NAME
IO::Event - Tied Filehandles for Nonblocking IO with Object Callbacks
SYNOPSIS
use IO::Event;
use IO::Event 'emulate_Event';
use IO::Event 'AnyEvent';
my $ioe = IO::Event->new($filehandle);
my $ioe = IO::Event::Socket::INET->new( [ARGS] )
my $ioe = IO::Event::Socket::UNIX->new( [ARGS] )
my $timer = IO::Event->timer(
[after => $seconds],
interval => $seconds,
cb => CODE);
my $idler = IO::Event->idle(
[min => $seconds],
[max => $seconds],
[reentrant => 0],
cb => CODE);
IO::Event::loop();
IO::Event::unloop_all();
DESCRIPTION
IO::Event provides a object-based callback system for handling
nonblocking IO. The design goal is to provide a system that just does
the right thing w/o the user needing to think about it much.
All APIs are kept as simple as possible yet at the same time, all
functionality is accesible if needed. Simple things are easy. Hard
things are possible.
Most of the time file handling syntax will work fine: "<$filehandle>"
and "print $filehandle 'stuff'".
IO::Event provides automatic buffering of output (with a callback to
throttle). It provides automatic line-at-a-time input.
After initial setup, call "IO::Event::loop()".
IO::Event was originally written to use Event. IO::Event still defaults
to using Event but it can now use AnyEvent or its own event loop.
CHOOSING AN EVENT HANDLER
Until you create your first IO::Event object, you can choose which
underlying event handler to use. The default is Event. To choose an
event handler, use one of the following lines, import
"no_emulate_Event", "emulate_Event", or "AnyEvent".
use IO::Event 'no_emulate_Event'
use IO::Event 'emulate_Event'
use IO::Event 'AnyEvent'
The "no_emulate_Event" option means: use Event. The "emulate_Event"
option means IO::Event should use its own event loop.
Why?
You should use AnyEvent if you want to have compatibility with other
event loops. You should use "emulate_Event" if you don't need
compatibility with other event loops and you have missing-event bugs
when using Event. You should use Event if it works for you.
The APIs are a bit different depending on which event loop you're using.
Event
To use Event's event loop:
use IO::Event 'no_emulate_Event';
or just:
use IO::Event
IO::Event's definition for "loop()", "timer()", "idle()" and
"unloop_all()" all default to the Event version unless "emulate_Event"
or "AnyEvent" have been imported. This allows you to easily switch back
and forth between Event's API and the others.
AnyEvent
To use AnyEvent's select loop, import "AnyEvent".
use IO::Event 'AnyEvent';
You can use AnyEvent's API directly or you can use IO::Event's emulated
APIs: "IO::Event::loop()", "IO::Event::unloop()", "IO::Event::timer()",
and "IO::Event::idle()". These behave like Event's routines of the same
name but use AnyEvent underneath.
During testing, using the pure-perl event loop of AnyEvent::Impl::Perl
from AnyEvent version 5.271, some read events were dropped. To work
around this, a synthetic read-ready event is dispatched for all
connected read filehandles every two seconds. Turn this off or adjust
its frequency by changing $IO::Event::AnyEvent::lost_event_hack. A
numeric value is the time (in seconds) between dispatching read events.
A false value turns off this performance-sapping hack.
AnyEvent only provides basic support for idle() events: it promises to
invoke them "every now and then".
"emulate_Event"
To use IO::Event's own select loop, import "emulate_Event".
use IO::Event 'emulate_Event';
IO::Event does not provide a complete emulation of everything that Event
does. It provides the full timer API:
my $timer = IO::Event::timer( [ARGS] )
instead of
my $timer = Event::timer( [ARGS] )
However it does not provide timer events on filehandles, nor does it
provide events for signals, or variable accesses.
Use "IO::Event::loop()" instead of "Event::loop()". Use
"IO::Event::unloop_all()" instead of "Event::unloop_all()". Use
"IO::Event::idle()" instead of "Event::idle()". It does not provide any
other methods or functions from Event. If you need them, please send a
patch.
CONSTRUCTORS
IO::Event->new($filehandle, [ $handler, [ $options ]])
The basic "new" constructor takes a filehandle and returns a
psuedo-filehandle. Treat the IO::Event object as a filehandle. Do
not use the original filehandle without good reason (let us know if
you find a good reason so we can fix the problem).
The handler is the class or object where you provide callback
functions to handle IO events. It defaults to the package of the
calling context.
If present, $options is a hash reference with the following possible
keys:
description A text description of this filehandle. Used for
debugging and error messages.
read_only Set to true if this is a read-only filehandle. Do not
accept output.
write_only Set to true if this is a write-only filehandle. Do not
attept to read.
autoread Set to 0 if this should not be an auto-read filehandle.
IO::Event::Socket::INET->new( [ARGS] )
This constructor uses IO::Socket::INET->new() to create a socket
using the ARGS provided. It returns an IO::Event object.
The handler defaults as above or can be set with an additional
pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A
description for the socket can be provided with an additional
psuedo-parameter: "Description".
IO::Event::Socket::UNIX->new( [ARGS] )
This constructor uses IO::Socket::UNIX->new() to create a socket
using the ARGS provided. It returns an IO::Event object.
The handler defaults as above or can be set with an additional
pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A
description for the socket can be provided with an additional
psuedo-parameter: "Description".
MANDATORY HANDLERS
These handler methods must be available in the handler object/class if
the situation in which they would be called arises.
ie_input($handler, $ioe, $input_buffer_reference)
Invoked when there is fresh data in the input buffer. The input can
be retreived via directly reading it from $$input_buffer_reference
or via "read()" from the $ioe filehandle, or by using a variety of
standard methods for getting data:
<$ioe> like IO::Handle
$ioe->get() like Data::LineBuffer
$ioe->read() like IO::Handle
$ioe->sysread() like IO::Handle
$ioe->getline() like IO::Handle
$ioe->getlines() like IO::Handle
$ioe->getsome() see below
$ioe->ungets() like FileHandle::Unget
At end-of-file, ie_input will only be invoked once. There may or may
not be data in the input buffer.
ie_connection($handler, $ioe)
Invoked when a listen()ing socket is ready to accept(). It should
call accept:
sub ie_connection
{
my ($pkg, $ioe) = @_;
my $newfh = $ioe->accept()
}
ie_read_ready($handler, $ioe, $underlying_file_handle)
If autoreading is turned off then this will be invoked.
ie_werror($handler, $ioe, $output_buffer_reference)
A write error has occured when trying to drain the write buffer.
Provide an empty subroutine if you don't care.
OPTIONAL HANDLERS
These handler methods will be called if they are defined but it is not
required that they be defined.
ie_eof($handler, $ioe, $input_buffer_reference)
This is invoked when the read-side of the filehandle has been closed
by its source.
ie_output
This is invoked when data has just been written to the underlying
filehandle.
ie_outputdone
This is invoked when all pending data has just been written to the
underlying filehandle.
ie_connected
This is invoked when a "connect()" completes.
ie_connect_failed($handler, $ioe, $error_code)
This is invoked when a "connect()" fails. For a timeout, the error
code will be ETIMEOUT.
ie_died($handler, $ioe, $method, $@)
If another handler calls "die" then ie_died will be called with the
IO::Event object, the name of the method just invoked, and the die
string. If no ie_died() callback exists then execution will
terminate.
ie_timer
This is invoked for timer events.
ie_exception
Invoked when an exceptional condition arises on the underlying
filehandle
ie_outputoverflow($handler, $ioe, $overflowing,
$output_buffer_reference)
Invoked when there is too much output data and the output buffers
are overflowing. You can take some action to generate less output.
This will be invoked exactly once (with $overflowing == 1) when
there is too much data in the buffer and then exactly once again
(with $overflowing == 0) when there is no longer too much data in
the buffer.
METHODS
In addition to methods described in detail below, the following methods
behave like their "IO" (mostly "IO::Socket") counterparts (except for
being mostly non-blocking...):
connect
listen
open
read
sysread
syswrite
print
eof
shutdown
Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are
passed to underlying "Event" objects:
loop
unloop
and many more...
Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are
passed to underlying "IO" objects:
fileno
stat
truncate
error
opened
untaint
and many more...
IO::Event defines its own methods too:
->accept($handler, %options)
accept() is nearly identical to the normal IO::Socket::accept()
method except that instead of optionally passing a class specifier
for the new socket, you optionally pass a handler object or class.
The returned filehandle is an IO::Event object.
Supported options:
description
Sets the description for the new socket
autoread
Set to 0 if you do not want auto-read
->can_read($amount)
Returns true if $amount bytes worth of input is available for
reading. Note: this does not return true at EOF so be careful not to
hang forever at EOF.
->getsome($amount)
Returns $amount bytes worth of input or undef if the request can't
be filled. Returns what it can at EOF.
->get()
get() is like getline() except that it pre-chomp()s the results and
assumes the input_record_separator is "\n". This is like get() from
Data::LineBuffer.
->unget()
Push chomp()ed lines back into the input buffer. This is like
unget() from Data::LineBuffer.
->ungetline(), ->xungetc(), ->ungets()
This is what ungetc() should be: it pushes a string back into the
input buffer. This is unlike IO::Handle->ungetc which takes an
ordinal and pushes one character back into the the input buffer.
This is like FileHandle::Unget.
->handler($new_handler)
Sets the handler object/class if $new_handler is provided. Returns
the old handler.
->filehandle()
Returns the underlying "IO::Handle".
->event()
Returns the underling "Event".
->listener($listening)
Used to note that a filehandle is being used to listen for
connections (instead of receiving data). A passed parameter of 0
does the opposite. Returns the old value. This is mostly used
internally in IO::Event.
->input_record_separator($new_sep)
IO::Handle doesn't allow input_record_separator's on a per
filehandle basis. IO::Event does. If you don't ever set a
filehandle's input record separator, then it contineously defaults
to the current value of $/. If you set it, then it will use your
value and never look at $/ again.
->readevents($readevents)
Get/set listening for read-ready events on the underlying
filehandle. This could be used by ie_outputoverflow to control input
flows.
->output_bufsize($output_bufsize)
Get/set the size of the output buffer.
->autoread($autoread)
Get/set automatic reading if data when data can be read. Without
autoread turned on, the input buffer ins't filled and none of the
read methods will work. The point of this is for working with
non-data filehandles. This is an experts-only method that kinda
defeats the purpose of this module. This would be necessary using
recv() to get data.
->drain()
Used to start looking for write-ready events on the underlying
filehandle. In normal operation this is handled automatically.
Deprecated: use writeevents(1) instead.
->reentrant($reentrant)
Get/set reentrant callbacks. By default, IO::Event avoids making
reentrant callbacks. This is good because your code is less likely
to break. This is bad because you won't learn about things right
away. For example, you will not learn the the output buffer is
overflowing during print(). You'll have to wait for the output
buffer to begin draining to find out. This could be a problem.
->close()
If there is output buffered, close will be delayed until the output
buffer drains.
->forceclose
Close close immediately, even if there is output buffered.
->ie_desc([new description])
Returns (and sets) the text description of the filehandle. For
debugging.
TIMER API
The following timer construction arguments are supported by IO::Event's
emulated event loop and IO::Event's API on top of AnyEvent:
cb A callback to invoke when the timer goes off. The callback can
either be a CODE reference or an array reference. If it's an array
reference, the array should be a two element tuple: the first
element is an object and the second object is a method to invoke on
the object. The only argument to the method call a reference to the
timer object:
my ($object, $method) = @{$timer->{cb}}
$object->$method($timer)
at A time at which to invoke the callback.
interval
An interval, in seconds between repeat invocations of the callback.
after
The interval until the first invocation of the callback. After that,
invoke every *interval*.
The following methods (from Event) are supported on timer objects:
start(), again(), now(), stop(), cancel(), is_cancelled(), is_running(),
is_suspended(), pending.
IDLE API
The following idle construction arguments are supported by IO::Event's
emulated event loop and IO::Event's API on top of AnyEvent:
cb A callback to invoke when the event loop is idle. The callback can
either be a CODE reference or an array reference. If it's an array
reference, the array should be a two element tuple: the first
element is an object and the second object is a method to invoke on
the object.
my ($object, $method) = @{$timer->{cb}}
$object->$method();
min The minimum time between invocations of the callback.
max The maximum time between invocations of the callback.
The following methods (from Event) are supported on idle objects:
start(), again(), now(), stop(), cancel(), is_cancelled(), is_running(),
is_suspended(), pending.
SUBSTITUED METHODS
Any method invocations that fail because the method isn't defined in
IO::Event will by tried twice more: once using trying for a method on
the inner (hidden) filehandle and once more trying for a method on the
Event object that's used to create the select loop for this module.
This dispatch is now deprecated with the choice of event handlers.
EXAMPLE SERVER
# This is a tcp line echo server
my $listener = IO::Event::Socket::INET->new(
Listen => 10,
Proto => 'tcp',
LocalPort => 2821,
);
Event::loop();
sub ie_connection
{
my ($pkg, $lstnr) = @_;
my $client = $lstnr->accept();
printf "accepted connection from %s:%s\n",
$client->peerhost, $client->peerport;
}
sub ie_input
{
my ($pkg, $client, $ibufref) = @_;
print $client <$client>;
}
SYSREAD and EOF
sysread() is incompatable with eof() because eof() uses getc(). Most of
the time this isn't a problem. In other words, some of the time this is
a problem: lines go missing.
For this reason, IO::Event never uses sysread(). In fact, if you ask it
to do a sysread() it does a read() for you instead.
On the other hand, at the current time no problems with syswrite have
come to light and IO::Event uses syswrite and never any other form of
write/print etc.
DESTRUCTION
IO::Event keeps copies of all of its registered filehandles. If you want
to close a filehandle, you'll need to actually call close on it.
DATA STRUCTURE
The filehandle object itself is a funny kind of hash reference. If you
want to use it to store your own data, you can. Please don't use hash
keys that begin "ie_" or "io_" as those are the prefixes used by
"IO::Event" and "IO::Socket".
The syntax is kinda funny:
${*$filehandle}{'your_hash_key'}
SEE ALSO
For a different API on top of IO::Event, see IO::Event::Callback. It
uses IO::Event but provides a simpler and perhaps easier-to-use API.
The following perl modules do something that is kinda similar to what is
being done here:
AnyEvent::Handle, AnyEvent::AIO, IO::AIO, IO::Multiplex,
IO::NonBlocking, IO::Select Event, POE, POE::Component::Server::TCP,
Net::Socket::NonBlock, Net::Server::Multiplex, NetServer::Generic
The API borrows most heavily from IO::Multiplex. IO::Event uses Event.pm
and thus can be used in programs that are already using Event or POE.
Since the original writing of IO::Event, AnyEvent has been released and
now AnyEvent::AIO and <AnyEvent:Handle> should be considered the only
good alternatives to IO::Event.
For an example program using IO::Event, see IO::Event::rinetd which used
to be included in this package.
BUGS
The test suite only covers 40% of the code. The module is used by its
author and seems solid.
LICENSE
Copyright (C) 2002-2009 David Muir Sharnoff <muir@idiom.org>. Copyright
(C) 2011 Google, Inc. This module may be used/copied/etc on the same
terms as Perl itself.
POD ERRORS
Hey! The above document had some coding errors, which are explained
below:
Around line 476:
'=item' outside of any '=over'