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25 25
26Libev supports select, poll, the linux-specific epoll and the bsd-specific 26Libev supports select, poll, the linux-specific epoll and the bsd-specific
27kqueue mechanisms for file descriptor events, relative timers, absolute 27kqueue mechanisms for file descriptor events, relative timers, absolute
28timers with customised rescheduling, signal events, process status change 28timers with customised rescheduling, signal events, process status change
29events (related to SIGCHLD), and event watchers dealing with the event 29events (related to SIGCHLD), and event watchers dealing with the event
30loop mechanism itself (idle, prepare and check watchers). 30loop mechanism itself (idle, prepare and check watchers). It also is quite
31fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing
32it to libevent for example).
31 33
32=head1 CONVENTIONS 34=head1 CONVENTIONS
33 35
34Libev is very configurable. In this manual the default configuration 36Libev is very configurable. In this manual the default configuration
35will be described, which supports multiple event loops. For more info 37will be described, which supports multiple event loops. For more info
36about various configuraiton options please have a look at the file 38about various configuration options please have a look at the file
37F<README.embed> in the libev distribution. If libev was configured without 39F<README.embed> in the libev distribution. If libev was configured without
38support for multiple event loops, then all functions taking an initial 40support for multiple event loops, then all functions taking an initial
39argument of name C<loop> (which is always of type C<struct ev_loop *>) 41argument of name C<loop> (which is always of type C<struct ev_loop *>)
40will not have this argument. 42will not have this argument.
41 43
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61you linked against by calling the functions C<ev_version_major> and 63you linked against by calling the functions C<ev_version_major> and
62C<ev_version_minor>. If you want, you can compare against the global 64C<ev_version_minor>. If you want, you can compare against the global
63symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 65symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
64version of the library your program was compiled against. 66version of the library your program was compiled against.
65 67
66Usually, its a good idea to terminate if the major versions mismatch, 68Usually, it's a good idea to terminate if the major versions mismatch,
67as this indicates an incompatible change. Minor versions are usually 69as this indicates an incompatible change. Minor versions are usually
68compatible to older versions, so a larger minor version alone is usually 70compatible to older versions, so a larger minor version alone is usually
69not a problem. 71not a problem.
70 72
71=item ev_set_allocator (void *(*cb)(void *ptr, long size)) 73=item ev_set_allocator (void *(*cb)(void *ptr, long size))
72 74
73Sets the allocation function to use (the prototype is similar to the 75Sets the allocation function to use (the prototype is similar to the
74realloc function). It is used to allocate and free memory (no surprises 76realloc C function, the semantics are identical). It is used to allocate
75here). If it returns zero when memory needs to be allocated, the library 77and free memory (no surprises here). If it returns zero when memory
76might abort or take some potentially destructive action. The default is 78needs to be allocated, the library might abort or take some potentially
77your system realloc function. 79destructive action. The default is your system realloc function.
78 80
79You could override this function in high-availability programs to, say, 81You could override this function in high-availability programs to, say,
80free some memory if it cannot allocate memory, to use a special allocator, 82free some memory if it cannot allocate memory, to use a special allocator,
81or even to sleep a while and retry until some memory is available. 83or even to sleep a while and retry until some memory is available.
82 84
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84 86
85Set the callback function to call on a retryable syscall error (such 87Set the callback function to call on a retryable syscall error (such
86as failed select, poll, epoll_wait). The message is a printable string 88as failed select, poll, epoll_wait). The message is a printable string
87indicating the system call or subsystem causing the problem. If this 89indicating the system call or subsystem causing the problem. If this
88callback is set, then libev will expect it to remedy the sitution, no 90callback is set, then libev will expect it to remedy the sitution, no
89matter what, when it returns. That is, libev will geenrally retry the 91matter what, when it returns. That is, libev will generally retry the
90requested operation, or, if the condition doesn't go away, do bad stuff 92requested operation, or, if the condition doesn't go away, do bad stuff
91(such as abort). 93(such as abort).
92 94
93=back 95=back
94 96
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98types of such loops, the I<default> loop, which supports signals and child 100types of such loops, the I<default> loop, which supports signals and child
99events, and dynamically created loops which do not. 101events, and dynamically created loops which do not.
100 102
101If you use threads, a common model is to run the default event loop 103If you use threads, a common model is to run the default event loop
102in your main thread (or in a separate thrad) and for each thread you 104in your main thread (or in a separate thrad) and for each thread you
103create, you also create another event loop. Libev itself does no lockign 105create, you also create another event loop. Libev itself does no locking
104whatsoever, so if you mix calls to different event loops, make sure you 106whatsoever, so if you mix calls to the same event loop in different
105lock (this is usually a bad idea, though, even if done right). 107threads, make sure you lock (this is usually a bad idea, though, even if
108done correctly, because it's hideous and inefficient).
106 109
107=over 4 110=over 4
108 111
109=item struct ev_loop *ev_default_loop (unsigned int flags) 112=item struct ev_loop *ev_default_loop (unsigned int flags)
110 113
… …
115 118
116If you don't know what event loop to use, use the one returned from this 119If you don't know what event loop to use, use the one returned from this
117function. 120function.
118 121
119The flags argument can be used to specify special behaviour or specific 122The flags argument can be used to specify special behaviour or specific
120backends to use, and is usually specified as 0 (or EVFLAG_AUTO) 123backends to use, and is usually specified as 0 (or EVFLAG_AUTO).
121 124
122It supports the following flags: 125It supports the following flags:
123 126
124=over 4 127=over 4
125 128
126=item EVFLAG_AUTO 129=item C<EVFLAG_AUTO>
127 130
128The default flags value. Use this if you have no clue (its the right 131The default flags value. Use this if you have no clue (it's the right
129thing, believe me). 132thing, believe me).
130 133
131=item EVFLAG_NOENV 134=item C<EVFLAG_NOENV>
132 135
133If this flag bit is ored into the flag value then libev will I<not> look 136If this flag bit is ored into the flag value (or the program runs setuid
134at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this 137or setgid) then libev will I<not> look at the environment variable
135environment variable will override the flags completely. This is useful 138C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139override the flags completely if it is found in the environment. This is
136to try out specific backends to tets their performance, or to work around 140useful to try out specific backends to test their performance, or to work
137bugs. 141around bugs.
138 142
139=item EVMETHOD_SELECT portable select backend 143=item C<EVMETHOD_SELECT> (portable select backend)
140 144
141=item EVMETHOD_POLL poll backend (everywhere except windows) 145=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)
142 146
143=item EVMETHOD_EPOLL linux only 147=item C<EVMETHOD_EPOLL> (linux only)
144 148
145=item EVMETHOD_KQUEUE some bsds only 149=item C<EVMETHOD_KQUEUE> (some bsds only)
146 150
147=item EVMETHOD_DEVPOLL solaris 8 only 151=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
148 152
149=item EVMETHOD_PORT solaris 10 only 153=item C<EVMETHOD_PORT> (solaris 10 only)
150 154
151If one or more of these are ored into the flags value, then only these 155If one or more of these are ored into the flags value, then only these
152backends will be tried (in the reverse order as given here). If one are 156backends will be tried (in the reverse order as given here). If one are
153specified, any backend will do. 157specified, any backend will do.
154 158
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163 167
164=item ev_default_destroy () 168=item ev_default_destroy ()
165 169
166Destroys the default loop again (frees all memory and kernel state 170Destroys the default loop again (frees all memory and kernel state
167etc.). This stops all registered event watchers (by not touching them in 171etc.). This stops all registered event watchers (by not touching them in
168any way whatsoever, although you cnanot rely on this :). 172any way whatsoever, although you cannot rely on this :).
169 173
170=item ev_loop_destroy (loop) 174=item ev_loop_destroy (loop)
171 175
172Like C<ev_default_destroy>, but destroys an event loop created by an 176Like C<ev_default_destroy>, but destroys an event loop created by an
173earlier call to C<ev_loop_new>. 177earlier call to C<ev_loop_new>.
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181 185
182You I<must> call this function after forking if and only if you want to 186You I<must> call this function after forking if and only if you want to
183use the event library in both processes. If you just fork+exec, you don't 187use the event library in both processes. If you just fork+exec, you don't
184have to call it. 188have to call it.
185 189
186The function itself is quite fast and its usually not a problem to call 190The function itself is quite fast and it's usually not a problem to call
187it just in case after a fork. To make this easy, the function will fit in 191it just in case after a fork. To make this easy, the function will fit in
188quite nicely into a call to C<pthread_atfork>: 192quite nicely into a call to C<pthread_atfork>:
189 193
190 pthread_atfork (0, 0, ev_default_fork); 194 pthread_atfork (0, 0, ev_default_fork);
191 195
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198=item unsigned int ev_method (loop) 202=item unsigned int ev_method (loop)
199 203
200Returns one of the C<EVMETHOD_*> flags indicating the event backend in 204Returns one of the C<EVMETHOD_*> flags indicating the event backend in
201use. 205use.
202 206
203=item ev_tstamp = ev_now (loop) 207=item ev_tstamp ev_now (loop)
204 208
205Returns the current "event loop time", which is the time the event loop 209Returns the current "event loop time", which is the time the event loop
206got events and started processing them. This timestamp does not change 210got events and started processing them. This timestamp does not change
207as long as callbacks are being processed, and this is also the base time 211as long as callbacks are being processed, and this is also the base time
208used for relative timers. You can treat it as the timestamp of the event 212used for relative timers. You can treat it as the timestamp of the event
… …
217If the flags argument is specified as 0, it will not return until either 221If the flags argument is specified as 0, it will not return until either
218no event watchers are active anymore or C<ev_unloop> was called. 222no event watchers are active anymore or C<ev_unloop> was called.
219 223
220A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle 224A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
221those events and any outstanding ones, but will not block your process in 225those events and any outstanding ones, but will not block your process in
222case there are no events. 226case there are no events and will return after one iteration of the loop.
223 227
224A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if 228A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
225neccessary) and will handle those and any outstanding ones. It will block 229neccessary) and will handle those and any outstanding ones. It will block
226your process until at least one new event arrives. 230your process until at least one new event arrives, and will return after
231one iteration of the loop.
227 232
228This flags value could be used to implement alternative looping 233This flags value could be used to implement alternative looping
229constructs, but the C<prepare> and C<check> watchers provide a better and 234constructs, but the C<prepare> and C<check> watchers provide a better and
230more generic mechanism. 235more generic mechanism.
231 236
232=item ev_unloop (loop, how) 237=item ev_unloop (loop, how)
233 238
234Can be used to make a call to C<ev_loop> return early. The C<how> argument 239Can be used to make a call to C<ev_loop> return early (but only after it
240has processed all outstanding events). The C<how> argument must be either
235must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> 241C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or
236call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> 242C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
237calls return.
238 243
239=item ev_ref (loop) 244=item ev_ref (loop)
240 245
241=item ev_unref (loop) 246=item ev_unref (loop)
242 247
243Ref/unref can be used to add or remove a refcount on the event loop: Every 248Ref/unref can be used to add or remove a reference count on the event
244watcher keeps one reference. If you have a long-runing watcher you never 249loop: Every watcher keeps one reference, and as long as the reference
245unregister that should not keep ev_loop from running, ev_unref() after 250count is nonzero, C<ev_loop> will not return on its own. If you have
246starting, and ev_ref() before stopping it. Libev itself uses this for 251a watcher you never unregister that should not keep C<ev_loop> from
247example for its internal signal pipe: It is not visible to you as a user 252returning, ev_unref() after starting, and ev_ref() before stopping it. For
248and should not keep C<ev_loop> from exiting if the work is done. It is 253example, libev itself uses this for its internal signal pipe: It is not
249also an excellent way to do this for generic recurring timers or from 254visible to the libev user and should not keep C<ev_loop> from exiting if
250within third-party libraries. Just remember to unref after start and ref 255no event watchers registered by it are active. It is also an excellent
251before stop. 256way to do this for generic recurring timers or from within third-party
257libraries. Just remember to I<unref after start> and I<ref before stop>.
252 258
253=back 259=back
254 260
255=head1 ANATOMY OF A WATCHER 261=head1 ANATOMY OF A WATCHER
256 262
257A watcher is a structure that you create and register to record your 263A watcher is a structure that you create and register to record your
258interest in some event. For instance, if you want to wait for STDIN to 264interest in some event. For instance, if you want to wait for STDIN to
259become readable, you would create an ev_io watcher for that: 265become readable, you would create an C<ev_io> watcher for that:
260 266
261 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 267 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
262 { 268 {
263 ev_io_stop (w); 269 ev_io_stop (w);
264 ev_unloop (loop, EVUNLOOP_ALL); 270 ev_unloop (loop, EVUNLOOP_ALL);
… …
293 299
294As long as your watcher is active (has been started but not stopped) you 300As long as your watcher is active (has been started but not stopped) you
295must not touch the values stored in it. Most specifically you must never 301must not touch the values stored in it. Most specifically you must never
296reinitialise it or call its set method. 302reinitialise it or call its set method.
297 303
298You cna check whether an event is active by calling the C<ev_is_active 304You can check whether an event is active by calling the C<ev_is_active
299(watcher *)> macro. To see whether an event is outstanding (but the 305(watcher *)> macro. To see whether an event is outstanding (but the
300callback for it has not been called yet) you cna use the C<ev_is_pending 306callback for it has not been called yet) you can use the C<ev_is_pending
301(watcher *)> macro. 307(watcher *)> macro.
302 308
303Each and every callback receives the event loop pointer as first, the 309Each and every callback receives the event loop pointer as first, the
304registered watcher structure as second, and a bitset of received events as 310registered watcher structure as second, and a bitset of received events as
305third argument. 311third argument.
306 312
307The rceeived events usually include a single bit per event type received 313The received events usually include a single bit per event type received
308(you can receive multiple events at the same time). The possible bit masks 314(you can receive multiple events at the same time). The possible bit masks
309are: 315are:
310 316
311=over 4 317=over 4
312 318
313=item EV_READ 319=item C<EV_READ>
314 320
315=item EV_WRITE 321=item C<EV_WRITE>
316 322
317The file descriptor in the ev_io watcher has become readable and/or 323The file descriptor in the C<ev_io> watcher has become readable and/or
318writable. 324writable.
319 325
320=item EV_TIMEOUT 326=item C<EV_TIMEOUT>
321 327
322The ev_timer watcher has timed out. 328The C<ev_timer> watcher has timed out.
323 329
324=item EV_PERIODIC 330=item C<EV_PERIODIC>
325 331
326The ev_periodic watcher has timed out. 332The C<ev_periodic> watcher has timed out.
327 333
328=item EV_SIGNAL 334=item C<EV_SIGNAL>
329 335
330The signal specified in the ev_signal watcher has been received by a thread. 336The signal specified in the C<ev_signal> watcher has been received by a thread.
331 337
332=item EV_CHILD 338=item C<EV_CHILD>
333 339
334The pid specified in the ev_child watcher has received a status change. 340The pid specified in the C<ev_child> watcher has received a status change.
335 341
336=item EV_IDLE 342=item C<EV_IDLE>
337 343
338The ev_idle watcher has determined that you have nothing better to do. 344The C<ev_idle> watcher has determined that you have nothing better to do.
339 345
340=item EV_PREPARE 346=item C<EV_PREPARE>
341 347
342=item EV_CHECK 348=item C<EV_CHECK>
343 349
344All ev_prepare watchers are invoked just I<before> C<ev_loop> starts 350All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
345to gather new events, and all ev_check watchers are invoked just after 351to gather new events, and all C<ev_check> watchers are invoked just after
346C<ev_loop> has gathered them, but before it invokes any callbacks for any 352C<ev_loop> has gathered them, but before it invokes any callbacks for any
347received events. Callbacks of both watcher types can start and stop as 353received events. Callbacks of both watcher types can start and stop as
348many watchers as they want, and all of them will be taken into account 354many watchers as they want, and all of them will be taken into account
349(for example, a ev_prepare watcher might start an idle watcher to keep 355(for example, a C<ev_prepare> watcher might start an idle watcher to keep
350C<ev_loop> from blocking). 356C<ev_loop> from blocking).
351 357
352=item EV_ERROR 358=item C<EV_ERROR>
353 359
354An unspecified error has occured, the watcher has been stopped. This might 360An unspecified error has occured, the watcher has been stopped. This might
355happen because the watcher could not be properly started because libev 361happen because the watcher could not be properly started because libev
356ran out of memory, a file descriptor was found to be closed or any other 362ran out of memory, a file descriptor was found to be closed or any other
357problem. You best act on it by reporting the problem and somehow coping 363problem. You best act on it by reporting the problem and somehow coping
… …
366=back 372=back
367 373
368=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 374=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
369 375
370Each watcher has, by default, a member C<void *data> that you can change 376Each watcher has, by default, a member C<void *data> that you can change
371and read at any time, libev will completely ignore it. This cna be used 377and read at any time, libev will completely ignore it. This can be used
372to associate arbitrary data with your watcher. If you need more data and 378to associate arbitrary data with your watcher. If you need more data and
373don't want to allocate memory and store a pointer to it in that data 379don't want to allocate memory and store a pointer to it in that data
374member, you can also "subclass" the watcher type and provide your own 380member, you can also "subclass" the watcher type and provide your own
375data: 381data:
376 382
… …
398=head1 WATCHER TYPES 404=head1 WATCHER TYPES
399 405
400This section describes each watcher in detail, but will not repeat 406This section describes each watcher in detail, but will not repeat
401information given in the last section. 407information given in the last section.
402 408
403=head2 struct ev_io - is my file descriptor readable or writable 409=head2 C<ev_io> - is this file descriptor readable or writable
404 410
405I/O watchers check whether a file descriptor is readable or writable 411I/O watchers check whether a file descriptor is readable or writable
406in each iteration of the event loop (This behaviour is called 412in each iteration of the event loop (This behaviour is called
407level-triggering because you keep receiving events as long as the 413level-triggering because you keep receiving events as long as the
408condition persists. Remember you cna stop the watcher if you don't want to 414condition persists. Remember you can stop the watcher if you don't want to
409act on the event and neither want to receive future events). 415act on the event and neither want to receive future events).
410 416
417In general you can register as many read and/or write event watchers oer
418fd as you want (as long as you don't confuse yourself). Setting all file
419descriptors to non-blocking mode is also usually a good idea (but not
420required if you know what you are doing).
421
422You have to be careful with dup'ed file descriptors, though. Some backends
423(the linux epoll backend is a notable example) cannot handle dup'ed file
424descriptors correctly if you register interest in two or more fds pointing
425to the same file/socket etc. description.
426
427If you must do this, then force the use of a known-to-be-good backend
428(at the time of this writing, this includes only EVMETHOD_SELECT and
429EVMETHOD_POLL).
430
411=over 4 431=over 4
412 432
413=item ev_io_init (ev_io *, callback, int fd, int events) 433=item ev_io_init (ev_io *, callback, int fd, int events)
414 434
415=item ev_io_set (ev_io *, int fd, int events) 435=item ev_io_set (ev_io *, int fd, int events)
416 436
417Configures an ev_io watcher. The fd is the file descriptor to rceeive 437Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
418events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ | 438events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
419EV_WRITE> to receive the given events. 439EV_WRITE> to receive the given events.
420 440
421=back 441=back
422 442
423=head2 struct ev_timer - relative and optionally recurring timeouts 443=head2 C<ev_timer> - relative and optionally recurring timeouts
424 444
425Timer watchers are simple relative timers that generate an event after a 445Timer watchers are simple relative timers that generate an event after a
426given time, and optionally repeating in regular intervals after that. 446given time, and optionally repeating in regular intervals after that.
427 447
428The timers are based on real time, that is, if you register an event that 448The timers are based on real time, that is, if you register an event that
429times out after an hour and youreset your system clock to last years 449times out after an hour and youreset your system clock to last years
430time, it will still time out after (roughly) and hour. "Roughly" because 450time, it will still time out after (roughly) and hour. "Roughly" because
431detecting time jumps is hard, and soem inaccuracies are unavoidable (the 451detecting time jumps is hard, and soem inaccuracies are unavoidable (the
432monotonic clock option helps a lot here). 452monotonic clock option helps a lot here).
433 453
454The relative timeouts are calculated relative to the C<ev_now ()>
455time. This is usually the right thing as this timestamp refers to the time
456of the event triggering whatever timeout you are modifying/starting. If
457you suspect event processing to be delayed and you *need* to base the timeout
458ion the current time, use something like this to adjust for this:
459
460 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
461
434=over 4 462=over 4
435 463
436=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 464=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
437 465
438=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) 466=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
… …
460 488
461This sounds a bit complicated, but here is a useful and typical 489This sounds a bit complicated, but here is a useful and typical
462example: Imagine you have a tcp connection and you want a so-called idle 490example: Imagine you have a tcp connection and you want a so-called idle
463timeout, that is, you want to be called when there have been, say, 60 491timeout, that is, you want to be called when there have been, say, 60
464seconds of inactivity on the socket. The easiest way to do this is to 492seconds of inactivity on the socket. The easiest way to do this is to
465configure an ev_timer with after=repeat=60 and calling ev_timer_again each 493configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
466time you successfully read or write some data. If you go into an idle 494time you successfully read or write some data. If you go into an idle
467state where you do not expect data to travel on the socket, you can stop 495state where you do not expect data to travel on the socket, you can stop
468the timer, and again will automatically restart it if need be. 496the timer, and again will automatically restart it if need be.
469 497
470=back 498=back
471 499
472=head2 ev_periodic - to cron or not to cron it 500=head2 C<ev_periodic> - to cron or not to cron
473 501
474Periodic watchers are also timers of a kind, but they are very versatile 502Periodic watchers are also timers of a kind, but they are very versatile
475(and unfortunately a bit complex). 503(and unfortunately a bit complex).
476 504
477Unlike ev_timer's, they are not based on real time (or relative time) 505Unlike C<ev_timer>'s, they are not based on real time (or relative time)
478but on wallclock time (absolute time). You can tell a periodic watcher 506but on wallclock time (absolute time). You can tell a periodic watcher
479to trigger "at" some specific point in time. For example, if you tell a 507to trigger "at" some specific point in time. For example, if you tell a
480periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 508periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
481+ 10.>) and then reset your system clock to the last year, then it will 509+ 10.>) and then reset your system clock to the last year, then it will
482take a year to trigger the event (unlike an ev_timer, which would trigger 510take a year to trigger the event (unlike an C<ev_timer>, which would trigger
483roughly 10 seconds later and of course not if you reset your system time 511roughly 10 seconds later and of course not if you reset your system time
484again). 512again).
485 513
486They can also be used to implement vastly more complex timers, such as 514They can also be used to implement vastly more complex timers, such as
487triggering an event on eahc midnight, local time. 515triggering an event on eahc midnight, local time.
… …
516 544
517 ev_periodic_set (&periodic, 0., 3600., 0); 545 ev_periodic_set (&periodic, 0., 3600., 0);
518 546
519This doesn't mean there will always be 3600 seconds in between triggers, 547This doesn't mean there will always be 3600 seconds in between triggers,
520but only that the the callback will be called when the system time shows a 548but only that the the callback will be called when the system time shows a
521full hour (UTC), or more correct, when the system time is evenly divisible 549full hour (UTC), or more correctly, when the system time is evenly divisible
522by 3600. 550by 3600.
523 551
524Another way to think about it (for the mathematically inclined) is that 552Another way to think about it (for the mathematically inclined) is that
525ev_periodic will try to run the callback in this mode at the next possible 553C<ev_periodic> will try to run the callback in this mode at the next possible
526time where C<time = at (mod interval)>, regardless of any time jumps. 554time where C<time = at (mod interval)>, regardless of any time jumps.
527 555
528=item * manual reschedule mode (reschedule_cb = callback) 556=item * manual reschedule mode (reschedule_cb = callback)
529 557
530In this mode the values for C<interval> and C<at> are both being 558In this mode the values for C<interval> and C<at> are both being
531ignored. Instead, each time the periodic watcher gets scheduled, the 559ignored. Instead, each time the periodic watcher gets scheduled, the
532reschedule callback will be called with the watcher as first, and the 560reschedule callback will be called with the watcher as first, and the
533current time as second argument. 561current time as second argument.
534 562
535NOTE: I<This callback MUST NOT stop or destroy the periodic or any other 563NOTE: I<This callback MUST NOT stop or destroy the periodic or any other
536periodic watcher, ever, or make any event loop modificstions>. If you need 564periodic watcher, ever, or make any event loop modifications>. If you need
537to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards. 565to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.
538 566
567Also, I<< this callback must always return a time that is later than the
568passed C<now> value >>. Not even C<now> itself will be ok.
569
539Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 570Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
540ev_tstamp now)>, e.g.: 571ev_tstamp now)>, e.g.:
541 572
542 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 573 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
543 { 574 {
544 return now + 60.; 575 return now + 60.;
… …
563a different time than the last time it was called (e.g. in a crond like 594a different time than the last time it was called (e.g. in a crond like
564program when the crontabs have changed). 595program when the crontabs have changed).
565 596
566=back 597=back
567 598
568=head2 ev_signal - signal me when a signal gets signalled 599=head2 C<ev_signal> - signal me when a signal gets signalled
569 600
570Signal watchers will trigger an event when the process receives a specific 601Signal watchers will trigger an event when the process receives a specific
571signal one or more times. Even though signals are very asynchronous, libev 602signal one or more times. Even though signals are very asynchronous, libev
572will try its best to deliver signals synchronously, i.e. as part of the 603will try it's best to deliver signals synchronously, i.e. as part of the
573normal event processing, like any other event. 604normal event processing, like any other event.
574 605
575You cna configure as many watchers as you like per signal. Only when the 606You can configure as many watchers as you like per signal. Only when the
576first watcher gets started will libev actually register a signal watcher 607first watcher gets started will libev actually register a signal watcher
577with the kernel (thus it coexists with your own signal handlers as long 608with the kernel (thus it coexists with your own signal handlers as long
578as you don't register any with libev). Similarly, when the last signal 609as you don't register any with libev). Similarly, when the last signal
579watcher for a signal is stopped libev will reset the signal handler to 610watcher for a signal is stopped libev will reset the signal handler to
580SIG_DFL (regardless of what it was set to before). 611SIG_DFL (regardless of what it was set to before).
… …
588Configures the watcher to trigger on the given signal number (usually one 619Configures the watcher to trigger on the given signal number (usually one
589of the C<SIGxxx> constants). 620of the C<SIGxxx> constants).
590 621
591=back 622=back
592 623
593=head2 ev_child - wait for pid status changes 624=head2 C<ev_child> - wait for pid status changes
594 625
595Child watchers trigger when your process receives a SIGCHLD in response to 626Child watchers trigger when your process receives a SIGCHLD in response to
596some child status changes (most typically when a child of yours dies). 627some child status changes (most typically when a child of yours dies).
597 628
598=over 4 629=over 4
… …
602=item ev_child_set (ev_child *, int pid) 633=item ev_child_set (ev_child *, int pid)
603 634
604Configures the watcher to wait for status changes of process C<pid> (or 635Configures the watcher to wait for status changes of process C<pid> (or
605I<any> process if C<pid> is specified as C<0>). The callback can look 636I<any> process if C<pid> is specified as C<0>). The callback can look
606at the C<rstatus> member of the C<ev_child> watcher structure to see 637at the C<rstatus> member of the C<ev_child> watcher structure to see
607the status word (use the macros from C<sys/wait.h>). The C<rpid> member 638the status word (use the macros from C<sys/wait.h> and see your systems
608contains the pid of the process causing the status change. 639C<waitpid> documentation). The C<rpid> member contains the pid of the
640process causing the status change.
609 641
610=back 642=back
611 643
612=head2 ev_idle - when you've got nothing better to do 644=head2 C<ev_idle> - when you've got nothing better to do
613 645
614Idle watchers trigger events when there are no other I/O or timer (or 646Idle watchers trigger events when there are no other events are pending
615periodic) events pending. That is, as long as your process is busy 647(prepare, check and other idle watchers do not count). That is, as long
616handling sockets or timeouts it will not be called. But when your process 648as your process is busy handling sockets or timeouts (or even signals,
617is idle all idle watchers are being called again and again - until 649imagine) it will not be triggered. But when your process is idle all idle
650watchers are being called again and again, once per event loop iteration -
618stopped, that is, or your process receives more events. 651until stopped, that is, or your process receives more events and becomes
652busy.
619 653
620The most noteworthy effect is that as long as any idle watchers are 654The most noteworthy effect is that as long as any idle watchers are
621active, the process will not block when waiting for new events. 655active, the process will not block when waiting for new events.
622 656
623Apart from keeping your process non-blocking (which is a useful 657Apart from keeping your process non-blocking (which is a useful
… …
633kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 667kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
634believe me. 668believe me.
635 669
636=back 670=back
637 671
638=head2 prepare and check - your hooks into the event loop 672=head2 C<ev_prepare> and C<ev_check> - customise your event loop
639 673
640Prepare and check watchers usually (but not always) are used in 674Prepare and check watchers are usually (but not always) used in tandem:
641tandom. Prepare watchers get invoked before the process blocks and check 675Prepare watchers get invoked before the process blocks and check watchers
642watchers afterwards. 676afterwards.
643 677
644Their main purpose is to integrate other event mechanisms into libev. This 678Their main purpose is to integrate other event mechanisms into libev. This
645could be used, for example, to track variable changes, implement your own 679could be used, for example, to track variable changes, implement your own
646watchers, integrate net-snmp or a coroutine library and lots more. 680watchers, integrate net-snmp or a coroutine library and lots more.
647 681
648This is done by examining in each prepare call which file descriptors need 682This is done by examining in each prepare call which file descriptors need
649to be watched by the other library, registering ev_io watchers for them 683to be watched by the other library, registering C<ev_io> watchers for
650and starting an ev_timer watcher for any timeouts (many libraries provide 684them and starting an C<ev_timer> watcher for any timeouts (many libraries
651just this functionality). Then, in the check watcher you check for any 685provide just this functionality). Then, in the check watcher you check for
652events that occured (by making your callbacks set soem flags for example) 686any events that occured (by checking the pending status of all watchers
653and call back into the library. 687and stopping them) and call back into the library. The I/O and timer
688callbacks will never actually be called (but must be valid neverthelles,
689because you never know, you know?).
654 690
655As another example, the perl Coro module uses these hooks to integrate 691As another example, the Perl Coro module uses these hooks to integrate
656coroutines into libev programs, by yielding to other active coroutines 692coroutines into libev programs, by yielding to other active coroutines
657during each prepare and only letting the process block if no coroutines 693during each prepare and only letting the process block if no coroutines
658are ready to run. 694are ready to run (its actually more complicated, it only runs coroutines
695with priority higher than the event loop and one lower priority once,
696using idle watchers to keep the event loop from blocking if lower-priority
697coroutines exist, thus mapping low-priority coroutines to idle/background
698tasks).
659 699
660=over 4 700=over 4
661 701
662=item ev_prepare_init (ev_prepare *, callback) 702=item ev_prepare_init (ev_prepare *, callback)
663 703
664=item ev_check_init (ev_check *, callback) 704=item ev_check_init (ev_check *, callback)
665 705
666Initialises and configures the prepare or check watcher - they have no 706Initialises and configures the prepare or check watcher - they have no
667parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 707parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
668macros, but using them is utterly, utterly pointless. 708macros, but using them is utterly, utterly and completely pointless.
669 709
670=back 710=back
671 711
672=head1 OTHER FUNCTIONS 712=head1 OTHER FUNCTIONS
673 713
674There are some other fucntions of possible interest. Described. Here. Now. 714There are some other functions of possible interest. Described. Here. Now.
675 715
676=over 4 716=over 4
677 717
678=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 718=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
679 719
… …
681callback on whichever event happens first and automatically stop both 721callback on whichever event happens first and automatically stop both
682watchers. This is useful if you want to wait for a single event on an fd 722watchers. This is useful if you want to wait for a single event on an fd
683or timeout without havign to allocate/configure/start/stop/free one or 723or timeout without havign to allocate/configure/start/stop/free one or
684more watchers yourself. 724more watchers yourself.
685 725
686If C<fd> is less than 0, then no I/O watcher will be started and events is 726If C<fd> is less than 0, then no I/O watcher will be started and events
687ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set 727is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
688will be craeted and started. 728C<events> set will be craeted and started.
689 729
690If C<timeout> is less than 0, then no timeout watcher will be 730If C<timeout> is less than 0, then no timeout watcher will be
691started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat 731started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
692= 0) will be started. 732repeat = 0) will be started. While C<0> is a valid timeout, it is of
733dubious value.
693 734
694The callback has the type C<void (*cb)(int revents, void *arg)> and 735The callback has the type C<void (*cb)(int revents, void *arg)> and gets
695gets passed an events set (normally a combination of EV_ERROR, EV_READ, 736passed an events set like normal event callbacks (with a combination of
696EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>: 737C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
738value passed to C<ev_once>:
697 739
698 static void stdin_ready (int revents, void *arg) 740 static void stdin_ready (int revents, void *arg)
699 { 741 {
700 if (revents & EV_TIMEOUT) 742 if (revents & EV_TIMEOUT)
701 /* doh, nothing entered */ 743 /* doh, nothing entered */;
702 else if (revents & EV_READ) 744 else if (revents & EV_READ)
703 /* stdin might have data for us, joy! */ 745 /* stdin might have data for us, joy! */;
704 } 746 }
705 747
706 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 748 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
707 749
708=item ev_feed_event (loop, watcher, int events) 750=item ev_feed_event (loop, watcher, int events)
709 751
710Feeds the given event set into the event loop, as if the specified event 752Feeds the given event set into the event loop, as if the specified event
711has happened for the specified watcher (which must be a pointer to an 753had happened for the specified watcher (which must be a pointer to an
712initialised but not necessarily active event watcher). 754initialised but not necessarily started event watcher).
713 755
714=item ev_feed_fd_event (loop, int fd, int revents) 756=item ev_feed_fd_event (loop, int fd, int revents)
715 757
716Feed an event on the given fd, as if a file descriptor backend detected it. 758Feed an event on the given fd, as if a file descriptor backend detected
759the given events it.
717 760
718=item ev_feed_signal_event (loop, int signum) 761=item ev_feed_signal_event (loop, int signum)
719 762
720Feed an event as if the given signal occured (loop must be the default loop!). 763Feed an event as if the given signal occured (loop must be the default loop!).
721 764

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