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…		…
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
210		234
211	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
232		256
233	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	263	(such as abort).
240		264
241	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
256		280
257	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
258	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
259	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
260		284
261	If you use threads, a common model is to run the default event loop
262	in your main thread (or in a separate thread) and for each thread you
263	create, you also create another event loop. Libev itself does no locking
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267
268	=over 4	285	=over 4
269		286
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		288
272	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		293
277	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
278	function.	295	function.
279		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
280	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	306	C<ev_default_init>.
286		307
287	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	318	thing, believe me).
298		319
299	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
300		321
301	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
306	around bugs.	327	around bugs.
…		…
313		334
314	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
320		341
321	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
323	flag.	344	flag.
324		345
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	347	environment variable.
327		348
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		350
330	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
335		356
336	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
342		363
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		365
345	And this is your standard poll(2) backend. It's more complicated	366	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	367	than select, but handles sparse fds better and has no artificial
…		…
354	For few fds, this backend is a bit little slower than poll and select,	375	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	376	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	377	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	379	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and rewiring a syscall per fd change, no fork support and bad	380	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	381	support for dup.
361		382
362	While stopping, setting and starting an I/O watcher in the same iteration	383	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	385	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	387	very well if you register events for both fds.
367		388
368	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
…		…
371		392
372	Best performance from this backend is achieved by not unregistering all	393	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	394	watchers for a file descriptor until it has been closed, if possible, i.e.
374	keep at least one watcher active per fd at all times.	395	keep at least one watcher active per fd at all times.
375		396
376	While nominally embeddeble in other event loops, this feature is broken in	397	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	398	all kernel versions tested so far.
378		399
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		401
381	Kqueue deserves special mention, as at the time of this writing, it	402	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	404	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
385	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	408	system like NetBSD.
388		409
389	You still can embed kqueue into a normal poll or select backend and use it	410	You still can embed kqueue into a normal poll or select backend and use it
…		…
391	the target platform). See C<ev_embed> watchers for more info.	412	the target platform). See C<ev_embed> watchers for more info.
392		413
393	It scales in the same way as the epoll backend, but the interface to the	414	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	415	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	416	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	418	two event changes per incident, support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	419	drops fds silently in similarly hard-to-detect cases.
399		420
400	This backend usually performs well under most conditions.	421	This backend usually performs well under most conditions.
401		422
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		438
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	440	it's really slow, but it still scales very well (O(active_fds)).
420		441
421	Please note that solaris event ports can deliver a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	443	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
424		445
425	While this backend scales well, it requires one system call per active	446	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	447	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	449	might perform better.
429		450
430	On the positive side, ignoring the spurious readyness notifications, this	451	On the positive side, ignoring the spurious readiness notifications, this
431	backend actually performed to specification in all tests and is fully	452	backend actually performed to specification in all tests and is fully
432	embeddable, which is a rare feat among the OS-specific backends.	453	embeddable, which is a rare feat among the OS-specific backends.
433		454
434	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
435		456
…		…
439		460
440	It is definitely not recommended to use this flag.	461	It is definitely not recommended to use this flag.
441		462
442	=back	463	=back
443		464
444	If one or more of these are ored into the flags value, then only these	465	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		468
448	The most typical usage is like this:	469	The most typical usage is like this:
449		470
…		…
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
470		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
471	Example: Try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
472		497
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	499	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
…		…
477	=item ev_default_destroy ()	502	=item ev_default_destroy ()
478		503
479	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
480	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
481	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
482	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
483	calling this function, or cope with the fact afterwards (which is usually	508	calling this function, or cope with the fact afterwards (which is usually
484	the easiest thing, you can just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	510	for example).
486		511
487	Note that certain global state, such as signal state, will not be freed by	512	Note that certain global state, such as signal state, will not be freed by
…		…
568	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
569	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
570	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
571		596
572	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
573	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
574	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
575	one iteration of the loop. This is useful if you are waiting for some	600	one iteration of the loop. This is useful if you are waiting for some
576	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
578	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
…		…
679	to spend more time collecting timeouts, at the expense of increased	704	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	705	latency (the watcher callback will be called later). C<ev_io> watchers
681	will not be affected. Setting this to a non-null value will not introduce	706	will not be affected. Setting this to a non-null value will not introduce
682	any overhead in libev.	707	any overhead in libev.
683		708
684	Many (busy) programs can usually benefit by setting the io collect	709	Many (busy) programs can usually benefit by setting the I/O collect
685	interval to a value near C<0.1> or so, which is often enough for	710	interval to a value near C<0.1> or so, which is often enough for
686	interactive servers (of course not for games), likewise for timeouts. It	711	interactive servers (of course not for games), likewise for timeouts. It
687	usually doesn't make much sense to set it to a lower value than C<0.01>,	712	usually doesn't make much sense to set it to a lower value than C<0.01>,
688	as this approsaches the timing granularity of most systems.	713	as this approaches the timing granularity of most systems.
		714
		715	=item ev_loop_verify (loop)
		716
		717	This function only does something when C<EV_VERIFY> support has been
		718	compiled in. It tries to go through all internal structures and checks
		719	them for validity. If anything is found to be inconsistent, it will print
		720	an error message to standard error and call C<abort ()>.
		721
		722	This can be used to catch bugs inside libev itself: under normal
		723	circumstances, this function will never abort as of course libev keeps its
		724	data structures consistent.
689		725
690	=back	726	=back
691		727
692		728
693	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
…		…
713	watcher structures (and it is usually a bad idea to do this on the stack,	749	watcher structures (and it is usually a bad idea to do this on the stack,
714	although this can sometimes be quite valid).	750	although this can sometimes be quite valid).
715		751
716	Each watcher structure must be initialised by a call to C<ev_init	752	Each watcher structure must be initialised by a call to C<ev_init
717	(watcher *, callback)>, which expects a callback to be provided. This	753	(watcher *, callback)>, which expects a callback to be provided. This
718	callback gets invoked each time the event occurs (or, in the case of io	754	callback gets invoked each time the event occurs (or, in the case of I/O
719	watchers, each time the event loop detects that the file descriptor given	755	watchers, each time the event loop detects that the file descriptor given
720	is readable and/or writable).	756	is readable and/or writable).
721		757
722	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
723	with arguments specific to this watcher type. There is also a macro	759	with arguments specific to this watcher type. There is also a macro
…		…
799		835
800	The given async watcher has been asynchronously notified (see C<ev_async>).	836	The given async watcher has been asynchronously notified (see C<ev_async>).
801		837
802	=item C<EV_ERROR>	838	=item C<EV_ERROR>
803		839
804	An unspecified error has occured, the watcher has been stopped. This might	840	An unspecified error has occurred, the watcher has been stopped. This might
805	happen because the watcher could not be properly started because libev	841	happen because the watcher could not be properly started because libev
806	ran out of memory, a file descriptor was found to be closed or any other	842	ran out of memory, a file descriptor was found to be closed or any other
807	problem. You best act on it by reporting the problem and somehow coping	843	problem. You best act on it by reporting the problem and somehow coping
808	with the watcher being stopped.	844	with the watcher being stopped.
809		845
810	Libev will usually signal a few "dummy" events together with an error,	846	Libev will usually signal a few "dummy" events together with an error,
811	for example it might indicate that a fd is readable or writable, and if	847	for example it might indicate that a fd is readable or writable, and if
812	your callbacks is well-written it can just attempt the operation and cope	848	your callbacks is well-written it can just attempt the operation and cope
813	with the error from read() or write(). This will not work in multithreaded	849	with the error from read() or write(). This will not work in multi-threaded
814	programs, though, so beware.	850	programs, though, so beware.
815		851
816	=back	852	=back
817		853
818	=head2 GENERIC WATCHER FUNCTIONS	854	=head2 GENERIC WATCHER FUNCTIONS
…		…
848	Although some watcher types do not have type-specific arguments	884	Although some watcher types do not have type-specific arguments
849	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
850		886
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		888
853	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
854	calls into a single call. This is the most convinient method to initialise	890	calls into a single call. This is the most convenient method to initialise
855	a watcher. The same limitations apply, of course.	891	a watcher. The same limitations apply, of course.
856		892
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
858		894
859	Starts (activates) the given watcher. Only active watchers will receive	895	Starts (activates) the given watcher. Only active watchers will receive
…		…
1028	If you must do this, then force the use of a known-to-be-good backend	1064	If you must do this, then force the use of a known-to-be-good backend
1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
1030	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
1031		1067
1032	Another thing you have to watch out for is that it is quite easy to	1068	Another thing you have to watch out for is that it is quite easy to
1033	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
1034	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1035	because there is no data. Not only are some backends known to create a	1071	because there is no data. Not only are some backends known to create a
1036	lot of those (for example solaris ports), it is very easy to get into	1072	lot of those (for example Solaris ports), it is very easy to get into
1037	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
1038	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1039	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1040		1076
1041	If you cannot run the fd in non-blocking mode (for example you should not	1077	If you cannot run the fd in non-blocking mode (for example you should not
1042	play around with an Xlib connection), then you have to seperately re-test	1078	play around with an Xlib connection), then you have to separately re-test
1043	whether a file descriptor is really ready with a known-to-be good interface	1079	whether a file descriptor is really ready with a known-to-be good interface
1044	such as poll (fortunately in our Xlib example, Xlib already does this on	1080	such as poll (fortunately in our Xlib example, Xlib already does this on
1045	its own, so its quite safe to use).	1081	its own, so its quite safe to use).
1046		1082
1047	=head3 The special problem of disappearing file descriptors	1083	=head3 The special problem of disappearing file descriptors
…		…
1085	To support fork in your programs, you either have to call	1121	To support fork in your programs, you either have to call
1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1124	C<EVBACKEND_POLL>.
1089		1125
		1126	=head3 The special problem of SIGPIPE
		1127
		1128	While not really specific to libev, it is easy to forget about SIGPIPE:
		1129	when reading from a pipe whose other end has been closed, your program
		1130	gets send a SIGPIPE, which, by default, aborts your program. For most
		1131	programs this is sensible behaviour, for daemons, this is usually
		1132	undesirable.
		1133
		1134	So when you encounter spurious, unexplained daemon exits, make sure you
		1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1136	somewhere, as that would have given you a big clue).
		1137
1090		1138
1091	=head3 Watcher-Specific Functions	1139	=head3 Watcher-Specific Functions
1092		1140
1093	=over 4	1141	=over 4
1094		1142
1095	=item ev_io_init (ev_io *, callback, int fd, int events)	1143	=item ev_io_init (ev_io *, callback, int fd, int events)
1096		1144
1097	=item ev_io_set (ev_io *, int fd, int events)	1145	=item ev_io_set (ev_io *, int fd, int events)
1098		1146
1099	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1100	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1101	C<EV_READ | EV_WRITE> to receive the given events.	1149	C<EV_READ | EV_WRITE> to receive the given events.
1102		1150
1103	=item int fd [read-only]	1151	=item int fd [read-only]
1104		1152
1105	The file descriptor being watched.	1153	The file descriptor being watched.
…		…
1135		1183
1136	Timer watchers are simple relative timers that generate an event after a	1184	Timer watchers are simple relative timers that generate an event after a
1137	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
1138		1186
1139	The timers are based on real time, that is, if you register an event that	1187	The timers are based on real time, that is, if you register an event that
1140	times out after an hour and you reset your system clock to last years	1188	times out after an hour and you reset your system clock to January last
1141	time, it will still time out after (roughly) and hour. "Roughly" because	1189	year, it will still time out after (roughly) and hour. "Roughly" because
1142	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1143	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
1144		1192
1145	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
1146	time. This is usually the right thing as this timestamp refers to the time	1194	time. This is usually the right thing as this timestamp refers to the time
…		…
1148	you suspect event processing to be delayed and you I<need> to base the timeout	1196	you suspect event processing to be delayed and you I<need> to base the timeout
1149	on the current time, use something like this to adjust for this:	1197	on the current time, use something like this to adjust for this:
1150		1198
1151	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1152		1200
1153	The callback is guarenteed to be invoked only when its timeout has passed,	1201	The callback is guaranteed to be invoked only after its timeout has passed,
1154	but if multiple timers become ready during the same loop iteration then	1202	but if multiple timers become ready during the same loop iteration then
1155	order of execution is undefined.	1203	order of execution is undefined.
1156		1204
1157	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1158		1206
…		…
1160		1208
1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1209	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1162		1210
1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1211	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1164		1212
1165	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1213	Configure the timer to trigger after C<after> seconds. If C<repeat>
1166	C<0.>, then it will automatically be stopped. If it is positive, then the	1214	is C<0.>, then it will automatically be stopped once the timeout is
1167	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1168	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1169		1218
1170	The timer itself will do a best-effort at avoiding drift, that is, if you	1219	The timer itself will do a best-effort at avoiding drift, that is, if
1171	configure a timer to trigger every 10 seconds, then it will trigger at	1220	you configure a timer to trigger every 10 seconds, then it will normally
1172	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1173	the timer (because it takes longer than those 10 seconds to do stuff) the	1222	keep up with the timer (because it takes longer than those 10 seconds to
1174	timer will not fire more than once per event loop iteration.	1223	do stuff) the timer will not fire more than once per event loop iteration.
1175		1224
1176	=item ev_timer_again (loop, ev_timer *)	1225	=item ev_timer_again (loop, ev_timer *)
1177		1226
1178	This will act as if the timer timed out and restart it again if it is	1227	This will act as if the timer timed out and restart it again if it is
1179	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
1180		1229
1181	If the timer is pending, its pending status is cleared.	1230	If the timer is pending, its pending status is cleared.
1182		1231
1183	If the timer is started but nonrepeating, stop it (as if it timed out).	1232	If the timer is started but non-repeating, stop it (as if it timed out).
1184		1233
1185	If the timer is repeating, either start it if necessary (with the	1234	If the timer is repeating, either start it if necessary (with the
1186	C<repeat> value), or reset the running timer to the C<repeat> value.	1235	C<repeat> value), or reset the running timer to the C<repeat> value.
1187		1236
1188	This sounds a bit complicated, but here is a useful and typical	1237	This sounds a bit complicated, but here is a useful and typical
1189	example: Imagine you have a tcp connection and you want a so-called idle	1238	example: Imagine you have a TCP connection and you want a so-called idle
1190	timeout, that is, you want to be called when there have been, say, 60	1239	timeout, that is, you want to be called when there have been, say, 60
1191	seconds of inactivity on the socket. The easiest way to do this is to	1240	seconds of inactivity on the socket. The easiest way to do this is to
1192	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1193	C<ev_timer_again> each time you successfully read or write some data. If	1242	C<ev_timer_again> each time you successfully read or write some data. If
1194	you go into an idle state where you do not expect data to travel on the	1243	you go into an idle state where you do not expect data to travel on the
…		…
1255		1304
1256	Periodic watchers are also timers of a kind, but they are very versatile	1305	Periodic watchers are also timers of a kind, but they are very versatile
1257	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1258		1307
1259	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1260	but on wallclock time (absolute time). You can tell a periodic watcher	1309	but on wall clock time (absolute time). You can tell a periodic watcher
1261	to trigger "at" some specific point in time. For example, if you tell a	1310	to trigger after some specific point in time. For example, if you tell a
1262	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1263	+ 10.>) and then reset your system clock to the last year, then it will	1312	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1313	clock to January of the previous year, then it will take more than year
1264	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1265	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1266		1316
1267	They can also be used to implement vastly more complex timers, such as	1317	C<ev_periodic>s can also be used to implement vastly more complex timers,
1268	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1269	rules.	1319	complicated, rules.
1270		1320
1271	As with timers, the callback is guarenteed to be invoked only when the	1321	As with timers, the callback is guaranteed to be invoked only when the
1272	time (C<at>) has been passed, but if multiple periodic timers become ready	1322	time (C<at>) has passed, but if multiple periodic timers become ready
1273	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1274		1324
1275	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1276		1326
1277	=over 4	1327	=over 4
…		…
1285		1335
1286	=over 4	1336	=over 4
1287		1337
1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1289		1339
1290	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wall clock
1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1341	time C<at> has passed and doesn't repeat. It will not adjust when a time
1292	that is, if it is to be run at January 1st 2011 then it will run when the	1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1293	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1294		1344
1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1296		1346
1297	In this mode the watcher will always be scheduled to time out at the next	1347	In this mode the watcher will always be scheduled to time out at the next
1298	C<at + N * interval> time (for some integer N, which can also be negative)	1348	C<at + N * interval> time (for some integer N, which can also be negative)
1299	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1300		1350
1301	This can be used to create timers that do not drift with respect to system	1351	This can be used to create timers that do not drift with respect to system
1302	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1303		1354
1304	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1305		1356
1306	This doesn't mean there will always be 3600 seconds in between triggers,	1357	This doesn't mean there will always be 3600 seconds in between triggers,
1307	but only that the the callback will be called when the system time shows a	1358	but only that the callback will be called when the system time shows a
1308	full hour (UTC), or more correctly, when the system time is evenly divisible	1359	full hour (UTC), or more correctly, when the system time is evenly divisible
1309	by 3600.	1360	by 3600.
1310		1361
1311	Another way to think about it (for the mathematically inclined) is that	1362	Another way to think about it (for the mathematically inclined) is that
1312	C<ev_periodic> will try to run the callback in this mode at the next possible	1363	C<ev_periodic> will try to run the callback in this mode at the next possible
1313	time where C<time = at (mod interval)>, regardless of any time jumps.	1364	time where C<time = at (mod interval)>, regardless of any time jumps.
1314		1365
1315	For numerical stability it is preferable that the C<at> value is near	1366	For numerical stability it is preferable that the C<at> value is near
1316	C<ev_now ()> (the current time), but there is no range requirement for	1367	C<ev_now ()> (the current time), but there is no range requirement for
1317	this value.	1368	this value, and in fact is often specified as zero.
		1369
		1370	Note also that there is an upper limit to how often a timer can fire (CPU
		1371	speed for example), so if C<interval> is very small then timing stability
		1372	will of course deteriorate. Libev itself tries to be exact to be about one
		1373	millisecond (if the OS supports it and the machine is fast enough).
1318		1374
1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1320		1376
1321	In this mode the values for C<interval> and C<at> are both being	1377	In this mode the values for C<interval> and C<at> are both being
1322	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1323	reschedule callback will be called with the watcher as first, and the	1379	reschedule callback will be called with the watcher as first, and the
1324	current time as second argument.	1380	current time as second argument.
1325		1381
1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1327	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1328	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1329	starting an C<ev_prepare> watcher, which is legal).
1330		1384
		1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1387	only event loop modification you are allowed to do).
		1388
1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1332	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1333		1391
1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1335	{	1393	{
1336	return now + 60.;	1394	return now + 60.;
1337	}	1395	}
…		…
1339	It must return the next time to trigger, based on the passed time value	1397	It must return the next time to trigger, based on the passed time value
1340	(that is, the lowest time value larger than to the second argument). It	1398	(that is, the lowest time value larger than to the second argument). It
1341	will usually be called just before the callback will be triggered, but	1399	will usually be called just before the callback will be triggered, but
1342	might be called at other times, too.	1400	might be called at other times, too.
1343		1401
1344	NOTE: I<< This callback must always return a time that is later than the	1402	NOTE: I<< This callback must always return a time that is higher than or
1345	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1346		1404
1347	This can be used to create very complex timers, such as a timer that	1405	This can be used to create very complex timers, such as a timer that
1348	triggers on each midnight, local time. To do this, you would calculate the	1406	triggers on "next midnight, local time". To do this, you would calculate the
1349	next midnight after C<now> and return the timestamp value for this. How	1407	next midnight after C<now> and return the timestamp value for this. How
1350	you do this is, again, up to you (but it is not trivial, which is the main	1408	you do this is, again, up to you (but it is not trivial, which is the main
1351	reason I omitted it as an example).	1409	reason I omitted it as an example).
1352		1410
1353	=back	1411	=back
…		…
1357	Simply stops and restarts the periodic watcher again. This is only useful	1415	Simply stops and restarts the periodic watcher again. This is only useful
1358	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1359	a different time than the last time it was called (e.g. in a crond like	1417	a different time than the last time it was called (e.g. in a crond like
1360	program when the crontabs have changed).	1418	program when the crontabs have changed).
1361		1419
		1420	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1421
		1422	When active, returns the absolute time that the watcher is supposed to
		1423	trigger next.
		1424
1362	=item ev_tstamp offset [read-write]	1425	=item ev_tstamp offset [read-write]
1363		1426
1364	When repeating, this contains the offset value, otherwise this is the	1427	When repeating, this contains the offset value, otherwise this is the
1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1366		1429
…		…
1377		1440
1378	The current reschedule callback, or C<0>, if this functionality is	1441	The current reschedule callback, or C<0>, if this functionality is
1379	switched off. Can be changed any time, but changes only take effect when	1442	switched off. Can be changed any time, but changes only take effect when
1380	the periodic timer fires or C<ev_periodic_again> is being called.	1443	the periodic timer fires or C<ev_periodic_again> is being called.
1381		1444
1382	=item ev_tstamp at [read-only]
1383
1384	When active, contains the absolute time that the watcher is supposed to
1385	trigger next.
1386
1387	=back	1445	=back
1388		1446
1389	=head3 Examples	1447	=head3 Examples
1390		1448
1391	Example: Call a callback every hour, or, more precisely, whenever the	1449	Example: Call a callback every hour, or, more precisely, whenever the
1392	system clock is divisible by 3600. The callback invocation times have	1450	system clock is divisible by 3600. The callback invocation times have
1393	potentially a lot of jittering, but good long-term stability.	1451	potentially a lot of jitter, but good long-term stability.
1394		1452
1395	static void	1453	static void
1396	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1397	{	1455	{
1398	... its now a full hour (UTC, or TAI or whatever your clock follows)	1456	... its now a full hour (UTC, or TAI or whatever your clock follows)
…		…
1435	as you don't register any with libev). Similarly, when the last signal	1493	as you don't register any with libev). Similarly, when the last signal
1436	watcher for a signal is stopped libev will reset the signal handler to	1494	watcher for a signal is stopped libev will reset the signal handler to
1437	SIG_DFL (regardless of what it was set to before).	1495	SIG_DFL (regardless of what it was set to before).
1438		1496
1439	If possible and supported, libev will install its handlers with	1497	If possible and supported, libev will install its handlers with
1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1441	interrupted. If you have a problem with syscalls getting interrupted by	1499	interrupted. If you have a problem with system calls getting interrupted by
1442	signals you can block all signals in an C<ev_check> watcher and unblock	1500	signals you can block all signals in an C<ev_check> watcher and unblock
1443	them in an C<ev_prepare> watcher.	1501	them in an C<ev_prepare> watcher.
1444		1502
1445	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1446		1504
…		…
1481	is permissible to install a child watcher I<after> the child has been	1539	is permissible to install a child watcher I<after> the child has been
1482	forked (which implies it might have already exited), as long as the event	1540	forked (which implies it might have already exited), as long as the event
1483	loop isn't entered (or is continued from a watcher).	1541	loop isn't entered (or is continued from a watcher).
1484		1542
1485	Only the default event loop is capable of handling signals, and therefore	1543	Only the default event loop is capable of handling signals, and therefore
1486	you can only rgeister child watchers in the default event loop.	1544	you can only register child watchers in the default event loop.
1487		1545
1488	=head3 Process Interaction	1546	=head3 Process Interaction
1489		1547
1490	Libev grabs C<SIGCHLD> as soon as the default event loop is	1548	Libev grabs C<SIGCHLD> as soon as the default event loop is
1491	initialised. This is necessary to guarantee proper behaviour even if	1549	initialised. This is necessary to guarantee proper behaviour even if
1492	the first child watcher is started after the child exits. The occurance	1550	the first child watcher is started after the child exits. The occurrence
1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1494	synchronously as part of the event loop processing. Libev always reaps all	1552	synchronously as part of the event loop processing. Libev always reaps all
1495	children, even ones not watched.	1553	children, even ones not watched.
1496		1554
1497	=head3 Overriding the Built-In Processing	1555	=head3 Overriding the Built-In Processing
…		…
1566	}	1624	}
1567		1625
1568		1626
1569	=head2 C<ev_stat> - did the file attributes just change?	1627	=head2 C<ev_stat> - did the file attributes just change?
1570		1628
1571	This watches a filesystem path for attribute changes. That is, it calls	1629	This watches a file system path for attribute changes. That is, it calls
1572	C<stat> regularly (or when the OS says it changed) and sees if it changed	1630	C<stat> regularly (or when the OS says it changed) and sees if it changed
1573	compared to the last time, invoking the callback if it did.	1631	compared to the last time, invoking the callback if it did.
1574		1632
1575	The path does not need to exist: changing from "path exists" to "path does	1633	The path does not need to exist: changing from "path exists" to "path does
1576	not exist" is a status change like any other. The condition "path does	1634	not exist" is a status change like any other. The condition "path does
…		…
1594	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1595	resource-intensive.	1653	resource-intensive.
1596		1654
1597	At the time of this writing, only the Linux inotify interface is	1655	At the time of this writing, only the Linux inotify interface is
1598	implemented (implementing kqueue support is left as an exercise for the	1656	implemented (implementing kqueue support is left as an exercise for the
		1657	reader, note, however, that the author sees no way of implementing ev_stat
1599	reader). Inotify will be used to give hints only and should not change the	1658	semantics with kqueue). Inotify will be used to give hints only and should
1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1659	not change the semantics of C<ev_stat> watchers, which means that libev
1601	to fall back to regular polling again even with inotify, but changes are	1660	sometimes needs to fall back to regular polling again even with inotify,
1602	usually detected immediately, and if the file exists there will be no	1661	but changes are usually detected immediately, and if the file exists there
1603	polling.	1662	will be no polling.
		1663
		1664	=head3 ABI Issues (Largefile Support)
		1665
		1666	Libev by default (unless the user overrides this) uses the default
		1667	compilation environment, which means that on systems with optionally
		1668	disabled large file support, you get the 32 bit version of the stat
		1669	structure. When using the library from programs that change the ABI to
		1670	use 64 bit file offsets the programs will fail. In that case you have to
		1671	compile libev with the same flags to get binary compatibility. This is
		1672	obviously the case with any flags that change the ABI, but the problem is
		1673	most noticeably with ev_stat and large file support.
1604		1674
1605	=head3 Inotify	1675	=head3 Inotify
1606		1676
1607	When C<inotify (7)> support has been compiled into libev (generally only	1677	When C<inotify (7)> support has been compiled into libev (generally only
1608	available on Linux) and present at runtime, it will be used to speed up	1678	available on Linux) and present at runtime, it will be used to speed up
1609	change detection where possible. The inotify descriptor will be created lazily	1679	change detection where possible. The inotify descriptor will be created lazily
1610	when the first C<ev_stat> watcher is being started.	1680	when the first C<ev_stat> watcher is being started.
1611		1681
1612	Inotify presense does not change the semantics of C<ev_stat> watchers	1682	Inotify presence does not change the semantics of C<ev_stat> watchers
1613	except that changes might be detected earlier, and in some cases, to avoid	1683	except that changes might be detected earlier, and in some cases, to avoid
1614	making regular C<stat> calls. Even in the presense of inotify support	1684	making regular C<stat> calls. Even in the presence of inotify support
1615	there are many cases where libev has to resort to regular C<stat> polling.	1685	there are many cases where libev has to resort to regular C<stat> polling.
1616		1686
1617	(There is no support for kqueue, as apparently it cannot be used to	1687	(There is no support for kqueue, as apparently it cannot be used to
1618	implement this functionality, due to the requirement of having a file	1688	implement this functionality, due to the requirement of having a file
1619	descriptor open on the object at all times).	1689	descriptor open on the object at all times).
1620		1690
1621	=head3 The special problem of stat time resolution	1691	=head3 The special problem of stat time resolution
1622		1692
1623	The C<stat ()> syscall only supports full-second resolution portably, and	1693	The C<stat ()> system call only supports full-second resolution portably, and
1624	even on systems where the resolution is higher, many filesystems still	1694	even on systems where the resolution is higher, many file systems still
1625	only support whole seconds.	1695	only support whole seconds.
1626		1696
1627	That means that, if the time is the only thing that changes, you might	1697	That means that, if the time is the only thing that changes, you can
1628	miss updates: on the first update, C<ev_stat> detects a change and calls	1698	easily miss updates: on the first update, C<ev_stat> detects a change and
1629	your callback, which does something. When there is another update within	1699	calls your callback, which does something. When there is another update
1630	the same second, C<ev_stat> will be unable to detect it.	1700	within the same second, C<ev_stat> will be unable to detect it as the stat
		1701	data does not change.
1631		1702
1632	The solution to this is to delay acting on a change for a second (or till	1703	The solution to this is to delay acting on a change for slightly more
1633	the next second boundary), using a roughly one-second delay C<ev_timer>	1704	than a second (or till slightly after the next full second boundary), using
1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1635	is added to work around small timing inconsistencies of some operating	1706	ev_timer_again (loop, w)>).
1636	systems.	1707
		1708	The C<.02> offset is added to work around small timing inconsistencies
		1709	of some operating systems (where the second counter of the current time
		1710	might be be delayed. One such system is the Linux kernel, where a call to
		1711	C<gettimeofday> might return a timestamp with a full second later than
		1712	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1713	update file times then there will be a small window where the kernel uses
		1714	the previous second to update file times but libev might already execute
		1715	the timer callback).
1637		1716
1638	=head3 Watcher-Specific Functions and Data Members	1717	=head3 Watcher-Specific Functions and Data Members
1639		1718
1640	=over 4	1719	=over 4
1641		1720
…		…
1647	C<path>. The C<interval> is a hint on how quickly a change is expected to	1726	C<path>. The C<interval> is a hint on how quickly a change is expected to
1648	be detected and should normally be specified as C<0> to let libev choose	1727	be detected and should normally be specified as C<0> to let libev choose
1649	a suitable value. The memory pointed to by C<path> must point to the same	1728	a suitable value. The memory pointed to by C<path> must point to the same
1650	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1651		1730
1652	The callback will be receive C<EV_STAT> when a change was detected,	1731	The callback will receive C<EV_STAT> when a change was detected, relative
1653	relative to the attributes at the time the watcher was started (or the	1732	to the attributes at the time the watcher was started (or the last change
1654	last change was detected).	1733	was detected).
1655		1734
1656	=item ev_stat_stat (loop, ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1657		1736
1658	Updates the stat buffer immediately with new values. If you change the	1737	Updates the stat buffer immediately with new values. If you change the
1659	watched path in your callback, you could call this fucntion to avoid	1738	watched path in your callback, you could call this function to avoid
1660	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1661	useful simply to find out the new values.	1740	the only one changing the path). Can also be useful simply to find out the
		1741	new values.
1662		1742
1663	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1664		1744
1665	The most-recently detected attributes of the file. Although the type is of	1745	The most-recently detected attributes of the file. Although the type is
1666	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1746	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1667	suitable for your system. If the C<st_nlink> member is C<0>, then there	1747	suitable for your system, but you can only rely on the POSIX-standardised
		1748	members to be present. If the C<st_nlink> member is C<0>, then there was
1668	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1669		1750
1670	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1671		1752
1672	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1673	C<prev> != C<attr>.	1754	C<prev> != C<attr>, or, more precisely, one or more of these members
		1755	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1756	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1674		1757
1675	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1676		1759
1677	The specified interval.	1760	The specified interval.
1678		1761
1679	=item const char *path [read-only]	1762	=item const char *path [read-only]
1680		1763
1681	The filesystem path that is being watched.	1764	The file system path that is being watched.
1682		1765
1683	=back	1766	=back
1684		1767
1685	=head3 Examples	1768	=head3 Examples
1686		1769
…		…
1732	}	1815	}
1733		1816
1734	...	1817	...
1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	1819	ev_stat_start (loop, &passwd);
1737	ev_timer_init (&timer, timer_cb, 0., 1.01);	1820	ev_timer_init (&timer, timer_cb, 0., 1.02);
1738		1821
1739		1822
1740	=head2 C<ev_idle> - when you've got nothing better to do...	1823	=head2 C<ev_idle> - when you've got nothing better to do...
1741		1824
1742	Idle watchers trigger events when no other events of the same or higher	1825	Idle watchers trigger events when no other events of the same or higher
…		…
1812		1895
1813	This is done by examining in each prepare call which file descriptors need	1896	This is done by examining in each prepare call which file descriptors need
1814	to be watched by the other library, registering C<ev_io> watchers for	1897	to be watched by the other library, registering C<ev_io> watchers for
1815	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1816	provide just this functionality). Then, in the check watcher you check for	1899	provide just this functionality). Then, in the check watcher you check for
1817	any events that occured (by checking the pending status of all watchers	1900	any events that occurred (by checking the pending status of all watchers
1818	and stopping them) and call back into the library. The I/O and timer	1901	and stopping them) and call back into the library. The I/O and timer
1819	callbacks will never actually be called (but must be valid nevertheless,	1902	callbacks will never actually be called (but must be valid nevertheless,
1820	because you never know, you know?).	1903	because you never know, you know?).
1821		1904
1822	As another example, the Perl Coro module uses these hooks to integrate	1905	As another example, the Perl Coro module uses these hooks to integrate
…		…
1830		1913
1831	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1832	priority, to ensure that they are being run before any other watchers	1915	priority, to ensure that they are being run before any other watchers
1833	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1834	too) should not activate ("feed") events into libev. While libev fully	1917	too) should not activate ("feed") events into libev. While libev fully
1835	supports this, they will be called before other C<ev_check> watchers	1918	supports this, they might get executed before other C<ev_check> watchers
1836	did their job. As C<ev_check> watchers are often used to embed other	1919	did their job. As C<ev_check> watchers are often used to embed other
1837	(non-libev) event loops those other event loops might be in an unusable	1920	(non-libev) event loops those other event loops might be in an unusable
1838	state until their C<ev_check> watcher ran (always remind yourself to	1921	state until their C<ev_check> watcher ran (always remind yourself to
1839	coexist peacefully with others).	1922	coexist peacefully with others).
1840		1923
…		…
1855	=head3 Examples	1938	=head3 Examples
1856		1939
1857	There are a number of principal ways to embed other event loops or modules	1940	There are a number of principal ways to embed other event loops or modules
1858	into libev. Here are some ideas on how to include libadns into libev	1941	into libev. Here are some ideas on how to include libadns into libev
1859	(there is a Perl module named C<EV::ADNS> that does this, which you could	1942	(there is a Perl module named C<EV::ADNS> that does this, which you could
1860	use for an actually working example. Another Perl module named C<EV::Glib>	1943	use as a working example. Another Perl module named C<EV::Glib> embeds a
1861	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1944	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1862	into the Glib event loop).	1945	Glib event loop).
1863		1946
1864	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1947	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1865	and in a check watcher, destroy them and call into libadns. What follows	1948	and in a check watcher, destroy them and call into libadns. What follows
1866	is pseudo-code only of course. This requires you to either use a low	1949	is pseudo-code only of course. This requires you to either use a low
1867	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as
…		…
1924		2007
1925	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1926	in the prepare watcher and would dispose of the check watcher.	2009	in the prepare watcher and would dispose of the check watcher.
1927		2010
1928	Method 3: If the module to be embedded supports explicit event	2011	Method 3: If the module to be embedded supports explicit event
1929	notification (adns does), you can also make use of the actual watcher	2012	notification (libadns does), you can also make use of the actual watcher
1930	callbacks, and only destroy/create the watchers in the prepare watcher.	2013	callbacks, and only destroy/create the watchers in the prepare watcher.
1931		2014
1932	static void	2015	static void
1933	timer_cb (EV_P_ ev_timer *w, int revents)	2016	timer_cb (EV_P_ ev_timer *w, int revents)
1934	{	2017	{
…		…
1949	}	2032	}
1950		2033
1951	// do not ever call adns_afterpoll	2034	// do not ever call adns_afterpoll
1952		2035
1953	Method 4: Do not use a prepare or check watcher because the module you	2036	Method 4: Do not use a prepare or check watcher because the module you
1954	want to embed is too inflexible to support it. Instead, youc na override	2037	want to embed is too inflexible to support it. Instead, you can override
1955	their poll function. The drawback with this solution is that the main	2038	their poll function. The drawback with this solution is that the main
1956	loop is now no longer controllable by EV. The C<Glib::EV> module does	2039	loop is now no longer controllable by EV. The C<Glib::EV> module does
1957	this.	2040	this.
1958		2041
1959	static gint	2042	static gint
…		…
2043		2126
2044	Configures the watcher to embed the given loop, which must be	2127	Configures the watcher to embed the given loop, which must be
2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2128	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2046	invoked automatically, otherwise it is the responsibility of the callback	2129	invoked automatically, otherwise it is the responsibility of the callback
2047	to invoke it (it will continue to be called until the sweep has been done,	2130	to invoke it (it will continue to be called until the sweep has been done,
2048	if you do not want thta, you need to temporarily stop the embed watcher).	2131	if you do not want that, you need to temporarily stop the embed watcher).
2049		2132
2050	=item ev_embed_sweep (loop, ev_embed *)	2133	=item ev_embed_sweep (loop, ev_embed *)
2051		2134
2052	Make a single, non-blocking sweep over the embedded loop. This works	2135	Make a single, non-blocking sweep over the embedded loop. This works
2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2054	apropriate way for embedded loops.	2137	appropriate way for embedded loops.
2055		2138
2056	=item struct ev_loop *other [read-only]	2139	=item struct ev_loop *other [read-only]
2057		2140
2058	The embedded event loop.	2141	The embedded event loop.
2059		2142
…		…
2061		2144
2062	=head3 Examples	2145	=head3 Examples
2063		2146
2064	Example: Try to get an embeddable event loop and embed it into the default	2147	Example: Try to get an embeddable event loop and embed it into the default
2065	event loop. If that is not possible, use the default loop. The default	2148	event loop. If that is not possible, use the default loop. The default
2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2068	used).	2151	used).
2069		2152
2070	struct ev_loop *loop_hi = ev_default_init (0);	2153	struct ev_loop *loop_hi = ev_default_init (0);
2071	struct ev_loop *loop_lo = 0;	2154	struct ev_loop *loop_lo = 0;
2072	struct ev_embed embed;	2155	struct ev_embed embed;
…		…
2166		2249
2167	=item queueing from a signal handler context	2250	=item queueing from a signal handler context
2168		2251
2169	To implement race-free queueing, you simply add to the queue in the signal	2252	To implement race-free queueing, you simply add to the queue in the signal
2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for
2171	some fictitiuous SIGUSR1 handler:	2254	some fictitious SIGUSR1 handler:
2172		2255
2173	static ev_async mysig;	2256	static ev_async mysig;
2174		2257
2175	static void	2258	static void
2176	sigusr1_handler (void)	2259	sigusr1_handler (void)
…		…
2250	=item ev_async_send (loop, ev_async *)	2333	=item ev_async_send (loop, ev_async *)
2251		2334
2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2254	C<ev_feed_event>, this call is safe to do in other threads, signal or	2337	C<ev_feed_event>, this call is safe to do in other threads, signal or
2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2256	section below on what exactly this means).	2339	section below on what exactly this means).
2257		2340
2258	This call incurs the overhead of a syscall only once per loop iteration,	2341	This call incurs the overhead of a system call only once per loop iteration,
2259	so while the overhead might be noticable, it doesn't apply to repeated	2342	so while the overhead might be noticeable, it doesn't apply to repeated
2260	calls to C<ev_async_send>.	2343	calls to C<ev_async_send>.
		2344
		2345	=item bool = ev_async_pending (ev_async *)
		2346
		2347	Returns a non-zero value when C<ev_async_send> has been called on the
		2348	watcher but the event has not yet been processed (or even noted) by the
		2349	event loop.
		2350
		2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2352	the loop iterates next and checks for the watcher to have become active,
		2353	it will reset the flag again. C<ev_async_pending> can be used to very
		2354	quickly check whether invoking the loop might be a good idea.
		2355
		2356	Not that this does I<not> check whether the watcher itself is pending, only
		2357	whether it has been requested to make this watcher pending.
2261		2358
2262	=back	2359	=back
2263		2360
2264		2361
2265	=head1 OTHER FUNCTIONS	2362	=head1 OTHER FUNCTIONS
…		…
2276	or timeout without having to allocate/configure/start/stop/free one or	2373	or timeout without having to allocate/configure/start/stop/free one or
2277	more watchers yourself.	2374	more watchers yourself.
2278		2375
2279	If C<fd> is less than 0, then no I/O watcher will be started and events	2376	If C<fd> is less than 0, then no I/O watcher will be started and events
2280	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
2281	C<events> set will be craeted and started.	2378	C<events> set will be created and started.
2282		2379
2283	If C<timeout> is less than 0, then no timeout watcher will be	2380	If C<timeout> is less than 0, then no timeout watcher will be
2284	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2285	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2286	dubious value.	2383	dubious value.
…		…
2311	Feed an event on the given fd, as if a file descriptor backend detected	2408	Feed an event on the given fd, as if a file descriptor backend detected
2312	the given events it.	2409	the given events it.
2313		2410
2314	=item ev_feed_signal_event (ev_loop *loop, int signum)	2411	=item ev_feed_signal_event (ev_loop *loop, int signum)
2315		2412
2316	Feed an event as if the given signal occured (C<loop> must be the default	2413	Feed an event as if the given signal occurred (C<loop> must be the default
2317	loop!).	2414	loop!).
2318		2415
2319	=back	2416	=back
2320		2417
2321		2418
…		…
2337		2434
2338	=item * Priorities are not currently supported. Initialising priorities	2435	=item * Priorities are not currently supported. Initialising priorities
2339	will fail and all watchers will have the same priority, even though there	2436	will fail and all watchers will have the same priority, even though there
2340	is an ev_pri field.	2437	is an ev_pri field.
2341		2438
		2439	=item * In libevent, the last base created gets the signals, in libev, the
		2440	first base created (== the default loop) gets the signals.
		2441
2342	=item * Other members are not supported.	2442	=item * Other members are not supported.
2343		2443
2344	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2444	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2345	to use the libev header file and library.	2445	to use the libev header file and library.
2346		2446
2347	=back	2447	=back
2348		2448
2349	=head1 C++ SUPPORT	2449	=head1 C++ SUPPORT
2350		2450
2351	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2451	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2352	you to use some convinience methods to start/stop watchers and also change	2452	you to use some convenience methods to start/stop watchers and also change
2353	the callback model to a model using method callbacks on objects.	2453	the callback model to a model using method callbacks on objects.
2354		2454
2355	To use it,	2455	To use it,
2356		2456
2357	#include <ev++.h>	2457	#include <ev++.h>
…		…
2458	=item w->set (struct ev_loop *)	2558	=item w->set (struct ev_loop *)
2459		2559
2460	Associates a different C<struct ev_loop> with this watcher. You can only	2560	Associates a different C<struct ev_loop> with this watcher. You can only
2461	do this when the watcher is inactive (and not pending either).	2561	do this when the watcher is inactive (and not pending either).
2462		2562
2463	=item w->set ([args])	2563	=item w->set ([arguments])
2464		2564
2465	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2565	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2466	called at least once. Unlike the C counterpart, an active watcher gets	2566	called at least once. Unlike the C counterpart, an active watcher gets
2467	automatically stopped and restarted when reconfiguring it with this	2567	automatically stopped and restarted when reconfiguring it with this
2468	method.	2568	method.
2469		2569
2470	=item w->start ()	2570	=item w->start ()
…		…
2512		2612
2513		2613
2514	=head1 OTHER LANGUAGE BINDINGS	2614	=head1 OTHER LANGUAGE BINDINGS
2515		2615
2516	Libev does not offer other language bindings itself, but bindings for a	2616	Libev does not offer other language bindings itself, but bindings for a
2517	numbe rof languages exist in the form of third-party packages. If you know	2617	number of languages exist in the form of third-party packages. If you know
2518	any interesting language binding in addition to the ones listed here, drop	2618	any interesting language binding in addition to the ones listed here, drop
2519	me a note.	2619	me a note.
2520		2620
2521	=over 4	2621	=over 4
2522		2622
…		…
2532	L<http://software.schmorp.de/pkg/EV>.	2632	L<http://software.schmorp.de/pkg/EV>.
2533		2633
2534	=item Ruby	2634	=item Ruby
2535		2635
2536	Tony Arcieri has written a ruby extension that offers access to a subset	2636	Tony Arcieri has written a ruby extension that offers access to a subset
2537	of the libev API and adds filehandle abstractions, asynchronous DNS and	2637	of the libev API and adds file handle abstractions, asynchronous DNS and
2538	more on top of it. It can be found via gem servers. Its homepage is at	2638	more on top of it. It can be found via gem servers. Its homepage is at
2539	L<http://rev.rubyforge.org/>.	2639	L<http://rev.rubyforge.org/>.
2540		2640
2541	=item D	2641	=item D
2542		2642
…		…
2546	=back	2646	=back
2547		2647
2548		2648
2549	=head1 MACRO MAGIC	2649	=head1 MACRO MAGIC
2550		2650
2551	Libev can be compiled with a variety of options, the most fundamantal	2651	Libev can be compiled with a variety of options, the most fundamental
2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2652	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2553	functions and callbacks have an initial C<struct ev_loop *> argument.	2653	functions and callbacks have an initial C<struct ev_loop *> argument.
2554		2654
2555	To make it easier to write programs that cope with either variant, the	2655	To make it easier to write programs that cope with either variant, the
2556	following macros are defined:	2656	following macros are defined:
…		…
2587		2687
2588	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2589		2689
2590	Similar to the other two macros, this gives you the value of the default	2690	Similar to the other two macros, this gives you the value of the default
2591	loop, if multiple loops are supported ("ev loop default").	2691	loop, if multiple loops are supported ("ev loop default").
		2692
		2693	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2694
		2695	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2696	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2697	is undefined when the default loop has not been initialised by a previous
		2698	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2699
		2700	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2701	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2592		2702
2593	=back	2703	=back
2594		2704
2595	Example: Declare and initialise a check watcher, utilising the above	2705	Example: Declare and initialise a check watcher, utilising the above
2596	macros so it will work regardless of whether multiple loops are supported	2706	macros so it will work regardless of whether multiple loops are supported
…		…
2620	libev somewhere in your source tree).	2730	libev somewhere in your source tree).
2621		2731
2622	=head2 FILESETS	2732	=head2 FILESETS
2623		2733
2624	Depending on what features you need you need to include one or more sets of files	2734	Depending on what features you need you need to include one or more sets of files
2625	in your app.	2735	in your application.
2626		2736
2627	=head3 CORE EVENT LOOP	2737	=head3 CORE EVENT LOOP
2628		2738
2629	To include only the libev core (all the C<ev_*> functions), with manual	2739	To include only the libev core (all the C<ev_*> functions), with manual
2630	configuration (no autoconf):	2740	configuration (no autoconf):
…		…
2681	event.h	2791	event.h
2682	event.c	2792	event.c
2683		2793
2684	=head3 AUTOCONF SUPPORT	2794	=head3 AUTOCONF SUPPORT
2685		2795
2686	Instead of using C<EV_STANDALONE=1> and providing your config in	2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2687	whatever way you want, you can also C<m4_include([libev.m4])> in your	2797	whatever way you want, you can also C<m4_include([libev.m4])> in your
2688	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2689	include F<config.h> and configure itself accordingly.	2799	include F<config.h> and configure itself accordingly.
2690		2800
2691	For this of course you need the m4 file:	2801	For this of course you need the m4 file:
2692		2802
2693	libev.m4	2803	libev.m4
2694		2804
2695	=head2 PREPROCESSOR SYMBOLS/MACROS	2805	=head2 PREPROCESSOR SYMBOLS/MACROS
2696		2806
2697	Libev can be configured via a variety of preprocessor symbols you have to define	2807	Libev can be configured via a variety of preprocessor symbols you have to
2698	before including any of its files. The default is not to build for multiplicity	2808	define before including any of its files. The default in the absence of
2699	and only include the select backend.	2809	autoconf is noted for every option.
2700		2810
2701	=over 4	2811	=over 4
2702		2812
2703	=item EV_STANDALONE	2813	=item EV_STANDALONE
2704		2814
…		…
2709	F<event.h> that are not directly supported by the libev core alone.	2819	F<event.h> that are not directly supported by the libev core alone.
2710		2820
2711	=item EV_USE_MONOTONIC	2821	=item EV_USE_MONOTONIC
2712		2822
2713	If defined to be C<1>, libev will try to detect the availability of the	2823	If defined to be C<1>, libev will try to detect the availability of the
2714	monotonic clock option at both compiletime and runtime. Otherwise no use	2824	monotonic clock option at both compile time and runtime. Otherwise no use
2715	of the monotonic clock option will be attempted. If you enable this, you	2825	of the monotonic clock option will be attempted. If you enable this, you
2716	usually have to link against librt or something similar. Enabling it when	2826	usually have to link against librt or something similar. Enabling it when
2717	the functionality isn't available is safe, though, although you have	2827	the functionality isn't available is safe, though, although you have
2718	to make sure you link against any libraries where the C<clock_gettime>	2828	to make sure you link against any libraries where the C<clock_gettime>
2719	function is hiding in (often F<-lrt>).	2829	function is hiding in (often F<-lrt>).
2720		2830
2721	=item EV_USE_REALTIME	2831	=item EV_USE_REALTIME
2722		2832
2723	If defined to be C<1>, libev will try to detect the availability of the	2833	If defined to be C<1>, libev will try to detect the availability of the
2724	realtime clock option at compiletime (and assume its availability at	2834	real-time clock option at compile time (and assume its availability at
2725	runtime if successful). Otherwise no use of the realtime clock option will	2835	runtime if successful). Otherwise no use of the real-time clock option will
2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2729		2839
2730	=item EV_USE_NANOSLEEP	2840	=item EV_USE_NANOSLEEP
2731		2841
2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2733	and will use it for delays. Otherwise it will use C<select ()>.	2843	and will use it for delays. Otherwise it will use C<select ()>.
2734		2844
		2845	=item EV_USE_EVENTFD
		2846
		2847	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2848	available and will probe for kernel support at runtime. This will improve
		2849	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2850	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2851	2.7 or newer, otherwise disabled.
		2852
2735	=item EV_USE_SELECT	2853	=item EV_USE_SELECT
2736		2854
2737	If undefined or defined to be C<1>, libev will compile in support for the	2855	If undefined or defined to be C<1>, libev will compile in support for the
2738	C<select>(2) backend. No attempt at autodetection will be done: if no	2856	C<select>(2) backend. No attempt at auto-detection will be done: if no
2739	other method takes over, select will be it. Otherwise the select backend	2857	other method takes over, select will be it. Otherwise the select backend
2740	will not be compiled in.	2858	will not be compiled in.
2741		2859
2742	=item EV_SELECT_USE_FD_SET	2860	=item EV_SELECT_USE_FD_SET
2743		2861
2744	If defined to C<1>, then the select backend will use the system C<fd_set>	2862	If defined to C<1>, then the select backend will use the system C<fd_set>
2745	structure. This is useful if libev doesn't compile due to a missing	2863	structure. This is useful if libev doesn't compile due to a missing
2746	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2747	exotic systems. This usually limits the range of file descriptors to some	2865	exotic systems. This usually limits the range of file descriptors to some
2748	low limit such as 1024 or might have other limitations (winsocket only	2866	low limit such as 1024 or might have other limitations (winsocket only
2749	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2750	influence the size of the C<fd_set> used.	2868	influence the size of the C<fd_set> used.
2751		2869
…		…
2775		2893
2776	=item EV_USE_EPOLL	2894	=item EV_USE_EPOLL
2777		2895
2778	If defined to be C<1>, libev will compile in support for the Linux	2896	If defined to be C<1>, libev will compile in support for the Linux
2779	C<epoll>(7) backend. Its availability will be detected at runtime,	2897	C<epoll>(7) backend. Its availability will be detected at runtime,
2780	otherwise another method will be used as fallback. This is the	2898	otherwise another method will be used as fallback. This is the preferred
2781	preferred backend for GNU/Linux systems.	2899	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2900	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2782		2901
2783	=item EV_USE_KQUEUE	2902	=item EV_USE_KQUEUE
2784		2903
2785	If defined to be C<1>, libev will compile in support for the BSD style	2904	If defined to be C<1>, libev will compile in support for the BSD style
2786	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2905	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2799	otherwise another method will be used as fallback. This is the preferred	2918	otherwise another method will be used as fallback. This is the preferred
2800	backend for Solaris 10 systems.	2919	backend for Solaris 10 systems.
2801		2920
2802	=item EV_USE_DEVPOLL	2921	=item EV_USE_DEVPOLL
2803		2922
2804	reserved for future expansion, works like the USE symbols above.	2923	Reserved for future expansion, works like the USE symbols above.
2805		2924
2806	=item EV_USE_INOTIFY	2925	=item EV_USE_INOTIFY
2807		2926
2808	If defined to be C<1>, libev will compile in support for the Linux inotify	2927	If defined to be C<1>, libev will compile in support for the Linux inotify
2809	interface to speed up C<ev_stat> watchers. Its actual availability will	2928	interface to speed up C<ev_stat> watchers. Its actual availability will
2810	be detected at runtime.	2929	be detected at runtime. If undefined, it will be enabled if the headers
		2930	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2811		2931
2812	=item EV_ATOMIC_T	2932	=item EV_ATOMIC_T
2813		2933
2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	2934	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2815	access is atomic with respect to other threads or signal contexts. No such	2935	access is atomic with respect to other threads or signal contexts. No such
2816	type is easily found in the C language, so you can provide your own type	2936	type is easily found in the C language, so you can provide your own type
2817	that you know is safe for your purposes. It is used both for signal handler "locking"	2937	that you know is safe for your purposes. It is used both for signal handler "locking"
2818	as well as for signal and thread safety in C<ev_async> watchers.	2938	as well as for signal and thread safety in C<ev_async> watchers.
2819		2939
2820	In the absense of this define, libev will use C<sig_atomic_t volatile>	2940	In the absence of this define, libev will use C<sig_atomic_t volatile>
2821	(from F<signal.h>), which is usually good enough on most platforms.	2941	(from F<signal.h>), which is usually good enough on most platforms.
2822		2942
2823	=item EV_H	2943	=item EV_H
2824		2944
2825	The name of the F<ev.h> header file used to include it. The default if	2945	The name of the F<ev.h> header file used to include it. The default if
…		…
2864	When doing priority-based operations, libev usually has to linearly search	2984	When doing priority-based operations, libev usually has to linearly search
2865	all the priorities, so having many of them (hundreds) uses a lot of space	2985	all the priorities, so having many of them (hundreds) uses a lot of space
2866	and time, so using the defaults of five priorities (-2 .. +2) is usually	2986	and time, so using the defaults of five priorities (-2 .. +2) is usually
2867	fine.	2987	fine.
2868		2988
2869	If your embedding app does not need any priorities, defining these both to	2989	If your embedding application does not need any priorities, defining these both to
2870	C<0> will save some memory and cpu.	2990	C<0> will save some memory and CPU.
2871		2991
2872	=item EV_PERIODIC_ENABLE	2992	=item EV_PERIODIC_ENABLE
2873		2993
2874	If undefined or defined to be C<1>, then periodic timers are supported. If	2994	If undefined or defined to be C<1>, then periodic timers are supported. If
2875	defined to be C<0>, then they are not. Disabling them saves a few kB of	2995	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2902	defined to be C<0>, then they are not.	3022	defined to be C<0>, then they are not.
2903		3023
2904	=item EV_MINIMAL	3024	=item EV_MINIMAL
2905		3025
2906	If you need to shave off some kilobytes of code at the expense of some	3026	If you need to shave off some kilobytes of code at the expense of some
2907	speed, define this symbol to C<1>. Currently only used for gcc to override	3027	speed, define this symbol to C<1>. Currently this is used to override some
2908	some inlining decisions, saves roughly 30% codesize of amd64.	3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3029	much smaller 2-heap for timer management over the default 4-heap.
2909		3030
2910	=item EV_PID_HASHSIZE	3031	=item EV_PID_HASHSIZE
2911		3032
2912	C<ev_child> watchers use a small hash table to distribute workload by	3033	C<ev_child> watchers use a small hash table to distribute workload by
2913	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2919	C<ev_stat> watchers use a small hash table to distribute workload by	3040	C<ev_stat> watchers use a small hash table to distribute workload by
2920	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2921	usually more than enough. If you need to manage thousands of C<ev_stat>	3042	usually more than enough. If you need to manage thousands of C<ev_stat>
2922	watchers you might want to increase this value (I<must> be a power of	3043	watchers you might want to increase this value (I<must> be a power of
2923	two).	3044	two).
		3045
		3046	=item EV_USE_4HEAP
		3047
		3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3050	to C<1>. The 4-heap uses more complicated (longer) code but has
		3051	noticeably faster performance with many (thousands) of watchers.
		3052
		3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3054	(disabled).
		3055
		3056	=item EV_HEAP_CACHE_AT
		3057
		3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3059	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3062	but avoids random read accesses on heap changes. This improves performance
		3063	noticeably with with many (hundreds) of watchers.
		3064
		3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3066	(disabled).
		3067
		3068	=item EV_VERIFY
		3069
		3070	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3071	be done: If set to C<0>, no internal verification code will be compiled
		3072	in. If set to C<1>, then verification code will be compiled in, but not
		3073	called. If set to C<2>, then the internal verification code will be
		3074	called once per loop, which can slow down libev. If set to C<3>, then the
		3075	verification code will be called very frequently, which will slow down
		3076	libev considerably.
		3077
		3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3079	C<0.>
2924		3080
2925	=item EV_COMMON	3081	=item EV_COMMON
2926		3082
2927	By default, all watchers have a C<void *data> member. By redefining	3083	By default, all watchers have a C<void *data> member. By redefining
2928	this macro to a something else you can include more and other types of	3084	this macro to a something else you can include more and other types of
…		…
2948	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2949	method calls instead of plain function calls in C++.	3105	method calls instead of plain function calls in C++.
2950		3106
2951	=head2 EXPORTED API SYMBOLS	3107	=head2 EXPORTED API SYMBOLS
2952		3108
2953	If you need to re-export the API (e.g. via a dll) and you need a list of	3109	If you need to re-export the API (e.g. via a DLL) and you need a list of
2954	exported symbols, you can use the provided F<Symbol.*> files which list	3110	exported symbols, you can use the provided F<Symbol.*> files which list
2955	all public symbols, one per line:	3111	all public symbols, one per line:
2956		3112
2957	Symbols.ev for libev proper	3113	Symbols.ev for libev proper
2958	Symbols.event for the libevent emulation	3114	Symbols.event for the libevent emulation
2959		3115
2960	This can also be used to rename all public symbols to avoid clashes with	3116	This can also be used to rename all public symbols to avoid clashes with
2961	multiple versions of libev linked together (which is obviously bad in	3117	multiple versions of libev linked together (which is obviously bad in
2962	itself, but sometimes it is inconvinient to avoid this).	3118	itself, but sometimes it is inconvenient to avoid this).
2963		3119
2964	A sed command like this will create wrapper C<#define>'s that you need to	3120	A sed command like this will create wrapper C<#define>'s that you need to
2965	include before including F<ev.h>:	3121	include before including F<ev.h>:
2966		3122
2967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3123	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3002		3158
3003	#include "ev_cpp.h"	3159	#include "ev_cpp.h"
3004	#include "ev.c"	3160	#include "ev.c"
3005		3161
3006		3162
		3163	=head1 THREADS AND COROUTINES
		3164
		3165	=head2 THREADS
		3166
		3167	Libev itself is completely thread-safe, but it uses no locking. This
		3168	means that you can use as many loops as you want in parallel, as long as
		3169	only one thread ever calls into one libev function with the same loop
		3170	parameter.
		3171
		3172	Or put differently: calls with different loop parameters can be done in
		3173	parallel from multiple threads, calls with the same loop parameter must be
		3174	done serially (but can be done from different threads, as long as only one
		3175	thread ever is inside a call at any point in time, e.g. by using a mutex
		3176	per loop).
		3177
		3178	If you want to know which design is best for your problem, then I cannot
		3179	help you but by giving some generic advice:
		3180
		3181	=over 4
		3182
		3183	=item * most applications have a main thread: use the default libev loop
		3184	in that thread, or create a separate thread running only the default loop.
		3185
		3186	This helps integrating other libraries or software modules that use libev
		3187	themselves and don't care/know about threading.
		3188
		3189	=item * one loop per thread is usually a good model.
		3190
		3191	Doing this is almost never wrong, sometimes a better-performance model
		3192	exists, but it is always a good start.
		3193
		3194	=item * other models exist, such as the leader/follower pattern, where one
		3195	loop is handed through multiple threads in a kind of round-robin fashion.
		3196
		3197	Choosing a model is hard - look around, learn, know that usually you can do
		3198	better than you currently do :-)
		3199
		3200	=item * often you need to talk to some other thread which blocks in the
		3201	event loop - C<ev_async> watchers can be used to wake them up from other
		3202	threads safely (or from signal contexts...).
		3203
		3204	=back
		3205
		3206	=head2 COROUTINES
		3207
		3208	Libev is much more accommodating to coroutines ("cooperative threads"):
		3209	libev fully supports nesting calls to it's functions from different
		3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3211	different coroutines and switch freely between both coroutines running the
		3212	loop, as long as you don't confuse yourself). The only exception is that
		3213	you must not do this from C<ev_periodic> reschedule callbacks.
		3214
		3215	Care has been invested into making sure that libev does not keep local
		3216	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3217	switches.
		3218
		3219
3007	=head1 COMPLEXITIES	3220	=head1 COMPLEXITIES
3008		3221
3009	In this section the complexities of (many of) the algorithms used inside	3222	In this section the complexities of (many of) the algorithms used inside
3010	libev will be explained. For complexity discussions about backends see the	3223	libev will be explained. For complexity discussions about backends see the
3011	documentation for C<ev_default_init>.	3224	documentation for C<ev_default_init>.
…		…
3041	correct watcher to remove. The lists are usually short (you don't usually	3254	correct watcher to remove. The lists are usually short (you don't usually
3042	have many watchers waiting for the same fd or signal).	3255	have many watchers waiting for the same fd or signal).
3043		3256
3044	=item Finding the next timer in each loop iteration: O(1)	3257	=item Finding the next timer in each loop iteration: O(1)
3045		3258
3046	By virtue of using a binary heap, the next timer is always found at the	3259	By virtue of using a binary or 4-heap, the next timer is always found at a
3047	beginning of the storage array.	3260	fixed position in the storage array.
3048		3261
3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3050		3263
3051	A change means an I/O watcher gets started or stopped, which requires	3264	A change means an I/O watcher gets started or stopped, which requires
3052	libev to recalculate its status (and possibly tell the kernel, depending	3265	libev to recalculate its status (and possibly tell the kernel, depending
3053	on backend and wether C<ev_io_set> was used).	3266	on backend and whether C<ev_io_set> was used).
3054		3267
3055	=item Activating one watcher (putting it into the pending state): O(1)	3268	=item Activating one watcher (putting it into the pending state): O(1)
3056		3269
3057	=item Priority handling: O(number_of_priorities)	3270	=item Priority handling: O(number_of_priorities)
3058		3271
…		…
3065		3278
3066	=item Processing ev_async_send: O(number_of_async_watchers)	3279	=item Processing ev_async_send: O(number_of_async_watchers)
3067		3280
3068	=item Processing signals: O(max_signal_number)	3281	=item Processing signals: O(max_signal_number)
3069		3282
3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>	3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3071	calls in the current loop iteration. Checking for async and signal events	3284	calls in the current loop iteration. Checking for async and signal events
3072	involves iterating over all running async watchers or all signal numbers.	3285	involves iterating over all running async watchers or all signal numbers.
3073		3286
3074	=back	3287	=back
3075		3288
3076		3289
3077	=head1 Win32 platform limitations and workarounds	3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3078		3291
3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3080	requires, and its I/O model is fundamentally incompatible with the POSIX	3293	requires, and its I/O model is fundamentally incompatible with the POSIX
3081	model. Libev still offers limited functionality on this platform in	3294	model. Libev still offers limited functionality on this platform in
3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3083	descriptors. This only applies when using Win32 natively, not when using	3296	descriptors. This only applies when using Win32 natively, not when using
3084	e.g. cygwin.	3297	e.g. cygwin.
3085		3298
		3299	Lifting these limitations would basically require the full
		3300	re-implementation of the I/O system. If you are into these kinds of
		3301	things, then note that glib does exactly that for you in a very portable
		3302	way (note also that glib is the slowest event library known to man).
		3303
3086	There is no supported compilation method available on windows except	3304	There is no supported compilation method available on windows except
3087	embedding it into other applications.	3305	embedding it into other applications.
3088		3306
		3307	Not a libev limitation but worth mentioning: windows apparently doesn't
		3308	accept large writes: instead of resulting in a partial write, windows will
		3309	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3310	so make sure you only write small amounts into your sockets (less than a
		3311	megabyte seems safe, but thsi apparently depends on the amount of memory
		3312	available).
		3313
3089	Due to the many, low, and arbitrary limits on the win32 platform and the	3314	Due to the many, low, and arbitrary limits on the win32 platform and
3090	abysmal performance of winsockets, using a large number of sockets is not	3315	the abysmal performance of winsockets, using a large number of sockets
3091	recommended (and not reasonable). If your program needs to use more than	3316	is not recommended (and not reasonable). If your program needs to use
3092	a hundred or so sockets, then likely it needs to use a totally different	3317	more than a hundred or so sockets, then likely it needs to use a totally
3093	implementation for windows, as libev offers the POSIX model, which cannot	3318	different implementation for windows, as libev offers the POSIX readiness
3094	be implemented efficiently on windows (microsoft monopoly games).	3319	notification model, which cannot be implemented efficiently on windows
		3320	(Microsoft monopoly games).
3095		3321
3096	=over 4	3322	=over 4
3097		3323
3098	=item The winsocket select function	3324	=item The winsocket select function
3099		3325
3100	The winsocket C<select> function doesn't follow POSIX in that it requires	3326	The winsocket C<select> function doesn't follow POSIX in that it
3101	socket I<handles> and not socket I<file descriptors>. This makes select	3327	requires socket I<handles> and not socket I<file descriptors> (it is
3102	very inefficient, and also requires a mapping from file descriptors	3328	also extremely buggy). This makes select very inefficient, and also
3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3329	requires a mapping from file descriptors to socket handles. See the
3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3105	symbols for more info.	3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3106		3332
3107	The configuration for a "naked" win32 using the microsoft runtime	3333	The configuration for a "naked" win32 using the Microsoft runtime
3108	libraries and raw winsocket select is:	3334	libraries and raw winsocket select is:
3109		3335
3110	#define EV_USE_SELECT 1	3336	#define EV_USE_SELECT 1
3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3112		3338
3113	Note that winsockets handling of fd sets is O(n), so you can easily get a	3339	Note that winsockets handling of fd sets is O(n), so you can easily get a
3114	complexity in the O(n²) range when using win32.	3340	complexity in the O(n²) range when using win32.
3115		3341
3116	=item Limited number of file descriptors	3342	=item Limited number of file descriptors
3117		3343
3118	Windows has numerous arbitrary (and low) limits on things. Early versions	3344	Windows has numerous arbitrary (and low) limits on things.
3119	of winsocket's select only supported waiting for a max. of C<64> handles	3345
		3346	Early versions of winsocket's select only supported waiting for a maximum
3120	(probably owning to the fact that all windows kernels can only wait for	3347	of C<64> handles (probably owning to the fact that all windows kernels
3121	C<64> things at the same time internally; microsoft recommends spawning a	3348	can only wait for C<64> things at the same time internally; Microsoft
3122	chain of threads and wait for 63 handles and the previous thread in each).	3349	recommends spawning a chain of threads and wait for 63 handles and the
		3350	previous thread in each. Great).
3123		3351
3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3352	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3125	to some high number (e.g. C<2048>) before compiling the winsocket select	3353	to some high number (e.g. C<2048>) before compiling the winsocket select
3126	call (which might be in libev or elsewhere, for example, perl does its own	3354	call (which might be in libev or elsewhere, for example, perl does its own
3127	select emulation on windows).	3355	select emulation on windows).
3128		3356
3129	Another limit is the number of file descriptors in the microsoft runtime	3357	Another limit is the number of file descriptors in the Microsoft runtime
3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3358	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3131	or something like this inside microsoft). You can increase this by calling	3359	or something like this inside Microsoft). You can increase this by calling
3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3360	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3133	arbitrary limit), but is broken in many versions of the microsoft runtime	3361	arbitrary limit), but is broken in many versions of the Microsoft runtime
3134	libraries.	3362	libraries.
3135		3363
3136	This might get you to about C<512> or C<2048> sockets (depending on	3364	This might get you to about C<512> or C<2048> sockets (depending on
3137	windows version and/or the phase of the moon). To get more, you need to	3365	windows version and/or the phase of the moon). To get more, you need to
3138	wrap all I/O functions and provide your own fd management, but the cost of	3366	wrap all I/O functions and provide your own fd management, but the cost of
3139	calling select (O(n²)) will likely make this unworkable.	3367	calling select (O(n²)) will likely make this unworkable.
3140		3368
3141	=back	3369	=back
3142		3370
3143		3371
		3372	=head1 PORTABILITY REQUIREMENTS
		3373
		3374	In addition to a working ISO-C implementation, libev relies on a few
		3375	additional extensions:
		3376
		3377	=over 4
		3378
		3379	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3380
		3381	The type C<sig_atomic_t volatile> (or whatever is defined as
		3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3383	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3384	believed to be sufficiently portable.
		3385
		3386	=item C<sigprocmask> must work in a threaded environment
		3387
		3388	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3389	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3390	pthread implementations will either allow C<sigprocmask> in the "main
		3391	thread" or will block signals process-wide, both behaviours would
		3392	be compatible with libev. Interaction between C<sigprocmask> and
		3393	C<pthread_sigmask> could complicate things, however.
		3394
		3395	The most portable way to handle signals is to block signals in all threads
		3396	except the initial one, and run the default loop in the initial thread as
		3397	well.
		3398
		3399	=item C<long> must be large enough for common memory allocation sizes
		3400
		3401	To improve portability and simplify using libev, libev uses C<long>
		3402	internally instead of C<size_t> when allocating its data structures. On
		3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3404	is still at least 31 bits everywhere, which is enough for hundreds of
		3405	millions of watchers.
		3406
		3407	=item C<double> must hold a time value in seconds with enough accuracy
		3408
		3409	The type C<double> is used to represent timestamps. It is required to
		3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3411	enough for at least into the year 4000. This requirement is fulfilled by
		3412	implementations implementing IEEE 754 (basically all existing ones).
		3413
		3414	=back
		3415
		3416	If you know of other additional requirements drop me a note.
		3417
		3418
		3419	=head1 COMPILER WARNINGS
		3420
		3421	Depending on your compiler and compiler settings, you might get no or a
		3422	lot of warnings when compiling libev code. Some people are apparently
		3423	scared by this.
		3424
		3425	However, these are unavoidable for many reasons. For one, each compiler
		3426	has different warnings, and each user has different tastes regarding
		3427	warning options. "Warn-free" code therefore cannot be a goal except when
		3428	targeting a specific compiler and compiler-version.
		3429
		3430	Another reason is that some compiler warnings require elaborate
		3431	workarounds, or other changes to the code that make it less clear and less
		3432	maintainable.
		3433
		3434	And of course, some compiler warnings are just plain stupid, or simply
		3435	wrong (because they don't actually warn about the condition their message
		3436	seems to warn about).
		3437
		3438	While libev is written to generate as few warnings as possible,
		3439	"warn-free" code is not a goal, and it is recommended not to build libev
		3440	with any compiler warnings enabled unless you are prepared to cope with
		3441	them (e.g. by ignoring them). Remember that warnings are just that:
		3442	warnings, not errors, or proof of bugs.
		3443
		3444
		3445	=head1 VALGRIND
		3446
		3447	Valgrind has a special section here because it is a popular tool that is
		3448	highly useful, but valgrind reports are very hard to interpret.
		3449
		3450	If you think you found a bug (memory leak, uninitialised data access etc.)
		3451	in libev, then check twice: If valgrind reports something like:
		3452
		3453	==2274== definitely lost: 0 bytes in 0 blocks.
		3454	==2274== possibly lost: 0 bytes in 0 blocks.
		3455	==2274== still reachable: 256 bytes in 1 blocks.
		3456
		3457	Then there is no memory leak. Similarly, under some circumstances,
		3458	valgrind might report kernel bugs as if it were a bug in libev, or it
		3459	might be confused (it is a very good tool, but only a tool).
		3460
		3461	If you are unsure about something, feel free to contact the mailing list
		3462	with the full valgrind report and an explanation on why you think this is
		3463	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3464	no bug" answer and take the chance of learning how to interpret valgrind
		3465	properly.
		3466
		3467	If you need, for some reason, empty reports from valgrind for your project
		3468	I suggest using suppression lists.
		3469
		3470
3144	=head1 AUTHOR	3471	=head1 AUTHOR
3145		3472
3146	Marc Lehmann <libev@schmorp.de>.	3473	Marc Lehmann <libev@schmorp.de>.
3147		3474

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