[ViewVC] Contents of: cvs/AnyEvent/README

NAME
    AnyEvent - provide framework for multiple event loops

    Event, Coro, Glib, Tk - various supported event loops

SYNOPSIS
       use AnyEvent;

       my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub {
          my ($poll_got) = @_;
          ...
       });

    * only one io watcher per $fh and $poll type is allowed (i.e. on a
    socket you can have one r + one w or one rw watcher, not any more
    (limitation by Tk).

    * the $poll_got passed to the handler needs to be checked by looking for
    single characters (e.g. with a regex), as it can contain more event
    types than were requested (e.g. a 'w' watcher might generate 'rw'
    events, limitation by Glib).

    * AnyEvent will keep filehandles alive, so as long as the watcher
    exists, the filehandle exists.

       my $w = AnyEvent->timer (after => $seconds, cb => sub {
          ...
       });

    * io and time watchers get canceled whenever $w is destroyed, so keep a
    copy

    * timers can only be used once and must be recreated for repeated
    operation (limitation by Glib and Tk).

       my $w = AnyEvent->condvar; # kind of main loop replacement
       $w->wait; # enters main loop till $condvar gets ->broadcast
       $w->broadcast; # wake up current and all future wait's

    * condvars are used to give blocking behaviour when neccessary. Create a
    condvar for any "request" or "event" your module might create,
    "->broadcast" it when the event happens and provide a function that
    calls "->wait" for it. See the examples below.

DESCRIPTION
    AnyEvent provides an identical interface to multiple event loops. This
    allows module authors to utilizy an event loop without forcing module
    users to use the same event loop (as only a single event loop can
    coexist peacefully at any one time).

    The interface itself is vaguely similar but not identical to the Event
    module.

    On the first call of any method, the module tries to detect the
    currently loaded event loop by probing wether any of the following
    modules is loaded: Coro::Event, Event, Glib, Tk. The first one found is
    used. If none is found, the module tries to load these modules in the
    order given. The first one that could be successfully loaded will be
    used. If still none could be found, it will issue an error.

SUPPLYING YOUR OWN EVENT MODEL INTERFACE
    If you need to support another event library which isn't directly
    supported by AnyEvent, you can supply your own interface to it by
    pushing, before the first watch gets created, the package name of the
    event module and the package name of the interface to use onto
    @AnyEvent::REGISTRY. You can do that before and even without loading
    AnyEvent.

    Example:

       push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];

    This tells AnyEvent to (literally) use the "urxvt::anyevent::" module
    when it finds the "urxvt" module is loaded. When AnyEvent is loaded and
    requested to find a suitable event model, it will first check for the
    urxvt module.

    The above isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) uses the
    above line exactly. An interface isn't included in AnyEvent because it
    doesn't make sense outside the embedded interpreter inside
    *rxvt-unicode*, and it is updated and maintained as part of the
    *rxvt-unicode* distribution.

ENVIRONMENT VARIABLES
    The following environment variables are used by this module:

    "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, reports which event
    model gets used.

EXAMPLE
    The following program uses an io watcher to read data from stdin, a
    timer to display a message once per second, and a condvar to exit the
    program when the user enters quit:

       use AnyEvent;

       my $cv = AnyEvent->condvar;

       my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
          warn "io event <$_[0]>\n";   # will always output <r>
          chomp (my $input = <STDIN>); # read a line
          warn "read: $input\n";       # output what has been read
          $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
       });

       my $time_watcher; # can only be used once

       sub new_timer {
          $timer = AnyEvent->timer (after => 1, cb => sub {
             warn "timeout\n"; # print 'timeout' about every second
             &new_timer; # and restart the time
          });
       }

       new_timer; # create first timer

       $cv->wait; # wait until user enters /^q/i

REAL-WORLD EXAMPLE
    Consider the Net::FCP module. It features (among others) the following
    API calls, which are to freenet what HTTP GET requests are to http:

       my $data = $fcp->client_get ($url); # blocks

       my $transaction = $fcp->txn_client_get ($url); # does not block
       $transaction->cb ( sub { ... } ); # set optional result callback
       my $data = $transaction->result; # possibly blocks

    The "client_get" method works like "LWP::Simple::get": it requests the
    given URL and waits till the data has arrived. It is defined to be:

       sub client_get { $_[0]->txn_client_get ($_[1])->result }

    And in fact is automatically generated. This is the blocking API of
    Net::FCP, and it works as simple as in any other, similar, module.

    More complicated is "txn_client_get": It only creates a transaction
    (completion, result, ...) object and initiates the transaction.

       my $txn = bless { }, Net::FCP::Txn::;

    It also creates a condition variable that is used to signal the
    completion of the request:

       $txn->{finished} = AnyAvent->condvar;

    It then creates a socket in non-blocking mode.

       socket $txn->{fh}, ...;
       fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
       connect $txn->{fh}, ...
          and !$!{EWOULDBLOCK}
          and !$!{EINPROGRESS}
          and Carp::croak "unable to connect: $!\n";

    Then it creates a write-watcher which gets called whenever an error
    occurs or the connection succeeds:

       $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });

    And returns this transaction object. The "fh_ready_w" callback gets
    called as soon as the event loop detects that the socket is ready for
    writing.

    The "fh_ready_w" method makes the socket blocking again, writes the
    request data and replaces the watcher by a read watcher (waiting for
    reply data). The actual code is more complicated, but that doesn't
    matter for this example:

       fcntl $txn->{fh}, F_SETFL, 0;
       syswrite $txn->{fh}, $txn->{request}
          or die "connection or write error";
       $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });

    Again, "fh_ready_r" waits till all data has arrived, and then stores the
    result and signals any possible waiters that the request ahs finished:

       sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};

       if (end-of-file or data complete) {
         $txn->{result} = $txn->{buf};
         $txn->{finished}->broadcast;
         $txb->{cb}->($txn) of $txn->{cb}; # also call callback
       }

    The "result" method, finally, just waits for the finished signal (if the
    request was already finished, it doesn't wait, of course, and returns
    the data:

       $txn->{finished}->wait;
       return $txn->{result};

    The actual code goes further and collects all errors ("die"s,
    exceptions) that occured during request processing. The "result" method
    detects wether an exception as thrown (it is stored inside the $txn
    object) and just throws the exception, which means connection errors and
    other problems get reported tot he code that tries to use the result,
    not in a random callback.

    All of this enables the following usage styles:

    1. Blocking:

       my $data = $fcp->client_get ($url);

    2. Blocking, but parallelizing:

       my @datas = map $_->result,
                      map $fcp->txn_client_get ($_),
                         @urls;

    Both blocking examples work without the module user having to know
    anything about events.

    3a. Event-based in a main program, using any support Event module:

       use Event;

       $fcp->txn_client_get ($url)->cb (sub {
          my $txn = shift;
          my $data = $txn->result;
          ...
       });

       Event::loop;

    3b. The module user could use AnyEvent, too:

       use AnyEvent;

       my $quit = AnyEvent->condvar;

       $fcp->txn_client_get ($url)->cb (sub {
          ...
          $quit->broadcast;
       });

       $quit->wait;

SEE ALSO
    Event modules: Coro::Event, Coro, Event, Glib::Event, Glib.

    Implementations: AnyEvent::Impl::Coro, AnyEvent::Impl::Event,
    AnyEvent::Impl::Glib, AnyEvent::Impl::Tk.

    Nontrivial usage example: Net::FCP.


Revision:	1.5
Committed:	Sun Jan 8 04:41:08 2006 UTC (18 years, 4 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_0, rel-1_02, rel-1_01
Changes since 1.4:	+23 -0 lines
Log Message:	* empty log message *
#	Content
1	NAME
2	AnyEvent - provide framework for multiple event loops
3
4	Event, Coro, Glib, Tk - various supported event loops
5
6	SYNOPSIS
7	use AnyEvent;
8
9	my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub {
10	my ($poll_got) = @_;
11	...
12	});
13
14	* only one io watcher per $fh and $poll type is allowed (i.e. on a
15	socket you can have one r + one w or one rw watcher, not any more
16	(limitation by Tk).
17
18	* the $poll_got passed to the handler needs to be checked by looking for
19	single characters (e.g. with a regex), as it can contain more event
20	types than were requested (e.g. a 'w' watcher might generate 'rw'
21	events, limitation by Glib).
22
23	* AnyEvent will keep filehandles alive, so as long as the watcher
24	exists, the filehandle exists.
25
26	my $w = AnyEvent->timer (after => $seconds, cb => sub {
27	...
28	});
29
30	* io and time watchers get canceled whenever $w is destroyed, so keep a
31	copy
32
33	* timers can only be used once and must be recreated for repeated
34	operation (limitation by Glib and Tk).
35
36	my $w = AnyEvent->condvar; # kind of main loop replacement
37	$w->wait; # enters main loop till $condvar gets ->broadcast
38	$w->broadcast; # wake up current and all future wait's
39
40	* condvars are used to give blocking behaviour when neccessary. Create a
41	condvar for any "request" or "event" your module might create,
42	"->broadcast" it when the event happens and provide a function that
43	calls "->wait" for it. See the examples below.
44
45	DESCRIPTION
46	AnyEvent provides an identical interface to multiple event loops. This
47	allows module authors to utilizy an event loop without forcing module
48	users to use the same event loop (as only a single event loop can
49	coexist peacefully at any one time).
50
51	The interface itself is vaguely similar but not identical to the Event
52	module.
53
54	On the first call of any method, the module tries to detect the
55	currently loaded event loop by probing wether any of the following
56	modules is loaded: Coro::Event, Event, Glib, Tk. The first one found is
57	used. If none is found, the module tries to load these modules in the
58	order given. The first one that could be successfully loaded will be
59	used. If still none could be found, it will issue an error.
60
61	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
62	If you need to support another event library which isn't directly
63	supported by AnyEvent, you can supply your own interface to it by
64	pushing, before the first watch gets created, the package name of the
65	event module and the package name of the interface to use onto
66	@AnyEvent::REGISTRY. You can do that before and even without loading
67	AnyEvent.
68
69	Example:
70
71	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
72
73	This tells AnyEvent to (literally) use the "urxvt::anyevent::" module
74	when it finds the "urxvt" module is loaded. When AnyEvent is loaded and
75	requested to find a suitable event model, it will first check for the
76	urxvt module.
77
78	The above isn't fictitious, the rxvt-unicode (a.k.a. urxvt) uses the
79	above line exactly. An interface isn't included in AnyEvent because it
80	doesn't make sense outside the embedded interpreter inside
81	rxvt-unicode, and it is updated and maintained as part of the
82	rxvt-unicode distribution.
83
84	ENVIRONMENT VARIABLES
85	The following environment variables are used by this module:
86
87	"PERL_ANYEVENT_VERBOSE" when set to 2 or higher, reports which event
88	model gets used.
89
90	EXAMPLE
91	The following program uses an io watcher to read data from stdin, a
92	timer to display a message once per second, and a condvar to exit the
93	program when the user enters quit:
94
95	use AnyEvent;
96
97	my $cv = AnyEvent->condvar;
98
99	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
100	warn "io event <$_[0]>\n"; # will always output <r>
101	chomp (my $input = <STDIN>); # read a line
102	warn "read: $input\n"; # output what has been read
103	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
104	});
105
106	my $time_watcher; # can only be used once
107
108	sub new_timer {
109	$timer = AnyEvent->timer (after => 1, cb => sub {
110	warn "timeout\n"; # print 'timeout' about every second
111	&new_timer; # and restart the time
112	});
113	}
114
115	new_timer; # create first timer
116
117	$cv->wait; # wait until user enters /^q/i
118
119	REAL-WORLD EXAMPLE
120	Consider the Net::FCP module. It features (among others) the following
121	API calls, which are to freenet what HTTP GET requests are to http:
122
123	my $data = $fcp->client_get ($url); # blocks
124
125	my $transaction = $fcp->txn_client_get ($url); # does not block
126	$transaction->cb ( sub { ... } ); # set optional result callback
127	my $data = $transaction->result; # possibly blocks
128
129	The "client_get" method works like "LWP::Simple::get": it requests the
130	given URL and waits till the data has arrived. It is defined to be:
131
132	sub client_get { $_[0]->txn_client_get ($_[1])->result }
133
134	And in fact is automatically generated. This is the blocking API of
135	Net::FCP, and it works as simple as in any other, similar, module.
136
137	More complicated is "txn_client_get": It only creates a transaction
138	(completion, result, ...) object and initiates the transaction.
139
140	my $txn = bless { }, Net::FCP::Txn::;
141
142	It also creates a condition variable that is used to signal the
143	completion of the request:
144
145	$txn->{finished} = AnyAvent->condvar;
146
147	It then creates a socket in non-blocking mode.
148
149	socket $txn->{fh}, ...;
150	fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
151	connect $txn->{fh}, ...
152	and !$!{EWOULDBLOCK}
153	and !$!{EINPROGRESS}
154	and Carp::croak "unable to connect: $!\n";
155
156	Then it creates a write-watcher which gets called whenever an error
157	occurs or the connection succeeds:
158
159	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
160
161	And returns this transaction object. The "fh_ready_w" callback gets
162	called as soon as the event loop detects that the socket is ready for
163	writing.
164
165	The "fh_ready_w" method makes the socket blocking again, writes the
166	request data and replaces the watcher by a read watcher (waiting for
167	reply data). The actual code is more complicated, but that doesn't
168	matter for this example:
169
170	fcntl $txn->{fh}, F_SETFL, 0;
171	syswrite $txn->{fh}, $txn->{request}
172	or die "connection or write error";
173	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
174
175	Again, "fh_ready_r" waits till all data has arrived, and then stores the
176	result and signals any possible waiters that the request ahs finished:
177
178	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
179
180	if (end-of-file or data complete) {
181	$txn->{result} = $txn->{buf};
182	$txn->{finished}->broadcast;
183	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
184	}
185
186	The "result" method, finally, just waits for the finished signal (if the
187	request was already finished, it doesn't wait, of course, and returns
188	the data:
189
190	$txn->{finished}->wait;
191	return $txn->{result};
192
193	The actual code goes further and collects all errors ("die"s,
194	exceptions) that occured during request processing. The "result" method
195	detects wether an exception as thrown (it is stored inside the $txn
196	object) and just throws the exception, which means connection errors and
197	other problems get reported tot he code that tries to use the result,
198	not in a random callback.
199
200	All of this enables the following usage styles:
201
202	1. Blocking:
203
204	my $data = $fcp->client_get ($url);
205
206	2. Blocking, but parallelizing:
207
208	my @datas = map $_->result,
209	map $fcp->txn_client_get ($_),
210	@urls;
211
212	Both blocking examples work without the module user having to know
213	anything about events.
214
215	3a. Event-based in a main program, using any support Event module:
216
217	use Event;
218
219	$fcp->txn_client_get ($url)->cb (sub {
220	my $txn = shift;
221	my $data = $txn->result;
222	...
223	});
224
225	Event::loop;
226
227	3b. The module user could use AnyEvent, too:
228
229	use AnyEvent;
230
231	my $quit = AnyEvent->condvar;
232
233	$fcp->txn_client_get ($url)->cb (sub {
234	...
235	$quit->broadcast;
236	});
237
238	$quit->wait;
239
240	SEE ALSO
241	Event modules: Coro::Event, Coro, Event, Glib::Event, Glib.
242
243	Implementations: AnyEvent::Impl::Coro, AnyEvent::Impl::Event,
244	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk.
245
246	Nontrivial usage example: Net::FCP.
247
248