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.\" ========================================================================
.\"
.IX Title "IO::Epoll 3pm"
.TH IO::Epoll 3pm "2014-08-15" "perl v5.20.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
IO::Epoll \- Scalable IO Multiplexing for Linux 2.5.44 and higher
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&    # Low level interface
\&    use IO::Epoll;
\&
\&    $epfd = epoll_create(10);
\&
\&    epoll_ctl($epfd, EPOLL_CTL_ADD, fileno STDIN, EPOLLIN) >= 0
\&        || die "epoll_ctl: $!\en";
\&    epoll_ctl($epfd, ...);
\&
\&    $events = epoll_wait($epfd, 10, 1000); # Max 10 events returned, 1s timeout
\&
\&    # High level IO::Poll emulation layer
\&    use IO::EPoll qw(:compat);
\&
\&    $poll = new IO::Epoll;
\&
\&    $poll\->mask($input_handle => POLLIN);
\&    $poll\->mask($output_handle => POLLOUT);
\&
\&    $poll\->poll($timeout);
\&
\&    $ev = $poll\->events($input);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CWepoll(4)\fR subsystem is a new, (currently) Linux-specific variant of
\&\f(CWpoll(2)\fR.  It is designed to offer O(1) scalability over large numbers of
watched file descriptors.  You will need at least version 2.5.44 of Linux
to use this module, and you might need to upgrade your C library.
.PP
The \f(CWepoll(2)\fR \s-1API\s0 comprises four system calls: \f(CWepoll_create(2)\fR,
\&\f(CWepoll_ctl(2)\fR, \f(CWepoll_wait(2)\fR and \f(CWepoll_pwait(2)\fR.  \f(CW\*(C`IO::Epoll\*(C'\fR
provides a low-level \s-1API\s0 which closely matches the underlying system calls.
It also provides a higher-level layer designed to emulate the behavior of
\&\f(CW\*(C`IO::Poll\*(C'\fR and \f(CW\*(C`IO::Ppoll\*(C'\fR.
.SH "LOW-LEVEL API"
.IX Header "LOW-LEVEL API"
.SS "epoll_create"
.IX Subsection "epoll_create"
Create a new \f(CW\*(C`epoll\*(C'\fR file descriptor by requesting the kernel
allocate an event backing store dimensioned for \f(CW\*(C`size\*(C'\fR descriptors.
The size is not the maximum size of the backing store but just a hint
to the kernel about how to dimension internal structures.  The
returned file descriptor will be used for all the subsequent calls
to the \f(CW\*(C`epoll\*(C'\fR interface.  The file descriptor returned by
\&\f(CW\*(C`epoll_create\*(C'\fR must be closed by using \f(CW\*(C`POSIX::close\*(C'\fR.
.PP
.Vb 3
\&    $epfd = epoll_create(15);
\&    ...
\&    POSIX::close($epfd);
.Ve
.PP
When successful, \f(CW\*(C`epoll_create\*(C'\fR returns a positive integer
identifying the descriptor.  When an error occurs, \f(CW\*(C`epoll_create\*(C'\fR
returns \-1 and errno is set appropriately.
.SS "epoll_ctl"
.IX Subsection "epoll_ctl"
Control an \f(CW\*(C`epoll\*(C'\fR descriptor, \f(CW$epfd\fR, by requesting the operation op be
performed on the target file descriptor, fd.
.PP
.Vb 1
\&  $ret = epoll_ctl($epfd, $op, $fd, $eventmask)
.Ve
.PP
\&\f(CW$epfd\fR is an \f(CW\*(C`epoll\*(C'\fR descriptor returned from \f(CW\*(C`epoll_create\*(C'\fR.
.PP
\&\f(CW$op\fR is one of \f(CW\*(C`EPOLL_CTL_ADD\*(C'\fR, \f(CW\*(C`EPOLL_CTL_MOD\*(C'\fR or \f(CW\*(C`EPOLL_CTL_DEL\*(C'\fR.
.PP
\&\f(CW$fd\fR is the file desciptor to be watched.
.PP
\&\f(CW$eventmask\fR is a bitmask of events defined by \f(CW\*(C`EPOLLIN\*(C'\fR, \f(CW\*(C`EPOLLOUT\*(C'\fR, etc.
.PP
When successful, \f(CW\*(C`epoll_ctl\*(C'\fR returns 0.  When an error occurs,
\&\f(CW\*(C`epoll_ctl\*(C'\fR returns \-1 and errno is set appropriately.
.SS "epoll_wait"
.IX Subsection "epoll_wait"
Wait for events on the \f(CW\*(C`epoll\*(C'\fR file descriptor \f(CW$epfd\fR.
.PP
.Vb 1
\&  $ret = epoll_wait($epfd, $maxevents, $timeout)
.Ve
.PP
\&\f(CW$epfd\fR is an \f(CW\*(C`epoll\*(C'\fR descriptor returned from \f(CW\*(C`epoll_create\*(C'\fR.
.PP
\&\f(CW$maxevents\fR is an integer specifying the maximum number of events to
be returned.
.PP
\&\f(CW$timeout\fR is a timeout, in milliseconds
.PP
When successful, \f(CW\*(C`epoll_wait\*(C'\fR returns a reference to an array of
events.  Each event is a two element array, the first element being
the file descriptor which triggered the event, and the second is the
mask of event types triggered.  For example, if \f(CW\*(C`epoll_wait\*(C'\fR returned the
following data structure:
.PP
.Vb 4
\&    [
\&      [ 0, EPOLLIN ],
\&      [ 6, EPOLLOUT | EPOLLIN ]
\&    ]
.Ve
.PP
then file descriptor 0 would be ready for reading, and fd 4 would be
ready for both reading and writing.
.PP
On error, \f(CW\*(C`epoll_wait\*(C'\fR returns undef and sets \f(CW\*(C`errno\*(C'\fR appropriately.
.SS "epoll_pwait"
.IX Subsection "epoll_pwait"
Wait for events on the \f(CW\*(C`epoll\*(C'\fR file descriptor \f(CW$epfd\fR.
.PP
.Vb 1
\&  $ret = epoll_pwait($epfd, $maxevents, $timeout, $sigmask)
.Ve
.PP
Identical to \f(CW\*(C`epoll_wait\*(C'\fR, except that the kernel will atomically swap the
current signal mask for the process to that supplied in \f(CW$sigmask\fR, wait for
events, then restore it to what it was originally. The \f(CW$sigmask\fR parameter
should be undef, or an instance of \f(CW\*(C`POSIX::SigSet\*(C'\fR.
.SH "HIGH LEVEL API"
.IX Header "HIGH LEVEL API"
IO::Epoll provides an object oriented \s-1API\s0 designed to be a drop-in
replacement for IO::Poll.  See the documentation for that module for
more information.
.SH "METHODS"
.IX Header "METHODS"
.IP "mask ( \s-1IO\s0 [, \s-1EVENT_MASK \s0] )" 4
.IX Item "mask ( IO [, EVENT_MASK ] )"
If \s-1EVENT_MASK\s0 is given, then, if \s-1EVENT_MASK\s0 is non-zero, \s-1IO\s0 is added to the
list of file descriptors and the next call to poll will check for
any event specified in \s-1EVENT_MASK.\s0 If \s-1EVENT_MASK\s0 is zero then \s-1IO\s0 will be
removed from the list of file descriptors.
.Sp
If \s-1EVENT_MASK\s0 is not given then the return value will be the current
event mask value for \s-1IO.\s0
.IP "poll ( [ \s-1TIMEOUT \s0] )" 4
.IX Item "poll ( [ TIMEOUT ] )"
Call the system level poll routine. If \s-1TIMEOUT\s0 is not specified then the
call will block. Returns the number of handles which had events
happen, or \-1 on error. \s-1TIMEOUT\s0 is in seconds and may be fractional.
.IP "events ( \s-1IO \s0)" 4
.IX Item "events ( IO )"
Returns the event mask which represents the events that happend on \s-1IO\s0
during the last call to \f(CW\*(C`poll\*(C'\fR.
.IP "remove ( \s-1IO \s0)" 4
.IX Item "remove ( IO )"
Remove \s-1IO\s0 from the list of file descriptors for the next poll.
.IP "handles( [ \s-1EVENT_MASK \s0] )" 4
.IX Item "handles( [ EVENT_MASK ] )"
Returns a list of handles. If \s-1EVENT_MASK\s0 is not given then a list of all
handles known will be returned. If \s-1EVENT_MASK\s0 is given then a list
of handles will be returned which had one of the events specified by
\&\s-1EVENT_MASK\s0 happen during the last call ti \f(CW\*(C`poll\*(C'\fR
.SH "IO::Ppoll METHODS"
.IX Header "IO::Ppoll METHODS"
IO::Epoll also provides methods compatible with IO::Ppoll. When any of these
methods are called, the IO::Epoll object switches up to IO::Ppoll\-compatible
mode, and will use the \f(CWepoll_pwait(2)\fR system call when the \f(CW\*(C`poll\*(C'\fR method
is invoked.
.IP "sigmask" 4
.IX Item "sigmask"
Returns the \f(CW\*(C`POSIX::SigSet\*(C'\fR object in which the signal mask is stored. Since
this is a reference to the object used in the call to \f(CWepoll_pwait(2)\fR, any
modifications made to it will be reflected in the signal mask given to the
system call.
.IP "sigmask_add ( \s-1SIGNALS \s0)" 4
.IX Item "sigmask_add ( SIGNALS )"
Adds the given signals to the signal mask. These signals will be blocked
during the \f(CW\*(C`poll\*(C'\fR call.
.IP "sigmask_del ( \s-1SIGNALS \s0)" 4
.IX Item "sigmask_del ( SIGNALS )"
Removes the given signals from the signal mask. These signals will not be
blocked during the \f(CW\*(C`poll\*(C'\fR call, and may be delivered while \f(CW\*(C`poll\*(C'\fR is
waiting.
.IP "sigmask_ismember ( \s-1SIGNAL \s0)" 4
.IX Item "sigmask_ismember ( SIGNAL )"
Tests if the given signal is present in the signal mask.
.SH "Exportable constants"
.IX Header "Exportable constants"
Exported by default:
.PP
.Vb 10
\&  EPOLLERR
\&  EPOLLET
\&  EPOLLHUP
\&  EPOLLIN
\&  EPOLLMSG
\&  EPOLLOUT
\&  EPOLLPRI
\&  EPOLLRDBAND
\&  EPOLLRDNORM
\&  EPOLLWRBAND
\&  EPOLLWRNORM
\&  EPOLL_CTL_ADD
\&  EPOLL_CTL_DEL
\&  EPOLL_CTL_MOD
.Ve
.PP
Exported by the :compat tag:
.PP
.Vb 10
\&  POLLNVAL
\&  POLLIN
\&  POLLOUT
\&  POLLERR
\&  POLLHUP
\&  POLLPRI
\&  POLLRDNORM
\&  POLLWRNORM
\&  POLLRDBAND
\&  POLLWRBAND
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\f(CW\*(C`IO::Poll\*(C'\fR \f(CW\*(C`IO::Select\*(C'\fR \f(CW\*(C`IO::Ppoll\*(C'\fR \f(CWepoll(4)\fR \f(CWepoll_create(2)\fR
\&\f(CWepoll_ctl(2)\fR \f(CWepoll_wait(2)\fR \f(CWepoll_pwait(2)\fR
.SH "AUTHOR"
.IX Header "AUTHOR"
Bruce J Keeler, <bruce@gridpoint.com>
.SH "CREDITS"
.IX Header "CREDITS"
The \f(CW\*(C`IO::Poll\*(C'\fR compatibility code borrows heavily from the \f(CW\*(C`IO::Poll\*(C'\fR
code itself, which was written by Graham Barr.
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright (C) 2004 by Bruce J. Keeler
Portions Copyright (C) 1997\-8 Graham Barr <gbarr@pobox.com>
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.