1IO::Event(3) User Contributed Perl Documentation IO::Event(3)
2
6 IO::Event - Tied Filehandles for Nonblocking IO with Object Callbacks
7
9 use IO::Event;
10 use IO::Event 'emulate_Event';
11 use IO::Event 'AnyEvent';
12 my $ioe = IO::Event->new($filehandle);
14 my $ioe = IO::Event::Socket::INET->new( [ARGS] )
16 my $ioe = IO::Event::Socket::UNIX->new( [ARGS] )
18 my $timer = IO::Event->timer(
20 [after => $seconds],
21 interval => $seconds,
22 cb => CODE);
23 my $idler = IO::Event->idle(
25 [min => $seconds],
26 [max => $seconds],
27 [reentrant => 0],
28 cb => CODE);
29 IO::Event::loop();
31 IO::Event::unloop_all();
33
35 IO::Event provides a object-based callback system for handling
36 nonblocking IO. The design goal is to provide a system that just does
37 the right thing w/o the user needing to think about it much.
38 All APIs are kept as simple as possible yet at the same time, all
40 functionality is accesible if needed. Simple things are easy. Hard
41 things are possible.
42 Most of the time file handling syntax will work fine: "<$filehandle>"
44 and "print $filehandle 'stuff'".
45 IO::Event provides automatic buffering of output (with a callback to
47 throttle). It provides automatic line-at-a-time input.
48 After initial setup, call "IO::Event::loop()".
50 IO::Event was originally written to use Event. IO::Event still
52 defaults to using Event but it can now use AnyEvent or its own event
53 loop.
54
56 Until you create your first IO::Event object, you can choose which
57 underlying event handler to use. The default is Event. To choose an
58 event handler, use one of the following lines, import
59 "no_emulate_Event", "emulate_Event", or "AnyEvent".
60 use IO::Event 'no_emulate_Event'
62 use IO::Event 'emulate_Event'
63 use IO::Event 'AnyEvent'
64 The "no_emulate_Event" option means: use Event. The "emulate_Event"
66 option means IO::Event should use its own event loop.
67 Why?
69 You should use AnyEvent if you want to have compatibility with other
71 event loops. You should use "emulate_Event" if you don't need
72 compatibility with other event loops and you have missing-event bugs
73 when using Event. You should use Event if it works for you.
74 The APIs are a bit different depending on which event loop you're
76 using.
77 Event
79 To use Event's event loop:
80 use IO::Event 'no_emulate_Event';
82 or just:
84 use IO::Event
86 IO::Event's definition for "loop()", "timer()", "idle()" and
88 "unloop_all()" all default to the Event version unless "emulate_Event"
89 or "AnyEvent" have been imported. This allows you to easily switch
90 back and forth between Event's API and the others.
91 AnyEvent
93 To use AnyEvent's select loop, import "AnyEvent".
94 use IO::Event 'AnyEvent';
96 You can use AnyEvent's API directly or you can use IO::Event's emulated
98 APIs: "IO::Event::loop()", "IO::Event::unloop()", "IO::Event::timer()",
99 and "IO::Event::idle()". These behave like Event's routines of the
100 same name but use AnyEvent underneath.
101 During testing, using the pure-perl event loop of AnyEvent::Impl::Perl
103 from AnyEvent version 5.271, some read events were dropped. To work
104 around this, a synthetic read-ready event is dispatched for all
105 connected read filehandles every two seconds. Turn this off or adjust
106 its frequency by changing $IO::Event::AnyEvent::lost_event_hack. A
107 numeric value is the time (in seconds) between dispatching read events.
108 A false value turns off this performance-sapping hack.
109 AnyEvent only provides basic support for idle() events: it promises to
111 invoke them "every now and then".
112 "emulate_Event"
114 To use IO::Event's own select loop, import "emulate_Event".
115 use IO::Event 'emulate_Event';
117 IO::Event does not provide a complete emulation of everything that
119 Event does. It provides the full timer API:
120 my $timer = IO::Event::timer( [ARGS] )
122 instead of
124 my $timer = Event::timer( [ARGS] )
126 However it does not provide timer events on filehandles, nor does it
128 provide events for signals, or variable accesses.
129 Use "IO::Event::loop()" instead of "Event::loop()". Use
131 "IO::Event::unloop_all()" instead of "Event::unloop_all()". Use
132 "IO::Event::idle()" instead of "Event::idle()". It does not provide
133 any other methods or functions from Event. If you need them, please
134 send a patch.
135
137 IO::Event->new($filehandle, [ $handler, [ $options ]])
138 The basic "new" constructor takes a filehandle and returns a
139 psuedo-filehandle. Treat the IO::Event object as a filehandle. Do
140 not use the original filehandle without good reason (let us know if
141 you find a good reason so we can fix the problem).
142 The handler is the class or object where you provide callback
144 functions to handle IO events. It defaults to the package of the
145 calling context.
146 If present, $options is a hash reference with the following
148 possible keys:
149 description A text description of this filehandle. Used for
151 debugging and error messages.
152 read_only Set to true if this is a read-only filehandle. Do not
154 accept output.
155 write_only Set to true if this is a write-only filehandle. Do
157 not attept to read.
158 autoread Set to 0 if this should not be an auto-read
160 filehandle.
161 IO::Event::Socket::INET->new( [ARGS] )
163 This constructor uses IO::Socket::INET->new() to create a socket
164 using the ARGS provided. It returns an IO::Event object.
165 The handler defaults as above or can be set with an additional
167 pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A
168 description for the socket can be provided with an additional
169 psuedo-parameter: "Description".
170 IO::Event::Socket::UNIX->new( [ARGS] )
172 This constructor uses IO::Socket::UNIX->new() to create a socket
173 using the ARGS provided. It returns an IO::Event object.
174 The handler defaults as above or can be set with an additional
176 pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A
177 description for the socket can be provided with an additional
178 psuedo-parameter: "Description".
179
181 These handler methods must be available in the handler object/class if
182 the situation in which they would be called arises.
183 ie_input($handler, $ioe, $input_buffer_reference)
185 Invoked when there is fresh data in the input buffer. The input
186 can be retrieved via directly reading it from
187 $$input_buffer_reference or via "read()" from the $ioe filehandle,
188 or by using a variety of standard methods for getting data:
189 <$ioe> like IO::Handle
191 $ioe->get() like Data::LineBuffer
192 $ioe->read() like IO::Handle
193 $ioe->sysread() like IO::Handle
194 $ioe->getline() like IO::Handle
195 $ioe->getlines() like IO::Handle
196 $ioe->getsome() see below
197 $ioe->ungets() like FileHandle::Unget
198 At end-of-file, ie_input will only be invoked once. There may or
200 may not be data in the input buffer.
201 ie_connection($handler, $ioe)
203 Invoked when a listen()ing socket is ready to accept(). It should
204 call accept:
205 sub ie_connection
207 {
208 my ($pkg, $ioe) = @_;
209 my $newfh = $ioe->accept()
210 }
211 ie_read_ready($handler, $ioe, $underlying_file_handle)
213 If autoreading is turned off then this will be invoked.
214 ie_werror($handler, $ioe, $output_buffer_reference)
216 A write error has occured when trying to drain the write buffer.
217 Provide an empty subroutine if you don't care.
218
220 These handler methods will be called if they are defined but it is not
221 required that they be defined.
222 ie_eof($handler, $ioe, $input_buffer_reference)
224 This is invoked when the read-side of the filehandle has been
225 closed by its source.
226 ie_output
228 This is invoked when data has just been written to the underlying
229 filehandle.
230 ie_outputdone
232 This is invoked when all pending data has just been written to the
233 underlying filehandle.
234 ie_connected
236 This is invoked when a "connect()" completes.
237 ie_connect_failed($handler, $ioe, $error_code)
239 This is invoked when a "connect()" fails. For a timeout, the error
240 code will be ETIMEOUT.
241 ie_died($handler, $ioe, $method, $@)
243 If another handler calls "die" then ie_died will be called with the
244 IO::Event object, the name of the method just invoked, and the die
245 string. If no ie_died() callback exists then execution will
246 terminate.
247 ie_timer
249 This is invoked for timer events.
250 ie_exception
252 Invoked when an exceptional condition arises on the underlying
253 filehandle
254 ie_outputoverflow($handler, $ioe, $overflowing,
256 $output_buffer_reference)
257 Invoked when there is too much output data and the output buffers
258 are overflowing. You can take some action to generate less output.
259 This will be invoked exactly once (with $overflowing == 1) when
260 there is too much data in the buffer and then exactly once again
261 (with $overflowing == 0) when there is no longer too much data in
262 the buffer.
263
265 In addition to methods described in detail below, the following methods
266 behave like their "IO" (mostly "IO::Socket") counterparts (except for
267 being mostly non-blocking...):
268 connect
270 listen
271 open
272 read
273 sysread
274 syswrite
275 print
276 eof
277 shutdown
278 Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are
280 passed to underlying "Event" objects:
281 loop
283 unloop
284 and many more...
285 Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are
287 passed to underlying "IO" objects:
288 fileno
290 stat
291 truncate
292 error
293 opened
294 untaint
295 and many more...
296 IO::Event defines its own methods too:
298 ->accept($handler, %options)
300 accept() is nearly identical to the normal IO::Socket::accept()
301 method except that instead of optionally passing a class specifier
302 for the new socket, you optionally pass a handler object or class.
303 The returned filehandle is an IO::Event object.
304 Supported options:
306 description
308 Sets the description for the new socket
309 autoread
311 Set to 0 if you do not want auto-read
312 ->can_read($amount)
314 Returns true if $amount bytes worth of input is available for
315 reading. Note: this does not return true at EOF so be careful not
316 to hang forever at EOF.
317 ->getsome($amount)
319 Returns $amount bytes worth of input or undef if the request can't
320 be filled. Returns what it can at EOF.
321 ->get()
323 get() is like getline() except that it pre-chomp()s the results and
324 assumes the input_record_separator is "\n". This is like get()
325 from Data::LineBuffer.
326 ->unget()
328 Push chomp()ed lines back into the input buffer. This is like
329 unget() from Data::LineBuffer.
330 ->ungetline(), ->xungetc(), ->ungets()
332 This is what ungetc() should be: it pushes a string back into the
333 input buffer. This is unlike IO::Handle->ungetc which takes an
334 ordinal and pushes one character back into the the input buffer.
335 This is like FileHandle::Unget.
336 ->handler($new_handler)
338 Sets the handler object/class if $new_handler is provided. Returns
339 the old handler.
340 ->filehandle()
342 Returns the underlying "IO::Handle".
343 ->event()
345 Returns the underling "Event".
346 ->listener($listening)
348 Used to note that a filehandle is being used to listen for
349 connections (instead of receiving data). A passed parameter of 0
350 does the opposite. Returns the old value. This is mostly used
351 internally in IO::Event.
352 ->input_record_separator($new_sep)
354 IO::Handle doesn't allow input_record_separator's on a per
355 filehandle basis. IO::Event does. If you don't ever set a
356 filehandle's input record separator, then it contineously defaults
357 to the current value of $/. If you set it, then it will use your
358 value and never look at $/ again.
359 ->readevents($readevents)
361 Get/set listening for read-ready events on the underlying
362 filehandle. This could be used by ie_outputoverflow to control
363 input flows.
364 ->output_bufsize($output_bufsize)
366 Get/set the size of the output buffer.
367 ->autoread($autoread)
369 Get/set automatic reading if data when data can be read. Without
370 autoread turned on, the input buffer ins't filled and none of the
371 read methods will work. The point of this is for working with non-
372 data filehandles. This is an experts-only method that kinda
373 defeats the purpose of this module. This would be necessary using
374 recv() to get data.
375 ->drain()
377 Used to start looking for write-ready events on the underlying
378 filehandle. In normal operation this is handled automatically.
379 Deprecated: use writeevents(1) instead.
380 ->reentrant($reentrant)
382 Get/set reentrant callbacks. By default, IO::Event avoids making
383 reentrant callbacks. This is good because your code is less likely
384 to break. This is bad because you won't learn about things right
385 away. For example, you will not learn the the output buffer is
386 overflowing during print(). You'll have to wait for the output
387 buffer to begin draining to find out. This could be a problem.
388 ->close()
390 If there is output buffered, close will be delayed until the output
391 buffer drains.
392 ->forceclose
394 Close close immediately, even if there is output buffered.
395 ->ie_desc([new description])
397 Returns (and sets) the text description of the filehandle. For
398 debugging.
399
401 The following timer construction arguments are supported by IO::Event's
402 emulated event loop and IO::Event's API on top of AnyEvent:
403 cb A callback to invoke when the timer goes off. The callback can
405 either be a CODE reference or an array reference. If it's an array
406 reference, the array should be a two element tuple: the first
407 element is an object and the second object is a method to invoke on
408 the object. The only argument to the method call a reference to
409 the timer object:
410 my ($object, $method) = @{$timer->{cb}}
412 $object->$method($timer)
413 at A time at which to invoke the callback.
415 interval
417 An interval, in seconds between repeat invocations of the callback.
418 after
420 The interval until the first invocation of the callback. After
421 that, invoke every interval.
422 The following methods (from Event) are supported on timer objects:
424 start(), again(), now(), stop(), cancel(), is_cancelled(),
425 is_running(), is_suspended(), pending.
426
428 The following idle construction arguments are supported by IO::Event's
429 emulated event loop and IO::Event's API on top of AnyEvent:
430 cb A callback to invoke when the event loop is idle. The callback can
432 either be a CODE reference or an array reference. If it's an array
433 reference, the array should be a two element tuple: the first
434 element is an object and the second object is a method to invoke on
435 the object.
436 my ($object, $method) = @{$timer->{cb}}
438 $object->$method();
439 min The minimum time between invocations of the callback.
441 max The maximum time between invocations of the callback.
443 The following methods (from Event) are supported on idle objects:
445 start(), again(), now(), stop(), cancel(), is_cancelled(),
446 is_running(), is_suspended(), pending.
447
449 Any method invocations that fail because the method isn't defined in
450 IO::Event will by tried twice more: once using trying for a method on
451 the inner (hidden) filehandle and once more trying for a method on the
452 Event object that's used to create the select loop for this module.
453 This dispatch is now deprecated with the choice of event handlers.
455
457 # This is a tcp line echo server
458 my $listener = IO::Event::Socket::INET->new(
460 Listen => 10,
461 Proto => 'tcp',
462 LocalPort => 2821,
463 );
464 Event::loop();
466 sub ie_connection
468 {
469 my ($pkg, $lstnr) = @_;
470 my $client = $lstnr->accept();
471 printf "accepted connection from %s:%s\n",
472 $client->peerhost, $client->peerport;
473 }
474 sub ie_input
476 {
477 my ($pkg, $client, $ibufref) = @_;
478 print $client <$client>;
479 }
480
482 sysread() is incompatible with eof() because eof() uses getc(). Most
483 of the time this isn't a problem. In other words, some of the time
484 this is a problem: lines go missing.
485 For this reason, IO::Event never uses sysread(). In fact, if you ask
487 it to do a sysread() it does a read() for you instead.
488 On the other hand, at the current time no problems with syswrite have
490 come to light and IO::Event uses syswrite and never any other form of
491 write/print etc.
492
494 IO::Event keeps copies of all of its registered filehandles. If you
495 want to close a filehandle, you'll need to actually call close on it.
496
498 The filehandle object itself is a funny kind of hash reference. If you
499 want to use it to store your own data, you can. Please don't use hash
500 keys that begin "ie_" or "io_" as those are the prefixes used by
501 "IO::Event" and "IO::Socket".
502 The syntax is kinda funny:
504 ${*$filehandle}{'your_hash_key'}
506
508 For a different API on top of IO::Event, see IO::Event::Callback. It
509 uses IO::Event but provides a simpler and perhaps easier-to-use API.
510 The following perl modules do something that is kinda similar to what
512 is being done here:
513 AnyEvent::Handle, AnyEvent::AIO, IO::AIO, IO::Multiplex,
515 IO::NonBlocking, IO::Select Event, POE, POE::Component::Server::TCP,
516 Net::Socket::NonBlock, Net::Server::Multiplex, NetServer::Generic
517 The API borrows most heavily from IO::Multiplex. IO::Event uses
519 Event.pm and thus can be used in programs that are already using Event
520 or POE.
521 Since the original writing of IO::Event, AnyEvent has been released and
523 now AnyEvent::AIO and <AnyEvent:Handle> should be considered the only
524 good alternatives to IO::Event.
525 For an example program using IO::Event, see IO::Event::rinetd which
527 used to be included in this package.
528
530 The test suite only covers 40% of the code. The module is used by its
531 author and seems solid.
532
534 Copyright (C) 2002-2009 David Muir Sharnoff <muir@idiom.org>.
535 Copyright (C) 2011-2013 Google, Inc. This module may be
536 used/copied/etc on the same terms as Perl itself.
537 This module is packaged for Fedora by Emmanuel Seyman
539 <emmanuel@seyman.fr>
540
542 Hey! The above document had some coding errors, which are explained
543 below:
544 Around line 476:
546 '=item' outside of any '=over'
547perl v5.34.0 2021-07-22 IO::Event(3)