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Revision: 1.19
Committed: Sun Dec 10 23:59:15 2006 UTC (17 years, 6 months ago) by root
Branch: MAIN
Changes since 1.18: +71 -14 lines
Log Message:
implement sigwatcher

File Contents

# Content
1 =head1 NAME
2
3 AnyEvent - provide framework for multiple event loops
4
5 Event, Coro, Glib, Tk, Perl - 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 wether 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 DESCRIPTION
24
25 L<AnyEvent> provides an identical interface to multiple event loops. This
26 allows module authors to utilise an event loop without forcing module
27 users to use the same event loop (as only a single event loop can coexist
28 peacefully at any one time).
29
30 The interface itself is vaguely similar but not identical to the Event
31 module.
32
33 On the first call of any method, the module tries to detect the currently
34 loaded event loop by probing wether any of the following modules is
35 loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is
36 used. If none is found, the module tries to load these modules in the
37 order given. The first one that could be successfully loaded will be
38 used. If still none could be found, AnyEvent will fall back to a pure-perl
39 event loop, which is also not very efficient.
40
41 Because AnyEvent first checks for modules that are already loaded, loading
42 an Event model explicitly before first using AnyEvent will likely make
43 that model the default. For example:
44
45 use Tk;
46 use AnyEvent;
47
48 # .. AnyEvent will likely default to Tk
49
50 The pure-perl implementation of AnyEvent is called
51 C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52 explicitly.
53
54 =head1 WATCHERS
55
56 AnyEvent has the central concept of a I<watcher>, which is an object that
57 stores relevant data for each kind of event you are waiting for, such as
58 the callback to call, the filehandle to watch, etc.
59
60 These watchers are normal Perl objects with normal Perl lifetime. After
61 creating a watcher it will immediately "watch" for events and invoke
62 the callback. To disable the watcher you have to destroy it (e.g. by
63 setting the variable that stores it to C<undef> or otherwise deleting all
64 references to it).
65
66 All watchers are created by calling a method on the C<AnyEvent> class.
67
68 =head2 IO WATCHERS
69
70 You can create I/O watcher by calling the C<< AnyEvent->io >> method with
71 the following mandatory arguments:
72
73 C<fh> the Perl I<filehandle> (not filedescriptor) to watch for
74 events. C<poll> must be a string that is either C<r> or C<w>, that creates
75 a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback
76 to invoke everytime the filehandle becomes ready.
77
78 Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on
79 a socket you can have one r + one w, not any more (limitation comes from
80 Tk - if you are sure you are not using Tk this limitation is gone).
81
82 Filehandles will be kept alive, so as long as the watcher exists, the
83 filehandle exists, too.
84
85 Example:
86
87 # wait for readability of STDIN, then read a line and disable the watcher
88 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89 chomp (my $input = <STDIN>);
90 warn "read: $input\n";
91 undef $w;
92 });
93
94 =head2 TIME WATCHERS
95
96 You can create a time watcher by calling the C<< AnyEvent->timer >>
97 method with the following mandatory arguments:
98
99 C<after> after how many seconds (fractions are supported) should the timer
100 activate. C<cb> the callback to invoke.
101
102 The timer callback will be invoked at most once: if you want a repeating
103 timer you have to create a new watcher (this is a limitation by both Tk
104 and Glib).
105
106 Example:
107
108 # fire an event after 7.7 seconds
109 my $w = AnyEvent->timer (after => 7.7, cb => sub {
110 warn "timeout\n";
111 });
112
113 # to cancel the timer:
114 undef $w
115
116 =head2 CONDITION WATCHERS
117
118 Condition watchers can be created by calling the C<< AnyEvent->condvar >>
119 method without any arguments.
120
121 A condition watcher watches for a condition - precisely that the C<<
122 ->broadcast >> method has been called.
123
124 The watcher has only two methods:
125
126 =over 4
127
128 =item $cv->wait
129
130 Wait (blocking if necessary) until the C<< ->broadcast >> method has been
131 called on c<$cv>, while servicing other watchers normally.
132
133 Not all event models support a blocking wait - some die in that case, so
134 if you are using this from a module, never require a blocking wait, but
135 let the caller decide wether the call will block or not (for example,
136 by coupling condition variables with some kind of request results and
137 supporting callbacks so the caller knows that getting the result will not
138 block, while still suppporting blockign waits if the caller so desires).
139
140 You can only wait once on a condition - additional calls will return
141 immediately.
142
143 =item $cv->broadcast
144
145 Flag the condition as ready - a running C<< ->wait >> and all further
146 calls to C<wait> will return after this method has been called. If nobody
147 is waiting the broadcast will be remembered..
148
149 Example:
150
151 # wait till the result is ready
152 my $result_ready = AnyEvent->condvar;
153
154 # do something such as adding a timer
155 # or socket watcher the calls $result_ready->broadcast
156 # when the "result" is ready.
157
158 $result_ready->wait;
159
160 =back
161
162 =head2 SIGNAL WATCHERS
163
164 You can listen for signals using a signal watcher, C<signal> is the signal
165 I<name> without any C<SIG> prefix.
166
167 These watchers might use C<%SIG>, so programs overwriting those signals
168 directly will likely not work correctly.
169
170 Example: exit on SIGINT
171
172 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
173
174 =head1 GLOBALS
175
176 =over 4
177
178 =item $AnyEvent::MODEL
179
180 Contains C<undef> until the first watcher is being created. Then it
181 contains the event model that is being used, which is the name of the
182 Perl class implementing the model. This class is usually one of the
183 C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
184 AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
185
186 The known classes so far are:
187
188 AnyEvent::Impl::Coro based on Coro::Event, best choise.
189 AnyEvent::Impl::Event based on Event, also best choice :)
190 AnyEvent::Impl::Glib based on Glib, second-best choice.
191 AnyEvent::Impl::Tk based on Tk, very bad choice.
192 AnyEvent::Impl::Perl pure-perl implementation, inefficient.
193
194 =item AnyEvent::detect
195
196 Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if
197 necessary. You should only call this function right before you would have
198 created an AnyEvent watcher anyway, that is, very late at runtime.
199
200 =back
201
202 =head1 WHAT TO DO IN A MODULE
203
204 As a module author, you should "use AnyEvent" and call AnyEvent methods
205 freely, but you should not load a specific event module or rely on it.
206
207 Be careful when you create watchers in the module body - Anyevent will
208 decide which event module to use as soon as the first method is called, so
209 by calling AnyEvent in your module body you force the user of your module
210 to load the event module first.
211
212 =head1 WHAT TO DO IN THE MAIN PROGRAM
213
214 There will always be a single main program - the only place that should
215 dictate which event model to use.
216
217 If it doesn't care, it can just "use AnyEvent" and use it itself, or not
218 do anything special and let AnyEvent decide which implementation to chose.
219
220 If the main program relies on a specific event model (for example, in Gtk2
221 programs you have to rely on either Glib or Glib::Event), you should load
222 it before loading AnyEvent or any module that uses it, generally, as early
223 as possible. The reason is that modules might create watchers when they
224 are loaded, and AnyEvent will decide on the event model to use as soon as
225 it creates watchers, and it might chose the wrong one unless you load the
226 correct one yourself.
227
228 You can chose to use a rather inefficient pure-perl implementation by
229 loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is
230 generally better.
231
232 =cut
233
234 package AnyEvent;
235
236 no warnings;
237 use strict;
238 use Carp;
239
240 our $VERSION = '2.5';
241 our $MODEL;
242
243 our $AUTOLOAD;
244 our @ISA;
245
246 our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
247
248 our @REGISTRY;
249
250 my @models = (
251 [Coro::Event:: => AnyEvent::Impl::Coro::],
252 [Event:: => AnyEvent::Impl::Event::],
253 [Glib:: => AnyEvent::Impl::Glib::],
254 [Tk:: => AnyEvent::Impl::Tk::],
255 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
256 );
257
258 our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);
259
260 sub detect() {
261 unless ($MODEL) {
262 no strict 'refs';
263
264 # check for already loaded models
265 for (@REGISTRY, @models) {
266 my ($package, $model) = @$_;
267 if (${"$package\::VERSION"} > 0) {
268 if (eval "require $model") {
269 $MODEL = $model;
270 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;
271 last;
272 }
273 }
274 }
275
276 unless ($MODEL) {
277 # try to load a model
278
279 for (@REGISTRY, @models) {
280 my ($package, $model) = @$_;
281 if (eval "require $model") {
282 $MODEL = $model;
283 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
284 last;
285 }
286 }
287
288 $MODEL
289 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
290 }
291
292 unshift @ISA, $MODEL;
293 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
294 }
295
296 $MODEL
297 }
298
299 sub AUTOLOAD {
300 (my $func = $AUTOLOAD) =~ s/.*://;
301
302 $method{$func}
303 or croak "$func: not a valid method for AnyEvent objects";
304
305 detect unless $MODEL;
306
307 my $class = shift;
308 $class->$func (@_);
309 }
310
311 package AnyEvent::Base;
312
313 # default implementation for signal
314
315 our %SIG_CB;
316
317 sub signal {
318 my (undef, %arg) = @_;
319
320 my $signal = uc $arg{signal}
321 or Carp::croak "required option 'signal' is missing";
322
323 my $w = bless [$signal, $arg{cb}], "AnyEvent::Base::Signal";
324
325 $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
326 $SIG{$signal} ||= sub {
327 $_->() for values %{ $SIG_CB{$signal} };
328 };
329
330 $w
331 }
332
333 sub AnyEvent::Base::Signal::DESTROY {
334 my ($signal, $cb) = @{$_[0]};
335
336 delete $SIG_CB{$signal}{$cb};
337
338 $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
339 }
340
341 =head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
342
343 If you need to support another event library which isn't directly
344 supported by AnyEvent, you can supply your own interface to it by
345 pushing, before the first watcher gets created, the package name of
346 the event module and the package name of the interface to use onto
347 C<@AnyEvent::REGISTRY>. You can do that before and even without loading
348 AnyEvent.
349
350 Example:
351
352 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
353
354 This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
355 package/class when it finds the C<urxvt> package/module is loaded. When
356 AnyEvent is loaded and asked to find a suitable event model, it will
357 first check for the presence of urxvt.
358
359 The class should provide implementations for all watcher types (see
360 L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>
361 (Source code) and so on for actual examples, use C<perldoc -m
362 AnyEvent::Impl::Glib> to see the sources).
363
364 The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
365 uses the above line as-is. An interface isn't included in AnyEvent
366 because it doesn't make sense outside the embedded interpreter inside
367 I<rxvt-unicode>, and it is updated and maintained as part of the
368 I<rxvt-unicode> distribution.
369
370 I<rxvt-unicode> also cheats a bit by not providing blocking access to
371 condition variables: code blocking while waiting for a condition will
372 C<die>. This still works with most modules/usages, and blocking calls must
373 not be in an interactive appliation, so it makes sense.
374
375 =head1 ENVIRONMENT VARIABLES
376
377 The following environment variables are used by this module:
378
379 C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
380 model gets used.
381
382 =head1 EXAMPLE
383
384 The following program uses an io watcher to read data from stdin, a timer
385 to display a message once per second, and a condvar to exit the program
386 when the user enters quit:
387
388 use AnyEvent;
389
390 my $cv = AnyEvent->condvar;
391
392 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
393 warn "io event <$_[0]>\n"; # will always output <r>
394 chomp (my $input = <STDIN>); # read a line
395 warn "read: $input\n"; # output what has been read
396 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
397 });
398
399 my $time_watcher; # can only be used once
400
401 sub new_timer {
402 $timer = AnyEvent->timer (after => 1, cb => sub {
403 warn "timeout\n"; # print 'timeout' about every second
404 &new_timer; # and restart the time
405 });
406 }
407
408 new_timer; # create first timer
409
410 $cv->wait; # wait until user enters /^q/i
411
412 =head1 REAL-WORLD EXAMPLE
413
414 Consider the L<Net::FCP> module. It features (among others) the following
415 API calls, which are to freenet what HTTP GET requests are to http:
416
417 my $data = $fcp->client_get ($url); # blocks
418
419 my $transaction = $fcp->txn_client_get ($url); # does not block
420 $transaction->cb ( sub { ... } ); # set optional result callback
421 my $data = $transaction->result; # possibly blocks
422
423 The C<client_get> method works like C<LWP::Simple::get>: it requests the
424 given URL and waits till the data has arrived. It is defined to be:
425
426 sub client_get { $_[0]->txn_client_get ($_[1])->result }
427
428 And in fact is automatically generated. This is the blocking API of
429 L<Net::FCP>, and it works as simple as in any other, similar, module.
430
431 More complicated is C<txn_client_get>: It only creates a transaction
432 (completion, result, ...) object and initiates the transaction.
433
434 my $txn = bless { }, Net::FCP::Txn::;
435
436 It also creates a condition variable that is used to signal the completion
437 of the request:
438
439 $txn->{finished} = AnyAvent->condvar;
440
441 It then creates a socket in non-blocking mode.
442
443 socket $txn->{fh}, ...;
444 fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
445 connect $txn->{fh}, ...
446 and !$!{EWOULDBLOCK}
447 and !$!{EINPROGRESS}
448 and Carp::croak "unable to connect: $!\n";
449
450 Then it creates a write-watcher which gets called whenever an error occurs
451 or the connection succeeds:
452
453 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
454
455 And returns this transaction object. The C<fh_ready_w> callback gets
456 called as soon as the event loop detects that the socket is ready for
457 writing.
458
459 The C<fh_ready_w> method makes the socket blocking again, writes the
460 request data and replaces the watcher by a read watcher (waiting for reply
461 data). The actual code is more complicated, but that doesn't matter for
462 this example:
463
464 fcntl $txn->{fh}, F_SETFL, 0;
465 syswrite $txn->{fh}, $txn->{request}
466 or die "connection or write error";
467 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
468
469 Again, C<fh_ready_r> waits till all data has arrived, and then stores the
470 result and signals any possible waiters that the request ahs finished:
471
472 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
473
474 if (end-of-file or data complete) {
475 $txn->{result} = $txn->{buf};
476 $txn->{finished}->broadcast;
477 $txb->{cb}->($txn) of $txn->{cb}; # also call callback
478 }
479
480 The C<result> method, finally, just waits for the finished signal (if the
481 request was already finished, it doesn't wait, of course, and returns the
482 data:
483
484 $txn->{finished}->wait;
485 return $txn->{result};
486
487 The actual code goes further and collects all errors (C<die>s, exceptions)
488 that occured during request processing. The C<result> method detects
489 wether an exception as thrown (it is stored inside the $txn object)
490 and just throws the exception, which means connection errors and other
491 problems get reported tot he code that tries to use the result, not in a
492 random callback.
493
494 All of this enables the following usage styles:
495
496 1. Blocking:
497
498 my $data = $fcp->client_get ($url);
499
500 2. Blocking, but parallelizing:
501
502 my @datas = map $_->result,
503 map $fcp->txn_client_get ($_),
504 @urls;
505
506 Both blocking examples work without the module user having to know
507 anything about events.
508
509 3a. Event-based in a main program, using any support Event module:
510
511 use Event;
512
513 $fcp->txn_client_get ($url)->cb (sub {
514 my $txn = shift;
515 my $data = $txn->result;
516 ...
517 });
518
519 Event::loop;
520
521 3b. The module user could use AnyEvent, too:
522
523 use AnyEvent;
524
525 my $quit = AnyEvent->condvar;
526
527 $fcp->txn_client_get ($url)->cb (sub {
528 ...
529 $quit->broadcast;
530 });
531
532 $quit->wait;
533
534 =head1 SEE ALSO
535
536 Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.
537
538 Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.
539
540 Nontrivial usage example: L<Net::FCP>.
541
542 =head1
543
544 =cut
545
546 1
547