EV/EV.pm

=head1 NAME

EV - perl interface to libev, a high performance full-featured event loop

=head1 SYNOPSIS

  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, 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
     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 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>).

=cut

package EV;

use strict;

BEGIN {
   our $VERSION = '0.6';
   use XSLoader;
   XSLoader::load "EV", $VERSION;
}

@EV::Io::ISA       =
@EV::Timer::ISA    =
@EV::Periodic::ISA =
@EV::Signal::ISA   =
@EV::Idle::ISA     =
@EV::Prepare::ISA  =
@EV::Check::ISA    =
@EV::Child::ISA    = "EV::Watcher";

=head1 BASIC INTERFACE

=over 4

=item $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.

=item $time = EV::time

Returns the current time in (fractional) seconds since the epoch.

=item $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.

=item $method = EV::ev_method

Returns an integer describing the backend used by libev (EV::METHOD_SELECT
or EV::METHOD_EPOLL).

=item 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)

=item 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.

=back

=head2 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 C<_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 I<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.

=head2 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).

=over 4

=item $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 C<_ns> variants if you need stopped watchers).

=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.

=item $bool = $w->is_active

Returns true if the watcher is active, false otherwise.

=item $current_data = $w->data

=item $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!");

=item $current_cb = $w->cb

=item $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.

=item $current_priority = $w->priority

=item $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.

=item $w->trigger ($revents)

Call the callback *now* with the given event mask.


=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>.

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 C<io_ns> variant doesn't start (activate) the newly created watcher.

=item $w->set ($fileno_or_fh, $eventmask)

Reconfigures the watcher, see the constructor above for details. Can be
called at any time.

=item $current_fh = $w->fh

=item $old_fh = $w->fh ($new_fh)

Returns the previously set filehandle and optionally set a new one.

=item $current_eventmask = $w->events

=item $old_eventmask = $w->events ($new_eventmask)

Returns the previously set event mask and optionally set a new one.


=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,
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 C<$after>
seconds, and then every C<$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 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
any time.

=item $w->again

Similar to the C<start> method, but has special semantics for repeating timers:

If the timer is active and repeating, reset the timeout to occur
C<$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 C<$after> and
C<$repeat>, and then, in the read/write watcher, run the C<again> method
on the timeout.


=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback

=item $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":

=over 4

=item * absolute timer ($interval = $reschedule_cb = 0)

This time simply fires at the wallclock time C<$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.

=item * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)

In this mode the watcher will always be scheduled to time out at the
next C<$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 C<$time = $at (mod $interval)>, regardless of any time
jumps.

=item * manual reschedule mode ($reschedule_cb = coderef)

In this mode $interval and $at are both being ignored. Instead, each time
the periodic watcher gets scheduled, the first callback ($reschedule_cb)
will be called with the watcher as first, and the current time as second
argument.

I<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";
   };

=back

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
any time.

=item $w->again

Simply stops and starts the watcher again.


=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
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 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
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.


=item $w = EV::child $pid, $callback

=item $w = EV::child_ns $pid, $callback

Call the callback when a status change for pid C<$pid> (or any pid
if C<$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 C<rstatus> and C<rpid>
methods on the watcher object.

You can have as many pid watchers per pid as you want.

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
any time.

=item $current_pid = $w->pid

=item $old_pid = $w->pid ($new_pid)

Returns the previously set process id and optionally set a new one.

=item $exit_status = $w->rstatus

Return the exit/wait status (as returned by waitpid, see the waitpid entry
in perlfunc).

=item $pid = $w->rpid

Return the pid of the awaited child (useful when you have installed a
watcher for all pids).


=item $w = EV::idle $callback

=item $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 C<idle_ns> variant doesn't start (activate) the newly created watcher.


=item $w = EV::prepare $callback

=item $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 C<prepare_ns> variant doesn't start (activate) the newly created watcher.


=item $w = EV::check $callback

=item $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 C<check_ns> variant doesn't start (activate) the newly created watcher.

=back

=head1 THREADS

Threads are not supported by this in any way. Perl pseudo-threads is evil
stuff and must die.

=cut

our $DIED = sub {
   warn "EV: error in callback (ignoring): $@";
};

default_loop
   or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_METHODS}?';

1;

=head1 SEE ALSO

  L<EV::DNS>, L<EV::AnyEvent>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.33
Committed:	Fri Nov 9 19:33:51 2007 UTC (16 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.32:	+0 -2 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.20	EV - perl interface to libev, a high performance full-featured event loop
4	root	1.1
5			=head1 SYNOPSIS
6
7	root	1.11	use EV;
8
9	root	1.20	# TIMERS
10	root	1.11
11			my $w = EV::timer 2, 0, sub {
12			warn "is called after 2s";
13			};
14
15			my $w = EV::timer 2, 1, sub {
16			warn "is called roughly every 2s (repeat = 1)";
17			};
18
19			undef $w; # destroy event watcher again
20
21	root	1.30	my $w = EV::periodic 0, 60, 0, sub {
22	root	1.11	warn "is called every minute, on the minute, exactly";
23			};
24
25			# IO
26
27	root	1.20	my $w = EV::io *STDIN, EV::READ, sub {
28	root	1.16	my ($w, $revents) = @_; # all callbacks get the watcher object and event mask
29	root	1.20	warn "stdin is readable, you entered: ", <STDIN>;
30	root	1.11	};
31
32			# SIGNALS
33
34			my $w = EV::signal 'QUIT', sub {
35			warn "sigquit received\n";
36			};
37
38			my $w = EV::signal 3, sub {
39			warn "sigquit received (this is GNU/Linux, right?)\n";
40			};
41	root	1.16
42			# CHILD/PID STATUS CHANGES
43
44			my $w = EV::child 666, sub {
45	root	1.27	my ($w, $revents) = @_;
46			# my $pid = $w->rpid;
47			my $status = $w->rstatus;
48	root	1.16	};
49	root	1.11
50			# MAINLOOP
51	root	1.20	EV::loop; # loop until EV::loop_done is called
52			EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
53			EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
54	root	1.2
55	root	1.1	=head1 DESCRIPTION
56
57	root	1.16	This module provides an interface to libev
58	root	1.20	(L<http://software.schmorp.de/pkg/libev.html>).
59	root	1.1
60			=cut
61
62			package EV;
63
64			use strict;
65
66			BEGIN {
67	root	1.32	our $VERSION = '0.6';
68	root	1.1	use XSLoader;
69			XSLoader::load "EV", $VERSION;
70			}
71
72	root	1.18	@EV::Io::ISA =
73			@EV::Timer::ISA =
74			@EV::Periodic::ISA =
75			@EV::Signal::ISA =
76			@EV::Idle::ISA =
77			@EV::Prepare::ISA =
78			@EV::Check::ISA =
79	root	1.17	@EV::Child::ISA = "EV::Watcher";
80	root	1.15
81	root	1.8	=head1 BASIC INTERFACE
82	root	1.1
83			=over 4
84
85	root	1.8	=item $EV::DIED
86
87			Must contain a reference to a function that is called when a callback
88			throws an exception (with $@ containing thr error). The default prints an
89			informative message and continues.
90
91			If this callback throws an exception it will be silently ignored.
92
93	root	1.20	=item $time = EV::time
94
95			Returns the current time in (fractional) seconds since the epoch.
96
97	root	1.2	=item $time = EV::now
98
99	root	1.20	Returns the time the last event loop iteration has been started. This
100			is the time that (relative) timers are based on, and refering to it is
101			usually faster then calling EV::time.
102
103			=item $method = EV::ev_method
104
105			Returns an integer describing the backend used by libev (EV::METHOD_SELECT
106			or EV::METHOD_EPOLL).
107
108			=item EV::loop [$flags]
109	root	1.2
110	root	1.20	Begin checking for events and calling callbacks. It returns when a
111			callback calls EV::loop_done.
112	root	1.2
113	root	1.20	The $flags argument can be one of the following:
114	root	1.2
115	root	1.20	0 as above
116			EV::LOOP_ONESHOT block at most once (wait, but do not loop)
117			EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
118	root	1.2
119	root	1.20	=item EV::loop_done [$how]
120	root	1.2
121	root	1.20	When called with no arguments or an argument of 1, makes the innermost
122			call to EV::loop return.
123	root	1.2
124	root	1.20	When called with an agrument of 2, all calls to EV::loop will return as
125			fast as possible.
126	root	1.2
127	root	1.20	=back
128
129			=head2 WATCHER
130	root	1.2
131	root	1.20	A watcher is an object that gets created to record your interest in some
132			event. For instance, if you want to wait for STDIN to become readable, you
133			would create an EV::io watcher for that:
134
135			my $watcher = EV::io *STDIN, EV::READ, sub {
136			my ($watcher, $revents) = @_;
137			warn "yeah, STDIN should not be readable without blocking!\n"
138			};
139	root	1.2
140	root	1.20	All watchers can be active (waiting for events) or inactive (paused). Only
141			active watchers will have their callbacks invoked. All callbacks will be
142			called with at least two arguments: the watcher and a bitmask of received
143			events.
144
145			Each watcher type has its associated bit in revents, so you can use the
146			same callback for multiple watchers. The event mask is named after the
147			type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
148			EV::periodic sets EV::PERIODIC and so on, with the exception of IO events
149			(which can set both EV::READ and EV::WRITE bits), and EV::timer (which
150			uses EV::TIMEOUT).
151
152			In the rare case where one wants to create a watcher but not start it at
153			the same time, each constructor has a variant with a trailing C<_ns> in
154			its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
155
156			Please note that a watcher will automatically be stopped when the watcher
157	root	1.23	object is destroyed, so you I<need> to keep the watcher objects returned by
158	root	1.20	the constructors.
159
160	root	1.23	Also, all methods changing some aspect of a watcher (->set, ->priority,
161			->fh and so on) automatically stop and start it again if it is active,
162			which means pending events get lost.
163
164	root	1.20	=head2 WATCHER TYPES
165
166			Now lets move to the existing watcher types and asociated methods.
167
168			The following methods are available for all watchers. Then followes a
169			description of each watcher constructor (EV::io, EV::timer, EV::periodic,
170			EV::signal, EV::child, EV::idle, EV::prepare and EV::check), followed by
171			any type-specific methods (if any).
172
173			=over 4
174	root	1.2
175	root	1.20	=item $w->start
176
177			Starts a watcher if it isn't active already. Does nothing to an already
178			active watcher. By default, all watchers start out in the active state
179			(see the description of the C<_ns> variants if you need stopped watchers).
180
181			=item $w->stop
182	root	1.2
183	root	1.20	Stop a watcher if it is active. Also clear any pending events (events that
184			have been received but that didn't yet result in a callback invocation),
185			regardless of wether the watcher was active or not.
186	root	1.2
187	root	1.20	=item $bool = $w->is_active
188	root	1.2
189	root	1.20	Returns true if the watcher is active, false otherwise.
190
191	root	1.30	=item $current_data = $w->data
192
193			=item $old_data = $w->data ($new_data)
194
195			Queries a freely usable data scalar on the watcher and optionally changes
196			it. This is a way to associate custom data with a watcher:
197
198			my $w = EV::timer 60, 0, sub {
199			warn $_[0]->data;
200			};
201			$w->data ("print me!");
202
203	root	1.20	=item $current_cb = $w->cb
204
205			=item $old_cb = $w->cb ($new_cb)
206
207	root	1.23	Queries the callback on the watcher and optionally changes it. You can do
208			this at any time without the watcher restarting.
209
210			=item $current_priority = $w->priority
211
212			=item $old_priority = $w->priority ($new_priority)
213
214			Queries the priority on the watcher and optionally changes it. Pending
215			watchers with higher priority will be invoked first. The valid range of
216	root	1.24	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
217			-2). If the priority is outside this range it will automatically be
218	root	1.23	normalised to the nearest valid priority.
219
220			The default priority of any newly-created weatcher is 0.
221	root	1.20
222			=item $w->trigger ($revents)
223
224			Call the callback now with the given event mask.
225
226
227			=item $w = EV::io $fileno_or_fh, $eventmask, $callback
228	root	1.2
229	root	1.20	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
230	root	1.7
231	root	1.20	As long as the returned watcher object is alive, call the C<$callback>
232			when the events specified in C<$eventmask>.
233	root	1.2
234	root	1.20	The $eventmask can be one or more of these constants ORed together:
235	root	1.2
236			EV::READ wait until read() wouldn't block anymore
237			EV::WRITE wait until write() wouldn't block anymore
238	root	1.7
239	root	1.20	The C<io_ns> variant doesn't start (activate) the newly created watcher.
240	root	1.2
241	root	1.20	=item $w->set ($fileno_or_fh, $eventmask)
242	root	1.10
243	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be
244			called at any time.
245	root	1.10
246	root	1.20	=item $current_fh = $w->fh
247
248			=item $old_fh = $w->fh ($new_fh)
249
250			Returns the previously set filehandle and optionally set a new one.
251	root	1.10
252	root	1.20	=item $current_eventmask = $w->events
253
254			=item $old_eventmask = $w->events ($new_eventmask)
255	root	1.10
256	root	1.20	Returns the previously set event mask and optionally set a new one.
257	root	1.10
258
259	root	1.20	=item $w = EV::timer $after, $repeat, $callback
260	root	1.2
261	root	1.20	=item $w = EV::timer_ns $after, $repeat, $callback
262	root	1.2
263	root	1.20	Calls the callback after C<$after> seconds. If C<$repeat> is non-zero,
264			the timer will be restarted (with the $repeat value as $after) after the
265			callback returns.
266	root	1.2
267	root	1.20	This means that the callback would be called roughly after C<$after>
268			seconds, and then every C<$repeat> seconds. "Roughly" because the time of
269			callback processing is not taken into account, so the timer will slowly
270			drift. If that isn't acceptable, look at EV::periodic.
271	root	1.2
272	root	1.20	The timer is based on a monotonic clock, that is if somebody is sitting
273			in front of the machine while the timer is running and changes the system
274			clock, the timer will nevertheless run (roughly) the same time.
275	root	1.2
276	root	1.20	The C<timer_ns> variant doesn't start (activate) the newly created watcher.
277
278			=item $w->set ($after, $repeat)
279
280			Reconfigures the watcher, see the constructor above for details. Can be at
281			any time.
282
283			=item $w->again
284
285			Similar to the C<start> method, but has special semantics for repeating timers:
286
287			If the timer is active and repeating, reset the timeout to occur
288			C<$repeat> seconds after now.
289
290			If the timer is active and non-repeating, it will be stopped.
291
292			If the timer is in active and repeating, start it.
293
294			Otherwise do nothing.
295
296			This behaviour is useful when you have a timeout for some IO
297			operation. You create a timer object with the same value for C<$after> and
298			C<$repeat>, and then, in the read/write watcher, run the C<again> method
299			on the timeout.
300
301
302	root	1.30	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
303	root	1.20
304	root	1.30	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
305
306			Similar to EV::timer, but is not based on relative timeouts but on
307			absolute times. Apart from creating "simple" timers that trigger "at" the
308			specified time, it can also be used for non-drifting absolute timers and
309			more complex, cron-like, setups that are not adversely affected by time
310			jumps (i.e. when the system clock is changed by explicit date -s or other
311			means such as ntpd). It is also the most complex watcher type in EV.
312
313			It has three distinct "modes":
314
315			=over 4
316	root	1.2
317	root	1.30	=item * absolute timer ($interval = $reschedule_cb = 0)
318	root	1.2
319	root	1.30	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
320			will not adjust when a time jump occurs, that is, if it is to be run
321			at January 1st 2011 then it will run when the system time reaches or
322			surpasses this time.
323	root	1.2
324	root	1.30	=item * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
325	root	1.2
326	root	1.30	In this mode the watcher will always be scheduled to time out at the
327			next C<$at + N * $interval> time (for some integer N) and then repeat,
328			regardless of any time jumps.
329
330			This can be used to create timers that do not drift with respect to system
331			time:
332
333			my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
334
335			That doesn't mean there will always be 3600 seconds in between triggers,
336			but only that the the clalback will be called when the system time shows a
337			full hour (UTC).
338	root	1.2
339	root	1.7	Another way to think about it (for the mathematically inclined) is that
340	root	1.30	EV::periodic will try to run the callback in this mode at the next
341			possible time where C<$time = $at (mod $interval)>, regardless of any time
342			jumps.
343
344			=item * manual reschedule mode ($reschedule_cb = coderef)
345
346			In this mode $interval and $at are both being ignored. Instead, each time
347			the periodic watcher gets scheduled, the first callback ($reschedule_cb)
348			will be called with the watcher as first, and the current time as second
349			argument.
350
351	root	1.31	I<This callback MUST NOT stop or destroy this or any other periodic
352			watcher, ever>. If you need to stop it, return 1e30 and stop it
353			afterwards.
354	root	1.30
355			It must return the next time to trigger, based on the passed time value
356			(that is, the lowest time value larger than to the second argument). It
357			will usually be called just before the callback will be triggered, but
358			might be called at other times, too.
359
360			This can be used to create very complex timers, such as a timer that
361			triggers on each midnight, local time (actually 24 hours after the last
362			midnight, to keep the example simple. If you know a way to do it correctly
363			in about the same space (without requiring elaborate modules), drop me a
364			note :):
365
366			my $daily = EV::periodic 0, 0, sub {
367			my ($w, $now) = @_;
368
369			use Time::Local ();
370			my (undef, undef, undef, $d, $m, $y) = localtime $now;
371			86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
372			}, sub {
373			print "it's midnight or likely shortly after, now\n";
374			};
375	root	1.7
376	root	1.30	=back
377	root	1.20
378			The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
379	root	1.2
380	root	1.30	=item $w->set ($at, $interval, $reschedule_cb)
381	root	1.11
382	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be at
383			any time.
384
385	root	1.30	=item $w->again
386
387			Simply stops and starts the watcher again.
388
389	root	1.20
390			=item $w = EV::signal $signal, $callback
391
392			=item $w = EV::signal_ns $signal, $callback
393	root	1.11
394			Call the callback when $signal is received (the signal can be specified
395	root	1.20	by number or by name, just as with kill or %SIG).
396	root	1.2
397	root	1.11	EV will grab the signal for the process (the kernel only allows one
398	root	1.20	component to receive a signal at a time) when you start a signal watcher,
399			and removes it again when you stop it. Perl does the same when you
400			add/remove callbacks to %SIG, so watch out.
401
402			You can have as many signal watchers per signal as you want.
403	root	1.2
404	root	1.20	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
405	root	1.2
406	root	1.20	=item $w->set ($signal)
407	root	1.2
408	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be at
409			any time.
410
411	root	1.22	=item $current_signum = $w->signal
412
413			=item $old_signum = $w->signal ($new_signal)
414
415			Returns the previously set signal (always as a number not name) and
416			optionally set a new one.
417
418	root	1.20
419			=item $w = EV::child $pid, $callback
420
421			=item $w = EV::child_ns $pid, $callback
422
423			Call the callback when a status change for pid C<$pid> (or any pid
424			if C<$pid> is 0) has been received. More precisely: when the process
425			receives a SIGCHLD, EV will fetch the outstanding exit/wait status for all
426			changed/zombie children and call the callback.
427
428	root	1.27	You can access both status and pid by using the C<rstatus> and C<rpid>
429			methods on the watcher object.
430	root	1.20
431			You can have as many pid watchers per pid as you want.
432
433			The C<child_ns> variant doesn't start (activate) the newly created watcher.
434
435			=item $w->set ($pid)
436	root	1.1
437	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be at
438			any time.
439	root	1.2
440	root	1.22	=item $current_pid = $w->pid
441
442			=item $old_pid = $w->pid ($new_pid)
443
444			Returns the previously set process id and optionally set a new one.
445
446	root	1.27	=item $exit_status = $w->rstatus
447
448			Return the exit/wait status (as returned by waitpid, see the waitpid entry
449			in perlfunc).
450
451			=item $pid = $w->rpid
452
453			Return the pid of the awaited child (useful when you have installed a
454			watcher for all pids).
455
456	root	1.2
457	root	1.20	=item $w = EV::idle $callback
458	root	1.2
459	root	1.20	=item $w = EV::idle_ns $callback
460	root	1.2
461	root	1.20	Call the callback when there are no pending io, timer/periodic, signal or
462			child events, i.e. when the process is idle.
463	root	1.2
464	root	1.20	The process will not block as long as any idle watchers are active, and
465			they will be called repeatedly until stopped.
466	root	1.2
467	root	1.20	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
468	root	1.2
469
470	root	1.20	=item $w = EV::prepare $callback
471	root	1.1
472	root	1.20	=item $w = EV::prepare_ns $callback
473	root	1.1
474	root	1.20	Call the callback just before the process would block. You can still
475			create/modify any watchers at this point.
476	root	1.1
477	root	1.20	See the EV::check watcher, below, for explanations and an example.
478	root	1.2
479	root	1.20	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
480	root	1.2
481
482	root	1.20	=item $w = EV::check $callback
483	root	1.2
484	root	1.20	=item $w = EV::check_ns $callback
485	root	1.10
486	root	1.20	Call the callback just after the process wakes up again (after it has
487			gathered events), but before any other callbacks have been invoked.
488	root	1.10
489	root	1.20	This is used to integrate other event-based software into the EV
490			mainloop: You register a prepare callback and in there, you create io and
491			timer watchers as required by the other software. Here is a real-world
492			example of integrating Net::SNMP (with some details left out):
493	root	1.10
494	root	1.20	our @snmp_watcher;
495	root	1.2
496	root	1.20	our $snmp_prepare = EV::prepare sub {
497			# do nothing unless active
498			$dispatcher->{_event_queue_h}
499			or return;
500	root	1.2
501	root	1.20	# make the dispatcher handle any outstanding stuff
502	root	1.2
503	root	1.20	# create an IO watcher for each and every socket
504			@snmp_watcher = (
505			(map { EV::io $_, EV::READ, sub { } }
506			keys %{ $dispatcher->{_descriptors} }),
507			);
508	root	1.2
509	root	1.20	# if there are any timeouts, also create a timer
510			push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
511			if $event->[Net::SNMP::Dispatcher::_ACTIVE];
512			};
513	root	1.2
514	root	1.20	The callbacks are irrelevant, the only purpose of those watchers is
515			to wake up the process as soon as one of those events occurs (socket
516			readable, or timer timed out). The corresponding EV::check watcher will then
517			clean up:
518	root	1.2
519	root	1.20	our $snmp_check = EV::check sub {
520			# destroy all watchers
521			@snmp_watcher = ();
522	root	1.2
523	root	1.20	# make the dispatcher handle any new stuff
524			};
525	root	1.2
526	root	1.20	The callbacks of the created watchers will not be called as the watchers
527			are destroyed before this cna happen (remember EV::check gets called
528			first).
529	root	1.2
530	root	1.20	The C<check_ns> variant doesn't start (activate) the newly created watcher.
531	root	1.1
532			=back
533
534	root	1.13	=head1 THREADS
535
536			Threads are not supported by this in any way. Perl pseudo-threads is evil
537	root	1.20	stuff and must die.
538	root	1.13
539	root	1.1	=cut
540
541	root	1.8	our $DIED = sub {
542			warn "EV: error in callback (ignoring): $@";
543			};
544
545	root	1.28	default_loop
546	root	1.26	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_METHODS}?';
547	root	1.1
548			1;
549
550	root	1.3	=head1 SEE ALSO
551
552	root	1.20	L<EV::DNS>, L<EV::AnyEvent>.
553	root	1.3
554	root	1.1	=head1 AUTHOR
555
556			Marc Lehmann <schmorp@schmorp.de>
557			http://home.schmorp.de/
558
559			=cut
560