, 'cb' => \&my_callback ) ;
sub my_callback {
my ( $fh ) = @_ ;
print "i can read $fh from package main::\n" ;
}
package Foo ;
sub readable {
my ( $self, $fh ) = @_ ;
print "i can read $fh\n" ;
}
sub my_write_method {
my ( $self, $fh ) = @_ ;
print "i can write $fh\n" ;
}
Most callbacks will also allow an optional timeout which would use the the 'timed_out' method by default. You can override that method name with the 'timeout_method' argument.
# 10 second timeout
AIO::read_event( 'fh' => $fh, 'cb' => $obj, 'timeout' => 10 ) ;
package Foo ;
sub readable {
my ( $self, $fh ) = @_ ;
print "i can read $fh\n" ;
}
sub timed_out {
my ( $self, $fh ) = @_ ;
print "$fh has had no data in a while\n" ;
}
None.
None.
Event.pm: XS based event loop module.
RFC 14: Modify open() to support FileObjects and Extensibility
RFC 47: Universal Asynchronous I/O
RFC 60: Safe Signals
RFC 86: IPC Mailboxes for Threads and Signals
RFC 87: Timers and Timeouts