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Revision 1.113 by root, Sat May 10 20:30:35 2008 UTC vs.
Revision 1.121 by root, Tue May 20 15:04:43 2008 UTC

15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 15 my $w = AnyEvent->timer (after => $seconds, cb => sub {
16 ... 16 ...
17 }); 17 });
18 18
19 my $w = AnyEvent->condvar; # stores whether a condition was flagged 19 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->send; # wake up current and all future recv's
20 $w->wait; # enters "main loop" till $condvar gets ->send 21 $w->recv; # enters "main loop" till $condvar gets ->send
21 $w->send; # wake up current and all future wait's
22 22
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) 23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 24
25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26nowadays. So what is different about AnyEvent? 26nowadays. So what is different about AnyEvent?
279 279
280Example: fork a process and wait for it 280Example: fork a process and wait for it
281 281
282 my $done = AnyEvent->condvar; 282 my $done = AnyEvent->condvar;
283 283
284 AnyEvent::detect; # force event module to be initialised
285
286 my $pid = fork or exit 5; 284 my $pid = fork or exit 5;
287 285
288 my $w = AnyEvent->child ( 286 my $w = AnyEvent->child (
289 pid => $pid, 287 pid => $pid,
290 cb => sub { 288 cb => sub {
293 $done->send; 291 $done->send;
294 }, 292 },
295 ); 293 );
296 294
297 # do something else, then wait for process exit 295 # do something else, then wait for process exit
298 $done->wait; 296 $done->recv;
299 297
300=head2 CONDITION VARIABLES 298=head2 CONDITION VARIABLES
301 299
302If you are familiar with some event loops you will know that all of them 300If you are familiar with some event loops you will know that all of them
303require you to run some blocking "loop", "run" or similar function that 301require you to run some blocking "loop", "run" or similar function that
326 324
327Condition variables are very useful to signal that something has finished, 325Condition variables are very useful to signal that something has finished,
328for example, if you write a module that does asynchronous http requests, 326for example, if you write a module that does asynchronous http requests,
329then a condition variable would be the ideal candidate to signal the 327then a condition variable would be the ideal candidate to signal the
330availability of results. The user can either act when the callback is 328availability of results. The user can either act when the callback is
331called or can synchronously C<< ->wait >> for the results. 329called or can synchronously C<< ->recv >> for the results.
332 330
333You can also use them to simulate traditional event loops - for example, 331You can also use them to simulate traditional event loops - for example,
334you can block your main program until an event occurs - for example, you 332you can block your main program until an event occurs - for example, you
335could C<< ->wait >> in your main program until the user clicks the Quit 333could C<< ->recv >> in your main program until the user clicks the Quit
336button of your app, which would C<< ->send >> the "quit" event. 334button of your app, which would C<< ->send >> the "quit" event.
337 335
338Note that condition variables recurse into the event loop - if you have 336Note that condition variables recurse into the event loop - if you have
339two pieces of code that call C<< ->wait >> in a round-robbin fashion, you 337two pieces of code that call C<< ->recv >> in a round-robbin fashion, you
340lose. Therefore, condition variables are good to export to your caller, but 338lose. Therefore, condition variables are good to export to your caller, but
341you should avoid making a blocking wait yourself, at least in callbacks, 339you should avoid making a blocking wait yourself, at least in callbacks,
342as this asks for trouble. 340as this asks for trouble.
343 341
344Condition variables are represented by hash refs in perl, and the keys 342Condition variables are represented by hash refs in perl, and the keys
365 cb => sub { $result_ready->send }, 363 cb => sub { $result_ready->send },
366 ); 364 );
367 365
368 # this "blocks" (while handling events) till the callback 366 # this "blocks" (while handling events) till the callback
369 # calls send 367 # calls send
370 $result_ready->wait; 368 $result_ready->recv;
371 369
372=head3 METHODS FOR PRODUCERS 370=head3 METHODS FOR PRODUCERS
373 371
374These methods should only be used by the producing side, i.e. the 372These methods should only be used by the producing side, i.e. the
375code/module that eventually sends the signal. Note that it is also 373code/module that eventually sends the signal. Note that it is also
378 376
379=over 4 377=over 4
380 378
381=item $cv->send (...) 379=item $cv->send (...)
382 380
383Flag the condition as ready - a running C<< ->wait >> and all further 381Flag the condition as ready - a running C<< ->recv >> and all further
384calls to C<wait> will (eventually) return after this method has been 382calls to C<recv> will (eventually) return after this method has been
385called. If nobody is waiting the send will be remembered. 383called. If nobody is waiting the send will be remembered.
386 384
387If a callback has been set on the condition variable, it is called 385If a callback has been set on the condition variable, it is called
388immediately from within send. 386immediately from within send.
389 387
390Any arguments passed to the C<send> call will be returned by all 388Any arguments passed to the C<send> call will be returned by all
391future C<< ->wait >> calls. 389future C<< ->recv >> calls.
392 390
393=item $cv->croak ($error) 391=item $cv->croak ($error)
394 392
395Similar to send, but causes all call's wait C<< ->wait >> to invoke 393Similar to send, but causes all call's to C<< ->recv >> to invoke
396C<Carp::croak> with the given error message/object/scalar. 394C<Carp::croak> with the given error message/object/scalar.
397 395
398This can be used to signal any errors to the condition variable 396This can be used to signal any errors to the condition variable
399user/consumer. 397user/consumer.
400 398
401=item $cv->begin ([group callback]) 399=item $cv->begin ([group callback])
402 400
403=item $cv->end 401=item $cv->end
402
403These two methods are EXPERIMENTAL and MIGHT CHANGE.
404 404
405These two methods can be used to combine many transactions/events into 405These two methods can be used to combine many transactions/events into
406one. For example, a function that pings many hosts in parallel might want 406one. For example, a function that pings many hosts in parallel might want
407to use a condition variable for the whole process. 407to use a condition variable for the whole process.
408 408
454These methods should only be used by the consuming side, i.e. the 454These methods should only be used by the consuming side, i.e. the
455code awaits the condition. 455code awaits the condition.
456 456
457=over 4 457=over 4
458 458
459=item $cv->wait 459=item $cv->recv
460 460
461Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak 461Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462>> methods have been called on c<$cv>, while servicing other watchers 462>> methods have been called on c<$cv>, while servicing other watchers
463normally. 463normally.
464 464
477caller decide whether the call will block or not (for example, by coupling 477caller decide whether the call will block or not (for example, by coupling
478condition variables with some kind of request results and supporting 478condition variables with some kind of request results and supporting
479callbacks so the caller knows that getting the result will not block, 479callbacks so the caller knows that getting the result will not block,
480while still suppporting blocking waits if the caller so desires). 480while still suppporting blocking waits if the caller so desires).
481 481
482Another reason I<never> to C<< ->wait >> in a module is that you cannot 482Another reason I<never> to C<< ->recv >> in a module is that you cannot
483sensibly have two C<< ->wait >>'s in parallel, as that would require 483sensibly have two C<< ->recv >>'s in parallel, as that would require
484multiple interpreters or coroutines/threads, none of which C<AnyEvent> 484multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485can supply. 485can supply.
486 486
487The L<Coro> module, however, I<can> and I<does> supply coroutines and, in 487The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe 488fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489versions and also integrates coroutines into AnyEvent, making blocking 489versions and also integrates coroutines into AnyEvent, making blocking
490C<< ->wait >> calls perfectly safe as long as they are done from another 490C<< ->recv >> calls perfectly safe as long as they are done from another
491coroutine (one that doesn't run the event loop). 491coroutine (one that doesn't run the event loop).
492 492
493You can ensure that C<< -wait >> never blocks by setting a callback and 493You can ensure that C<< -recv >> never blocks by setting a callback and
494only calling C<< ->wait >> from within that callback (or at a later 494only calling C<< ->recv >> from within that callback (or at a later
495time). This will work even when the event loop does not support blocking 495time). This will work even when the event loop does not support blocking
496waits otherwise. 496waits otherwise.
497 497
498=item $bool = $cv->ready 498=item $bool = $cv->ready
499 499
504 504
505This is a mutator function that returns the callback set and optionally 505This is a mutator function that returns the callback set and optionally
506replaces it before doing so. 506replaces it before doing so.
507 507
508The callback will be called when the condition becomes "true", i.e. when 508The callback will be called when the condition becomes "true", i.e. when
509C<send> or C<croak> are called. Calling C<wait> inside the callback 509C<send> or C<croak> are called. Calling C<recv> inside the callback
510or at any later time is guaranteed not to block. 510or at any later time is guaranteed not to block.
511 511
512=back 512=back
513 513
514=head1 GLOBAL VARIABLES AND FUNCTIONS 514=head1 GLOBAL VARIABLES AND FUNCTIONS
582Be careful when you create watchers in the module body - AnyEvent will 582Be careful when you create watchers in the module body - AnyEvent will
583decide which event module to use as soon as the first method is called, so 583decide which event module to use as soon as the first method is called, so
584by calling AnyEvent in your module body you force the user of your module 584by calling AnyEvent in your module body you force the user of your module
585to load the event module first. 585to load the event module first.
586 586
587Never call C<< ->wait >> on a condition variable unless you I<know> that 587Never call C<< ->recv >> on a condition variable unless you I<know> that
588the C<< ->send >> method has been called on it already. This is 588the C<< ->send >> method has been called on it already. This is
589because it will stall the whole program, and the whole point of using 589because it will stall the whole program, and the whole point of using
590events is to stay interactive. 590events is to stay interactive.
591 591
592It is fine, however, to call C<< ->wait >> when the user of your module 592It is fine, however, to call C<< ->recv >> when the user of your module
593requests it (i.e. if you create a http request object ad have a method 593requests it (i.e. if you create a http request object ad have a method
594called C<results> that returns the results, it should call C<< ->wait >> 594called C<results> that returns the results, it should call C<< ->recv >>
595freely, as the user of your module knows what she is doing. always). 595freely, as the user of your module knows what she is doing. always).
596 596
597=head1 WHAT TO DO IN THE MAIN PROGRAM 597=head1 WHAT TO DO IN THE MAIN PROGRAM
598 598
599There will always be a single main program - the only place that should 599There will always be a single main program - the only place that should
691no warnings; 691no warnings;
692use strict; 692use strict;
693 693
694use Carp; 694use Carp;
695 695
696our $VERSION = '3.4'; 696our $VERSION = '3.51';
697our $MODEL; 697our $MODEL;
698 698
699our $AUTOLOAD; 699our $AUTOLOAD;
700our @ISA; 700our @ISA;
701 701
730 1 730 1
731 } else { 731 } else {
732 push @post_detect, $cb; 732 push @post_detect, $cb;
733 733
734 defined wantarray 734 defined wantarray
735 ? bless \$cb, "AnyEvent::Util::Guard" 735 ? bless \$cb, "AnyEvent::Util::PostDetect"
736 : () 736 : ()
737 } 737 }
738} 738}
739 739
740sub AnyEvent::Util::Guard::DESTROY { 740sub AnyEvent::Util::PostDetect::DESTROY {
741 @post_detect = grep $_ != ${$_[0]}, @post_detect; 741 @post_detect = grep $_ != ${$_[0]}, @post_detect;
742} 742}
743 743
744sub detect() { 744sub detect() {
745 unless ($MODEL) { 745 unless ($MODEL) {
808 $class->$func (@_); 808 $class->$func (@_);
809} 809}
810 810
811package AnyEvent::Base; 811package AnyEvent::Base;
812 812
813# default implementation for ->condvar, ->wait, ->broadcast 813# default implementation for ->condvar
814 814
815sub condvar { 815sub condvar {
816 bless \my $flag, "AnyEvent::Base::CondVar" 816 bless {}, AnyEvent::CondVar::
817}
818
819sub AnyEvent::Base::CondVar::broadcast {
820 ${$_[0]}++;
821}
822
823sub AnyEvent::Base::CondVar::wait {
824 AnyEvent->one_event while !${$_[0]};
825} 817}
826 818
827# default implementation for ->signal 819# default implementation for ->signal
828 820
829our %SIG_CB; 821our %SIG_CB;
902 delete $PID_CB{$pid}{$cb}; 894 delete $PID_CB{$pid}{$cb};
903 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; 895 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
904 896
905 undef $CHLD_W unless keys %PID_CB; 897 undef $CHLD_W unless keys %PID_CB;
906} 898}
899
900package AnyEvent::CondVar;
901
902our @ISA = AnyEvent::CondVar::Base::;
903
904package AnyEvent::CondVar::Base;
905
906sub _send {
907 # nop
908}
909
910sub send {
911 my $cv = shift;
912 $cv->{_ae_sent} = [@_];
913 (delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
914 $cv->_send;
915}
916
917sub croak {
918 $_[0]{_ae_croak} = $_[1];
919 $_[0]->send;
920}
921
922sub ready {
923 $_[0]{_ae_sent}
924}
925
926sub _wait {
927 AnyEvent->one_event while !$_[0]{_ae_sent};
928}
929
930sub recv {
931 $_[0]->_wait;
932
933 Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
934 wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
935}
936
937sub cb {
938 $_[0]{_ae_cb} = $_[1] if @_ > 1;
939 $_[0]{_ae_cb}
940}
941
942sub begin {
943 ++$_[0]{_ae_counter};
944 $_[0]{_ae_end_cb} = $_[1] if @_ > 1;
945}
946
947sub end {
948 return if --$_[0]{_ae_counter};
949 &{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};
950}
951
952# undocumented/compatibility with pre-3.4
953*broadcast = \&send;
954*wait = \&_wait;
907 955
908=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 956=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
909 957
910This is an advanced topic that you do not normally need to use AnyEvent in 958This is an advanced topic that you do not normally need to use AnyEvent in
911a module. This section is only of use to event loop authors who want to 959a module. This section is only of use to event loop authors who want to
1000 poll => 'r', 1048 poll => 'r',
1001 cb => sub { 1049 cb => sub {
1002 warn "io event <$_[0]>\n"; # will always output <r> 1050 warn "io event <$_[0]>\n"; # will always output <r>
1003 chomp (my $input = <STDIN>); # read a line 1051 chomp (my $input = <STDIN>); # read a line
1004 warn "read: $input\n"; # output what has been read 1052 warn "read: $input\n"; # output what has been read
1005 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 1053 $cv->send if $input =~ /^q/i; # quit program if /^q/i
1006 }, 1054 },
1007 ); 1055 );
1008 1056
1009 my $time_watcher; # can only be used once 1057 my $time_watcher; # can only be used once
1010 1058
1015 }); 1063 });
1016 } 1064 }
1017 1065
1018 new_timer; # create first timer 1066 new_timer; # create first timer
1019 1067
1020 $cv->wait; # wait until user enters /^q/i 1068 $cv->recv; # wait until user enters /^q/i
1021 1069
1022=head1 REAL-WORLD EXAMPLE 1070=head1 REAL-WORLD EXAMPLE
1023 1071
1024Consider the L<Net::FCP> module. It features (among others) the following 1072Consider the L<Net::FCP> module. It features (among others) the following
1025API calls, which are to freenet what HTTP GET requests are to http: 1073API calls, which are to freenet what HTTP GET requests are to http:
1081 1129
1082 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; 1130 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1083 1131
1084 if (end-of-file or data complete) { 1132 if (end-of-file or data complete) {
1085 $txn->{result} = $txn->{buf}; 1133 $txn->{result} = $txn->{buf};
1086 $txn->{finished}->broadcast; 1134 $txn->{finished}->send;
1087 $txb->{cb}->($txn) of $txn->{cb}; # also call callback 1135 $txb->{cb}->($txn) of $txn->{cb}; # also call callback
1088 } 1136 }
1089 1137
1090The C<result> method, finally, just waits for the finished signal (if the 1138The C<result> method, finally, just waits for the finished signal (if the
1091request was already finished, it doesn't wait, of course, and returns the 1139request was already finished, it doesn't wait, of course, and returns the
1092data: 1140data:
1093 1141
1094 $txn->{finished}->wait; 1142 $txn->{finished}->recv;
1095 return $txn->{result}; 1143 return $txn->{result};
1096 1144
1097The actual code goes further and collects all errors (C<die>s, exceptions) 1145The actual code goes further and collects all errors (C<die>s, exceptions)
1098that occured during request processing. The C<result> method detects 1146that occured during request processing. The C<result> method detects
1099whether an exception as thrown (it is stored inside the $txn object) 1147whether an exception as thrown (it is stored inside the $txn object)
1134 1182
1135 my $quit = AnyEvent->condvar; 1183 my $quit = AnyEvent->condvar;
1136 1184
1137 $fcp->txn_client_get ($url)->cb (sub { 1185 $fcp->txn_client_get ($url)->cb (sub {
1138 ... 1186 ...
1139 $quit->broadcast; 1187 $quit->send;
1140 }); 1188 });
1141 1189
1142 $quit->wait; 1190 $quit->recv;
1143 1191
1144 1192
1145=head1 BENCHMARKS 1193=head1 BENCHMARKS
1146 1194
1147To give you an idea of the performance and overheads that AnyEvent adds 1195To give you an idea of the performance and overheads that AnyEvent adds
1176all watchers, to avoid adding memory overhead. That means closure creation 1224all watchers, to avoid adding memory overhead. That means closure creation
1177and memory usage is not included in the figures. 1225and memory usage is not included in the figures.
1178 1226
1179I<invoke> is the time, in microseconds, used to invoke a simple 1227I<invoke> is the time, in microseconds, used to invoke a simple
1180callback. The callback simply counts down a Perl variable and after it was 1228callback. The callback simply counts down a Perl variable and after it was
1181invoked "watcher" times, it would C<< ->broadcast >> a condvar once to 1229invoked "watcher" times, it would C<< ->send >> a condvar once to
1182signal the end of this phase. 1230signal the end of this phase.
1183 1231
1184I<destroy> is the time, in microseconds, that it takes to destroy a single 1232I<destroy> is the time, in microseconds, that it takes to destroy a single
1185watcher. 1233watcher.
1186 1234

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