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.IX Title "Linux::FD::Event 3pm"
.TH Linux::FD::Event 3pm 2024-03-07 "perl v5.38.2" "User Contributed Perl Documentation"
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.SH NAME
Linux::FD::Event \- Event filehandles for Linux
.SH VERSION
.IX Header "VERSION"
version 0.016
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& use Linux::FD::Event;
\& 
\& my $foo = Linux::FD::Event\->new(42);
\& if (fork) {
\&     say $foo\->get while sleep 1
\& }
\& else {
\&     $foo\->add($_) while <>;
\& }
.Ve
.SH DESCRIPTION
.IX Header "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 \f(CW\*(C`get\*(C'\fR behavior as described below.
.SH METHODS
.IX Header "METHODS"
.ie n .SS "new($initial_value, @flags)"
.el .SS "new($initial_value, \f(CW@flags\fP)"
.IX Subsection "new($initial_value, @flags)"
This creates a new eventfd filehandler. The counter is initialized with the value specified in the argument \f(CW$initial_value\fR. \f(CW@flags\fR is an optional list of flags, currently limited to \f(CW\*(Aqnon\-blocking\*(Aq\fR (requires Linux 2.6.27), and \f(CW\*(Aqsemaphore\*(Aq\fR (requires Linux 2.6.30).
.SS \fBget()\fP
.IX Subsection "get()"
If the eventfd counter has a non-zero value, and \f(CW\*(Aqsemaphore\*(Aq\fR is not set, then a \f(CW\*(C`get\*(C'\fR returns 64 bit unsigned integer containing that value, and the counter's value is reset to zero. If \f(CW\*(Aqsemaphore\*(Aq\fR is set, it decrements the counter by one and returns one. In either case, if the counter is zero at the time of the \f(CW\*(C`get\*(C'\fR, 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.
.SS add($value)
.IX Subsection "add($value)"
A \f(CW\*(C`add\*(C'\fR call adds the 64 bit unsigned integer value \f(CW$value\fR 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 \f(CW\*(C`add\*(C'\fR either blocks until a \f(CW\*(C`get\*(C'\fR is performed on the file descriptor, or fails with the error EAGAIN if the file descriptor has been made non-blocking. A \f(CW\*(C`add\*(C'\fR will fail with the error EINVAL if an attempt is made to write the value 0xffffffffffffffff.
.SH AUTHOR
.IX Header "AUTHOR"
Leon Timmermans <leont@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This software is copyright (c) 2010 by Leon Timmermans.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.