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Revision 1.5 by root, Sun Dec 4 09:44:32 2005 UTC vs.
Revision 1.44 by root, Mon Apr 7 19:42:18 2008 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5Event, Coro, Glib, Tk - various supported event loops 5Event, Coro, Glib, Tk, Perl - various supported event loops
6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9use AnyEvent; 9 use AnyEvent;
10 10
11 my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub { 11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {
12 my ($poll_got) = @_;
13 ... 12 ...
14 }); 13 });
15
16- only one io watcher per $fh and $poll type is allowed
17(i.e. on a socket you can have one r + one w or one rw
18watcher, not any more.
19
20- AnyEvent will keep filehandles alive, so as long as the watcher exists,
21the filehandle exists.
22 14
23 my $w = AnyEvent->timer (after => $seconds, cb => sub { 15 my $w = AnyEvent->timer (after => $seconds, cb => sub {
24 ... 16 ...
25 }); 17 });
26 18
27- io and time watchers get canceled whenever $w is destroyed, so keep a copy 19 my $w = AnyEvent->condvar; # stores wether a condition was flagged
28
29- timers can only be used once and must be recreated for repeated operation
30
31 my $w = AnyEvent->condvar; # kind of main loop replacement
32 $w->wait; # enters main loop till $condvar gets ->broadcast 20 $w->wait; # enters "main loop" till $condvar gets ->broadcast
33 $w->broadcast; # wake up current and all future wait's 21 $w->broadcast; # wake up current and all future wait's
34 22
35- condvars are used to give blocking behaviour when neccessary. Create 23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
36a condvar for any "request" or "event" your module might create, C<< 24
37->broadcast >> it when the event happens and provide a function that calls 25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
38C<< ->wait >> for it. See the examples below. 26nowadays. So what is different about AnyEvent?
27
28Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29policy> and AnyEvent is I<small and efficient>.
30
31First and foremost, I<AnyEvent is not an event model> itself, it only
32interfaces to whatever event model the main program happens to use in a
33pragmatic way. For event models and certain classes of immortals alike,
34the statement "there can only be one" is a bitter reality, and AnyEvent
35helps hiding the differences.
36
37The goal of AnyEvent is to offer module authors the ability to do event
38programming (waiting for I/O or timer events) without subscribing to a
39religion, a way of living, and most importantly: without forcing your
40module users into the same thing by forcing them to use the same event
41model you use.
42
43For modules like POE or IO::Async (which is actually doing all I/O
44I<synchronously>...), using them in your module is like joining a
45cult: After you joined, you are dependent on them and you cannot use
46anything else, as it is simply incompatible to everything that isn't
47itself.
48
49AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk
50works fine etc. etc. but none of these work together with the rest: POE
51+ IO::Async? no go. Tk + Event? no go. If your module uses one of
52those, every user of your module has to use it, too. If your module
53uses AnyEvent, it works transparently with all event models it supports
54(including stuff like POE and IO::Async).
55
56In addition of being free of having to use I<the one and only true event
57model>, AnyEvent also is free of bloat and policy: with POE or similar
58modules, you get an enourmous amount of code and strict rules you have
59to follow. AnyEvent, on the other hand, is lean and to the point by only
60offering the functionality that is useful, in as thin as a wrapper as
61technically possible.
62
63Of course, if you want lots of policy (this is arguably somewhat useful
64in many cases) and you want to force your users to the one and only event
65model your module forces on them, you should I<not> use this module.
66
39 67
40=head1 DESCRIPTION 68=head1 DESCRIPTION
41 69
42L<AnyEvent> provides an identical interface to multiple event loops. This 70L<AnyEvent> provides an identical interface to multiple event loops. This
43allows module authors to utilizy an event loop without forcing module 71allows module authors to utilise an event loop without forcing module
44users to use the same event loop (as only a single event loop can coexist 72users to use the same event loop (as only a single event loop can coexist
45peacefully at any one time). 73peacefully at any one time).
46 74
47The interface itself is vaguely similar but not identical to the Event 75The interface itself is vaguely similar but not identical to the Event
48module. 76module.
50On the first call of any method, the module tries to detect the currently 78On the first call of any method, the module tries to detect the currently
51loaded event loop by probing wether any of the following modules is 79loaded event loop by probing wether any of the following modules is
52loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is 80loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is
53used. If none is found, the module tries to load these modules in the 81used. If none is found, the module tries to load these modules in the
54order given. The first one that could be successfully loaded will be 82order given. The first one that could be successfully loaded will be
55used. If still none could be found, it will issue an error. 83used. If still none could be found, AnyEvent will fall back to a pure-perl
84event loop, which is also not very efficient.
85
86Because AnyEvent first checks for modules that are already loaded, loading
87an Event model explicitly before first using AnyEvent will likely make
88that model the default. For example:
89
90 use Tk;
91 use AnyEvent;
92
93 # .. AnyEvent will likely default to Tk
94
95The pure-perl implementation of AnyEvent is called
96C<AnyEvent::Impl::Perl>. Like other event modules you can load it
97explicitly.
98
99=head1 WATCHERS
100
101AnyEvent has the central concept of a I<watcher>, which is an object that
102stores relevant data for each kind of event you are waiting for, such as
103the callback to call, the filehandle to watch, etc.
104
105These watchers are normal Perl objects with normal Perl lifetime. After
106creating a watcher it will immediately "watch" for events and invoke
107the callback. To disable the watcher you have to destroy it (e.g. by
108setting the variable that stores it to C<undef> or otherwise deleting all
109references to it).
110
111All watchers are created by calling a method on the C<AnyEvent> class.
112
113=head2 IO WATCHERS
114
115You can create I/O watcher by calling the C<< AnyEvent->io >> method with
116the following mandatory arguments:
117
118C<fh> the Perl I<filehandle> (not filedescriptor) to watch for
119events. C<poll> must be a string that is either C<r> or C<w>, that creates
120a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback
121to invoke everytime the filehandle becomes ready.
122
123Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on
124a socket you can have one r + one w, not any more (limitation comes from
125Tk - if you are sure you are not using Tk this limitation is gone).
126
127Filehandles will be kept alive, so as long as the watcher exists, the
128filehandle exists, too.
129
130Example:
131
132 # wait for readability of STDIN, then read a line and disable the watcher
133 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
134 chomp (my $input = <STDIN>);
135 warn "read: $input\n";
136 undef $w;
137 });
138
139=head2 TIME WATCHERS
140
141You can create a time watcher by calling the C<< AnyEvent->timer >>
142method with the following mandatory arguments:
143
144C<after> after how many seconds (fractions are supported) should the timer
145activate. C<cb> the callback to invoke.
146
147The timer callback will be invoked at most once: if you want a repeating
148timer you have to create a new watcher (this is a limitation by both Tk
149and Glib).
150
151Example:
152
153 # fire an event after 7.7 seconds
154 my $w = AnyEvent->timer (after => 7.7, cb => sub {
155 warn "timeout\n";
156 });
157
158 # to cancel the timer:
159 undef $w;
160
161=head2 CONDITION WATCHERS
162
163Condition watchers can be created by calling the C<< AnyEvent->condvar >>
164method without any arguments.
165
166A condition watcher watches for a condition - precisely that the C<<
167->broadcast >> method has been called.
168
169Note that condition watchers recurse into the event loop - if you have
170two watchers that call C<< ->wait >> in a round-robbin fashion, you
171lose. Therefore, condition watchers are good to export to your caller, but
172you should avoid making a blocking wait, at least in callbacks, as this
173usually asks for trouble.
174
175The watcher has only two methods:
56 176
57=over 4 177=over 4
58 178
179=item $cv->wait
180
181Wait (blocking if necessary) until the C<< ->broadcast >> method has been
182called on c<$cv>, while servicing other watchers normally.
183
184Not all event models support a blocking wait - some die in that case, so
185if you are using this from a module, never require a blocking wait, but
186let the caller decide wether the call will block or not (for example,
187by coupling condition variables with some kind of request results and
188supporting callbacks so the caller knows that getting the result will not
189block, while still suppporting blockign waits if the caller so desires).
190
191You can only wait once on a condition - additional calls will return
192immediately.
193
194=item $cv->broadcast
195
196Flag the condition as ready - a running C<< ->wait >> and all further
197calls to C<wait> will return after this method has been called. If nobody
198is waiting the broadcast will be remembered..
199
200Example:
201
202 # wait till the result is ready
203 my $result_ready = AnyEvent->condvar;
204
205 # do something such as adding a timer
206 # or socket watcher the calls $result_ready->broadcast
207 # when the "result" is ready.
208
209 $result_ready->wait;
210
211=back
212
213=head2 SIGNAL WATCHERS
214
215You can listen for signals using a signal watcher, C<signal> is the signal
216I<name> without any C<SIG> prefix. Multiple signals events can be clumped
217together into one callback invocation, and callback invocation might or
218might not be asynchronous.
219
220These watchers might use C<%SIG>, so programs overwriting those signals
221directly will likely not work correctly.
222
223Example: exit on SIGINT
224
225 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
226
227=head2 CHILD PROCESS WATCHERS
228
229You can also listen for the status of a child process specified by the
230C<pid> argument (or any child if the pid argument is 0). The watcher will
231trigger as often as status change for the child are received. This works
232by installing a signal handler for C<SIGCHLD>. The callback will be called with
233the pid and exit status (as returned by waitpid).
234
235Example: wait for pid 1333
236
237 my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
238
239=head1 GLOBALS
240
241=over 4
242
243=item $AnyEvent::MODEL
244
245Contains C<undef> until the first watcher is being created. Then it
246contains the event model that is being used, which is the name of the
247Perl class implementing the model. This class is usually one of the
248C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
249AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
250
251The known classes so far are:
252
253 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
254 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
255 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
256 AnyEvent::Impl::Event based on Event, also second best choice :)
257 AnyEvent::Impl::Glib based on Glib, second-best choice.
258 AnyEvent::Impl::Tk based on Tk, very bad choice.
259 AnyEvent::Impl::Perl pure-perl implementation, inefficient.
260
261=item AnyEvent::detect
262
263Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if
264necessary. You should only call this function right before you would have
265created an AnyEvent watcher anyway, that is, very late at runtime.
266
267=back
268
269=head1 WHAT TO DO IN A MODULE
270
271As a module author, you should "use AnyEvent" and call AnyEvent methods
272freely, but you should not load a specific event module or rely on it.
273
274Be careful when you create watchers in the module body - Anyevent will
275decide which event module to use as soon as the first method is called, so
276by calling AnyEvent in your module body you force the user of your module
277to load the event module first.
278
279=head1 WHAT TO DO IN THE MAIN PROGRAM
280
281There will always be a single main program - the only place that should
282dictate which event model to use.
283
284If it doesn't care, it can just "use AnyEvent" and use it itself, or not
285do anything special and let AnyEvent decide which implementation to chose.
286
287If the main program relies on a specific event model (for example, in Gtk2
288programs you have to rely on either Glib or Glib::Event), you should load
289it before loading AnyEvent or any module that uses it, generally, as early
290as possible. The reason is that modules might create watchers when they
291are loaded, and AnyEvent will decide on the event model to use as soon as
292it creates watchers, and it might chose the wrong one unless you load the
293correct one yourself.
294
295You can chose to use a rather inefficient pure-perl implementation by
296loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is
297generally better.
298
59=cut 299=cut
60 300
61package AnyEvent; 301package AnyEvent;
62 302
63no warnings; 303no warnings;
64use strict 'vars'; 304use strict;
305
65use Carp; 306use Carp;
66 307
67our $VERSION = 0.3; 308our $VERSION = '3.0';
68our $MODEL; 309our $MODEL;
69 310
70our $AUTOLOAD; 311our $AUTOLOAD;
71our @ISA; 312our @ISA;
72 313
314our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
315
316our @REGISTRY;
317
73my @models = ( 318my @models = (
74 [Coro => Coro::Event::], 319 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
75 [Event => Event::], 320 [EV:: => AnyEvent::Impl::EV::],
76 [Glib => Glib::], 321 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
77 [Tk => Tk::], 322 [Event:: => AnyEvent::Impl::Event::],
323 [Glib:: => AnyEvent::Impl::Glib::],
324 [Tk:: => AnyEvent::Impl::Tk::],
325 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
78); 326);
79 327
80our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY); 328our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);
81 329
82sub AUTOLOAD { 330sub detect() {
83 $AUTOLOAD =~ s/.*://;
84
85 $method{$AUTOLOAD}
86 or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
87
88 unless ($MODEL) { 331 unless ($MODEL) {
332 no strict 'refs';
333
89 # check for already loaded models 334 # check for already loaded models
90 for (@models) { 335 for (@REGISTRY, @models) {
91 my ($model, $package) = @$_; 336 my ($package, $model) = @$_;
92 if (scalar keys %{ *{"$package\::"} }) { 337 if (${"$package\::VERSION"} > 0) {
93 eval "require AnyEvent::Impl::$model"; 338 if (eval "require $model") {
94 last if $MODEL; 339 $MODEL = $model;
340 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;
341 last;
342 }
95 } 343 }
96 } 344 }
97 345
98 unless ($MODEL) { 346 unless ($MODEL) {
99 # try to load a model 347 # try to load a model
100 348
101 for (@models) { 349 for (@REGISTRY, @models) {
102 my ($model, $package) = @$_; 350 my ($package, $model) = @$_;
103 eval "require AnyEvent::Impl::$model"; 351 if (eval "require $package"
104 last if $MODEL; 352 and ${"$package\::VERSION"} > 0
353 and eval "require $model") {
354 $MODEL = $model;
355 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
356 last;
357 }
105 } 358 }
106 359
107 $MODEL 360 $MODEL
108 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk."; 361 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), Glib or Tk.";
109 } 362 }
363
364 unshift @ISA, $MODEL;
365 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
110 } 366 }
111 367
112 @ISA = $MODEL; 368 $MODEL
369}
370
371sub AUTOLOAD {
372 (my $func = $AUTOLOAD) =~ s/.*://;
373
374 $method{$func}
375 or croak "$func: not a valid method for AnyEvent objects";
376
377 detect unless $MODEL;
113 378
114 my $class = shift; 379 my $class = shift;
115 $class->$AUTOLOAD (@_); 380 $class->$func (@_);
116} 381}
117 382
118=back 383package AnyEvent::Base;
384
385# default implementation for ->condvar, ->wait, ->broadcast
386
387sub condvar {
388 bless \my $flag, "AnyEvent::Base::CondVar"
389}
390
391sub AnyEvent::Base::CondVar::broadcast {
392 ${$_[0]}++;
393}
394
395sub AnyEvent::Base::CondVar::wait {
396 AnyEvent->one_event while !${$_[0]};
397}
398
399# default implementation for ->signal
400
401our %SIG_CB;
402
403sub signal {
404 my (undef, %arg) = @_;
405
406 my $signal = uc $arg{signal}
407 or Carp::croak "required option 'signal' is missing";
408
409 $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
410 $SIG{$signal} ||= sub {
411 $_->() for values %{ $SIG_CB{$signal} || {} };
412 };
413
414 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
415}
416
417sub AnyEvent::Base::Signal::DESTROY {
418 my ($signal, $cb) = @{$_[0]};
419
420 delete $SIG_CB{$signal}{$cb};
421
422 $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
423}
424
425# default implementation for ->child
426
427our %PID_CB;
428our $CHLD_W;
429our $CHLD_DELAY_W;
430our $PID_IDLE;
431our $WNOHANG;
432
433sub _child_wait {
434 while (0 < (my $pid = waitpid -1, $WNOHANG)) {
435 $_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
436 (values %{ $PID_CB{0} || {} });
437 }
438
439 undef $PID_IDLE;
440}
441
442sub _sigchld {
443 # make sure we deliver these changes "synchronous" with the event loop.
444 $CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
445 undef $CHLD_DELAY_W;
446 &_child_wait;
447 });
448}
449
450sub child {
451 my (undef, %arg) = @_;
452
453 defined (my $pid = $arg{pid} + 0)
454 or Carp::croak "required option 'pid' is missing";
455
456 $PID_CB{$pid}{$arg{cb}} = $arg{cb};
457
458 unless ($WNOHANG) {
459 $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
460 }
461
462 unless ($CHLD_W) {
463 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
464 # child could be a zombie already, so make at least one round
465 &_sigchld;
466 }
467
468 bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
469}
470
471sub AnyEvent::Base::Child::DESTROY {
472 my ($pid, $cb) = @{$_[0]};
473
474 delete $PID_CB{$pid}{$cb};
475 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
476
477 undef $CHLD_W unless keys %PID_CB;
478}
479
480=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
481
482If you need to support another event library which isn't directly
483supported by AnyEvent, you can supply your own interface to it by
484pushing, before the first watcher gets created, the package name of
485the event module and the package name of the interface to use onto
486C<@AnyEvent::REGISTRY>. You can do that before and even without loading
487AnyEvent.
488
489Example:
490
491 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
492
493This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
494package/class when it finds the C<urxvt> package/module is loaded. When
495AnyEvent is loaded and asked to find a suitable event model, it will
496first check for the presence of urxvt.
497
498The class should provide implementations for all watcher types (see
499L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>
500(Source code) and so on for actual examples, use C<perldoc -m
501AnyEvent::Impl::Glib> to see the sources).
502
503The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
504uses the above line as-is. An interface isn't included in AnyEvent
505because it doesn't make sense outside the embedded interpreter inside
506I<rxvt-unicode>, and it is updated and maintained as part of the
507I<rxvt-unicode> distribution.
508
509I<rxvt-unicode> also cheats a bit by not providing blocking access to
510condition variables: code blocking while waiting for a condition will
511C<die>. This still works with most modules/usages, and blocking calls must
512not be in an interactive application, so it makes sense.
513
514=head1 ENVIRONMENT VARIABLES
515
516The following environment variables are used by this module:
517
518C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
519model gets used.
119 520
120=head1 EXAMPLE 521=head1 EXAMPLE
121 522
122The following program uses an io watcher to read data from stdin, a timer 523The following program uses an io watcher to read data from stdin, a timer
123to display a message once per second, and a condvar to exit the program 524to display a message once per second, and a condvar to exit the program
183 connect $txn->{fh}, ... 584 connect $txn->{fh}, ...
184 and !$!{EWOULDBLOCK} 585 and !$!{EWOULDBLOCK}
185 and !$!{EINPROGRESS} 586 and !$!{EINPROGRESS}
186 and Carp::croak "unable to connect: $!\n"; 587 and Carp::croak "unable to connect: $!\n";
187 588
188Then it creates a write-watcher which gets called wehnever an error occurs 589Then it creates a write-watcher which gets called whenever an error occurs
189or the connection succeeds: 590or the connection succeeds:
190 591
191 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); 592 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
192 593
193And returns this transaction object. The C<fh_ready_w> callback gets 594And returns this transaction object. The C<fh_ready_w> callback gets
210 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; 611 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
211 612
212 if (end-of-file or data complete) { 613 if (end-of-file or data complete) {
213 $txn->{result} = $txn->{buf}; 614 $txn->{result} = $txn->{buf};
214 $txn->{finished}->broadcast; 615 $txn->{finished}->broadcast;
616 $txb->{cb}->($txn) of $txn->{cb}; # also call callback
215 } 617 }
216 618
217The C<result> method, finally, just waits for the finished signal (if the 619The C<result> method, finally, just waits for the finished signal (if the
218request was already finished, it doesn't wait, of course, and returns the 620request was already finished, it doesn't wait, of course, and returns the
219data: 621data:
220 622
221 $txn->{finished}->wait; 623 $txn->{finished}->wait;
222 return $txn->{buf}; 624 return $txn->{result};
223 625
224The actual code goes further and collects all errors (C<die>s, exceptions) 626The actual code goes further and collects all errors (C<die>s, exceptions)
225that occured during request processing. The C<result> method detects 627that occured during request processing. The C<result> method detects
226wether an exception as thrown (it is stored inside the $txn object) 628wether an exception as thrown (it is stored inside the $txn object)
227and just throws the exception, which means connection errors and other 629and just throws the exception, which means connection errors and other

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