--- AnyEvent/README 2008/10/30 03:43:13 1.33 +++ AnyEvent/README 2009/06/07 16:48:38 1.39 @@ -1,27 +1,34 @@ NAME AnyEvent - provide framework for multiple event loops - EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event - loops + EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported + event loops. SYNOPSIS use AnyEvent; - my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... }); + # file descriptor readable + my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); + # one-shot or repeating timers my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... print AnyEvent->now; # prints current event loop time print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. + # POSIX signal my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); + # child process exit my $w = AnyEvent->child (pid => $pid, cb => sub { my ($pid, $status) = @_; ... }); + # called when event loop idle (if applicable) + my $w = AnyEvent->idle (cb => sub { ... }); + my $w = AnyEvent->condvar; # stores whether a condition was flagged $w->send; # wake up current and all future recv's $w->recv; # enters "main loop" till $condvar gets ->send @@ -134,6 +141,12 @@ callback when the event occurs (of course, only when the event model is in control). + Note that callbacks must not permanently change global variables + potentially in use by the event loop (such as $_ or $[) and that + callbacks must not "die". The former is good programming practise in + Perl and the latter stems from the fact that exception handling differs + widely between event loops. + To disable the watcher you have to destroy it (e.g. by setting the variable you store it in to "undef" or otherwise deleting all references to it). @@ -158,11 +171,17 @@ You can create an I/O watcher by calling the "AnyEvent->io" method with the following mandatory key-value pairs as arguments: - "fh" the Perl *file handle* (*not* file descriptor) to watch for events - (AnyEvent might or might not keep a reference to this file handle). + "fh" is the Perl *file handle* (*not* file descriptor) to watch for + events (AnyEvent might or might not keep a reference to this file + handle). Note that only file handles pointing to things for which + non-blocking operation makes sense are allowed. This includes sockets, + most character devices, pipes, fifos and so on, but not for example + files or block devices. + "poll" must be a string that is either "r" or "w", which creates a - watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" - is the callback to invoke each time the file handle becomes ready. + watcher waiting for "r"eadable or "w"ritable events, respectively. + + "cb" is the callback to invoke each time the file handle becomes ready. Although the callback might get passed parameters, their value and presence is undefined and you cannot rely on them. Portable AnyEvent @@ -304,6 +323,20 @@ the difference between "AnyEvent->time" and "AnyEvent->now" into account. + AnyEvent->now_update + Some event loops (such as EV or AnyEvent::Impl::Perl) cache the + current time for each loop iteration (see the discussion of + AnyEvent->now, above). + + When a callback runs for a long time (or when the process sleeps), + then this "current" time will differ substantially from the real + time, which might affect timers and time-outs. + + When this is the case, you can call this method, which will update + the event loop's idea of "current time". + + Note that updating the time *might* cause some events to be handled. + SIGNAL WATCHERS You can watch for signals using a signal watcher, "signal" is the signal *name* in uppercase and without any "SIG" prefix, "cb" is the Perl @@ -376,6 +409,40 @@ # do something else, then wait for process exit $done->recv; + IDLE WATCHERS + Sometimes there is a need to do something, but it is not so important to + do it instantly, but only when there is nothing better to do. This + "nothing better to do" is usually defined to be "no other events need + attention by the event loop". + + Idle watchers ideally get invoked when the event loop has nothing better + to do, just before it would block the process to wait for new events. + Instead of blocking, the idle watcher is invoked. + + Most event loops unfortunately do not really support idle watchers (only + EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent + will simply call the callback "from time to time". + + Example: read lines from STDIN, but only process them when the program + is otherwise idle: + + my @lines; # read data + my $idle_w; + my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { + push @lines, scalar ; + + # start an idle watcher, if not already done + $idle_w ||= AnyEvent->idle (cb => sub { + # handle only one line, when there are lines left + if (my $line = shift @lines) { + print "handled when idle: $line"; + } else { + # otherwise disable the idle watcher again + undef $idle_w; + } + }); + }); + CONDITION VARIABLES If you are familiar with some event loops you will know that all of them require you to run some blocking "loop", "run" or similar function that @@ -872,8 +939,8 @@ This variable can effectively be used for denial-of-service attacks against local programs (e.g. when setuid), although the impact is - likely small, as the program has to handle connection errors - already- + likely small, as the program has to handle conenction and other + failures anyways. Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over IPv6, but support both and try to use both. @@ -1136,7 +1203,7 @@ EV/EV 400000 224 0.47 0.35 0.27 EV native interface EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal - Perl/Any 100000 452 4.14 0.75 0.99 pure perl implementation + Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation Event/Event 16000 517 32.20 31.80 0.81 Event native interface Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour @@ -1389,7 +1456,7 @@ Perl 5.8 has numerous memleaks that sometimes hit this module and are hard to work around. If you suffer from memleaks, first upgrade to Perl 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other - annoying mamleaks, such as leaking on "map" and "grep" but it is usually + annoying memleaks, such as leaking on "map" and "grep" but it is usually not as pronounced). SEE ALSO