1 |
=head1 NAME |
2 |
|
3 |
AnyEvent - provide framework for multiple event loops |
4 |
|
5 |
EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - various supported event loops |
6 |
|
7 |
=head1 SYNOPSIS |
8 |
|
9 |
use AnyEvent; |
10 |
|
11 |
my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
12 |
... |
13 |
}); |
14 |
|
15 |
my $w = AnyEvent->timer (after => $seconds, cb => sub { |
16 |
... |
17 |
}); |
18 |
|
19 |
my $w = AnyEvent->condvar; # stores whether a condition was flagged |
20 |
$w->wait; # enters "main loop" till $condvar gets ->broadcast |
21 |
$w->broadcast; # wake up current and all future wait's |
22 |
|
23 |
=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) |
24 |
|
25 |
Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
26 |
nowadays. So what is different about AnyEvent? |
27 |
|
28 |
Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of |
29 |
policy> and AnyEvent is I<small and efficient>. |
30 |
|
31 |
First and foremost, I<AnyEvent is not an event model> itself, it only |
32 |
interfaces to whatever event model the main program happens to use in a |
33 |
pragmatic way. For event models and certain classes of immortals alike, |
34 |
the statement "there can only be one" is a bitter reality: In general, |
35 |
only one event loop can be active at the same time in a process. AnyEvent |
36 |
helps hiding the differences between those event loops. |
37 |
|
38 |
The goal of AnyEvent is to offer module authors the ability to do event |
39 |
programming (waiting for I/O or timer events) without subscribing to a |
40 |
religion, a way of living, and most importantly: without forcing your |
41 |
module users into the same thing by forcing them to use the same event |
42 |
model you use. |
43 |
|
44 |
For modules like POE or IO::Async (which is a total misnomer as it is |
45 |
actually doing all I/O I<synchronously>...), using them in your module is |
46 |
like joining a cult: After you joined, you are dependent on them and you |
47 |
cannot use anything else, as it is simply incompatible to everything that |
48 |
isn't itself. What's worse, all the potential users of your module are |
49 |
I<also> forced to use the same event loop you use. |
50 |
|
51 |
AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
52 |
fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
53 |
with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if |
54 |
your module uses one of those, every user of your module has to use it, |
55 |
too. But if your module uses AnyEvent, it works transparently with all |
56 |
event models it supports (including stuff like POE and IO::Async, as long |
57 |
as those use one of the supported event loops. It is trivial to add new |
58 |
event loops to AnyEvent, too, so it is future-proof). |
59 |
|
60 |
In addition to being free of having to use I<the one and only true event |
61 |
model>, AnyEvent also is free of bloat and policy: with POE or similar |
62 |
modules, you get an enourmous amount of code and strict rules you have to |
63 |
follow. AnyEvent, on the other hand, is lean and up to the point, by only |
64 |
offering the functionality that is necessary, in as thin as a wrapper as |
65 |
technically possible. |
66 |
|
67 |
Of course, if you want lots of policy (this can arguably be somewhat |
68 |
useful) and you want to force your users to use the one and only event |
69 |
model, you should I<not> use this module. |
70 |
|
71 |
|
72 |
=head1 DESCRIPTION |
73 |
|
74 |
L<AnyEvent> provides an identical interface to multiple event loops. This |
75 |
allows module authors to utilise an event loop without forcing module |
76 |
users to use the same event loop (as only a single event loop can coexist |
77 |
peacefully at any one time). |
78 |
|
79 |
The interface itself is vaguely similar, but not identical to the L<Event> |
80 |
module. |
81 |
|
82 |
During the first call of any watcher-creation method, the module tries |
83 |
to detect the currently loaded event loop by probing whether one of |
84 |
the following modules is already loaded: L<Coro::EV>, L<Coro::Event>, |
85 |
L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one |
86 |
found is used. If none are found, the module tries to load these modules |
87 |
(excluding Event::Lib and Qt) in the order given. The first one that can |
88 |
be successfully loaded will be used. If, after this, still none could be |
89 |
found, AnyEvent will fall back to a pure-perl event loop, which is not |
90 |
very efficient, but should work everywhere. |
91 |
|
92 |
Because AnyEvent first checks for modules that are already loaded, loading |
93 |
an event model explicitly before first using AnyEvent will likely make |
94 |
that model the default. For example: |
95 |
|
96 |
use Tk; |
97 |
use AnyEvent; |
98 |
|
99 |
# .. AnyEvent will likely default to Tk |
100 |
|
101 |
The I<likely> means that, if any module loads another event model and |
102 |
starts using it, all bets are off. Maybe you should tell their authors to |
103 |
use AnyEvent so their modules work together with others seamlessly... |
104 |
|
105 |
The pure-perl implementation of AnyEvent is called |
106 |
C<AnyEvent::Impl::Perl>. Like other event modules you can load it |
107 |
explicitly. |
108 |
|
109 |
=head1 WATCHERS |
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|
111 |
AnyEvent has the central concept of a I<watcher>, which is an object that |
112 |
stores relevant data for each kind of event you are waiting for, such as |
113 |
the callback to call, the filehandle to watch, etc. |
114 |
|
115 |
These watchers are normal Perl objects with normal Perl lifetime. After |
116 |
creating a watcher it will immediately "watch" for events and invoke the |
117 |
callback when the event occurs (of course, only when the event model |
118 |
is in control). |
119 |
|
120 |
To disable the watcher you have to destroy it (e.g. by setting the |
121 |
variable you store it in to C<undef> or otherwise deleting all references |
122 |
to it). |
123 |
|
124 |
All watchers are created by calling a method on the C<AnyEvent> class. |
125 |
|
126 |
Many watchers either are used with "recursion" (repeating timers for |
127 |
example), or need to refer to their watcher object in other ways. |
128 |
|
129 |
An any way to achieve that is this pattern: |
130 |
|
131 |
my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
132 |
# you can use $w here, for example to undef it |
133 |
undef $w; |
134 |
}); |
135 |
|
136 |
Note that C<my $w; $w => combination. This is necessary because in Perl, |
137 |
my variables are only visible after the statement in which they are |
138 |
declared. |
139 |
|
140 |
=head2 IO WATCHERS |
141 |
|
142 |
You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
143 |
with the following mandatory key-value pairs as arguments: |
144 |
|
145 |
C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
146 |
events. C<poll> must be a string that is either C<r> or C<w>, which |
147 |
creates a watcher waiting for "r"eadable or "w"ritable events, |
148 |
respectively. C<cb> is the callback to invoke each time the file handle |
149 |
becomes ready. |
150 |
|
151 |
As long as the I/O watcher exists it will keep the file descriptor or a |
152 |
copy of it alive/open. |
153 |
|
154 |
It is not allowed to close a file handle as long as any watcher is active |
155 |
on the underlying file descriptor. |
156 |
|
157 |
Some event loops issue spurious readyness notifications, so you should |
158 |
always use non-blocking calls when reading/writing from/to your file |
159 |
handles. |
160 |
|
161 |
Example: |
162 |
|
163 |
# wait for readability of STDIN, then read a line and disable the watcher |
164 |
my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
165 |
chomp (my $input = <STDIN>); |
166 |
warn "read: $input\n"; |
167 |
undef $w; |
168 |
}); |
169 |
|
170 |
=head2 TIME WATCHERS |
171 |
|
172 |
You can create a time watcher by calling the C<< AnyEvent->timer >> |
173 |
method with the following mandatory arguments: |
174 |
|
175 |
C<after> specifies after how many seconds (fractional values are |
176 |
supported) should the timer activate. C<cb> the callback to invoke in that |
177 |
case. |
178 |
|
179 |
The timer callback will be invoked at most once: if you want a repeating |
180 |
timer you have to create a new watcher (this is a limitation by both Tk |
181 |
and Glib). |
182 |
|
183 |
Example: |
184 |
|
185 |
# fire an event after 7.7 seconds |
186 |
my $w = AnyEvent->timer (after => 7.7, cb => sub { |
187 |
warn "timeout\n"; |
188 |
}); |
189 |
|
190 |
# to cancel the timer: |
191 |
undef $w; |
192 |
|
193 |
Example 2: |
194 |
|
195 |
# fire an event after 0.5 seconds, then roughly every second |
196 |
my $w; |
197 |
|
198 |
my $cb = sub { |
199 |
# cancel the old timer while creating a new one |
200 |
$w = AnyEvent->timer (after => 1, cb => $cb); |
201 |
}; |
202 |
|
203 |
# start the "loop" by creating the first watcher |
204 |
$w = AnyEvent->timer (after => 0.5, cb => $cb); |
205 |
|
206 |
=head3 TIMING ISSUES |
207 |
|
208 |
There are two ways to handle timers: based on real time (relative, "fire |
209 |
in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
210 |
o'clock"). |
211 |
|
212 |
While most event loops expect timers to specified in a relative way, they |
213 |
use absolute time internally. This makes a difference when your clock |
214 |
"jumps", for example, when ntp decides to set your clock backwards from |
215 |
the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to |
216 |
fire "after" a second might actually take six years to finally fire. |
217 |
|
218 |
AnyEvent cannot compensate for this. The only event loop that is conscious |
219 |
about these issues is L<EV>, which offers both relative (ev_timer, based |
220 |
on true relative time) and absolute (ev_periodic, based on wallclock time) |
221 |
timers. |
222 |
|
223 |
AnyEvent always prefers relative timers, if available, matching the |
224 |
AnyEvent API. |
225 |
|
226 |
=head2 SIGNAL WATCHERS |
227 |
|
228 |
You can watch for signals using a signal watcher, C<signal> is the signal |
229 |
I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
230 |
be invoked whenever a signal occurs. |
231 |
|
232 |
Multiple signal occurances can be clumped together into one callback |
233 |
invocation, and callback invocation will be synchronous. synchronous means |
234 |
that it might take a while until the signal gets handled by the process, |
235 |
but it is guarenteed not to interrupt any other callbacks. |
236 |
|
237 |
The main advantage of using these watchers is that you can share a signal |
238 |
between multiple watchers. |
239 |
|
240 |
This watcher might use C<%SIG>, so programs overwriting those signals |
241 |
directly will likely not work correctly. |
242 |
|
243 |
Example: exit on SIGINT |
244 |
|
245 |
my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
246 |
|
247 |
=head2 CHILD PROCESS WATCHERS |
248 |
|
249 |
You can also watch on a child process exit and catch its exit status. |
250 |
|
251 |
The child process is specified by the C<pid> argument (if set to C<0>, it |
252 |
watches for any child process exit). The watcher will trigger as often |
253 |
as status change for the child are received. This works by installing a |
254 |
signal handler for C<SIGCHLD>. The callback will be called with the pid |
255 |
and exit status (as returned by waitpid). |
256 |
|
257 |
Example: wait for pid 1333 |
258 |
|
259 |
my $w = AnyEvent->child ( |
260 |
pid => 1333, |
261 |
cb => sub { |
262 |
my ($pid, $status) = @_; |
263 |
warn "pid $pid exited with status $status"; |
264 |
}, |
265 |
); |
266 |
|
267 |
=head2 CONDITION VARIABLES |
268 |
|
269 |
Condition variables can be created by calling the C<< AnyEvent->condvar >> |
270 |
method without any arguments. |
271 |
|
272 |
A condition variable waits for a condition - precisely that the C<< |
273 |
->broadcast >> method has been called. |
274 |
|
275 |
They are very useful to signal that a condition has been fulfilled, for |
276 |
example, if you write a module that does asynchronous http requests, |
277 |
then a condition variable would be the ideal candidate to signal the |
278 |
availability of results. |
279 |
|
280 |
You can also use condition variables to block your main program until |
281 |
an event occurs - for example, you could C<< ->wait >> in your main |
282 |
program until the user clicks the Quit button in your app, which would C<< |
283 |
->broadcast >> the "quit" event. |
284 |
|
285 |
Note that condition variables recurse into the event loop - if you have |
286 |
two pirces of code that call C<< ->wait >> in a round-robbin fashion, you |
287 |
lose. Therefore, condition variables are good to export to your caller, but |
288 |
you should avoid making a blocking wait yourself, at least in callbacks, |
289 |
as this asks for trouble. |
290 |
|
291 |
This object has two methods: |
292 |
|
293 |
=over 4 |
294 |
|
295 |
=item $cv->wait |
296 |
|
297 |
Wait (blocking if necessary) until the C<< ->broadcast >> method has been |
298 |
called on c<$cv>, while servicing other watchers normally. |
299 |
|
300 |
You can only wait once on a condition - additional calls will return |
301 |
immediately. |
302 |
|
303 |
Not all event models support a blocking wait - some die in that case |
304 |
(programs might want to do that to stay interactive), so I<if you are |
305 |
using this from a module, never require a blocking wait>, but let the |
306 |
caller decide whether the call will block or not (for example, by coupling |
307 |
condition variables with some kind of request results and supporting |
308 |
callbacks so the caller knows that getting the result will not block, |
309 |
while still suppporting blocking waits if the caller so desires). |
310 |
|
311 |
Another reason I<never> to C<< ->wait >> in a module is that you cannot |
312 |
sensibly have two C<< ->wait >>'s in parallel, as that would require |
313 |
multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
314 |
can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
315 |
L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
316 |
from different coroutines, however). |
317 |
|
318 |
=item $cv->broadcast |
319 |
|
320 |
Flag the condition as ready - a running C<< ->wait >> and all further |
321 |
calls to C<wait> will (eventually) return after this method has been |
322 |
called. If nobody is waiting the broadcast will be remembered.. |
323 |
|
324 |
=back |
325 |
|
326 |
Example: |
327 |
|
328 |
# wait till the result is ready |
329 |
my $result_ready = AnyEvent->condvar; |
330 |
|
331 |
# do something such as adding a timer |
332 |
# or socket watcher the calls $result_ready->broadcast |
333 |
# when the "result" is ready. |
334 |
# in this case, we simply use a timer: |
335 |
my $w = AnyEvent->timer ( |
336 |
after => 1, |
337 |
cb => sub { $result_ready->broadcast }, |
338 |
); |
339 |
|
340 |
# this "blocks" (while handling events) till the watcher |
341 |
# calls broadcast |
342 |
$result_ready->wait; |
343 |
|
344 |
=head1 GLOBAL VARIABLES AND FUNCTIONS |
345 |
|
346 |
=over 4 |
347 |
|
348 |
=item $AnyEvent::MODEL |
349 |
|
350 |
Contains C<undef> until the first watcher is being created. Then it |
351 |
contains the event model that is being used, which is the name of the |
352 |
Perl class implementing the model. This class is usually one of the |
353 |
C<AnyEvent::Impl:xxx> modules, but can be any other class in the case |
354 |
AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). |
355 |
|
356 |
The known classes so far are: |
357 |
|
358 |
AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
359 |
AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
360 |
AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
361 |
AnyEvent::Impl::Event based on Event, second best choice. |
362 |
AnyEvent::Impl::Glib based on Glib, third-best choice. |
363 |
AnyEvent::Impl::Tk based on Tk, very bad choice. |
364 |
AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
365 |
AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
366 |
AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
367 |
|
368 |
=item AnyEvent::detect |
369 |
|
370 |
Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
371 |
if necessary. You should only call this function right before you would |
372 |
have created an AnyEvent watcher anyway, that is, as late as possible at |
373 |
runtime. |
374 |
|
375 |
=back |
376 |
|
377 |
=head1 WHAT TO DO IN A MODULE |
378 |
|
379 |
As a module author, you should C<use AnyEvent> and call AnyEvent methods |
380 |
freely, but you should not load a specific event module or rely on it. |
381 |
|
382 |
Be careful when you create watchers in the module body - AnyEvent will |
383 |
decide which event module to use as soon as the first method is called, so |
384 |
by calling AnyEvent in your module body you force the user of your module |
385 |
to load the event module first. |
386 |
|
387 |
Never call C<< ->wait >> on a condition variable unless you I<know> that |
388 |
the C<< ->broadcast >> method has been called on it already. This is |
389 |
because it will stall the whole program, and the whole point of using |
390 |
events is to stay interactive. |
391 |
|
392 |
It is fine, however, to call C<< ->wait >> when the user of your module |
393 |
requests it (i.e. if you create a http request object ad have a method |
394 |
called C<results> that returns the results, it should call C<< ->wait >> |
395 |
freely, as the user of your module knows what she is doing. always). |
396 |
|
397 |
=head1 WHAT TO DO IN THE MAIN PROGRAM |
398 |
|
399 |
There will always be a single main program - the only place that should |
400 |
dictate which event model to use. |
401 |
|
402 |
If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
403 |
do anything special (it does not need to be event-based) and let AnyEvent |
404 |
decide which implementation to chose if some module relies on it. |
405 |
|
406 |
If the main program relies on a specific event model. For example, in |
407 |
Gtk2 programs you have to rely on the Glib module. You should load the |
408 |
event module before loading AnyEvent or any module that uses it: generally |
409 |
speaking, you should load it as early as possible. The reason is that |
410 |
modules might create watchers when they are loaded, and AnyEvent will |
411 |
decide on the event model to use as soon as it creates watchers, and it |
412 |
might chose the wrong one unless you load the correct one yourself. |
413 |
|
414 |
You can chose to use a rather inefficient pure-perl implementation by |
415 |
loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
416 |
behaviour everywhere, but letting AnyEvent chose is generally better. |
417 |
|
418 |
=cut |
419 |
|
420 |
package AnyEvent; |
421 |
|
422 |
no warnings; |
423 |
use strict; |
424 |
|
425 |
use Carp; |
426 |
|
427 |
our $VERSION = '3.12'; |
428 |
our $MODEL; |
429 |
|
430 |
our $AUTOLOAD; |
431 |
our @ISA; |
432 |
|
433 |
our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; |
434 |
|
435 |
our @REGISTRY; |
436 |
|
437 |
my @models = ( |
438 |
[Coro::EV:: => AnyEvent::Impl::CoroEV::], |
439 |
[Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
440 |
[EV:: => AnyEvent::Impl::EV::], |
441 |
[Event:: => AnyEvent::Impl::Event::], |
442 |
[Glib:: => AnyEvent::Impl::Glib::], |
443 |
[Tk:: => AnyEvent::Impl::Tk::], |
444 |
[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
445 |
); |
446 |
my @models_detect = ( |
447 |
[Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
448 |
[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
449 |
); |
450 |
|
451 |
our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
452 |
|
453 |
sub detect() { |
454 |
unless ($MODEL) { |
455 |
no strict 'refs'; |
456 |
|
457 |
if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
458 |
my $model = "AnyEvent::Impl::$1"; |
459 |
if (eval "require $model") { |
460 |
$MODEL = $model; |
461 |
warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
462 |
} |
463 |
} |
464 |
|
465 |
# check for already loaded models |
466 |
unless ($MODEL) { |
467 |
for (@REGISTRY, @models, @models_detect) { |
468 |
my ($package, $model) = @$_; |
469 |
if (${"$package\::VERSION"} > 0) { |
470 |
if (eval "require $model") { |
471 |
$MODEL = $model; |
472 |
warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
473 |
last; |
474 |
} |
475 |
} |
476 |
} |
477 |
|
478 |
unless ($MODEL) { |
479 |
# try to load a model |
480 |
|
481 |
for (@REGISTRY, @models) { |
482 |
my ($package, $model) = @$_; |
483 |
if (eval "require $package" |
484 |
and ${"$package\::VERSION"} > 0 |
485 |
and eval "require $model") { |
486 |
$MODEL = $model; |
487 |
warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1; |
488 |
last; |
489 |
} |
490 |
} |
491 |
|
492 |
$MODEL |
493 |
or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib."; |
494 |
} |
495 |
} |
496 |
|
497 |
unshift @ISA, $MODEL; |
498 |
push @{"$MODEL\::ISA"}, "AnyEvent::Base"; |
499 |
} |
500 |
|
501 |
$MODEL |
502 |
} |
503 |
|
504 |
sub AUTOLOAD { |
505 |
(my $func = $AUTOLOAD) =~ s/.*://; |
506 |
|
507 |
$method{$func} |
508 |
or croak "$func: not a valid method for AnyEvent objects"; |
509 |
|
510 |
detect unless $MODEL; |
511 |
|
512 |
my $class = shift; |
513 |
$class->$func (@_); |
514 |
} |
515 |
|
516 |
package AnyEvent::Base; |
517 |
|
518 |
# default implementation for ->condvar, ->wait, ->broadcast |
519 |
|
520 |
sub condvar { |
521 |
bless \my $flag, "AnyEvent::Base::CondVar" |
522 |
} |
523 |
|
524 |
sub AnyEvent::Base::CondVar::broadcast { |
525 |
${$_[0]}++; |
526 |
} |
527 |
|
528 |
sub AnyEvent::Base::CondVar::wait { |
529 |
AnyEvent->one_event while !${$_[0]}; |
530 |
} |
531 |
|
532 |
# default implementation for ->signal |
533 |
|
534 |
our %SIG_CB; |
535 |
|
536 |
sub signal { |
537 |
my (undef, %arg) = @_; |
538 |
|
539 |
my $signal = uc $arg{signal} |
540 |
or Carp::croak "required option 'signal' is missing"; |
541 |
|
542 |
$SIG_CB{$signal}{$arg{cb}} = $arg{cb}; |
543 |
$SIG{$signal} ||= sub { |
544 |
$_->() for values %{ $SIG_CB{$signal} || {} }; |
545 |
}; |
546 |
|
547 |
bless [$signal, $arg{cb}], "AnyEvent::Base::Signal" |
548 |
} |
549 |
|
550 |
sub AnyEvent::Base::Signal::DESTROY { |
551 |
my ($signal, $cb) = @{$_[0]}; |
552 |
|
553 |
delete $SIG_CB{$signal}{$cb}; |
554 |
|
555 |
$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} }; |
556 |
} |
557 |
|
558 |
# default implementation for ->child |
559 |
|
560 |
our %PID_CB; |
561 |
our $CHLD_W; |
562 |
our $CHLD_DELAY_W; |
563 |
our $PID_IDLE; |
564 |
our $WNOHANG; |
565 |
|
566 |
sub _child_wait { |
567 |
while (0 < (my $pid = waitpid -1, $WNOHANG)) { |
568 |
$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }), |
569 |
(values %{ $PID_CB{0} || {} }); |
570 |
} |
571 |
|
572 |
undef $PID_IDLE; |
573 |
} |
574 |
|
575 |
sub _sigchld { |
576 |
# make sure we deliver these changes "synchronous" with the event loop. |
577 |
$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub { |
578 |
undef $CHLD_DELAY_W; |
579 |
&_child_wait; |
580 |
}); |
581 |
} |
582 |
|
583 |
sub child { |
584 |
my (undef, %arg) = @_; |
585 |
|
586 |
defined (my $pid = $arg{pid} + 0) |
587 |
or Carp::croak "required option 'pid' is missing"; |
588 |
|
589 |
$PID_CB{$pid}{$arg{cb}} = $arg{cb}; |
590 |
|
591 |
unless ($WNOHANG) { |
592 |
$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1; |
593 |
} |
594 |
|
595 |
unless ($CHLD_W) { |
596 |
$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld); |
597 |
# child could be a zombie already, so make at least one round |
598 |
&_sigchld; |
599 |
} |
600 |
|
601 |
bless [$pid, $arg{cb}], "AnyEvent::Base::Child" |
602 |
} |
603 |
|
604 |
sub AnyEvent::Base::Child::DESTROY { |
605 |
my ($pid, $cb) = @{$_[0]}; |
606 |
|
607 |
delete $PID_CB{$pid}{$cb}; |
608 |
delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; |
609 |
|
610 |
undef $CHLD_W unless keys %PID_CB; |
611 |
} |
612 |
|
613 |
=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
614 |
|
615 |
This is an advanced topic that you do not normally need to use AnyEvent in |
616 |
a module. This section is only of use to event loop authors who want to |
617 |
provide AnyEvent compatibility. |
618 |
|
619 |
If you need to support another event library which isn't directly |
620 |
supported by AnyEvent, you can supply your own interface to it by |
621 |
pushing, before the first watcher gets created, the package name of |
622 |
the event module and the package name of the interface to use onto |
623 |
C<@AnyEvent::REGISTRY>. You can do that before and even without loading |
624 |
AnyEvent, so it is reasonably cheap. |
625 |
|
626 |
Example: |
627 |
|
628 |
push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
629 |
|
630 |
This tells AnyEvent to (literally) use the C<urxvt::anyevent::> |
631 |
package/class when it finds the C<urxvt> package/module is already loaded. |
632 |
|
633 |
When AnyEvent is loaded and asked to find a suitable event model, it |
634 |
will first check for the presence of urxvt by trying to C<use> the |
635 |
C<urxvt::anyevent> module. |
636 |
|
637 |
The class should provide implementations for all watcher types. See |
638 |
L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code) |
639 |
and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to |
640 |
see the sources. |
641 |
|
642 |
If you don't provide C<signal> and C<child> watchers than AnyEvent will |
643 |
provide suitable (hopefully) replacements. |
644 |
|
645 |
The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) |
646 |
terminal emulator uses the above line as-is. An interface isn't included |
647 |
in AnyEvent because it doesn't make sense outside the embedded interpreter |
648 |
inside I<rxvt-unicode>, and it is updated and maintained as part of the |
649 |
I<rxvt-unicode> distribution. |
650 |
|
651 |
I<rxvt-unicode> also cheats a bit by not providing blocking access to |
652 |
condition variables: code blocking while waiting for a condition will |
653 |
C<die>. This still works with most modules/usages, and blocking calls must |
654 |
not be done in an interactive application, so it makes sense. |
655 |
|
656 |
=head1 ENVIRONMENT VARIABLES |
657 |
|
658 |
The following environment variables are used by this module: |
659 |
|
660 |
=over 4 |
661 |
|
662 |
=item C<PERL_ANYEVENT_VERBOSE> |
663 |
|
664 |
When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
665 |
model it chooses. |
666 |
|
667 |
=item C<PERL_ANYEVENT_MODEL> |
668 |
|
669 |
This can be used to specify the event model to be used by AnyEvent, before |
670 |
autodetection and -probing kicks in. It must be a string consisting |
671 |
entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended |
672 |
and the resulting module name is loaded and if the load was successful, |
673 |
used as event model. If it fails to load AnyEvent will proceed with |
674 |
autodetection and -probing. |
675 |
|
676 |
This functionality might change in future versions. |
677 |
|
678 |
For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you |
679 |
could start your program like this: |
680 |
|
681 |
PERL_ANYEVENT_MODEL=Perl perl ... |
682 |
|
683 |
=back |
684 |
|
685 |
=head1 EXAMPLE PROGRAM |
686 |
|
687 |
The following program uses an IO watcher to read data from STDIN, a timer |
688 |
to display a message once per second, and a condition variable to quit the |
689 |
program when the user enters quit: |
690 |
|
691 |
use AnyEvent; |
692 |
|
693 |
my $cv = AnyEvent->condvar; |
694 |
|
695 |
my $io_watcher = AnyEvent->io ( |
696 |
fh => \*STDIN, |
697 |
poll => 'r', |
698 |
cb => sub { |
699 |
warn "io event <$_[0]>\n"; # will always output <r> |
700 |
chomp (my $input = <STDIN>); # read a line |
701 |
warn "read: $input\n"; # output what has been read |
702 |
$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
703 |
}, |
704 |
); |
705 |
|
706 |
my $time_watcher; # can only be used once |
707 |
|
708 |
sub new_timer { |
709 |
$timer = AnyEvent->timer (after => 1, cb => sub { |
710 |
warn "timeout\n"; # print 'timeout' about every second |
711 |
&new_timer; # and restart the time |
712 |
}); |
713 |
} |
714 |
|
715 |
new_timer; # create first timer |
716 |
|
717 |
$cv->wait; # wait until user enters /^q/i |
718 |
|
719 |
=head1 REAL-WORLD EXAMPLE |
720 |
|
721 |
Consider the L<Net::FCP> module. It features (among others) the following |
722 |
API calls, which are to freenet what HTTP GET requests are to http: |
723 |
|
724 |
my $data = $fcp->client_get ($url); # blocks |
725 |
|
726 |
my $transaction = $fcp->txn_client_get ($url); # does not block |
727 |
$transaction->cb ( sub { ... } ); # set optional result callback |
728 |
my $data = $transaction->result; # possibly blocks |
729 |
|
730 |
The C<client_get> method works like C<LWP::Simple::get>: it requests the |
731 |
given URL and waits till the data has arrived. It is defined to be: |
732 |
|
733 |
sub client_get { $_[0]->txn_client_get ($_[1])->result } |
734 |
|
735 |
And in fact is automatically generated. This is the blocking API of |
736 |
L<Net::FCP>, and it works as simple as in any other, similar, module. |
737 |
|
738 |
More complicated is C<txn_client_get>: It only creates a transaction |
739 |
(completion, result, ...) object and initiates the transaction. |
740 |
|
741 |
my $txn = bless { }, Net::FCP::Txn::; |
742 |
|
743 |
It also creates a condition variable that is used to signal the completion |
744 |
of the request: |
745 |
|
746 |
$txn->{finished} = AnyAvent->condvar; |
747 |
|
748 |
It then creates a socket in non-blocking mode. |
749 |
|
750 |
socket $txn->{fh}, ...; |
751 |
fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
752 |
connect $txn->{fh}, ... |
753 |
and !$!{EWOULDBLOCK} |
754 |
and !$!{EINPROGRESS} |
755 |
and Carp::croak "unable to connect: $!\n"; |
756 |
|
757 |
Then it creates a write-watcher which gets called whenever an error occurs |
758 |
or the connection succeeds: |
759 |
|
760 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
761 |
|
762 |
And returns this transaction object. The C<fh_ready_w> callback gets |
763 |
called as soon as the event loop detects that the socket is ready for |
764 |
writing. |
765 |
|
766 |
The C<fh_ready_w> method makes the socket blocking again, writes the |
767 |
request data and replaces the watcher by a read watcher (waiting for reply |
768 |
data). The actual code is more complicated, but that doesn't matter for |
769 |
this example: |
770 |
|
771 |
fcntl $txn->{fh}, F_SETFL, 0; |
772 |
syswrite $txn->{fh}, $txn->{request} |
773 |
or die "connection or write error"; |
774 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
775 |
|
776 |
Again, C<fh_ready_r> waits till all data has arrived, and then stores the |
777 |
result and signals any possible waiters that the request ahs finished: |
778 |
|
779 |
sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
780 |
|
781 |
if (end-of-file or data complete) { |
782 |
$txn->{result} = $txn->{buf}; |
783 |
$txn->{finished}->broadcast; |
784 |
$txb->{cb}->($txn) of $txn->{cb}; # also call callback |
785 |
} |
786 |
|
787 |
The C<result> method, finally, just waits for the finished signal (if the |
788 |
request was already finished, it doesn't wait, of course, and returns the |
789 |
data: |
790 |
|
791 |
$txn->{finished}->wait; |
792 |
return $txn->{result}; |
793 |
|
794 |
The actual code goes further and collects all errors (C<die>s, exceptions) |
795 |
that occured during request processing. The C<result> method detects |
796 |
whether an exception as thrown (it is stored inside the $txn object) |
797 |
and just throws the exception, which means connection errors and other |
798 |
problems get reported tot he code that tries to use the result, not in a |
799 |
random callback. |
800 |
|
801 |
All of this enables the following usage styles: |
802 |
|
803 |
1. Blocking: |
804 |
|
805 |
my $data = $fcp->client_get ($url); |
806 |
|
807 |
2. Blocking, but running in parallel: |
808 |
|
809 |
my @datas = map $_->result, |
810 |
map $fcp->txn_client_get ($_), |
811 |
@urls; |
812 |
|
813 |
Both blocking examples work without the module user having to know |
814 |
anything about events. |
815 |
|
816 |
3a. Event-based in a main program, using any supported event module: |
817 |
|
818 |
use EV; |
819 |
|
820 |
$fcp->txn_client_get ($url)->cb (sub { |
821 |
my $txn = shift; |
822 |
my $data = $txn->result; |
823 |
... |
824 |
}); |
825 |
|
826 |
EV::loop; |
827 |
|
828 |
3b. The module user could use AnyEvent, too: |
829 |
|
830 |
use AnyEvent; |
831 |
|
832 |
my $quit = AnyEvent->condvar; |
833 |
|
834 |
$fcp->txn_client_get ($url)->cb (sub { |
835 |
... |
836 |
$quit->broadcast; |
837 |
}); |
838 |
|
839 |
$quit->wait; |
840 |
|
841 |
=head1 FORK |
842 |
|
843 |
Most event libraries are not fork-safe. The ones who are usually are |
844 |
because they are so inefficient. Only L<EV> is fully fork-aware. |
845 |
|
846 |
If you have to fork, you must either do so I<before> creating your first |
847 |
watcher OR you must not use AnyEvent at all in the child. |
848 |
|
849 |
=head1 SECURITY CONSIDERATIONS |
850 |
|
851 |
AnyEvent can be forced to load any event model via |
852 |
$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
853 |
execute arbitrary code or directly gain access, it can easily be used to |
854 |
make the program hang or malfunction in subtle ways, as AnyEvent watchers |
855 |
will not be active when the program uses a different event model than |
856 |
specified in the variable. |
857 |
|
858 |
You can make AnyEvent completely ignore this variable by deleting it |
859 |
before the first watcher gets created, e.g. with a C<BEGIN> block: |
860 |
|
861 |
BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
862 |
|
863 |
use AnyEvent; |
864 |
|
865 |
=head1 SEE ALSO |
866 |
|
867 |
Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
868 |
L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
869 |
L<Event::Lib>, L<Qt>. |
870 |
|
871 |
Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
872 |
L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
873 |
L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
874 |
L<AnyEvent::Impl::Qt>. |
875 |
|
876 |
Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
877 |
|
878 |
=head1 AUTHOR |
879 |
|
880 |
Marc Lehmann <schmorp@schmorp.de> |
881 |
http://home.schmorp.de/ |
882 |
|
883 |
=cut |
884 |
|
885 |
1 |
886 |
|