NAME EV - perl interface to libev, a high performance full-featured event loop SYNOPSIS use EV; # TIMERS my $w = EV::timer 2, 0, sub { warn "is called after 2s"; }; my $w = EV::timer 2, 2, sub { warn "is called roughly every 2s (repeat = 2)"; }; undef $w; # destroy event watcher again my $w = EV::periodic 0, 60, 0, sub { warn "is called every minute, on the minute, exactly"; }; # IO my $w = EV::io *STDIN, EV::READ, sub { my ($w, $revents) = @_; # all callbacks receive the watcher and event mask warn "stdin is readable, you entered: ", ; }; # SIGNALS my $w = EV::signal 'QUIT', sub { warn "sigquit received\n"; }; # CHILD/PID STATUS CHANGES my $w = EV::child 666, sub { my ($w, $revents) = @_; my $status = $w->rstatus; }; # MAINLOOP EV::loop; # loop until EV::unloop is called or all watchers stop EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block DESCRIPTION This module provides an interface to libev (). BASIC INTERFACE $EV::DIED Must contain a reference to a function that is called when a callback throws an exception (with $@ containing thr error). The default prints an informative message and continues. If this callback throws an exception it will be silently ignored. $time = EV::time Returns the current time in (fractional) seconds since the epoch. $time = EV::now Returns the time the last event loop iteration has been started. This is the time that (relative) timers are based on, and refering to it is usually faster then calling EV::time. $method = EV::method Returns an integer describing the backend used by libev (EV::METHOD_SELECT or EV::METHOD_EPOLL). EV::loop [$flags] Begin checking for events and calling callbacks. It returns when a callback calls EV::unloop. The $flags argument can be one of the following: 0 as above EV::LOOP_ONESHOT block at most once (wait, but do not loop) EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) EV::unloop [$how] When called with no arguments or an argument of EV::UNLOOP_ONE, makes the innermost call to EV::loop return. When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as fast as possible. WATCHER A watcher is an object that gets created to record your interest in some event. For instance, if you want to wait for STDIN to become readable, you would create an EV::io watcher for that: my $watcher = EV::io *STDIN, EV::READ, sub { my ($watcher, $revents) = @_; warn "yeah, STDIN should not be readable without blocking!\n" }; All watchers can be active (waiting for events) or inactive (paused). Only active watchers will have their callbacks invoked. All callbacks will be called with at least two arguments: the watcher and a bitmask of received events. Each watcher type has its associated bit in revents, so you can use the same callback for multiple watchers. The event mask is named after the type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, EV::periodic sets EV::PERIODIC and so on, with the exception of IO events (which can set both EV::READ and EV::WRITE bits), and EV::timer (which uses EV::TIMEOUT). In the rare case where one wants to create a watcher but not start it at the same time, each constructor has a variant with a trailing "_ns" in its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. Please note that a watcher will automatically be stopped when the watcher object is destroyed, so you *need* to keep the watcher objects returned by the constructors. Also, all methods changing some aspect of a watcher (->set, ->priority, ->fh and so on) automatically stop and start it again if it is active, which means pending events get lost. WATCHER TYPES Now lets move to the existing watcher types and asociated methods. The following methods are available for all watchers. Then followes a description of each watcher constructor (EV::io, EV::timer, EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and EV::check), followed by any type-specific methods (if any). $w->start Starts a watcher if it isn't active already. Does nothing to an already active watcher. By default, all watchers start out in the active state (see the description of the "_ns" variants if you need stopped watchers). $w->stop Stop a watcher if it is active. Also clear any pending events (events that have been received but that didn't yet result in a callback invocation), regardless of wether the watcher was active or not. $bool = $w->is_active Returns true if the watcher is active, false otherwise. $current_data = $w->data $old_data = $w->data ($new_data) Queries a freely usable data scalar on the watcher and optionally changes it. This is a way to associate custom data with a watcher: my $w = EV::timer 60, 0, sub { warn $_[0]->data; }; $w->data ("print me!"); $current_cb = $w->cb $old_cb = $w->cb ($new_cb) Queries the callback on the watcher and optionally changes it. You can do this at any time without the watcher restarting. $current_priority = $w->priority $old_priority = $w->priority ($new_priority) Queries the priority on the watcher and optionally changes it. Pending watchers with higher priority will be invoked first. The valid range of priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default -2). If the priority is outside this range it will automatically be normalised to the nearest valid priority. The default priority of any newly-created weatcher is 0. $w->trigger ($revents) Call the callback *now* with the given event mask. $w = EV::io $fileno_or_fh, $eventmask, $callback $w = EV::io_ns $fileno_or_fh, $eventmask, $callback As long as the returned watcher object is alive, call the $callback when the events specified in $eventmask. The $eventmask can be one or more of these constants ORed together: EV::READ wait until read() wouldn't block anymore EV::WRITE wait until write() wouldn't block anymore The "io_ns" variant doesn't start (activate) the newly created watcher. $w->set ($fileno_or_fh, $eventmask) Reconfigures the watcher, see the constructor above for details. Can be called at any time. $current_fh = $w->fh $old_fh = $w->fh ($new_fh) Returns the previously set filehandle and optionally set a new one. $current_eventmask = $w->events $old_eventmask = $w->events ($new_eventmask) Returns the previously set event mask and optionally set a new one. $w = EV::timer $after, $repeat, $callback $w = EV::timer_ns $after, $repeat, $callback Calls the callback after $after seconds. If $repeat is non-zero, the timer will be restarted (with the $repeat value as $after) after the callback returns. This means that the callback would be called roughly after $after seconds, and then every $repeat seconds. The timer does his best not to drift, but it will not invoke the timer more often then once per event loop iteration, and might drift in other cases. If that isn't acceptable, look at EV::periodic, which can provide long-term stable timers. The timer is based on a monotonic clock, that is, if somebody is sitting in front of the machine while the timer is running and changes the system clock, the timer will nevertheless run (roughly) the same time. The "timer_ns" variant doesn't start (activate) the newly created watcher. $w->set ($after, $repeat) Reconfigures the watcher, see the constructor above for details. Can be at any time. $w->again Similar to the "start" method, but has special semantics for repeating timers: If the timer is active and non-repeating, it will be stopped. If the timer is active and repeating, reset the timeout to occur $repeat seconds after now. If the timer is inactive and repeating, start it using the repeat value. Otherwise do nothing. This behaviour is useful when you have a timeout for some IO operation. You create a timer object with the same value for $after and $repeat, and then, in the read/write watcher, run the "again" method on the timeout. $w = EV::periodic $at, $interval, $reschedule_cb, $callback $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback Similar to EV::timer, but is not based on relative timeouts but on absolute times. Apart from creating "simple" timers that trigger "at" the specified time, it can also be used for non-drifting absolute timers and more complex, cron-like, setups that are not adversely affected by time jumps (i.e. when the system clock is changed by explicit date -s or other means such as ntpd). It is also the most complex watcher type in EV. It has three distinct "modes": * absolute timer ($interval = $reschedule_cb = 0) This time simply fires at the wallclock time $at and doesn't repeat. It will not adjust when a time jump occurs, that is, if it is to be run at January 1st 2011 then it will run when the system time reaches or surpasses this time. * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) In this mode the watcher will always be scheduled to time out at the next "$at + N * $interval" time (for some integer N) and then repeat, regardless of any time jumps. This can be used to create timers that do not drift with respect to system time: my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" }; That doesn't mean there will always be 3600 seconds in between triggers, but only that the the clalback will be called when the system time shows a full hour (UTC). Another way to think about it (for the mathematically inclined) is that EV::periodic will try to run the callback in this mode at the next possible time where "$time = $at (mod $interval)", regardless of any time jumps. * manual reschedule mode ($reschedule_cb = coderef) In this mode $interval and $at are both being ignored. Instead, each time the periodic watcher gets scheduled, the reschedule callback ($reschedule_cb) will be called with the watcher as first, and the current time as second argument. *This callback MUST NOT stop or destroy this or any other periodic watcher, ever*. If you need to stop it, return 1e30 and stop it afterwards. It must return the next time to trigger, based on the passed time value (that is, the lowest time value larger than to the second argument). It will usually be called just before the callback will be triggered, but might be called at other times, too. This can be used to create very complex timers, such as a timer that triggers on each midnight, local time (actually 24 hours after the last midnight, to keep the example simple. If you know a way to do it correctly in about the same space (without requiring elaborate modules), drop me a note :): my $daily = EV::periodic 0, 0, sub { my ($w, $now) = @_; use Time::Local (); my (undef, undef, undef, $d, $m, $y) = localtime $now; 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y }, sub { print "it's midnight or likely shortly after, now\n"; }; The "periodic_ns" variant doesn't start (activate) the newly created watcher. $w->set ($at, $interval, $reschedule_cb) Reconfigures the watcher, see the constructor above for details. Can be at any time. $w->again Simply stops and starts the watcher again. $w = EV::signal $signal, $callback $w = EV::signal_ns $signal, $callback Call the callback when $signal is received (the signal can be specified by number or by name, just as with kill or %SIG). EV will grab the signal for the process (the kernel only allows one component to receive a signal at a time) when you start a signal watcher, and removes it again when you stop it. Perl does the same when you add/remove callbacks to %SIG, so watch out. You can have as many signal watchers per signal as you want. The "signal_ns" variant doesn't start (activate) the newly created watcher. $w->set ($signal) Reconfigures the watcher, see the constructor above for details. Can be at any time. $current_signum = $w->signal $old_signum = $w->signal ($new_signal) Returns the previously set signal (always as a number not name) and optionally set a new one. $w = EV::child $pid, $callback $w = EV::child_ns $pid, $callback Call the callback when a status change for pid $pid (or any pid if $pid is 0) has been received. More precisely: when the process receives a SIGCHLD, EV will fetch the outstanding exit/wait status for all changed/zombie children and call the callback. You can access both status and pid by using the "rstatus" and "rpid" methods on the watcher object. You can have as many pid watchers per pid as you want. The "child_ns" variant doesn't start (activate) the newly created watcher. $w->set ($pid) Reconfigures the watcher, see the constructor above for details. Can be at any time. $current_pid = $w->pid $old_pid = $w->pid ($new_pid) Returns the previously set process id and optionally set a new one. $exit_status = $w->rstatus Return the exit/wait status (as returned by waitpid, see the waitpid entry in perlfunc). $pid = $w->rpid Return the pid of the awaited child (useful when you have installed a watcher for all pids). $w = EV::idle $callback $w = EV::idle_ns $callback Call the callback when there are no pending io, timer/periodic, signal or child events, i.e. when the process is idle. The process will not block as long as any idle watchers are active, and they will be called repeatedly until stopped. The "idle_ns" variant doesn't start (activate) the newly created watcher. $w = EV::prepare $callback $w = EV::prepare_ns $callback Call the callback just before the process would block. You can still create/modify any watchers at this point. See the EV::check watcher, below, for explanations and an example. The "prepare_ns" variant doesn't start (activate) the newly created watcher. $w = EV::check $callback $w = EV::check_ns $callback Call the callback just after the process wakes up again (after it has gathered events), but before any other callbacks have been invoked. This is used to integrate other event-based software into the EV mainloop: You register a prepare callback and in there, you create io and timer watchers as required by the other software. Here is a real-world example of integrating Net::SNMP (with some details left out): our @snmp_watcher; our $snmp_prepare = EV::prepare sub { # do nothing unless active $dispatcher->{_event_queue_h} or return; # make the dispatcher handle any outstanding stuff # create an IO watcher for each and every socket @snmp_watcher = ( (map { EV::io $_, EV::READ, sub { } } keys %{ $dispatcher->{_descriptors} }), ); # if there are any timeouts, also create a timer push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { } if $event->[Net::SNMP::Dispatcher::_ACTIVE]; }; The callbacks are irrelevant, the only purpose of those watchers is to wake up the process as soon as one of those events occurs (socket readable, or timer timed out). The corresponding EV::check watcher will then clean up: our $snmp_check = EV::check sub { # destroy all watchers @snmp_watcher = (); # make the dispatcher handle any new stuff }; The callbacks of the created watchers will not be called as the watchers are destroyed before this cna happen (remember EV::check gets called first). The "check_ns" variant doesn't start (activate) the newly created watcher. THREADS Threads are not supported by this in any way. Perl pseudo-threads is evil stuff and must die. SEE ALSO L. AUTHOR Marc Lehmann http://home.schmorp.de/