[ViewVC] Diff of: cvs/EV/README

Comparing EV/README (file contents):
Revision 1.7 by root, Sat Nov 3 16:25:49 2007 UTC vs.
Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC

       my $w = EV::timer 2, 0, sub {
          warn "is called after 2s";
       };
-      my $w = EV::timer 2, 1, sub {
+      my $w = EV::timer 2, 2, sub {
-         warn "is called roughly every 2s (repeat = 1)";
+         warn "is called roughly every 2s (repeat = 2)";
       };
       undef $w; # destroy event watcher again
-      my $w = EV::periodic 0, 60, sub {
+      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, $revents) = @_; # all callbacks get the watcher object and event mask
+         my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
          warn "stdin is readable, you entered: ", <STDIN>;
       };
       # 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) = @_;
-         # my $pid = $w->rpid;
          my $status = $w->rstatus;
       };
       # MAINLOOP
-      EV::loop;                   # loop until EV::loop_done is called
+      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
-    (<http://software.schmorp.de/pkg/libev.html>).
+    (<http://software.schmorp.de/pkg/libev.html>). While the documentation
+    below is comprehensive, one might also consult the documentation of
+    libev itself (<http://cvs.schmorp.de/libev/ev.html>) for more subtle
+    details on watcher semantics or some discussion on the available
+    backends, or how to force a specific backend with "LIBEV_FLAGS".
 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
     $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::ev_method
+    $method = EV::method
         Returns an integer describing the backend used by libev
         (EV::METHOD_SELECT or EV::METHOD_EPOLL).
     EV::loop [$flags]
         Begin checking for events and calling callbacks. It returns when a
-        callback calls EV::loop_done.
+        callback calls EV::unloop.
         The $flags argument can be one of the following:
            0                  as above
            EV::LOOP_ONESHOT   block at most once (wait, but do not loop)
            EV::LOOP_NONBLOCK  do not block at all (fetch/handle events but do not wait)
-    EV::loop_done [$how]
+    EV::unloop [$how]
-        When called with no arguments or an argument of 1, makes the
+        When called with no arguments or an argument of EV::UNLOOP_ONE,
-        innermost call to EV::loop return.
+        makes the innermost call to EV::loop return.
-        When called with an agrument of 2, all calls to EV::loop will return
+        When called with an argument of EV::UNLOOP_ALL, all calls to
-        as fast as possible.
+        EV::loop will return as fast as possible.
+    EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
+        This function rolls together an I/O and a timer watcher for a single
+        one-shot event without the need for managing a watcher object.
+        If $fh_or_undef is a filehandle or file descriptor, then $events
+        must be a bitset containing either "EV::READ", "EV::WRITE" or
+        "EV::READ | EV::WRITE", indicating the type of I/O event you want to
+        wait for. If you do not want to wait for some I/O event, specify
+        "undef" for $fh_or_undef and 0 for $events).
+        If timeout is "undef" or negative, then there will be no timeout.
+        Otherwise a EV::timer with this value will be started.
+        When an error occurs or either the timeout or I/O watcher triggers,
+        then the callback will be called with the received event set (in
+        general you can expect it to be a combination of "EV:ERROR",
+        "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
+        EV::once doesn't return anything: the watchers stay active till
+        either of them triggers, then they will be stopped and freed, and
+        the callback invoked.
   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:
         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.
         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.
+        The default priority of any newly-created watcher is 0.
+        Note that the priority semantics have not yet been fleshed out and
+        are subject to almost certain change.
     $w->trigger ($revents)
         Call the callback *now* with the given event mask.
+    $previous_state = $w->keepalive ($bool)
+        Normally, "EV::loop" will return when there are no active watchers
+        (which is a "deadlock" because no progress can be made anymore).
+        This is convinient because it allows you to start your watchers (and
+        your jobs), call "EV::loop" once and when it returns you know that
+        all your jobs are finished (or they forgot to register some watchers
+        for their task :).
+        Sometimes, however, this gets in your way, for example when you the
+        module that calls "EV::loop" (usually the main program) is not the
+        same module as a long-living watcher (for example a DNS client
+        module written by somebody else even). Then you might want any
+        outstanding requests to be handled, but you would not want to keep
+        "EV::loop" from returning just because you happen to have this
+        long-running UDP port watcher.
+        In this case you can clear the keepalive status, which means that
+        even though your watcher is active, it won't keep "EV::loop" from
+        returning.
+        The initial value for keepalive is true (enabled), and you cna
+        change it any time.
+        Example: Register an IO watcher for some UDP socket but do not keep
+        the event loop from running just because of that watcher.
+           my $udp_socket = ...
+           my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
+           $udp_watcher->keepalive (0);
     $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.
     $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
+        Calls the callback after $after seconds (which may be fractional).
-        timer will be restarted (with the $repeat value as $after) after the
+        If $repeat is non-zero, the timer will be restarted (with the
-        callback returns.
+        $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
+        seconds, and then every $repeat seconds. The timer does his best not
-        of callback processing is not taken into account, so the timer will
+        to drift, but it will not invoke the timer more often then once per
-        slowly drift. If that isn't acceptable, look at EV::periodic.
+        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
+        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
     $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 active and non-repeating, it will be stopped.
-        If the timer is in active and repeating, start it.
+        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, $callback
+    $w = EV::periodic $at, $interval, $reschedule_cb, $callback
-    $w = EV::periodic_ns $at, $interval, $callback
+    $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
-        Similar to EV::timer, but the time is given as an absolute point in
+        Similar to EV::timer, but is not based on relative timeouts but on
-        time ($at), plus an optional $interval.
+        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.
-        If the $interval is zero, then the callback will be called at the
+        It has three distinct "modes":
-        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 $interval is nonzero, then the watcher will always be
+        * absolute timer ($interval = $reschedule_cb = 0)
-        scheduled to time out at the next "$at + N * $interval" time.
+            This time simply fires at the wallclock time $at and doesn't
+            repeat. It will not adjust when a time jump occurs, that is, if
+            it is to be run at January 1st 2011 then it will run when the
+            system time reaches or surpasses this time.
-        This can be used to schedule a callback to run at very regular
+        * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
-        intervals, as long as the processing time is less then the interval
+            In this mode the watcher will always be scheduled to time out at
-        (otherwise obviously events will be skipped).
+            the next "$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 $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
+            That doesn't mean there will always be 3600 seconds in between
+            triggers, but only that the the clalback will be called when the
+            system time shows a full hour (UTC).
-        Another way to think about it (for the mathematically inclined) is
+            Another way to think about it (for the mathematically inclined)
-        that EV::periodic will try to run the callback at the next possible
+            is that EV::periodic will try to run the callback in this mode
-        time where "$time = $at (mod $interval)", regardless of any time
+            at the next possible time where "$time = $at (mod $interval)",
-        jumps.
+            regardless of any time jumps.
-        This periodic timer is based on "wallclock time", that is, if the
+        * manual reschedule mode ($reschedule_cb = coderef)
-        clock changes ("ntp", "date -s" etc.), then the timer will
+            In this mode $interval and $at are both being ignored. Instead,
-        nevertheless run at the specified time. This means it will never
+            each time the periodic watcher gets scheduled, the reschedule
-        drift (it might jitter, but it will not drift).
+            callback ($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)
+    $w->set ($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).
               # do nothing unless active
               $dispatcher->{_event_queue_h}
                  or return;
               # make the dispatcher handle any outstanding stuff
+              ... not shown
               # create an IO watcher for each and every socket
               @snmp_watcher = (
                  (map { EV::io $_, EV::READ, sub { } }
                      keys %{ $dispatcher->{_descriptors} }),
+                 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
+                             ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
+                            0, sub { },
               );
-              # 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
+        The callbacks are irrelevant (and are not even being called), the
-        to wake up the process as soon as one of those events occurs (socket
+        only purpose of those watchers is to wake up the process as soon as
-        readable, or timer timed out). The corresponding EV::check watcher
+        one of those events occurs (socket readable, or timer timed out).
-        will then clean up:
+        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
+              ... not shown
            };
         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
+    Threads are not supported by this module in any way. Perl pseudo-threads
-    evil stuff and must die.
+    is evil stuff and must die. As soon as Perl gains real threads I will
+    work on thread support for it.
+FORK
+    Most of the "improved" event delivering mechanisms of modern operating
+    systems have quite a few problems with fork(2) (to put it bluntly: it is
+    not supported and usually destructive). Libev makes it possible to work
+    around this by having a function that recreates the kernel state after
+    fork in the child.
+    On non-win32 platforms, this module requires the pthread_atfork
+    functionality to do this automatically for you. This function is quite
+    buggy on most BSDs, though, so YMMV. The overhead for this is quite
+    negligible, because everything the function currently does is set a flag
+    that is checked only when the event loop gets used the next time, so
+    when you do fork but not use EV, the overhead is minimal.
+    On win32, there is no notion of fork so all this doesn't apply, of
+    course.
 SEE ALSO
-      L<EV::DNS>, L<EV::AnyEvent>.
+      L<EV::DNS>.
 AUTHOR
      Marc Lehmann <schmorp@schmorp.de>
      http://home.schmorp.de/

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Comparing EV/README (file contents): Revision 1.7 by root, Sat Nov 3 16:25:49 2007 UTC vs. Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC

Diff Legend

Comparing EV/README (file contents):
Revision 1.7 by root, Sat Nov 3 16:25:49 2007 UTC vs.
Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC