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, 2, sub {
     warn "is called roughly every 2s (repeat = 2)";
  };
  
  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 receive the watcher and event mask
     warn "stdin is readable, you entered: ", <STDIN>;
  };
  
  # SIGNALS
  
  my $w = EV::signal 'QUIT', sub {
     warn "sigquit received\n";
  };
  
  # CHILD/PID STATUS CHANGES

  my $w = EV::child 666, sub {
     my ($w, $revents) = @_;
     my $status = $w->rstatus;
  };
  
  # 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>).

=cut

package EV;

use strict;

BEGIN {
   our $VERSION = '1.1';
   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::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::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)

=item EV::unloop [$how]

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.

=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. 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,
look at EV::periodic, which can provide long-term stable timers.

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 non-repeating, it will be stopped.

If the timer is active and repeating, reset the timeout to occur
C<$repeat> seconds after now.

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 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 $at are both being ignored. Instead, each
time the periodic watcher gets scheduled, the reschedule callback
($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>.

=head1 AUTHOR

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

=cut

Revision:	1.43
Committed:	Wed Nov 21 05:09:38 2007 UTC (16 years, 5 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_1
Changes since 1.42:	+1 -1 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	root	1.35	my $w = EV::timer 2, 2, sub {
16			warn "is called roughly every 2s (repeat = 2)";
17	root	1.11	};
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 $w = EV::io *STDIN, EV::READ, sub {
28	root	1.35	my ($w, $revents) = @_; # all callbacks receive the watcher 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	root	1.16	# CHILD/PID STATUS CHANGES
39
40			my $w = EV::child 666, sub {
41	root	1.27	my ($w, $revents) = @_;
42			my $status = $w->rstatus;
43	root	1.16	};
44	root	1.11
45			# MAINLOOP
46	root	1.39	EV::loop; # loop until EV::unloop is called or all watchers stop
47	root	1.20	EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
48			EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
49	root	1.2
50	root	1.1	=head1 DESCRIPTION
51
52	root	1.16	This module provides an interface to libev
53	root	1.20	(L<http://software.schmorp.de/pkg/libev.html>).
54	root	1.1
55			=cut
56
57			package EV;
58
59			use strict;
60
61			BEGIN {
62	root	1.43	our $VERSION = '1.1';
63	root	1.1	use XSLoader;
64			XSLoader::load "EV", $VERSION;
65			}
66
67	root	1.18	@EV::Io::ISA =
68			@EV::Timer::ISA =
69			@EV::Periodic::ISA =
70			@EV::Signal::ISA =
71			@EV::Idle::ISA =
72			@EV::Prepare::ISA =
73			@EV::Check::ISA =
74	root	1.17	@EV::Child::ISA = "EV::Watcher";
75	root	1.15
76	root	1.8	=head1 BASIC INTERFACE
77	root	1.1
78			=over 4
79
80	root	1.8	=item $EV::DIED
81
82			Must contain a reference to a function that is called when a callback
83			throws an exception (with $@ containing thr error). The default prints an
84			informative message and continues.
85
86			If this callback throws an exception it will be silently ignored.
87
88	root	1.20	=item $time = EV::time
89
90			Returns the current time in (fractional) seconds since the epoch.
91
92	root	1.2	=item $time = EV::now
93
94	root	1.20	Returns the time the last event loop iteration has been started. This
95			is the time that (relative) timers are based on, and refering to it is
96			usually faster then calling EV::time.
97
98	root	1.41	=item $method = EV::method
99	root	1.20
100			Returns an integer describing the backend used by libev (EV::METHOD_SELECT
101			or EV::METHOD_EPOLL).
102
103			=item EV::loop [$flags]
104	root	1.2
105	root	1.20	Begin checking for events and calling callbacks. It returns when a
106	root	1.39	callback calls EV::unloop.
107	root	1.2
108	root	1.20	The $flags argument can be one of the following:
109	root	1.2
110	root	1.20	0 as above
111			EV::LOOP_ONESHOT block at most once (wait, but do not loop)
112			EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
113	root	1.2
114	root	1.39	=item EV::unloop [$how]
115	root	1.2
116	root	1.39	When called with no arguments or an argument of EV::UNLOOP_ONE, makes the
117			innermost call to EV::loop return.
118	root	1.2
119	root	1.39	When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as
120	root	1.20	fast as possible.
121	root	1.2
122	root	1.20	=back
123
124			=head2 WATCHER
125	root	1.2
126	root	1.20	A watcher is an object that gets created to record your interest in some
127			event. For instance, if you want to wait for STDIN to become readable, you
128			would create an EV::io watcher for that:
129
130			my $watcher = EV::io *STDIN, EV::READ, sub {
131			my ($watcher, $revents) = @_;
132			warn "yeah, STDIN should not be readable without blocking!\n"
133			};
134	root	1.2
135	root	1.20	All watchers can be active (waiting for events) or inactive (paused). Only
136			active watchers will have their callbacks invoked. All callbacks will be
137			called with at least two arguments: the watcher and a bitmask of received
138			events.
139
140			Each watcher type has its associated bit in revents, so you can use the
141			same callback for multiple watchers. The event mask is named after the
142			type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
143			EV::periodic sets EV::PERIODIC and so on, with the exception of IO events
144			(which can set both EV::READ and EV::WRITE bits), and EV::timer (which
145			uses EV::TIMEOUT).
146
147			In the rare case where one wants to create a watcher but not start it at
148			the same time, each constructor has a variant with a trailing C<_ns> in
149			its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
150
151			Please note that a watcher will automatically be stopped when the watcher
152	root	1.23	object is destroyed, so you I<need> to keep the watcher objects returned by
153	root	1.20	the constructors.
154
155	root	1.23	Also, all methods changing some aspect of a watcher (->set, ->priority,
156			->fh and so on) automatically stop and start it again if it is active,
157			which means pending events get lost.
158
159	root	1.20	=head2 WATCHER TYPES
160
161			Now lets move to the existing watcher types and asociated methods.
162
163			The following methods are available for all watchers. Then followes a
164			description of each watcher constructor (EV::io, EV::timer, EV::periodic,
165			EV::signal, EV::child, EV::idle, EV::prepare and EV::check), followed by
166			any type-specific methods (if any).
167
168			=over 4
169	root	1.2
170	root	1.20	=item $w->start
171
172			Starts a watcher if it isn't active already. Does nothing to an already
173			active watcher. By default, all watchers start out in the active state
174			(see the description of the C<_ns> variants if you need stopped watchers).
175
176			=item $w->stop
177	root	1.2
178	root	1.20	Stop a watcher if it is active. Also clear any pending events (events that
179			have been received but that didn't yet result in a callback invocation),
180			regardless of wether the watcher was active or not.
181	root	1.2
182	root	1.20	=item $bool = $w->is_active
183	root	1.2
184	root	1.20	Returns true if the watcher is active, false otherwise.
185
186	root	1.30	=item $current_data = $w->data
187
188			=item $old_data = $w->data ($new_data)
189
190			Queries a freely usable data scalar on the watcher and optionally changes
191			it. This is a way to associate custom data with a watcher:
192
193			my $w = EV::timer 60, 0, sub {
194			warn $_[0]->data;
195			};
196			$w->data ("print me!");
197
198	root	1.20	=item $current_cb = $w->cb
199
200			=item $old_cb = $w->cb ($new_cb)
201
202	root	1.23	Queries the callback on the watcher and optionally changes it. You can do
203			this at any time without the watcher restarting.
204
205			=item $current_priority = $w->priority
206
207			=item $old_priority = $w->priority ($new_priority)
208
209			Queries the priority on the watcher and optionally changes it. Pending
210			watchers with higher priority will be invoked first. The valid range of
211	root	1.24	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
212			-2). If the priority is outside this range it will automatically be
213	root	1.23	normalised to the nearest valid priority.
214
215			The default priority of any newly-created weatcher is 0.
216	root	1.20
217			=item $w->trigger ($revents)
218
219			Call the callback now with the given event mask.
220
221
222			=item $w = EV::io $fileno_or_fh, $eventmask, $callback
223	root	1.2
224	root	1.20	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
225	root	1.7
226	root	1.20	As long as the returned watcher object is alive, call the C<$callback>
227			when the events specified in C<$eventmask>.
228	root	1.2
229	root	1.20	The $eventmask can be one or more of these constants ORed together:
230	root	1.2
231			EV::READ wait until read() wouldn't block anymore
232			EV::WRITE wait until write() wouldn't block anymore
233	root	1.7
234	root	1.20	The C<io_ns> variant doesn't start (activate) the newly created watcher.
235	root	1.2
236	root	1.20	=item $w->set ($fileno_or_fh, $eventmask)
237	root	1.10
238	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be
239			called at any time.
240	root	1.10
241	root	1.20	=item $current_fh = $w->fh
242
243			=item $old_fh = $w->fh ($new_fh)
244
245			Returns the previously set filehandle and optionally set a new one.
246	root	1.10
247	root	1.20	=item $current_eventmask = $w->events
248
249			=item $old_eventmask = $w->events ($new_eventmask)
250	root	1.10
251	root	1.20	Returns the previously set event mask and optionally set a new one.
252	root	1.10
253
254	root	1.20	=item $w = EV::timer $after, $repeat, $callback
255	root	1.2
256	root	1.20	=item $w = EV::timer_ns $after, $repeat, $callback
257	root	1.2
258	root	1.20	Calls the callback after C<$after> seconds. If C<$repeat> is non-zero,
259			the timer will be restarted (with the $repeat value as $after) after the
260			callback returns.
261	root	1.2
262	root	1.20	This means that the callback would be called roughly after C<$after>
263	root	1.39	seconds, and then every C<$repeat> seconds. The timer does his best not
264			to drift, but it will not invoke the timer more often then once per event
265			loop iteration, and might drift in other cases. If that isn't acceptable,
266			look at EV::periodic, which can provide long-term stable timers.
267	root	1.2
268	root	1.39	The timer is based on a monotonic clock, that is, if somebody is sitting
269	root	1.20	in front of the machine while the timer is running and changes the system
270			clock, the timer will nevertheless run (roughly) the same time.
271	root	1.2
272	root	1.20	The C<timer_ns> variant doesn't start (activate) the newly created watcher.
273
274			=item $w->set ($after, $repeat)
275
276			Reconfigures the watcher, see the constructor above for details. Can be at
277			any time.
278
279			=item $w->again
280
281			Similar to the C<start> method, but has special semantics for repeating timers:
282
283	root	1.39	If the timer is active and non-repeating, it will be stopped.
284
285	root	1.20	If the timer is active and repeating, reset the timeout to occur
286			C<$repeat> seconds after now.
287
288	root	1.39	If the timer is inactive and repeating, start it using the repeat value.
289	root	1.20
290			Otherwise do nothing.
291
292			This behaviour is useful when you have a timeout for some IO
293			operation. You create a timer object with the same value for C<$after> and
294			C<$repeat>, and then, in the read/write watcher, run the C<again> method
295			on the timeout.
296
297
298	root	1.30	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
299	root	1.20
300	root	1.30	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
301
302			Similar to EV::timer, but is not based on relative timeouts but on
303			absolute times. Apart from creating "simple" timers that trigger "at" the
304			specified time, it can also be used for non-drifting absolute timers and
305			more complex, cron-like, setups that are not adversely affected by time
306			jumps (i.e. when the system clock is changed by explicit date -s or other
307			means such as ntpd). It is also the most complex watcher type in EV.
308
309			It has three distinct "modes":
310
311			=over 4
312	root	1.2
313	root	1.30	=item * absolute timer ($interval = $reschedule_cb = 0)
314	root	1.2
315	root	1.30	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
316			will not adjust when a time jump occurs, that is, if it is to be run
317			at January 1st 2011 then it will run when the system time reaches or
318			surpasses this time.
319	root	1.2
320	root	1.30	=item * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
321	root	1.2
322	root	1.30	In this mode the watcher will always be scheduled to time out at the
323			next C<$at + N * $interval> time (for some integer N) and then repeat,
324			regardless of any time jumps.
325
326			This can be used to create timers that do not drift with respect to system
327			time:
328
329			my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
330
331			That doesn't mean there will always be 3600 seconds in between triggers,
332			but only that the the clalback will be called when the system time shows a
333			full hour (UTC).
334	root	1.2
335	root	1.7	Another way to think about it (for the mathematically inclined) is that
336	root	1.30	EV::periodic will try to run the callback in this mode at the next
337			possible time where C<$time = $at (mod $interval)>, regardless of any time
338			jumps.
339
340			=item * manual reschedule mode ($reschedule_cb = coderef)
341
342	root	1.37	In this mode $interval and $at are both being ignored. Instead, each
343			time the periodic watcher gets scheduled, the reschedule callback
344			($reschedule_cb) will be called with the watcher as first, and the current
345			time as second argument.
346	root	1.30
347	root	1.31	I<This callback MUST NOT stop or destroy this or any other periodic
348			watcher, ever>. If you need to stop it, return 1e30 and stop it
349			afterwards.
350	root	1.30
351			It must return the next time to trigger, based on the passed time value
352			(that is, the lowest time value larger than to the second argument). It
353			will usually be called just before the callback will be triggered, but
354			might be called at other times, too.
355
356			This can be used to create very complex timers, such as a timer that
357			triggers on each midnight, local time (actually 24 hours after the last
358			midnight, to keep the example simple. If you know a way to do it correctly
359			in about the same space (without requiring elaborate modules), drop me a
360			note :):
361
362			my $daily = EV::periodic 0, 0, sub {
363			my ($w, $now) = @_;
364
365			use Time::Local ();
366			my (undef, undef, undef, $d, $m, $y) = localtime $now;
367			86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
368			}, sub {
369			print "it's midnight or likely shortly after, now\n";
370			};
371	root	1.7
372	root	1.30	=back
373	root	1.20
374			The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
375	root	1.2
376	root	1.30	=item $w->set ($at, $interval, $reschedule_cb)
377	root	1.11
378	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be at
379			any time.
380
381	root	1.30	=item $w->again
382
383			Simply stops and starts the watcher again.
384
385	root	1.20
386			=item $w = EV::signal $signal, $callback
387
388			=item $w = EV::signal_ns $signal, $callback
389	root	1.11
390			Call the callback when $signal is received (the signal can be specified
391	root	1.20	by number or by name, just as with kill or %SIG).
392	root	1.2
393	root	1.11	EV will grab the signal for the process (the kernel only allows one
394	root	1.20	component to receive a signal at a time) when you start a signal watcher,
395			and removes it again when you stop it. Perl does the same when you
396			add/remove callbacks to %SIG, so watch out.
397
398			You can have as many signal watchers per signal as you want.
399	root	1.2
400	root	1.20	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
401	root	1.2
402	root	1.20	=item $w->set ($signal)
403	root	1.2
404	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be at
405			any time.
406
407	root	1.22	=item $current_signum = $w->signal
408
409			=item $old_signum = $w->signal ($new_signal)
410
411			Returns the previously set signal (always as a number not name) and
412			optionally set a new one.
413
414	root	1.20
415			=item $w = EV::child $pid, $callback
416
417			=item $w = EV::child_ns $pid, $callback
418
419			Call the callback when a status change for pid C<$pid> (or any pid
420			if C<$pid> is 0) has been received. More precisely: when the process
421			receives a SIGCHLD, EV will fetch the outstanding exit/wait status for all
422			changed/zombie children and call the callback.
423
424	root	1.27	You can access both status and pid by using the C<rstatus> and C<rpid>
425			methods on the watcher object.
426	root	1.20
427			You can have as many pid watchers per pid as you want.
428
429			The C<child_ns> variant doesn't start (activate) the newly created watcher.
430
431			=item $w->set ($pid)
432	root	1.1
433	root	1.20	Reconfigures the watcher, see the constructor above for details. Can be at
434			any time.
435	root	1.2
436	root	1.22	=item $current_pid = $w->pid
437
438			=item $old_pid = $w->pid ($new_pid)
439
440			Returns the previously set process id and optionally set a new one.
441
442	root	1.27	=item $exit_status = $w->rstatus
443
444			Return the exit/wait status (as returned by waitpid, see the waitpid entry
445			in perlfunc).
446
447			=item $pid = $w->rpid
448
449			Return the pid of the awaited child (useful when you have installed a
450			watcher for all pids).
451
452	root	1.2
453	root	1.20	=item $w = EV::idle $callback
454	root	1.2
455	root	1.20	=item $w = EV::idle_ns $callback
456	root	1.2
457	root	1.20	Call the callback when there are no pending io, timer/periodic, signal or
458			child events, i.e. when the process is idle.
459	root	1.2
460	root	1.20	The process will not block as long as any idle watchers are active, and
461			they will be called repeatedly until stopped.
462	root	1.2
463	root	1.20	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
464	root	1.2
465
466	root	1.20	=item $w = EV::prepare $callback
467	root	1.1
468	root	1.20	=item $w = EV::prepare_ns $callback
469	root	1.1
470	root	1.20	Call the callback just before the process would block. You can still
471			create/modify any watchers at this point.
472	root	1.1
473	root	1.20	See the EV::check watcher, below, for explanations and an example.
474	root	1.2
475	root	1.20	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
476	root	1.2
477
478	root	1.20	=item $w = EV::check $callback
479	root	1.2
480	root	1.20	=item $w = EV::check_ns $callback
481	root	1.10
482	root	1.20	Call the callback just after the process wakes up again (after it has
483			gathered events), but before any other callbacks have been invoked.
484	root	1.10
485	root	1.20	This is used to integrate other event-based software into the EV
486			mainloop: You register a prepare callback and in there, you create io and
487			timer watchers as required by the other software. Here is a real-world
488			example of integrating Net::SNMP (with some details left out):
489	root	1.10
490	root	1.20	our @snmp_watcher;
491	root	1.2
492	root	1.20	our $snmp_prepare = EV::prepare sub {
493			# do nothing unless active
494			$dispatcher->{_event_queue_h}
495			or return;
496	root	1.2
497	root	1.20	# make the dispatcher handle any outstanding stuff
498	root	1.2
499	root	1.20	# create an IO watcher for each and every socket
500			@snmp_watcher = (
501			(map { EV::io $_, EV::READ, sub { } }
502			keys %{ $dispatcher->{_descriptors} }),
503			);
504	root	1.2
505	root	1.20	# if there are any timeouts, also create a timer
506			push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
507			if $event->[Net::SNMP::Dispatcher::_ACTIVE];
508			};
509	root	1.2
510	root	1.20	The callbacks are irrelevant, the only purpose of those watchers is
511			to wake up the process as soon as one of those events occurs (socket
512			readable, or timer timed out). The corresponding EV::check watcher will then
513			clean up:
514	root	1.2
515	root	1.20	our $snmp_check = EV::check sub {
516			# destroy all watchers
517			@snmp_watcher = ();
518	root	1.2
519	root	1.20	# make the dispatcher handle any new stuff
520			};
521	root	1.2
522	root	1.20	The callbacks of the created watchers will not be called as the watchers
523			are destroyed before this cna happen (remember EV::check gets called
524			first).
525	root	1.2
526	root	1.20	The C<check_ns> variant doesn't start (activate) the newly created watcher.
527	root	1.1
528			=back
529
530	root	1.13	=head1 THREADS
531
532			Threads are not supported by this in any way. Perl pseudo-threads is evil
533	root	1.20	stuff and must die.
534	root	1.13
535	root	1.1	=cut
536
537	root	1.8	our $DIED = sub {
538			warn "EV: error in callback (ignoring): $@";
539			};
540
541	root	1.28	default_loop
542	root	1.26	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_METHODS}?';
543	root	1.1
544			1;
545
546	root	1.3	=head1 SEE ALSO
547
548	root	1.40	L<EV::DNS>.
549	root	1.3
550	root	1.1	=head1 AUTHOR
551
552			Marc Lehmann <schmorp@schmorp.de>
553			http://home.schmorp.de/
554
555			=cut
556