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Revision 1.153 by root, Fri May 9 15:52:13 2008 UTC vs.
Revision 1.213 by root, Wed Nov 5 02:48:45 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
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
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
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
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
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
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
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)) [NOT REENTRANT]
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 are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	250	}
230		251
231	...	252	...
232	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
233		254
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		256
236	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
237	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
238	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
239	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
240	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
241	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
242	(such as abort).	263	(such as abort).
243		264
244	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.
…		…
255		276
256	=back	277	=back
257		278
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		280
260	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 C<struct>
261	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
263		288
264	=over 4	289	=over 4
265		290
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		292
…		…
273	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
274	function.	299	function.
275		300
276	Note that this function is I<not> thread-safe, so if you want to use it	301	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
279		304
280	The default loop is the only loop that can handle C<ev_signal> and	305	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	306	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	307	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	308	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	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	310	C<ev_default_init>.
286		311
287	The flags argument can be used to specify special behaviour or specific	312	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	321	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	322	thing, believe me).
298		323
299	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
300		325
301	If this flag bit is ored into the flag value (or the program runs setuid	326	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	327	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	329	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	330	useful to try out specific backends to test their performance, or to work
306	around bugs.	331	around bugs.
…		…
313		338
314	This works by calling C<getpid ()> on every iteration of the loop,	339	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	340	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	341	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	342	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	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
320		345
321	The big advantage of this flag is that you can forget about fork (and	346	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	347	forget about forgetting to tell libev about forking) when you use this
323	flag.	348	flag.
324		349
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	351	environment variable.
327		352
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		354
330	This is your standard select(2) backend. Not I<completely> standard, as	355	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	357	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	358	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.	359	usually the fastest backend for a low number of (low-numbered :) fds.
335		360
336	To get good performance out of this backend you need a high amount of	361	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	362	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	363	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	364	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	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
342		371
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		373
345	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	376	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	377	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	379	performance tips.
351		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		385
354	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	390
359	cases and requiring a syscall per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
361		407
362	While stopping, setting and starting an I/O watcher in the same iteration	408	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	409	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	410	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
367		413	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		414
372	Best performance from this backend is achieved by not unregistering all	415	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.	416	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	417	i.e. keep at least one watcher active per fd at all times. Stopping and
		418	starting a watcher (without re-setting it) also usually doesn't cause
		419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
375		422
		423	All this means that, in practise, C<EVBACKEND_SELECT> is as fast or faster
		424	then epoll for maybe up to a hundred file descriptors. So sad.
		425
376	While nominally embeddeble in other event loops, this feature is broken in	426	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	427	all kernel versions tested so far.
		428
		429	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		430	C<EVBACKEND_POLL>.
378		431
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	432	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		433
381	Kqueue deserves special mention, as at the time of this writing, it	434	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	435	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	436	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"	437	it's completely useless). Unlike epoll, however, whose brokenness
		438	is by design, these kqueue bugs can (and eventually will) be fixed
		439	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	440	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	441	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	442	system like NetBSD.
388		443
389	You still can embed kqueue into a normal poll or select backend and use it	444	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	445	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	446	the target platform). See C<ev_embed> watchers for more info.
392		447
393	It scales in the same way as the epoll backend, but the interface to the	448	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	449	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	450	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	451	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	452	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	453	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		454	cases
399		455
400	This backend usually performs well under most conditions.	456	This backend usually performs well under most conditions.
401		457
402	While nominally embeddable in other event loops, this doesn't work	458	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	459	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	460	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	461	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	462	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	463	using it only for sockets.
		464
		465	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		466	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		467	C<NOTE_EOF>.
408		468
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	469	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		470
411	This is not implemented yet (and might never be, unless you send me an	471	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	472	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	476	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		477
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	478	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)).	479	it's really slow, but it still scales very well (O(active_fds)).
420		480
421	Please note that solaris event ports can deliver a lot of spurious	481	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	482	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	483	blocking when no data (or space) is available.
424		484
425	While this backend scales well, it requires one system call per active	485	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	486	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	487	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	488	might perform better.
429		489
430	On the positive side, ignoring the spurious readyness notifications, this	490	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	491	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	492	in all tests and is fully embeddable, which is a rare feat among the
		493	OS-specific backends (I vastly prefer correctness over speed hacks).
		494
		495	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		496	C<EVBACKEND_POLL>.
433		497
434	=item C<EVBACKEND_ALL>	498	=item C<EVBACKEND_ALL>
435		499
436	Try all backends (even potentially broken ones that wouldn't be tried	500	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	501	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		503
440	It is definitely not recommended to use this flag.	504	It is definitely not recommended to use this flag.
441		505
442	=back	506	=back
443		507
444	If one or more of these are ored into the flags value, then only these	508	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	509	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.	510	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		511
448	The most typical usage is like this:	512	Example: This is the most typical usage.
449		513
450	if (!ev_default_loop (0))	514	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	515	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		516
453	Restrict libev to the select and poll backends, and do not allow	517	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	518	environment settings to be taken into account:
455		519
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	520	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		521
458	Use whatever libev has to offer, but make sure that kqueue is used if	522	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	523	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	524	private event loop and only if you know the OS supports your types of
		525	fds):
461		526
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	527	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		528
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	529	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		530
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	531	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	532	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	537	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	538	default loop in the "main" or "initial" thread.
474		539
475	Example: Try to create a event loop that uses epoll and nothing else.	540	Example: Try to create a event loop that uses epoll and nothing else.
476		541
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	542	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	543	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	544	fatal ("no epoll found here, maybe it hides under your chair");
480		545
481	=item ev_default_destroy ()	546	=item ev_default_destroy ()
482		547
483	Destroys the default loop again (frees all memory and kernel state	548	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	549	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	550	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	551	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	552	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	553	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	554	for example).
490		555
491	Note that certain global state, such as signal state, will not be freed by	556	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	557	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	558	as signal and child watchers) would need to be stopped manually.
494		559
495	In general it is not advisable to call this function except in the	560	In general it is not advisable to call this function except in the
496	rare occasion where you really need to free e.g. the signal handling	561	rare occasion where you really need to free e.g. the signal handling
497	pipe fds. If you need dynamically allocated loops it is better to use	562	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	563	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		588
524	=item ev_loop_fork (loop)	589	=item ev_loop_fork (loop)
525		590
526	Like C<ev_default_fork>, but acts on an event loop created by	591	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	592	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	593	after fork that you want to re-use in the child, and how you do this is
		594	entirely your own problem.
529		595
530	=item int ev_is_default_loop (loop)	596	=item int ev_is_default_loop (loop)
531		597
532	Returns true when the given loop actually is the default loop, false otherwise.	598	Returns true when the given loop is, in fact, the default loop, and false
		599	otherwise.
533		600
534	=item unsigned int ev_loop_count (loop)	601	=item unsigned int ev_loop_count (loop)
535		602
536	Returns the count of loop iterations for the loop, which is identical to	603	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	604	the number of times libev did poll for new events. It starts at C<0> and
…		…
552	received events and started processing them. This timestamp does not	619	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	620	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	621	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	622	event occurring (or more correctly, libev finding out about it).
556		623
		624	=item ev_now_update (loop)
		625
		626	Establishes the current time by querying the kernel, updating the time
		627	returned by C<ev_now ()> in the progress. This is a costly operation and
		628	is usually done automatically within C<ev_loop ()>.
		629
		630	This function is rarely useful, but when some event callback runs for a
		631	very long time without entering the event loop, updating libev's idea of
		632	the current time is a good idea.
		633
		634	See also "The special problem of time updates" in the C<ev_timer> section.
		635
557	=item ev_loop (loop, int flags)	636	=item ev_loop (loop, int flags)
558		637
559	Finally, this is it, the event handler. This function usually is called	638	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	639	after you initialised all your watchers and you want to start handling
561	events.	640	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	642	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	643	either no event watchers are active anymore or C<ev_unloop> was called.
565		644
566	Please note that an explicit C<ev_unloop> is usually better than	645	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	646	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	647	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	648	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	649	of relying on its watchers stopping correctly, that is truly a thing of
		650	beauty.
571		651
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	652	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	653	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	654	process in case there are no events and will return after one iteration of
		655	the loop.
575		656
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	657	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	658	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	659	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	660	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	661	user-registered callback will be called), and will return after one
		662	iteration of the loop.
		663
		664	This is useful if you are waiting for some external event in conjunction
		665	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	666	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	667	usually a better approach for this kind of thing.
583		668
584	Here are the gory details of what C<ev_loop> does:	669	Here are the gory details of what C<ev_loop> does:
585		670
586	- Before the first iteration, call any pending watchers.	671	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	672	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	673	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	674	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	675	- If we have been forked, detach and recreate the kernel state
		676	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	677	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	678	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	679	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	680	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	681	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	682	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	683	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	684	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	685	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	686	- Queue all expired timers.
601	- Queue all outstanding periodics.	687	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	688	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	689	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	690	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	691	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	692	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	693	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	698	anymore.
613		699
614	... queue jobs here, make sure they register event watchers as long	700	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	701	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	702	ev_loop (my_loop, 0);
617	... jobs done. yeah!	703	... jobs done or somebody called unloop. yeah!
618		704
619	=item ev_unloop (loop, how)	705	=item ev_unloop (loop, how)
620		706
621	Can be used to make a call to C<ev_loop> return early (but only after it	707	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	708	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	709	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	710	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		711
626	This "unloop state" will be cleared when entering C<ev_loop> again.	712	This "unloop state" will be cleared when entering C<ev_loop> again.
627		713
		714	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		715
628	=item ev_ref (loop)	716	=item ev_ref (loop)
629		717
630	=item ev_unref (loop)	718	=item ev_unref (loop)
631		719
632	Ref/unref can be used to add or remove a reference count on the event	720	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	721	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	722	count is nonzero, C<ev_loop> will not return on its own.
		723
635	a watcher you never unregister that should not keep C<ev_loop> from	724	If you have a watcher you never unregister that should not keep C<ev_loop>
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	725	from returning, call ev_unref() after starting, and ev_ref() before
		726	stopping it.
		727
637	example, libev itself uses this for its internal signal pipe: It is not	728	As an example, libev itself uses this for its internal signal pipe: It is
638	visible to the libev user and should not keep C<ev_loop> from exiting if	729	not visible to the libev user and should not keep C<ev_loop> from exiting
639	no event watchers registered by it are active. It is also an excellent	730	if no event watchers registered by it are active. It is also an excellent
640	way to do this for generic recurring timers or from within third-party	731	way to do this for generic recurring timers or from within third-party
641	libraries. Just remember to I<unref after start> and I<ref before stop>	732	libraries. Just remember to I<unref after start> and I<ref before stop>
642	(but only if the watcher wasn't active before, or was active before,	733	(but only if the watcher wasn't active before, or was active before,
643	respectively).	734	respectively).
644		735
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	736	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	737	running when nothing else is active.
647		738
648	struct ev_signal exitsig;	739	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	740	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	741	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	742	evf_unref (loop);
652		743
653	Example: For some weird reason, unregister the above signal handler again.	744	Example: For some weird reason, unregister the above signal handler again.
654		745
655	ev_ref (loop);	746	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	747	ev_signal_stop (loop, &exitsig);
657		748
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	749	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		750
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	751	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		752
662	These advanced functions influence the time that libev will spend waiting	753	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	754	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	755	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		756	latency.
665		757
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	758	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	759	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	760	to increase efficiency of loop iterations (or to increase power-saving
		761	opportunities).
669		762
670	The background is that sometimes your program runs just fast enough to	763	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	764	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	765	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	766	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	767	overhead for the actual polling but can deliver many events at once.
675		768
676	By setting a higher I<io collect interval> you allow libev to spend more	769	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	770	time collecting I/O events, so you can handle more events per iteration,
…		…
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	772	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	773	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		774
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	775	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	776	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	777	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	778	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	779	value will not introduce any overhead in libev.
687		780
688	Many (busy) programs can usually benefit by setting the io collect	781	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	782	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	783	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	784	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	785	as this approaches the timing granularity of most systems.
		786
		787	Setting the I<timeout collect interval> can improve the opportunity for
		788	saving power, as the program will "bundle" timer callback invocations that
		789	are "near" in time together, by delaying some, thus reducing the number of
		790	times the process sleeps and wakes up again. Another useful technique to
		791	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		792	they fire on, say, one-second boundaries only.
		793
		794	=item ev_loop_verify (loop)
		795
		796	This function only does something when C<EV_VERIFY> support has been
		797	compiled in, which is the default for non-minimal builds. It tries to go
		798	through all internal structures and checks them for validity. If anything
		799	is found to be inconsistent, it will print an error message to standard
		800	error and call C<abort ()>.
		801
		802	This can be used to catch bugs inside libev itself: under normal
		803	circumstances, this function will never abort as of course libev keeps its
		804	data structures consistent.
693		805
694	=back	806	=back
695		807
696		808
697	=head1 ANATOMY OF A WATCHER	809	=head1 ANATOMY OF A WATCHER
		810
		811	In the following description, uppercase C<TYPE> in names stands for the
		812	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		813	watchers and C<ev_io_start> for I/O watchers.
698		814
699	A watcher is a structure that you create and register to record your	815	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	816	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	817	become readable, you would create an C<ev_io> watcher for that:
702		818
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	819	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	820	{
705	ev_io_stop (w);	821	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	822	ev_unloop (loop, EVUNLOOP_ALL);
707	}	823	}
708		824
709	struct ev_loop *loop = ev_default_loop (0);	825	struct ev_loop *loop = ev_default_loop (0);
		826
710	struct ev_io stdin_watcher;	827	ev_io stdin_watcher;
		828
711	ev_init (&stdin_watcher, my_cb);	829	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	830	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	831	ev_io_start (loop, &stdin_watcher);
		832
714	ev_loop (loop, 0);	833	ev_loop (loop, 0);
715		834
716	As you can see, you are responsible for allocating the memory for your	835	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	836	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	837	stack).
		838
		839	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		840	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		841
720	Each watcher structure must be initialised by a call to C<ev_init	842	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	843	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	844	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	845	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	846	is readable and/or writable).
725		847
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	848	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	849	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	850	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	851	ev_TYPE_init (watcher *, callback, ...) >>.
730		852
731	To make the watcher actually watch out for events, you have to start it	853	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	854	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	855	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	856	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		857
736	As long as your watcher is active (has been started but not stopped) you	858	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	859	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	860	reinitialise it or call its C<ev_TYPE_set> macro.
739		861
740	Each and every callback receives the event loop pointer as first, the	862	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	863	registered watcher structure as second, and a bitset of received events as
742	third argument.	864	third argument.
743		865
…		…
803		925
804	The given async watcher has been asynchronously notified (see C<ev_async>).	926	The given async watcher has been asynchronously notified (see C<ev_async>).
805		927
806	=item C<EV_ERROR>	928	=item C<EV_ERROR>
807		929
808	An unspecified error has occured, the watcher has been stopped. This might	930	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	931	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	932	ran out of memory, a file descriptor was found to be closed or any other
		933	problem. Libev considers these application bugs.
		934
811	problem. You best act on it by reporting the problem and somehow coping	935	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	936	watcher being stopped. Note that well-written programs should not receive
		937	an error ever, so when your watcher receives it, this usually indicates a
		938	bug in your program.
813		939
814	Libev will usually signal a few "dummy" events together with an error,	940	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	941	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	942	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	943	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	944	programs, though, as the fd could already be closed and reused for another
		945	thing, so beware.
819		946
820	=back	947	=back
821		948
822	=head2 GENERIC WATCHER FUNCTIONS	949	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		950
827	=over 4	951	=over 4
828		952
829	=item C<ev_init> (ev_TYPE *watcher, callback)	953	=item C<ev_init> (ev_TYPE *watcher, callback)
830		954
…		…
836	which rolls both calls into one.	960	which rolls both calls into one.
837		961
838	You can reinitialise a watcher at any time as long as it has been stopped	962	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	963	(or never started) and there are no pending events outstanding.
840		964
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	965	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	966	int revents)>.
		967
		968	Example: Initialise an C<ev_io> watcher in two steps.
		969
		970	ev_io w;
		971	ev_init (&w, my_cb);
		972	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		973
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	974	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		975
846	This macro initialises the type-specific parts of a watcher. You need to	976	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	977	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	980	difference to the C<ev_init> macro).
851		981
852	Although some watcher types do not have type-specific arguments	982	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	983	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		984
		985	See C<ev_init>, above, for an example.
		986
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	987	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		988
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	989	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	990	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	991	a watcher. The same limitations apply, of course.
		992
		993	Example: Initialise and set an C<ev_io> watcher in one step.
		994
		995	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		996
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	997	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		998
863	Starts (activates) the given watcher. Only active watchers will receive	999	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1000	events. If the watcher is already active nothing will happen.
865		1001
		1002	Example: Start the C<ev_io> watcher that is being abused as example in this
		1003	whole section.
		1004
		1005	ev_io_start (EV_DEFAULT_UC, &w);
		1006
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1007	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		1008
868	Stops the given watcher again (if active) and clears the pending	1009	Stops the given watcher if active, and clears the pending status (whether
		1010	the watcher was active or not).
		1011
869	status. It is possible that stopped watchers are pending (for example,	1012	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1013	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1014	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	1015	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	1016	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1017
875	=item bool ev_is_active (ev_TYPE *watcher)	1018	=item bool ev_is_active (ev_TYPE *watcher)
876		1019
877	Returns a true value iff the watcher is active (i.e. it has been started	1020	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1021	and not yet been stopped). As long as a watcher is active you must not modify
…		…
920	The default priority used by watchers when no priority has been set is	1063	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1064	always C<0>, which is supposed to not be too high and not be too low :).
922		1065
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1066	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
924	fine, as long as you do not mind that the priority value you query might	1067	fine, as long as you do not mind that the priority value you query might
925	or might not have been adjusted to be within valid range.	1068	or might not have been clamped to the valid range.
926		1069
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1070	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1071
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1072	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1073	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1074	can deal with that fact, as both are simply passed through to the
		1075	callback.
932		1076
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1077	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1078
935	If the watcher is pending, this function returns clears its pending status	1079	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1080	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1081	watcher isn't pending it does nothing and returns C<0>.
938		1082
		1083	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1084	callback to be invoked, which can be accomplished with this function.
		1085
939	=back	1086	=back
940		1087
941		1088
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1089	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1090
944	Each watcher has, by default, a member C<void *data> that you can change	1091	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1092	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1093	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1094	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1095	member, you can also "subclass" the watcher type and provide your own
949	data:	1096	data:
950		1097
951	struct my_io	1098	struct my_io
952	{	1099	{
953	struct ev_io io;	1100	ev_io io;
954	int otherfd;	1101	int otherfd;
955	void *somedata;	1102	void *somedata;
956	struct whatever *mostinteresting;	1103	struct whatever *mostinteresting;
957	}	1104	};
		1105
		1106	...
		1107	struct my_io w;
		1108	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1109
959	And since your callback will be called with a pointer to the watcher, you	1110	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1111	can cast it back to your own type:
961		1112
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1113	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1114	{
964	struct my_io *w = (struct my_io *)w_;	1115	struct my_io *w = (struct my_io *)w_;
965	...	1116	...
966	}	1117	}
967		1118
968	More interesting and less C-conformant ways of casting your callback type	1119	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1120	instead have been omitted.
970		1121
971	Another common scenario is having some data structure with multiple	1122	Another common scenario is to use some data structure with multiple
972	watchers:	1123	embedded watchers:
973		1124
974	struct my_biggy	1125	struct my_biggy
975	{	1126	{
976	int some_data;	1127	int some_data;
977	ev_timer t1;	1128	ev_timer t1;
978	ev_timer t2;	1129	ev_timer t2;
979	}	1130	}
980		1131
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1132	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1133	complicated: Either you store the address of your C<my_biggy> struct
		1134	in the C<data> member of the watcher (for woozies), or you need to use
		1135	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1136	programmers):
983		1137
984	#include <stddef.h>	1138	#include <stddef.h>
985		1139
986	static void	1140	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1141	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1142	{
989	struct my_biggy big = (struct my_biggy *	1143	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1144	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1145	}
992		1146
993	static void	1147	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1148	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1149	{
996	struct my_biggy big = (struct my_biggy *	1150	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1151	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1152	}
999		1153
1000		1154
1001	=head1 WATCHER TYPES	1155	=head1 WATCHER TYPES
1002		1156
1003	This section describes each watcher in detail, but will not repeat	1157	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1181	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1182	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1183	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1184	required if you know what you are doing).
1031		1185
1032	If you must do this, then force the use of a known-to-be-good backend	1186	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1187	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1188	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1189
1036	Another thing you have to watch out for is that it is quite easy to	1190	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1191	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1192	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1193	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1194	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1195	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1196	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1197	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1198
1045	If you cannot run the fd in non-blocking mode (for example you should not	1199	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1200	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1201	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1202	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1203	does this on its own, so its quite safe to use). Some people additionally
		1204	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1205	indefinitely.
		1206
		1207	But really, best use non-blocking mode.
1050		1208
1051	=head3 The special problem of disappearing file descriptors	1209	=head3 The special problem of disappearing file descriptors
1052		1210
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1211	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1212	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1213	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1214	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1215	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1216	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1217	fact, a different file descriptor.
1060		1218
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1249	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1250	C<EVBACKEND_POLL>.
1093		1251
1094	=head3 The special problem of SIGPIPE	1252	=head3 The special problem of SIGPIPE
1095		1253
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1254	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1255	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1256	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1257	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1258
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1259	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1260	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1261	somewhere, as that would have given you a big clue).
1105		1262
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1268	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1269
1113	=item ev_io_set (ev_io *, int fd, int events)	1270	=item ev_io_set (ev_io *, int fd, int events)
1114		1271
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1272	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1273	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1274	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1275
1119	=item int fd [read-only]	1276	=item int fd [read-only]
1120		1277
1121	The file descriptor being watched.	1278	The file descriptor being watched.
1122		1279
…		…
1130		1287
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1288	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1289	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1290	attempt to read a whole line in the callback.
1134		1291
1135	static void	1292	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1293	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1294	{
1138	ev_io_stop (loop, w);	1295	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1296	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1297	}
1141		1298
1142	...	1299	...
1143	struct ev_loop *loop = ev_default_init (0);	1300	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1301	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1302	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1303	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1304	ev_loop (loop, 0);
1148		1305
1149		1306
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1307	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1308
1152	Timer watchers are simple relative timers that generate an event after a	1309	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1310	given time, and optionally repeating in regular intervals after that.
1154		1311
1155	The timers are based on real time, that is, if you register an event that	1312	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1313	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1314	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1315	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1316	monotonic clock option helps a lot here).
		1317
		1318	The callback is guaranteed to be invoked only I<after> its timeout has
		1319	passed, but if multiple timers become ready during the same loop iteration
		1320	then order of execution is undefined.
		1321
		1322	=head3 Be smart about timeouts
		1323
		1324	Many real-world problems involve some kind of timeout, usually for error
		1325	recovery. A typical example is an HTTP request - if the other side hangs,
		1326	you want to raise some error after a while.
		1327
		1328	What follows are some ways to handle this problem, from obvious and
		1329	inefficient to smart and efficient.
		1330
		1331	In the following, a 60 second activity timeout is assumed - a timeout that
		1332	gets reset to 60 seconds each time there is activity (e.g. each time some
		1333	data or other life sign was received).
		1334
		1335	=over 4
		1336
		1337	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1338
		1339	This is the most obvious, but not the most simple way: In the beginning,
		1340	start the watcher:
		1341
		1342	ev_timer_init (timer, callback, 60., 0.);
		1343	ev_timer_start (loop, timer);
		1344
		1345	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1346	and start it again:
		1347
		1348	ev_timer_stop (loop, timer);
		1349	ev_timer_set (timer, 60., 0.);
		1350	ev_timer_start (loop, timer);
		1351
		1352	This is relatively simple to implement, but means that each time there is
		1353	some activity, libev will first have to remove the timer from its internal
		1354	data structure and then add it again. Libev tries to be fast, but it's
		1355	still not a constant-time operation.
		1356
		1357	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1358
		1359	This is the easiest way, and involves using C<ev_timer_again> instead of
		1360	C<ev_timer_start>.
		1361
		1362	To implement this, configure an C<ev_timer> with a C<repeat> value
		1363	of C<60> and then call C<ev_timer_again> at start and each time you
		1364	successfully read or write some data. If you go into an idle state where
		1365	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1366	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1367
		1368	That means you can ignore both the C<ev_timer_start> function and the
		1369	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1370	member and C<ev_timer_again>.
		1371
		1372	At start:
		1373
		1374	ev_timer_init (timer, callback);
		1375	timer->repeat = 60.;
		1376	ev_timer_again (loop, timer);
		1377
		1378	Each time there is some activity:
		1379
		1380	ev_timer_again (loop, timer);
		1381
		1382	It is even possible to change the time-out on the fly, regardless of
		1383	whether the watcher is active or not:
		1384
		1385	timer->repeat = 30.;
		1386	ev_timer_again (loop, timer);
		1387
		1388	This is slightly more efficient then stopping/starting the timer each time
		1389	you want to modify its timeout value, as libev does not have to completely
		1390	remove and re-insert the timer from/into its internal data structure.
		1391
		1392	It is, however, even simpler than the "obvious" way to do it.
		1393
		1394	=item 3. Let the timer time out, but then re-arm it as required.
		1395
		1396	This method is more tricky, but usually most efficient: Most timeouts are
		1397	relatively long compared to the intervals between other activity - in
		1398	our example, within 60 seconds, there are usually many I/O events with
		1399	associated activity resets.
		1400
		1401	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1402	but remember the time of last activity, and check for a real timeout only
		1403	within the callback:
		1404
		1405	ev_tstamp last_activity; // time of last activity
		1406
		1407	static void
		1408	callback (EV_P_ ev_timer *w, int revents)
		1409	{
		1410	ev_tstamp now = ev_now (EV_A);
		1411	ev_tstamp timeout = last_activity + 60.;
		1412
		1413	// if last_activity + 60. is older than now, we did time out
		1414	if (timeout < now)
		1415	{
		1416	// timeout occured, take action
		1417	}
		1418	else
		1419	{
		1420	// callback was invoked, but there was some activity, re-arm
		1421	// the watcher to fire in last_activity + 60, which is
		1422	// guaranteed to be in the future, so "again" is positive:
		1423	w->again = timeout - now;
		1424	ev_timer_again (EV_A_ w);
		1425	}
		1426	}
		1427
		1428	To summarise the callback: first calculate the real timeout (defined
		1429	as "60 seconds after the last activity"), then check if that time has
		1430	been reached, which means something I<did>, in fact, time out. Otherwise
		1431	the callback was invoked too early (C<timeout> is in the future), so
		1432	re-schedule the timer to fire at that future time, to see if maybe we have
		1433	a timeout then.
		1434
		1435	Note how C<ev_timer_again> is used, taking advantage of the
		1436	C<ev_timer_again> optimisation when the timer is already running.
		1437
		1438	This scheme causes more callback invocations (about one every 60 seconds
		1439	minus half the average time between activity), but virtually no calls to
		1440	libev to change the timeout.
		1441
		1442	To start the timer, simply initialise the watcher and set C<last_activity>
		1443	to the current time (meaning we just have some activity :), then call the
		1444	callback, which will "do the right thing" and start the timer:
		1445
		1446	ev_timer_init (timer, callback);
		1447	last_activity = ev_now (loop);
		1448	callback (loop, timer, EV_TIMEOUT);
		1449
		1450	And when there is some activity, simply store the current time in
		1451	C<last_activity>, no libev calls at all:
		1452
		1453	last_actiivty = ev_now (loop);
		1454
		1455	This technique is slightly more complex, but in most cases where the
		1456	time-out is unlikely to be triggered, much more efficient.
		1457
		1458	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1459	callback :) - just change the timeout and invoke the callback, which will
		1460	fix things for you.
		1461
		1462	=item 4. Wee, just use a double-linked list for your timeouts.
		1463
		1464	If there is not one request, but many thousands (millions...), all
		1465	employing some kind of timeout with the same timeout value, then one can
		1466	do even better:
		1467
		1468	When starting the timeout, calculate the timeout value and put the timeout
		1469	at the I<end> of the list.
		1470
		1471	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1472	the list is expected to fire (for example, using the technique #3).
		1473
		1474	When there is some activity, remove the timer from the list, recalculate
		1475	the timeout, append it to the end of the list again, and make sure to
		1476	update the C<ev_timer> if it was taken from the beginning of the list.
		1477
		1478	This way, one can manage an unlimited number of timeouts in O(1) time for
		1479	starting, stopping and updating the timers, at the expense of a major
		1480	complication, and having to use a constant timeout. The constant timeout
		1481	ensures that the list stays sorted.
		1482
		1483	=back
		1484
		1485	So which method the best?
		1486
		1487	Method #2 is a simple no-brain-required solution that is adequate in most
		1488	situations. Method #3 requires a bit more thinking, but handles many cases
		1489	better, and isn't very complicated either. In most case, choosing either
		1490	one is fine, with #3 being better in typical situations.
		1491
		1492	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1493	rather complicated, but extremely efficient, something that really pays
		1494	off after the first million or so of active timers, i.e. it's usually
		1495	overkill :)
		1496
		1497	=head3 The special problem of time updates
		1498
		1499	Establishing the current time is a costly operation (it usually takes at
		1500	least two system calls): EV therefore updates its idea of the current
		1501	time only before and after C<ev_loop> collects new events, which causes a
		1502	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1503	lots of events in one iteration.
1160		1504
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1505	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1506	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1507	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1508	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1509	timeout on the current time, use something like this to adjust for this:
1166		1510
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1511	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1512
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1513	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1514	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1515	()>.
1172		1516
1173	=head3 Watcher-Specific Functions and Data Members	1517	=head3 Watcher-Specific Functions and Data Members
1174		1518
1175	=over 4	1519	=over 4
1176		1520
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1521	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1522
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1523	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1524
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1525	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1526	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1527	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1528	configured to trigger again C<repeat> seconds later, again, and again,
		1529	until stopped manually.
1185		1530
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1531	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1532	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1533	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1534	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1535	do stuff) the timer will not fire more than once per event loop iteration.
1191		1536
1192	=item ev_timer_again (loop, ev_timer *)	1537	=item ev_timer_again (loop, ev_timer *)
1193		1538
1194	This will act as if the timer timed out and restart it again if it is	1539	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1540	repeating. The exact semantics are:
1196		1541
1197	If the timer is pending, its pending status is cleared.	1542	If the timer is pending, its pending status is cleared.
1198		1543
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1544	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1545
1201	If the timer is repeating, either start it if necessary (with the	1546	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	1547	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1548
1204	This sounds a bit complicated, but here is a useful and typical	1549	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1205	example: Imagine you have a tcp connection and you want a so-called idle	1550	usage example.
1206	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the
1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1212	automatically restart it if need be.
1213
1214	That means you can ignore the C<after> value and C<ev_timer_start>
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216
1217	ev_timer_init (timer, callback, 0., 5.);
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 17.;
1221	ev_timer_again (loop, timer);
1222	...
1223	timer->again = 10.;
1224	ev_timer_again (loop, timer);
1225
1226	This is more slightly efficient then stopping/starting the timer each time
1227	you want to modify its timeout value.
1228		1551
1229	=item ev_tstamp repeat [read-write]	1552	=item ev_tstamp repeat [read-write]
1230		1553
1231	The current C<repeat> value. Will be used each time the watcher times out	1554	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	1555	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	1556	which is also when any modifications are taken into account.
1234		1557
1235	=back	1558	=back
1236		1559
1237	=head3 Examples	1560	=head3 Examples
1238		1561
1239	Example: Create a timer that fires after 60 seconds.	1562	Example: Create a timer that fires after 60 seconds.
1240		1563
1241	static void	1564	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1565	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	1566	{
1244	.. one minute over, w is actually stopped right here	1567	.. one minute over, w is actually stopped right here
1245	}	1568	}
1246		1569
1247	struct ev_timer mytimer;	1570	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1571	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1572	ev_timer_start (loop, &mytimer);
1250		1573
1251	Example: Create a timeout timer that times out after 10 seconds of	1574	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1575	inactivity.
1253		1576
1254	static void	1577	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1578	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	1579	{
1257	.. ten seconds without any activity	1580	.. ten seconds without any activity
1258	}	1581	}
1259		1582
1260	struct ev_timer mytimer;	1583	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1584	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1585	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1586	ev_loop (loop, 0);
1264		1587
1265	// and in some piece of code that gets executed on any "activity":	1588	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1589	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1590	ev_timer_again (&mytimer);
1268		1591
1269		1592
1270	=head2 C<ev_periodic> - to cron or not to cron?	1593	=head2 C<ev_periodic> - to cron or not to cron?
1271		1594
1272	Periodic watchers are also timers of a kind, but they are very versatile	1595	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1596	(and unfortunately a bit complex).
1274		1597
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1598	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1599	but on wall clock time (absolute time). You can tell a periodic watcher
1277	to trigger "at" some specific point in time. For example, if you tell a	1600	to trigger after some specific point in time. For example, if you tell a
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1601	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1279	+ 10.>) and then reset your system clock to the last year, then it will	1602	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1603	clock to January of the previous year, then it will take more than year
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1604	to trigger the event (unlike an C<ev_timer>, which would still trigger
1281	roughly 10 seconds later).	1605	roughly 10 seconds later as it uses a relative timeout).
1282		1606
1283	They can also be used to implement vastly more complex timers, such as	1607	C<ev_periodic>s can also be used to implement vastly more complex timers,
1284	triggering an event on each midnight, local time or other, complicated,	1608	such as triggering an event on each "midnight, local time", or other
1285	rules.	1609	complicated rules.
1286		1610
1287	As with timers, the callback is guarenteed to be invoked only when the	1611	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1612	time (C<at>) has passed, but if multiple periodic timers become ready
1289	during the same loop iteration then order of execution is undefined.	1613	during the same loop iteration, then order of execution is undefined.
1290		1614
1291	=head3 Watcher-Specific Functions and Data Members	1615	=head3 Watcher-Specific Functions and Data Members
1292		1616
1293	=over 4	1617	=over 4
1294		1618
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1619	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1296		1620
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1621	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1298		1622
1299	Lots of arguments, lets sort it out... There are basically three modes of	1623	Lots of arguments, lets sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1624	operation, and we will explain them from simplest to most complex:
1301		1625
1302	=over 4	1626	=over 4
1303		1627
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1628	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305		1629
1306	In this configuration the watcher triggers an event at the wallclock time	1630	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1631	time C<at> has passed. It will not repeat and will not adjust when a time
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1632	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1309	system time reaches or surpasses this time.	1633	only run when the system clock reaches or surpasses this time.
1310		1634
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1635	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312		1636
1313	In this mode the watcher will always be scheduled to time out at the next	1637	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1638	C<at + N * interval> time (for some integer N, which can also be negative)
1315	and then repeat, regardless of any time jumps.	1639	and then repeat, regardless of any time jumps.
1316		1640
1317	This can be used to create timers that do not drift with respect to system	1641	This can be used to create timers that do not drift with respect to the
1318	time:	1642	system clock, for example, here is a C<ev_periodic> that triggers each
		1643	hour, on the hour:
1319		1644
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1645	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1646
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1647	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1648	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	1649	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1650	by 3600.
1326		1651
1327	Another way to think about it (for the mathematically inclined) is that	1652	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1653	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1654	time where C<time = at (mod interval)>, regardless of any time jumps.
1330		1655
1331	For numerical stability it is preferable that the C<at> value is near	1656	For numerical stability it is preferable that the C<at> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1657	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1658	this value, and in fact is often specified as zero.
		1659
		1660	Note also that there is an upper limit to how often a timer can fire (CPU
		1661	speed for example), so if C<interval> is very small then timing stability
		1662	will of course deteriorate. Libev itself tries to be exact to be about one
		1663	millisecond (if the OS supports it and the machine is fast enough).
1334		1664
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1665	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336		1666
1337	In this mode the values for C<interval> and C<at> are both being	1667	In this mode the values for C<interval> and C<at> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1668	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1669	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1670	current time as second argument.
1341		1671
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1672	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1343	ever, or make any event loop modifications>. If you need to stop it,	1673	ever, or make ANY event loop modifications whatsoever>.
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1674
		1675	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1676	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1677	only event loop modification you are allowed to do).
		1678
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1679	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1680	*w, ev_tstamp now)>, e.g.:
1349		1681
		1682	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1683	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1684	{
1352	return now + 60.;	1685	return now + 60.;
1353	}	1686	}
1354		1687
1355	It must return the next time to trigger, based on the passed time value	1688	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	1689	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	1690	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1691	might be called at other times, too.
1359		1692
1360	NOTE: I<< This callback must always return a time that is later than the	1693	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1694	equal to the passed C<now> value >>.
1362		1695
1363	This can be used to create very complex timers, such as a timer that	1696	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	1697	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	1698	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	1699	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	1700	reason I omitted it as an example).
1368		1701
1369	=back	1702	=back
…		…
1392		1725
1393	The current interval value. Can be modified any time, but changes only	1726	The current interval value. Can be modified any time, but changes only
1394	take effect when the periodic timer fires or C<ev_periodic_again> is being	1727	take effect when the periodic timer fires or C<ev_periodic_again> is being
1395	called.	1728	called.
1396		1729
1397	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1730	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1398		1731
1399	The current reschedule callback, or C<0>, if this functionality is	1732	The current reschedule callback, or C<0>, if this functionality is
1400	switched off. Can be changed any time, but changes only take effect when	1733	switched off. Can be changed any time, but changes only take effect when
1401	the periodic timer fires or C<ev_periodic_again> is being called.	1734	the periodic timer fires or C<ev_periodic_again> is being called.
1402		1735
1403	=back	1736	=back
1404		1737
1405	=head3 Examples	1738	=head3 Examples
1406		1739
1407	Example: Call a callback every hour, or, more precisely, whenever the	1740	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1741	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1742	potentially a lot of jitter, but good long-term stability.
1410		1743
1411	static void	1744	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1745	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1413	{	1746	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1747	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1748	}
1416		1749
1417	struct ev_periodic hourly_tick;	1750	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1751	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1752	ev_periodic_start (loop, &hourly_tick);
1420		1753
1421	Example: The same as above, but use a reschedule callback to do it:	1754	Example: The same as above, but use a reschedule callback to do it:
1422		1755
1423	#include <math.h>	1756	#include <math.h>
1424		1757
1425	static ev_tstamp	1758	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1759	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	1760	{
1428	return fmod (now, 3600.) + 3600.;	1761	return now + (3600. - fmod (now, 3600.));
1429	}	1762	}
1430		1763
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1764	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1765
1433	Example: Call a callback every hour, starting now:	1766	Example: Call a callback every hour, starting now:
1434		1767
1435	struct ev_periodic hourly_tick;	1768	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1769	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1770	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1771	ev_periodic_start (loop, &hourly_tick);
1439		1772
1440		1773
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1774	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1775
1443	Signal watchers will trigger an event when the process receives a specific	1776	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	1777	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	1778	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1779	normal event processing, like any other event.
1447		1780
		1781	If you want signals asynchronously, just use C<sigaction> as you would
		1782	do without libev and forget about sharing the signal. You can even use
		1783	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1784
1448	You can configure as many watchers as you like per signal. Only when the	1785	You can configure as many watchers as you like per signal. Only when the
1449	first watcher gets started will libev actually register a signal watcher	1786	first watcher gets started will libev actually register a signal handler
1450	with the kernel (thus it coexists with your own signal handlers as long	1787	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	1788	you don't register any with libev for the same signal). Similarly, when
1452	watcher for a signal is stopped libev will reset the signal handler to	1789	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1790	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1791
1455	If possible and supported, libev will install its handlers with	1792	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1793	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1794	interrupted. If you have a problem with system calls getting interrupted by
1458	signals you can block all signals in an C<ev_check> watcher and unblock	1795	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1796	them in an C<ev_prepare> watcher.
1460		1797
1461	=head3 Watcher-Specific Functions and Data Members	1798	=head3 Watcher-Specific Functions and Data Members
1462		1799
…		…
1475		1812
1476	=back	1813	=back
1477		1814
1478	=head3 Examples	1815	=head3 Examples
1479		1816
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	1817	Example: Try to exit cleanly on SIGINT.
1481		1818
1482	static void	1819	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1820	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	1821	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	1822	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	1823	}
1487		1824
1488	struct ev_signal signal_watcher;	1825	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1826	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	1827	ev_signal_start (loop, &signal_watcher);
1491		1828
1492		1829
1493	=head2 C<ev_child> - watch out for process status changes	1830	=head2 C<ev_child> - watch out for process status changes
1494		1831
1495	Child watchers trigger when your process receives a SIGCHLD in response to	1832	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	1833	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	1834	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	1835	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	1836	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1837	forking and then immediately registering a watcher for the child is fine,
		1838	but forking and registering a watcher a few event loop iterations later is
		1839	not.
1500		1840
1501	Only the default event loop is capable of handling signals, and therefore	1841	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	1842	you can only register child watchers in the default event loop.
1503		1843
1504	=head3 Process Interaction	1844	=head3 Process Interaction
1505		1845
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	1846	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	1847	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	1848	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1849	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	1850	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	1851	children, even ones not watched.
1512		1852
1513	=head3 Overriding the Built-In Processing	1853	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	1857	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	1858	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	1859	default loop never gets destroyed. You are encouraged, however, to use an
1520	event-based approach to child reaping and thus use libev's support for	1860	event-based approach to child reaping and thus use libev's support for
1521	that, so other libev users can use C<ev_child> watchers freely.	1861	that, so other libev users can use C<ev_child> watchers freely.
		1862
		1863	=head3 Stopping the Child Watcher
		1864
		1865	Currently, the child watcher never gets stopped, even when the
		1866	child terminates, so normally one needs to stop the watcher in the
		1867	callback. Future versions of libev might stop the watcher automatically
		1868	when a child exit is detected.
1522		1869
1523	=head3 Watcher-Specific Functions and Data Members	1870	=head3 Watcher-Specific Functions and Data Members
1524		1871
1525	=over 4	1872	=over 4
1526		1873
…		…
1555	=head3 Examples	1902	=head3 Examples
1556		1903
1557	Example: C<fork()> a new process and install a child handler to wait for	1904	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	1905	its completion.
1559		1906
1560	ev_child cw;	1907	ev_child cw;
1561		1908
1562	static void	1909	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	1910	child_cb (EV_P_ ev_child *w, int revents)
1564	{	1911	{
1565	ev_child_stop (EV_A_ w);	1912	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1913	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	1914	}
1568		1915
1569	pid_t pid = fork ();	1916	pid_t pid = fork ();
1570		1917
1571	if (pid < 0)	1918	if (pid < 0)
1572	// error	1919	// error
1573	else if (pid == 0)	1920	else if (pid == 0)
1574	{	1921	{
1575	// the forked child executes here	1922	// the forked child executes here
1576	exit (1);	1923	exit (1);
1577	}	1924	}
1578	else	1925	else
1579	{	1926	{
1580	ev_child_init (&cw, child_cb, pid, 0);	1927	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	1928	ev_child_start (EV_DEFAULT_ &cw);
1582	}	1929	}
1583		1930
1584		1931
1585	=head2 C<ev_stat> - did the file attributes just change?	1932	=head2 C<ev_stat> - did the file attributes just change?
1586		1933
1587	This watches a filesystem path for attribute changes. That is, it calls	1934	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	1935	C<stat> on that path in regular intervals (or when the OS says it changed)
1589	compared to the last time, invoking the callback if it did.	1936	and sees if it changed compared to the last time, invoking the callback if
		1937	it did.
1590		1938
1591	The path does not need to exist: changing from "path exists" to "path does	1939	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	1940	not exist" is a status change like any other. The condition "path does not
1593	not exist" is signified by the C<st_nlink> field being zero (which is	1941	exist" (or more correctly "path cannot be stat'ed") is signified by the
1594	otherwise always forced to be at least one) and all the other fields of	1942	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	1943	least one) and all the other fields of the stat buffer having unspecified
		1944	contents.
1596		1945
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	1946	The path I<must not> end in a slash or contain special components such as
		1947	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1598	relative and your working directory changes, the behaviour is undefined.	1948	your working directory changes, then the behaviour is undefined.
1599		1949
1600	Since there is no standard to do this, the portable implementation simply	1950	Since there is no portable change notification interface available, the
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1951	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	1952	to see if it changed somehow. You can specify a recommended polling
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	1953	interval for this case. If you specify a polling interval of C<0> (highly
1604	unspecified default> value will be used (which you can expect to be around	1954	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	1955	(which you can expect to be around five seconds, although this might
1606	impose a minimum interval which is currently around C<0.1>, but thats	1956	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	1957	currently around C<0.1>, but that's usually overkill.
1608		1958
1609	This watcher type is not meant for massive numbers of stat watchers,	1959	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	1960	as even with OS-supported change notifications, this can be
1611	resource-intensive.	1961	resource-intensive.
1612		1962
1613	At the time of this writing, only the Linux inotify interface is	1963	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	1964	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader, note, however, that the author sees no way of implementing ev_stat	1965	exercise for the reader. Note, however, that the author sees no way of
1616	semantics with kqueue). Inotify will be used to give hints only and should	1966	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	not change the semantics of C<ev_stat> watchers, which means that libev
1618	sometimes needs to fall back to regular polling again even with inotify,
1619	but changes are usually detected immediately, and if the file exists there
1620	will be no polling.
1621		1967
1622	=head3 ABI Issues (Largefile Support)	1968	=head3 ABI Issues (Largefile Support)
1623		1969
1624	Libev by default (unless the user overrides this) uses the default	1970	Libev by default (unless the user overrides this) uses the default
1625	compilation environment, which means that on systems with optionally	1971	compilation environment, which means that on systems with large file
1626	disabled large file support, you get the 32 bit version of the stat	1972	support disabled by default, you get the 32 bit version of the stat
1627	structure. When using the library from programs that change the ABI to	1973	structure. When using the library from programs that change the ABI to
1628	use 64 bit file offsets the programs will fail. In that case you have to	1974	use 64 bit file offsets the programs will fail. In that case you have to
1629	compile libev with the same flags to get binary compatibility. This is	1975	compile libev with the same flags to get binary compatibility. This is
1630	obviously the case with any flags that change the ABI, but the problem is	1976	obviously the case with any flags that change the ABI, but the problem is
1631	most noticably with ev_stat and largefile support.	1977	most noticeably displayed with ev_stat and large file support.
1632		1978
1633	=head3 Inotify	1979	The solution for this is to lobby your distribution maker to make large
		1980	file interfaces available by default (as e.g. FreeBSD does) and not
		1981	optional. Libev cannot simply switch on large file support because it has
		1982	to exchange stat structures with application programs compiled using the
		1983	default compilation environment.
1634		1984
		1985	=head3 Inotify and Kqueue
		1986
1635	When C<inotify (7)> support has been compiled into libev (generally only	1987	When C<inotify (7)> support has been compiled into libev and present at
1636	available on Linux) and present at runtime, it will be used to speed up	1988	runtime, it will be used to speed up change detection where possible. The
1637	change detection where possible. The inotify descriptor will be created lazily	1989	inotify descriptor will be created lazily when the first C<ev_stat>
1638	when the first C<ev_stat> watcher is being started.	1990	watcher is being started.
1639		1991
1640	Inotify presence does not change the semantics of C<ev_stat> watchers	1992	Inotify presence does not change the semantics of C<ev_stat> watchers
1641	except that changes might be detected earlier, and in some cases, to avoid	1993	except that changes might be detected earlier, and in some cases, to avoid
1642	making regular C<stat> calls. Even in the presence of inotify support	1994	making regular C<stat> calls. Even in the presence of inotify support
1643	there are many cases where libev has to resort to regular C<stat> polling.	1995	there are many cases where libev has to resort to regular C<stat> polling,
		1996	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1997	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1998	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1999	xfs are fully working) libev usually gets away without polling.
1644		2000
1645	(There is no support for kqueue, as apparently it cannot be used to	2001	There is no support for kqueue, as apparently it cannot be used to
1646	implement this functionality, due to the requirement of having a file	2002	implement this functionality, due to the requirement of having a file
1647	descriptor open on the object at all times).	2003	descriptor open on the object at all times, and detecting renames, unlinks
		2004	etc. is difficult.
		2005
		2006	=head3 C<stat ()> is a synchronous operation
		2007
		2008	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2009	the process. The exception are C<ev_stat> watchers - those call C<stat
		2010	()>, which is a synchronous operation.
		2011
		2012	For local paths, this usually doesn't matter: unless the system is very
		2013	busy or the intervals between stat's are large, a stat call will be fast,
		2014	as the path data is suually in memory already (except when starting the
		2015	watcher).
		2016
		2017	For networked file systems, calling C<stat ()> can block an indefinite
		2018	time due to network issues, and even under good conditions, a stat call
		2019	often takes multiple milliseconds.
		2020
		2021	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2022	paths, although this is fully supported by libev.
1648		2023
1649	=head3 The special problem of stat time resolution	2024	=head3 The special problem of stat time resolution
1650		2025
1651	The C<stat ()> syscall only supports full-second resolution portably, and	2026	The C<stat ()> system call only supports full-second resolution portably,
1652	even on systems where the resolution is higher, many filesystems still	2027	and even on systems where the resolution is higher, most file systems
1653	only support whole seconds.	2028	still only support whole seconds.
1654		2029
1655	That means that, if the time is the only thing that changes, you can	2030	That means that, if the time is the only thing that changes, you can
1656	easily miss updates: on the first update, C<ev_stat> detects a change and	2031	easily miss updates: on the first update, C<ev_stat> detects a change and
1657	calls your callback, which does something. When there is another update	2032	calls your callback, which does something. When there is another update
1658	within the same second, C<ev_stat> will be unable to detect it as the stat	2033	within the same second, C<ev_stat> will be unable to detect unless the
1659	data does not change.	2034	stat data does change in other ways (e.g. file size).
1660		2035
1661	The solution to this is to delay acting on a change for slightly more	2036	The solution to this is to delay acting on a change for slightly more
1662	than second (or till slightly after the next full second boundary), using	2037	than a second (or till slightly after the next full second boundary), using
1663	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2038	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664	ev_timer_again (loop, w)>).	2039	ev_timer_again (loop, w)>).
1665		2040
1666	The C<.02> offset is added to work around small timing inconsistencies	2041	The C<.02> offset is added to work around small timing inconsistencies
1667	of some operating systems (where the second counter of the current time	2042	of some operating systems (where the second counter of the current time
…		…
1684	C<path>. The C<interval> is a hint on how quickly a change is expected to	2059	C<path>. The C<interval> is a hint on how quickly a change is expected to
1685	be detected and should normally be specified as C<0> to let libev choose	2060	be detected and should normally be specified as C<0> to let libev choose
1686	a suitable value. The memory pointed to by C<path> must point to the same	2061	a suitable value. The memory pointed to by C<path> must point to the same
1687	path for as long as the watcher is active.	2062	path for as long as the watcher is active.
1688		2063
1689	The callback will receive C<EV_STAT> when a change was detected, relative	2064	The callback will receive an C<EV_STAT> event when a change was detected,
1690	to the attributes at the time the watcher was started (or the last change	2065	relative to the attributes at the time the watcher was started (or the
1691	was detected).	2066	last change was detected).
1692		2067
1693	=item ev_stat_stat (loop, ev_stat *)	2068	=item ev_stat_stat (loop, ev_stat *)
1694		2069
1695	Updates the stat buffer immediately with new values. If you change the	2070	Updates the stat buffer immediately with new values. If you change the
1696	watched path in your callback, you could call this function to avoid	2071	watched path in your callback, you could call this function to avoid
…		…
1717		2092
1718	The specified interval.	2093	The specified interval.
1719		2094
1720	=item const char *path [read-only]	2095	=item const char *path [read-only]
1721		2096
1722	The filesystem path that is being watched.	2097	The file system path that is being watched.
1723		2098
1724	=back	2099	=back
1725		2100
1726	=head3 Examples	2101	=head3 Examples
1727		2102
1728	Example: Watch C</etc/passwd> for attribute changes.	2103	Example: Watch C</etc/passwd> for attribute changes.
1729		2104
1730	static void	2105	static void
1731	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2106	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732	{	2107	{
1733	/* /etc/passwd changed in some way */	2108	/* /etc/passwd changed in some way */
1734	if (w->attr.st_nlink)	2109	if (w->attr.st_nlink)
1735	{	2110	{
1736	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2111	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2112	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2113	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739	}	2114	}
1740	else	2115	else
1741	/* you shalt not abuse printf for puts */	2116	/* you shalt not abuse printf for puts */
1742	puts ("wow, /etc/passwd is not there, expect problems. "	2117	puts ("wow, /etc/passwd is not there, expect problems. "
1743	"if this is windows, they already arrived\n");	2118	"if this is windows, they already arrived\n");
1744	}	2119	}
1745		2120
1746	...	2121	...
1747	ev_stat passwd;	2122	ev_stat passwd;
1748		2123
1749	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2124	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750	ev_stat_start (loop, &passwd);	2125	ev_stat_start (loop, &passwd);
1751		2126
1752	Example: Like above, but additionally use a one-second delay so we do not	2127	Example: Like above, but additionally use a one-second delay so we do not
1753	miss updates (however, frequent updates will delay processing, too, so	2128	miss updates (however, frequent updates will delay processing, too, so
1754	one might do the work both on C<ev_stat> callback invocation I<and> on	2129	one might do the work both on C<ev_stat> callback invocation I<and> on
1755	C<ev_timer> callback invocation).	2130	C<ev_timer> callback invocation).
1756		2131
1757	static ev_stat passwd;	2132	static ev_stat passwd;
1758	static ev_timer timer;	2133	static ev_timer timer;
1759		2134
1760	static void	2135	static void
1761	timer_cb (EV_P_ ev_timer *w, int revents)	2136	timer_cb (EV_P_ ev_timer *w, int revents)
1762	{	2137	{
1763	ev_timer_stop (EV_A_ w);	2138	ev_timer_stop (EV_A_ w);
1764		2139
1765	/* now it's one second after the most recent passwd change */	2140	/* now it's one second after the most recent passwd change */
1766	}	2141	}
1767		2142
1768	static void	2143	static void
1769	stat_cb (EV_P_ ev_stat *w, int revents)	2144	stat_cb (EV_P_ ev_stat *w, int revents)
1770	{	2145	{
1771	/* reset the one-second timer */	2146	/* reset the one-second timer */
1772	ev_timer_again (EV_A_ &timer);	2147	ev_timer_again (EV_A_ &timer);
1773	}	2148	}
1774		2149
1775	...	2150	...
1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2151	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777	ev_stat_start (loop, &passwd);	2152	ev_stat_start (loop, &passwd);
1778	ev_timer_init (&timer, timer_cb, 0., 1.02);	2153	ev_timer_init (&timer, timer_cb, 0., 1.02);
1779		2154
1780		2155
1781	=head2 C<ev_idle> - when you've got nothing better to do...	2156	=head2 C<ev_idle> - when you've got nothing better to do...
1782		2157
1783	Idle watchers trigger events when no other events of the same or higher	2158	Idle watchers trigger events when no other events of the same or higher
1784	priority are pending (prepare, check and other idle watchers do not	2159	priority are pending (prepare, check and other idle watchers do not count
1785	count).	2160	as receiving "events").
1786		2161
1787	That is, as long as your process is busy handling sockets or timeouts	2162	That is, as long as your process is busy handling sockets or timeouts
1788	(or even signals, imagine) of the same or higher priority it will not be	2163	(or even signals, imagine) of the same or higher priority it will not be
1789	triggered. But when your process is idle (or only lower-priority watchers	2164	triggered. But when your process is idle (or only lower-priority watchers
1790	are pending), the idle watchers are being called once per event loop	2165	are pending), the idle watchers are being called once per event loop
…		…
1814	=head3 Examples	2189	=head3 Examples
1815		2190
1816	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2191	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817	callback, free it. Also, use no error checking, as usual.	2192	callback, free it. Also, use no error checking, as usual.
1818		2193
1819	static void	2194	static void
1820	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2195	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1821	{	2196	{
1822	free (w);	2197	free (w);
1823	// now do something you wanted to do when the program has	2198	// now do something you wanted to do when the program has
1824	// no longer anything immediate to do.	2199	// no longer anything immediate to do.
1825	}	2200	}
1826		2201
1827	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2202	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1828	ev_idle_init (idle_watcher, idle_cb);	2203	ev_idle_init (idle_watcher, idle_cb);
1829	ev_idle_start (loop, idle_cb);	2204	ev_idle_start (loop, idle_cb);
1830		2205
1831		2206
1832	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2207	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833		2208
1834	Prepare and check watchers are usually (but not always) used in tandem:	2209	Prepare and check watchers are usually (but not always) used in pairs:
1835	prepare watchers get invoked before the process blocks and check watchers	2210	prepare watchers get invoked before the process blocks and check watchers
1836	afterwards.	2211	afterwards.
1837		2212
1838	You I<must not> call C<ev_loop> or similar functions that enter	2213	You I<must not> call C<ev_loop> or similar functions that enter
1839	the current event loop from either C<ev_prepare> or C<ev_check>	2214	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1842	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2217	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1843	C<ev_check> so if you have one watcher of each kind they will always be	2218	C<ev_check> so if you have one watcher of each kind they will always be
1844	called in pairs bracketing the blocking call.	2219	called in pairs bracketing the blocking call.
1845		2220
1846	Their main purpose is to integrate other event mechanisms into libev and	2221	Their main purpose is to integrate other event mechanisms into libev and
1847	their use is somewhat advanced. This could be used, for example, to track	2222	their use is somewhat advanced. They could be used, for example, to track
1848	variable changes, implement your own watchers, integrate net-snmp or a	2223	variable changes, implement your own watchers, integrate net-snmp or a
1849	coroutine library and lots more. They are also occasionally useful if	2224	coroutine library and lots more. They are also occasionally useful if
1850	you cache some data and want to flush it before blocking (for example,	2225	you cache some data and want to flush it before blocking (for example,
1851	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2226	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1852	watcher).	2227	watcher).
1853		2228
1854	This is done by examining in each prepare call which file descriptors need	2229	This is done by examining in each prepare call which file descriptors
1855	to be watched by the other library, registering C<ev_io> watchers for	2230	need to be watched by the other library, registering C<ev_io> watchers
1856	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2231	for them and starting an C<ev_timer> watcher for any timeouts (many
1857	provide just this functionality). Then, in the check watcher you check for	2232	libraries provide exactly this functionality). Then, in the check watcher,
1858	any events that occured (by checking the pending status of all watchers	2233	you check for any events that occurred (by checking the pending status
1859	and stopping them) and call back into the library. The I/O and timer	2234	of all watchers and stopping them) and call back into the library. The
1860	callbacks will never actually be called (but must be valid nevertheless,	2235	I/O and timer callbacks will never actually be called (but must be valid
1861	because you never know, you know?).	2236	nevertheless, because you never know, you know?).
1862		2237
1863	As another example, the Perl Coro module uses these hooks to integrate	2238	As another example, the Perl Coro module uses these hooks to integrate
1864	coroutines into libev programs, by yielding to other active coroutines	2239	coroutines into libev programs, by yielding to other active coroutines
1865	during each prepare and only letting the process block if no coroutines	2240	during each prepare and only letting the process block if no coroutines
1866	are ready to run (it's actually more complicated: it only runs coroutines	2241	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1869	loop from blocking if lower-priority coroutines are active, thus mapping	2244	loop from blocking if lower-priority coroutines are active, thus mapping
1870	low-priority coroutines to idle/background tasks).	2245	low-priority coroutines to idle/background tasks).
1871		2246
1872	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2247	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1873	priority, to ensure that they are being run before any other watchers	2248	priority, to ensure that they are being run before any other watchers
		2249	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2250
1874	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2251	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1875	too) should not activate ("feed") events into libev. While libev fully	2252	activate ("feed") events into libev. While libev fully supports this, they
1876	supports this, they might get executed before other C<ev_check> watchers	2253	might get executed before other C<ev_check> watchers did their job. As
1877	did their job. As C<ev_check> watchers are often used to embed other	2254	C<ev_check> watchers are often used to embed other (non-libev) event
1878	(non-libev) event loops those other event loops might be in an unusable	2255	loops those other event loops might be in an unusable state until their
1879	state until their C<ev_check> watcher ran (always remind yourself to	2256	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1880	coexist peacefully with others).	2257	others).
1881		2258
1882	=head3 Watcher-Specific Functions and Data Members	2259	=head3 Watcher-Specific Functions and Data Members
1883		2260
1884	=over 4	2261	=over 4
1885		2262
…		…
1887		2264
1888	=item ev_check_init (ev_check *, callback)	2265	=item ev_check_init (ev_check *, callback)
1889		2266
1890	Initialises and configures the prepare or check watcher - they have no	2267	Initialises and configures the prepare or check watcher - they have no
1891	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2268	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1892	macros, but using them is utterly, utterly and completely pointless.	2269	macros, but using them is utterly, utterly, utterly and completely
		2270	pointless.
1893		2271
1894	=back	2272	=back
1895		2273
1896	=head3 Examples	2274	=head3 Examples
1897		2275
…		…
1906	and in a check watcher, destroy them and call into libadns. What follows	2284	and in a check watcher, destroy them and call into libadns. What follows
1907	is pseudo-code only of course. This requires you to either use a low	2285	is pseudo-code only of course. This requires you to either use a low
1908	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2286	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1909	the callbacks for the IO/timeout watchers might not have been called yet.	2287	the callbacks for the IO/timeout watchers might not have been called yet.
1910		2288
1911	static ev_io iow [nfd];	2289	static ev_io iow [nfd];
1912	static ev_timer tw;	2290	static ev_timer tw;
1913		2291
1914	static void	2292	static void
1915	io_cb (ev_loop *loop, ev_io *w, int revents)	2293	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1916	{	2294	{
1917	}	2295	}
1918		2296
1919	// create io watchers for each fd and a timer before blocking	2297	// create io watchers for each fd and a timer before blocking
1920	static void	2298	static void
1921	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2299	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1922	{	2300	{
1923	int timeout = 3600000;	2301	int timeout = 3600000;
1924	struct pollfd fds [nfd];	2302	struct pollfd fds [nfd];
1925	// actual code will need to loop here and realloc etc.	2303	// actual code will need to loop here and realloc etc.
1926	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2304	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927		2305
1928	/* the callback is illegal, but won't be called as we stop during check */	2306	/* the callback is illegal, but won't be called as we stop during check */
1929	ev_timer_init (&tw, 0, timeout * 1e-3);	2307	ev_timer_init (&tw, 0, timeout * 1e-3);
1930	ev_timer_start (loop, &tw);	2308	ev_timer_start (loop, &tw);
1931		2309
1932	// create one ev_io per pollfd	2310	// create one ev_io per pollfd
1933	for (int i = 0; i < nfd; ++i)	2311	for (int i = 0; i < nfd; ++i)
1934	{	2312	{
1935	ev_io_init (iow + i, io_cb, fds [i].fd,	2313	ev_io_init (iow + i, io_cb, fds [i].fd,
1936	((fds [i].events & POLLIN ? EV_READ : 0)	2314	((fds [i].events & POLLIN ? EV_READ : 0)
1937	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2315	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938		2316
1939	fds [i].revents = 0;	2317	fds [i].revents = 0;
1940	ev_io_start (loop, iow + i);	2318	ev_io_start (loop, iow + i);
1941	}	2319	}
1942	}	2320	}
1943		2321
1944	// stop all watchers after blocking	2322	// stop all watchers after blocking
1945	static void	2323	static void
1946	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2324	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1947	{	2325	{
1948	ev_timer_stop (loop, &tw);	2326	ev_timer_stop (loop, &tw);
1949		2327
1950	for (int i = 0; i < nfd; ++i)	2328	for (int i = 0; i < nfd; ++i)
1951	{	2329	{
1952	// set the relevant poll flags	2330	// set the relevant poll flags
1953	// could also call adns_processreadable etc. here	2331	// could also call adns_processreadable etc. here
1954	struct pollfd *fd = fds + i;	2332	struct pollfd *fd = fds + i;
1955	int revents = ev_clear_pending (iow + i);	2333	int revents = ev_clear_pending (iow + i);
1956	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2334	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2335	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958		2336
1959	// now stop the watcher	2337	// now stop the watcher
1960	ev_io_stop (loop, iow + i);	2338	ev_io_stop (loop, iow + i);
1961	}	2339	}
1962		2340
1963	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2341	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964	}	2342	}
1965		2343
1966	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2344	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1967	in the prepare watcher and would dispose of the check watcher.	2345	in the prepare watcher and would dispose of the check watcher.
1968		2346
1969	Method 3: If the module to be embedded supports explicit event	2347	Method 3: If the module to be embedded supports explicit event
1970	notification (adns does), you can also make use of the actual watcher	2348	notification (libadns does), you can also make use of the actual watcher
1971	callbacks, and only destroy/create the watchers in the prepare watcher.	2349	callbacks, and only destroy/create the watchers in the prepare watcher.
1972		2350
1973	static void	2351	static void
1974	timer_cb (EV_P_ ev_timer *w, int revents)	2352	timer_cb (EV_P_ ev_timer *w, int revents)
1975	{	2353	{
1976	adns_state ads = (adns_state)w->data;	2354	adns_state ads = (adns_state)w->data;
1977	update_now (EV_A);	2355	update_now (EV_A);
1978		2356
1979	adns_processtimeouts (ads, &tv_now);	2357	adns_processtimeouts (ads, &tv_now);
1980	}	2358	}
1981		2359
1982	static void	2360	static void
1983	io_cb (EV_P_ ev_io *w, int revents)	2361	io_cb (EV_P_ ev_io *w, int revents)
1984	{	2362	{
1985	adns_state ads = (adns_state)w->data;	2363	adns_state ads = (adns_state)w->data;
1986	update_now (EV_A);	2364	update_now (EV_A);
1987		2365
1988	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2366	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2367	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990	}	2368	}
1991		2369
1992	// do not ever call adns_afterpoll	2370	// do not ever call adns_afterpoll
1993		2371
1994	Method 4: Do not use a prepare or check watcher because the module you	2372	Method 4: Do not use a prepare or check watcher because the module you
1995	want to embed is too inflexible to support it. Instead, youc na override	2373	want to embed is not flexible enough to support it. Instead, you can
1996	their poll function. The drawback with this solution is that the main	2374	override their poll function. The drawback with this solution is that the
1997	loop is now no longer controllable by EV. The C<Glib::EV> module does	2375	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1998	this.	2376	this approach, effectively embedding EV as a client into the horrible
		2377	libglib event loop.
1999		2378
2000	static gint	2379	static gint
2001	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2380	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002	{	2381	{
2003	int got_events = 0;	2382	int got_events = 0;
2004		2383
2005	for (n = 0; n < nfds; ++n)	2384	for (n = 0; n < nfds; ++n)
2006	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2385	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007		2386
2008	if (timeout >= 0)	2387	if (timeout >= 0)
2009	// create/start timer	2388	// create/start timer
2010		2389
2011	// poll	2390	// poll
2012	ev_loop (EV_A_ 0);	2391	ev_loop (EV_A_ 0);
2013		2392
2014	// stop timer again	2393	// stop timer again
2015	if (timeout >= 0)	2394	if (timeout >= 0)
2016	ev_timer_stop (EV_A_ &to);	2395	ev_timer_stop (EV_A_ &to);
2017		2396
2018	// stop io watchers again - their callbacks should have set	2397	// stop io watchers again - their callbacks should have set
2019	for (n = 0; n < nfds; ++n)	2398	for (n = 0; n < nfds; ++n)
2020	ev_io_stop (EV_A_ iow [n]);	2399	ev_io_stop (EV_A_ iow [n]);
2021		2400
2022	return got_events;	2401	return got_events;
2023	}	2402	}
2024		2403
2025		2404
2026	=head2 C<ev_embed> - when one backend isn't enough...	2405	=head2 C<ev_embed> - when one backend isn't enough...
2027		2406
2028	This is a rather advanced watcher type that lets you embed one event loop	2407	This is a rather advanced watcher type that lets you embed one event loop
…		…
2034	prioritise I/O.	2413	prioritise I/O.
2035		2414
2036	As an example for a bug workaround, the kqueue backend might only support	2415	As an example for a bug workaround, the kqueue backend might only support
2037	sockets on some platform, so it is unusable as generic backend, but you	2416	sockets on some platform, so it is unusable as generic backend, but you
2038	still want to make use of it because you have many sockets and it scales	2417	still want to make use of it because you have many sockets and it scales
2039	so nicely. In this case, you would create a kqueue-based loop and embed it	2418	so nicely. In this case, you would create a kqueue-based loop and embed
2040	into your default loop (which might use e.g. poll). Overall operation will	2419	it into your default loop (which might use e.g. poll). Overall operation
2041	be a bit slower because first libev has to poll and then call kevent, but	2420	will be a bit slower because first libev has to call C<poll> and then
2042	at least you can use both at what they are best.	2421	C<kevent>, but at least you can use both mechanisms for what they are
		2422	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2043		2423
2044	As for prioritising I/O: rarely you have the case where some fds have	2424	As for prioritising I/O: under rare circumstances you have the case where
2045	to be watched and handled very quickly (with low latency), and even	2425	some fds have to be watched and handled very quickly (with low latency),
2046	priorities and idle watchers might have too much overhead. In this case	2426	and even priorities and idle watchers might have too much overhead. In
2047	you would put all the high priority stuff in one loop and all the rest in	2427	this case you would put all the high priority stuff in one loop and all
2048	a second one, and embed the second one in the first.	2428	the rest in a second one, and embed the second one in the first.
2049		2429
2050	As long as the watcher is active, the callback will be invoked every time	2430	As long as the watcher is active, the callback will be invoked every time
2051	there might be events pending in the embedded loop. The callback must then	2431	there might be events pending in the embedded loop. The callback must then
2052	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2432	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2053	their callbacks (you could also start an idle watcher to give the embedded	2433	their callbacks (you could also start an idle watcher to give the embedded
…		…
2061	interested in that.	2441	interested in that.
2062		2442
2063	Also, there have not currently been made special provisions for forking:	2443	Also, there have not currently been made special provisions for forking:
2064	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2444	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2065	but you will also have to stop and restart any C<ev_embed> watchers	2445	but you will also have to stop and restart any C<ev_embed> watchers
2066	yourself.	2446	yourself - but you can use a fork watcher to handle this automatically,
		2447	and future versions of libev might do just that.
2067		2448
2068	Unfortunately, not all backends are embeddable, only the ones returned by	2449	Unfortunately, not all backends are embeddable: only the ones returned by
2069	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2450	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2070	portable one.	2451	portable one.
2071		2452
2072	So when you want to use this feature you will always have to be prepared	2453	So when you want to use this feature you will always have to be prepared
2073	that you cannot get an embeddable loop. The recommended way to get around	2454	that you cannot get an embeddable loop. The recommended way to get around
2074	this is to have a separate variables for your embeddable loop, try to	2455	this is to have a separate variables for your embeddable loop, try to
2075	create it, and if that fails, use the normal loop for everything.	2456	create it, and if that fails, use the normal loop for everything.
2076		2457
		2458	=head3 C<ev_embed> and fork
		2459
		2460	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2461	automatically be applied to the embedded loop as well, so no special
		2462	fork handling is required in that case. When the watcher is not running,
		2463	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2464	as applicable.
		2465
2077	=head3 Watcher-Specific Functions and Data Members	2466	=head3 Watcher-Specific Functions and Data Members
2078		2467
2079	=over 4	2468	=over 4
2080		2469
2081	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2470	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2084		2473
2085	Configures the watcher to embed the given loop, which must be	2474	Configures the watcher to embed the given loop, which must be
2086	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2475	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087	invoked automatically, otherwise it is the responsibility of the callback	2476	invoked automatically, otherwise it is the responsibility of the callback
2088	to invoke it (it will continue to be called until the sweep has been done,	2477	to invoke it (it will continue to be called until the sweep has been done,
2089	if you do not want thta, you need to temporarily stop the embed watcher).	2478	if you do not want that, you need to temporarily stop the embed watcher).
2090		2479
2091	=item ev_embed_sweep (loop, ev_embed *)	2480	=item ev_embed_sweep (loop, ev_embed *)
2092		2481
2093	Make a single, non-blocking sweep over the embedded loop. This works	2482	Make a single, non-blocking sweep over the embedded loop. This works
2094	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2483	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095	apropriate way for embedded loops.	2484	appropriate way for embedded loops.
2096		2485
2097	=item struct ev_loop *other [read-only]	2486	=item struct ev_loop *other [read-only]
2098		2487
2099	The embedded event loop.	2488	The embedded event loop.
2100		2489
…		…
2102		2491
2103	=head3 Examples	2492	=head3 Examples
2104		2493
2105	Example: Try to get an embeddable event loop and embed it into the default	2494	Example: Try to get an embeddable event loop and embed it into the default
2106	event loop. If that is not possible, use the default loop. The default	2495	event loop. If that is not possible, use the default loop. The default
2107	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2496	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2108	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2497	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109	used).	2498	used).
2110		2499
2111	struct ev_loop *loop_hi = ev_default_init (0);	2500	struct ev_loop *loop_hi = ev_default_init (0);
2112	struct ev_loop *loop_lo = 0;	2501	struct ev_loop *loop_lo = 0;
2113	struct ev_embed embed;	2502	ev_embed embed;
2114		2503
2115	// see if there is a chance of getting one that works	2504	// see if there is a chance of getting one that works
2116	// (remember that a flags value of 0 means autodetection)	2505	// (remember that a flags value of 0 means autodetection)
2117	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2506	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2507	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119	: 0;	2508	: 0;
2120		2509
2121	// if we got one, then embed it, otherwise default to loop_hi	2510	// if we got one, then embed it, otherwise default to loop_hi
2122	if (loop_lo)	2511	if (loop_lo)
2123	{	2512	{
2124	ev_embed_init (&embed, 0, loop_lo);	2513	ev_embed_init (&embed, 0, loop_lo);
2125	ev_embed_start (loop_hi, &embed);	2514	ev_embed_start (loop_hi, &embed);
2126	}	2515	}
2127	else	2516	else
2128	loop_lo = loop_hi;	2517	loop_lo = loop_hi;
2129		2518
2130	Example: Check if kqueue is available but not recommended and create	2519	Example: Check if kqueue is available but not recommended and create
2131	a kqueue backend for use with sockets (which usually work with any	2520	a kqueue backend for use with sockets (which usually work with any
2132	kqueue implementation). Store the kqueue/socket-only event loop in	2521	kqueue implementation). Store the kqueue/socket-only event loop in
2133	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2522	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134		2523
2135	struct ev_loop *loop = ev_default_init (0);	2524	struct ev_loop *loop = ev_default_init (0);
2136	struct ev_loop *loop_socket = 0;	2525	struct ev_loop *loop_socket = 0;
2137	struct ev_embed embed;	2526	ev_embed embed;
2138		2527
2139	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2528	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2529	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141	{	2530	{
2142	ev_embed_init (&embed, 0, loop_socket);	2531	ev_embed_init (&embed, 0, loop_socket);
2143	ev_embed_start (loop, &embed);	2532	ev_embed_start (loop, &embed);
2144	}	2533	}
2145		2534
2146	if (!loop_socket)	2535	if (!loop_socket)
2147	loop_socket = loop;	2536	loop_socket = loop;
2148		2537
2149	// now use loop_socket for all sockets, and loop for everything else	2538	// now use loop_socket for all sockets, and loop for everything else
2150		2539
2151		2540
2152	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2541	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153		2542
2154	Fork watchers are called when a C<fork ()> was detected (usually because	2543	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2198	is that the author does not know of a simple (or any) algorithm for a	2587	is that the author does not know of a simple (or any) algorithm for a
2199	multiple-writer-single-reader queue that works in all cases and doesn't	2588	multiple-writer-single-reader queue that works in all cases and doesn't
2200	need elaborate support such as pthreads.	2589	need elaborate support such as pthreads.
2201		2590
2202	That means that if you want to queue data, you have to provide your own	2591	That means that if you want to queue data, you have to provide your own
2203	queue. But at least I can tell you would implement locking around your	2592	queue. But at least I can tell you how to implement locking around your
2204	queue:	2593	queue:
2205		2594
2206	=over 4	2595	=over 4
2207		2596
2208	=item queueing from a signal handler context	2597	=item queueing from a signal handler context
2209		2598
2210	To implement race-free queueing, you simply add to the queue in the signal	2599	To implement race-free queueing, you simply add to the queue in the signal
2211	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2600	handler but you block the signal handler in the watcher callback. Here is
2212	some fictitiuous SIGUSR1 handler:	2601	an example that does that for some fictitious SIGUSR1 handler:
2213		2602
2214	static ev_async mysig;	2603	static ev_async mysig;
2215		2604
2216	static void	2605	static void
2217	sigusr1_handler (void)	2606	sigusr1_handler (void)
…		…
2283	=over 4	2672	=over 4
2284		2673
2285	=item ev_async_init (ev_async *, callback)	2674	=item ev_async_init (ev_async *, callback)
2286		2675
2287	Initialises and configures the async watcher - it has no parameters of any	2676	Initialises and configures the async watcher - it has no parameters of any
2288	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2677	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2289	believe me.	2678	trust me.
2290		2679
2291	=item ev_async_send (loop, ev_async *)	2680	=item ev_async_send (loop, ev_async *)
2292		2681
2293	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2682	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2683	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2295	C<ev_feed_event>, this call is safe to do in other threads, signal or	2684	C<ev_feed_event>, this call is safe to do from other threads, signal or
2296	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2685	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297	section below on what exactly this means).	2686	section below on what exactly this means).
2298		2687
2299	This call incurs the overhead of a syscall only once per loop iteration,	2688	This call incurs the overhead of a system call only once per loop iteration,
2300	so while the overhead might be noticable, it doesn't apply to repeated	2689	so while the overhead might be noticeable, it doesn't apply to repeated
2301	calls to C<ev_async_send>.	2690	calls to C<ev_async_send>.
2302		2691
2303	=item bool = ev_async_pending (ev_async *)	2692	=item bool = ev_async_pending (ev_async *)
2304		2693
2305	Returns a non-zero value when C<ev_async_send> has been called on the	2694	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2307	event loop.	2696	event loop.
2308		2697
2309	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2698	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2310	the loop iterates next and checks for the watcher to have become active,	2699	the loop iterates next and checks for the watcher to have become active,
2311	it will reset the flag again. C<ev_async_pending> can be used to very	2700	it will reset the flag again. C<ev_async_pending> can be used to very
2312	quickly check wether invoking the loop might be a good idea.	2701	quickly check whether invoking the loop might be a good idea.
2313		2702
2314	Not that this does I<not> check wether the watcher itself is pending, only	2703	Not that this does I<not> check whether the watcher itself is pending, only
2315	wether it has been requested to make this watcher pending.	2704	whether it has been requested to make this watcher pending.
2316		2705
2317	=back	2706	=back
2318		2707
2319		2708
2320	=head1 OTHER FUNCTIONS	2709	=head1 OTHER FUNCTIONS
…		…
2324	=over 4	2713	=over 4
2325		2714
2326	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2715	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2327		2716
2328	This function combines a simple timer and an I/O watcher, calls your	2717	This function combines a simple timer and an I/O watcher, calls your
2329	callback on whichever event happens first and automatically stop both	2718	callback on whichever event happens first and automatically stops both
2330	watchers. This is useful if you want to wait for a single event on an fd	2719	watchers. This is useful if you want to wait for a single event on an fd
2331	or timeout without having to allocate/configure/start/stop/free one or	2720	or timeout without having to allocate/configure/start/stop/free one or
2332	more watchers yourself.	2721	more watchers yourself.
2333		2722
2334	If C<fd> is less than 0, then no I/O watcher will be started and events	2723	If C<fd> is less than 0, then no I/O watcher will be started and the
2335	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2724	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2336	C<events> set will be craeted and started.	2725	the given C<fd> and C<events> set will be created and started.
2337		2726
2338	If C<timeout> is less than 0, then no timeout watcher will be	2727	If C<timeout> is less than 0, then no timeout watcher will be
2339	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2728	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2340	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2729	repeat = 0) will be started. C<0> is a valid timeout.
2341	dubious value.
2342		2730
2343	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2731	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2344	passed an C<revents> set like normal event callbacks (a combination of	2732	passed an C<revents> set like normal event callbacks (a combination of
2345	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2733	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346	value passed to C<ev_once>:	2734	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2735	a timeout and an io event at the same time - you probably should give io
		2736	events precedence.
2347		2737
		2738	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2739
2348	static void stdin_ready (int revents, void *arg)	2740	static void stdin_ready (int revents, void *arg)
2349	{	2741	{
2350	if (revents & EV_TIMEOUT)
2351	/* doh, nothing entered */;
2352	else if (revents & EV_READ)	2742	if (revents & EV_READ)
2353	/* stdin might have data for us, joy! */;	2743	/* stdin might have data for us, joy! */;
		2744	else if (revents & EV_TIMEOUT)
		2745	/* doh, nothing entered */;
2354	}	2746	}
2355		2747
2356	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2748	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357		2749
2358	=item ev_feed_event (ev_loop *, watcher *, int revents)	2750	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2359		2751
2360	Feeds the given event set into the event loop, as if the specified event	2752	Feeds the given event set into the event loop, as if the specified event
2361	had happened for the specified watcher (which must be a pointer to an	2753	had happened for the specified watcher (which must be a pointer to an
2362	initialised but not necessarily started event watcher).	2754	initialised but not necessarily started event watcher).
2363		2755
2364	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2756	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2365		2757
2366	Feed an event on the given fd, as if a file descriptor backend detected	2758	Feed an event on the given fd, as if a file descriptor backend detected
2367	the given events it.	2759	the given events it.
2368		2760
2369	=item ev_feed_signal_event (ev_loop *loop, int signum)	2761	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2370		2762
2371	Feed an event as if the given signal occured (C<loop> must be the default	2763	Feed an event as if the given signal occurred (C<loop> must be the default
2372	loop!).	2764	loop!).
2373		2765
2374	=back	2766	=back
2375		2767
2376		2768
…		…
2405	=back	2797	=back
2406		2798
2407	=head1 C++ SUPPORT	2799	=head1 C++ SUPPORT
2408		2800
2409	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2801	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410	you to use some convinience methods to start/stop watchers and also change	2802	you to use some convenience methods to start/stop watchers and also change
2411	the callback model to a model using method callbacks on objects.	2803	the callback model to a model using method callbacks on objects.
2412		2804
2413	To use it,	2805	To use it,
2414		2806
2415	#include <ev++.h>	2807	#include <ev++.h>
2416		2808
2417	This automatically includes F<ev.h> and puts all of its definitions (many	2809	This automatically includes F<ev.h> and puts all of its definitions (many
2418	of them macros) into the global namespace. All C++ specific things are	2810	of them macros) into the global namespace. All C++ specific things are
2419	put into the C<ev> namespace. It should support all the same embedding	2811	put into the C<ev> namespace. It should support all the same embedding
2420	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2812	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2487	your compiler is good :), then the method will be fully inlined into the	2879	your compiler is good :), then the method will be fully inlined into the
2488	thunking function, making it as fast as a direct C callback.	2880	thunking function, making it as fast as a direct C callback.
2489		2881
2490	Example: simple class declaration and watcher initialisation	2882	Example: simple class declaration and watcher initialisation
2491		2883
2492	struct myclass	2884	struct myclass
2493	{	2885	{
2494	void io_cb (ev::io &w, int revents) { }	2886	void io_cb (ev::io &w, int revents) { }
2495	}	2887	}
2496		2888
2497	myclass obj;	2889	myclass obj;
2498	ev::io iow;	2890	ev::io iow;
2499	iow.set <myclass, &myclass::io_cb> (&obj);	2891	iow.set <myclass, &myclass::io_cb> (&obj);
2500		2892
2501	=item w->set<function> (void *data = 0)	2893	=item w->set<function> (void *data = 0)
2502		2894
2503	Also sets a callback, but uses a static method or plain function as	2895	Also sets a callback, but uses a static method or plain function as
2504	callback. The optional C<data> argument will be stored in the watcher's	2896	callback. The optional C<data> argument will be stored in the watcher's
…		…
2506		2898
2507	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2899	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2508		2900
2509	See the method-C<set> above for more details.	2901	See the method-C<set> above for more details.
2510		2902
2511	Example:	2903	Example: Use a plain function as callback.
2512		2904
2513	static void io_cb (ev::io &w, int revents) { }	2905	static void io_cb (ev::io &w, int revents) { }
2514	iow.set <io_cb> ();	2906	iow.set <io_cb> ();
2515		2907
2516	=item w->set (struct ev_loop *)	2908	=item w->set (struct ev_loop *)
2517		2909
2518	Associates a different C<struct ev_loop> with this watcher. You can only	2910	Associates a different C<struct ev_loop> with this watcher. You can only
2519	do this when the watcher is inactive (and not pending either).	2911	do this when the watcher is inactive (and not pending either).
2520		2912
2521	=item w->set ([args])	2913	=item w->set ([arguments])
2522		2914
2523	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2915	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2524	called at least once. Unlike the C counterpart, an active watcher gets	2916	called at least once. Unlike the C counterpart, an active watcher gets
2525	automatically stopped and restarted when reconfiguring it with this	2917	automatically stopped and restarted when reconfiguring it with this
2526	method.	2918	method.
2527		2919
2528	=item w->start ()	2920	=item w->start ()
…		…
2552	=back	2944	=back
2553		2945
2554	Example: Define a class with an IO and idle watcher, start one of them in	2946	Example: Define a class with an IO and idle watcher, start one of them in
2555	the constructor.	2947	the constructor.
2556		2948
2557	class myclass	2949	class myclass
2558	{	2950	{
2559	ev::io io; void io_cb (ev::io &w, int revents);	2951	ev::io io ; void io_cb (ev::io &w, int revents);
2560	ev:idle idle void idle_cb (ev::idle &w, int revents);	2952	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2561		2953
2562	myclass (int fd)	2954	myclass (int fd)
2563	{	2955	{
2564	io .set <myclass, &myclass::io_cb > (this);	2956	io .set <myclass, &myclass::io_cb > (this);
2565	idle.set <myclass, &myclass::idle_cb> (this);	2957	idle.set <myclass, &myclass::idle_cb> (this);
2566		2958
2567	io.start (fd, ev::READ);	2959	io.start (fd, ev::READ);
2568	}	2960	}
2569	};	2961	};
2570		2962
2571		2963
2572	=head1 OTHER LANGUAGE BINDINGS	2964	=head1 OTHER LANGUAGE BINDINGS
2573		2965
2574	Libev does not offer other language bindings itself, but bindings for a	2966	Libev does not offer other language bindings itself, but bindings for a
2575	numbe rof languages exist in the form of third-party packages. If you know	2967	number of languages exist in the form of third-party packages. If you know
2576	any interesting language binding in addition to the ones listed here, drop	2968	any interesting language binding in addition to the ones listed here, drop
2577	me a note.	2969	me a note.
2578		2970
2579	=over 4	2971	=over 4
2580		2972
2581	=item Perl	2973	=item Perl
2582		2974
2583	The EV module implements the full libev API and is actually used to test	2975	The EV module implements the full libev API and is actually used to test
2584	libev. EV is developed together with libev. Apart from the EV core module,	2976	libev. EV is developed together with libev. Apart from the EV core module,
2585	there are additional modules that implement libev-compatible interfaces	2977	there are additional modules that implement libev-compatible interfaces
2586	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2978	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2587	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2979	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2980	and C<EV::Glib>).
2588		2981
2589	It can be found and installed via CPAN, its homepage is found at	2982	It can be found and installed via CPAN, its homepage is at
2590	L<http://software.schmorp.de/pkg/EV>.	2983	L<http://software.schmorp.de/pkg/EV>.
2591		2984
		2985	=item Python
		2986
		2987	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2988	seems to be quite complete and well-documented. Note, however, that the
		2989	patch they require for libev is outright dangerous as it breaks the ABI
		2990	for everybody else, and therefore, should never be applied in an installed
		2991	libev (if python requires an incompatible ABI then it needs to embed
		2992	libev).
		2993
2592	=item Ruby	2994	=item Ruby
2593		2995
2594	Tony Arcieri has written a ruby extension that offers access to a subset	2996	Tony Arcieri has written a ruby extension that offers access to a subset
2595	of the libev API and adds filehandle abstractions, asynchronous DNS and	2997	of the libev API and adds file handle abstractions, asynchronous DNS and
2596	more on top of it. It can be found via gem servers. Its homepage is at	2998	more on top of it. It can be found via gem servers. Its homepage is at
2597	L<http://rev.rubyforge.org/>.	2999	L<http://rev.rubyforge.org/>.
2598		3000
2599	=item D	3001	=item D
2600		3002
2601	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3003	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2602	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3004	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3005
		3006	=item Ocaml
		3007
		3008	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3009	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2603		3010
2604	=back	3011	=back
2605		3012
2606		3013
2607	=head1 MACRO MAGIC	3014	=head1 MACRO MAGIC
2608		3015
2609	Libev can be compiled with a variety of options, the most fundamantal	3016	Libev can be compiled with a variety of options, the most fundamental
2610	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3017	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611	functions and callbacks have an initial C<struct ev_loop *> argument.	3018	functions and callbacks have an initial C<struct ev_loop *> argument.
2612		3019
2613	To make it easier to write programs that cope with either variant, the	3020	To make it easier to write programs that cope with either variant, the
2614	following macros are defined:	3021	following macros are defined:
…		…
2619		3026
2620	This provides the loop I<argument> for functions, if one is required ("ev	3027	This provides the loop I<argument> for functions, if one is required ("ev
2621	loop argument"). The C<EV_A> form is used when this is the sole argument,	3028	loop argument"). The C<EV_A> form is used when this is the sole argument,
2622	C<EV_A_> is used when other arguments are following. Example:	3029	C<EV_A_> is used when other arguments are following. Example:
2623		3030
2624	ev_unref (EV_A);	3031	ev_unref (EV_A);
2625	ev_timer_add (EV_A_ watcher);	3032	ev_timer_add (EV_A_ watcher);
2626	ev_loop (EV_A_ 0);	3033	ev_loop (EV_A_ 0);
2627		3034
2628	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3035	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629	which is often provided by the following macro.	3036	which is often provided by the following macro.
2630		3037
2631	=item C<EV_P>, C<EV_P_>	3038	=item C<EV_P>, C<EV_P_>
2632		3039
2633	This provides the loop I<parameter> for functions, if one is required ("ev	3040	This provides the loop I<parameter> for functions, if one is required ("ev
2634	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3041	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2635	C<EV_P_> is used when other parameters are following. Example:	3042	C<EV_P_> is used when other parameters are following. Example:
2636		3043
2637	// this is how ev_unref is being declared	3044	// this is how ev_unref is being declared
2638	static void ev_unref (EV_P);	3045	static void ev_unref (EV_P);
2639		3046
2640	// this is how you can declare your typical callback	3047	// this is how you can declare your typical callback
2641	static void cb (EV_P_ ev_timer *w, int revents)	3048	static void cb (EV_P_ ev_timer *w, int revents)
2642		3049
2643	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3050	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644	suitable for use with C<EV_A>.	3051	suitable for use with C<EV_A>.
2645		3052
2646	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3053	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2662		3069
2663	Example: Declare and initialise a check watcher, utilising the above	3070	Example: Declare and initialise a check watcher, utilising the above
2664	macros so it will work regardless of whether multiple loops are supported	3071	macros so it will work regardless of whether multiple loops are supported
2665	or not.	3072	or not.
2666		3073
2667	static void	3074	static void
2668	check_cb (EV_P_ ev_timer *w, int revents)	3075	check_cb (EV_P_ ev_timer *w, int revents)
2669	{	3076	{
2670	ev_check_stop (EV_A_ w);	3077	ev_check_stop (EV_A_ w);
2671	}	3078	}
2672		3079
2673	ev_check check;	3080	ev_check check;
2674	ev_check_init (&check, check_cb);	3081	ev_check_init (&check, check_cb);
2675	ev_check_start (EV_DEFAULT_ &check);	3082	ev_check_start (EV_DEFAULT_ &check);
2676	ev_loop (EV_DEFAULT_ 0);	3083	ev_loop (EV_DEFAULT_ 0);
2677		3084
2678	=head1 EMBEDDING	3085	=head1 EMBEDDING
2679		3086
2680	Libev can (and often is) directly embedded into host	3087	Libev can (and often is) directly embedded into host
2681	applications. Examples of applications that embed it include the Deliantra	3088	applications. Examples of applications that embed it include the Deliantra
…		…
2688	libev somewhere in your source tree).	3095	libev somewhere in your source tree).
2689		3096
2690	=head2 FILESETS	3097	=head2 FILESETS
2691		3098
2692	Depending on what features you need you need to include one or more sets of files	3099	Depending on what features you need you need to include one or more sets of files
2693	in your app.	3100	in your application.
2694		3101
2695	=head3 CORE EVENT LOOP	3102	=head3 CORE EVENT LOOP
2696		3103
2697	To include only the libev core (all the C<ev_*> functions), with manual	3104	To include only the libev core (all the C<ev_*> functions), with manual
2698	configuration (no autoconf):	3105	configuration (no autoconf):
2699		3106
2700	#define EV_STANDALONE 1	3107	#define EV_STANDALONE 1
2701	#include "ev.c"	3108	#include "ev.c"
2702		3109
2703	This will automatically include F<ev.h>, too, and should be done in a	3110	This will automatically include F<ev.h>, too, and should be done in a
2704	single C source file only to provide the function implementations. To use	3111	single C source file only to provide the function implementations. To use
2705	it, do the same for F<ev.h> in all files wishing to use this API (best	3112	it, do the same for F<ev.h> in all files wishing to use this API (best
2706	done by writing a wrapper around F<ev.h> that you can include instead and	3113	done by writing a wrapper around F<ev.h> that you can include instead and
2707	where you can put other configuration options):	3114	where you can put other configuration options):
2708		3115
2709	#define EV_STANDALONE 1	3116	#define EV_STANDALONE 1
2710	#include "ev.h"	3117	#include "ev.h"
2711		3118
2712	Both header files and implementation files can be compiled with a C++	3119	Both header files and implementation files can be compiled with a C++
2713	compiler (at least, thats a stated goal, and breakage will be treated	3120	compiler (at least, that's a stated goal, and breakage will be treated
2714	as a bug).	3121	as a bug).
2715		3122
2716	You need the following files in your source tree, or in a directory	3123	You need the following files in your source tree, or in a directory
2717	in your include path (e.g. in libev/ when using -Ilibev):	3124	in your include path (e.g. in libev/ when using -Ilibev):
2718		3125
2719	ev.h	3126	ev.h
2720	ev.c	3127	ev.c
2721	ev_vars.h	3128	ev_vars.h
2722	ev_wrap.h	3129	ev_wrap.h
2723		3130
2724	ev_win32.c required on win32 platforms only	3131	ev_win32.c required on win32 platforms only
2725		3132
2726	ev_select.c only when select backend is enabled (which is enabled by default)	3133	ev_select.c only when select backend is enabled (which is enabled by default)
2727	ev_poll.c only when poll backend is enabled (disabled by default)	3134	ev_poll.c only when poll backend is enabled (disabled by default)
2728	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3135	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2729	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3136	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2730	ev_port.c only when the solaris port backend is enabled (disabled by default)	3137	ev_port.c only when the solaris port backend is enabled (disabled by default)
2731		3138
2732	F<ev.c> includes the backend files directly when enabled, so you only need	3139	F<ev.c> includes the backend files directly when enabled, so you only need
2733	to compile this single file.	3140	to compile this single file.
2734		3141
2735	=head3 LIBEVENT COMPATIBILITY API	3142	=head3 LIBEVENT COMPATIBILITY API
2736		3143
2737	To include the libevent compatibility API, also include:	3144	To include the libevent compatibility API, also include:
2738		3145
2739	#include "event.c"	3146	#include "event.c"
2740		3147
2741	in the file including F<ev.c>, and:	3148	in the file including F<ev.c>, and:
2742		3149
2743	#include "event.h"	3150	#include "event.h"
2744		3151
2745	in the files that want to use the libevent API. This also includes F<ev.h>.	3152	in the files that want to use the libevent API. This also includes F<ev.h>.
2746		3153
2747	You need the following additional files for this:	3154	You need the following additional files for this:
2748		3155
2749	event.h	3156	event.h
2750	event.c	3157	event.c
2751		3158
2752	=head3 AUTOCONF SUPPORT	3159	=head3 AUTOCONF SUPPORT
2753		3160
2754	Instead of using C<EV_STANDALONE=1> and providing your config in	3161	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2755	whatever way you want, you can also C<m4_include([libev.m4])> in your	3162	whatever way you want, you can also C<m4_include([libev.m4])> in your
2756	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3163	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757	include F<config.h> and configure itself accordingly.	3164	include F<config.h> and configure itself accordingly.
2758		3165
2759	For this of course you need the m4 file:	3166	For this of course you need the m4 file:
2760		3167
2761	libev.m4	3168	libev.m4
2762		3169
2763	=head2 PREPROCESSOR SYMBOLS/MACROS	3170	=head2 PREPROCESSOR SYMBOLS/MACROS
2764		3171
2765	Libev can be configured via a variety of preprocessor symbols you have to	3172	Libev can be configured via a variety of preprocessor symbols you have to
2766	define before including any of its files. The default in the absense of	3173	define before including any of its files. The default in the absence of
2767	autoconf is noted for every option.	3174	autoconf is documented for every option.
2768		3175
2769	=over 4	3176	=over 4
2770		3177
2771	=item EV_STANDALONE	3178	=item EV_STANDALONE
2772		3179
…		…
2777	F<event.h> that are not directly supported by the libev core alone.	3184	F<event.h> that are not directly supported by the libev core alone.
2778		3185
2779	=item EV_USE_MONOTONIC	3186	=item EV_USE_MONOTONIC
2780		3187
2781	If defined to be C<1>, libev will try to detect the availability of the	3188	If defined to be C<1>, libev will try to detect the availability of the
2782	monotonic clock option at both compiletime and runtime. Otherwise no use	3189	monotonic clock option at both compile time and runtime. Otherwise no use
2783	of the monotonic clock option will be attempted. If you enable this, you	3190	of the monotonic clock option will be attempted. If you enable this, you
2784	usually have to link against librt or something similar. Enabling it when	3191	usually have to link against librt or something similar. Enabling it when
2785	the functionality isn't available is safe, though, although you have	3192	the functionality isn't available is safe, though, although you have
2786	to make sure you link against any libraries where the C<clock_gettime>	3193	to make sure you link against any libraries where the C<clock_gettime>
2787	function is hiding in (often F<-lrt>).	3194	function is hiding in (often F<-lrt>).
2788		3195
2789	=item EV_USE_REALTIME	3196	=item EV_USE_REALTIME
2790		3197
2791	If defined to be C<1>, libev will try to detect the availability of the	3198	If defined to be C<1>, libev will try to detect the availability of the
2792	realtime clock option at compiletime (and assume its availability at	3199	real-time clock option at compile time (and assume its availability at
2793	runtime if successful). Otherwise no use of the realtime clock option will	3200	runtime if successful). Otherwise no use of the real-time clock option will
2794	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3201	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2795	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3202	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2796	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3203	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2797		3204
2798	=item EV_USE_NANOSLEEP	3205	=item EV_USE_NANOSLEEP
…		…
2809	2.7 or newer, otherwise disabled.	3216	2.7 or newer, otherwise disabled.
2810		3217
2811	=item EV_USE_SELECT	3218	=item EV_USE_SELECT
2812		3219
2813	If undefined or defined to be C<1>, libev will compile in support for the	3220	If undefined or defined to be C<1>, libev will compile in support for the
2814	C<select>(2) backend. No attempt at autodetection will be done: if no	3221	C<select>(2) backend. No attempt at auto-detection will be done: if no
2815	other method takes over, select will be it. Otherwise the select backend	3222	other method takes over, select will be it. Otherwise the select backend
2816	will not be compiled in.	3223	will not be compiled in.
2817		3224
2818	=item EV_SELECT_USE_FD_SET	3225	=item EV_SELECT_USE_FD_SET
2819		3226
2820	If defined to C<1>, then the select backend will use the system C<fd_set>	3227	If defined to C<1>, then the select backend will use the system C<fd_set>
2821	structure. This is useful if libev doesn't compile due to a missing	3228	structure. This is useful if libev doesn't compile due to a missing
2822	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3229	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2823	exotic systems. This usually limits the range of file descriptors to some	3230	exotic systems. This usually limits the range of file descriptors to some
2824	low limit such as 1024 or might have other limitations (winsocket only	3231	low limit such as 1024 or might have other limitations (winsocket only
2825	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3232	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2826	influence the size of the C<fd_set> used.	3233	influence the size of the C<fd_set> used.
2827		3234
…		…
2876	otherwise another method will be used as fallback. This is the preferred	3283	otherwise another method will be used as fallback. This is the preferred
2877	backend for Solaris 10 systems.	3284	backend for Solaris 10 systems.
2878		3285
2879	=item EV_USE_DEVPOLL	3286	=item EV_USE_DEVPOLL
2880		3287
2881	reserved for future expansion, works like the USE symbols above.	3288	Reserved for future expansion, works like the USE symbols above.
2882		3289
2883	=item EV_USE_INOTIFY	3290	=item EV_USE_INOTIFY
2884		3291
2885	If defined to be C<1>, libev will compile in support for the Linux inotify	3292	If defined to be C<1>, libev will compile in support for the Linux inotify
2886	interface to speed up C<ev_stat> watchers. Its actual availability will	3293	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2893	access is atomic with respect to other threads or signal contexts. No such	3300	access is atomic with respect to other threads or signal contexts. No such
2894	type is easily found in the C language, so you can provide your own type	3301	type is easily found in the C language, so you can provide your own type
2895	that you know is safe for your purposes. It is used both for signal handler "locking"	3302	that you know is safe for your purposes. It is used both for signal handler "locking"
2896	as well as for signal and thread safety in C<ev_async> watchers.	3303	as well as for signal and thread safety in C<ev_async> watchers.
2897		3304
2898	In the absense of this define, libev will use C<sig_atomic_t volatile>	3305	In the absence of this define, libev will use C<sig_atomic_t volatile>
2899	(from F<signal.h>), which is usually good enough on most platforms.	3306	(from F<signal.h>), which is usually good enough on most platforms.
2900		3307
2901	=item EV_H	3308	=item EV_H
2902		3309
2903	The name of the F<ev.h> header file used to include it. The default if	3310	The name of the F<ev.h> header file used to include it. The default if
…		…
2942	When doing priority-based operations, libev usually has to linearly search	3349	When doing priority-based operations, libev usually has to linearly search
2943	all the priorities, so having many of them (hundreds) uses a lot of space	3350	all the priorities, so having many of them (hundreds) uses a lot of space
2944	and time, so using the defaults of five priorities (-2 .. +2) is usually	3351	and time, so using the defaults of five priorities (-2 .. +2) is usually
2945	fine.	3352	fine.
2946		3353
2947	If your embedding app does not need any priorities, defining these both to	3354	If your embedding application does not need any priorities, defining these
2948	C<0> will save some memory and cpu.	3355	both to C<0> will save some memory and CPU.
2949		3356
2950	=item EV_PERIODIC_ENABLE	3357	=item EV_PERIODIC_ENABLE
2951		3358
2952	If undefined or defined to be C<1>, then periodic timers are supported. If	3359	If undefined or defined to be C<1>, then periodic timers are supported. If
2953	defined to be C<0>, then they are not. Disabling them saves a few kB of	3360	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2960	code.	3367	code.
2961		3368
2962	=item EV_EMBED_ENABLE	3369	=item EV_EMBED_ENABLE
2963		3370
2964	If undefined or defined to be C<1>, then embed watchers are supported. If	3371	If undefined or defined to be C<1>, then embed watchers are supported. If
2965	defined to be C<0>, then they are not.	3372	defined to be C<0>, then they are not. Embed watchers rely on most other
		3373	watcher types, which therefore must not be disabled.
2966		3374
2967	=item EV_STAT_ENABLE	3375	=item EV_STAT_ENABLE
2968		3376
2969	If undefined or defined to be C<1>, then stat watchers are supported. If	3377	If undefined or defined to be C<1>, then stat watchers are supported. If
2970	defined to be C<0>, then they are not.	3378	defined to be C<0>, then they are not.
…		…
2981		3389
2982	=item EV_MINIMAL	3390	=item EV_MINIMAL
2983		3391
2984	If you need to shave off some kilobytes of code at the expense of some	3392	If you need to shave off some kilobytes of code at the expense of some
2985	speed, define this symbol to C<1>. Currently this is used to override some	3393	speed, define this symbol to C<1>. Currently this is used to override some
2986	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3394	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2987	much smaller 2-heap for timer management over the default 4-heap.	3395	much smaller 2-heap for timer management over the default 4-heap.
2988		3396
2989	=item EV_PID_HASHSIZE	3397	=item EV_PID_HASHSIZE
2990		3398
2991	C<ev_child> watchers use a small hash table to distribute workload by	3399	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3002	two).	3410	two).
3003		3411
3004	=item EV_USE_4HEAP	3412	=item EV_USE_4HEAP
3005		3413
3006	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3414	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3007	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3415	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3008	to C<1>. The 4-heap uses more complicated (longer) code but has a	3416	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3009	noticable after performance with many (thousands) of watchers.	3417	faster performance with many (thousands) of watchers.
3010		3418
3011	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3419	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3012	(disabled).	3420	(disabled).
3013		3421
3014	=item EV_HEAP_CACHE_AT	3422	=item EV_HEAP_CACHE_AT
3015		3423
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3424	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev can cache the timestamp (I<at>) within	3425	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3018	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3426	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3019	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3427	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3020	but avoids random read accesses on heap changes. This noticably improves	3428	but avoids random read accesses on heap changes. This improves performance
3021	performance noticably with with many (hundreds) of watchers.	3429	noticeably with many (hundreds) of watchers.
3022		3430
3023	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3431	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3024	(disabled).	3432	(disabled).
		3433
		3434	=item EV_VERIFY
		3435
		3436	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3437	be done: If set to C<0>, no internal verification code will be compiled
		3438	in. If set to C<1>, then verification code will be compiled in, but not
		3439	called. If set to C<2>, then the internal verification code will be
		3440	called once per loop, which can slow down libev. If set to C<3>, then the
		3441	verification code will be called very frequently, which will slow down
		3442	libev considerably.
		3443
		3444	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3445	C<0>.
3025		3446
3026	=item EV_COMMON	3447	=item EV_COMMON
3027		3448
3028	By default, all watchers have a C<void *data> member. By redefining	3449	By default, all watchers have a C<void *data> member. By redefining
3029	this macro to a something else you can include more and other types of	3450	this macro to a something else you can include more and other types of
3030	members. You have to define it each time you include one of the files,	3451	members. You have to define it each time you include one of the files,
3031	though, and it must be identical each time.	3452	though, and it must be identical each time.
3032		3453
3033	For example, the perl EV module uses something like this:	3454	For example, the perl EV module uses something like this:
3034		3455
3035	#define EV_COMMON \	3456	#define EV_COMMON \
3036	SV *self; /* contains this struct */ \	3457	SV *self; /* contains this struct */ \
3037	SV *cb_sv, *fh /* note no trailing ";" */	3458	SV *cb_sv, *fh /* note no trailing ";" */
3038		3459
3039	=item EV_CB_DECLARE (type)	3460	=item EV_CB_DECLARE (type)
3040		3461
3041	=item EV_CB_INVOKE (watcher, revents)	3462	=item EV_CB_INVOKE (watcher, revents)
3042		3463
…		…
3047	definition and a statement, respectively. See the F<ev.h> header file for	3468	definition and a statement, respectively. See the F<ev.h> header file for
3048	their default definitions. One possible use for overriding these is to	3469	their default definitions. One possible use for overriding these is to
3049	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3470	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3050	method calls instead of plain function calls in C++.	3471	method calls instead of plain function calls in C++.
3051		3472
		3473	=back
		3474
3052	=head2 EXPORTED API SYMBOLS	3475	=head2 EXPORTED API SYMBOLS
3053		3476
3054	If you need to re-export the API (e.g. via a dll) and you need a list of	3477	If you need to re-export the API (e.g. via a DLL) and you need a list of
3055	exported symbols, you can use the provided F<Symbol.*> files which list	3478	exported symbols, you can use the provided F<Symbol.*> files which list
3056	all public symbols, one per line:	3479	all public symbols, one per line:
3057		3480
3058	Symbols.ev for libev proper	3481	Symbols.ev for libev proper
3059	Symbols.event for the libevent emulation	3482	Symbols.event for the libevent emulation
3060		3483
3061	This can also be used to rename all public symbols to avoid clashes with	3484	This can also be used to rename all public symbols to avoid clashes with
3062	multiple versions of libev linked together (which is obviously bad in	3485	multiple versions of libev linked together (which is obviously bad in
3063	itself, but sometimes it is inconvinient to avoid this).	3486	itself, but sometimes it is inconvenient to avoid this).
3064		3487
3065	A sed command like this will create wrapper C<#define>'s that you need to	3488	A sed command like this will create wrapper C<#define>'s that you need to
3066	include before including F<ev.h>:	3489	include before including F<ev.h>:
3067		3490
3068	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3491	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3085	file.	3508	file.
3086		3509
3087	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3510	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3088	that everybody includes and which overrides some configure choices:	3511	that everybody includes and which overrides some configure choices:
3089		3512
3090	#define EV_MINIMAL 1	3513	#define EV_MINIMAL 1
3091	#define EV_USE_POLL 0	3514	#define EV_USE_POLL 0
3092	#define EV_MULTIPLICITY 0	3515	#define EV_MULTIPLICITY 0
3093	#define EV_PERIODIC_ENABLE 0	3516	#define EV_PERIODIC_ENABLE 0
3094	#define EV_STAT_ENABLE 0	3517	#define EV_STAT_ENABLE 0
3095	#define EV_FORK_ENABLE 0	3518	#define EV_FORK_ENABLE 0
3096	#define EV_CONFIG_H <config.h>	3519	#define EV_CONFIG_H <config.h>
3097	#define EV_MINPRI 0	3520	#define EV_MINPRI 0
3098	#define EV_MAXPRI 0	3521	#define EV_MAXPRI 0
3099		3522
3100	#include "ev++.h"	3523	#include "ev++.h"
3101		3524
3102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3525	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3103		3526
3104	#include "ev_cpp.h"	3527	#include "ev_cpp.h"
3105	#include "ev.c"	3528	#include "ev.c"
3106		3529
		3530	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3107		3531
3108	=head1 THREADS AND COROUTINES	3532	=head2 THREADS AND COROUTINES
3109		3533
3110	=head2 THREADS	3534	=head3 THREADS
3111		3535
3112	Libev itself is completely threadsafe, but it uses no locking. This	3536	All libev functions are reentrant and thread-safe unless explicitly
		3537	documented otherwise, but libev implements no locking itself. This means
3113	means that you can use as many loops as you want in parallel, as long as	3538	that you can use as many loops as you want in parallel, as long as there
3114	only one thread ever calls into one libev function with the same loop	3539	are no concurrent calls into any libev function with the same loop
3115	parameter.	3540	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3541	of course): libev guarantees that different event loops share no data
		3542	structures that need any locking.
3116		3543
3117	Or put differently: calls with different loop parameters can be done in	3544	Or to put it differently: calls with different loop parameters can be done
3118	parallel from multiple threads, calls with the same loop parameter must be	3545	concurrently from multiple threads, calls with the same loop parameter
3119	done serially (but can be done from different threads, as long as only one	3546	must be done serially (but can be done from different threads, as long as
3120	thread ever is inside a call at any point in time, e.g. by using a mutex	3547	only one thread ever is inside a call at any point in time, e.g. by using
3121	per loop).	3548	a mutex per loop).
3122		3549
3123	If you want to know which design is best for your problem, then I cannot	3550	Specifically to support threads (and signal handlers), libev implements
		3551	so-called C<ev_async> watchers, which allow some limited form of
		3552	concurrency on the same event loop, namely waking it up "from the
		3553	outside".
		3554
		3555	If you want to know which design (one loop, locking, or multiple loops
		3556	without or something else still) is best for your problem, then I cannot
3124	help you but by giving some generic advice:	3557	help you, but here is some generic advice:
3125		3558
3126	=over 4	3559	=over 4
3127		3560
3128	=item * most applications have a main thread: use the default libev loop	3561	=item * most applications have a main thread: use the default libev loop
3129	in that thread, or create a seperate thread running only the default loop.	3562	in that thread, or create a separate thread running only the default loop.
3130		3563
3131	This helps integrating other libraries or software modules that use libev	3564	This helps integrating other libraries or software modules that use libev
3132	themselves and don't care/know about threading.	3565	themselves and don't care/know about threading.
3133		3566
3134	=item * one loop per thread is usually a good model.	3567	=item * one loop per thread is usually a good model.
3135		3568
3136	Doing this is almost never wrong, sometimes a better-performance model	3569	Doing this is almost never wrong, sometimes a better-performance model
3137	exists, but it is always a good start.	3570	exists, but it is always a good start.
3138		3571
3139	=item * other models exist, such as the leader/follower pattern, where one	3572	=item * other models exist, such as the leader/follower pattern, where one
3140	loop is handed through multiple threads in a kind of round-robbin fashion.	3573	loop is handed through multiple threads in a kind of round-robin fashion.
3141		3574
3142	Chosing a model is hard - look around, learn, know that usually you cna do	3575	Choosing a model is hard - look around, learn, know that usually you can do
3143	better than you currently do :-)	3576	better than you currently do :-)
3144		3577
3145	=item * often you need to talk to some other thread which blocks in the	3578	=item * often you need to talk to some other thread which blocks in the
		3579	event loop.
		3580
3146	event loop - C<ev_async> watchers can be used to wake them up from other	3581	C<ev_async> watchers can be used to wake them up from other threads safely
3147	threads safely (or from signal contexts...).	3582	(or from signal contexts...).
		3583
		3584	An example use would be to communicate signals or other events that only
		3585	work in the default loop by registering the signal watcher with the
		3586	default loop and triggering an C<ev_async> watcher from the default loop
		3587	watcher callback into the event loop interested in the signal.
3148		3588
3149	=back	3589	=back
3150		3590
3151	=head2 COROUTINES	3591	=head3 COROUTINES
3152		3592
3153	Libev is much more accomodating to coroutines ("cooperative threads"):	3593	Libev is very accommodating to coroutines ("cooperative threads"):
3154	libev fully supports nesting calls to it's functions from different	3594	libev fully supports nesting calls to its functions from different
3155	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3595	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3156	different coroutines and switch freely between both coroutines running the	3596	different coroutines, and switch freely between both coroutines running the
3157	loop, as long as you don't confuse yourself). The only exception is that	3597	loop, as long as you don't confuse yourself). The only exception is that
3158	you must not do this from C<ev_periodic> reschedule callbacks.	3598	you must not do this from C<ev_periodic> reschedule callbacks.
3159		3599
3160	Care has been invested into making sure that libev does not keep local	3600	Care has been taken to ensure that libev does not keep local state inside
3161	state inside C<ev_loop>, and other calls do not usually allow coroutine	3601	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3162	switches.	3602	they do not call any callbacks.
3163		3603
		3604	=head2 COMPILER WARNINGS
3164		3605
3165	=head1 COMPLEXITIES	3606	Depending on your compiler and compiler settings, you might get no or a
		3607	lot of warnings when compiling libev code. Some people are apparently
		3608	scared by this.
3166		3609
3167	In this section the complexities of (many of) the algorithms used inside	3610	However, these are unavoidable for many reasons. For one, each compiler
3168	libev will be explained. For complexity discussions about backends see the	3611	has different warnings, and each user has different tastes regarding
3169	documentation for C<ev_default_init>.	3612	warning options. "Warn-free" code therefore cannot be a goal except when
		3613	targeting a specific compiler and compiler-version.
3170		3614
3171	All of the following are about amortised time: If an array needs to be	3615	Another reason is that some compiler warnings require elaborate
3172	extended, libev needs to realloc and move the whole array, but this	3616	workarounds, or other changes to the code that make it less clear and less
3173	happens asymptotically never with higher number of elements, so O(1) might	3617	maintainable.
3174	mean it might do a lengthy realloc operation in rare cases, but on average
3175	it is much faster and asymptotically approaches constant time.
3176		3618
3177	=over 4	3619	And of course, some compiler warnings are just plain stupid, or simply
		3620	wrong (because they don't actually warn about the condition their message
		3621	seems to warn about). For example, certain older gcc versions had some
		3622	warnings that resulted an extreme number of false positives. These have
		3623	been fixed, but some people still insist on making code warn-free with
		3624	such buggy versions.
3178		3625
3179	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3626	While libev is written to generate as few warnings as possible,
		3627	"warn-free" code is not a goal, and it is recommended not to build libev
		3628	with any compiler warnings enabled unless you are prepared to cope with
		3629	them (e.g. by ignoring them). Remember that warnings are just that:
		3630	warnings, not errors, or proof of bugs.
3180		3631
3181	This means that, when you have a watcher that triggers in one hour and
3182	there are 100 watchers that would trigger before that then inserting will
3183	have to skip roughly seven (C<ld 100>) of these watchers.
3184		3632
3185	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3633	=head2 VALGRIND
3186		3634
3187	That means that changing a timer costs less than removing/adding them	3635	Valgrind has a special section here because it is a popular tool that is
3188	as only the relative motion in the event queue has to be paid for.	3636	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3189		3637
3190	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3638	If you think you found a bug (memory leak, uninitialised data access etc.)
		3639	in libev, then check twice: If valgrind reports something like:
3191		3640
3192	These just add the watcher into an array or at the head of a list.	3641	==2274== definitely lost: 0 bytes in 0 blocks.
		3642	==2274== possibly lost: 0 bytes in 0 blocks.
		3643	==2274== still reachable: 256 bytes in 1 blocks.
3193		3644
3194	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3645	Then there is no memory leak, just as memory accounted to global variables
		3646	is not a memleak - the memory is still being referenced, and didn't leak.
3195		3647
3196	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3648	Similarly, under some circumstances, valgrind might report kernel bugs
		3649	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3650	although an acceptable workaround has been found here), or it might be
		3651	confused.
3197		3652
3198	These watchers are stored in lists then need to be walked to find the	3653	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3199	correct watcher to remove. The lists are usually short (you don't usually	3654	make it into some kind of religion.
3200	have many watchers waiting for the same fd or signal).
3201		3655
3202	=item Finding the next timer in each loop iteration: O(1)	3656	If you are unsure about something, feel free to contact the mailing list
		3657	with the full valgrind report and an explanation on why you think this
		3658	is a bug in libev (best check the archives, too :). However, don't be
		3659	annoyed when you get a brisk "this is no bug" answer and take the chance
		3660	of learning how to interpret valgrind properly.
3203		3661
3204	By virtue of using a binary or 4-heap, the next timer is always found at a	3662	If you need, for some reason, empty reports from valgrind for your project
3205	fixed position in the storage array.	3663	I suggest using suppression lists.
3206		3664
3207	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3208		3665
3209	A change means an I/O watcher gets started or stopped, which requires	3666	=head1 PORTABILITY NOTES
3210	libev to recalculate its status (and possibly tell the kernel, depending
3211	on backend and wether C<ev_io_set> was used).
3212		3667
3213	=item Activating one watcher (putting it into the pending state): O(1)	3668	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3214
3215	=item Priority handling: O(number_of_priorities)
3216
3217	Priorities are implemented by allocating some space for each
3218	priority. When doing priority-based operations, libev usually has to
3219	linearly search all the priorities, but starting/stopping and activating
3220	watchers becomes O(1) w.r.t. priority handling.
3221
3222	=item Sending an ev_async: O(1)
3223
3224	=item Processing ev_async_send: O(number_of_async_watchers)
3225
3226	=item Processing signals: O(max_signal_number)
3227
3228	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3229	calls in the current loop iteration. Checking for async and signal events
3230	involves iterating over all running async watchers or all signal numbers.
3231
3232	=back
3233
3234
3235	=head1 Win32 platform limitations and workarounds
3236		3669
3237	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3670	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3238	requires, and its I/O model is fundamentally incompatible with the POSIX	3671	requires, and its I/O model is fundamentally incompatible with the POSIX
3239	model. Libev still offers limited functionality on this platform in	3672	model. Libev still offers limited functionality on this platform in
3240	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3247	way (note also that glib is the slowest event library known to man).	3680	way (note also that glib is the slowest event library known to man).
3248		3681
3249	There is no supported compilation method available on windows except	3682	There is no supported compilation method available on windows except
3250	embedding it into other applications.	3683	embedding it into other applications.
3251		3684
		3685	Not a libev limitation but worth mentioning: windows apparently doesn't
		3686	accept large writes: instead of resulting in a partial write, windows will
		3687	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3688	so make sure you only write small amounts into your sockets (less than a
		3689	megabyte seems safe, but this apparently depends on the amount of memory
		3690	available).
		3691
3252	Due to the many, low, and arbitrary limits on the win32 platform and	3692	Due to the many, low, and arbitrary limits on the win32 platform and
3253	the abysmal performance of winsockets, using a large number of sockets	3693	the abysmal performance of winsockets, using a large number of sockets
3254	is not recommended (and not reasonable). If your program needs to use	3694	is not recommended (and not reasonable). If your program needs to use
3255	more than a hundred or so sockets, then likely it needs to use a totally	3695	more than a hundred or so sockets, then likely it needs to use a totally
3256	different implementation for windows, as libev offers the POSIX readyness	3696	different implementation for windows, as libev offers the POSIX readiness
3257	notification model, which cannot be implemented efficiently on windows	3697	notification model, which cannot be implemented efficiently on windows
3258	(microsoft monopoly games).	3698	(Microsoft monopoly games).
		3699
		3700	A typical way to use libev under windows is to embed it (see the embedding
		3701	section for details) and use the following F<evwrap.h> header file instead
		3702	of F<ev.h>:
		3703
		3704	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3705	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3706
		3707	#include "ev.h"
		3708
		3709	And compile the following F<evwrap.c> file into your project (make sure
		3710	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3711
		3712	#include "evwrap.h"
		3713	#include "ev.c"
3259		3714
3260	=over 4	3715	=over 4
3261		3716
3262	=item The winsocket select function	3717	=item The winsocket select function
3263		3718
3264	The winsocket C<select> function doesn't follow POSIX in that it requires	3719	The winsocket C<select> function doesn't follow POSIX in that it
3265	socket I<handles> and not socket I<file descriptors>. This makes select	3720	requires socket I<handles> and not socket I<file descriptors> (it is
3266	very inefficient, and also requires a mapping from file descriptors	3721	also extremely buggy). This makes select very inefficient, and also
3267	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3722	requires a mapping from file descriptors to socket handles (the Microsoft
3268	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3723	C runtime provides the function C<_open_osfhandle> for this). See the
3269	symbols for more info.	3724	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3725	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3270		3726
3271	The configuration for a "naked" win32 using the microsoft runtime	3727	The configuration for a "naked" win32 using the Microsoft runtime
3272	libraries and raw winsocket select is:	3728	libraries and raw winsocket select is:
3273		3729
3274	#define EV_USE_SELECT 1	3730	#define EV_USE_SELECT 1
3275	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3731	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3276		3732
3277	Note that winsockets handling of fd sets is O(n), so you can easily get a	3733	Note that winsockets handling of fd sets is O(n), so you can easily get a
3278	complexity in the O(n²) range when using win32.	3734	complexity in the O(n²) range when using win32.
3279		3735
3280	=item Limited number of file descriptors	3736	=item Limited number of file descriptors
3281		3737
3282	Windows has numerous arbitrary (and low) limits on things.	3738	Windows has numerous arbitrary (and low) limits on things.
3283		3739
3284	Early versions of winsocket's select only supported waiting for a maximum	3740	Early versions of winsocket's select only supported waiting for a maximum
3285	of C<64> handles (probably owning to the fact that all windows kernels	3741	of C<64> handles (probably owning to the fact that all windows kernels
3286	can only wait for C<64> things at the same time internally; microsoft	3742	can only wait for C<64> things at the same time internally; Microsoft
3287	recommends spawning a chain of threads and wait for 63 handles and the	3743	recommends spawning a chain of threads and wait for 63 handles and the
3288	previous thread in each. Great).	3744	previous thread in each. Great).
3289		3745
3290	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3746	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3291	to some high number (e.g. C<2048>) before compiling the winsocket select	3747	to some high number (e.g. C<2048>) before compiling the winsocket select
3292	call (which might be in libev or elsewhere, for example, perl does its own	3748	call (which might be in libev or elsewhere, for example, perl does its own
3293	select emulation on windows).	3749	select emulation on windows).
3294		3750
3295	Another limit is the number of file descriptors in the microsoft runtime	3751	Another limit is the number of file descriptors in the Microsoft runtime
3296	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3752	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3297	or something like this inside microsoft). You can increase this by calling	3753	or something like this inside Microsoft). You can increase this by calling
3298	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3754	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3299	arbitrary limit), but is broken in many versions of the microsoft runtime	3755	arbitrary limit), but is broken in many versions of the Microsoft runtime
3300	libraries.	3756	libraries.
3301		3757
3302	This might get you to about C<512> or C<2048> sockets (depending on	3758	This might get you to about C<512> or C<2048> sockets (depending on
3303	windows version and/or the phase of the moon). To get more, you need to	3759	windows version and/or the phase of the moon). To get more, you need to
3304	wrap all I/O functions and provide your own fd management, but the cost of	3760	wrap all I/O functions and provide your own fd management, but the cost of
3305	calling select (O(n²)) will likely make this unworkable.	3761	calling select (O(n²)) will likely make this unworkable.
3306		3762
3307	=back	3763	=back
3308		3764
3309
3310	=head1 PORTABILITY REQUIREMENTS	3765	=head2 PORTABILITY REQUIREMENTS
3311		3766
3312	In addition to a working ISO-C implementation, libev relies on a few	3767	In addition to a working ISO-C implementation and of course the
3313	additional extensions:	3768	backend-specific APIs, libev relies on a few additional extensions:
3314		3769
3315	=over 4	3770	=over 4
3316		3771
		3772	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3773	calling conventions regardless of C<ev_watcher_type *>.
		3774
		3775	Libev assumes not only that all watcher pointers have the same internal
		3776	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3777	assumes that the same (machine) code can be used to call any watcher
		3778	callback: The watcher callbacks have different type signatures, but libev
		3779	calls them using an C<ev_watcher *> internally.
		3780
3317	=item C<sig_atomic_t volatile> must be thread-atomic as well	3781	=item C<sig_atomic_t volatile> must be thread-atomic as well
3318		3782
3319	The type C<sig_atomic_t volatile> (or whatever is defined as	3783	The type C<sig_atomic_t volatile> (or whatever is defined as
3320	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3784	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3321	threads. This is not part of the specification for C<sig_atomic_t>, but is	3785	threads. This is not part of the specification for C<sig_atomic_t>, but is
3322	believed to be sufficiently portable.	3786	believed to be sufficiently portable.
3323		3787
3324	=item C<sigprocmask> must work in a threaded environment	3788	=item C<sigprocmask> must work in a threaded environment
3325		3789
…		…
3334	except the initial one, and run the default loop in the initial thread as	3798	except the initial one, and run the default loop in the initial thread as
3335	well.	3799	well.
3336		3800
3337	=item C<long> must be large enough for common memory allocation sizes	3801	=item C<long> must be large enough for common memory allocation sizes
3338		3802
3339	To improve portability and simplify using libev, libev uses C<long>	3803	To improve portability and simplify its API, libev uses C<long> internally
3340	internally instead of C<size_t> when allocating its data structures. On	3804	instead of C<size_t> when allocating its data structures. On non-POSIX
3341	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3805	systems (Microsoft...) this might be unexpectedly low, but is still at
3342	is still at least 31 bits everywhere, which is enough for hundreds of	3806	least 31 bits everywhere, which is enough for hundreds of millions of
3343	millions of watchers.	3807	watchers.
3344		3808
3345	=item C<double> must hold a time value in seconds with enough accuracy	3809	=item C<double> must hold a time value in seconds with enough accuracy
3346		3810
3347	The type C<double> is used to represent timestamps. It is required to	3811	The type C<double> is used to represent timestamps. It is required to
3348	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3812	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3352	=back	3816	=back
3353		3817
3354	If you know of other additional requirements drop me a note.	3818	If you know of other additional requirements drop me a note.
3355		3819
3356		3820
		3821	=head1 ALGORITHMIC COMPLEXITIES
		3822
		3823	In this section the complexities of (many of) the algorithms used inside
		3824	libev will be documented. For complexity discussions about backends see
		3825	the documentation for C<ev_default_init>.
		3826
		3827	All of the following are about amortised time: If an array needs to be
		3828	extended, libev needs to realloc and move the whole array, but this
		3829	happens asymptotically rarer with higher number of elements, so O(1) might
		3830	mean that libev does a lengthy realloc operation in rare cases, but on
		3831	average it is much faster and asymptotically approaches constant time.
		3832
		3833	=over 4
		3834
		3835	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3836
		3837	This means that, when you have a watcher that triggers in one hour and
		3838	there are 100 watchers that would trigger before that, then inserting will
		3839	have to skip roughly seven (C<ld 100>) of these watchers.
		3840
		3841	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3842
		3843	That means that changing a timer costs less than removing/adding them,
		3844	as only the relative motion in the event queue has to be paid for.
		3845
		3846	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3847
		3848	These just add the watcher into an array or at the head of a list.
		3849
		3850	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3851
		3852	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3853
		3854	These watchers are stored in lists, so they need to be walked to find the
		3855	correct watcher to remove. The lists are usually short (you don't usually
		3856	have many watchers waiting for the same fd or signal: one is typical, two
		3857	is rare).
		3858
		3859	=item Finding the next timer in each loop iteration: O(1)
		3860
		3861	By virtue of using a binary or 4-heap, the next timer is always found at a
		3862	fixed position in the storage array.
		3863
		3864	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3865
		3866	A change means an I/O watcher gets started or stopped, which requires
		3867	libev to recalculate its status (and possibly tell the kernel, depending
		3868	on backend and whether C<ev_io_set> was used).
		3869
		3870	=item Activating one watcher (putting it into the pending state): O(1)
		3871
		3872	=item Priority handling: O(number_of_priorities)
		3873
		3874	Priorities are implemented by allocating some space for each
		3875	priority. When doing priority-based operations, libev usually has to
		3876	linearly search all the priorities, but starting/stopping and activating
		3877	watchers becomes O(1) with respect to priority handling.
		3878
		3879	=item Sending an ev_async: O(1)
		3880
		3881	=item Processing ev_async_send: O(number_of_async_watchers)
		3882
		3883	=item Processing signals: O(max_signal_number)
		3884
		3885	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3886	calls in the current loop iteration. Checking for async and signal events
		3887	involves iterating over all running async watchers or all signal numbers.
		3888
		3889	=back
		3890
		3891
3357	=head1 AUTHOR	3892	=head1 AUTHOR
3358		3893
3359	Marc Lehmann <libev@schmorp.de>.	3894	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3360		3895

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