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=head1 NAME |
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|
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EV::Loop::Async - run an EV event loop asynchronously |
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|
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=head1 SYNOPSIS |
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|
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use EV::Loop::Async; |
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|
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my $loop = EV::Loop::Async::default; |
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my $timer; |
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my $flag; |
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|
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# create a watcher, but make sure the loop is locked |
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{ |
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$loop->scope_lock; # lock the loop structures |
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$timer = $loop->timer (5, 1, sub { $flag = 1 }); |
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$loop->notify; # tell loop to take note of the timer |
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} |
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|
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1 while $flag; # $flag will be set asynchronously |
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|
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# implement a critical section, uninterrupted by any callbacks |
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{ |
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$loop->interrupt->scope_block; |
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# critical section, no watcher callback interruptions |
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} |
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|
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# stop the timer watcher again - locking is required once more |
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{ |
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$loop->scope_lock; # lock the loop structures |
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$timer->stop; |
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# no need to notify |
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} |
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|
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=head1 DESCRIPTION |
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|
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This module implements a rather specialised event loop - it takes a normal |
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L<EV> event loop and runs it in a separate thread. That means it will poll |
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for events even while your foreground Perl interpreter is busy (you don't |
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need to have perls pseudo-threads enabled for this either). |
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|
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Whenever the event loop detecs new events, it will interrupt perl and ask |
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it to invoke all the pending watcher callbacks. This invocation will be |
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"synchronous" (in the perl thread), but it can happen at any time. |
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|
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See the documentation for L<Async::Interrupt> for details on when and how |
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your perl program can be interrupted (and how to avoid it), and how to |
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integrate background event loops into foreground ones. |
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|
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=head1 FAQ |
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|
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=over 4 |
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|
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=item Why on earth...??? |
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|
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Sometimes you need lower latency for specific events, but it's too heavy |
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to continuously poll for events. And perl already does this for you |
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anyways, so this module only uses this existing mechanism. |
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|
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=item When do I have to lock? |
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|
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When in doubt, lock. Do not start or stop a watcher, do not create a |
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watcher (unless with the C<_ns> methods) and do not DESTROY an active |
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watcher without locking either. |
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|
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Any other event loop modifications need to be done while locked as |
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well. So when in doubt, lock (best using C<scope_lock>). |
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|
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=item Why explicit locking? |
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|
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Because I was too lazy to wrap everything and there are probably only a |
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few people on this world using this module. |
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|
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=back |
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|
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=head1 FUNCTIONS, METHODS AND VARIABLES OF THIS MODULE |
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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 EV::Loop::Async; |
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|
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use common::sense; |
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|
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use EV (); |
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use Async::Interrupt (); |
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|
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use base 'EV::Loop'; |
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|
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BEGIN { |
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our $VERSION = '0.03'; |
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|
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require XSLoader; |
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XSLoader::load ("EV::Loop::Async", $VERSION); |
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} |
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|
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=item $loop = EV::Loop::Async::default |
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|
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Return the default loop, usable by all programs. The default loop will be |
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created on the first call to C<default> by calling X<new EV::Loop>, and |
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should be used by all programs unless they have special requirements. |
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|
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The associated L<Async::Interrupt> object is stored in |
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C<$EV::Loop::Async::AI>, and can be used to lock critical sections etc. |
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|
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=cut |
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|
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our ($LOOP, $INTERRUPT); |
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|
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sub default() { |
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$LOOP || do { |
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$LOOP = new EV::Loop::Async; |
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$INTERRUPT = $LOOP->interrupt; |
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|
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$LOOP |
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} |
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} |
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|
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=item $EV::Loop::Async::LOOP |
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|
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The default async loop, available after the first call to |
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C<EV::Loop::Async::default>. |
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|
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=item $EV::Loop::Async::INTERRUPT |
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|
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The default loop's L<Async::Interrupt> object, for easy access. |
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|
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Example: create a section of code where no callback invocations will |
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interrupt: |
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|
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{ |
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$EV::Loop::Async::INTERRUPT->scope_block; |
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# no default loop callbacks will be executed here. |
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# the loop will not be locked, however. |
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} |
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|
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Example: embed the default EV::Async::Loop loop into the default L<EV> |
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loop (note that it could be any other event loop as well). |
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|
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my $async_w = EV::io |
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$EV::Loop::Async::LOOP->interrupt->pipe_fileno, |
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EV::READ, |
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sub { }; |
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|
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=item $loop = new EV::Loop::Async $flags, [Async-Interrupt-Arguments...] |
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|
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This constructor: |
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|
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=over 4 |
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|
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=item 1. creates a new C<EV::Loop> (similar C<new EV::Loop>). |
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|
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=item 2. creates a new L<Async::Interrupt> object and attaches itself to it. |
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|
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=item 3. creates a new background thread. |
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|
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=item 4. runs C<< $loop->run >> in that thread. |
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|
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=back |
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|
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The resulting loop will be running and unlocked when it is returned. |
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|
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Example: create a new loop, block it's interrupt object and embed |
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it into the foreground L<AnyEvent> event loop. This basically runs the |
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C<EV::Loop::Async> loop in a synchronous way inside another loop. |
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|
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my $loop = new EV::Loop::Async 0; |
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my $async = $loop->interrupt; |
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|
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$async->block; |
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|
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my $async_w = AnyEvent->io ( |
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fh => $async->pipe_fileno, |
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poll => "r", |
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cb => sub { |
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# temporarily unblock to handle events |
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$async->unblock; |
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$async->block; |
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}, |
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); |
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|
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=cut |
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|
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sub new { |
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my ($class, $flags, @asy) = @_; |
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|
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my $self = bless $class->SUPER::new ($flags), $class; |
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my ($c_func, $c_arg) = _c_func $self; |
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my $asy = new Async::Interrupt @asy, c_cb => [$c_func, $c_arg]; |
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$self->_attach ($asy, $asy->signal_func); |
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|
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$self |
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} |
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|
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=item $loop->notify |
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|
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Wake up the asynchronous loop. This is useful after registering a new |
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watcher, to ensure that the background event loop integrates the new |
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watcher(s) (which only happens when it iterates, which you can force by |
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calling this method). |
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|
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Without calling this method, the event loop I<eventually> takes notice |
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of new watchers, bit when this happens is not well-defined (can be |
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instantaneous, or take a few hours). |
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|
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No locking is required. |
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|
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Example: lock the loop, create a timer, nudge the loop so it takes notice |
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of the new timer, then evily busy-wait till the timer fires. |
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|
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my $timer; |
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my $flag; |
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|
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{ |
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$loop->scope_lock; |
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$timer = $loop->timer (1, 0, sub { $flag = 1 }); |
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$loop->notify; |
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} |
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|
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1 until $flag; |
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|
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=item $loop->lock |
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|
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=item $loop->unlock |
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|
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Lock/unlock the loop data structures. Since the event loop runs in |
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a separate thread, you have to lock the loop data structures before |
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accessing them in any way. Since I was lazy, you have to do this manually. |
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|
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You must lock under the same conditions as you would have to lock the |
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underlying C library, e.g. when starting or stopping watchers (but not |
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when creating or destroying them, but note that create and destroy often |
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starts and stops for you, in which case you have to lock). |
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|
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When in doubt, lock. |
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|
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See also the next method, C<< $loop->scope_lock >> for a more failsafe way |
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to lock parts of your code. |
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|
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Note that there must be exactly one call of "unblock" for every previous |
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call to "block" (i.e. calls can nest). |
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|
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=item $loop->scope_lock |
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|
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Calls C<lock> immediately, and C<unlock> automatically whent he current |
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scope is left. |
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|
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=item $loop->set_max_foreground_loops ($max_loops) |
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|
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The background loop will immediately stop polling for new events after it |
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has collected at least one new event, regardless of how long it then takes |
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to actually handle them. |
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|
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When Perl finally handles the events, there could be many more ready |
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file descriptors. To improve latency and performance, you can ask |
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C<EV::Loop::Async> to loop an additional number of times in the foreground |
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after invoking the callbacks, effectively doing the polling in the |
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foreground. |
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|
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The default is C<0>, meaning that no foreground polling will be done. A |
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value of C<1> means that, after handling the pending events, it will call |
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C<< $loop->loop (EV::LOOP_NONBLOCK) >> and handle the resulting events, if |
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any. A value of C<2> means that this will be iterated twice. |
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|
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When a foreground event poll does not yield any new events, then no |
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further iterations will be made, so this is only a I<maximum> value of |
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additional loop runs. |
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|
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Take also note of the standard EV C<set_io_collect_interval> |
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functionality, which can achieve a similar, but different, effect - YMMV. |
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|
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=back |
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|
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=head1 SEE ALSO |
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|
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L<EV>, L<Async::Interrupt>. |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
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=cut |
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1 |
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