[ViewVC] Diff of: cvs/EV/EV.pm

Comparing EV/EV.pm (file contents):
Revision 1.41 by root, Fri Nov 16 10:42:40 2007 UTC vs.
Revision 1.64 by root, Sat Dec 8 02:55:13 2007 UTC

   my $w = EV::child 666, sub {
      my ($w, $revents) = @_;
      my $status = $w->rstatus;
   };
+  # STAT CHANGES
+  my $w = EV::stat "/etc/passwd", 10, sub {
+     my ($w, $revents) = @_;
+     warn $w->path, " has changed somehow.\n";
+  };
   # 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
 =head1 DESCRIPTION
 This module provides an interface to libev
-(L<http://software.schmorp.de/pkg/libev.html>).
+(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
+below is comprehensive, one might also consult the documentation of libev
+itself (L<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 C<LIBEV_FLAGS>, or just about in any case
+because it has much more detailed information.
 =cut
 package EV;
 use strict;
 BEGIN {
-   our $VERSION = '0.9';
+   our $VERSION = '1.8';
    use XSLoader;
    XSLoader::load "EV", $VERSION;
 }
-@EV::Io::ISA       =
+@EV::IO::ISA       =
 @EV::Timer::ISA    =
 @EV::Periodic::ISA =
 @EV::Signal::ISA   =
+@EV::Child::ISA    =
+@EV::Stat::ISA     =
 @EV::Idle::ISA     =
 @EV::Prepare::ISA  =
 @EV::Check::ISA    =
-@EV::Child::ISA    = "EV::Watcher";
+@EV::Embed::ISA    =
+@EV::Fork::ISA     =
+   "EV::Watcher";
 =head1 BASIC INTERFACE
 =over 4
 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.
-=back
+=item $count = EV::loop_count
+Return the number of times the event loop has polled for new
+events. Sometiems useful as a generation counter.
+=item 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 C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
+must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<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 C<undef> for
+C<$fh_or_undef> and C<0> for C<$events>).
+If timeout is C<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 C<EV:ERROR>, C<EV::READ>,
+C<EV::WRITE> and C<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.
+=back
-=head2 WATCHER
+=head2 WATCHER OBJECTS
 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:
 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
+EV::periodic sets EV::PERIODIC and so on, with the exception of I/O 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 C<_ns> in
 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.
-=head2 WATCHER TYPES
+=head2 COMMON WATCHER METHODS
-Now lets move to the existing watcher types and asociated methods.
+This section lists methods common to all watchers.
-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).
 =over 4
 =item $w->start
 =item $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.
+regardless of whether the watcher was active or not.
 =item $bool = $w->is_active
 Returns true if the watcher is active, false otherwise.
 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.
 =item $w->trigger ($revents)
 Call the callback *now* with the given event mask.
+=item $previous_state = $w->keepalive ($bool)
+Normally, C<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 C<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 C<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 C<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 C<EV::loop> from returning.
+The initial value for keepalive is true (enabled), and you cna change it
+any time.
+Example: Register an I/O 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);
+=back
+=head2 WATCHER TYPES
+Each of the following subsections describes a single watcher type.
+=head3 I/O WATCHERS - is this file descriptor readable or writable?
+=over 4
 =item $w = EV::io $fileno_or_fh, $eventmask, $callback
 =item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
 As long as the returned watcher object is alive, call the C<$callback>
-when the events specified in C<$eventmask>.
+when at least one of events specified in C<$eventmask> occurs.
 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
 =item $old_eventmask = $w->events ($new_eventmask)
 Returns the previously set event mask and optionally set a new one.
+=back
+=head3 TIMER WATCHERS - relative and optionally repeating timeouts
+=over 4
 =item $w = EV::timer $after, $repeat, $callback
 =item $w = EV::timer_ns $after, $repeat, $callback
-Calls the callback after C<$after> seconds. If C<$repeat> is non-zero,
+Calls the callback after C<$after> seconds (which may be fractional). If
-the timer will be restarted (with the $repeat value as $after) after the
+C<$repeat> is non-zero, the timer will be restarted (with the $repeat
-callback returns.
+value as $after) after the callback returns.
 This means that the callback would be called roughly after C<$after>
 seconds, and then every C<$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,
 The C<timer_ns> variant doesn't start (activate) the newly created watcher.
 =item $w->set ($after, $repeat)
-Reconfigures the watcher, see the constructor above for details. Can be at
+Reconfigures the watcher, see the constructor above for details. Can be called at
 any time.
 =item $w->again
 Similar to the C<start> method, but has special semantics for repeating timers:
 This behaviour is useful when you have a timeout for some IO
 operation. You create a timer object with the same value for C<$after> and
 C<$repeat>, and then, in the read/write watcher, run the C<again> method
 on the timeout.
+=back
+=head3 PERIODIC WATCHERS - to cron or not to cron?
+=over 4
 =item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
 =item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
 The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
 =item $w->set ($at, $interval, $reschedule_cb)
-Reconfigures the watcher, see the constructor above for details. Can be at
+Reconfigures the watcher, see the constructor above for details. Can be called at
 any time.
 =item $w->again
 Simply stops and starts the watcher again.
+=back
+=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
+=over 4
 =item $w = EV::signal $signal, $callback
 =item $w = EV::signal_ns $signal, $callback
-Call the callback when $signal is received (the signal can be specified
+Call the callback when $signal is received (the signal can be specified by
-by number or by name, just as with kill or %SIG).
+number or by name, just as with C<kill> or C<%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.
+add/remove callbacks to C<%SIG>, so watch out.
 You can have as many signal watchers per signal as you want.
 The C<signal_ns> variant doesn't start (activate) the newly created watcher.
 =item $w->set ($signal)
-Reconfigures the watcher, see the constructor above for details. Can be at
+Reconfigures the watcher, see the constructor above for details. Can be
-any time.
+called at any time.
 =item $current_signum = $w->signal
 =item $old_signum = $w->signal ($new_signal)
 Returns the previously set signal (always as a number not name) and
 optionally set a new one.
+=back
+=head3 CHILD WATCHERS - watch out for process status changes
+=over 4
 =item $w = EV::child $pid, $callback
 =item $w = EV::child_ns $pid, $callback
-Call the callback when a status change for pid C<$pid> (or any pid
+Call the callback when a status change for pid C<$pid> (or any pid if
-if C<$pid> is 0) has been received. More precisely: when the process
+C<$pid> is 0) has been received. More precisely: when the process receives
-receives a SIGCHLD, EV will fetch the outstanding exit/wait status for all
+a C<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 C<rstatus> and C<rpid>
+It is valid (and fully supported) to install a child watcher after a child
-methods on the watcher object.
+has exited but before the event loop has started its next iteration (for
+example, first you C<fork>, then the new child process might exit, and
+only then do you install a child watcher in the parent for the new pid).
+You can access both exit (or tracing) status and pid by using the
+C<rstatus> and C<rpid> methods on the watcher object.
-You can have as many pid watchers per pid as you want.
+You can have as many pid watchers per pid as you want, they will all be
+called.
 The C<child_ns> variant doesn't start (activate) the newly created watcher.
 =item $w->set ($pid)
-Reconfigures the watcher, see the constructor above for details. Can be at
+Reconfigures the watcher, see the constructor above for details. Can be called at
 any time.
 =item $current_pid = $w->pid
 =item $old_pid = $w->pid ($new_pid)
 =item $pid = $w->rpid
 Return the pid of the awaited child (useful when you have installed a
 watcher for all pids).
+=back
+=head3 STAT WATCHERS - did the file attributes just change?
+=over 4
+=item $w = EV::stat $path, $interval, $callback
+=item $w = EV::stat_ns $path, $interval, $callback
+Call the callback when a file status change has been detected on
+C<$path>. The C<$path> does not need to exist, changing from "path exists"
+to "path does not exist" is a status change like any other.
+The C<$interval> is a recommended polling interval for systems where
+OS-supported change notifications don't exist or are not supported. If
+you use C<0> then an unspecified default is used (which is highly
+recommended!), which is to be expected to be around five seconds usually.
+This watcher type is not meant for massive numbers of stat watchers,
+as even with OS-supported change notifications, this can be
+resource-intensive.
+The C<stat_ns> variant doesn't start (activate) the newly created watcher.
+=item ... = $w->stat
+This call is very similar to the perl C<stat> built-in: It stats (using
+C<lstat>) the path specified in the watcher and sets perls stat cache (as
+well as EV's idea of the current stat values) to the values found.
+In scalar context, a boolean is return indicating success or failure of
+the stat. In list context, the same 13-value list as with stat is returned
+(except that the blksize and blocks fields are not reliable).
+In the case of an error, errno is set to C<ENOENT> (regardless of the
+actual error value) and the C<nlink> value is forced to zero (if the stat
+was successful then nlink is guaranteed to be non-zero).
+See also the next two entries for more info.
+=item ... = $w->attr
+Just like C<< $w->stat >>, but without the initial stat'ing: this returns
+the values most recently detected by EV. See the next entry for more info.
+=item ... = $w->prev
+Just like C<< $w->stat >>, but without the initial stat'ing: this returns
+the previous set of values, before the change.
+That is, when the watcher callback is invoked, C<< $w->prev >> will be set
+to the values found I<before> a change was detected, while C<< $w->attr >>
+returns the values found leading to the change detection. The difference (if any)
+between C<prev> and C<attr> is what triggered the callback.
+If you did something to the filesystem object and do not want to trigger
+yet another change, you can call C<stat> to update EV's idea of what the
+current attributes are.
+=item $w->set ($path, $interval)
+Reconfigures the watcher, see the constructor above for details. Can be
+called at any time.
+=item $current_path = $w->path
+=item $old_path = $w->path ($new_path)
+Returns the previously set path and optionally set a new one.
+=item $current_interval = $w->interval
+=item $old_interval = $w->interval ($new_interval)
+Returns the previously set interval and optionally set a new one. Can be
+used to query the actual interval used.
+=back
+=head3 IDLE WATCHERS - when you've got nothing better to do...
+=over 4
 =item $w = EV::idle $callback
 =item $w = EV::idle_ns $callback
-Call the callback when there are no pending io, timer/periodic, signal or
+Call the callback when there are no other pending watchers of the same or
-child events, i.e. when the process is idle.
+higher priority (excluding check, prepare and other idle watchers of the
+same or lower priority, of course). They are called idle watchers because
+when the watcher is the highest priority pending event in the process, the
+process is considered to be idle at that priority.
+If you want a watcher that is only ever called when I<no> other events are
+outstanding you have to set the priority to C<EV::MINPRI>.
 The process will not block as long as any idle watchers are active, and
 they will be called repeatedly until stopped.
+For example, if you have idle watchers at priority C<0> and C<1>, and
+an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
+and the I/O watcher will always run when ready. Only when the idle watcher
+at priority C<1> is stopped and the I/O watcher at priority C<0> is not
+pending with the C<0>-priority idle watcher be invoked.
 The C<idle_ns> variant doesn't start (activate) the newly created watcher.
+=back
+=head3 PREPARE WATCHERS - customise your event loop!
+=over 4
 =item $w = EV::prepare $callback
 =item $w = EV::prepare_ns $callback
 See the EV::check watcher, below, for explanations and an example.
 The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
+=back
+=head3 CHECK WATCHERS - customise your event loop even more!
+=over 4
 =item $w = EV::check $callback
 =item $w = EV::check_ns $callback
       # 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
+      # create an I/O 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 will then
+one of those events occurs (socket readable, or timer timed out). The
-clean up:
+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 C<check_ns> variant doesn't start (activate) the newly created watcher.
 =back
+=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
+Fork watchers are called when a C<fork ()> was detected. The invocation
+is done before the event loop blocks next and before C<check> watchers
+are being called, and only in the child after the fork.
+=over 4
+=item $w = EV::fork $callback
+=item $w = EV::fork_ns $callback
+Call the callback before the event loop is resumed in the child process
+after a fork.
+The C<fork_ns> variant doesn't start (activate) the newly created watcher.
+=back
+=head1 PERL SIGNALS
+While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
+with EV is as the same as any other C library: Perl-signals will only be
+handled when Perl runs, which means your signal handler might be invoked
+only the next time an event callback is invoked.
+The solution is to use EV signal watchers (see C<EV::signal>), which will
+ensure proper operations with regards to other event watchers.
+If you cannot do this for whatever reason, you can also force a watcher
+to be called on every event loop iteration by installing a C<EV::check>
+watcher:
+   my $async_check = EV::check sub { };
+This ensures that perl shortly gets into control for a short time, and
+also ensures slower overall operation.
 =head1 THREADS
-Threads are not supported by this in any way. Perl pseudo-threads is evil
+Threads are not supported by this module in any way. Perl pseudo-threads
-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.
+=head1 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.
 =cut
 our $DIED = sub {
    warn "EV: error in callback (ignoring): $@";
 1;
 =head1 SEE ALSO
-  L<EV::DNS>.
+L<EV::ADNS> (asynchronous dns), L<Glib::EV> (makes Glib/Gtk2 use EV as
+event loop), L<Coro::EV> (efficient coroutines with EV).
 =head1 AUTHOR
  Marc Lehmann <schmorp@schmorp.de>
  http://home.schmorp.de/

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Comparing EV/EV.pm (file contents): Revision 1.41 by root, Fri Nov 16 10:42:40 2007 UTC vs. Revision 1.64 by root, Sat Dec 8 02:55:13 2007 UTC

Diff Legend

Comparing EV/EV.pm (file contents):
Revision 1.41 by root, Fri Nov 16 10:42:40 2007 UTC vs.
Revision 1.64 by root, Sat Dec 8 02:55:13 2007 UTC