[ViewVC] Diff of: cvs/EV/README

Comparing EV/README (file contents):
Revision 1.11 by root, Sat Nov 17 01:41:33 2007 UTC vs.
Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC

       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
         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.
+    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:
         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. 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
               # 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>.
 AUTHOR

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Comparing EV/README (file contents): Revision 1.11 by root, Sat Nov 17 01:41:33 2007 UTC vs. Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC

Diff Legend

Comparing EV/README (file contents):
Revision 1.11 by root, Sat Nov 17 01:41:33 2007 UTC vs.
Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC