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26 puts ("stdin ready"); 26 puts ("stdin ready");
27 // for one-shot events, one must manually stop the watcher 27 // for one-shot events, one must manually stop the watcher
28 // with its corresponding stop function. 28 // with its corresponding stop function.
29 ev_io_stop (EV_A_ w); 29 ev_io_stop (EV_A_ w);
30 30
31 // this causes all nested ev_loop's to stop iterating 31 // this causes all nested ev_run's to stop iterating
32 ev_unloop (EV_A_ EVUNLOOP_ALL); 32 ev_break (EV_A_ EVBREAK_ALL);
33 } 33 }
34 34
35 // another callback, this time for a time-out 35 // another callback, this time for a time-out
36 static void 36 static void
37 timeout_cb (EV_P_ ev_timer *w, int revents) 37 timeout_cb (EV_P_ ev_timer *w, int revents)
38 { 38 {
39 puts ("timeout"); 39 puts ("timeout");
40 // this causes the innermost ev_loop to stop iterating 40 // this causes the innermost ev_run to stop iterating
41 ev_unloop (EV_A_ EVUNLOOP_ONE); 41 ev_break (EV_A_ EVBREAK_ONE);
42 } 42 }
43 43
44 int 44 int
45 main (void) 45 main (void)
46 { 46 {
47 // use the default event loop unless you have special needs 47 // use the default event loop unless you have special needs
48 struct ev_loop *loop = ev_default_loop (0); 48 struct ev_loop *loop = EV_DEFAULT;
49 49
50 // initialise an io watcher, then start it 50 // initialise an io watcher, then start it
51 // this one will watch for stdin to become readable 51 // this one will watch for stdin to become readable
52 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); 52 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53 ev_io_start (loop, &stdin_watcher); 53 ev_io_start (loop, &stdin_watcher);
56 // simple non-repeating 5.5 second timeout 56 // simple non-repeating 5.5 second timeout
57 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); 57 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58 ev_timer_start (loop, &timeout_watcher); 58 ev_timer_start (loop, &timeout_watcher);
59 59
60 // now wait for events to arrive 60 // now wait for events to arrive
61 ev_loop (loop, 0); 61 ev_run (loop, 0);
62 62
63 // unloop was called, so exit 63 // unloop was called, so exit
64 return 0; 64 return 0;
65 } 65 }
66 66
75While this document tries to be as complete as possible in documenting 75While this document tries to be as complete as possible in documenting
76libev, its usage and the rationale behind its design, it is not a tutorial 76libev, its usage and the rationale behind its design, it is not a tutorial
77on event-based programming, nor will it introduce event-based programming 77on event-based programming, nor will it introduce event-based programming
78with libev. 78with libev.
79 79
80Familarity with event based programming techniques in general is assumed 80Familiarity with event based programming techniques in general is assumed
81throughout this document. 81throughout this document.
82
83=head1 WHAT TO READ WHEN IN A HURRY
84
85This manual tries to be very detailed, but unfortunately, this also makes
86it very long. If you just want to know the basics of libev, I suggest
87reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
88look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
89C<ev_timer> sections in L<WATCHER TYPES>.
82 90
83=head1 ABOUT LIBEV 91=head1 ABOUT LIBEV
84 92
85Libev is an event loop: you register interest in certain events (such as a 93Libev is an event loop: you register interest in certain events (such as a
86file descriptor being readable or a timeout occurring), and it will manage 94file descriptor being readable or a timeout occurring), and it will manage
118Libev is very configurable. In this manual the default (and most common) 126Libev is very configurable. In this manual the default (and most common)
119configuration will be described, which supports multiple event loops. For 127configuration will be described, which supports multiple event loops. For
120more info about various configuration options please have a look at 128more info about various configuration options please have a look at
121B<EMBED> section in this manual. If libev was configured without support 129B<EMBED> section in this manual. If libev was configured without support
122for multiple event loops, then all functions taking an initial argument of 130for multiple event loops, then all functions taking an initial argument of
123name C<loop> (which is always of type C<ev_loop *>) will not have 131name C<loop> (which is always of type C<struct ev_loop *>) will not have
124this argument. 132this argument.
125 133
126=head2 TIME REPRESENTATION 134=head2 TIME REPRESENTATION
127 135
128Libev represents time as a single floating point number, representing 136Libev represents time as a single floating point number, representing
129the (fractional) number of seconds since the (POSIX) epoch (somewhere 137the (fractional) number of seconds since the (POSIX) epoch (in practice
130near the beginning of 1970, details are complicated, don't ask). This 138somewhere near the beginning of 1970, details are complicated, don't
131type is called C<ev_tstamp>, which is what you should use too. It usually 139ask). This type is called C<ev_tstamp>, which is what you should use
132aliases to the C<double> type in C. When you need to do any calculations 140too. It usually aliases to the C<double> type in C. When you need to do
133on it, you should treat it as some floating point value. Unlike the name 141any calculations on it, you should treat it as some floating point value.
142
134component C<stamp> might indicate, it is also used for time differences 143Unlike the name component C<stamp> might indicate, it is also used for
135throughout libev. 144time differences (e.g. delays) throughout libev.
136 145
137=head1 ERROR HANDLING 146=head1 ERROR HANDLING
138 147
139Libev knows three classes of errors: operating system errors, usage errors 148Libev knows three classes of errors: operating system errors, usage errors
140and internal errors (bugs). 149and internal errors (bugs).
164 173
165=item ev_tstamp ev_time () 174=item ev_tstamp ev_time ()
166 175
167Returns the current time as libev would use it. Please note that the 176Returns the current time as libev would use it. Please note that the
168C<ev_now> function is usually faster and also often returns the timestamp 177C<ev_now> function is usually faster and also often returns the timestamp
169you actually want to know. 178you actually want to know. Also interesting is the combination of
179C<ev_update_now> and C<ev_now>.
170 180
171=item ev_sleep (ev_tstamp interval) 181=item ev_sleep (ev_tstamp interval)
172 182
173Sleep for the given interval: The current thread will be blocked until 183Sleep for the given interval: The current thread will be blocked until
174either it is interrupted or the given time interval has passed. Basically 184either it is interrupted or the given time interval has passed. Basically
191as this indicates an incompatible change. Minor versions are usually 201as this indicates an incompatible change. Minor versions are usually
192compatible to older versions, so a larger minor version alone is usually 202compatible to older versions, so a larger minor version alone is usually
193not a problem. 203not a problem.
194 204
195Example: Make sure we haven't accidentally been linked against the wrong 205Example: Make sure we haven't accidentally been linked against the wrong
196version. 206version (note, however, that this will not detect other ABI mismatches,
207such as LFS or reentrancy).
197 208
198 assert (("libev version mismatch", 209 assert (("libev version mismatch",
199 ev_version_major () == EV_VERSION_MAJOR 210 ev_version_major () == EV_VERSION_MAJOR
200 && ev_version_minor () >= EV_VERSION_MINOR)); 211 && ev_version_minor () >= EV_VERSION_MINOR));
201 212
212 assert (("sorry, no epoll, no sex", 223 assert (("sorry, no epoll, no sex",
213 ev_supported_backends () & EVBACKEND_EPOLL)); 224 ev_supported_backends () & EVBACKEND_EPOLL));
214 225
215=item unsigned int ev_recommended_backends () 226=item unsigned int ev_recommended_backends ()
216 227
217Return the set of all backends compiled into this binary of libev and also 228Return the set of all backends compiled into this binary of libev and
218recommended for this platform. This set is often smaller than the one 229also recommended for this platform, meaning it will work for most file
230descriptor types. This set is often smaller than the one returned by
219returned by C<ev_supported_backends>, as for example kqueue is broken on 231C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220most BSDs and will not be auto-detected unless you explicitly request it 232and will not be auto-detected unless you explicitly request it (assuming
221(assuming you know what you are doing). This is the set of backends that 233you know what you are doing). This is the set of backends that libev will
222libev will probe for if you specify no backends explicitly. 234probe for if you specify no backends explicitly.
223 235
224=item unsigned int ev_embeddable_backends () 236=item unsigned int ev_embeddable_backends ()
225 237
226Returns the set of backends that are embeddable in other event loops. This 238Returns the set of backends that are embeddable in other event loops. This
227is the theoretical, all-platform, value. To find which backends 239value is platform-specific but can include backends not available on the
228might be supported on the current system, you would need to look at 240current system. To find which embeddable backends might be supported on
229C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for 241the current system, you would need to look at C<ev_embeddable_backends ()
230recommended ones. 242& ev_supported_backends ()>, likewise for recommended ones.
231 243
232See the description of C<ev_embed> watchers for more info. 244See the description of C<ev_embed> watchers for more info.
233 245
234=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] 246=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235 247
236Sets the allocation function to use (the prototype is similar - the 248Sets the allocation function to use (the prototype is similar - the
237semantics are identical to the C<realloc> C89/SuS/POSIX function). It is 249semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238used to allocate and free memory (no surprises here). If it returns zero 250used to allocate and free memory (no surprises here). If it returns zero
239when memory needs to be allocated (C<size != 0>), the library might abort 251when memory needs to be allocated (C<size != 0>), the library might abort
265 } 277 }
266 278
267 ... 279 ...
268 ev_set_allocator (persistent_realloc); 280 ev_set_allocator (persistent_realloc);
269 281
270=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] 282=item ev_set_syserr_cb (void (*cb)(const char *msg))
271 283
272Set the callback function to call on a retryable system call error (such 284Set the callback function to call on a retryable system call error (such
273as failed select, poll, epoll_wait). The message is a printable string 285as failed select, poll, epoll_wait). The message is a printable string
274indicating the system call or subsystem causing the problem. If this 286indicating the system call or subsystem causing the problem. If this
275callback is set, then libev will expect it to remedy the situation, no 287callback is set, then libev will expect it to remedy the situation, no
289 ... 301 ...
290 ev_set_syserr_cb (fatal_error); 302 ev_set_syserr_cb (fatal_error);
291 303
292=back 304=back
293 305
294=head1 FUNCTIONS CONTROLLING THE EVENT LOOP 306=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295 307
296An event loop is described by a C<struct ev_loop *> (the C<struct> 308An event loop is described by a C<struct ev_loop *> (the C<struct> is
297is I<not> optional in this case, as there is also an C<ev_loop> 309I<not> optional in this case unless libev 3 compatibility is disabled, as
298I<function>). 310libev 3 had an C<ev_loop> function colliding with the struct name).
299 311
300The library knows two types of such loops, the I<default> loop, which 312The library knows two types of such loops, the I<default> loop, which
301supports signals and child events, and dynamically created loops which do 313supports child process events, and dynamically created event loops which
302not. 314do not.
303 315
304=over 4 316=over 4
305 317
306=item struct ev_loop *ev_default_loop (unsigned int flags) 318=item struct ev_loop *ev_default_loop (unsigned int flags)
307 319
308This will initialise the default event loop if it hasn't been initialised 320This returns the "default" event loop object, which is what you should
309yet and return it. If the default loop could not be initialised, returns 321normally use when you just need "the event loop". Event loop objects and
310false. If it already was initialised it simply returns it (and ignores the 322the C<flags> parameter are described in more detail in the entry for
311flags. If that is troubling you, check C<ev_backend ()> afterwards). 323C<ev_loop_new>.
324
325If the default loop is already initialised then this function simply
326returns it (and ignores the flags. If that is troubling you, check
327C<ev_backend ()> afterwards). Otherwise it will create it with the given
328flags, which should almost always be C<0>, unless the caller is also the
329one calling C<ev_run> or otherwise qualifies as "the main program".
312 330
313If you don't know what event loop to use, use the one returned from this 331If you don't know what event loop to use, use the one returned from this
314function. 332function (or via the C<EV_DEFAULT> macro).
315 333
316Note that this function is I<not> thread-safe, so if you want to use it 334Note that this function is I<not> thread-safe, so if you want to use it
317from multiple threads, you have to lock (note also that this is unlikely, 335from multiple threads, you have to employ some kind of mutex (note also
318as loops cannot be shared easily between threads anyway). 336that this case is unlikely, as loops cannot be shared easily between
337threads anyway).
319 338
320The default loop is the only loop that can handle C<ev_signal> and 339The default loop is the only loop that can handle C<ev_child> watchers,
321C<ev_child> watchers, and to do this, it always registers a handler 340and to do this, it always registers a handler for C<SIGCHLD>. If this is
322for C<SIGCHLD>. If this is a problem for your application you can either 341a problem for your application you can either create a dynamic loop with
323create a dynamic loop with C<ev_loop_new> that doesn't do that, or you 342C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324can simply overwrite the C<SIGCHLD> signal handler I<after> calling 343C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325C<ev_default_init>. 344
345Example: This is the most typical usage.
346
347 if (!ev_default_loop (0))
348 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
349
350Example: Restrict libev to the select and poll backends, and do not allow
351environment settings to be taken into account:
352
353 ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
354
355=item struct ev_loop *ev_loop_new (unsigned int flags)
356
357This will create and initialise a new event loop object. If the loop
358could not be initialised, returns false.
359
360This function is thread-safe, and one common way to use libev with
361threads is indeed to create one loop per thread, and using the default
362loop in the "main" or "initial" thread.
326 363
327The flags argument can be used to specify special behaviour or specific 364The flags argument can be used to specify special behaviour or specific
328backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). 365backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329 366
330The following flags are supported: 367The following flags are supported:
345useful to try out specific backends to test their performance, or to work 382useful to try out specific backends to test their performance, or to work
346around bugs. 383around bugs.
347 384
348=item C<EVFLAG_FORKCHECK> 385=item C<EVFLAG_FORKCHECK>
349 386
350Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after 387Instead of calling C<ev_loop_fork> manually after a fork, you can also
351a fork, you can also make libev check for a fork in each iteration by 388make libev check for a fork in each iteration by enabling this flag.
352enabling this flag.
353 389
354This works by calling C<getpid ()> on every iteration of the loop, 390This works by calling C<getpid ()> on every iteration of the loop,
355and thus this might slow down your event loop if you do a lot of loop 391and thus this might slow down your event loop if you do a lot of loop
356iterations and little real work, but is usually not noticeable (on my 392iterations and little real work, but is usually not noticeable (on my
357GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence 393GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
366environment variable. 402environment variable.
367 403
368=item C<EVFLAG_NOINOTIFY> 404=item C<EVFLAG_NOINOTIFY>
369 405
370When this flag is specified, then libev will not attempt to use the 406When this flag is specified, then libev will not attempt to use the
371I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and 407I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372testing, this flag can be useful to conserve inotify file descriptors, as 408testing, this flag can be useful to conserve inotify file descriptors, as
373otherwise each loop using C<ev_stat> watchers consumes one inotify handle. 409otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374 410
375=item C<EVFLAG_NOSIGNALFD> 411=item C<EVFLAG_SIGNALFD>
376 412
377When this flag is specified, then libev will not attempt to use the 413When this flag is specified, then libev will attempt to use the
378I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is 414I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379probably only useful to work around any bugs in libev. Consequently, this 415delivers signals synchronously, which makes it both faster and might make
380flag might go away once the signalfd functionality is considered stable, 416it possible to get the queued signal data. It can also simplify signal
381so it's useful mostly in environment variables and not in program code. 417handling with threads, as long as you properly block signals in your
418threads that are not interested in handling them.
419
420Signalfd will not be used by default as this changes your signal mask, and
421there are a lot of shoddy libraries and programs (glib's threadpool for
422example) that can't properly initialise their signal masks.
382 423
383=item C<EVBACKEND_SELECT> (value 1, portable select backend) 424=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384 425
385This is your standard select(2) backend. Not I<completely> standard, as 426This is your standard select(2) backend. Not I<completely> standard, as
386libev tries to roll its own fd_set with no limits on the number of fds, 427libev tries to roll its own fd_set with no limits on the number of fds,
411This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and 452This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
412C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. 453C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
413 454
414=item C<EVBACKEND_EPOLL> (value 4, Linux) 455=item C<EVBACKEND_EPOLL> (value 4, Linux)
415 456
457Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
458kernels).
459
416For few fds, this backend is a bit little slower than poll and select, 460For few fds, this backend is a bit little slower than poll and select,
417but it scales phenomenally better. While poll and select usually scale 461but it scales phenomenally better. While poll and select usually scale
418like O(total_fds) where n is the total number of fds (or the highest fd), 462like O(total_fds) where n is the total number of fds (or the highest fd),
419epoll scales either O(1) or O(active_fds). 463epoll scales either O(1) or O(active_fds).
420 464
421The epoll mechanism deserves honorable mention as the most misdesigned 465The epoll mechanism deserves honorable mention as the most misdesigned
422of the more advanced event mechanisms: mere annoyances include silently 466of the more advanced event mechanisms: mere annoyances include silently
423dropping file descriptors, requiring a system call per change per file 467dropping file descriptors, requiring a system call per change per file
424descriptor (and unnecessary guessing of parameters), problems with dup and 468descriptor (and unnecessary guessing of parameters), problems with dup,
469returning before the timeout value, resulting in additional iterations
470(and only giving 5ms accuracy while select on the same platform gives
425so on. The biggest issue is fork races, however - if a program forks then 4710.1ms) and so on. The biggest issue is fork races, however - if a program
426I<both> parent and child process have to recreate the epoll set, which can 472forks then I<both> parent and child process have to recreate the epoll
427take considerable time (one syscall per file descriptor) and is of course 473set, which can take considerable time (one syscall per file descriptor)
428hard to detect. 474and is of course hard to detect.
429 475
430Epoll is also notoriously buggy - embedding epoll fds I<should> work, but 476Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
431of course I<doesn't>, and epoll just loves to report events for totally 477of course I<doesn't>, and epoll just loves to report events for totally
432I<different> file descriptors (even already closed ones, so one cannot 478I<different> file descriptors (even already closed ones, so one cannot
433even remove them from the set) than registered in the set (especially 479even remove them from the set) than registered in the set (especially
434on SMP systems). Libev tries to counter these spurious notifications by 480on SMP systems). Libev tries to counter these spurious notifications by
435employing an additional generation counter and comparing that against the 481employing an additional generation counter and comparing that against the
436events to filter out spurious ones, recreating the set when required. 482events to filter out spurious ones, recreating the set when required. Last
483not least, it also refuses to work with some file descriptors which work
484perfectly fine with C<select> (files, many character devices...).
485
486Epoll is truly the train wreck analog among event poll mechanisms.
437 487
438While stopping, setting and starting an I/O watcher in the same iteration 488While stopping, setting and starting an I/O watcher in the same iteration
439will result in some caching, there is still a system call per such 489will result in some caching, there is still a system call per such
440incident (because the same I<file descriptor> could point to a different 490incident (because the same I<file descriptor> could point to a different
441I<file description> now), so its best to avoid that. Also, C<dup ()>'ed 491I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
539If one or more of the backend flags are or'ed into the flags value, 589If one or more of the backend flags are or'ed into the flags value,
540then only these backends will be tried (in the reverse order as listed 590then only these backends will be tried (in the reverse order as listed
541here). If none are specified, all backends in C<ev_recommended_backends 591here). If none are specified, all backends in C<ev_recommended_backends
542()> will be tried. 592()> will be tried.
543 593
544Example: This is the most typical usage.
545
546 if (!ev_default_loop (0))
547 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
548
549Example: Restrict libev to the select and poll backends, and do not allow
550environment settings to be taken into account:
551
552 ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
553
554Example: Use whatever libev has to offer, but make sure that kqueue is
555used if available (warning, breaks stuff, best use only with your own
556private event loop and only if you know the OS supports your types of
557fds):
558
559 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
560
561=item struct ev_loop *ev_loop_new (unsigned int flags)
562
563Similar to C<ev_default_loop>, but always creates a new event loop that is
564always distinct from the default loop. Unlike the default loop, it cannot
565handle signal and child watchers, and attempts to do so will be greeted by
566undefined behaviour (or a failed assertion if assertions are enabled).
567
568Note that this function I<is> thread-safe, and the recommended way to use
569libev with threads is indeed to create one loop per thread, and using the
570default loop in the "main" or "initial" thread.
571
572Example: Try to create a event loop that uses epoll and nothing else. 594Example: Try to create a event loop that uses epoll and nothing else.
573 595
574 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 596 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
575 if (!epoller) 597 if (!epoller)
576 fatal ("no epoll found here, maybe it hides under your chair"); 598 fatal ("no epoll found here, maybe it hides under your chair");
577 599
600Example: Use whatever libev has to offer, but make sure that kqueue is
601used if available.
602
603 struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
604
578=item ev_default_destroy () 605=item ev_loop_destroy (loop)
579 606
580Destroys the default loop again (frees all memory and kernel state 607Destroys an event loop object (frees all memory and kernel state
581etc.). None of the active event watchers will be stopped in the normal 608etc.). None of the active event watchers will be stopped in the normal
582sense, so e.g. C<ev_is_active> might still return true. It is your 609sense, so e.g. C<ev_is_active> might still return true. It is your
583responsibility to either stop all watchers cleanly yourself I<before> 610responsibility to either stop all watchers cleanly yourself I<before>
584calling this function, or cope with the fact afterwards (which is usually 611calling this function, or cope with the fact afterwards (which is usually
585the easiest thing, you can just ignore the watchers and/or C<free ()> them 612the easiest thing, you can just ignore the watchers and/or C<free ()> them
587 614
588Note that certain global state, such as signal state (and installed signal 615Note that certain global state, such as signal state (and installed signal
589handlers), will not be freed by this function, and related watchers (such 616handlers), will not be freed by this function, and related watchers (such
590as signal and child watchers) would need to be stopped manually. 617as signal and child watchers) would need to be stopped manually.
591 618
592In general it is not advisable to call this function except in the 619This function is normally used on loop objects allocated by
593rare occasion where you really need to free e.g. the signal handling 620C<ev_loop_new>, but it can also be used on the default loop returned by
621C<ev_default_loop>, in which case it is not thread-safe.
622
623Note that it is not advisable to call this function on the default loop
624except in the rare occasion where you really need to free its resources.
594pipe fds. If you need dynamically allocated loops it is better to use 625If you need dynamically allocated loops it is better to use C<ev_loop_new>
595C<ev_loop_new> and C<ev_loop_destroy>). 626and C<ev_loop_destroy>.
596 627
597=item ev_loop_destroy (loop) 628=item ev_loop_fork (loop)
598 629
599Like C<ev_default_destroy>, but destroys an event loop created by an
600earlier call to C<ev_loop_new>.
601
602=item ev_default_fork ()
603
604This function sets a flag that causes subsequent C<ev_loop> iterations 630This function sets a flag that causes subsequent C<ev_run> iterations to
605to reinitialise the kernel state for backends that have one. Despite the 631reinitialise the kernel state for backends that have one. Despite the
606name, you can call it anytime, but it makes most sense after forking, in 632name, you can call it anytime, but it makes most sense after forking, in
607the child process (or both child and parent, but that again makes little 633the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
608sense). You I<must> call it in the child before using any of the libev 634child before resuming or calling C<ev_run>.
609functions, and it will only take effect at the next C<ev_loop> iteration. 635
636Again, you I<have> to call it on I<any> loop that you want to re-use after
637a fork, I<even if you do not plan to use the loop in the parent>. This is
638because some kernel interfaces *cough* I<kqueue> *cough* do funny things
639during fork.
610 640
611On the other hand, you only need to call this function in the child 641On the other hand, you only need to call this function in the child
612process if and only if you want to use the event library in the child. If 642process if and only if you want to use the event loop in the child. If
613you just fork+exec, you don't have to call it at all. 643you just fork+exec or create a new loop in the child, you don't have to
644call it at all (in fact, C<epoll> is so badly broken that it makes a
645difference, but libev will usually detect this case on its own and do a
646costly reset of the backend).
614 647
615The function itself is quite fast and it's usually not a problem to call 648The function itself is quite fast and it's usually not a problem to call
616it just in case after a fork. To make this easy, the function will fit in 649it just in case after a fork.
617quite nicely into a call to C<pthread_atfork>:
618 650
651Example: Automate calling C<ev_loop_fork> on the default loop when
652using pthreads.
653
654 static void
655 post_fork_child (void)
656 {
657 ev_loop_fork (EV_DEFAULT);
658 }
659
660 ...
619 pthread_atfork (0, 0, ev_default_fork); 661 pthread_atfork (0, 0, post_fork_child);
620
621=item ev_loop_fork (loop)
622
623Like C<ev_default_fork>, but acts on an event loop created by
624C<ev_loop_new>. Yes, you have to call this on every allocated event loop
625after fork that you want to re-use in the child, and how you do this is
626entirely your own problem.
627 662
628=item int ev_is_default_loop (loop) 663=item int ev_is_default_loop (loop)
629 664
630Returns true when the given loop is, in fact, the default loop, and false 665Returns true when the given loop is, in fact, the default loop, and false
631otherwise. 666otherwise.
632 667
633=item unsigned int ev_loop_count (loop) 668=item unsigned int ev_iteration (loop)
634 669
635Returns the count of loop iterations for the loop, which is identical to 670Returns the current iteration count for the event loop, which is identical
636the number of times libev did poll for new events. It starts at C<0> and 671to the number of times libev did poll for new events. It starts at C<0>
637happily wraps around with enough iterations. 672and happily wraps around with enough iterations.
638 673
639This value can sometimes be useful as a generation counter of sorts (it 674This value can sometimes be useful as a generation counter of sorts (it
640"ticks" the number of loop iterations), as it roughly corresponds with 675"ticks" the number of loop iterations), as it roughly corresponds with
641C<ev_prepare> and C<ev_check> calls. 676C<ev_prepare> and C<ev_check> calls - and is incremented between the
677prepare and check phases.
642 678
643=item unsigned int ev_loop_depth (loop) 679=item unsigned int ev_depth (loop)
644 680
645Returns the number of times C<ev_loop> was entered minus the number of 681Returns the number of times C<ev_run> was entered minus the number of
646times C<ev_loop> was exited, in other words, the recursion depth. 682times C<ev_run> was exited normally, in other words, the recursion depth.
647 683
648Outside C<ev_loop>, this number is zero. In a callback, this number is 684Outside C<ev_run>, this number is zero. In a callback, this number is
649C<1>, unless C<ev_loop> was invoked recursively (or from another thread), 685C<1>, unless C<ev_run> was invoked recursively (or from another thread),
650in which case it is higher. 686in which case it is higher.
651 687
652Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread 688Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
653etc.), doesn't count as exit. 689throwing an exception etc.), doesn't count as "exit" - consider this
690as a hint to avoid such ungentleman-like behaviour unless it's really
691convenient, in which case it is fully supported.
654 692
655=item unsigned int ev_backend (loop) 693=item unsigned int ev_backend (loop)
656 694
657Returns one of the C<EVBACKEND_*> flags indicating the event backend in 695Returns one of the C<EVBACKEND_*> flags indicating the event backend in
658use. 696use.
667 705
668=item ev_now_update (loop) 706=item ev_now_update (loop)
669 707
670Establishes the current time by querying the kernel, updating the time 708Establishes the current time by querying the kernel, updating the time
671returned by C<ev_now ()> in the progress. This is a costly operation and 709returned by C<ev_now ()> in the progress. This is a costly operation and
672is usually done automatically within C<ev_loop ()>. 710is usually done automatically within C<ev_run ()>.
673 711
674This function is rarely useful, but when some event callback runs for a 712This function is rarely useful, but when some event callback runs for a
675very long time without entering the event loop, updating libev's idea of 713very long time without entering the event loop, updating libev's idea of
676the current time is a good idea. 714the current time is a good idea.
677 715
679 717
680=item ev_suspend (loop) 718=item ev_suspend (loop)
681 719
682=item ev_resume (loop) 720=item ev_resume (loop)
683 721
684These two functions suspend and resume a loop, for use when the loop is 722These two functions suspend and resume an event loop, for use when the
685not used for a while and timeouts should not be processed. 723loop is not used for a while and timeouts should not be processed.
686 724
687A typical use case would be an interactive program such as a game: When 725A typical use case would be an interactive program such as a game: When
688the user presses C<^Z> to suspend the game and resumes it an hour later it 726the user presses C<^Z> to suspend the game and resumes it an hour later it
689would be best to handle timeouts as if no time had actually passed while 727would be best to handle timeouts as if no time had actually passed while
690the program was suspended. This can be achieved by calling C<ev_suspend> 728the program was suspended. This can be achieved by calling C<ev_suspend>
692C<ev_resume> directly afterwards to resume timer processing. 730C<ev_resume> directly afterwards to resume timer processing.
693 731
694Effectively, all C<ev_timer> watchers will be delayed by the time spend 732Effectively, all C<ev_timer> watchers will be delayed by the time spend
695between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers 733between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
696will be rescheduled (that is, they will lose any events that would have 734will be rescheduled (that is, they will lose any events that would have
697occured while suspended). 735occurred while suspended).
698 736
699After calling C<ev_suspend> you B<must not> call I<any> function on the 737After calling C<ev_suspend> you B<must not> call I<any> function on the
700given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> 738given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
701without a previous call to C<ev_suspend>. 739without a previous call to C<ev_suspend>.
702 740
703Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the 741Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
704event loop time (see C<ev_now_update>). 742event loop time (see C<ev_now_update>).
705 743
706=item ev_loop (loop, int flags) 744=item ev_run (loop, int flags)
707 745
708Finally, this is it, the event handler. This function usually is called 746Finally, this is it, the event handler. This function usually is called
709after you initialised all your watchers and you want to start handling 747after you have initialised all your watchers and you want to start
710events. 748handling events. It will ask the operating system for any new events, call
749the watcher callbacks, an then repeat the whole process indefinitely: This
750is why event loops are called I<loops>.
711 751
712If the flags argument is specified as C<0>, it will not return until 752If the flags argument is specified as C<0>, it will keep handling events
713either no event watchers are active anymore or C<ev_unloop> was called. 753until either no event watchers are active anymore or C<ev_break> was
754called.
714 755
715Please note that an explicit C<ev_unloop> is usually better than 756Please note that an explicit C<ev_break> is usually better than
716relying on all watchers to be stopped when deciding when a program has 757relying on all watchers to be stopped when deciding when a program has
717finished (especially in interactive programs), but having a program 758finished (especially in interactive programs), but having a program
718that automatically loops as long as it has to and no longer by virtue 759that automatically loops as long as it has to and no longer by virtue
719of relying on its watchers stopping correctly, that is truly a thing of 760of relying on its watchers stopping correctly, that is truly a thing of
720beauty. 761beauty.
721 762
763This function is also I<mostly> exception-safe - you can break out of
764a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
765exception and so on. This does not decrement the C<ev_depth> value, nor
766will it clear any outstanding C<EVBREAK_ONE> breaks.
767
722A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle 768A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
723those events and any already outstanding ones, but will not block your 769those events and any already outstanding ones, but will not wait and
724process in case there are no events and will return after one iteration of 770block your process in case there are no events and will return after one
725the loop. 771iteration of the loop. This is sometimes useful to poll and handle new
772events while doing lengthy calculations, to keep the program responsive.
726 773
727A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if 774A flags value of C<EVRUN_ONCE> will look for new events (waiting if
728necessary) and will handle those and any already outstanding ones. It 775necessary) and will handle those and any already outstanding ones. It
729will block your process until at least one new event arrives (which could 776will block your process until at least one new event arrives (which could
730be an event internal to libev itself, so there is no guarantee that a 777be an event internal to libev itself, so there is no guarantee that a
731user-registered callback will be called), and will return after one 778user-registered callback will be called), and will return after one
732iteration of the loop. 779iteration of the loop.
733 780
734This is useful if you are waiting for some external event in conjunction 781This is useful if you are waiting for some external event in conjunction
735with something not expressible using other libev watchers (i.e. "roll your 782with something not expressible using other libev watchers (i.e. "roll your
736own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is 783own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
737usually a better approach for this kind of thing. 784usually a better approach for this kind of thing.
738 785
739Here are the gory details of what C<ev_loop> does: 786Here are the gory details of what C<ev_run> does:
740 787
788 - Increment loop depth.
789 - Reset the ev_break status.
741 - Before the first iteration, call any pending watchers. 790 - Before the first iteration, call any pending watchers.
791 LOOP:
742 * If EVFLAG_FORKCHECK was used, check for a fork. 792 - If EVFLAG_FORKCHECK was used, check for a fork.
743 - If a fork was detected (by any means), queue and call all fork watchers. 793 - If a fork was detected (by any means), queue and call all fork watchers.
744 - Queue and call all prepare watchers. 794 - Queue and call all prepare watchers.
795 - If ev_break was called, goto FINISH.
745 - If we have been forked, detach and recreate the kernel state 796 - If we have been forked, detach and recreate the kernel state
746 as to not disturb the other process. 797 as to not disturb the other process.
747 - Update the kernel state with all outstanding changes. 798 - Update the kernel state with all outstanding changes.
748 - Update the "event loop time" (ev_now ()). 799 - Update the "event loop time" (ev_now ()).
749 - Calculate for how long to sleep or block, if at all 800 - Calculate for how long to sleep or block, if at all
750 (active idle watchers, EVLOOP_NONBLOCK or not having 801 (active idle watchers, EVRUN_NOWAIT or not having
751 any active watchers at all will result in not sleeping). 802 any active watchers at all will result in not sleeping).
752 - Sleep if the I/O and timer collect interval say so. 803 - Sleep if the I/O and timer collect interval say so.
804 - Increment loop iteration counter.
753 - Block the process, waiting for any events. 805 - Block the process, waiting for any events.
754 - Queue all outstanding I/O (fd) events. 806 - Queue all outstanding I/O (fd) events.
755 - Update the "event loop time" (ev_now ()), and do time jump adjustments. 807 - Update the "event loop time" (ev_now ()), and do time jump adjustments.
756 - Queue all expired timers. 808 - Queue all expired timers.
757 - Queue all expired periodics. 809 - Queue all expired periodics.
758 - Unless any events are pending now, queue all idle watchers. 810 - Queue all idle watchers with priority higher than that of pending events.
759 - Queue all check watchers. 811 - Queue all check watchers.
760 - Call all queued watchers in reverse order (i.e. check watchers first). 812 - Call all queued watchers in reverse order (i.e. check watchers first).
761 Signals and child watchers are implemented as I/O watchers, and will 813 Signals and child watchers are implemented as I/O watchers, and will
762 be handled here by queueing them when their watcher gets executed. 814 be handled here by queueing them when their watcher gets executed.
763 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 815 - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
764 were used, or there are no active watchers, return, otherwise 816 were used, or there are no active watchers, goto FINISH, otherwise
765 continue with step *. 817 continue with step LOOP.
818 FINISH:
819 - Reset the ev_break status iff it was EVBREAK_ONE.
820 - Decrement the loop depth.
821 - Return.
766 822
767Example: Queue some jobs and then loop until no events are outstanding 823Example: Queue some jobs and then loop until no events are outstanding
768anymore. 824anymore.
769 825
770 ... queue jobs here, make sure they register event watchers as long 826 ... queue jobs here, make sure they register event watchers as long
771 ... as they still have work to do (even an idle watcher will do..) 827 ... as they still have work to do (even an idle watcher will do..)
772 ev_loop (my_loop, 0); 828 ev_run (my_loop, 0);
773 ... jobs done or somebody called unloop. yeah! 829 ... jobs done or somebody called unloop. yeah!
774 830
775=item ev_unloop (loop, how) 831=item ev_break (loop, how)
776 832
777Can be used to make a call to C<ev_loop> return early (but only after it 833Can be used to make a call to C<ev_run> return early (but only after it
778has processed all outstanding events). The C<how> argument must be either 834has processed all outstanding events). The C<how> argument must be either
779C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 835C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
780C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 836C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
781 837
782This "unloop state" will be cleared when entering C<ev_loop> again. 838This "break state" will be cleared on the next call to C<ev_run>.
783 839
784It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. 840It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
841which case it will have no effect.
785 842
786=item ev_ref (loop) 843=item ev_ref (loop)
787 844
788=item ev_unref (loop) 845=item ev_unref (loop)
789 846
790Ref/unref can be used to add or remove a reference count on the event 847Ref/unref can be used to add or remove a reference count on the event
791loop: Every watcher keeps one reference, and as long as the reference 848loop: Every watcher keeps one reference, and as long as the reference
792count is nonzero, C<ev_loop> will not return on its own. 849count is nonzero, C<ev_run> will not return on its own.
793 850
794If you have a watcher you never unregister that should not keep C<ev_loop> 851This is useful when you have a watcher that you never intend to
795from returning, call ev_unref() after starting, and ev_ref() before 852unregister, but that nevertheless should not keep C<ev_run> from
853returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
796stopping it. 854before stopping it.
797 855
798As an example, libev itself uses this for its internal signal pipe: It 856As an example, libev itself uses this for its internal signal pipe: It
799is not visible to the libev user and should not keep C<ev_loop> from 857is not visible to the libev user and should not keep C<ev_run> from
800exiting if no event watchers registered by it are active. It is also an 858exiting if no event watchers registered by it are active. It is also an
801excellent way to do this for generic recurring timers or from within 859excellent way to do this for generic recurring timers or from within
802third-party libraries. Just remember to I<unref after start> and I<ref 860third-party libraries. Just remember to I<unref after start> and I<ref
803before stop> (but only if the watcher wasn't active before, or was active 861before stop> (but only if the watcher wasn't active before, or was active
804before, respectively. Note also that libev might stop watchers itself 862before, respectively. Note also that libev might stop watchers itself
805(e.g. non-repeating timers) in which case you have to C<ev_ref> 863(e.g. non-repeating timers) in which case you have to C<ev_ref>
806in the callback). 864in the callback).
807 865
808Example: Create a signal watcher, but keep it from keeping C<ev_loop> 866Example: Create a signal watcher, but keep it from keeping C<ev_run>
809running when nothing else is active. 867running when nothing else is active.
810 868
811 ev_signal exitsig; 869 ev_signal exitsig;
812 ev_signal_init (&exitsig, sig_cb, SIGINT); 870 ev_signal_init (&exitsig, sig_cb, SIGINT);
813 ev_signal_start (loop, &exitsig); 871 ev_signal_start (loop, &exitsig);
858usually doesn't make much sense to set it to a lower value than C<0.01>, 916usually doesn't make much sense to set it to a lower value than C<0.01>,
859as this approaches the timing granularity of most systems. Note that if 917as this approaches the timing granularity of most systems. Note that if
860you do transactions with the outside world and you can't increase the 918you do transactions with the outside world and you can't increase the
861parallelity, then this setting will limit your transaction rate (if you 919parallelity, then this setting will limit your transaction rate (if you
862need to poll once per transaction and the I/O collect interval is 0.01, 920need to poll once per transaction and the I/O collect interval is 0.01,
863then you can't do more than 100 transations per second). 921then you can't do more than 100 transactions per second).
864 922
865Setting the I<timeout collect interval> can improve the opportunity for 923Setting the I<timeout collect interval> can improve the opportunity for
866saving power, as the program will "bundle" timer callback invocations that 924saving power, as the program will "bundle" timer callback invocations that
867are "near" in time together, by delaying some, thus reducing the number of 925are "near" in time together, by delaying some, thus reducing the number of
868times the process sleeps and wakes up again. Another useful technique to 926times the process sleeps and wakes up again. Another useful technique to
876 ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); 934 ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
877 935
878=item ev_invoke_pending (loop) 936=item ev_invoke_pending (loop)
879 937
880This call will simply invoke all pending watchers while resetting their 938This call will simply invoke all pending watchers while resetting their
881pending state. Normally, C<ev_loop> does this automatically when required, 939pending state. Normally, C<ev_run> does this automatically when required,
882but when overriding the invoke callback this call comes handy. 940but when overriding the invoke callback this call comes handy. This
941function can be invoked from a watcher - this can be useful for example
942when you want to do some lengthy calculation and want to pass further
943event handling to another thread (you still have to make sure only one
944thread executes within C<ev_invoke_pending> or C<ev_run> of course).
883 945
884=item int ev_pending_count (loop) 946=item int ev_pending_count (loop)
885 947
886Returns the number of pending watchers - zero indicates that no watchers 948Returns the number of pending watchers - zero indicates that no watchers
887are pending. 949are pending.
888 950
889=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) 951=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
890 952
891This overrides the invoke pending functionality of the loop: Instead of 953This overrides the invoke pending functionality of the loop: Instead of
892invoking all pending watchers when there are any, C<ev_loop> will call 954invoking all pending watchers when there are any, C<ev_run> will call
893this callback instead. This is useful, for example, when you want to 955this callback instead. This is useful, for example, when you want to
894invoke the actual watchers inside another context (another thread etc.). 956invoke the actual watchers inside another context (another thread etc.).
895 957
896If you want to reset the callback, use C<ev_invoke_pending> as new 958If you want to reset the callback, use C<ev_invoke_pending> as new
897callback. 959callback.
900 962
901Sometimes you want to share the same loop between multiple threads. This 963Sometimes you want to share the same loop between multiple threads. This
902can be done relatively simply by putting mutex_lock/unlock calls around 964can be done relatively simply by putting mutex_lock/unlock calls around
903each call to a libev function. 965each call to a libev function.
904 966
905However, C<ev_loop> can run an indefinite time, so it is not feasible to 967However, C<ev_run> can run an indefinite time, so it is not feasible
906wait for it to return. One way around this is to wake up the loop via 968to wait for it to return. One way around this is to wake up the event
907C<ev_unloop> and C<av_async_send>, another way is to set these I<release> 969loop via C<ev_break> and C<av_async_send>, another way is to set these
908and I<acquire> callbacks on the loop. 970I<release> and I<acquire> callbacks on the loop.
909 971
910When set, then C<release> will be called just before the thread is 972When set, then C<release> will be called just before the thread is
911suspended waiting for new events, and C<acquire> is called just 973suspended waiting for new events, and C<acquire> is called just
912afterwards. 974afterwards.
913 975
916 978
917While event loop modifications are allowed between invocations of 979While event loop modifications are allowed between invocations of
918C<release> and C<acquire> (that's their only purpose after all), no 980C<release> and C<acquire> (that's their only purpose after all), no
919modifications done will affect the event loop, i.e. adding watchers will 981modifications done will affect the event loop, i.e. adding watchers will
920have no effect on the set of file descriptors being watched, or the time 982have no effect on the set of file descriptors being watched, or the time
921waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it 983waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
922to take note of any changes you made. 984to take note of any changes you made.
923 985
924In theory, threads executing C<ev_loop> will be async-cancel safe between 986In theory, threads executing C<ev_run> will be async-cancel safe between
925invocations of C<release> and C<acquire>. 987invocations of C<release> and C<acquire>.
926 988
927See also the locking example in the C<THREADS> section later in this 989See also the locking example in the C<THREADS> section later in this
928document. 990document.
929 991
930=item ev_set_userdata (loop, void *data) 992=item ev_set_userdata (loop, void *data)
931 993
932=item ev_userdata (loop) 994=item void *ev_userdata (loop)
933 995
934Set and retrieve a single C<void *> associated with a loop. When 996Set and retrieve a single C<void *> associated with a loop. When
935C<ev_set_userdata> has never been called, then C<ev_userdata> returns 997C<ev_set_userdata> has never been called, then C<ev_userdata> returns
936C<0.> 998C<0>.
937 999
938These two functions can be used to associate arbitrary data with a loop, 1000These two functions can be used to associate arbitrary data with a loop,
939and are intended solely for the C<invoke_pending_cb>, C<release> and 1001and are intended solely for the C<invoke_pending_cb>, C<release> and
940C<acquire> callbacks described above, but of course can be (ab-)used for 1002C<acquire> callbacks described above, but of course can be (ab-)used for
941any other purpose as well. 1003any other purpose as well.
942 1004
943=item ev_loop_verify (loop) 1005=item ev_verify (loop)
944 1006
945This function only does something when C<EV_VERIFY> support has been 1007This function only does something when C<EV_VERIFY> support has been
946compiled in, which is the default for non-minimal builds. It tries to go 1008compiled in, which is the default for non-minimal builds. It tries to go
947through all internal structures and checks them for validity. If anything 1009through all internal structures and checks them for validity. If anything
948is found to be inconsistent, it will print an error message to standard 1010is found to be inconsistent, it will print an error message to standard
959 1021
960In the following description, uppercase C<TYPE> in names stands for the 1022In the following description, uppercase C<TYPE> in names stands for the
961watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer 1023watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
962watchers and C<ev_io_start> for I/O watchers. 1024watchers and C<ev_io_start> for I/O watchers.
963 1025
964A watcher is a structure that you create and register to record your 1026A watcher is an opaque structure that you allocate and register to record
965interest in some event. For instance, if you want to wait for STDIN to 1027your interest in some event. To make a concrete example, imagine you want
966become readable, you would create an C<ev_io> watcher for that: 1028to wait for STDIN to become readable, you would create an C<ev_io> watcher
1029for that:
967 1030
968 static void my_cb (struct ev_loop *loop, ev_io *w, int revents) 1031 static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
969 { 1032 {
970 ev_io_stop (w); 1033 ev_io_stop (w);
971 ev_unloop (loop, EVUNLOOP_ALL); 1034 ev_break (loop, EVBREAK_ALL);
972 } 1035 }
973 1036
974 struct ev_loop *loop = ev_default_loop (0); 1037 struct ev_loop *loop = ev_default_loop (0);
975 1038
976 ev_io stdin_watcher; 1039 ev_io stdin_watcher;
977 1040
978 ev_init (&stdin_watcher, my_cb); 1041 ev_init (&stdin_watcher, my_cb);
979 ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); 1042 ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
980 ev_io_start (loop, &stdin_watcher); 1043 ev_io_start (loop, &stdin_watcher);
981 1044
982 ev_loop (loop, 0); 1045 ev_run (loop, 0);
983 1046
984As you can see, you are responsible for allocating the memory for your 1047As you can see, you are responsible for allocating the memory for your
985watcher structures (and it is I<usually> a bad idea to do this on the 1048watcher structures (and it is I<usually> a bad idea to do this on the
986stack). 1049stack).
987 1050
988Each watcher has an associated watcher structure (called C<struct ev_TYPE> 1051Each watcher has an associated watcher structure (called C<struct ev_TYPE>
989or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). 1052or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
990 1053
991Each watcher structure must be initialised by a call to C<ev_init 1054Each watcher structure must be initialised by a call to C<ev_init (watcher
992(watcher *, callback)>, which expects a callback to be provided. This 1055*, callback)>, which expects a callback to be provided. This callback is
993callback gets invoked each time the event occurs (or, in the case of I/O 1056invoked each time the event occurs (or, in the case of I/O watchers, each
994watchers, each time the event loop detects that the file descriptor given 1057time the event loop detects that the file descriptor given is readable
995is readable and/or writable). 1058and/or writable).
996 1059
997Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> 1060Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
998macro to configure it, with arguments specific to the watcher type. There 1061macro to configure it, with arguments specific to the watcher type. There
999is also a macro to combine initialisation and setting in one call: C<< 1062is also a macro to combine initialisation and setting in one call: C<<
1000ev_TYPE_init (watcher *, callback, ...) >>. 1063ev_TYPE_init (watcher *, callback, ...) >>.
1023=item C<EV_WRITE> 1086=item C<EV_WRITE>
1024 1087
1025The file descriptor in the C<ev_io> watcher has become readable and/or 1088The file descriptor in the C<ev_io> watcher has become readable and/or
1026writable. 1089writable.
1027 1090
1028=item C<EV_TIMEOUT> 1091=item C<EV_TIMER>
1029 1092
1030The C<ev_timer> watcher has timed out. 1093The C<ev_timer> watcher has timed out.
1031 1094
1032=item C<EV_PERIODIC> 1095=item C<EV_PERIODIC>
1033 1096
1051 1114
1052=item C<EV_PREPARE> 1115=item C<EV_PREPARE>
1053 1116
1054=item C<EV_CHECK> 1117=item C<EV_CHECK>
1055 1118
1056All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts 1119All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1057to gather new events, and all C<ev_check> watchers are invoked just after 1120to gather new events, and all C<ev_check> watchers are invoked just after
1058C<ev_loop> has gathered them, but before it invokes any callbacks for any 1121C<ev_run> has gathered them, but before it invokes any callbacks for any
1059received events. Callbacks of both watcher types can start and stop as 1122received events. Callbacks of both watcher types can start and stop as
1060many watchers as they want, and all of them will be taken into account 1123many watchers as they want, and all of them will be taken into account
1061(for example, a C<ev_prepare> watcher might start an idle watcher to keep 1124(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1062C<ev_loop> from blocking). 1125C<ev_run> from blocking).
1063 1126
1064=item C<EV_EMBED> 1127=item C<EV_EMBED>
1065 1128
1066The embedded event loop specified in the C<ev_embed> watcher needs attention. 1129The embedded event loop specified in the C<ev_embed> watcher needs attention.
1067 1130
1068=item C<EV_FORK> 1131=item C<EV_FORK>
1069 1132
1070The event loop has been resumed in the child process after fork (see 1133The event loop has been resumed in the child process after fork (see
1071C<ev_fork>). 1134C<ev_fork>).
1135
1136=item C<EV_CLEANUP>
1137
1138The event loop is about to be destroyed (see C<ev_cleanup>).
1072 1139
1073=item C<EV_ASYNC> 1140=item C<EV_ASYNC>
1074 1141
1075The given async watcher has been asynchronously notified (see C<ev_async>). 1142The given async watcher has been asynchronously notified (see C<ev_async>).
1076 1143
1123 1190
1124 ev_io w; 1191 ev_io w;
1125 ev_init (&w, my_cb); 1192 ev_init (&w, my_cb);
1126 ev_io_set (&w, STDIN_FILENO, EV_READ); 1193 ev_io_set (&w, STDIN_FILENO, EV_READ);
1127 1194
1128=item C<ev_TYPE_set> (ev_TYPE *, [args]) 1195=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129 1196
1130This macro initialises the type-specific parts of a watcher. You need to 1197This macro initialises the type-specific parts of a watcher. You need to
1131call C<ev_init> at least once before you call this macro, but you can 1198call C<ev_init> at least once before you call this macro, but you can
1132call C<ev_TYPE_set> any number of times. You must not, however, call this 1199call C<ev_TYPE_set> any number of times. You must not, however, call this
1133macro on a watcher that is active (it can be pending, however, which is a 1200macro on a watcher that is active (it can be pending, however, which is a
1146 1213
1147Example: Initialise and set an C<ev_io> watcher in one step. 1214Example: Initialise and set an C<ev_io> watcher in one step.
1148 1215
1149 ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); 1216 ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150 1217
1151=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) 1218=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152 1219
1153Starts (activates) the given watcher. Only active watchers will receive 1220Starts (activates) the given watcher. Only active watchers will receive
1154events. If the watcher is already active nothing will happen. 1221events. If the watcher is already active nothing will happen.
1155 1222
1156Example: Start the C<ev_io> watcher that is being abused as example in this 1223Example: Start the C<ev_io> watcher that is being abused as example in this
1157whole section. 1224whole section.
1158 1225
1159 ev_io_start (EV_DEFAULT_UC, &w); 1226 ev_io_start (EV_DEFAULT_UC, &w);
1160 1227
1161=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) 1228=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162 1229
1163Stops the given watcher if active, and clears the pending status (whether 1230Stops the given watcher if active, and clears the pending status (whether
1164the watcher was active or not). 1231the watcher was active or not).
1165 1232
1166It is possible that stopped watchers are pending - for example, 1233It is possible that stopped watchers are pending - for example,
1191=item ev_cb_set (ev_TYPE *watcher, callback) 1258=item ev_cb_set (ev_TYPE *watcher, callback)
1192 1259
1193Change the callback. You can change the callback at virtually any time 1260Change the callback. You can change the callback at virtually any time
1194(modulo threads). 1261(modulo threads).
1195 1262
1196=item ev_set_priority (ev_TYPE *watcher, priority) 1263=item ev_set_priority (ev_TYPE *watcher, int priority)
1197 1264
1198=item int ev_priority (ev_TYPE *watcher) 1265=item int ev_priority (ev_TYPE *watcher)
1199 1266
1200Set and query the priority of the watcher. The priority is a small 1267Set and query the priority of the watcher. The priority is a small
1201integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> 1268integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1233watcher isn't pending it does nothing and returns C<0>. 1300watcher isn't pending it does nothing and returns C<0>.
1234 1301
1235Sometimes it can be useful to "poll" a watcher instead of waiting for its 1302Sometimes it can be useful to "poll" a watcher instead of waiting for its
1236callback to be invoked, which can be accomplished with this function. 1303callback to be invoked, which can be accomplished with this function.
1237 1304
1305=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1306
1307Feeds the given event set into the event loop, as if the specified event
1308had happened for the specified watcher (which must be a pointer to an
1309initialised but not necessarily started event watcher). Obviously you must
1310not free the watcher as long as it has pending events.
1311
1312Stopping the watcher, letting libev invoke it, or calling
1313C<ev_clear_pending> will clear the pending event, even if the watcher was
1314not started in the first place.
1315
1316See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1317functions that do not need a watcher.
1318
1238=back 1319=back
1239
1240 1320
1241=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 1321=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1242 1322
1243Each watcher has, by default, a member C<void *data> that you can change 1323Each watcher has, by default, a member C<void *data> that you can change
1244and read at any time: libev will completely ignore it. This can be used 1324and read at any time: libev will completely ignore it. This can be used
1300 t2_cb (EV_P_ ev_timer *w, int revents) 1380 t2_cb (EV_P_ ev_timer *w, int revents)
1301 { 1381 {
1302 struct my_biggy big = (struct my_biggy *) 1382 struct my_biggy big = (struct my_biggy *)
1303 (((char *)w) - offsetof (struct my_biggy, t2)); 1383 (((char *)w) - offsetof (struct my_biggy, t2));
1304 } 1384 }
1385
1386=head2 WATCHER STATES
1387
1388There are various watcher states mentioned throughout this manual -
1389active, pending and so on. In this section these states and the rules to
1390transition between them will be described in more detail - and while these
1391rules might look complicated, they usually do "the right thing".
1392
1393=over 4
1394
1395=item initialiased
1396
1397Before a watcher can be registered with the event looop it has to be
1398initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1399C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1400
1401In this state it is simply some block of memory that is suitable for use
1402in an event loop. It can be moved around, freed, reused etc. at will.
1403
1404=item started/running/active
1405
1406Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1407property of the event loop, and is actively waiting for events. While in
1408this state it cannot be accessed (except in a few documented ways), moved,
1409freed or anything else - the only legal thing is to keep a pointer to it,
1410and call libev functions on it that are documented to work on active watchers.
1411
1412=item pending
1413
1414If a watcher is active and libev determines that an event it is interested
1415in has occurred (such as a timer expiring), it will become pending. It will
1416stay in this pending state until either it is stopped or its callback is
1417about to be invoked, so it is not normally pending inside the watcher
1418callback.
1419
1420The watcher might or might not be active while it is pending (for example,
1421an expired non-repeating timer can be pending but no longer active). If it
1422is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
1423but it is still property of the event loop at this time, so cannot be
1424moved, freed or reused. And if it is active the rules described in the
1425previous item still apply.
1426
1427It is also possible to feed an event on a watcher that is not active (e.g.
1428via C<ev_feed_event>), in which case it becomes pending without being
1429active.
1430
1431=item stopped
1432
1433A watcher can be stopped implicitly by libev (in which case it might still
1434be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1435latter will clear any pending state the watcher might be in, regardless
1436of whether it was active or not, so stopping a watcher explicitly before
1437freeing it is often a good idea.
1438
1439While stopped (and not pending) the watcher is essentially in the
1440initialised state, that is it can be reused, moved, modified in any way
1441you wish.
1442
1443=back
1305 1444
1306=head2 WATCHER PRIORITY MODELS 1445=head2 WATCHER PRIORITY MODELS
1307 1446
1308Many event loops support I<watcher priorities>, which are usually small 1447Many event loops support I<watcher priorities>, which are usually small
1309integers that influence the ordering of event callback invocation 1448integers that influence the ordering of event callback invocation
1352 1491
1353For example, to emulate how many other event libraries handle priorities, 1492For example, to emulate how many other event libraries handle priorities,
1354you can associate an C<ev_idle> watcher to each such watcher, and in 1493you can associate an C<ev_idle> watcher to each such watcher, and in
1355the normal watcher callback, you just start the idle watcher. The real 1494the normal watcher callback, you just start the idle watcher. The real
1356processing is done in the idle watcher callback. This causes libev to 1495processing is done in the idle watcher callback. This causes libev to
1357continously poll and process kernel event data for the watcher, but when 1496continuously poll and process kernel event data for the watcher, but when
1358the lock-out case is known to be rare (which in turn is rare :), this is 1497the lock-out case is known to be rare (which in turn is rare :), this is
1359workable. 1498workable.
1360 1499
1361Usually, however, the lock-out model implemented that way will perform 1500Usually, however, the lock-out model implemented that way will perform
1362miserably under the type of load it was designed to handle. In that case, 1501miserably under the type of load it was designed to handle. In that case,
1376 { 1515 {
1377 // stop the I/O watcher, we received the event, but 1516 // stop the I/O watcher, we received the event, but
1378 // are not yet ready to handle it. 1517 // are not yet ready to handle it.
1379 ev_io_stop (EV_A_ w); 1518 ev_io_stop (EV_A_ w);
1380 1519
1381 // start the idle watcher to ahndle the actual event. 1520 // start the idle watcher to handle the actual event.
1382 // it will not be executed as long as other watchers 1521 // it will not be executed as long as other watchers
1383 // with the default priority are receiving events. 1522 // with the default priority are receiving events.
1384 ev_idle_start (EV_A_ &idle); 1523 ev_idle_start (EV_A_ &idle);
1385 } 1524 }
1386 1525
1440 1579
1441If you cannot use non-blocking mode, then force the use of a 1580If you cannot use non-blocking mode, then force the use of a
1442known-to-be-good backend (at the time of this writing, this includes only 1581known-to-be-good backend (at the time of this writing, this includes only
1443C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file 1582C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1444descriptors for which non-blocking operation makes no sense (such as 1583descriptors for which non-blocking operation makes no sense (such as
1445files) - libev doesn't guarentee any specific behaviour in that case. 1584files) - libev doesn't guarantee any specific behaviour in that case.
1446 1585
1447Another thing you have to watch out for is that it is quite easy to 1586Another thing you have to watch out for is that it is quite easy to
1448receive "spurious" readiness notifications, that is your callback might 1587receive "spurious" readiness notifications, that is your callback might
1449be called with C<EV_READ> but a subsequent C<read>(2) will actually block 1588be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1450because there is no data. Not only are some backends known to create a 1589because there is no data. Not only are some backends known to create a
1515 1654
1516So when you encounter spurious, unexplained daemon exits, make sure you 1655So when you encounter spurious, unexplained daemon exits, make sure you
1517ignore SIGPIPE (and maybe make sure you log the exit status of your daemon 1656ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1518somewhere, as that would have given you a big clue). 1657somewhere, as that would have given you a big clue).
1519 1658
1659=head3 The special problem of accept()ing when you can't
1660
1661Many implementations of the POSIX C<accept> function (for example,
1662found in post-2004 Linux) have the peculiar behaviour of not removing a
1663connection from the pending queue in all error cases.
1664
1665For example, larger servers often run out of file descriptors (because
1666of resource limits), causing C<accept> to fail with C<ENFILE> but not
1667rejecting the connection, leading to libev signalling readiness on
1668the next iteration again (the connection still exists after all), and
1669typically causing the program to loop at 100% CPU usage.
1670
1671Unfortunately, the set of errors that cause this issue differs between
1672operating systems, there is usually little the app can do to remedy the
1673situation, and no known thread-safe method of removing the connection to
1674cope with overload is known (to me).
1675
1676One of the easiest ways to handle this situation is to just ignore it
1677- when the program encounters an overload, it will just loop until the
1678situation is over. While this is a form of busy waiting, no OS offers an
1679event-based way to handle this situation, so it's the best one can do.
1680
1681A better way to handle the situation is to log any errors other than
1682C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
1683messages, and continue as usual, which at least gives the user an idea of
1684what could be wrong ("raise the ulimit!"). For extra points one could stop
1685the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
1686usage.
1687
1688If your program is single-threaded, then you could also keep a dummy file
1689descriptor for overload situations (e.g. by opening F</dev/null>), and
1690when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
1691close that fd, and create a new dummy fd. This will gracefully refuse
1692clients under typical overload conditions.
1693
1694The last way to handle it is to simply log the error and C<exit>, as
1695is often done with C<malloc> failures, but this results in an easy
1696opportunity for a DoS attack.
1520 1697
1521=head3 Watcher-Specific Functions 1698=head3 Watcher-Specific Functions
1522 1699
1523=over 4 1700=over 4
1524 1701
1556 ... 1733 ...
1557 struct ev_loop *loop = ev_default_init (0); 1734 struct ev_loop *loop = ev_default_init (0);
1558 ev_io stdin_readable; 1735 ev_io stdin_readable;
1559 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1736 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1560 ev_io_start (loop, &stdin_readable); 1737 ev_io_start (loop, &stdin_readable);
1561 ev_loop (loop, 0); 1738 ev_run (loop, 0);
1562 1739
1563 1740
1564=head2 C<ev_timer> - relative and optionally repeating timeouts 1741=head2 C<ev_timer> - relative and optionally repeating timeouts
1565 1742
1566Timer watchers are simple relative timers that generate an event after a 1743Timer watchers are simple relative timers that generate an event after a
1575The callback is guaranteed to be invoked only I<after> its timeout has 1752The callback is guaranteed to be invoked only I<after> its timeout has
1576passed (not I<at>, so on systems with very low-resolution clocks this 1753passed (not I<at>, so on systems with very low-resolution clocks this
1577might introduce a small delay). If multiple timers become ready during the 1754might introduce a small delay). If multiple timers become ready during the
1578same loop iteration then the ones with earlier time-out values are invoked 1755same loop iteration then the ones with earlier time-out values are invoked
1579before ones of the same priority with later time-out values (but this is 1756before ones of the same priority with later time-out values (but this is
1580no longer true when a callback calls C<ev_loop> recursively). 1757no longer true when a callback calls C<ev_run> recursively).
1581 1758
1582=head3 Be smart about timeouts 1759=head3 Be smart about timeouts
1583 1760
1584Many real-world problems involve some kind of timeout, usually for error 1761Many real-world problems involve some kind of timeout, usually for error
1585recovery. A typical example is an HTTP request - if the other side hangs, 1762recovery. A typical example is an HTTP request - if the other side hangs,
1671 ev_tstamp timeout = last_activity + 60.; 1848 ev_tstamp timeout = last_activity + 60.;
1672 1849
1673 // if last_activity + 60. is older than now, we did time out 1850 // if last_activity + 60. is older than now, we did time out
1674 if (timeout < now) 1851 if (timeout < now)
1675 { 1852 {
1676 // timeout occured, take action 1853 // timeout occurred, take action
1677 } 1854 }
1678 else 1855 else
1679 { 1856 {
1680 // callback was invoked, but there was some activity, re-arm 1857 // callback was invoked, but there was some activity, re-arm
1681 // the watcher to fire in last_activity + 60, which is 1858 // the watcher to fire in last_activity + 60, which is
1703to the current time (meaning we just have some activity :), then call the 1880to the current time (meaning we just have some activity :), then call the
1704callback, which will "do the right thing" and start the timer: 1881callback, which will "do the right thing" and start the timer:
1705 1882
1706 ev_init (timer, callback); 1883 ev_init (timer, callback);
1707 last_activity = ev_now (loop); 1884 last_activity = ev_now (loop);
1708 callback (loop, timer, EV_TIMEOUT); 1885 callback (loop, timer, EV_TIMER);
1709 1886
1710And when there is some activity, simply store the current time in 1887And when there is some activity, simply store the current time in
1711C<last_activity>, no libev calls at all: 1888C<last_activity>, no libev calls at all:
1712 1889
1713 last_actiivty = ev_now (loop); 1890 last_activity = ev_now (loop);
1714 1891
1715This technique is slightly more complex, but in most cases where the 1892This technique is slightly more complex, but in most cases where the
1716time-out is unlikely to be triggered, much more efficient. 1893time-out is unlikely to be triggered, much more efficient.
1717 1894
1718Changing the timeout is trivial as well (if it isn't hard-coded in the 1895Changing the timeout is trivial as well (if it isn't hard-coded in the
1756 1933
1757=head3 The special problem of time updates 1934=head3 The special problem of time updates
1758 1935
1759Establishing the current time is a costly operation (it usually takes at 1936Establishing the current time is a costly operation (it usually takes at
1760least two system calls): EV therefore updates its idea of the current 1937least two system calls): EV therefore updates its idea of the current
1761time only before and after C<ev_loop> collects new events, which causes a 1938time only before and after C<ev_run> collects new events, which causes a
1762growing difference between C<ev_now ()> and C<ev_time ()> when handling 1939growing difference between C<ev_now ()> and C<ev_time ()> when handling
1763lots of events in one iteration. 1940lots of events in one iteration.
1764 1941
1765The relative timeouts are calculated relative to the C<ev_now ()> 1942The relative timeouts are calculated relative to the C<ev_now ()>
1766time. This is usually the right thing as this timestamp refers to the time 1943time. This is usually the right thing as this timestamp refers to the time
1837C<repeat> value), or reset the running timer to the C<repeat> value. 2014C<repeat> value), or reset the running timer to the C<repeat> value.
1838 2015
1839This sounds a bit complicated, see L<Be smart about timeouts>, above, for a 2016This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1840usage example. 2017usage example.
1841 2018
1842=item ev_timer_remaining (loop, ev_timer *) 2019=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843 2020
1844Returns the remaining time until a timer fires. If the timer is active, 2021Returns the remaining time until a timer fires. If the timer is active,
1845then this time is relative to the current event loop time, otherwise it's 2022then this time is relative to the current event loop time, otherwise it's
1846the timeout value currently configured. 2023the timeout value currently configured.
1847 2024
1848That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns 2025That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1849C<5>. When the timer is started and one second passes, C<ev_timer_remain> 2026C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1850will return C<4>. When the timer expires and is restarted, it will return 2027will return C<4>. When the timer expires and is restarted, it will return
1851roughly C<7> (likely slightly less as callback invocation takes some time, 2028roughly C<7> (likely slightly less as callback invocation takes some time,
1852too), and so on. 2029too), and so on.
1853 2030
1854=item ev_tstamp repeat [read-write] 2031=item ev_tstamp repeat [read-write]
1883 } 2060 }
1884 2061
1885 ev_timer mytimer; 2062 ev_timer mytimer;
1886 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ 2063 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1887 ev_timer_again (&mytimer); /* start timer */ 2064 ev_timer_again (&mytimer); /* start timer */
1888 ev_loop (loop, 0); 2065 ev_run (loop, 0);
1889 2066
1890 // and in some piece of code that gets executed on any "activity": 2067 // and in some piece of code that gets executed on any "activity":
1891 // reset the timeout to start ticking again at 10 seconds 2068 // reset the timeout to start ticking again at 10 seconds
1892 ev_timer_again (&mytimer); 2069 ev_timer_again (&mytimer);
1893 2070
1919 2096
1920As with timers, the callback is guaranteed to be invoked only when the 2097As with timers, the callback is guaranteed to be invoked only when the
1921point in time where it is supposed to trigger has passed. If multiple 2098point in time where it is supposed to trigger has passed. If multiple
1922timers become ready during the same loop iteration then the ones with 2099timers become ready during the same loop iteration then the ones with
1923earlier time-out values are invoked before ones with later time-out values 2100earlier time-out values are invoked before ones with later time-out values
1924(but this is no longer true when a callback calls C<ev_loop> recursively). 2101(but this is no longer true when a callback calls C<ev_run> recursively).
1925 2102
1926=head3 Watcher-Specific Functions and Data Members 2103=head3 Watcher-Specific Functions and Data Members
1927 2104
1928=over 4 2105=over 4
1929 2106
2057Example: Call a callback every hour, or, more precisely, whenever the 2234Example: Call a callback every hour, or, more precisely, whenever the
2058system time is divisible by 3600. The callback invocation times have 2235system time is divisible by 3600. The callback invocation times have
2059potentially a lot of jitter, but good long-term stability. 2236potentially a lot of jitter, but good long-term stability.
2060 2237
2061 static void 2238 static void
2062 clock_cb (struct ev_loop *loop, ev_io *w, int revents) 2239 clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2063 { 2240 {
2064 ... its now a full hour (UTC, or TAI or whatever your clock follows) 2241 ... its now a full hour (UTC, or TAI or whatever your clock follows)
2065 } 2242 }
2066 2243
2067 ev_periodic hourly_tick; 2244 ev_periodic hourly_tick;
2090 2267
2091=head2 C<ev_signal> - signal me when a signal gets signalled! 2268=head2 C<ev_signal> - signal me when a signal gets signalled!
2092 2269
2093Signal watchers will trigger an event when the process receives a specific 2270Signal watchers will trigger an event when the process receives a specific
2094signal one or more times. Even though signals are very asynchronous, libev 2271signal one or more times. Even though signals are very asynchronous, libev
2095will try it's best to deliver signals synchronously, i.e. as part of the 2272will try its best to deliver signals synchronously, i.e. as part of the
2096normal event processing, like any other event. 2273normal event processing, like any other event.
2097 2274
2098If you want signals to be delivered truly asynchronously, just use 2275If you want signals to be delivered truly asynchronously, just use
2099C<sigaction> as you would do without libev and forget about sharing 2276C<sigaction> as you would do without libev and forget about sharing
2100the signal. You can even use C<ev_async> from a signal handler to 2277the signal. You can even use C<ev_async> from a signal handler to
2114C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should 2291C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2115not be unduly interrupted. If you have a problem with system calls getting 2292not be unduly interrupted. If you have a problem with system calls getting
2116interrupted by signals you can block all signals in an C<ev_check> watcher 2293interrupted by signals you can block all signals in an C<ev_check> watcher
2117and unblock them in an C<ev_prepare> watcher. 2294and unblock them in an C<ev_prepare> watcher.
2118 2295
2119=head3 The special problem of inheritance over execve 2296=head3 The special problem of inheritance over fork/execve/pthread_create
2120 2297
2121Both the signal mask (C<sigprocmask>) and the signal disposition 2298Both the signal mask (C<sigprocmask>) and the signal disposition
2122(C<sigaction>) are unspecified after starting a signal watcher (and after 2299(C<sigaction>) are unspecified after starting a signal watcher (and after
2123stopping it again), that is, libev might or might not block the signal, 2300stopping it again), that is, libev might or might not block the signal,
2124and might or might not set or restore the installed signal handler. 2301and might or might not set or restore the installed signal handler.
2125 2302
2126While this does not matter for the signal disposition (libev never 2303While this does not matter for the signal disposition (libev never
2127sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on 2304sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2128C<execve>), this matters for the signal mask: many programs do not expect 2305C<execve>), this matters for the signal mask: many programs do not expect
2129many signals to be blocked. 2306certain signals to be blocked.
2130 2307
2131This means that before calling C<exec> (from the child) you should reset 2308This means that before calling C<exec> (from the child) you should reset
2132the signal mask to whatever "default" you expect (all clear is a good 2309the signal mask to whatever "default" you expect (all clear is a good
2133choice usually). 2310choice usually).
2134 2311
2312The simplest way to ensure that the signal mask is reset in the child is
2313to install a fork handler with C<pthread_atfork> that resets it. That will
2314catch fork calls done by libraries (such as the libc) as well.
2315
2316In current versions of libev, the signal will not be blocked indefinitely
2317unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2318the window of opportunity for problems, it will not go away, as libev
2319I<has> to modify the signal mask, at least temporarily.
2320
2321So I can't stress this enough: I<If you do not reset your signal mask when
2322you expect it to be empty, you have a race condition in your code>. This
2323is not a libev-specific thing, this is true for most event libraries.
2324
2135=head3 Watcher-Specific Functions and Data Members 2325=head3 Watcher-Specific Functions and Data Members
2136 2326
2137=over 4 2327=over 4
2138 2328
2139=item ev_signal_init (ev_signal *, callback, int signum) 2329=item ev_signal_init (ev_signal *, callback, int signum)
2154Example: Try to exit cleanly on SIGINT. 2344Example: Try to exit cleanly on SIGINT.
2155 2345
2156 static void 2346 static void
2157 sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) 2347 sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2158 { 2348 {
2159 ev_unloop (loop, EVUNLOOP_ALL); 2349 ev_break (loop, EVBREAK_ALL);
2160 } 2350 }
2161 2351
2162 ev_signal signal_watcher; 2352 ev_signal signal_watcher;
2163 ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 2353 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2164 ev_signal_start (loop, &signal_watcher); 2354 ev_signal_start (loop, &signal_watcher);
2550 2740
2551Prepare and check watchers are usually (but not always) used in pairs: 2741Prepare and check watchers are usually (but not always) used in pairs:
2552prepare watchers get invoked before the process blocks and check watchers 2742prepare watchers get invoked before the process blocks and check watchers
2553afterwards. 2743afterwards.
2554 2744
2555You I<must not> call C<ev_loop> or similar functions that enter 2745You I<must not> call C<ev_run> or similar functions that enter
2556the current event loop from either C<ev_prepare> or C<ev_check> 2746the current event loop from either C<ev_prepare> or C<ev_check>
2557watchers. Other loops than the current one are fine, however. The 2747watchers. Other loops than the current one are fine, however. The
2558rationale behind this is that you do not need to check for recursion in 2748rationale behind this is that you do not need to check for recursion in
2559those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, 2749those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2560C<ev_check> so if you have one watcher of each kind they will always be 2750C<ev_check> so if you have one watcher of each kind they will always be
2728 2918
2729 if (timeout >= 0) 2919 if (timeout >= 0)
2730 // create/start timer 2920 // create/start timer
2731 2921
2732 // poll 2922 // poll
2733 ev_loop (EV_A_ 0); 2923 ev_run (EV_A_ 0);
2734 2924
2735 // stop timer again 2925 // stop timer again
2736 if (timeout >= 0) 2926 if (timeout >= 0)
2737 ev_timer_stop (EV_A_ &to); 2927 ev_timer_stop (EV_A_ &to);
2738 2928
2816if you do not want that, you need to temporarily stop the embed watcher). 3006if you do not want that, you need to temporarily stop the embed watcher).
2817 3007
2818=item ev_embed_sweep (loop, ev_embed *) 3008=item ev_embed_sweep (loop, ev_embed *)
2819 3009
2820Make a single, non-blocking sweep over the embedded loop. This works 3010Make a single, non-blocking sweep over the embedded loop. This works
2821similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most 3011similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2822appropriate way for embedded loops. 3012appropriate way for embedded loops.
2823 3013
2824=item struct ev_loop *other [read-only] 3014=item struct ev_loop *other [read-only]
2825 3015
2826The embedded event loop. 3016The embedded event loop.
2886C<ev_default_fork> cheats and calls it in the wrong process, the fork 3076C<ev_default_fork> cheats and calls it in the wrong process, the fork
2887handlers will be invoked, too, of course. 3077handlers will be invoked, too, of course.
2888 3078
2889=head3 The special problem of life after fork - how is it possible? 3079=head3 The special problem of life after fork - how is it possible?
2890 3080
2891Most uses of C<fork()> consist of forking, then some simple calls to ste 3081Most uses of C<fork()> consist of forking, then some simple calls to set
2892up/change the process environment, followed by a call to C<exec()>. This 3082up/change the process environment, followed by a call to C<exec()>. This
2893sequence should be handled by libev without any problems. 3083sequence should be handled by libev without any problems.
2894 3084
2895This changes when the application actually wants to do event handling 3085This changes when the application actually wants to do event handling
2896in the child, or both parent in child, in effect "continuing" after the 3086in the child, or both parent in child, in effect "continuing" after the
2912disadvantage of having to use multiple event loops (which do not support 3102disadvantage of having to use multiple event loops (which do not support
2913signal watchers). 3103signal watchers).
2914 3104
2915When this is not possible, or you want to use the default loop for 3105When this is not possible, or you want to use the default loop for
2916other reasons, then in the process that wants to start "fresh", call 3106other reasons, then in the process that wants to start "fresh", call
2917C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying 3107C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2918the default loop will "orphan" (not stop) all registered watchers, so you 3108Destroying the default loop will "orphan" (not stop) all registered
2919have to be careful not to execute code that modifies those watchers. Note 3109watchers, so you have to be careful not to execute code that modifies
2920also that in that case, you have to re-register any signal watchers. 3110those watchers. Note also that in that case, you have to re-register any
3111signal watchers.
2921 3112
2922=head3 Watcher-Specific Functions and Data Members 3113=head3 Watcher-Specific Functions and Data Members
2923 3114
2924=over 4 3115=over 4
2925 3116
2926=item ev_fork_init (ev_signal *, callback) 3117=item ev_fork_init (ev_fork *, callback)
2927 3118
2928Initialises and configures the fork watcher - it has no parameters of any 3119Initialises and configures the fork watcher - it has no parameters of any
2929kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, 3120kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2930believe me. 3121really.
2931 3122
2932=back 3123=back
2933 3124
2934 3125
3126=head2 C<ev_cleanup> - even the best things end
3127
3128Cleanup watchers are called just before the event loop is being destroyed
3129by a call to C<ev_loop_destroy>.
3130
3131While there is no guarantee that the event loop gets destroyed, cleanup
3132watchers provide a convenient method to install cleanup hooks for your
3133program, worker threads and so on - you just to make sure to destroy the
3134loop when you want them to be invoked.
3135
3136Cleanup watchers are invoked in the same way as any other watcher. Unlike
3137all other watchers, they do not keep a reference to the event loop (which
3138makes a lot of sense if you think about it). Like all other watchers, you
3139can call libev functions in the callback, except C<ev_cleanup_start>.
3140
3141=head3 Watcher-Specific Functions and Data Members
3142
3143=over 4
3144
3145=item ev_cleanup_init (ev_cleanup *, callback)
3146
3147Initialises and configures the cleanup watcher - it has no parameters of
3148any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
3149pointless, I assure you.
3150
3151=back
3152
3153Example: Register an atexit handler to destroy the default loop, so any
3154cleanup functions are called.
3155
3156 static void
3157 program_exits (void)
3158 {
3159 ev_loop_destroy (EV_DEFAULT_UC);
3160 }
3161
3162 ...
3163 atexit (program_exits);
3164
3165
2935=head2 C<ev_async> - how to wake up another event loop 3166=head2 C<ev_async> - how to wake up an event loop
2936 3167
2937In general, you cannot use an C<ev_loop> from multiple threads or other 3168In general, you cannot use an C<ev_run> from multiple threads or other
2938asynchronous sources such as signal handlers (as opposed to multiple event 3169asynchronous sources such as signal handlers (as opposed to multiple event
2939loops - those are of course safe to use in different threads). 3170loops - those are of course safe to use in different threads).
2940 3171
2941Sometimes, however, you need to wake up another event loop you do not 3172Sometimes, however, you need to wake up an event loop you do not control,
2942control, for example because it belongs to another thread. This is what 3173for example because it belongs to another thread. This is what C<ev_async>
2943C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you 3174watchers do: as long as the C<ev_async> watcher is active, you can signal
2944can signal it by calling C<ev_async_send>, which is thread- and signal 3175it by calling C<ev_async_send>, which is thread- and signal safe.
2945safe.
2946 3176
2947This functionality is very similar to C<ev_signal> watchers, as signals, 3177This functionality is very similar to C<ev_signal> watchers, as signals,
2948too, are asynchronous in nature, and signals, too, will be compressed 3178too, are asynchronous in nature, and signals, too, will be compressed
2949(i.e. the number of callback invocations may be less than the number of 3179(i.e. the number of callback invocations may be less than the number of
2950C<ev_async_sent> calls). 3180C<ev_async_sent> calls).
2955=head3 Queueing 3185=head3 Queueing
2956 3186
2957C<ev_async> does not support queueing of data in any way. The reason 3187C<ev_async> does not support queueing of data in any way. The reason
2958is that the author does not know of a simple (or any) algorithm for a 3188is that the author does not know of a simple (or any) algorithm for a
2959multiple-writer-single-reader queue that works in all cases and doesn't 3189multiple-writer-single-reader queue that works in all cases and doesn't
2960need elaborate support such as pthreads. 3190need elaborate support such as pthreads or unportable memory access
3191semantics.
2961 3192
2962That means that if you want to queue data, you have to provide your own 3193That means that if you want to queue data, you have to provide your own
2963queue. But at least I can tell you how to implement locking around your 3194queue. But at least I can tell you how to implement locking around your
2964queue: 3195queue:
2965 3196
3104 3335
3105If C<timeout> is less than 0, then no timeout watcher will be 3336If C<timeout> is less than 0, then no timeout watcher will be
3106started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 3337started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3107repeat = 0) will be started. C<0> is a valid timeout. 3338repeat = 0) will be started. C<0> is a valid timeout.
3108 3339
3109The callback has the type C<void (*cb)(int revents, void *arg)> and gets 3340The callback has the type C<void (*cb)(int revents, void *arg)> and is
3110passed an C<revents> set like normal event callbacks (a combination of 3341passed an C<revents> set like normal event callbacks (a combination of
3111C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> 3342C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3112value passed to C<ev_once>. Note that it is possible to receive I<both> 3343value passed to C<ev_once>. Note that it is possible to receive I<both>
3113a timeout and an io event at the same time - you probably should give io 3344a timeout and an io event at the same time - you probably should give io
3114events precedence. 3345events precedence.
3115 3346
3116Example: wait up to ten seconds for data to appear on STDIN_FILENO. 3347Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3117 3348
3118 static void stdin_ready (int revents, void *arg) 3349 static void stdin_ready (int revents, void *arg)
3119 { 3350 {
3120 if (revents & EV_READ) 3351 if (revents & EV_READ)
3121 /* stdin might have data for us, joy! */; 3352 /* stdin might have data for us, joy! */;
3122 else if (revents & EV_TIMEOUT) 3353 else if (revents & EV_TIMER)
3123 /* doh, nothing entered */; 3354 /* doh, nothing entered */;
3124 } 3355 }
3125 3356
3126 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3357 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3127 3358
3128=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3129
3130Feeds the given event set into the event loop, as if the specified event
3131had happened for the specified watcher (which must be a pointer to an
3132initialised but not necessarily started event watcher).
3133
3134=item ev_feed_fd_event (struct ev_loop *, int fd, int revents) 3359=item ev_feed_fd_event (loop, int fd, int revents)
3135 3360
3136Feed an event on the given fd, as if a file descriptor backend detected 3361Feed an event on the given fd, as if a file descriptor backend detected
3137the given events it. 3362the given events it.
3138 3363
3139=item ev_feed_signal_event (struct ev_loop *loop, int signum) 3364=item ev_feed_signal_event (loop, int signum)
3140 3365
3141Feed an event as if the given signal occurred (C<loop> must be the default 3366Feed an event as if the given signal occurred (C<loop> must be the default
3142loop!). 3367loop!).
3143 3368
3144=back 3369=back
3145 3370
3146 3371
3372=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
3373
3374This section explains some common idioms that are not immediately
3375obvious. Note that examples are sprinkled over the whole manual, and this
3376section only contains stuff that wouldn't fit anywhere else.
3377
3378=over 4
3379
3380=item Model/nested event loop invocations and exit conditions.
3381
3382Often (especially in GUI toolkits) there are places where you have
3383I<modal> interaction, which is most easily implemented by recursively
3384invoking C<ev_run>.
3385
3386This brings the problem of exiting - a callback might want to finish the
3387main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
3388a modal "Are you sure?" dialog is still waiting), or just the nested one
3389and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
3390other combination: In these cases, C<ev_break> will not work alone.
3391
3392The solution is to maintain "break this loop" variable for each C<ev_run>
3393invocation, and use a loop around C<ev_run> until the condition is
3394triggered, using C<EVRUN_ONCE>:
3395
3396 // main loop
3397 int exit_main_loop = 0;
3398
3399 while (!exit_main_loop)
3400 ev_run (EV_DEFAULT_ EVRUN_ONCE);
3401
3402 // in a model watcher
3403 int exit_nested_loop = 0;
3404
3405 while (!exit_nested_loop)
3406 ev_run (EV_A_ EVRUN_ONCE);
3407
3408To exit from any of these loops, just set the corresponding exit variable:
3409
3410 // exit modal loop
3411 exit_nested_loop = 1;
3412
3413 // exit main program, after modal loop is finished
3414 exit_main_loop = 1;
3415
3416 // exit both
3417 exit_main_loop = exit_nested_loop = 1;
3418
3419=back
3420
3421
3147=head1 LIBEVENT EMULATION 3422=head1 LIBEVENT EMULATION
3148 3423
3149Libev offers a compatibility emulation layer for libevent. It cannot 3424Libev offers a compatibility emulation layer for libevent. It cannot
3150emulate the internals of libevent, so here are some usage hints: 3425emulate the internals of libevent, so here are some usage hints:
3151 3426
3152=over 4 3427=over 4
3428
3429=item * Only the libevent-1.4.1-beta API is being emulated.
3430
3431This was the newest libevent version available when libev was implemented,
3432and is still mostly uncanged in 2010.
3153 3433
3154=item * Use it by including <event.h>, as usual. 3434=item * Use it by including <event.h>, as usual.
3155 3435
3156=item * The following members are fully supported: ev_base, ev_callback, 3436=item * The following members are fully supported: ev_base, ev_callback,
3157ev_arg, ev_fd, ev_res, ev_events. 3437ev_arg, ev_fd, ev_res, ev_events.
3163=item * Priorities are not currently supported. Initialising priorities 3443=item * Priorities are not currently supported. Initialising priorities
3164will fail and all watchers will have the same priority, even though there 3444will fail and all watchers will have the same priority, even though there
3165is an ev_pri field. 3445is an ev_pri field.
3166 3446
3167=item * In libevent, the last base created gets the signals, in libev, the 3447=item * In libevent, the last base created gets the signals, in libev, the
3168first base created (== the default loop) gets the signals. 3448base that registered the signal gets the signals.
3169 3449
3170=item * Other members are not supported. 3450=item * Other members are not supported.
3171 3451
3172=item * The libev emulation is I<not> ABI compatible to libevent, you need 3452=item * The libev emulation is I<not> ABI compatible to libevent, you need
3173to use the libev header file and library. 3453to use the libev header file and library.
3224 3504
3225=over 4 3505=over 4
3226 3506
3227=item ev::TYPE::TYPE () 3507=item ev::TYPE::TYPE ()
3228 3508
3229=item ev::TYPE::TYPE (struct ev_loop *) 3509=item ev::TYPE::TYPE (loop)
3230 3510
3231=item ev::TYPE::~TYPE 3511=item ev::TYPE::~TYPE
3232 3512
3233The constructor (optionally) takes an event loop to associate the watcher 3513The constructor (optionally) takes an event loop to associate the watcher
3234with. If it is omitted, it will use C<EV_DEFAULT>. 3514with. If it is omitted, it will use C<EV_DEFAULT>.
3267 myclass obj; 3547 myclass obj;
3268 ev::io iow; 3548 ev::io iow;
3269 iow.set <myclass, &myclass::io_cb> (&obj); 3549 iow.set <myclass, &myclass::io_cb> (&obj);
3270 3550
3271=item w->set (object *) 3551=item w->set (object *)
3272
3273This is an B<experimental> feature that might go away in a future version.
3274 3552
3275This is a variation of a method callback - leaving out the method to call 3553This is a variation of a method callback - leaving out the method to call
3276will default the method to C<operator ()>, which makes it possible to use 3554will default the method to C<operator ()>, which makes it possible to use
3277functor objects without having to manually specify the C<operator ()> all 3555functor objects without having to manually specify the C<operator ()> all
3278the time. Incidentally, you can then also leave out the template argument 3556the time. Incidentally, you can then also leave out the template argument
3311Example: Use a plain function as callback. 3589Example: Use a plain function as callback.
3312 3590
3313 static void io_cb (ev::io &w, int revents) { } 3591 static void io_cb (ev::io &w, int revents) { }
3314 iow.set <io_cb> (); 3592 iow.set <io_cb> ();
3315 3593
3316=item w->set (struct ev_loop *) 3594=item w->set (loop)
3317 3595
3318Associates a different C<struct ev_loop> with this watcher. You can only 3596Associates a different C<struct ev_loop> with this watcher. You can only
3319do this when the watcher is inactive (and not pending either). 3597do this when the watcher is inactive (and not pending either).
3320 3598
3321=item w->set ([arguments]) 3599=item w->set ([arguments])
3322 3600
3323Basically the same as C<ev_TYPE_set>, with the same arguments. Must be 3601Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3324called at least once. Unlike the C counterpart, an active watcher gets 3602method or a suitable start method must be called at least once. Unlike the
3325automatically stopped and restarted when reconfiguring it with this 3603C counterpart, an active watcher gets automatically stopped and restarted
3326method. 3604when reconfiguring it with this method.
3327 3605
3328=item w->start () 3606=item w->start ()
3329 3607
3330Starts the watcher. Note that there is no C<loop> argument, as the 3608Starts the watcher. Note that there is no C<loop> argument, as the
3331constructor already stores the event loop. 3609constructor already stores the event loop.
3332 3610
3611=item w->start ([arguments])
3612
3613Instead of calling C<set> and C<start> methods separately, it is often
3614convenient to wrap them in one call. Uses the same type of arguments as
3615the configure C<set> method of the watcher.
3616
3333=item w->stop () 3617=item w->stop ()
3334 3618
3335Stops the watcher if it is active. Again, no C<loop> argument. 3619Stops the watcher if it is active. Again, no C<loop> argument.
3336 3620
3337=item w->again () (C<ev::timer>, C<ev::periodic> only) 3621=item w->again () (C<ev::timer>, C<ev::periodic> only)
3349 3633
3350=back 3634=back
3351 3635
3352=back 3636=back
3353 3637
3354Example: Define a class with an IO and idle watcher, start one of them in 3638Example: Define a class with two I/O and idle watchers, start the I/O
3355the constructor. 3639watchers in the constructor.
3356 3640
3357 class myclass 3641 class myclass
3358 { 3642 {
3359 ev::io io ; void io_cb (ev::io &w, int revents); 3643 ev::io io ; void io_cb (ev::io &w, int revents);
3644 ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3360 ev::idle idle; void idle_cb (ev::idle &w, int revents); 3645 ev::idle idle; void idle_cb (ev::idle &w, int revents);
3361 3646
3362 myclass (int fd) 3647 myclass (int fd)
3363 { 3648 {
3364 io .set <myclass, &myclass::io_cb > (this); 3649 io .set <myclass, &myclass::io_cb > (this);
3650 io2 .set <myclass, &myclass::io2_cb > (this);
3365 idle.set <myclass, &myclass::idle_cb> (this); 3651 idle.set <myclass, &myclass::idle_cb> (this);
3366 3652
3367 io.start (fd, ev::READ); 3653 io.set (fd, ev::WRITE); // configure the watcher
3654 io.start (); // start it whenever convenient
3655
3656 io2.start (fd, ev::READ); // set + start in one call
3368 } 3657 }
3369 }; 3658 };
3370 3659
3371 3660
3372=head1 OTHER LANGUAGE BINDINGS 3661=head1 OTHER LANGUAGE BINDINGS
3420Erkki Seppala has written Ocaml bindings for libev, to be found at 3709Erkki Seppala has written Ocaml bindings for libev, to be found at
3421L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. 3710L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3422 3711
3423=item Lua 3712=item Lua
3424 3713
3425Brian Maher has written a partial interface to libev 3714Brian Maher has written a partial interface to libev for lua (at the
3426for lua (only C<ev_io> and C<ev_timer>), to be found at 3715time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3427L<http://github.com/brimworks/lua-ev>. 3716L<http://github.com/brimworks/lua-ev>.
3428 3717
3429=back 3718=back
3430 3719
3431 3720
3446loop argument"). The C<EV_A> form is used when this is the sole argument, 3735loop argument"). The C<EV_A> form is used when this is the sole argument,
3447C<EV_A_> is used when other arguments are following. Example: 3736C<EV_A_> is used when other arguments are following. Example:
3448 3737
3449 ev_unref (EV_A); 3738 ev_unref (EV_A);
3450 ev_timer_add (EV_A_ watcher); 3739 ev_timer_add (EV_A_ watcher);
3451 ev_loop (EV_A_ 0); 3740 ev_run (EV_A_ 0);
3452 3741
3453It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, 3742It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3454which is often provided by the following macro. 3743which is often provided by the following macro.
3455 3744
3456=item C<EV_P>, C<EV_P_> 3745=item C<EV_P>, C<EV_P_>
3496 } 3785 }
3497 3786
3498 ev_check check; 3787 ev_check check;
3499 ev_check_init (&check, check_cb); 3788 ev_check_init (&check, check_cb);
3500 ev_check_start (EV_DEFAULT_ &check); 3789 ev_check_start (EV_DEFAULT_ &check);
3501 ev_loop (EV_DEFAULT_ 0); 3790 ev_run (EV_DEFAULT_ 0);
3502 3791
3503=head1 EMBEDDING 3792=head1 EMBEDDING
3504 3793
3505Libev can (and often is) directly embedded into host 3794Libev can (and often is) directly embedded into host
3506applications. Examples of applications that embed it include the Deliantra 3795applications. Examples of applications that embed it include the Deliantra
3586 libev.m4 3875 libev.m4
3587 3876
3588=head2 PREPROCESSOR SYMBOLS/MACROS 3877=head2 PREPROCESSOR SYMBOLS/MACROS
3589 3878
3590Libev can be configured via a variety of preprocessor symbols you have to 3879Libev can be configured via a variety of preprocessor symbols you have to
3591define before including any of its files. The default in the absence of 3880define before including (or compiling) any of its files. The default in
3592autoconf is documented for every option. 3881the absence of autoconf is documented for every option.
3882
3883Symbols marked with "(h)" do not change the ABI, and can have different
3884values when compiling libev vs. including F<ev.h>, so it is permissible
3885to redefine them before including F<ev.h> without breaking compatibility
3886to a compiled library. All other symbols change the ABI, which means all
3887users of libev and the libev code itself must be compiled with compatible
3888settings.
3593 3889
3594=over 4 3890=over 4
3595 3891
3892=item EV_COMPAT3 (h)
3893
3894Backwards compatibility is a major concern for libev. This is why this
3895release of libev comes with wrappers for the functions and symbols that
3896have been renamed between libev version 3 and 4.
3897
3898You can disable these wrappers (to test compatibility with future
3899versions) by defining C<EV_COMPAT3> to C<0> when compiling your
3900sources. This has the additional advantage that you can drop the C<struct>
3901from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
3902typedef in that case.
3903
3904In some future version, the default for C<EV_COMPAT3> will become C<0>,
3905and in some even more future version the compatibility code will be
3906removed completely.
3907
3596=item EV_STANDALONE 3908=item EV_STANDALONE (h)
3597 3909
3598Must always be C<1> if you do not use autoconf configuration, which 3910Must always be C<1> if you do not use autoconf configuration, which
3599keeps libev from including F<config.h>, and it also defines dummy 3911keeps libev from including F<config.h>, and it also defines dummy
3600implementations for some libevent functions (such as logging, which is not 3912implementations for some libevent functions (such as logging, which is not
3601supported). It will also not define any of the structs usually found in 3913supported). It will also not define any of the structs usually found in
3751as well as for signal and thread safety in C<ev_async> watchers. 4063as well as for signal and thread safety in C<ev_async> watchers.
3752 4064
3753In the absence of this define, libev will use C<sig_atomic_t volatile> 4065In the absence of this define, libev will use C<sig_atomic_t volatile>
3754(from F<signal.h>), which is usually good enough on most platforms. 4066(from F<signal.h>), which is usually good enough on most platforms.
3755 4067
3756=item EV_H 4068=item EV_H (h)
3757 4069
3758The name of the F<ev.h> header file used to include it. The default if 4070The name of the F<ev.h> header file used to include it. The default if
3759undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be 4071undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3760used to virtually rename the F<ev.h> header file in case of conflicts. 4072used to virtually rename the F<ev.h> header file in case of conflicts.
3761 4073
3762=item EV_CONFIG_H 4074=item EV_CONFIG_H (h)
3763 4075
3764If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 4076If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3765F<ev.c>'s idea of where to find the F<config.h> file, similarly to 4077F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3766C<EV_H>, above. 4078C<EV_H>, above.
3767 4079
3768=item EV_EVENT_H 4080=item EV_EVENT_H (h)
3769 4081
3770Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 4082Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3771of how the F<event.h> header can be found, the default is C<"event.h">. 4083of how the F<event.h> header can be found, the default is C<"event.h">.
3772 4084
3773=item EV_PROTOTYPES 4085=item EV_PROTOTYPES (h)
3774 4086
3775If defined to be C<0>, then F<ev.h> will not define any function 4087If defined to be C<0>, then F<ev.h> will not define any function
3776prototypes, but still define all the structs and other symbols. This is 4088prototypes, but still define all the structs and other symbols. This is
3777occasionally useful if you want to provide your own wrapper functions 4089occasionally useful if you want to provide your own wrapper functions
3778around libev functions. 4090around libev functions.
3800fine. 4112fine.
3801 4113
3802If your embedding application does not need any priorities, defining these 4114If your embedding application does not need any priorities, defining these
3803both to C<0> will save some memory and CPU. 4115both to C<0> will save some memory and CPU.
3804 4116
3805=item EV_PERIODIC_ENABLE 4117=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
4118EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
4119EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3806 4120
3807If undefined or defined to be C<1>, then periodic timers are supported. If 4121If undefined or defined to be C<1> (and the platform supports it), then
3808defined to be C<0>, then they are not. Disabling them saves a few kB of 4122the respective watcher type is supported. If defined to be C<0>, then it
3809code. 4123is not. Disabling watcher types mainly saves code size.
3810 4124
3811=item EV_IDLE_ENABLE 4125=item EV_FEATURES
3812
3813If undefined or defined to be C<1>, then idle watchers are supported. If
3814defined to be C<0>, then they are not. Disabling them saves a few kB of
3815code.
3816
3817=item EV_EMBED_ENABLE
3818
3819If undefined or defined to be C<1>, then embed watchers are supported. If
3820defined to be C<0>, then they are not. Embed watchers rely on most other
3821watcher types, which therefore must not be disabled.
3822
3823=item EV_STAT_ENABLE
3824
3825If undefined or defined to be C<1>, then stat watchers are supported. If
3826defined to be C<0>, then they are not.
3827
3828=item EV_FORK_ENABLE
3829
3830If undefined or defined to be C<1>, then fork watchers are supported. If
3831defined to be C<0>, then they are not.
3832
3833=item EV_ASYNC_ENABLE
3834
3835If undefined or defined to be C<1>, then async watchers are supported. If
3836defined to be C<0>, then they are not.
3837
3838=item EV_MINIMAL
3839 4126
3840If you need to shave off some kilobytes of code at the expense of some 4127If you need to shave off some kilobytes of code at the expense of some
3841speed (but with the full API), define this symbol to C<1>. Currently this 4128speed (but with the full API), you can define this symbol to request
3842is used to override some inlining decisions, saves roughly 30% code size 4129certain subsets of functionality. The default is to enable all features
3843on amd64. It also selects a much smaller 2-heap for timer management over 4130that can be enabled on the platform.
3844the default 4-heap.
3845 4131
3846You can save even more by disabling watcher types you do not need 4132A typical way to use this symbol is to define it to C<0> (or to a bitset
3847and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> 4133with some broad features you want) and then selectively re-enable
3848(C<-DNDEBUG>) will usually reduce code size a lot. 4134additional parts you want, for example if you want everything minimal,
4135but multiple event loop support, async and child watchers and the poll
4136backend, use this:
3849 4137
3850Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to 4138 #define EV_FEATURES 0
3851provide a bare-bones event library. See C<ev.h> for details on what parts 4139 #define EV_MULTIPLICITY 1
3852of the API are still available, and do not complain if this subset changes 4140 #define EV_USE_POLL 1
3853over time. 4141 #define EV_CHILD_ENABLE 1
4142 #define EV_ASYNC_ENABLE 1
4143
4144The actual value is a bitset, it can be a combination of the following
4145values:
4146
4147=over 4
4148
4149=item C<1> - faster/larger code
4150
4151Use larger code to speed up some operations.
4152
4153Currently this is used to override some inlining decisions (enlarging the
4154code size by roughly 30% on amd64).
4155
4156When optimising for size, use of compiler flags such as C<-Os> with
4157gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4158assertions.
4159
4160=item C<2> - faster/larger data structures
4161
4162Replaces the small 2-heap for timer management by a faster 4-heap, larger
4163hash table sizes and so on. This will usually further increase code size
4164and can additionally have an effect on the size of data structures at
4165runtime.
4166
4167=item C<4> - full API configuration
4168
4169This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4170enables multiplicity (C<EV_MULTIPLICITY>=1).
4171
4172=item C<8> - full API
4173
4174This enables a lot of the "lesser used" API functions. See C<ev.h> for
4175details on which parts of the API are still available without this
4176feature, and do not complain if this subset changes over time.
4177
4178=item C<16> - enable all optional watcher types
4179
4180Enables all optional watcher types. If you want to selectively enable
4181only some watcher types other than I/O and timers (e.g. prepare,
4182embed, async, child...) you can enable them manually by defining
4183C<EV_watchertype_ENABLE> to C<1> instead.
4184
4185=item C<32> - enable all backends
4186
4187This enables all backends - without this feature, you need to enable at
4188least one backend manually (C<EV_USE_SELECT> is a good choice).
4189
4190=item C<64> - enable OS-specific "helper" APIs
4191
4192Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
4193default.
4194
4195=back
4196
4197Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
4198reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
4199code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
4200watchers, timers and monotonic clock support.
4201
4202With an intelligent-enough linker (gcc+binutils are intelligent enough
4203when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4204your program might be left out as well - a binary starting a timer and an
4205I/O watcher then might come out at only 5Kb.
4206
4207=item EV_AVOID_STDIO
4208
4209If this is set to C<1> at compiletime, then libev will avoid using stdio
4210functions (printf, scanf, perror etc.). This will increase the code size
4211somewhat, but if your program doesn't otherwise depend on stdio and your
4212libc allows it, this avoids linking in the stdio library which is quite
4213big.
4214
4215Note that error messages might become less precise when this option is
4216enabled.
3854 4217
3855=item EV_NSIG 4218=item EV_NSIG
3856 4219
3857The highest supported signal number, +1 (or, the number of 4220The highest supported signal number, +1 (or, the number of
3858signals): Normally, libev tries to deduce the maximum number of signals 4221signals): Normally, libev tries to deduce the maximum number of signals
3859automatically, but sometimes this fails, in which case it can be 4222automatically, but sometimes this fails, in which case it can be
3860specified. Also, using a lower number than detected (C<32> should be 4223specified. Also, using a lower number than detected (C<32> should be
3861good for about any system in existance) can save some memory, as libev 4224good for about any system in existence) can save some memory, as libev
3862statically allocates some 12-24 bytes per signal number. 4225statically allocates some 12-24 bytes per signal number.
3863 4226
3864=item EV_PID_HASHSIZE 4227=item EV_PID_HASHSIZE
3865 4228
3866C<ev_child> watchers use a small hash table to distribute workload by 4229C<ev_child> watchers use a small hash table to distribute workload by
3867pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more 4230pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3868than enough. If you need to manage thousands of children you might want to 4231usually more than enough. If you need to manage thousands of children you
3869increase this value (I<must> be a power of two). 4232might want to increase this value (I<must> be a power of two).
3870 4233
3871=item EV_INOTIFY_HASHSIZE 4234=item EV_INOTIFY_HASHSIZE
3872 4235
3873C<ev_stat> watchers use a small hash table to distribute workload by 4236C<ev_stat> watchers use a small hash table to distribute workload by
3874inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 4237inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3875usually more than enough. If you need to manage thousands of C<ev_stat> 4238disabled), usually more than enough. If you need to manage thousands of
3876watchers you might want to increase this value (I<must> be a power of 4239C<ev_stat> watchers you might want to increase this value (I<must> be a
3877two). 4240power of two).
3878 4241
3879=item EV_USE_4HEAP 4242=item EV_USE_4HEAP
3880 4243
3881Heaps are not very cache-efficient. To improve the cache-efficiency of the 4244Heaps are not very cache-efficient. To improve the cache-efficiency of the
3882timer and periodics heaps, libev uses a 4-heap when this symbol is defined 4245timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3883to C<1>. The 4-heap uses more complicated (longer) code but has noticeably 4246to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3884faster performance with many (thousands) of watchers. 4247faster performance with many (thousands) of watchers.
3885 4248
3886The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4249The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3887(disabled). 4250will be C<0>.
3888 4251
3889=item EV_HEAP_CACHE_AT 4252=item EV_HEAP_CACHE_AT
3890 4253
3891Heaps are not very cache-efficient. To improve the cache-efficiency of the 4254Heaps are not very cache-efficient. To improve the cache-efficiency of the
3892timer and periodics heaps, libev can cache the timestamp (I<at>) within 4255timer and periodics heaps, libev can cache the timestamp (I<at>) within
3893the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), 4256the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3894which uses 8-12 bytes more per watcher and a few hundred bytes more code, 4257which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3895but avoids random read accesses on heap changes. This improves performance 4258but avoids random read accesses on heap changes. This improves performance
3896noticeably with many (hundreds) of watchers. 4259noticeably with many (hundreds) of watchers.
3897 4260
3898The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4261The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3899(disabled). 4262will be C<0>.
3900 4263
3901=item EV_VERIFY 4264=item EV_VERIFY
3902 4265
3903Controls how much internal verification (see C<ev_loop_verify ()>) will 4266Controls how much internal verification (see C<ev_verify ()>) will
3904be done: If set to C<0>, no internal verification code will be compiled 4267be done: If set to C<0>, no internal verification code will be compiled
3905in. If set to C<1>, then verification code will be compiled in, but not 4268in. If set to C<1>, then verification code will be compiled in, but not
3906called. If set to C<2>, then the internal verification code will be 4269called. If set to C<2>, then the internal verification code will be
3907called once per loop, which can slow down libev. If set to C<3>, then the 4270called once per loop, which can slow down libev. If set to C<3>, then the
3908verification code will be called very frequently, which will slow down 4271verification code will be called very frequently, which will slow down
3909libev considerably. 4272libev considerably.
3910 4273
3911The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be 4274The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3912C<0>. 4275will be C<0>.
3913 4276
3914=item EV_COMMON 4277=item EV_COMMON
3915 4278
3916By default, all watchers have a C<void *data> member. By redefining 4279By default, all watchers have a C<void *data> member. By redefining
3917this macro to a something else you can include more and other types of 4280this macro to something else you can include more and other types of
3918members. You have to define it each time you include one of the files, 4281members. You have to define it each time you include one of the files,
3919though, and it must be identical each time. 4282though, and it must be identical each time.
3920 4283
3921For example, the perl EV module uses something like this: 4284For example, the perl EV module uses something like this:
3922 4285
3975file. 4338file.
3976 4339
3977The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 4340The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3978that everybody includes and which overrides some configure choices: 4341that everybody includes and which overrides some configure choices:
3979 4342
3980 #define EV_MINIMAL 1 4343 #define EV_FEATURES 8
3981 #define EV_USE_POLL 0 4344 #define EV_USE_SELECT 1
3982 #define EV_MULTIPLICITY 0
3983 #define EV_PERIODIC_ENABLE 0 4345 #define EV_PREPARE_ENABLE 1
4346 #define EV_IDLE_ENABLE 1
3984 #define EV_STAT_ENABLE 0 4347 #define EV_SIGNAL_ENABLE 1
3985 #define EV_FORK_ENABLE 0 4348 #define EV_CHILD_ENABLE 1
4349 #define EV_USE_STDEXCEPT 0
3986 #define EV_CONFIG_H <config.h> 4350 #define EV_CONFIG_H <config.h>
3987 #define EV_MINPRI 0
3988 #define EV_MAXPRI 0
3989 4351
3990 #include "ev++.h" 4352 #include "ev++.h"
3991 4353
3992And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 4354And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3993 4355
4124 userdata *u = ev_userdata (EV_A); 4486 userdata *u = ev_userdata (EV_A);
4125 pthread_mutex_lock (&u->lock); 4487 pthread_mutex_lock (&u->lock);
4126 } 4488 }
4127 4489
4128The event loop thread first acquires the mutex, and then jumps straight 4490The event loop thread first acquires the mutex, and then jumps straight
4129into C<ev_loop>: 4491into C<ev_run>:
4130 4492
4131 void * 4493 void *
4132 l_run (void *thr_arg) 4494 l_run (void *thr_arg)
4133 { 4495 {
4134 struct ev_loop *loop = (struct ev_loop *)thr_arg; 4496 struct ev_loop *loop = (struct ev_loop *)thr_arg;
4135 4497
4136 l_acquire (EV_A); 4498 l_acquire (EV_A);
4137 pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); 4499 pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4138 ev_loop (EV_A_ 0); 4500 ev_run (EV_A_ 0);
4139 l_release (EV_A); 4501 l_release (EV_A);
4140 4502
4141 return 0; 4503 return 0;
4142 } 4504 }
4143 4505
4195 4557
4196=head3 COROUTINES 4558=head3 COROUTINES
4197 4559
4198Libev is very accommodating to coroutines ("cooperative threads"): 4560Libev is very accommodating to coroutines ("cooperative threads"):
4199libev fully supports nesting calls to its functions from different 4561libev fully supports nesting calls to its functions from different
4200coroutines (e.g. you can call C<ev_loop> on the same loop from two 4562coroutines (e.g. you can call C<ev_run> on the same loop from two
4201different coroutines, and switch freely between both coroutines running 4563different coroutines, and switch freely between both coroutines running
4202the loop, as long as you don't confuse yourself). The only exception is 4564the loop, as long as you don't confuse yourself). The only exception is
4203that you must not do this from C<ev_periodic> reschedule callbacks. 4565that you must not do this from C<ev_periodic> reschedule callbacks.
4204 4566
4205Care has been taken to ensure that libev does not keep local state inside 4567Care has been taken to ensure that libev does not keep local state inside
4206C<ev_loop>, and other calls do not usually allow for coroutine switches as 4568C<ev_run>, and other calls do not usually allow for coroutine switches as
4207they do not call any callbacks. 4569they do not call any callbacks.
4208 4570
4209=head2 COMPILER WARNINGS 4571=head2 COMPILER WARNINGS
4210 4572
4211Depending on your compiler and compiler settings, you might get no or a 4573Depending on your compiler and compiler settings, you might get no or a
4222maintainable. 4584maintainable.
4223 4585
4224And of course, some compiler warnings are just plain stupid, or simply 4586And of course, some compiler warnings are just plain stupid, or simply
4225wrong (because they don't actually warn about the condition their message 4587wrong (because they don't actually warn about the condition their message
4226seems to warn about). For example, certain older gcc versions had some 4588seems to warn about). For example, certain older gcc versions had some
4227warnings that resulted an extreme number of false positives. These have 4589warnings that resulted in an extreme number of false positives. These have
4228been fixed, but some people still insist on making code warn-free with 4590been fixed, but some people still insist on making code warn-free with
4229such buggy versions. 4591such buggy versions.
4230 4592
4231While libev is written to generate as few warnings as possible, 4593While libev is written to generate as few warnings as possible,
4232"warn-free" code is not a goal, and it is recommended not to build libev 4594"warn-free" code is not a goal, and it is recommended not to build libev
4268I suggest using suppression lists. 4630I suggest using suppression lists.
4269 4631
4270 4632
4271=head1 PORTABILITY NOTES 4633=head1 PORTABILITY NOTES
4272 4634
4635=head2 GNU/LINUX 32 BIT LIMITATIONS
4636
4637GNU/Linux is the only common platform that supports 64 bit file/large file
4638interfaces but I<disables> them by default.
4639
4640That means that libev compiled in the default environment doesn't support
4641files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
4642
4643Unfortunately, many programs try to work around this GNU/Linux issue
4644by enabling the large file API, which makes them incompatible with the
4645standard libev compiled for their system.
4646
4647Likewise, libev cannot enable the large file API itself as this would
4648suddenly make it incompatible to the default compile time environment,
4649i.e. all programs not using special compile switches.
4650
4651=head2 OS/X AND DARWIN BUGS
4652
4653The whole thing is a bug if you ask me - basically any system interface
4654you touch is broken, whether it is locales, poll, kqueue or even the
4655OpenGL drivers.
4656
4657=head3 C<kqueue> is buggy
4658
4659The kqueue syscall is broken in all known versions - most versions support
4660only sockets, many support pipes.
4661
4662Libev tries to work around this by not using C<kqueue> by default on this
4663rotten platform, but of course you can still ask for it when creating a
4664loop - embedding a socket-only kqueue loop into a select-based one is
4665probably going to work well.
4666
4667=head3 C<poll> is buggy
4668
4669Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4670implementation by something calling C<kqueue> internally around the 10.5.6
4671release, so now C<kqueue> I<and> C<poll> are broken.
4672
4673Libev tries to work around this by not using C<poll> by default on
4674this rotten platform, but of course you can still ask for it when creating
4675a loop.
4676
4677=head3 C<select> is buggy
4678
4679All that's left is C<select>, and of course Apple found a way to fuck this
4680one up as well: On OS/X, C<select> actively limits the number of file
4681descriptors you can pass in to 1024 - your program suddenly crashes when
4682you use more.
4683
4684There is an undocumented "workaround" for this - defining
4685C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
4686work on OS/X.
4687
4688=head2 SOLARIS PROBLEMS AND WORKAROUNDS
4689
4690=head3 C<errno> reentrancy
4691
4692The default compile environment on Solaris is unfortunately so
4693thread-unsafe that you can't even use components/libraries compiled
4694without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4695defined by default. A valid, if stupid, implementation choice.
4696
4697If you want to use libev in threaded environments you have to make sure
4698it's compiled with C<_REENTRANT> defined.
4699
4700=head3 Event port backend
4701
4702The scalable event interface for Solaris is called "event
4703ports". Unfortunately, this mechanism is very buggy in all major
4704releases. If you run into high CPU usage, your program freezes or you get
4705a large number of spurious wakeups, make sure you have all the relevant
4706and latest kernel patches applied. No, I don't know which ones, but there
4707are multiple ones to apply, and afterwards, event ports actually work
4708great.
4709
4710If you can't get it to work, you can try running the program by setting
4711the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4712C<select> backends.
4713
4714=head2 AIX POLL BUG
4715
4716AIX unfortunately has a broken C<poll.h> header. Libev works around
4717this by trying to avoid the poll backend altogether (i.e. it's not even
4718compiled in), which normally isn't a big problem as C<select> works fine
4719with large bitsets on AIX, and AIX is dead anyway.
4720
4273=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS 4721=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4722
4723=head3 General issues
4274 4724
4275Win32 doesn't support any of the standards (e.g. POSIX) that libev 4725Win32 doesn't support any of the standards (e.g. POSIX) that libev
4276requires, and its I/O model is fundamentally incompatible with the POSIX 4726requires, and its I/O model is fundamentally incompatible with the POSIX
4277model. Libev still offers limited functionality on this platform in 4727model. Libev still offers limited functionality on this platform in
4278the form of the C<EVBACKEND_SELECT> backend, and only supports socket 4728the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4279descriptors. This only applies when using Win32 natively, not when using 4729descriptors. This only applies when using Win32 natively, not when using
4280e.g. cygwin. 4730e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4731as every compielr comes with a slightly differently broken/incompatible
4732environment.
4281 4733
4282Lifting these limitations would basically require the full 4734Lifting these limitations would basically require the full
4283re-implementation of the I/O system. If you are into these kinds of 4735re-implementation of the I/O system. If you are into this kind of thing,
4284things, then note that glib does exactly that for you in a very portable 4736then note that glib does exactly that for you in a very portable way (note
4285way (note also that glib is the slowest event library known to man). 4737also that glib is the slowest event library known to man).
4286 4738
4287There is no supported compilation method available on windows except 4739There is no supported compilation method available on windows except
4288embedding it into other applications. 4740embedding it into other applications.
4289 4741
4290Sensible signal handling is officially unsupported by Microsoft - libev 4742Sensible signal handling is officially unsupported by Microsoft - libev
4318you do I<not> compile the F<ev.c> or any other embedded source files!): 4770you do I<not> compile the F<ev.c> or any other embedded source files!):
4319 4771
4320 #include "evwrap.h" 4772 #include "evwrap.h"
4321 #include "ev.c" 4773 #include "ev.c"
4322 4774
4323=over 4
4324
4325=item The winsocket select function 4775=head3 The winsocket C<select> function
4326 4776
4327The winsocket C<select> function doesn't follow POSIX in that it 4777The winsocket C<select> function doesn't follow POSIX in that it
4328requires socket I<handles> and not socket I<file descriptors> (it is 4778requires socket I<handles> and not socket I<file descriptors> (it is
4329also extremely buggy). This makes select very inefficient, and also 4779also extremely buggy). This makes select very inefficient, and also
4330requires a mapping from file descriptors to socket handles (the Microsoft 4780requires a mapping from file descriptors to socket handles (the Microsoft
4339 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ 4789 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4340 4790
4341Note that winsockets handling of fd sets is O(n), so you can easily get a 4791Note that winsockets handling of fd sets is O(n), so you can easily get a
4342complexity in the O(n²) range when using win32. 4792complexity in the O(n²) range when using win32.
4343 4793
4344=item Limited number of file descriptors 4794=head3 Limited number of file descriptors
4345 4795
4346Windows has numerous arbitrary (and low) limits on things. 4796Windows has numerous arbitrary (and low) limits on things.
4347 4797
4348Early versions of winsocket's select only supported waiting for a maximum 4798Early versions of winsocket's select only supported waiting for a maximum
4349of C<64> handles (probably owning to the fact that all windows kernels 4799of C<64> handles (probably owning to the fact that all windows kernels
4364runtime libraries. This might get you to about C<512> or C<2048> sockets 4814runtime libraries. This might get you to about C<512> or C<2048> sockets
4365(depending on windows version and/or the phase of the moon). To get more, 4815(depending on windows version and/or the phase of the moon). To get more,
4366you need to wrap all I/O functions and provide your own fd management, but 4816you need to wrap all I/O functions and provide your own fd management, but
4367the cost of calling select (O(n²)) will likely make this unworkable. 4817the cost of calling select (O(n²)) will likely make this unworkable.
4368 4818
4369=back
4370
4371=head2 PORTABILITY REQUIREMENTS 4819=head2 PORTABILITY REQUIREMENTS
4372 4820
4373In addition to a working ISO-C implementation and of course the 4821In addition to a working ISO-C implementation and of course the
4374backend-specific APIs, libev relies on a few additional extensions: 4822backend-specific APIs, libev relies on a few additional extensions:
4375 4823
4381Libev assumes not only that all watcher pointers have the same internal 4829Libev assumes not only that all watcher pointers have the same internal
4382structure (guaranteed by POSIX but not by ISO C for example), but it also 4830structure (guaranteed by POSIX but not by ISO C for example), but it also
4383assumes that the same (machine) code can be used to call any watcher 4831assumes that the same (machine) code can be used to call any watcher
4384callback: The watcher callbacks have different type signatures, but libev 4832callback: The watcher callbacks have different type signatures, but libev
4385calls them using an C<ev_watcher *> internally. 4833calls them using an C<ev_watcher *> internally.
4834
4835=item pointer accesses must be thread-atomic
4836
4837Accessing a pointer value must be atomic, it must both be readable and
4838writable in one piece - this is the case on all current architectures.
4386 4839
4387=item C<sig_atomic_t volatile> must be thread-atomic as well 4840=item C<sig_atomic_t volatile> must be thread-atomic as well
4388 4841
4389The type C<sig_atomic_t volatile> (or whatever is defined as 4842The type C<sig_atomic_t volatile> (or whatever is defined as
4390C<EV_ATOMIC_T>) must be atomic with respect to accesses from different 4843C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4413watchers. 4866watchers.
4414 4867
4415=item C<double> must hold a time value in seconds with enough accuracy 4868=item C<double> must hold a time value in seconds with enough accuracy
4416 4869
4417The type C<double> is used to represent timestamps. It is required to 4870The type C<double> is used to represent timestamps. It is required to
4418have at least 51 bits of mantissa (and 9 bits of exponent), which is good 4871have at least 51 bits of mantissa (and 9 bits of exponent), which is
4419enough for at least into the year 4000. This requirement is fulfilled by 4872good enough for at least into the year 4000 with millisecond accuracy
4873(the design goal for libev). This requirement is overfulfilled by
4420implementations implementing IEEE 754, which is basically all existing 4874implementations using IEEE 754, which is basically all existing ones. With
4421ones. With IEEE 754 doubles, you get microsecond accuracy until at least 4875IEEE 754 doubles, you get microsecond accuracy until at least 2200.
44222200.
4423 4876
4424=back 4877=back
4425 4878
4426If you know of other additional requirements drop me a note. 4879If you know of other additional requirements drop me a note.
4427 4880
4495involves iterating over all running async watchers or all signal numbers. 4948involves iterating over all running async watchers or all signal numbers.
4496 4949
4497=back 4950=back
4498 4951
4499 4952
4953=head1 PORTING FROM LIBEV 3.X TO 4.X
4954
4955The major version 4 introduced some incompatible changes to the API.
4956
4957At the moment, the C<ev.h> header file provides compatibility definitions
4958for all changes, so most programs should still compile. The compatibility
4959layer might be removed in later versions of libev, so better update to the
4960new API early than late.
4961
4962=over 4
4963
4964=item C<EV_COMPAT3> backwards compatibility mechanism
4965
4966The backward compatibility mechanism can be controlled by
4967C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4968section.
4969
4970=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4971
4972These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4973
4974 ev_loop_destroy (EV_DEFAULT_UC);
4975 ev_loop_fork (EV_DEFAULT);
4976
4977=item function/symbol renames
4978
4979A number of functions and symbols have been renamed:
4980
4981 ev_loop => ev_run
4982 EVLOOP_NONBLOCK => EVRUN_NOWAIT
4983 EVLOOP_ONESHOT => EVRUN_ONCE
4984
4985 ev_unloop => ev_break
4986 EVUNLOOP_CANCEL => EVBREAK_CANCEL
4987 EVUNLOOP_ONE => EVBREAK_ONE
4988 EVUNLOOP_ALL => EVBREAK_ALL
4989
4990 EV_TIMEOUT => EV_TIMER
4991
4992 ev_loop_count => ev_iteration
4993 ev_loop_depth => ev_depth
4994 ev_loop_verify => ev_verify
4995
4996Most functions working on C<struct ev_loop> objects don't have an
4997C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
4998associated constants have been renamed to not collide with the C<struct
4999ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
5000as all other watcher types. Note that C<ev_loop_fork> is still called
5001C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
5002typedef.
5003
5004=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
5005
5006The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
5007mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
5008and work, but the library code will of course be larger.
5009
5010=back
5011
5012
4500=head1 GLOSSARY 5013=head1 GLOSSARY
4501 5014
4502=over 4 5015=over 4
4503 5016
4504=item active 5017=item active
4505 5018
4506A watcher is active as long as it has been started (has been attached to 5019A watcher is active as long as it has been started and not yet stopped.
4507an event loop) but not yet stopped (disassociated from the event loop). 5020See L<WATCHER STATES> for details.
4508 5021
4509=item application 5022=item application
4510 5023
4511In this document, an application is whatever is using libev. 5024In this document, an application is whatever is using libev.
5025
5026=item backend
5027
5028The part of the code dealing with the operating system interfaces.
4512 5029
4513=item callback 5030=item callback
4514 5031
4515The address of a function that is called when some event has been 5032The address of a function that is called when some event has been
4516detected. Callbacks are being passed the event loop, the watcher that 5033detected. Callbacks are being passed the event loop, the watcher that
4517received the event, and the actual event bitset. 5034received the event, and the actual event bitset.
4518 5035
4519=item callback invocation 5036=item callback/watcher invocation
4520 5037
4521The act of calling the callback associated with a watcher. 5038The act of calling the callback associated with a watcher.
4522 5039
4523=item event 5040=item event
4524 5041
4525A change of state of some external event, such as data now being available 5042A change of state of some external event, such as data now being available
4526for reading on a file descriptor, time having passed or simply not having 5043for reading on a file descriptor, time having passed or simply not having
4527any other events happening anymore. 5044any other events happening anymore.
4528 5045
4529In libev, events are represented as single bits (such as C<EV_READ> or 5046In libev, events are represented as single bits (such as C<EV_READ> or
4530C<EV_TIMEOUT>). 5047C<EV_TIMER>).
4531 5048
4532=item event library 5049=item event library
4533 5050
4534A software package implementing an event model and loop. 5051A software package implementing an event model and loop.
4535 5052
4543The model used to describe how an event loop handles and processes 5060The model used to describe how an event loop handles and processes
4544watchers and events. 5061watchers and events.
4545 5062
4546=item pending 5063=item pending
4547 5064
4548A watcher is pending as soon as the corresponding event has been detected, 5065A watcher is pending as soon as the corresponding event has been
4549and stops being pending as soon as the watcher will be invoked or its 5066detected. See L<WATCHER STATES> for details.
4550pending status is explicitly cleared by the application.
4551
4552A watcher can be pending, but not active. Stopping a watcher also clears
4553its pending status.
4554 5067
4555=item real time 5068=item real time
4556 5069
4557The physical time that is observed. It is apparently strictly monotonic :) 5070The physical time that is observed. It is apparently strictly monotonic :)
4558 5071
4565=item watcher 5078=item watcher
4566 5079
4567A data structure that describes interest in certain events. Watchers need 5080A data structure that describes interest in certain events. Watchers need
4568to be started (attached to an event loop) before they can receive events. 5081to be started (attached to an event loop) before they can receive events.
4569 5082
4570=item watcher invocation
4571
4572The act of calling the callback associated with a watcher.
4573
4574=back 5083=back
4575 5084
4576=head1 AUTHOR 5085=head1 AUTHOR
4577 5086
4578Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. 5087Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5088Magnusson and Emanuele Giaquinta.
4579 5089

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