NAME

Linux::FD::Event - Event filehandles for Linux

VERSION

version 0.016

SYNOPSIS

 use Linux::FD::Event;
 
 my $foo = Linux::FD::Event->new(42);
 if (fork) {
     say $foo->get while sleep 1
 }
 else {
     $foo->add($_) while <>;
 }

DESCRIPTION

This creates an eventfd object that can be used as an event wait/notify mechanism by userspace applications, and by the kernel to notify userspace applications of events. The object contains an unsigned 64-bit integer counter that is maintained by the kernel. It has two modes, default and semaphore, that differ only in get behavior as described below.

METHODS

new($initial_value, @flags)

This creates a new eventfd filehandler. The counter is initialized with the value specified in the argument $initial_value. @flags is an optional list of flags, currently limited to 'non-blocking' (requires Linux 2.6.27), and 'semaphore' (requires Linux 2.6.30).

get()

If the eventfd counter has a non-zero value, and 'semaphore' is not set, then a get returns 64 bit unsigned integer containing that value, and the counter's value is reset to zero. If 'semaphore' is set, it decrements the counter by one and returns one. In either case, if the counter is zero at the time of the get, then the call either blocks until the counter becomes non-zero, or fails with the error EAGAIN if the file handle has been made non-blocking.

add($value)

A add call adds the 64 bit unsigned integer value $value to the counter. The maximum value that may be stored in the counter is the largest unsigned 64-bit value minus 1 (i.e., 0xfffffffffffffffe). If the addition would cause the counter's value to exceed the maximum, then the add either blocks until a get is performed on the file descriptor, or fails with the error EAGAIN if the file descriptor has been made non-blocking. A add will fail with the error EINVAL if an attempt is made to write the value 0xffffffffffffffff.

AUTHOR

Leon Timmermans <leont@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2010 by Leon Timmermans.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.