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=head1 NAME |
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|
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AnyEvent - provide framework for multiple event loops |
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|
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Event, Coro, Glib, Tk - various supported event loops |
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|
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=head1 SYNOPSIS |
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|
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use AnyEvent; |
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|
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my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub { |
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my ($poll_got) = @_; |
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... |
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}); |
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|
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- only one io watcher per $fh and $poll type is allowed |
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(i.e. on a socket you can have one r + one w or one rw |
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watcher, not any more. |
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|
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- AnyEvent will keep filehandles alive, so as long as the watcher exists, |
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the filehandle exists. |
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|
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my $w = AnyEvent->timer (after => $seconds, cb => sub { |
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... |
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}); |
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|
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- io and time watchers get canceled whenever $w is destroyed, so keep a copy |
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|
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- timers can only be used once and must be recreated for repeated operation |
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|
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my $w = AnyEvent->condvar; # kind of main loop replacement |
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$w->wait; # enters main loop till $condvar gets ->broadcast |
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$w->broadcast; # wake up current and all future wait's |
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|
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- condvars are used to give blocking behaviour when neccessary. Create |
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a condvar for any "request" or "event" your module might create, C<< |
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->broadcast >> it when the event happens and provide a function that calls |
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C<< ->wait >> for it. See the examples below. |
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|
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=head1 DESCRIPTION |
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|
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L<AnyEvent> provides an identical interface to multiple event loops. This |
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allows module authors to utilizy an event loop without forcing module |
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users to use the same event loop (as only a single event loop can coexist |
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peacefully at any one time). |
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|
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The interface itself is vaguely similar but not identical to the Event |
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module. |
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|
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On the first call of any method, the module tries to detect the currently |
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loaded event loop by probing wether any of the following modules is |
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loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is |
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used. If none is found, the module tries to load these modules in the |
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order given. The first one that could be successfully loaded will be |
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used. If still none could be found, it will issue an error. |
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|
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=over 4 |
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|
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=cut |
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|
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package AnyEvent; |
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|
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no warnings; |
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use strict 'vars'; |
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use Carp; |
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|
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our $VERSION = 0.3; |
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our $MODEL; |
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|
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our $AUTOLOAD; |
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our @ISA; |
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|
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my @models = ( |
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[Coro => Coro::Event::], |
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[Event => Event::], |
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[Glib => Glib::], |
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[Tk => Tk::], |
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); |
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|
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our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY); |
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|
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sub AUTOLOAD { |
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$AUTOLOAD =~ s/.*://; |
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|
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$method{$AUTOLOAD} |
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or croak "$AUTOLOAD: not a valid method for AnyEvent objects"; |
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|
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unless ($MODEL) { |
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# check for already loaded models |
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for (@models) { |
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my ($model, $package) = @$_; |
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if (scalar keys %{ *{"$package\::"} }) { |
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eval "require AnyEvent::Impl::$model"; |
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last if $MODEL; |
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} |
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} |
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|
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unless ($MODEL) { |
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# try to load a model |
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|
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for (@models) { |
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my ($model, $package) = @$_; |
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eval "require AnyEvent::Impl::$model"; |
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last if $MODEL; |
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} |
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|
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$MODEL |
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or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk."; |
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} |
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} |
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|
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@ISA = $MODEL; |
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|
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my $class = shift; |
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$class->$AUTOLOAD (@_); |
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} |
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|
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=back |
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|
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=head1 EXAMPLE |
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|
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The following program uses an io watcher to read data from stdin, a timer |
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to display a message once per second, and a condvar to exit the program |
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when the user enters quit: |
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|
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use AnyEvent; |
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|
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my $cv = AnyEvent->condvar; |
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my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
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warn "io event <$_[0]>\n"; # will always output <r> |
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chomp (my $input = <STDIN>); # read a line |
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warn "read: $input\n"; # output what has been read |
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$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
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}); |
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my $time_watcher; # can only be used once |
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sub new_timer { |
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$timer = AnyEvent->timer (after => 1, cb => sub { |
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warn "timeout\n"; # print 'timeout' about every second |
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&new_timer; # and restart the time |
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}); |
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} |
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new_timer; # create first timer |
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$cv->wait; # wait until user enters /^q/i |
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|
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=head1 REAL-WORLD EXAMPLE |
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Consider the L<Net::FCP> module. It features (among others) the following |
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API calls, which are to freenet what HTTP GET requests are to http: |
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my $data = $fcp->client_get ($url); # blocks |
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my $transaction = $fcp->txn_client_get ($url); # does not block |
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$transaction->cb ( sub { ... } ); # set optional result callback |
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my $data = $transaction->result; # possibly blocks |
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The C<client_get> method works like C<LWP::Simple::get>: it requests the |
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given URL and waits till the data has arrived. It is defined to be: |
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sub client_get { $_[0]->txn_client_get ($_[1])->result } |
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And in fact is automatically generated. This is the blocking API of |
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L<Net::FCP>, and it works as simple as in any other, similar, module. |
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More complicated is C<txn_client_get>: It only creates a transaction |
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(completion, result, ...) object and initiates the transaction. |
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my $txn = bless { }, Net::FCP::Txn::; |
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It also creates a condition variable that is used to signal the completion |
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of the request: |
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$txn->{finished} = AnyAvent->condvar; |
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It then creates a socket in non-blocking mode. |
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socket $txn->{fh}, ...; |
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fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
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connect $txn->{fh}, ... |
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and !$!{EWOULDBLOCK} |
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and !$!{EINPROGRESS} |
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and Carp::croak "unable to connect: $!\n"; |
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Then it creates a write-watcher which gets called whenever an error occurs |
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or the connection succeeds: |
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$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
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And returns this transaction object. The C<fh_ready_w> callback gets |
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called as soon as the event loop detects that the socket is ready for |
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writing. |
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The C<fh_ready_w> method makes the socket blocking again, writes the |
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request data and replaces the watcher by a read watcher (waiting for reply |
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data). The actual code is more complicated, but that doesn't matter for |
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this example: |
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fcntl $txn->{fh}, F_SETFL, 0; |
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syswrite $txn->{fh}, $txn->{request} |
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or die "connection or write error"; |
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$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
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Again, C<fh_ready_r> waits till all data has arrived, and then stores the |
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result and signals any possible waiters that the request ahs finished: |
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sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
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if (end-of-file or data complete) { |
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$txn->{result} = $txn->{buf}; |
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$txn->{finished}->broadcast; |
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$txb->{cb}->($txn) of $txn->{cb}; # also call callback |
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} |
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The C<result> method, finally, just waits for the finished signal (if the |
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request was already finished, it doesn't wait, of course, and returns the |
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data: |
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$txn->{finished}->wait; |
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return $txn->{result}; |
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The actual code goes further and collects all errors (C<die>s, exceptions) |
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that occured during request processing. The C<result> method detects |
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wether an exception as thrown (it is stored inside the $txn object) |
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and just throws the exception, which means connection errors and other |
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problems get reported tot he code that tries to use the result, not in a |
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random callback. |
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|
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All of this enables the following usage styles: |
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1. Blocking: |
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my $data = $fcp->client_get ($url); |
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2. Blocking, but parallelizing: |
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my @datas = map $_->result, |
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map $fcp->txn_client_get ($_), |
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@urls; |
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|
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Both blocking examples work without the module user having to know |
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anything about events. |
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|
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3a. Event-based in a main program, using any support Event module: |
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use Event; |
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$fcp->txn_client_get ($url)->cb (sub { |
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my $txn = shift; |
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my $data = $txn->result; |
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... |
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}); |
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|
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Event::loop; |
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|
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3b. The module user could use AnyEvent, too: |
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|
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use AnyEvent; |
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|
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my $quit = AnyEvent->condvar; |
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$fcp->txn_client_get ($url)->cb (sub { |
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... |
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$quit->broadcast; |
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}); |
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|
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$quit->wait; |
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|
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=head1 SEE ALSO |
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|
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Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. |
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|
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Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>. |
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Nontrivial usage example: L<Net::FCP>. |
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|
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=head1 |
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|
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=cut |
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1 |
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