ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/AnyEvent/README
(Generate patch)

Comparing AnyEvent/README (file contents):
Revision 1.15 by root, Wed Apr 16 15:10:10 2008 UTC vs.
Revision 1.16 by root, Sat Apr 19 04:58:14 2008 UTC

… …
13 13
14 my $w = AnyEvent->timer (after => $seconds, cb => sub { 14 my $w = AnyEvent->timer (after => $seconds, cb => sub {
15 ... 15 ...
16 }); 16 });
17 17
18 my $w = AnyEvent->condvar; # stores wether a condition was flagged 18 my $w = AnyEvent->condvar; # stores whether a condition was flagged
19 $w->wait; # enters "main loop" till $condvar gets ->broadcast 19 $w->wait; # enters "main loop" till $condvar gets ->broadcast
20 $w->broadcast; # wake up current and all future wait's 20 $w->broadcast; # wake up current and all future wait's
21 21
22WHY YOU SHOULD USE THIS MODULE (OR NOT) 22WHY YOU SHOULD USE THIS MODULE (OR NOT)
23 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 23 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
… …
27 policy* and AnyEvent is *small and efficient*. 27 policy* and AnyEvent is *small and efficient*.
28 28
29 First and foremost, *AnyEvent is not an event model* itself, it only 29 First and foremost, *AnyEvent is not an event model* itself, it only
30 interfaces to whatever event model the main program happens to use in a 30 interfaces to whatever event model the main program happens to use in a
31 pragmatic way. For event models and certain classes of immortals alike, 31 pragmatic way. For event models and certain classes of immortals alike,
32 the statement "there can only be one" is a bitter reality, and AnyEvent 32 the statement "there can only be one" is a bitter reality: In general,
33 helps hiding the differences. 33 only one event loop can be active at the same time in a process.
34 AnyEvent helps hiding the differences between those event loops.
34 35
35 The goal of AnyEvent is to offer module authors the ability to do event 36 The goal of AnyEvent is to offer module authors the ability to do event
36 programming (waiting for I/O or timer events) without subscribing to a 37 programming (waiting for I/O or timer events) without subscribing to a
37 religion, a way of living, and most importantly: without forcing your 38 religion, a way of living, and most importantly: without forcing your
38 module users into the same thing by forcing them to use the same event 39 module users into the same thing by forcing them to use the same event
39 model you use. 40 model you use.
40 41
41 For modules like POE or IO::Async (which is actually doing all I/O 42 For modules like POE or IO::Async (which is a total misnomer as it is
42 *synchronously*...), using them in your module is like joining a cult: 43 actually doing all I/O *synchronously*...), using them in your module is
43 After you joined, you are dependent on them and you cannot use anything 44 like joining a cult: After you joined, you are dependent on them and you
44 else, as it is simply incompatible to everything that isn't itself. 45 cannot use anything else, as it is simply incompatible to everything
46 that isn't itself. What's worse, all the potential users of your module
47 are *also* forced to use the same event loop you use.
45 48
46 AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk 49 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
47 works fine etc. etc. but none of these work together with the rest: POE 50 fine. AnyEvent + Tk works fine etc. etc. but none of these work together
48 + IO::Async? no go. Tk + Event? no go. If your module uses one of those, 51 with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if your
49 every user of your module has to use it, too. If your module uses 52 module uses one of those, every user of your module has to use it, too.
50 AnyEvent, it works transparently with all event models it supports 53 But if your module uses AnyEvent, it works transparently with all event
51 (including stuff like POE and IO::Async). 54 models it supports (including stuff like POE and IO::Async, as long as
55 those use one of the supported event loops. It is trivial to add new
56 event loops to AnyEvent, too, so it is future-proof).
52 57
53 In addition of being free of having to use *the one and only true event 58 In addition to being free of having to use *the one and only true event
54 model*, AnyEvent also is free of bloat and policy: with POE or similar 59 model*, AnyEvent also is free of bloat and policy: with POE or similar
55 modules, you get an enourmous amount of code and strict rules you have 60 modules, you get an enourmous amount of code and strict rules you have
56 to follow. AnyEvent, on the other hand, is lean and to the point by only 61 to follow. AnyEvent, on the other hand, is lean and up to the point, by
57 offering the functionality that is useful, in as thin as a wrapper as 62 only offering the functionality that is necessary, in as thin as a
58 technically possible. 63 wrapper as technically possible.
59 64
60 Of course, if you want lots of policy (this can arguably be somewhat 65 Of course, if you want lots of policy (this can arguably be somewhat
61 useful) and you want to force your users to use the one and only event 66 useful) and you want to force your users to use the one and only event
62 model, you should *not* use this module. 67 model, you should *not* use this module.
63 68
… …
65 AnyEvent provides an identical interface to multiple event loops. This 70 AnyEvent provides an identical interface to multiple event loops. This
66 allows module authors to utilise an event loop without forcing module 71 allows module authors to utilise an event loop without forcing module
67 users to use the same event loop (as only a single event loop can 72 users to use the same event loop (as only a single event loop can
68 coexist peacefully at any one time). 73 coexist peacefully at any one time).
69 74
70 The interface itself is vaguely similar but not identical to the Event 75 The interface itself is vaguely similar, but not identical to the Event
71 module. 76 module.
72 77
73 On the first call of any method, the module tries to detect the 78 During the first call of any watcher-creation method, the module tries
74 currently loaded event loop by probing wether any of the following 79 to detect the currently loaded event loop by probing whether one of the
75 modules is loaded: Coro::EV, Coro::Event, EV, Event, Glib, Tk. The first 80 following modules is already loaded: Coro::EV, Coro::Event, EV, Event,
76 one found is used. If none are found, the module tries to load these 81 Glib, Tk. The first one found is used. If none are found, the module
77 modules in the order given. The first one that could be successfully 82 tries to load these modules in the stated order. The first one that can
78 loaded will be used. If still none could be found, AnyEvent will fall 83 be successfully loaded will be used. If, after this, still none could be
79 back to a pure-perl event loop, which is also not very efficient. 84 found, AnyEvent will fall back to a pure-perl event loop, which is not
85 very efficient, but should work everywhere.
80 86
81 Because AnyEvent first checks for modules that are already loaded, 87 Because AnyEvent first checks for modules that are already loaded,
82 loading an Event model explicitly before first using AnyEvent will 88 loading an event model explicitly before first using AnyEvent will
83 likely make that model the default. For example: 89 likely make that model the default. For example:
84 90
85 use Tk; 91 use Tk;
86 use AnyEvent; 92 use AnyEvent;
87 93
88 # .. AnyEvent will likely default to Tk 94 # .. AnyEvent will likely default to Tk
95
96 The *likely* means that, if any module loads another event model and
97 starts using it, all bets are off. Maybe you should tell their authors
98 to use AnyEvent so their modules work together with others seamlessly...
89 99
90 The pure-perl implementation of AnyEvent is called 100 The pure-perl implementation of AnyEvent is called
91 "AnyEvent::Impl::Perl". Like other event modules you can load it 101 "AnyEvent::Impl::Perl". Like other event modules you can load it
92 explicitly. 102 explicitly.
93 103
… …
96 stores relevant data for each kind of event you are waiting for, such as 106 stores relevant data for each kind of event you are waiting for, such as
97 the callback to call, the filehandle to watch, etc. 107 the callback to call, the filehandle to watch, etc.
98 108
99 These watchers are normal Perl objects with normal Perl lifetime. After 109 These watchers are normal Perl objects with normal Perl lifetime. After
100 creating a watcher it will immediately "watch" for events and invoke the 110 creating a watcher it will immediately "watch" for events and invoke the
111 callback when the event occurs (of course, only when the event model is
112 in control).
113
101 callback. To disable the watcher you have to destroy it (e.g. by setting 114 To disable the watcher you have to destroy it (e.g. by setting the
102 the variable that stores it to "undef" or otherwise deleting all 115 variable you store it in to "undef" or otherwise deleting all references
103 references to it). 116 to it).
104 117
105 All watchers are created by calling a method on the "AnyEvent" class. 118 All watchers are created by calling a method on the "AnyEvent" class.
106 119
120 Many watchers either are used with "recursion" (repeating timers for
121 example), or need to refer to their watcher object in other ways.
122
123 An any way to achieve that is this pattern:
124
125 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
126 # you can use $w here, for example to undef it
127 undef $w;
128 });
129
130 Note that "my $w; $w =" combination. This is necessary because in Perl,
131 my variables are only visible after the statement in which they are
132 declared.
133
107 IO WATCHERS 134 IO WATCHERS
108 You can create I/O watcher by calling the "AnyEvent->io" method with the 135 You can create an I/O watcher by calling the "AnyEvent->io" method with
109 following mandatory arguments: 136 the following mandatory key-value pairs as arguments:
110 137
111 "fh" the Perl *filehandle* (not filedescriptor) to watch for events. 138 "fh" the Perl *file handle* (*not* file descriptor) to watch for events.
112 "poll" must be a string that is either "r" or "w", that creates a 139 "poll" must be a string that is either "r" or "w", which creates a
113 watcher waiting for "r"eadable or "w"ritable events. "cb" the callback 140 watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"
114 to invoke everytime the filehandle becomes ready. 141 is the callback to invoke each time the file handle becomes ready.
115 142
116 Filehandles will be kept alive, so as long as the watcher exists, the 143 File handles will be kept alive, so as long as the watcher exists, the
117 filehandle exists, too. 144 file handle exists, too.
145
146 It is not allowed to close a file handle as long as any watcher is
147 active on the underlying file descriptor.
148
149 Some event loops issue spurious readyness notifications, so you should
150 always use non-blocking calls when reading/writing from/to your file
151 handles.
118 152
119 Example: 153 Example:
120 154
121 # wait for readability of STDIN, then read a line and disable the watcher 155 # wait for readability of STDIN, then read a line and disable the watcher
122 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 156 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
… …
127 161
128 TIME WATCHERS 162 TIME WATCHERS
129 You can create a time watcher by calling the "AnyEvent->timer" method 163 You can create a time watcher by calling the "AnyEvent->timer" method
130 with the following mandatory arguments: 164 with the following mandatory arguments:
131 165
132 "after" after how many seconds (fractions are supported) should the 166 "after" specifies after how many seconds (fractional values are
133 timer activate. "cb" the callback to invoke. 167 supported) should the timer activate. "cb" the callback to invoke in
168 that case.
134 169
135 The timer callback will be invoked at most once: if you want a repeating 170 The timer callback will be invoked at most once: if you want a repeating
136 timer you have to create a new watcher (this is a limitation by both Tk 171 timer you have to create a new watcher (this is a limitation by both Tk
137 and Glib). 172 and Glib).
138 173
… …
144 }); 179 });
145 180
146 # to cancel the timer: 181 # to cancel the timer:
147 undef $w; 182 undef $w;
148 183
149 CONDITION WATCHERS 184 Example 2:
185
186 # fire an event after 0.5 seconds, then roughly every second
187 my $w;
188
189 my $cb = sub {
190 # cancel the old timer while creating a new one
191 $w = AnyEvent->timer (after => 1, cb => $cb);
192 };
193
194 # start the "loop" by creating the first watcher
195 $w = AnyEvent->timer (after => 0.5, cb => $cb);
196
197 TIMING ISSUES
198 There are two ways to handle timers: based on real time (relative, "fire
199 in 10 seconds") and based on wallclock time (absolute, "fire at 12
200 o'clock").
201
202 While most event loops expect timers to specified in a relative way,
203 they use absolute time internally. This makes a difference when your
204 clock "jumps", for example, when ntp decides to set your clock backwards
205 from the wrong 2014-01-01 to 2008-01-01, a watcher that you created to
206 fire "after" a second might actually take six years to finally fire.
207
208 AnyEvent cannot compensate for this. The only event loop that is
209 conscious about these issues is EV, which offers both relative
210 (ev_timer) and absolute (ev_periodic) timers.
211
212 AnyEvent always prefers relative timers, if available, matching the
213 AnyEvent API.
214
215 SIGNAL WATCHERS
216 You can watch for signals using a signal watcher, "signal" is the signal
217 *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked
218 whenever a signal occurs.
219
220 Multiple signals occurances can be clumped together into one callback
221 invocation, and callback invocation will be synchronous. synchronous
222 means that it might take a while until the signal gets handled by the
223 process, but it is guarenteed not to interrupt any other callbacks.
224
225 The main advantage of using these watchers is that you can share a
226 signal between multiple watchers.
227
228 This watcher might use %SIG, so programs overwriting those signals
229 directly will likely not work correctly.
230
231 Example: exit on SIGINT
232
233 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
234
235 CHILD PROCESS WATCHERS
236 You can also watch on a child process exit and catch its exit status.
237
238 The child process is specified by the "pid" argument (if set to 0, it
239 watches for any child process exit). The watcher will trigger as often
240 as status change for the child are received. This works by installing a
241 signal handler for "SIGCHLD". The callback will be called with the pid
242 and exit status (as returned by waitpid).
243
244 Example: wait for pid 1333
245
246 my $w = AnyEvent->child (
247 pid => 1333,
248 cb => sub {
249 my ($pid, $status) = @_;
250 warn "pid $pid exited with status $status";
251 },
252 );
253
254 CONDITION VARIABLES
150 Condition watchers can be created by calling the "AnyEvent->condvar" 255 Condition variables can be created by calling the "AnyEvent->condvar"
151 method without any arguments. 256 method without any arguments.
152 257
153 A condition watcher watches for a condition - precisely that the 258 A condition variable waits for a condition - precisely that the
154 "->broadcast" method has been called. 259 "->broadcast" method has been called.
155 260
261 They are very useful to signal that a condition has been fulfilled, for
262 example, if you write a module that does asynchronous http requests,
263 then a condition variable would be the ideal candidate to signal the
264 availability of results.
265
266 You can also use condition variables to block your main program until an
267 event occurs - for example, you could "->wait" in your main program
268 until the user clicks the Quit button in your app, which would
269 "->broadcast" the "quit" event.
270
156 Note that condition watchers recurse into the event loop - if you have 271 Note that condition variables recurse into the event loop - if you have
157 two watchers that call "->wait" in a round-robbin fashion, you lose. 272 two pirces of code that call "->wait" in a round-robbin fashion, you
158 Therefore, condition watchers are good to export to your caller, but you 273 lose. Therefore, condition variables are good to export to your caller,
159 should avoid making a blocking wait, at least in callbacks, as this 274 but you should avoid making a blocking wait yourself, at least in
160 usually asks for trouble. 275 callbacks, as this asks for trouble.
161 276
162 The watcher has only two methods: 277 This object has two methods:
163 278
164 $cv->wait 279 $cv->wait
165 Wait (blocking if necessary) until the "->broadcast" method has been 280 Wait (blocking if necessary) until the "->broadcast" method has been
166 called on c<$cv>, while servicing other watchers normally. 281 called on c<$cv>, while servicing other watchers normally.
167 282
168 You can only wait once on a condition - additional calls will return 283 You can only wait once on a condition - additional calls will return
169 immediately. 284 immediately.
170 285
171 Not all event models support a blocking wait - some die in that case 286 Not all event models support a blocking wait - some die in that case
172 (programs might want to do that so they stay interactive), so *if 287 (programs might want to do that to stay interactive), so *if you are
173 you are using this from a module, never require a blocking wait*, 288 using this from a module, never require a blocking wait*, but let
174 but let the caller decide wether the call will block or not (for 289 the caller decide whether the call will block or not (for example,
175 example, by coupling condition variables with some kind of request 290 by coupling condition variables with some kind of request results
176 results and supporting callbacks so the caller knows that getting 291 and supporting callbacks so the caller knows that getting the result
177 the result will not block, while still suppporting blocking waits if 292 will not block, while still suppporting blocking waits if the caller
178 the caller so desires). 293 so desires).
179 294
180 Another reason *never* to "->wait" in a module is that you cannot 295 Another reason *never* to "->wait" in a module is that you cannot
181 sensibly have two "->wait"'s in parallel, as that would require 296 sensibly have two "->wait"'s in parallel, as that would require
182 multiple interpreters or coroutines/threads, none of which 297 multiple interpreters or coroutines/threads, none of which
183 "AnyEvent" can supply (the coroutine-aware backends "Coro::EV" and 298 "AnyEvent" can supply (the coroutine-aware backends
184 "Coro::Event" explicitly support concurrent "->wait"'s from 299 AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly
185 different coroutines, however). 300 support concurrent "->wait"'s from different coroutines, however).
186 301
187 $cv->broadcast 302 $cv->broadcast
188 Flag the condition as ready - a running "->wait" and all further 303 Flag the condition as ready - a running "->wait" and all further
189 calls to "wait" will return after this method has been called. If 304 calls to "wait" will (eventually) return after this method has been
190 nobody is waiting the broadcast will be remembered.. 305 called. If nobody is waiting the broadcast will be remembered..
191 306
192 Example: 307 Example:
193 308
194 # wait till the result is ready 309 # wait till the result is ready
195 my $result_ready = AnyEvent->condvar; 310 my $result_ready = AnyEvent->condvar;
196 311
197 # do something such as adding a timer 312 # do something such as adding a timer
198 # or socket watcher the calls $result_ready->broadcast 313 # or socket watcher the calls $result_ready->broadcast
199 # when the "result" is ready. 314 # when the "result" is ready.
315 # in this case, we simply use a timer:
316 my $w = AnyEvent->timer (
317 after => 1,
318 cb => sub { $result_ready->broadcast },
319 );
200 320
321 # this "blocks" (while handling events) till the watcher
322 # calls broadcast
201 $result_ready->wait; 323 $result_ready->wait;
202 324
203 SIGNAL WATCHERS 325GLOBAL VARIABLES AND FUNCTIONS
204 You can listen for signals using a signal watcher, "signal" is the
205 signal *name* without any "SIG" prefix. Multiple signals events can be
206 clumped together into one callback invocation, and callback invocation
207 might or might not be asynchronous.
208
209 These watchers might use %SIG, so programs overwriting those signals
210 directly will likely not work correctly.
211
212 Example: exit on SIGINT
213
214 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
215
216 CHILD PROCESS WATCHERS
217 You can also listen for the status of a child process specified by the
218 "pid" argument (or any child if the pid argument is 0). The watcher will
219 trigger as often as status change for the child are received. This works
220 by installing a signal handler for "SIGCHLD". The callback will be
221 called with the pid and exit status (as returned by waitpid).
222
223 Example: wait for pid 1333
224
225 my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
226
227GLOBALS
228 $AnyEvent::MODEL 326 $AnyEvent::MODEL
229 Contains "undef" until the first watcher is being created. Then it 327 Contains "undef" until the first watcher is being created. Then it
230 contains the event model that is being used, which is the name of 328 contains the event model that is being used, which is the name of
231 the Perl class implementing the model. This class is usually one of 329 the Perl class implementing the model. This class is usually one of
232 the "AnyEvent::Impl:xxx" modules, but can be any other class in the 330 the "AnyEvent::Impl:xxx" modules, but can be any other class in the
… …
243 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. 341 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
244 342
245 AnyEvent::detect 343 AnyEvent::detect
246 Returns $AnyEvent::MODEL, forcing autodetection of the event model 344 Returns $AnyEvent::MODEL, forcing autodetection of the event model
247 if necessary. You should only call this function right before you 345 if necessary. You should only call this function right before you
248 would have created an AnyEvent watcher anyway, that is, very late at 346 would have created an AnyEvent watcher anyway, that is, as late as
249 runtime. 347 possible at runtime.
250 348
251WHAT TO DO IN A MODULE 349WHAT TO DO IN A MODULE
252 As a module author, you should "use AnyEvent" and call AnyEvent methods 350 As a module author, you should "use AnyEvent" and call AnyEvent methods
253 freely, but you should not load a specific event module or rely on it. 351 freely, but you should not load a specific event module or rely on it.
254 352
255 Be careful when you create watchers in the module body - Anyevent will 353 Be careful when you create watchers in the module body - AnyEvent will
256 decide which event module to use as soon as the first method is called, 354 decide which event module to use as soon as the first method is called,
257 so by calling AnyEvent in your module body you force the user of your 355 so by calling AnyEvent in your module body you force the user of your
258 module to load the event module first. 356 module to load the event module first.
259 357
358 Never call "->wait" on a condition variable unless you *know* that the
359 "->broadcast" method has been called on it already. This is because it
360 will stall the whole program, and the whole point of using events is to
361 stay interactive.
362
363 It is fine, however, to call "->wait" when the user of your module
364 requests it (i.e. if you create a http request object ad have a method
365 called "results" that returns the results, it should call "->wait"
366 freely, as the user of your module knows what she is doing. always).
367
260WHAT TO DO IN THE MAIN PROGRAM 368WHAT TO DO IN THE MAIN PROGRAM
261 There will always be a single main program - the only place that should 369 There will always be a single main program - the only place that should
262 dictate which event model to use. 370 dictate which event model to use.
263 371
264 If it doesn't care, it can just "use AnyEvent" and use it itself, or not 372 If it doesn't care, it can just "use AnyEvent" and use it itself, or not
265 do anything special and let AnyEvent decide which implementation to 373 do anything special (it does not need to be event-based) and let
266 chose. 374 AnyEvent decide which implementation to chose if some module relies on
375 it.
267 376
268 If the main program relies on a specific event model (for example, in 377 If the main program relies on a specific event model. For example, in
269 Gtk2 programs you have to rely on either Glib or Glib::Event), you 378 Gtk2 programs you have to rely on the Glib module. You should load the
270 should load it before loading AnyEvent or any module that uses it, 379 event module before loading AnyEvent or any module that uses it:
271 generally, as early as possible. The reason is that modules might create 380 generally speaking, you should load it as early as possible. The reason
272 watchers when they are loaded, and AnyEvent will decide on the event 381 is that modules might create watchers when they are loaded, and AnyEvent
273 model to use as soon as it creates watchers, and it might chose the 382 will decide on the event model to use as soon as it creates watchers,
274 wrong one unless you load the correct one yourself. 383 and it might chose the wrong one unless you load the correct one
384 yourself.
275 385
276 You can chose to use a rather inefficient pure-perl implementation by 386 You can chose to use a rather inefficient pure-perl implementation by
277 loading the "AnyEvent::Impl::Perl" module, but letting AnyEvent chose is 387 loading the "AnyEvent::Impl::Perl" module, which gives you similar
278 generally better. 388 behaviour everywhere, but letting AnyEvent chose is generally better.
279 389
280SUPPLYING YOUR OWN EVENT MODEL INTERFACE 390SUPPLYING YOUR OWN EVENT MODEL INTERFACE
391 This is an advanced topic that you do not normally need to use AnyEvent
392 in a module. This section is only of use to event loop authors who want
393 to provide AnyEvent compatibility.
394
281 If you need to support another event library which isn't directly 395 If you need to support another event library which isn't directly
282 supported by AnyEvent, you can supply your own interface to it by 396 supported by AnyEvent, you can supply your own interface to it by
283 pushing, before the first watcher gets created, the package name of the 397 pushing, before the first watcher gets created, the package name of the
284 event module and the package name of the interface to use onto 398 event module and the package name of the interface to use onto
285 @AnyEvent::REGISTRY. You can do that before and even without loading 399 @AnyEvent::REGISTRY. You can do that before and even without loading
286 AnyEvent. 400 AnyEvent, so it is reasonably cheap.
287 401
288 Example: 402 Example:
289 403
290 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 404 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
291 405
292 This tells AnyEvent to (literally) use the "urxvt::anyevent::" 406 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
293 package/class when it finds the "urxvt" package/module is loaded. When 407 package/class when it finds the "urxvt" package/module is already
408 loaded.
409
294 AnyEvent is loaded and asked to find a suitable event model, it will 410 When AnyEvent is loaded and asked to find a suitable event model, it
295 first check for the presence of urxvt. 411 will first check for the presence of urxvt by trying to "use" the
412 "urxvt::anyevent" module.
296 413
297 The class should provide implementations for all watcher types (see 414 The class should provide implementations for all watcher types. See
298 AnyEvent::Impl::Event (source code), AnyEvent::Impl::Glib (Source code) 415 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
299 and so on for actual examples, use "perldoc -m AnyEvent::Impl::Glib" to 416 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
300 see the sources). 417 the sources.
301 418
419 If you don't provide "signal" and "child" watchers than AnyEvent will
420 provide suitable (hopefully) replacements.
421
302 The above isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) uses the 422 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
303 above line as-is. An interface isn't included in AnyEvent because it 423 terminal emulator uses the above line as-is. An interface isn't included
304 doesn't make sense outside the embedded interpreter inside 424 in AnyEvent because it doesn't make sense outside the embedded
305 *rxvt-unicode*, and it is updated and maintained as part of the 425 interpreter inside *rxvt-unicode*, and it is updated and maintained as
306 *rxvt-unicode* distribution. 426 part of the *rxvt-unicode* distribution.
307 427
308 *rxvt-unicode* also cheats a bit by not providing blocking access to 428 *rxvt-unicode* also cheats a bit by not providing blocking access to
309 condition variables: code blocking while waiting for a condition will 429 condition variables: code blocking while waiting for a condition will
310 "die". This still works with most modules/usages, and blocking calls 430 "die". This still works with most modules/usages, and blocking calls
311 must not be in an interactive application, so it makes sense. 431 must not be done in an interactive application, so it makes sense.
312 432
313ENVIRONMENT VARIABLES 433ENVIRONMENT VARIABLES
314 The following environment variables are used by this module: 434 The following environment variables are used by this module:
315 435
316 "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, reports which event 436 "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, cause AnyEvent to
317 model gets used. 437 report to STDERR which event model it chooses.
318 438
319EXAMPLE 439EXAMPLE PROGRAM
320 The following program uses an io watcher to read data from stdin, a 440 The following program uses an IO watcher to read data from STDIN, a
321 timer to display a message once per second, and a condvar to exit the 441 timer to display a message once per second, and a condition variable to
322 program when the user enters quit: 442 quit the program when the user enters quit:
323 443
324 use AnyEvent; 444 use AnyEvent;
325 445
326 my $cv = AnyEvent->condvar; 446 my $cv = AnyEvent->condvar;
327 447
328 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 448 my $io_watcher = AnyEvent->io (
449 fh => \*STDIN,
450 poll => 'r',
451 cb => sub {
329 warn "io event <$_[0]>\n"; # will always output <r> 452 warn "io event <$_[0]>\n"; # will always output <r>
330 chomp (my $input = <STDIN>); # read a line 453 chomp (my $input = <STDIN>); # read a line
331 warn "read: $input\n"; # output what has been read 454 warn "read: $input\n"; # output what has been read
332 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 455 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
456 },
333 }); 457 );
334 458
335 my $time_watcher; # can only be used once 459 my $time_watcher; # can only be used once
336 460
337 sub new_timer { 461 sub new_timer {
338 $timer = AnyEvent->timer (after => 1, cb => sub { 462 $timer = AnyEvent->timer (after => 1, cb => sub {
… …
419 $txn->{finished}->wait; 543 $txn->{finished}->wait;
420 return $txn->{result}; 544 return $txn->{result};
421 545
422 The actual code goes further and collects all errors ("die"s, 546 The actual code goes further and collects all errors ("die"s,
423 exceptions) that occured during request processing. The "result" method 547 exceptions) that occured during request processing. The "result" method
424 detects wether an exception as thrown (it is stored inside the $txn 548 detects whether an exception as thrown (it is stored inside the $txn
425 object) and just throws the exception, which means connection errors and 549 object) and just throws the exception, which means connection errors and
426 other problems get reported tot he code that tries to use the result, 550 other problems get reported tot he code that tries to use the result,
427 not in a random callback. 551 not in a random callback.
428 552
429 All of this enables the following usage styles: 553 All of this enables the following usage styles:

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines