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IO::Epoll.3pm

NAME

IO::Epoll - Scalable IO Multiplexing for Linux 2.5.44 and higher

SYNOPSIS

     # Low level interface
     use IO::Epoll;
 
     $epfd = epoll_create(10);
 
     epoll_ctl($epfd, EPOLL_CTL_ADD, fileno STDIN, EPOLLIN) >= 0
         || die "epoll_ctl: $!\n";
     epoll_ctl($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);
 
 

DESCRIPTION

The epoll(4) subsystem is a new, (currently) Linux-specific variant of poll(2). 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.

The epoll(2) API comprises four system calls: epoll_create(2), epoll_ctl(2), epoll_wait(2) and epoll_pwait(2). "IO::Epoll" provides a low-level API which closely matches the underlying system calls. It also provides a higher-level layer designed to emulate the behavior of "IO::Poll" and "IO::Ppoll".

LOW-LEVEL API

epoll_create

Create a new "epoll" file descriptor by requesting the kernel allocate an event backing store dimensioned for "size" 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 "epoll" interface. The file descriptor returned by "epoll_create" must be closed by using "POSIX::close".

     $epfd = epoll_create(15);
     ...
     POSIX::close($epfd);
 
 

When successful, "epoll_create" returns a positive integer identifying the descriptor. When an error occurs, "epoll_create" returns -1 and errno is set appropriately.

epoll_ctl

Control an "epoll" descriptor, $epfd, by requesting the operation op be performed on the target file descriptor, fd.

   $ret = epoll_ctl($epfd, $op, $fd, $eventmask)
 
 

$epfd is an "epoll" descriptor returned from "epoll_create".

$op is one of "EPOLL_CTL_ADD", "EPOLL_CTL_MOD" or "EPOLL_CTL_DEL".

$fd is the file desciptor to be watched.

$eventmask is a bitmask of events defined by "EPOLLIN", "EPOLLOUT", etc.

When successful, "epoll_ctl" returns 0. When an error occurs, "epoll_ctl" returns -1 and errno is set appropriately.

epoll_wait

Wait for events on the "epoll" file descriptor $epfd.

   $ret = epoll_wait($epfd, $maxevents, $timeout)
 
 

$epfd is an "epoll" descriptor returned from "epoll_create".

$maxevents is an integer specifying the maximum number of events to be returned.

$timeout is a timeout, in milliseconds

When successful, "epoll_wait" 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 "epoll_wait" returned the following data structure:

     [
       [ 0, EPOLLIN ],
       [ 6, EPOLLOUT | EPOLLIN ]
     ]
 
 

then file descriptor 0 would be ready for reading, and fd 4 would be ready for both reading and writing.

On error, "epoll_wait" returns undef and sets "errno" appropriately.

epoll_pwait

Wait for events on the "epoll" file descriptor $epfd.

   $ret = epoll_pwait($epfd, $maxevents, $timeout, $sigmask)
 
 

Identical to "epoll_wait", except that the kernel will atomically swap the current signal mask for the process to that supplied in $sigmask, wait for events, then restore it to what it was originally. The $sigmask parameter should be undef, or an instance of "POSIX::SigSet".

HIGH LEVEL API

IO::Epoll provides an object oriented API designed to be a drop-in replacement for IO::Poll. See the documentation for that module for more information.

METHODS

mask ( IO [, EVENT_MASK ] )

If EVENT_MASK is given, then, if EVENT_MASK is non-zero, IO is added to the list of file descriptors and the next call to poll will check for any event specified in EVENT_MASK. If EVENT_MASK is zero then IO will be removed from the list of file descriptors.

If EVENT_MASK is not given then the return value will be the current event mask value for IO.

poll ( [ TIMEOUT ] )

Call the system level poll routine. If TIMEOUT is not specified then the call will block. Returns the number of handles which had events happen, or -1 on error. TIMEOUT is in seconds and may be fractional.

events ( IO )

Returns the event mask which represents the events that happend on IO during the last call to "poll".

remove ( IO )

Remove IO from the list of file descriptors for the next poll.

handles( [ EVENT_MASK ] )

Returns a list of handles. If EVENT_MASK is not given then a list of all handles known will be returned. If EVENT_MASK is given then a list of handles will be returned which had one of the events specified by EVENT_MASK happen during the last call ti "poll"

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 epoll_pwait(2) system call when the "poll" method is invoked.

sigmask

Returns the "POSIX::SigSet" object in which the signal mask is stored. Since this is a reference to the object used in the call to epoll_pwait(2), any modifications made to it will be reflected in the signal mask given to the system call.

sigmask_add ( SIGNALS )

Adds the given signals to the signal mask. These signals will be blocked during the "poll" call.

sigmask_del ( SIGNALS )

Removes the given signals from the signal mask. These signals will not be blocked during the "poll" call, and may be delivered while "poll" is waiting.

sigmask_ismember ( SIGNAL )

Tests if the given signal is present in the signal mask.

Exportable constants

Exported by default:

   EPOLLERR
   EPOLLET
   EPOLLHUP
   EPOLLIN
   EPOLLMSG
   EPOLLOUT
   EPOLLPRI
   EPOLLRDBAND
   EPOLLRDNORM
   EPOLLWRBAND
   EPOLLWRNORM
   EPOLL_CTL_ADD
   EPOLL_CTL_DEL
   EPOLL_CTL_MOD
 
 

Exported by the :compat tag:

   POLLNVAL
   POLLIN
   POLLOUT
   POLLERR
   POLLHUP
   POLLPRI
   POLLRDNORM
   POLLWRNORM
   POLLRDBAND
   POLLWRBAND
 
 

SEE ALSO

"IO::Poll" "IO::Select" "IO::Ppoll" epoll(4) epoll_create(2) epoll_ctl(2) epoll_wait(2) epoll_pwait(2)

AUTHOR

Bruce J Keeler, <bruce@gridpoint.com>

CREDITS

The "IO::Poll" compatibility code borrows heavily from the "IO::Poll" code itself, which was written by Graham Barr.

COPYRIGHT AND LICENSE

Copyright (C) 2004 by Bruce J. Keeler Portions Copyright (C) 1997-8 Graham Barr <gbarr@pobox.com>

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