--- cvsroot/EV/README 2007/10/28 06:40:46 1.3 +++ cvsroot/EV/README 2007/11/01 17:32:39 1.6 @@ -1,56 +1,59 @@ NAME - EV - perl interface to libevent, monkey.org/~provos/libevent/ + EV - perl interface to libev, a high performance full-featured event + loop SYNOPSIS - use EV; - - # TIMER - - my $w = EV::timer 2, 0, sub { - warn "is called after 2s"; - }; - - my $w = EV::timer 2, 1, sub { - warn "is called roughly every 2s (repeat = 1)"; - }; - - undef $w; # destroy event watcher again - - # IO - - my $w = EV::timer_abs 0, 60, sub { - warn "is called every minute, on the minute, exactly"; - }; - - my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { - my ($w, $events) = @_; # all callbacks get the watcher object and event mask - if ($events & EV::TIMEOUT) { - warn "nothign received on stdin for 10 seconds, retrying"; - } else { - warn "stdin is readable, you entered: ", ; - } - }; - $w->timeout (10); - - # MAINLOOP - EV::dispatch; # loop as long as watchers are active - EV::loop; # the same thing - EV::loop EV::LOOP_ONCE; - EV::loop EV::LOOP_ONSHOT; + use EV; + + # TIMERS + + my $w = EV::timer 2, 0, sub { + warn "is called after 2s"; + }; + + my $w = EV::timer 2, 1, sub { + warn "is called roughly every 2s (repeat = 1)"; + }; + + undef $w; # destroy event watcher again + + my $w = EV::periodic 0, 60, sub { + warn "is called every minute, on the minute, exactly"; + }; + + # IO + + my $w = EV::io *STDIN, EV::READ, sub { + my ($w, $revents) = @_; # all callbacks get the watcher object and event mask + warn "stdin is readable, you entered: ", ; + }; + + # SIGNALS + + my $w = EV::signal 'QUIT', sub { + warn "sigquit received\n"; + }; + + my $w = EV::signal 3, sub { + warn "sigquit received (this is GNU/Linux, right?)\n"; + }; + + # CHILD/PID STATUS CHANGES + + my $w = EV::child 666, sub { + my ($w, $revents, $status) = @_; + }; + + # MAINLOOP + EV::loop; # loop until EV::loop_done is called + 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 libevent - (). You probably should acquaint - yourself with its documentation and source code to be able to use this - module fully. - - Please note thta this module disables the libevent EPOLL method by - default, see BUGS, below, if you need to enable it. + This module provides an interface to libev + (). BASIC INTERFACE - $EV::NPRI - How many priority levels are available. - $EV::DIED Must contain a reference to a function that is called when a callback throws an exception (with $@ containing thr error). The @@ -58,140 +61,312 @@ 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 in (fractional) seconds since the epoch. + 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. + + $method = EV::ev_method + Returns an integer describing the backend used by libev + (EV::METHOD_SELECT or EV::METHOD_EPOLL). + + EV::loop [$flags] + Begin checking for events and calling callbacks. It returns when a + callback calls EV::loop_done. + + The $flags argument can be one of the following: + + 0 as above + EV::LOOP_ONESHOT block at most once (wait, but do not loop) + EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) + + EV::loop_done [$how] + When called with no arguments or an argument of 1, makes the + innermost call to EV::loop return. + + When called with an agrument of 2, 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 returned, so you *need* to keep the watcher objects + returned by the constructors. + + 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). - $version = EV::version - $method = EV::method - Return version string and event polling method used. - - EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT - EV::loopexit $after - Exit any active loop or dispatch after $after seconds or immediately - if $after is missing or zero. - - EV::dispatch - Same as "EV::loop 0". - - EV::event $callback - Creates a new event watcher waiting for nothing, calling the given - callback. + $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). - my $w = EV::io $fileno_or_fh, $eventmask, $callback - my $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 happen. Initially, the - timeout is disabled. + $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_cb = $w->cb + $old_cb = $w->cb ($new_cb) + Queries the callback on the watcher and optionally changes it. You + cna do this at any time. - Youc an additionall set a timeout to occur on the watcher, but note - that this timeout will not be reset when you get an I/O event in the - EV::PERSIST case, and reaching a timeout will always stop the - watcher even in the EV::PERSIST case. + $w->trigger ($revents) + Call the callback *now* with the given event mask. - If you want a timeout to occur only after a specific time of - inactivity, set a repeating timeout and do NOT use EV::PERSIST. + $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. - Eventmask can be one or more of these constants ORed together: + 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 - EV::PERSIST stay active after a (non-timeout) event occured - The "io_ns" variant doesn't add/start the newly created watcher. + 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. "Roughly" because the time + of callback processing is not taken into account, so the timer will + slowly drift. If that isn't acceptable, look at EV::periodic. + + 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. - my $w = EV::timer $after, $repeat, $callback - my $w = EV::timer_ns $after, $repeat, $callback - Calls the callback after $after seconds. If $repeat is true, the - timer will be restarted after the callback returns. This means that - the callback would be called roughly every $after seconds, prolonged - by the time the callback takes. + $w->set ($after, $repeat) + Reconfigures the watcher, see the constructor above for details. Can + be at any time. - The "timer_ns" variant doesn't add/start the newly created watcher. + $w->again + Similar to the "start" method, but has special semantics for + repeating timers: - my $w = EV::timer_abs $at, $interval, $callback - my $w = EV::timer_abs_ns $at, $interval, $callback + If the timer is active and repeating, reset the timeout to occur + $repeat seconds after now. + + If the timer is active and non-repeating, it will be stopped. + + If the timer is in active and repeating, start it. + + 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, $callback + $w = EV::periodic_ns $at, $interval, $callback Similar to EV::timer, but the time is given as an absolute point in time ($at), plus an optional $interval. If the $interval is zero, then the callback will be called at the - time $at if that is in the future, or as soon as possible if its in - the past. It will not automatically repeat. + time $at if that is in the future, or as soon as possible if it is + in the past. It will not automatically repeat. If the $interval is nonzero, then the watcher will always be - scheduled to time out at the next "$at + integer * $interval" time. + scheduled to time out at the next "$at + N * $interval" time. This can be used to schedule a callback to run at very regular intervals, as long as the processing time is less then the interval (otherwise obviously events will be skipped). Another way to think about it (for the mathematically inclined) is - that "timer_abs" will try to tun the callback at the next possible + that EV::periodic will try to run the callback at the next possible time where "$time = $at (mod $interval)", regardless of any time jumps. - The "timer_abs_ns" variant doesn't add/start the newly created + This periodic timer is based on "wallclock time", that is, if the + clock changes ("ntp", "date -s" etc.), then the timer will + nevertheless run at the specified time. This means it will never + drift (it might jitter, but it will not drift). + + The "periodic_ns" variant doesn't start (activate) the newly created watcher. - my $w = EV::signal $signum, $callback - my $w = EV::signal_ns $signum, $callback - Call the callback when signal $signum is received. + $w->set ($at, $interval) + Reconfigures the watcher, see the constructor above for details. Can + be at any time. + + $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. - The "signal_ns" variant doesn't add/start the newly created watcher. + You can have as many signal watchers per signal as you want. -THE EV::Event CLASS - All EV functions creating an event watcher (designated by "my $w =" - above) support the following methods on the returned watcher object: + The "signal_ns" variant doesn't start (activate) the newly created + watcher. - $w->add ($timeout) - Stops and (re-)starts the event watcher, setting the optional - timeout to the given value, or clearing the timeout if none is - given. + $w->set ($signal) + Reconfigures the watcher, see the constructor above for details. Can + be at any time. + + $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. + + Unlike all other callbacks, this callback will be called with an + additional third argument which is the exit status. See the + "waitpid" function for details. - $w->start - Stops and (re-)starts the event watcher without touching the - timeout. + You can have as many pid watchers per pid as you want. - $w->del - $w->stop - Stop the event watcher if it was started. + The "child_ns" variant doesn't start (activate) the newly created + watcher. - $current_callback = $w->cb - $old_callback = $w->cb ($new_callback) - Return the previously set callback and optionally set a new one. + $w->set ($pid) + Reconfigures the watcher, see the constructor above for details. Can + be at any time. + + $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. - $current_fh = $w->fh - $old_fh = $w->fh ($new_fh) - Returns the previously set filehandle and optionally set a new one. + The process will not block as long as any idle watchers are active, + and they will be called repeatedly until stopped. - $current_eventmask = $w->events - $old_eventmask = $w->events ($new_eventmask) - Returns the previously set event mask and optionally set a new one. + 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. - $w->timeout ($after, $repeat) - Resets the timeout (see "EV::timer" for details). + See the EV::check watcher, below, for explanations and an example. - $w->timeout_abs ($at, $interval) - Resets the timeout (see "EV::timer_abs" for details). + The "prepare_ns" variant doesn't start (activate) the newly created + watcher. - $w->priority_set ($priority) - Set the priority of the watcher to $priority (0 <= $priority < - $EV::NPRI). - -BUGS - Lots. Libevent itself isn't well tested and rather buggy, and this - module is quite new at the moment. - - Please note that the epoll method is not, in general, reliable in - programs that use fork (even if no libveent calls are being made in the - forked process). If your program behaves erratically, try setting the - environment variable "EVENT_NOEPOLL" first when running the program. + $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. - In general, if you fork, then you can only use the EV module in one of - the children. +THREADS + Threads are not supported by this in any way. Perl pseudo-threads is + evil stuff and must die. SEE ALSO - L, L, L, L. - L. + L, L. AUTHOR Marc Lehmann