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Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs.
Revision 1.211 by root, Mon Nov 3 14:34:16 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
…		…
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	readiness 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
376	While nominally embeddeble in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	424	all kernel versions tested so far.
		425
		426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		427	C<EVBACKEND_POLL>.
378		428
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		430
381	Kqueue deserves special mention, as at the time of this writing, it	431	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	432	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	433	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"	434	it's completely useless). Unlike epoll, however, whose brokenness
		435	is by design, these kqueue bugs can (and eventually will) be fixed
		436	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	437	"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)	438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	439	system like NetBSD.
388		440
389	You still can embed kqueue into a normal poll or select backend and use it	441	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	442	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.	443	the target platform). See C<ev_embed> watchers for more info.
392		444
393	It scales in the same way as the epoll backend, but the interface to the	445	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	446	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	447	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	448	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	449	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
399		452
400	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
401		454
402	While nominally embeddable in other event loops, this doesn't work	455	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	456	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	457	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	458	(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	459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	460	using it only for sockets.
		461
		462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		464	C<NOTE_EOF>.
408		465
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	466	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		467
411	This is not implemented yet (and might never be, unless you send me an	468	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	469	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	473	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		474
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	475	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)).	476	it's really slow, but it still scales very well (O(active_fds)).
420		477
421	Please note that solaris event ports can deliver a lot of spurious	478	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	479	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	480	blocking when no data (or space) is available.
424		481
425	While this backend scales well, it requires one system call per active	482	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	483	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	485	might perform better.
429		486
430	On the positive side, ignoring the spurious readiness notifications, this	487	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	488	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	489	in all tests and is fully embeddable, which is a rare feat among the
		490	OS-specific backends (I vastly prefer correctness over speed hacks).
		491
		492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		493	C<EVBACKEND_POLL>.
433		494
434	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
435		496
436	Try all backends (even potentially broken ones that wouldn't be tried	497	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	498	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		500
440	It is definitely not recommended to use this flag.	501	It is definitely not recommended to use this flag.
441		502
442	=back	503	=back
443		504
444	If one or more of these are ored into the flags value, then only these	505	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	506	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.	507	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		508
448	The most typical usage is like this:	509	Example: This is the most typical usage.
449		510
450	if (!ev_default_loop (0))	511	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		513
453	Restrict libev to the select and poll backends, and do not allow	514	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	515	environment settings to be taken into account:
455		516
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		518
458	Use whatever libev has to offer, but make sure that kqueue is used if	519	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	520	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):	521	private event loop and only if you know the OS supports your types of
		522	fds):
461		523
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		525
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	526	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		527
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	528	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	529	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	534	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	535	default loop in the "main" or "initial" thread.
474		536
475	Example: Try to create a event loop that uses epoll and nothing else.	537	Example: Try to create a event loop that uses epoll and nothing else.
476		538
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	540	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	541	fatal ("no epoll found here, maybe it hides under your chair");
480		542
481	=item ev_default_destroy ()	543	=item ev_default_destroy ()
482		544
483	Destroys the default loop again (frees all memory and kernel state	545	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	546	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	547	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>	548	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	549	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	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	551	for example).
490		552
491	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
494		556
495	In general it is not advisable to call this function except in the	557	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	558	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	559	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		585
524	=item ev_loop_fork (loop)	586	=item ev_loop_fork (loop)
525		587
526	Like C<ev_default_fork>, but acts on an event loop created by	588	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	589	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.	590	after fork that you want to re-use in the child, and how you do this is
		591	entirely your own problem.
529		592
530	=item int ev_is_default_loop (loop)	593	=item int ev_is_default_loop (loop)
531		594
532	Returns true when the given loop actually is the default loop, false otherwise.	595	Returns true when the given loop is, in fact, the default loop, and false
		596	otherwise.
533		597
534	=item unsigned int ev_loop_count (loop)	598	=item unsigned int ev_loop_count (loop)
535		599
536	Returns the count of loop iterations for the loop, which is identical to	600	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	601	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	616	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	617	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	618	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).	619	event occurring (or more correctly, libev finding out about it).
556		620
		621	=item ev_now_update (loop)
		622
		623	Establishes the current time by querying the kernel, updating the time
		624	returned by C<ev_now ()> in the progress. This is a costly operation and
		625	is usually done automatically within C<ev_loop ()>.
		626
		627	This function is rarely useful, but when some event callback runs for a
		628	very long time without entering the event loop, updating libev's idea of
		629	the current time is a good idea.
		630
		631	See also "The special problem of time updates" in the C<ev_timer> section.
		632
557	=item ev_loop (loop, int flags)	633	=item ev_loop (loop, int flags)
558		634
559	Finally, this is it, the event handler. This function usually is called	635	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	636	after you initialised all your watchers and you want to start handling
561	events.	637	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	639	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.	640	either no event watchers are active anymore or C<ev_unloop> was called.
565		641
566	Please note that an explicit C<ev_unloop> is usually better than	642	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	643	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	644	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	645	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.	646	of relying on its watchers stopping correctly, that is truly a thing of
		647	beauty.
571		648
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	649	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	650	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.	651	process in case there are no events and will return after one iteration of
		652	the loop.
575		653
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	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	655	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	656	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	657	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	658	user-registered callback will be called), and will return after one
		659	iteration of the loop.
		660
		661	This is useful if you are waiting for some external event in conjunction
		662	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	663	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.	664	usually a better approach for this kind of thing.
583		665
584	Here are the gory details of what C<ev_loop> does:	666	Here are the gory details of what C<ev_loop> does:
585		667
586	- Before the first iteration, call any pending watchers.	668	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	669	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	670	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	671	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	672	- If we have been forked, detach and recreate the kernel state
		673	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	674	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	675	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	676	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	677	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	678	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	679	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	680	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	681	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	683	- Queue all expired timers.
601	- Queue all outstanding periodics.	684	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	685	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	686	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	687	- 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	688	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	689	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	690	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	695	anymore.
613		696
614	... queue jobs here, make sure they register event watchers as long	697	... 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..)	698	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	699	ev_loop (my_loop, 0);
617	... jobs done. yeah!	700	... jobs done or somebody called unloop. yeah!
618		701
619	=item ev_unloop (loop, how)	702	=item ev_unloop (loop, how)
620		703
621	Can be used to make a call to C<ev_loop> return early (but only after it	704	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	705	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	706	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.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		708
626	This "unloop state" will be cleared when entering C<ev_loop> again.	709	This "unloop state" will be cleared when entering C<ev_loop> again.
627		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
628	=item ev_ref (loop)	713	=item ev_ref (loop)
629		714
630	=item ev_unref (loop)	715	=item ev_unref (loop)
631		716
632	Ref/unref can be used to add or remove a reference count on the event	717	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	718	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	719	count is nonzero, C<ev_loop> will not return on its own.
		720
635	a watcher you never unregister that should not keep C<ev_loop> from	721	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	722	from returning, call ev_unref() after starting, and ev_ref() before
		723	stopping it.
		724
637	example, libev itself uses this for its internal signal pipe: It is not	725	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	726	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	727	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	728	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>	729	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,	730	(but only if the watcher wasn't active before, or was active before,
643	respectively).	731	respectively).
644		732
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	734	running when nothing else is active.
647		735
648	struct ev_signal exitsig;	736	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	739	evf_unref (loop);
652		740
653	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
654		742
655	ev_ref (loop);	743	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	744	ev_signal_stop (loop, &exitsig);
657		745
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	746	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		747
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	748	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		749
662	These advanced functions influence the time that libev will spend waiting	750	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	751	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.	752	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		753	latency.
665		754
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	755	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	756	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	757	to increase efficiency of loop iterations (or to increase power-saving
		758	opportunities).
669		759
670	The background is that sometimes your program runs just fast enough to	760	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	761	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	762	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	763	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	764	overhead for the actual polling but can deliver many events at once.
675		765
676	By setting a higher I<io collect interval> you allow libev to spend more	766	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,	767	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	769	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.	770	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		771
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	772	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	773	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	774	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	775	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	776	value will not introduce any overhead in libev.
687		777
688	Many (busy) programs can usually benefit by setting the io collect	778	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	779	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	780	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>,	781	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.	782	as this approaches the timing granularity of most systems.
		783
		784	Setting the I<timeout collect interval> can improve the opportunity for
		785	saving power, as the program will "bundle" timer callback invocations that
		786	are "near" in time together, by delaying some, thus reducing the number of
		787	times the process sleeps and wakes up again. Another useful technique to
		788	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		789	they fire on, say, one-second boundaries only.
693		790
694	=item ev_loop_verify (loop)	791	=item ev_loop_verify (loop)
695		792
696	This function only does something when C<EV_VERIFY> support has been	793	This function only does something when C<EV_VERIFY> support has been
697	compiled in. It tries to go through all internal structures and checks	794	compiled in, which is the default for non-minimal builds. It tries to go
698	them for validity. If anything is found to be inconsistent, it will print	795	through all internal structures and checks them for validity. If anything
699	an error message to standard error and call C<abort ()>.	796	is found to be inconsistent, it will print an error message to standard
		797	error and call C<abort ()>.
700		798
701	This can be used to catch bugs inside libev itself: under normal	799	This can be used to catch bugs inside libev itself: under normal
702	circumstances, this function will never abort as of course libev keeps its	800	circumstances, this function will never abort as of course libev keeps its
703	data structures consistent.	801	data structures consistent.
704		802
705	=back	803	=back
706		804
707		805
708	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
709		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
		811
710	A watcher is a structure that you create and register to record your	812	A watcher is a structure that you create and register to record your
711	interest in some event. For instance, if you want to wait for STDIN to	813	interest in some event. For instance, if you want to wait for STDIN to
712	become readable, you would create an C<ev_io> watcher for that:	814	become readable, you would create an C<ev_io> watcher for that:
713		815
714	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
715	{	817	{
716	ev_io_stop (w);	818	ev_io_stop (w);
717	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
718	}	820	}
719		821
720	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
721	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
722	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
723	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
724	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
725	ev_loop (loop, 0);	830	ev_loop (loop, 0);
726		831
727	As you can see, you are responsible for allocating the memory for your	832	As you can see, you are responsible for allocating the memory for your
728	watcher structures (and it is usually a bad idea to do this on the stack,	833	watcher structures (and it is I<usually> a bad idea to do this on the
729	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
730		838
731	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
732	(watcher *, callback)>, which expects a callback to be provided. This	840	(watcher *, callback)>, which expects a callback to be provided. This
733	callback gets invoked each time the event occurs (or, in the case of io	841	callback gets invoked each time the event occurs (or, in the case of I/O
734	watchers, each time the event loop detects that the file descriptor given	842	watchers, each time the event loop detects that the file descriptor given
735	is readable and/or writable).	843	is readable and/or writable).
736		844
737	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
738	with arguments specific to this watcher type. There is also a macro	846	macro to configure it, with arguments specific to the watcher type. There
739	to combine initialisation and setting in one call: C<< ev_<type>_init	847	is also a macro to combine initialisation and setting in one call: C<<
740	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
741		849
742	To make the watcher actually watch out for events, you have to start it	850	To make the watcher actually watch out for events, you have to start it
743	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	851	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
744	*) >>), and you can stop watching for events at any time by calling the	852	*) >>), and you can stop watching for events at any time by calling the
745	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
746		854
747	As long as your watcher is active (has been started but not stopped) you	855	As long as your watcher is active (has been started but not stopped) you
748	must not touch the values stored in it. Most specifically you must never	856	must not touch the values stored in it. Most specifically you must never
749	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
750		858
751	Each and every callback receives the event loop pointer as first, the	859	Each and every callback receives the event loop pointer as first, the
752	registered watcher structure as second, and a bitset of received events as	860	registered watcher structure as second, and a bitset of received events as
753	third argument.	861	third argument.
754		862
…		…
814		922
815	The given async watcher has been asynchronously notified (see C<ev_async>).	923	The given async watcher has been asynchronously notified (see C<ev_async>).
816		924
817	=item C<EV_ERROR>	925	=item C<EV_ERROR>
818		926
819	An unspecified error has occured, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
820	happen because the watcher could not be properly started because libev	928	happen because the watcher could not be properly started because libev
821	ran out of memory, a file descriptor was found to be closed or any other	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
822	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
823	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
824		936
825	Libev will usually signal a few "dummy" events together with an error,	937	Libev will usually signal a few "dummy" events together with an error, for
826	for example it might indicate that a fd is readable or writable, and if	938	example it might indicate that a fd is readable or writable, and if your
827	your callbacks is well-written it can just attempt the operation and cope	939	callbacks is well-written it can just attempt the operation and cope with
828	with the error from read() or write(). This will not work in multithreaded	940	the error from read() or write(). This will not work in multi-threaded
829	programs, though, so beware.	941	programs, though, as the fd could already be closed and reused for another
		942	thing, so beware.
830		943
831	=back	944	=back
832		945
833	=head2 GENERIC WATCHER FUNCTIONS	946	=head2 GENERIC WATCHER FUNCTIONS
834
835	In the following description, C<TYPE> stands for the watcher type,
836	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
837		947
838	=over 4	948	=over 4
839		949
840	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
841		951
…		…
847	which rolls both calls into one.	957	which rolls both calls into one.
848		958
849	You can reinitialise a watcher at any time as long as it has been stopped	959	You can reinitialise a watcher at any time as long as it has been stopped
850	(or never started) and there are no pending events outstanding.	960	(or never started) and there are no pending events outstanding.
851		961
852	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
853	int revents)>.	963	int revents)>.
		964
		965	Example: Initialise an C<ev_io> watcher in two steps.
		966
		967	ev_io w;
		968	ev_init (&w, my_cb);
		969	ev_io_set (&w, STDIN_FILENO, EV_READ);
854		970
855	=item C<ev_TYPE_set> (ev_TYPE *, [args])	971	=item C<ev_TYPE_set> (ev_TYPE *, [args])
856		972
857	This macro initialises the type-specific parts of a watcher. You need to	973	This macro initialises the type-specific parts of a watcher. You need to
858	call C<ev_init> at least once before you call this macro, but you can	974	call C<ev_init> at least once before you call this macro, but you can
…		…
861	difference to the C<ev_init> macro).	977	difference to the C<ev_init> macro).
862		978
863	Although some watcher types do not have type-specific arguments	979	Although some watcher types do not have type-specific arguments
864	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	980	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
865		981
		982	See C<ev_init>, above, for an example.
		983
866	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	984	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
867		985
868	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	986	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
869	calls into a single call. This is the most convinient method to initialise	987	calls into a single call. This is the most convenient method to initialise
870	a watcher. The same limitations apply, of course.	988	a watcher. The same limitations apply, of course.
		989
		990	Example: Initialise and set an C<ev_io> watcher in one step.
		991
		992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
871		993
872	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
873		995
874	Starts (activates) the given watcher. Only active watchers will receive	996	Starts (activates) the given watcher. Only active watchers will receive
875	events. If the watcher is already active nothing will happen.	997	events. If the watcher is already active nothing will happen.
876		998
		999	Example: Start the C<ev_io> watcher that is being abused as example in this
		1000	whole section.
		1001
		1002	ev_io_start (EV_DEFAULT_UC, &w);
		1003
877	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
878		1005
879	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
880	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
881	non-repeating timers are being stopped when they become pending), but	1010	non-repeating timers are being stopped when they become pending - but
882	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1011	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
883	you want to free or reuse the memory used by the watcher it is therefore a	1012	pending. If you want to free or reuse the memory used by the watcher it is
884	good idea to always call its C<ev_TYPE_stop> function.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
885		1014
886	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
887		1016
888	Returns a true value iff the watcher is active (i.e. it has been started	1017	Returns a true value iff the watcher is active (i.e. it has been started
889	and not yet been stopped). As long as a watcher is active you must not modify	1018	and not yet been stopped). As long as a watcher is active you must not modify
…		…
931	The default priority used by watchers when no priority has been set is	1060	The default priority used by watchers when no priority has been set is
932	always C<0>, which is supposed to not be too high and not be too low :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
933		1062
934	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
935	fine, as long as you do not mind that the priority value you query might	1064	fine, as long as you do not mind that the priority value you query might
936	or might not have been adjusted to be within valid range.	1065	or might not have been clamped to the valid range.
937		1066
938	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
939		1068
940	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
941	C<loop> nor C<revents> need to be valid as long as the watcher callback	1070	C<loop> nor C<revents> need to be valid as long as the watcher callback
942	can deal with that fact.	1071	can deal with that fact, as both are simply passed through to the
		1072	callback.
943		1073
944	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1074	=item int ev_clear_pending (loop, ev_TYPE *watcher)
945		1075
946	If the watcher is pending, this function returns clears its pending status	1076	If the watcher is pending, this function clears its pending status and
947	and returns its C<revents> bitset (as if its callback was invoked). If the	1077	returns its C<revents> bitset (as if its callback was invoked). If the
948	watcher isn't pending it does nothing and returns C<0>.	1078	watcher isn't pending it does nothing and returns C<0>.
949		1079
		1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1081	callback to be invoked, which can be accomplished with this function.
		1082
950	=back	1083	=back
951		1084
952		1085
953	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
954		1087
955	Each watcher has, by default, a member C<void *data> that you can change	1088	Each watcher has, by default, a member C<void *data> that you can change
956	and read at any time, libev will completely ignore it. This can be used	1089	and read at any time: libev will completely ignore it. This can be used
957	to associate arbitrary data with your watcher. If you need more data and	1090	to associate arbitrary data with your watcher. If you need more data and
958	don't want to allocate memory and store a pointer to it in that data	1091	don't want to allocate memory and store a pointer to it in that data
959	member, you can also "subclass" the watcher type and provide your own	1092	member, you can also "subclass" the watcher type and provide your own
960	data:	1093	data:
961		1094
962	struct my_io	1095	struct my_io
963	{	1096	{
964	struct ev_io io;	1097	ev_io io;
965	int otherfd;	1098	int otherfd;
966	void *somedata;	1099	void *somedata;
967	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
968	}	1101	};
		1102
		1103	...
		1104	struct my_io w;
		1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
969		1106
970	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
971	can cast it back to your own type:	1108	can cast it back to your own type:
972		1109
973	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
974	{	1111	{
975	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
976	...	1113	...
977	}	1114	}
978		1115
979	More interesting and less C-conformant ways of casting your callback type	1116	More interesting and less C-conformant ways of casting your callback type
980	instead have been omitted.	1117	instead have been omitted.
981		1118
982	Another common scenario is having some data structure with multiple	1119	Another common scenario is to use some data structure with multiple
983	watchers:	1120	embedded watchers:
984		1121
985	struct my_biggy	1122	struct my_biggy
986	{	1123	{
987	int some_data;	1124	int some_data;
988	ev_timer t1;	1125	ev_timer t1;
989	ev_timer t2;	1126	ev_timer t2;
990	}	1127	}
991		1128
992	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1129	In this case getting the pointer to C<my_biggy> is a bit more
993	you need to use C<offsetof>:	1130	complicated: Either you store the address of your C<my_biggy> struct
		1131	in the C<data> member of the watcher (for woozies), or you need to use
		1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
994		1134
995	#include <stddef.h>	1135	#include <stddef.h>
996		1136
997	static void	1137	static void
998	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
999	{	1139	{
1000	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
1001	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
1002	}	1142	}
1003		1143
1004	static void	1144	static void
1005	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
1006	{	1146	{
1007	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
1008	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
1009	}	1149	}
1010		1150
1011		1151
1012	=head1 WATCHER TYPES	1152	=head1 WATCHER TYPES
1013		1153
1014	This section describes each watcher in detail, but will not repeat	1154	This section describes each watcher in detail, but will not repeat
…		…
1038	In general you can register as many read and/or write event watchers per	1178	In general you can register as many read and/or write event watchers per
1039	fd as you want (as long as you don't confuse yourself). Setting all file	1179	fd as you want (as long as you don't confuse yourself). Setting all file
1040	descriptors to non-blocking mode is also usually a good idea (but not	1180	descriptors to non-blocking mode is also usually a good idea (but not
1041	required if you know what you are doing).	1181	required if you know what you are doing).
1042		1182
1043	If you must do this, then force the use of a known-to-be-good backend	1183	If you cannot use non-blocking mode, then force the use of a
1044	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1184	known-to-be-good backend (at the time of this writing, this includes only
1045	C<EVBACKEND_POLL>).	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1046		1186
1047	Another thing you have to watch out for is that it is quite easy to	1187	Another thing you have to watch out for is that it is quite easy to
1048	receive "spurious" readiness notifications, that is your callback might	1188	receive "spurious" readiness notifications, that is your callback might
1049	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1189	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1050	because there is no data. Not only are some backends known to create a	1190	because there is no data. Not only are some backends known to create a
1051	lot of those (for example solaris ports), it is very easy to get into	1191	lot of those (for example Solaris ports), it is very easy to get into
1052	this situation even with a relatively standard program structure. Thus	1192	this situation even with a relatively standard program structure. Thus
1053	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1193	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1054	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1055		1195
1056	If you cannot run the fd in non-blocking mode (for example you should not	1196	If you cannot run the fd in non-blocking mode (for example you should
1057	play around with an Xlib connection), then you have to seperately re-test	1197	not play around with an Xlib connection), then you have to separately
1058	whether a file descriptor is really ready with a known-to-be good interface	1198	re-test whether a file descriptor is really ready with a known-to-be good
1059	such as poll (fortunately in our Xlib example, Xlib already does this on	1199	interface such as poll (fortunately in our Xlib example, Xlib already
1060	its own, so its quite safe to use).	1200	does this on its own, so its quite safe to use). Some people additionally
		1201	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1202	indefinitely.
		1203
		1204	But really, best use non-blocking mode.
1061		1205
1062	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1063		1207
1064	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1208	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1065	descriptor (either by calling C<close> explicitly or by any other means,	1209	descriptor (either due to calling C<close> explicitly or any other means,
1066	such as C<dup>). The reason is that you register interest in some file	1210	such as C<dup2>). The reason is that you register interest in some file
1067	descriptor, but when it goes away, the operating system will silently drop	1211	descriptor, but when it goes away, the operating system will silently drop
1068	this interest. If another file descriptor with the same number then is	1212	this interest. If another file descriptor with the same number then is
1069	registered with libev, there is no efficient way to see that this is, in	1213	registered with libev, there is no efficient way to see that this is, in
1070	fact, a different file descriptor.	1214	fact, a different file descriptor.
1071		1215
…		…
1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1103	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1104		1248
1105	=head3 The special problem of SIGPIPE	1249	=head3 The special problem of SIGPIPE
1106		1250
1107	While not really specific to libev, it is easy to forget about SIGPIPE:	1251	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1108	when reading from a pipe whose other end has been closed, your program	1252	when writing to a pipe whose other end has been closed, your program gets
1109	gets send a SIGPIPE, which, by default, aborts your program. For most	1253	sent a SIGPIPE, which, by default, aborts your program. For most programs
1110	programs this is sensible behaviour, for daemons, this is usually	1254	this is sensible behaviour, for daemons, this is usually undesirable.
1111	undesirable.
1112		1255
1113	So when you encounter spurious, unexplained daemon exits, make sure you	1256	So when you encounter spurious, unexplained daemon exits, make sure you
1114	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1257	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1115	somewhere, as that would have given you a big clue).	1258	somewhere, as that would have given you a big clue).
1116		1259
…		…
1122	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1123		1266
1124	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1125		1268
1126	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1269	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1127	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1270	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1128	C<EV_READ | EV_WRITE> to receive the given events.	1271	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1129		1272
1130	=item int fd [read-only]	1273	=item int fd [read-only]
1131		1274
1132	The file descriptor being watched.	1275	The file descriptor being watched.
1133		1276
…		…
1141		1284
1142	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1143	readable, but only once. Since it is likely line-buffered, you could	1286	readable, but only once. Since it is likely line-buffered, you could
1144	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1145		1288
1146	static void	1289	static void
1147	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1148	{	1291	{
1149	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1150	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1151	}	1294	}
1152		1295
1153	...	1296	...
1154	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1155	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1156	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1157	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1158	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1159		1302
1160		1303
1161	=head2 C<ev_timer> - relative and optionally repeating timeouts	1304	=head2 C<ev_timer> - relative and optionally repeating timeouts
1162		1305
1163	Timer watchers are simple relative timers that generate an event after a	1306	Timer watchers are simple relative timers that generate an event after a
1164	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1165		1308
1166	The timers are based on real time, that is, if you register an event that	1309	The timers are based on real time, that is, if you register an event that
1167	times out after an hour and you reset your system clock to january last	1310	times out after an hour and you reset your system clock to January last
1168	year, it will still time out after (roughly) and hour. "Roughly" because	1311	year, it will still time out after (roughly) one hour. "Roughly" because
1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1170	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
		1314
		1315	The callback is guaranteed to be invoked only I<after> its timeout has
		1316	passed, but if multiple timers become ready during the same loop iteration
		1317	then order of execution is undefined.
		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
		1493
		1494	=head3 The special problem of time updates
		1495
		1496	Establishing the current time is a costly operation (it usually takes at
		1497	least two system calls): EV therefore updates its idea of the current
		1498	time only before and after C<ev_loop> collects new events, which causes a
		1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1500	lots of events in one iteration.
1171		1501
1172	The relative timeouts are calculated relative to the C<ev_now ()>	1502	The relative timeouts are calculated relative to the C<ev_now ()>
1173	time. This is usually the right thing as this timestamp refers to the time	1503	time. This is usually the right thing as this timestamp refers to the time
1174	of the event triggering whatever timeout you are modifying/starting. If	1504	of the event triggering whatever timeout you are modifying/starting. If
1175	you suspect event processing to be delayed and you I<need> to base the timeout	1505	you suspect event processing to be delayed and you I<need> to base the
1176	on the current time, use something like this to adjust for this:	1506	timeout on the current time, use something like this to adjust for this:
1177		1507
1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1508	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1179		1509
1180	The callback is guarenteed to be invoked only after its timeout has passed,	1510	If the event loop is suspended for a long time, you can also force an
1181	but if multiple timers become ready during the same loop iteration then	1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1182	order of execution is undefined.	1512	()>.
1183		1513
1184	=head3 Watcher-Specific Functions and Data Members	1514	=head3 Watcher-Specific Functions and Data Members
1185		1515
1186	=over 4	1516	=over 4
1187		1517
…		…
1206	This will act as if the timer timed out and restart it again if it is	1536	This will act as if the timer timed out and restart it again if it is
1207	repeating. The exact semantics are:	1537	repeating. The exact semantics are:
1208		1538
1209	If the timer is pending, its pending status is cleared.	1539	If the timer is pending, its pending status is cleared.
1210		1540
1211	If the timer is started but nonrepeating, stop it (as if it timed out).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1212		1542
1213	If the timer is repeating, either start it if necessary (with the	1543	If the timer is repeating, either start it if necessary (with the
1214	C<repeat> value), or reset the running timer to the C<repeat> value.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1215		1545
1216	This sounds a bit complicated, but here is a useful and typical	1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1217	example: Imagine you have a tcp connection and you want a so-called idle	1547	usage example.
1218	timeout, that is, you want to be called when there have been, say, 60
1219	seconds of inactivity on the socket. The easiest way to do this is to
1220	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1221	C<ev_timer_again> each time you successfully read or write some data. If
1222	you go into an idle state where you do not expect data to travel on the
1223	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1224	automatically restart it if need be.
1225
1226	That means you can ignore the C<after> value and C<ev_timer_start>
1227	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1228
1229	ev_timer_init (timer, callback, 0., 5.);
1230	ev_timer_again (loop, timer);
1231	...
1232	timer->again = 17.;
1233	ev_timer_again (loop, timer);
1234	...
1235	timer->again = 10.;
1236	ev_timer_again (loop, timer);
1237
1238	This is more slightly efficient then stopping/starting the timer each time
1239	you want to modify its timeout value.
1240		1548
1241	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1242		1550
1243	The current C<repeat> value. Will be used each time the watcher times out	1551	The current C<repeat> value. Will be used each time the watcher times out
1244	or C<ev_timer_again> is called and determines the next timeout (if any),	1552	or C<ev_timer_again> is called, and determines the next timeout (if any),
1245	which is also when any modifications are taken into account.	1553	which is also when any modifications are taken into account.
1246		1554
1247	=back	1555	=back
1248		1556
1249	=head3 Examples	1557	=head3 Examples
1250		1558
1251	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1252		1560
1253	static void	1561	static void
1254	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1255	{	1563	{
1256	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1257	}	1565	}
1258		1566
1259	struct ev_timer mytimer;	1567	ev_timer mytimer;
1260	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1261	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1262		1570
1263	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1264	inactivity.	1572	inactivity.
1265		1573
1266	static void	1574	static void
1267	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1268	{	1576	{
1269	.. ten seconds without any activity	1577	.. ten seconds without any activity
1270	}	1578	}
1271		1579
1272	struct ev_timer mytimer;	1580	ev_timer mytimer;
1273	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1274	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1275	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1276		1584
1277	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
1278	// reset the timeout to start ticking again at 10 seconds	1586	// reset the timeout to start ticking again at 10 seconds
1279	ev_timer_again (&mytimer);	1587	ev_timer_again (&mytimer);
1280		1588
1281		1589
1282	=head2 C<ev_periodic> - to cron or not to cron?	1590	=head2 C<ev_periodic> - to cron or not to cron?
1283		1591
1284	Periodic watchers are also timers of a kind, but they are very versatile	1592	Periodic watchers are also timers of a kind, but they are very versatile
1285	(and unfortunately a bit complex).	1593	(and unfortunately a bit complex).
1286		1594
1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1595	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1288	but on wallclock time (absolute time). You can tell a periodic watcher	1596	but on wall clock time (absolute time). You can tell a periodic watcher
1289	to trigger after some specific point in time. For example, if you tell a	1597	to trigger after some specific point in time. For example, if you tell a
1290	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1598	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1291	+ 10.>, that is, an absolute time not a delay) and then reset your system	1599	+ 10.>, that is, an absolute time not a delay) and then reset your system
1292	clock to january of the previous year, then it will take more than year	1600	clock to January of the previous year, then it will take more than year
1293	to trigger the event (unlike an C<ev_timer>, which would still trigger	1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1294	roughly 10 seconds later as it uses a relative timeout).	1602	roughly 10 seconds later as it uses a relative timeout).
1295		1603
1296	C<ev_periodic>s can also be used to implement vastly more complex timers,	1604	C<ev_periodic>s can also be used to implement vastly more complex timers,
1297	such as triggering an event on each "midnight, local time", or other	1605	such as triggering an event on each "midnight, local time", or other
1298	complicated, rules.	1606	complicated rules.
1299		1607
1300	As with timers, the callback is guarenteed to be invoked only when the	1608	As with timers, the callback is guaranteed to be invoked only when the
1301	time (C<at>) has passed, but if multiple periodic timers become ready	1609	time (C<at>) has passed, but if multiple periodic timers become ready
1302	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1303		1611
1304	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1305		1613
1306	=over 4	1614	=over 4
1307		1615
1308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1309		1617
1310	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1311		1619
1312	Lots of arguments, lets sort it out... There are basically three modes of	1620	Lots of arguments, lets sort it out... There are basically three modes of
1313	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1314		1622
1315	=over 4	1623	=over 4
1316		1624
1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1318		1626
1319	In this configuration the watcher triggers an event after the wallclock	1627	In this configuration the watcher triggers an event after the wall clock
1320	time C<at> has passed and doesn't repeat. It will not adjust when a time	1628	time C<at> has passed. It will not repeat and will not adjust when a time
1321	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1322	run when the system time reaches or surpasses this time.	1630	only run when the system clock reaches or surpasses this time.
1323		1631
1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1325		1633
1326	In this mode the watcher will always be scheduled to time out at the next	1634	In this mode the watcher will always be scheduled to time out at the next
1327	C<at + N * interval> time (for some integer N, which can also be negative)	1635	C<at + N * interval> time (for some integer N, which can also be negative)
1328	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1329		1637
1330	This can be used to create timers that do not drift with respect to system	1638	This can be used to create timers that do not drift with respect to the
1331	time, for example, here is a C<ev_periodic> that triggers each hour, on	1639	system clock, for example, here is a C<ev_periodic> that triggers each
1332	the hour:	1640	hour, on the hour:
1333		1641
1334	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1335		1643
1336	This doesn't mean there will always be 3600 seconds in between triggers,	1644	This doesn't mean there will always be 3600 seconds in between triggers,
1337	but only that the the callback will be called when the system time shows a	1645	but only that the callback will be called when the system time shows a
1338	full hour (UTC), or more correctly, when the system time is evenly divisible	1646	full hour (UTC), or more correctly, when the system time is evenly divisible
1339	by 3600.	1647	by 3600.
1340		1648
1341	Another way to think about it (for the mathematically inclined) is that	1649	Another way to think about it (for the mathematically inclined) is that
1342	C<ev_periodic> will try to run the callback in this mode at the next possible	1650	C<ev_periodic> will try to run the callback in this mode at the next possible
…		…
1344		1652
1345	For numerical stability it is preferable that the C<at> value is near	1653	For numerical stability it is preferable that the C<at> value is near
1346	C<ev_now ()> (the current time), but there is no range requirement for	1654	C<ev_now ()> (the current time), but there is no range requirement for
1347	this value, and in fact is often specified as zero.	1655	this value, and in fact is often specified as zero.
1348		1656
1349	Note also that there is an upper limit to how often a timer can fire (cpu	1657	Note also that there is an upper limit to how often a timer can fire (CPU
1350	speed for example), so if C<interval> is very small then timing stability	1658	speed for example), so if C<interval> is very small then timing stability
1351	will of course detoriate. Libev itself tries to be exact to be about one	1659	will of course deteriorate. Libev itself tries to be exact to be about one
1352	millisecond (if the OS supports it and the machine is fast enough).	1660	millisecond (if the OS supports it and the machine is fast enough).
1353		1661
1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1355		1663
1356	In this mode the values for C<interval> and C<at> are both being	1664	In this mode the values for C<interval> and C<at> are both being
…		…
1363		1671
1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1365	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1366	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1367		1675
1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1369	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1370		1678
		1679	static ev_tstamp
1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1372	{	1681	{
1373	return now + 60.;	1682	return now + 60.;
1374	}	1683	}
1375		1684
1376	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
…		…
1413		1722
1414	The current interval value. Can be modified any time, but changes only	1723	The current interval value. Can be modified any time, but changes only
1415	take effect when the periodic timer fires or C<ev_periodic_again> is being	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1416	called.	1725	called.
1417		1726
1418	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1419		1728
1420	The current reschedule callback, or C<0>, if this functionality is	1729	The current reschedule callback, or C<0>, if this functionality is
1421	switched off. Can be changed any time, but changes only take effect when	1730	switched off. Can be changed any time, but changes only take effect when
1422	the periodic timer fires or C<ev_periodic_again> is being called.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1423		1732
1424	=back	1733	=back
1425		1734
1426	=head3 Examples	1735	=head3 Examples
1427		1736
1428	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1429	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1430	potentially a lot of jittering, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1431		1740
1432	static void	1741	static void
1433	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1434	{	1743	{
1435	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1436	}	1745	}
1437		1746
1438	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1439	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1440	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1441		1750
1442	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1443		1752
1444	#include <math.h>	1753	#include <math.h>
1445		1754
1446	static ev_tstamp	1755	static ev_tstamp
1447	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1448	{	1757	{
1449	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1450	}	1759	}
1451		1760
1452	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1453		1762
1454	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1455		1764
1456	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1457	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1458	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1459	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1460		1769
1461		1770
1462	=head2 C<ev_signal> - signal me when a signal gets signalled!	1771	=head2 C<ev_signal> - signal me when a signal gets signalled!
1463		1772
1464	Signal watchers will trigger an event when the process receives a specific	1773	Signal watchers will trigger an event when the process receives a specific
1465	signal one or more times. Even though signals are very asynchronous, libev	1774	signal one or more times. Even though signals are very asynchronous, libev
1466	will try it's best to deliver signals synchronously, i.e. as part of the	1775	will try it's best to deliver signals synchronously, i.e. as part of the
1467	normal event processing, like any other event.	1776	normal event processing, like any other event.
1468		1777
		1778	If you want signals asynchronously, just use C<sigaction> as you would
		1779	do without libev and forget about sharing the signal. You can even use
		1780	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1781
1469	You can configure as many watchers as you like per signal. Only when the	1782	You can configure as many watchers as you like per signal. Only when the
1470	first watcher gets started will libev actually register a signal watcher	1783	first watcher gets started will libev actually register a signal handler
1471	with the kernel (thus it coexists with your own signal handlers as long	1784	with the kernel (thus it coexists with your own signal handlers as long as
1472	as you don't register any with libev). Similarly, when the last signal	1785	you don't register any with libev for the same signal). Similarly, when
1473	watcher for a signal is stopped libev will reset the signal handler to	1786	the last signal watcher for a signal is stopped, libev will reset the
1474	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
1475		1788
1476	If possible and supported, libev will install its handlers with	1789	If possible and supported, libev will install its handlers with
1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1478	interrupted. If you have a problem with syscalls getting interrupted by	1791	interrupted. If you have a problem with system calls getting interrupted by
1479	signals you can block all signals in an C<ev_check> watcher and unblock	1792	signals you can block all signals in an C<ev_check> watcher and unblock
1480	them in an C<ev_prepare> watcher.	1793	them in an C<ev_prepare> watcher.
1481		1794
1482	=head3 Watcher-Specific Functions and Data Members	1795	=head3 Watcher-Specific Functions and Data Members
1483		1796
…		…
1496		1809
1497	=back	1810	=back
1498		1811
1499	=head3 Examples	1812	=head3 Examples
1500		1813
1501	Example: Try to exit cleanly on SIGINT and SIGTERM.	1814	Example: Try to exit cleanly on SIGINT.
1502		1815
1503	static void	1816	static void
1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1505	{	1818	{
1506	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1507	}	1820	}
1508		1821
1509	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1511	ev_signal_start (loop, &sigint_cb);	1824	ev_signal_start (loop, &signal_watcher);
1512		1825
1513		1826
1514	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1515		1828
1516	Child watchers trigger when your process receives a SIGCHLD in response to	1829	Child watchers trigger when your process receives a SIGCHLD in response to
1517	some child status changes (most typically when a child of yours dies). It	1830	some child status changes (most typically when a child of yours dies or
1518	is permissible to install a child watcher I<after> the child has been	1831	exits). It is permissible to install a child watcher I<after> the child
1519	forked (which implies it might have already exited), as long as the event	1832	has been forked (which implies it might have already exited), as long
1520	loop isn't entered (or is continued from a watcher).	1833	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1834	forking and then immediately registering a watcher for the child is fine,
		1835	but forking and registering a watcher a few event loop iterations later is
		1836	not.
1521		1837
1522	Only the default event loop is capable of handling signals, and therefore	1838	Only the default event loop is capable of handling signals, and therefore
1523	you can only rgeister child watchers in the default event loop.	1839	you can only register child watchers in the default event loop.
1524		1840
1525	=head3 Process Interaction	1841	=head3 Process Interaction
1526		1842
1527	Libev grabs C<SIGCHLD> as soon as the default event loop is	1843	Libev grabs C<SIGCHLD> as soon as the default event loop is
1528	initialised. This is necessary to guarantee proper behaviour even if	1844	initialised. This is necessary to guarantee proper behaviour even if
1529	the first child watcher is started after the child exits. The occurance	1845	the first child watcher is started after the child exits. The occurrence
1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1531	synchronously as part of the event loop processing. Libev always reaps all	1847	synchronously as part of the event loop processing. Libev always reaps all
1532	children, even ones not watched.	1848	children, even ones not watched.
1533		1849
1534	=head3 Overriding the Built-In Processing	1850	=head3 Overriding the Built-In Processing
…		…
1538	handler, you can override it easily by installing your own handler for	1854	handler, you can override it easily by installing your own handler for
1539	C<SIGCHLD> after initialising the default loop, and making sure the	1855	C<SIGCHLD> after initialising the default loop, and making sure the
1540	default loop never gets destroyed. You are encouraged, however, to use an	1856	default loop never gets destroyed. You are encouraged, however, to use an
1541	event-based approach to child reaping and thus use libev's support for	1857	event-based approach to child reaping and thus use libev's support for
1542	that, so other libev users can use C<ev_child> watchers freely.	1858	that, so other libev users can use C<ev_child> watchers freely.
		1859
		1860	=head3 Stopping the Child Watcher
		1861
		1862	Currently, the child watcher never gets stopped, even when the
		1863	child terminates, so normally one needs to stop the watcher in the
		1864	callback. Future versions of libev might stop the watcher automatically
		1865	when a child exit is detected.
1543		1866
1544	=head3 Watcher-Specific Functions and Data Members	1867	=head3 Watcher-Specific Functions and Data Members
1545		1868
1546	=over 4	1869	=over 4
1547		1870
…		…
1576	=head3 Examples	1899	=head3 Examples
1577		1900
1578	Example: C<fork()> a new process and install a child handler to wait for	1901	Example: C<fork()> a new process and install a child handler to wait for
1579	its completion.	1902	its completion.
1580		1903
1581	ev_child cw;	1904	ev_child cw;
1582		1905
1583	static void	1906	static void
1584	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1585	{	1908	{
1586	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1588	}	1911	}
1589		1912
1590	pid_t pid = fork ();	1913	pid_t pid = fork ();
1591		1914
1592	if (pid < 0)	1915	if (pid < 0)
1593	// error	1916	// error
1594	else if (pid == 0)	1917	else if (pid == 0)
1595	{	1918	{
1596	// the forked child executes here	1919	// the forked child executes here
1597	exit (1);	1920	exit (1);
1598	}	1921	}
1599	else	1922	else
1600	{	1923	{
1601	ev_child_init (&cw, child_cb, pid, 0);	1924	ev_child_init (&cw, child_cb, pid, 0);
1602	ev_child_start (EV_DEFAULT_ &cw);	1925	ev_child_start (EV_DEFAULT_ &cw);
1603	}	1926	}
1604		1927
1605		1928
1606	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1607		1930
1608	This watches a filesystem path for attribute changes. That is, it calls	1931	This watches a file system path for attribute changes. That is, it calls
1609	C<stat> regularly (or when the OS says it changed) and sees if it changed	1932	C<stat> on that path in regular intervals (or when the OS says it changed)
1610	compared to the last time, invoking the callback if it did.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1611		1935
1612	The path does not need to exist: changing from "path exists" to "path does	1936	The path does not need to exist: changing from "path exists" to "path does
1613	not exist" is a status change like any other. The condition "path does	1937	not exist" is a status change like any other. The condition "path does not
1614	not exist" is signified by the C<st_nlink> field being zero (which is	1938	exist" (or more correctly "path cannot be stat'ed") is signified by the
1615	otherwise always forced to be at least one) and all the other fields of	1939	C<st_nlink> field being zero (which is otherwise always forced to be at
1616	the stat buffer having unspecified contents.	1940	least one) and all the other fields of the stat buffer having unspecified
		1941	contents.
1617		1942
1618	The path I<should> be absolute and I<must not> end in a slash. If it is	1943	The path I<must not> end in a slash or contain special components such as
		1944	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1619	relative and your working directory changes, the behaviour is undefined.	1945	your working directory changes, then the behaviour is undefined.
1620		1946
1621	Since there is no standard to do this, the portable implementation simply	1947	Since there is no portable change notification interface available, the
1622	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1948	portable implementation simply calls C<stat(2)> regularly on the path
1623	can specify a recommended polling interval for this case. If you specify	1949	to see if it changed somehow. You can specify a recommended polling
1624	a polling interval of C<0> (highly recommended!) then a I<suitable,	1950	interval for this case. If you specify a polling interval of C<0> (highly
1625	unspecified default> value will be used (which you can expect to be around	1951	recommended!) then a I<suitable, unspecified default> value will be used
1626	five seconds, although this might change dynamically). Libev will also	1952	(which you can expect to be around five seconds, although this might
1627	impose a minimum interval which is currently around C<0.1>, but thats	1953	change dynamically). Libev will also impose a minimum interval which is
1628	usually overkill.	1954	currently around C<0.1>, but that's usually overkill.
1629		1955
1630	This watcher type is not meant for massive numbers of stat watchers,	1956	This watcher type is not meant for massive numbers of stat watchers,
1631	as even with OS-supported change notifications, this can be	1957	as even with OS-supported change notifications, this can be
1632	resource-intensive.	1958	resource-intensive.
1633		1959
1634	At the time of this writing, only the Linux inotify interface is	1960	At the time of this writing, the only OS-specific interface implemented
1635	implemented (implementing kqueue support is left as an exercise for the	1961	is the Linux inotify interface (implementing kqueue support is left as an
1636	reader, note, however, that the author sees no way of implementing ev_stat	1962	exercise for the reader. Note, however, that the author sees no way of
1637	semantics with kqueue). Inotify will be used to give hints only and should	1963	implementing C<ev_stat> semantics with kqueue, except as a hint).
1638	not change the semantics of C<ev_stat> watchers, which means that libev
1639	sometimes needs to fall back to regular polling again even with inotify,
1640	but changes are usually detected immediately, and if the file exists there
1641	will be no polling.
1642		1964
1643	=head3 ABI Issues (Largefile Support)	1965	=head3 ABI Issues (Largefile Support)
1644		1966
1645	Libev by default (unless the user overrides this) uses the default	1967	Libev by default (unless the user overrides this) uses the default
1646	compilation environment, which means that on systems with optionally	1968	compilation environment, which means that on systems with large file
1647	disabled large file support, you get the 32 bit version of the stat	1969	support disabled by default, you get the 32 bit version of the stat
1648	structure. When using the library from programs that change the ABI to	1970	structure. When using the library from programs that change the ABI to
1649	use 64 bit file offsets the programs will fail. In that case you have to	1971	use 64 bit file offsets the programs will fail. In that case you have to
1650	compile libev with the same flags to get binary compatibility. This is	1972	compile libev with the same flags to get binary compatibility. This is
1651	obviously the case with any flags that change the ABI, but the problem is	1973	obviously the case with any flags that change the ABI, but the problem is
1652	most noticably with ev_stat and largefile support.	1974	most noticeably displayed with ev_stat and large file support.
1653		1975
1654	=head3 Inotify	1976	The solution for this is to lobby your distribution maker to make large
		1977	file interfaces available by default (as e.g. FreeBSD does) and not
		1978	optional. Libev cannot simply switch on large file support because it has
		1979	to exchange stat structures with application programs compiled using the
		1980	default compilation environment.
1655		1981
		1982	=head3 Inotify and Kqueue
		1983
1656	When C<inotify (7)> support has been compiled into libev (generally only	1984	When C<inotify (7)> support has been compiled into libev and present at
1657	available on Linux) and present at runtime, it will be used to speed up	1985	runtime, it will be used to speed up change detection where possible. The
1658	change detection where possible. The inotify descriptor will be created lazily	1986	inotify descriptor will be created lazily when the first C<ev_stat>
1659	when the first C<ev_stat> watcher is being started.	1987	watcher is being started.
1660		1988
1661	Inotify presence does not change the semantics of C<ev_stat> watchers	1989	Inotify presence does not change the semantics of C<ev_stat> watchers
1662	except that changes might be detected earlier, and in some cases, to avoid	1990	except that changes might be detected earlier, and in some cases, to avoid
1663	making regular C<stat> calls. Even in the presence of inotify support	1991	making regular C<stat> calls. Even in the presence of inotify support
1664	there are many cases where libev has to resort to regular C<stat> polling.	1992	there are many cases where libev has to resort to regular C<stat> polling,
		1993	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1994	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1995	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1996	xfs are fully working) libev usually gets away without polling.
1665		1997
1666	(There is no support for kqueue, as apparently it cannot be used to	1998	There is no support for kqueue, as apparently it cannot be used to
1667	implement this functionality, due to the requirement of having a file	1999	implement this functionality, due to the requirement of having a file
1668	descriptor open on the object at all times).	2000	descriptor open on the object at all times, and detecting renames, unlinks
		2001	etc. is difficult.
1669		2002
1670	=head3 The special problem of stat time resolution	2003	=head3 The special problem of stat time resolution
1671		2004
1672	The C<stat ()> syscall only supports full-second resolution portably, and	2005	The C<stat ()> system call only supports full-second resolution portably,
1673	even on systems where the resolution is higher, many filesystems still	2006	and even on systems where the resolution is higher, most file systems
1674	only support whole seconds.	2007	still only support whole seconds.
1675		2008
1676	That means that, if the time is the only thing that changes, you can	2009	That means that, if the time is the only thing that changes, you can
1677	easily miss updates: on the first update, C<ev_stat> detects a change and	2010	easily miss updates: on the first update, C<ev_stat> detects a change and
1678	calls your callback, which does something. When there is another update	2011	calls your callback, which does something. When there is another update
1679	within the same second, C<ev_stat> will be unable to detect it as the stat	2012	within the same second, C<ev_stat> will be unable to detect unless the
1680	data does not change.	2013	stat data does change in other ways (e.g. file size).
1681		2014
1682	The solution to this is to delay acting on a change for slightly more	2015	The solution to this is to delay acting on a change for slightly more
1683	than a second (or till slightly after the next full second boundary), using	2016	than a second (or till slightly after the next full second boundary), using
1684	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2017	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1685	ev_timer_again (loop, w)>).	2018	ev_timer_again (loop, w)>).
…		…
1705	C<path>. The C<interval> is a hint on how quickly a change is expected to	2038	C<path>. The C<interval> is a hint on how quickly a change is expected to
1706	be detected and should normally be specified as C<0> to let libev choose	2039	be detected and should normally be specified as C<0> to let libev choose
1707	a suitable value. The memory pointed to by C<path> must point to the same	2040	a suitable value. The memory pointed to by C<path> must point to the same
1708	path for as long as the watcher is active.	2041	path for as long as the watcher is active.
1709		2042
1710	The callback will receive C<EV_STAT> when a change was detected, relative	2043	The callback will receive an C<EV_STAT> event when a change was detected,
1711	to the attributes at the time the watcher was started (or the last change	2044	relative to the attributes at the time the watcher was started (or the
1712	was detected).	2045	last change was detected).
1713		2046
1714	=item ev_stat_stat (loop, ev_stat *)	2047	=item ev_stat_stat (loop, ev_stat *)
1715		2048
1716	Updates the stat buffer immediately with new values. If you change the	2049	Updates the stat buffer immediately with new values. If you change the
1717	watched path in your callback, you could call this function to avoid	2050	watched path in your callback, you could call this function to avoid
…		…
1738		2071
1739	The specified interval.	2072	The specified interval.
1740		2073
1741	=item const char *path [read-only]	2074	=item const char *path [read-only]
1742		2075
1743	The filesystem path that is being watched.	2076	The file system path that is being watched.
1744		2077
1745	=back	2078	=back
1746		2079
1747	=head3 Examples	2080	=head3 Examples
1748		2081
1749	Example: Watch C</etc/passwd> for attribute changes.	2082	Example: Watch C</etc/passwd> for attribute changes.
1750		2083
1751	static void	2084	static void
1752	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2085	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1753	{	2086	{
1754	/* /etc/passwd changed in some way */	2087	/* /etc/passwd changed in some way */
1755	if (w->attr.st_nlink)	2088	if (w->attr.st_nlink)
1756	{	2089	{
1757	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2090	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1758	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2091	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1759	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2092	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1760	}	2093	}
1761	else	2094	else
1762	/* you shalt not abuse printf for puts */	2095	/* you shalt not abuse printf for puts */
1763	puts ("wow, /etc/passwd is not there, expect problems. "	2096	puts ("wow, /etc/passwd is not there, expect problems. "
1764	"if this is windows, they already arrived\n");	2097	"if this is windows, they already arrived\n");
1765	}	2098	}
1766		2099
1767	...	2100	...
1768	ev_stat passwd;	2101	ev_stat passwd;
1769		2102
1770	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2103	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1771	ev_stat_start (loop, &passwd);	2104	ev_stat_start (loop, &passwd);
1772		2105
1773	Example: Like above, but additionally use a one-second delay so we do not	2106	Example: Like above, but additionally use a one-second delay so we do not
1774	miss updates (however, frequent updates will delay processing, too, so	2107	miss updates (however, frequent updates will delay processing, too, so
1775	one might do the work both on C<ev_stat> callback invocation I<and> on	2108	one might do the work both on C<ev_stat> callback invocation I<and> on
1776	C<ev_timer> callback invocation).	2109	C<ev_timer> callback invocation).
1777		2110
1778	static ev_stat passwd;	2111	static ev_stat passwd;
1779	static ev_timer timer;	2112	static ev_timer timer;
1780		2113
1781	static void	2114	static void
1782	timer_cb (EV_P_ ev_timer *w, int revents)	2115	timer_cb (EV_P_ ev_timer *w, int revents)
1783	{	2116	{
1784	ev_timer_stop (EV_A_ w);	2117	ev_timer_stop (EV_A_ w);
1785		2118
1786	/* now it's one second after the most recent passwd change */	2119	/* now it's one second after the most recent passwd change */
1787	}	2120	}
1788		2121
1789	static void	2122	static void
1790	stat_cb (EV_P_ ev_stat *w, int revents)	2123	stat_cb (EV_P_ ev_stat *w, int revents)
1791	{	2124	{
1792	/* reset the one-second timer */	2125	/* reset the one-second timer */
1793	ev_timer_again (EV_A_ &timer);	2126	ev_timer_again (EV_A_ &timer);
1794	}	2127	}
1795		2128
1796	...	2129	...
1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2130	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1798	ev_stat_start (loop, &passwd);	2131	ev_stat_start (loop, &passwd);
1799	ev_timer_init (&timer, timer_cb, 0., 1.02);	2132	ev_timer_init (&timer, timer_cb, 0., 1.02);
1800		2133
1801		2134
1802	=head2 C<ev_idle> - when you've got nothing better to do...	2135	=head2 C<ev_idle> - when you've got nothing better to do...
1803		2136
1804	Idle watchers trigger events when no other events of the same or higher	2137	Idle watchers trigger events when no other events of the same or higher
1805	priority are pending (prepare, check and other idle watchers do not	2138	priority are pending (prepare, check and other idle watchers do not count
1806	count).	2139	as receiving "events").
1807		2140
1808	That is, as long as your process is busy handling sockets or timeouts	2141	That is, as long as your process is busy handling sockets or timeouts
1809	(or even signals, imagine) of the same or higher priority it will not be	2142	(or even signals, imagine) of the same or higher priority it will not be
1810	triggered. But when your process is idle (or only lower-priority watchers	2143	triggered. But when your process is idle (or only lower-priority watchers
1811	are pending), the idle watchers are being called once per event loop	2144	are pending), the idle watchers are being called once per event loop
…		…
1835	=head3 Examples	2168	=head3 Examples
1836		2169
1837	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2170	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1838	callback, free it. Also, use no error checking, as usual.	2171	callback, free it. Also, use no error checking, as usual.
1839		2172
1840	static void	2173	static void
1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2174	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1842	{	2175	{
1843	free (w);	2176	free (w);
1844	// now do something you wanted to do when the program has	2177	// now do something you wanted to do when the program has
1845	// no longer anything immediate to do.	2178	// no longer anything immediate to do.
1846	}	2179	}
1847		2180
1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1849	ev_idle_init (idle_watcher, idle_cb);	2182	ev_idle_init (idle_watcher, idle_cb);
1850	ev_idle_start (loop, idle_cb);	2183	ev_idle_start (loop, idle_cb);
1851		2184
1852		2185
1853	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2186	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1854		2187
1855	Prepare and check watchers are usually (but not always) used in tandem:	2188	Prepare and check watchers are usually (but not always) used in pairs:
1856	prepare watchers get invoked before the process blocks and check watchers	2189	prepare watchers get invoked before the process blocks and check watchers
1857	afterwards.	2190	afterwards.
1858		2191
1859	You I<must not> call C<ev_loop> or similar functions that enter	2192	You I<must not> call C<ev_loop> or similar functions that enter
1860	the current event loop from either C<ev_prepare> or C<ev_check>	2193	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1863	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2196	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1864	C<ev_check> so if you have one watcher of each kind they will always be	2197	C<ev_check> so if you have one watcher of each kind they will always be
1865	called in pairs bracketing the blocking call.	2198	called in pairs bracketing the blocking call.
1866		2199
1867	Their main purpose is to integrate other event mechanisms into libev and	2200	Their main purpose is to integrate other event mechanisms into libev and
1868	their use is somewhat advanced. This could be used, for example, to track	2201	their use is somewhat advanced. They could be used, for example, to track
1869	variable changes, implement your own watchers, integrate net-snmp or a	2202	variable changes, implement your own watchers, integrate net-snmp or a
1870	coroutine library and lots more. They are also occasionally useful if	2203	coroutine library and lots more. They are also occasionally useful if
1871	you cache some data and want to flush it before blocking (for example,	2204	you cache some data and want to flush it before blocking (for example,
1872	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2205	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1873	watcher).	2206	watcher).
1874		2207
1875	This is done by examining in each prepare call which file descriptors need	2208	This is done by examining in each prepare call which file descriptors
1876	to be watched by the other library, registering C<ev_io> watchers for	2209	need to be watched by the other library, registering C<ev_io> watchers
1877	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2210	for them and starting an C<ev_timer> watcher for any timeouts (many
1878	provide just this functionality). Then, in the check watcher you check for	2211	libraries provide exactly this functionality). Then, in the check watcher,
1879	any events that occured (by checking the pending status of all watchers	2212	you check for any events that occurred (by checking the pending status
1880	and stopping them) and call back into the library. The I/O and timer	2213	of all watchers and stopping them) and call back into the library. The
1881	callbacks will never actually be called (but must be valid nevertheless,	2214	I/O and timer callbacks will never actually be called (but must be valid
1882	because you never know, you know?).	2215	nevertheless, because you never know, you know?).
1883		2216
1884	As another example, the Perl Coro module uses these hooks to integrate	2217	As another example, the Perl Coro module uses these hooks to integrate
1885	coroutines into libev programs, by yielding to other active coroutines	2218	coroutines into libev programs, by yielding to other active coroutines
1886	during each prepare and only letting the process block if no coroutines	2219	during each prepare and only letting the process block if no coroutines
1887	are ready to run (it's actually more complicated: it only runs coroutines	2220	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1890	loop from blocking if lower-priority coroutines are active, thus mapping	2223	loop from blocking if lower-priority coroutines are active, thus mapping
1891	low-priority coroutines to idle/background tasks).	2224	low-priority coroutines to idle/background tasks).
1892		2225
1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2226	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1894	priority, to ensure that they are being run before any other watchers	2227	priority, to ensure that they are being run before any other watchers
		2228	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2229
1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2230	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1896	too) should not activate ("feed") events into libev. While libev fully	2231	activate ("feed") events into libev. While libev fully supports this, they
1897	supports this, they might get executed before other C<ev_check> watchers	2232	might get executed before other C<ev_check> watchers did their job. As
1898	did their job. As C<ev_check> watchers are often used to embed other	2233	C<ev_check> watchers are often used to embed other (non-libev) event
1899	(non-libev) event loops those other event loops might be in an unusable	2234	loops those other event loops might be in an unusable state until their
1900	state until their C<ev_check> watcher ran (always remind yourself to	2235	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1901	coexist peacefully with others).	2236	others).
1902		2237
1903	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1904		2239
1905	=over 4	2240	=over 4
1906		2241
…		…
1908		2243
1909	=item ev_check_init (ev_check *, callback)	2244	=item ev_check_init (ev_check *, callback)
1910		2245
1911	Initialises and configures the prepare or check watcher - they have no	2246	Initialises and configures the prepare or check watcher - they have no
1912	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2247	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1913	macros, but using them is utterly, utterly and completely pointless.	2248	macros, but using them is utterly, utterly, utterly and completely
		2249	pointless.
1914		2250
1915	=back	2251	=back
1916		2252
1917	=head3 Examples	2253	=head3 Examples
1918		2254
…		…
1927	and in a check watcher, destroy them and call into libadns. What follows	2263	and in a check watcher, destroy them and call into libadns. What follows
1928	is pseudo-code only of course. This requires you to either use a low	2264	is pseudo-code only of course. This requires you to either use a low
1929	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2265	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1930	the callbacks for the IO/timeout watchers might not have been called yet.	2266	the callbacks for the IO/timeout watchers might not have been called yet.
1931		2267
1932	static ev_io iow [nfd];	2268	static ev_io iow [nfd];
1933	static ev_timer tw;	2269	static ev_timer tw;
1934		2270
1935	static void	2271	static void
1936	io_cb (ev_loop *loop, ev_io *w, int revents)	2272	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1937	{	2273	{
1938	}	2274	}
1939		2275
1940	// create io watchers for each fd and a timer before blocking	2276	// create io watchers for each fd and a timer before blocking
1941	static void	2277	static void
1942	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2278	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1943	{	2279	{
1944	int timeout = 3600000;	2280	int timeout = 3600000;
1945	struct pollfd fds [nfd];	2281	struct pollfd fds [nfd];
1946	// actual code will need to loop here and realloc etc.	2282	// actual code will need to loop here and realloc etc.
1947	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1948		2284
1949	/* the callback is illegal, but won't be called as we stop during check */	2285	/* the callback is illegal, but won't be called as we stop during check */
1950	ev_timer_init (&tw, 0, timeout * 1e-3);	2286	ev_timer_init (&tw, 0, timeout * 1e-3);
1951	ev_timer_start (loop, &tw);	2287	ev_timer_start (loop, &tw);
1952		2288
1953	// create one ev_io per pollfd	2289	// create one ev_io per pollfd
1954	for (int i = 0; i < nfd; ++i)	2290	for (int i = 0; i < nfd; ++i)
1955	{	2291	{
1956	ev_io_init (iow + i, io_cb, fds [i].fd,	2292	ev_io_init (iow + i, io_cb, fds [i].fd,
1957	((fds [i].events & POLLIN ? EV_READ : 0)	2293	((fds [i].events & POLLIN ? EV_READ : 0)
1958	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2294	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1959		2295
1960	fds [i].revents = 0;	2296	fds [i].revents = 0;
1961	ev_io_start (loop, iow + i);	2297	ev_io_start (loop, iow + i);
1962	}	2298	}
1963	}	2299	}
1964		2300
1965	// stop all watchers after blocking	2301	// stop all watchers after blocking
1966	static void	2302	static void
1967	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2303	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1968	{	2304	{
1969	ev_timer_stop (loop, &tw);	2305	ev_timer_stop (loop, &tw);
1970		2306
1971	for (int i = 0; i < nfd; ++i)	2307	for (int i = 0; i < nfd; ++i)
1972	{	2308	{
1973	// set the relevant poll flags	2309	// set the relevant poll flags
1974	// could also call adns_processreadable etc. here	2310	// could also call adns_processreadable etc. here
1975	struct pollfd *fd = fds + i;	2311	struct pollfd *fd = fds + i;
1976	int revents = ev_clear_pending (iow + i);	2312	int revents = ev_clear_pending (iow + i);
1977	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2313	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1978	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2314	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1979		2315
1980	// now stop the watcher	2316	// now stop the watcher
1981	ev_io_stop (loop, iow + i);	2317	ev_io_stop (loop, iow + i);
1982	}	2318	}
1983		2319
1984	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2320	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1985	}	2321	}
1986		2322
1987	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2323	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1988	in the prepare watcher and would dispose of the check watcher.	2324	in the prepare watcher and would dispose of the check watcher.
1989		2325
1990	Method 3: If the module to be embedded supports explicit event	2326	Method 3: If the module to be embedded supports explicit event
1991	notification (adns does), you can also make use of the actual watcher	2327	notification (libadns does), you can also make use of the actual watcher
1992	callbacks, and only destroy/create the watchers in the prepare watcher.	2328	callbacks, and only destroy/create the watchers in the prepare watcher.
1993		2329
1994	static void	2330	static void
1995	timer_cb (EV_P_ ev_timer *w, int revents)	2331	timer_cb (EV_P_ ev_timer *w, int revents)
1996	{	2332	{
1997	adns_state ads = (adns_state)w->data;	2333	adns_state ads = (adns_state)w->data;
1998	update_now (EV_A);	2334	update_now (EV_A);
1999		2335
2000	adns_processtimeouts (ads, &tv_now);	2336	adns_processtimeouts (ads, &tv_now);
2001	}	2337	}
2002		2338
2003	static void	2339	static void
2004	io_cb (EV_P_ ev_io *w, int revents)	2340	io_cb (EV_P_ ev_io *w, int revents)
2005	{	2341	{
2006	adns_state ads = (adns_state)w->data;	2342	adns_state ads = (adns_state)w->data;
2007	update_now (EV_A);	2343	update_now (EV_A);
2008		2344
2009	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2345	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2010	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2346	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2011	}	2347	}
2012		2348
2013	// do not ever call adns_afterpoll	2349	// do not ever call adns_afterpoll
2014		2350
2015	Method 4: Do not use a prepare or check watcher because the module you	2351	Method 4: Do not use a prepare or check watcher because the module you
2016	want to embed is too inflexible to support it. Instead, youc na override	2352	want to embed is not flexible enough to support it. Instead, you can
2017	their poll function. The drawback with this solution is that the main	2353	override their poll function. The drawback with this solution is that the
2018	loop is now no longer controllable by EV. The C<Glib::EV> module does	2354	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2019	this.	2355	this approach, effectively embedding EV as a client into the horrible
		2356	libglib event loop.
2020		2357
2021	static gint	2358	static gint
2022	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2359	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2023	{	2360	{
2024	int got_events = 0;	2361	int got_events = 0;
2025		2362
2026	for (n = 0; n < nfds; ++n)	2363	for (n = 0; n < nfds; ++n)
2027	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2364	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2028		2365
2029	if (timeout >= 0)	2366	if (timeout >= 0)
2030	// create/start timer	2367	// create/start timer
2031		2368
2032	// poll	2369	// poll
2033	ev_loop (EV_A_ 0);	2370	ev_loop (EV_A_ 0);
2034		2371
2035	// stop timer again	2372	// stop timer again
2036	if (timeout >= 0)	2373	if (timeout >= 0)
2037	ev_timer_stop (EV_A_ &to);	2374	ev_timer_stop (EV_A_ &to);
2038		2375
2039	// stop io watchers again - their callbacks should have set	2376	// stop io watchers again - their callbacks should have set
2040	for (n = 0; n < nfds; ++n)	2377	for (n = 0; n < nfds; ++n)
2041	ev_io_stop (EV_A_ iow [n]);	2378	ev_io_stop (EV_A_ iow [n]);
2042		2379
2043	return got_events;	2380	return got_events;
2044	}	2381	}
2045		2382
2046		2383
2047	=head2 C<ev_embed> - when one backend isn't enough...	2384	=head2 C<ev_embed> - when one backend isn't enough...
2048		2385
2049	This is a rather advanced watcher type that lets you embed one event loop	2386	This is a rather advanced watcher type that lets you embed one event loop
…		…
2055	prioritise I/O.	2392	prioritise I/O.
2056		2393
2057	As an example for a bug workaround, the kqueue backend might only support	2394	As an example for a bug workaround, the kqueue backend might only support
2058	sockets on some platform, so it is unusable as generic backend, but you	2395	sockets on some platform, so it is unusable as generic backend, but you
2059	still want to make use of it because you have many sockets and it scales	2396	still want to make use of it because you have many sockets and it scales
2060	so nicely. In this case, you would create a kqueue-based loop and embed it	2397	so nicely. In this case, you would create a kqueue-based loop and embed
2061	into your default loop (which might use e.g. poll). Overall operation will	2398	it into your default loop (which might use e.g. poll). Overall operation
2062	be a bit slower because first libev has to poll and then call kevent, but	2399	will be a bit slower because first libev has to call C<poll> and then
2063	at least you can use both at what they are best.	2400	C<kevent>, but at least you can use both mechanisms for what they are
		2401	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2064		2402
2065	As for prioritising I/O: rarely you have the case where some fds have	2403	As for prioritising I/O: under rare circumstances you have the case where
2066	to be watched and handled very quickly (with low latency), and even	2404	some fds have to be watched and handled very quickly (with low latency),
2067	priorities and idle watchers might have too much overhead. In this case	2405	and even priorities and idle watchers might have too much overhead. In
2068	you would put all the high priority stuff in one loop and all the rest in	2406	this case you would put all the high priority stuff in one loop and all
2069	a second one, and embed the second one in the first.	2407	the rest in a second one, and embed the second one in the first.
2070		2408
2071	As long as the watcher is active, the callback will be invoked every time	2409	As long as the watcher is active, the callback will be invoked every time
2072	there might be events pending in the embedded loop. The callback must then	2410	there might be events pending in the embedded loop. The callback must then
2073	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2411	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2074	their callbacks (you could also start an idle watcher to give the embedded	2412	their callbacks (you could also start an idle watcher to give the embedded
…		…
2082	interested in that.	2420	interested in that.
2083		2421
2084	Also, there have not currently been made special provisions for forking:	2422	Also, there have not currently been made special provisions for forking:
2085	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2423	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2086	but you will also have to stop and restart any C<ev_embed> watchers	2424	but you will also have to stop and restart any C<ev_embed> watchers
2087	yourself.	2425	yourself - but you can use a fork watcher to handle this automatically,
		2426	and future versions of libev might do just that.
2088		2427
2089	Unfortunately, not all backends are embeddable, only the ones returned by	2428	Unfortunately, not all backends are embeddable: only the ones returned by
2090	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2429	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2091	portable one.	2430	portable one.
2092		2431
2093	So when you want to use this feature you will always have to be prepared	2432	So when you want to use this feature you will always have to be prepared
2094	that you cannot get an embeddable loop. The recommended way to get around	2433	that you cannot get an embeddable loop. The recommended way to get around
2095	this is to have a separate variables for your embeddable loop, try to	2434	this is to have a separate variables for your embeddable loop, try to
2096	create it, and if that fails, use the normal loop for everything.	2435	create it, and if that fails, use the normal loop for everything.
2097		2436
		2437	=head3 C<ev_embed> and fork
		2438
		2439	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2440	automatically be applied to the embedded loop as well, so no special
		2441	fork handling is required in that case. When the watcher is not running,
		2442	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2443	as applicable.
		2444
2098	=head3 Watcher-Specific Functions and Data Members	2445	=head3 Watcher-Specific Functions and Data Members
2099		2446
2100	=over 4	2447	=over 4
2101		2448
2102	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2449	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2105		2452
2106	Configures the watcher to embed the given loop, which must be	2453	Configures the watcher to embed the given loop, which must be
2107	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2454	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2108	invoked automatically, otherwise it is the responsibility of the callback	2455	invoked automatically, otherwise it is the responsibility of the callback
2109	to invoke it (it will continue to be called until the sweep has been done,	2456	to invoke it (it will continue to be called until the sweep has been done,
2110	if you do not want thta, you need to temporarily stop the embed watcher).	2457	if you do not want that, you need to temporarily stop the embed watcher).
2111		2458
2112	=item ev_embed_sweep (loop, ev_embed *)	2459	=item ev_embed_sweep (loop, ev_embed *)
2113		2460
2114	Make a single, non-blocking sweep over the embedded loop. This works	2461	Make a single, non-blocking sweep over the embedded loop. This works
2115	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2462	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2116	apropriate way for embedded loops.	2463	appropriate way for embedded loops.
2117		2464
2118	=item struct ev_loop *other [read-only]	2465	=item struct ev_loop *other [read-only]
2119		2466
2120	The embedded event loop.	2467	The embedded event loop.
2121		2468
…		…
2123		2470
2124	=head3 Examples	2471	=head3 Examples
2125		2472
2126	Example: Try to get an embeddable event loop and embed it into the default	2473	Example: Try to get an embeddable event loop and embed it into the default
2127	event loop. If that is not possible, use the default loop. The default	2474	event loop. If that is not possible, use the default loop. The default
2128	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2475	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2129	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2476	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2130	used).	2477	used).
2131		2478
2132	struct ev_loop *loop_hi = ev_default_init (0);	2479	struct ev_loop *loop_hi = ev_default_init (0);
2133	struct ev_loop *loop_lo = 0;	2480	struct ev_loop *loop_lo = 0;
2134	struct ev_embed embed;	2481	ev_embed embed;
2135		2482
2136	// see if there is a chance of getting one that works	2483	// see if there is a chance of getting one that works
2137	// (remember that a flags value of 0 means autodetection)	2484	// (remember that a flags value of 0 means autodetection)
2138	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2139	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2140	: 0;	2487	: 0;
2141		2488
2142	// if we got one, then embed it, otherwise default to loop_hi	2489	// if we got one, then embed it, otherwise default to loop_hi
2143	if (loop_lo)	2490	if (loop_lo)
2144	{	2491	{
2145	ev_embed_init (&embed, 0, loop_lo);	2492	ev_embed_init (&embed, 0, loop_lo);
2146	ev_embed_start (loop_hi, &embed);	2493	ev_embed_start (loop_hi, &embed);
2147	}	2494	}
2148	else	2495	else
2149	loop_lo = loop_hi;	2496	loop_lo = loop_hi;
2150		2497
2151	Example: Check if kqueue is available but not recommended and create	2498	Example: Check if kqueue is available but not recommended and create
2152	a kqueue backend for use with sockets (which usually work with any	2499	a kqueue backend for use with sockets (which usually work with any
2153	kqueue implementation). Store the kqueue/socket-only event loop in	2500	kqueue implementation). Store the kqueue/socket-only event loop in
2154	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2501	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2155		2502
2156	struct ev_loop *loop = ev_default_init (0);	2503	struct ev_loop *loop = ev_default_init (0);
2157	struct ev_loop *loop_socket = 0;	2504	struct ev_loop *loop_socket = 0;
2158	struct ev_embed embed;	2505	ev_embed embed;
2159		2506
2160	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2507	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2161	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2508	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2162	{	2509	{
2163	ev_embed_init (&embed, 0, loop_socket);	2510	ev_embed_init (&embed, 0, loop_socket);
2164	ev_embed_start (loop, &embed);	2511	ev_embed_start (loop, &embed);
2165	}	2512	}
2166		2513
2167	if (!loop_socket)	2514	if (!loop_socket)
2168	loop_socket = loop;	2515	loop_socket = loop;
2169		2516
2170	// now use loop_socket for all sockets, and loop for everything else	2517	// now use loop_socket for all sockets, and loop for everything else
2171		2518
2172		2519
2173	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2520	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2174		2521
2175	Fork watchers are called when a C<fork ()> was detected (usually because	2522	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2219	is that the author does not know of a simple (or any) algorithm for a	2566	is that the author does not know of a simple (or any) algorithm for a
2220	multiple-writer-single-reader queue that works in all cases and doesn't	2567	multiple-writer-single-reader queue that works in all cases and doesn't
2221	need elaborate support such as pthreads.	2568	need elaborate support such as pthreads.
2222		2569
2223	That means that if you want to queue data, you have to provide your own	2570	That means that if you want to queue data, you have to provide your own
2224	queue. But at least I can tell you would implement locking around your	2571	queue. But at least I can tell you how to implement locking around your
2225	queue:	2572	queue:
2226		2573
2227	=over 4	2574	=over 4
2228		2575
2229	=item queueing from a signal handler context	2576	=item queueing from a signal handler context
2230		2577
2231	To implement race-free queueing, you simply add to the queue in the signal	2578	To implement race-free queueing, you simply add to the queue in the signal
2232	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2579	handler but you block the signal handler in the watcher callback. Here is
2233	some fictitiuous SIGUSR1 handler:	2580	an example that does that for some fictitious SIGUSR1 handler:
2234		2581
2235	static ev_async mysig;	2582	static ev_async mysig;
2236		2583
2237	static void	2584	static void
2238	sigusr1_handler (void)	2585	sigusr1_handler (void)
…		…
2304	=over 4	2651	=over 4
2305		2652
2306	=item ev_async_init (ev_async *, callback)	2653	=item ev_async_init (ev_async *, callback)
2307		2654
2308	Initialises and configures the async watcher - it has no parameters of any	2655	Initialises and configures the async watcher - it has no parameters of any
2309	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2656	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2310	believe me.	2657	trust me.
2311		2658
2312	=item ev_async_send (loop, ev_async *)	2659	=item ev_async_send (loop, ev_async *)
2313		2660
2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2661	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2315	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2662	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2316	C<ev_feed_event>, this call is safe to do in other threads, signal or	2663	C<ev_feed_event>, this call is safe to do from other threads, signal or
2317	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2664	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2318	section below on what exactly this means).	2665	section below on what exactly this means).
2319		2666
2320	This call incurs the overhead of a syscall only once per loop iteration,	2667	This call incurs the overhead of a system call only once per loop iteration,
2321	so while the overhead might be noticable, it doesn't apply to repeated	2668	so while the overhead might be noticeable, it doesn't apply to repeated
2322	calls to C<ev_async_send>.	2669	calls to C<ev_async_send>.
2323		2670
2324	=item bool = ev_async_pending (ev_async *)	2671	=item bool = ev_async_pending (ev_async *)
2325		2672
2326	Returns a non-zero value when C<ev_async_send> has been called on the	2673	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2328	event loop.	2675	event loop.
2329		2676
2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2677	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2331	the loop iterates next and checks for the watcher to have become active,	2678	the loop iterates next and checks for the watcher to have become active,
2332	it will reset the flag again. C<ev_async_pending> can be used to very	2679	it will reset the flag again. C<ev_async_pending> can be used to very
2333	quickly check wether invoking the loop might be a good idea.	2680	quickly check whether invoking the loop might be a good idea.
2334		2681
2335	Not that this does I<not> check wether the watcher itself is pending, only	2682	Not that this does I<not> check whether the watcher itself is pending, only
2336	wether it has been requested to make this watcher pending.	2683	whether it has been requested to make this watcher pending.
2337		2684
2338	=back	2685	=back
2339		2686
2340		2687
2341	=head1 OTHER FUNCTIONS	2688	=head1 OTHER FUNCTIONS
…		…
2345	=over 4	2692	=over 4
2346		2693
2347	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2694	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2348		2695
2349	This function combines a simple timer and an I/O watcher, calls your	2696	This function combines a simple timer and an I/O watcher, calls your
2350	callback on whichever event happens first and automatically stop both	2697	callback on whichever event happens first and automatically stops both
2351	watchers. This is useful if you want to wait for a single event on an fd	2698	watchers. This is useful if you want to wait for a single event on an fd
2352	or timeout without having to allocate/configure/start/stop/free one or	2699	or timeout without having to allocate/configure/start/stop/free one or
2353	more watchers yourself.	2700	more watchers yourself.
2354		2701
2355	If C<fd> is less than 0, then no I/O watcher will be started and events	2702	If C<fd> is less than 0, then no I/O watcher will be started and the
2356	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2703	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2357	C<events> set will be craeted and started.	2704	the given C<fd> and C<events> set will be created and started.
2358		2705
2359	If C<timeout> is less than 0, then no timeout watcher will be	2706	If C<timeout> is less than 0, then no timeout watcher will be
2360	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2707	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2361	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2708	repeat = 0) will be started. C<0> is a valid timeout.
2362	dubious value.
2363		2709
2364	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2710	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2365	passed an C<revents> set like normal event callbacks (a combination of	2711	passed an C<revents> set like normal event callbacks (a combination of
2366	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2712	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2367	value passed to C<ev_once>:	2713	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2714	a timeout and an io event at the same time - you probably should give io
		2715	events precedence.
2368		2716
		2717	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2718
2369	static void stdin_ready (int revents, void *arg)	2719	static void stdin_ready (int revents, void *arg)
2370	{	2720	{
2371	if (revents & EV_TIMEOUT)
2372	/* doh, nothing entered */;
2373	else if (revents & EV_READ)	2721	if (revents & EV_READ)
2374	/* stdin might have data for us, joy! */;	2722	/* stdin might have data for us, joy! */;
		2723	else if (revents & EV_TIMEOUT)
		2724	/* doh, nothing entered */;
2375	}	2725	}
2376		2726
2377	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2378		2728
2379	=item ev_feed_event (ev_loop *, watcher *, int revents)	2729	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2380		2730
2381	Feeds the given event set into the event loop, as if the specified event	2731	Feeds the given event set into the event loop, as if the specified event
2382	had happened for the specified watcher (which must be a pointer to an	2732	had happened for the specified watcher (which must be a pointer to an
2383	initialised but not necessarily started event watcher).	2733	initialised but not necessarily started event watcher).
2384		2734
2385	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2386		2736
2387	Feed an event on the given fd, as if a file descriptor backend detected	2737	Feed an event on the given fd, as if a file descriptor backend detected
2388	the given events it.	2738	the given events it.
2389		2739
2390	=item ev_feed_signal_event (ev_loop *loop, int signum)	2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2391		2741
2392	Feed an event as if the given signal occured (C<loop> must be the default	2742	Feed an event as if the given signal occurred (C<loop> must be the default
2393	loop!).	2743	loop!).
2394		2744
2395	=back	2745	=back
2396		2746
2397		2747
…		…
2426	=back	2776	=back
2427		2777
2428	=head1 C++ SUPPORT	2778	=head1 C++ SUPPORT
2429		2779
2430	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2780	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2431	you to use some convinience methods to start/stop watchers and also change	2781	you to use some convenience methods to start/stop watchers and also change
2432	the callback model to a model using method callbacks on objects.	2782	the callback model to a model using method callbacks on objects.
2433		2783
2434	To use it,	2784	To use it,
2435		2785
2436	#include <ev++.h>	2786	#include <ev++.h>
2437		2787
2438	This automatically includes F<ev.h> and puts all of its definitions (many	2788	This automatically includes F<ev.h> and puts all of its definitions (many
2439	of them macros) into the global namespace. All C++ specific things are	2789	of them macros) into the global namespace. All C++ specific things are
2440	put into the C<ev> namespace. It should support all the same embedding	2790	put into the C<ev> namespace. It should support all the same embedding
2441	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2791	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2508	your compiler is good :), then the method will be fully inlined into the	2858	your compiler is good :), then the method will be fully inlined into the
2509	thunking function, making it as fast as a direct C callback.	2859	thunking function, making it as fast as a direct C callback.
2510		2860
2511	Example: simple class declaration and watcher initialisation	2861	Example: simple class declaration and watcher initialisation
2512		2862
2513	struct myclass	2863	struct myclass
2514	{	2864	{
2515	void io_cb (ev::io &w, int revents) { }	2865	void io_cb (ev::io &w, int revents) { }
2516	}	2866	}
2517		2867
2518	myclass obj;	2868	myclass obj;
2519	ev::io iow;	2869	ev::io iow;
2520	iow.set <myclass, &myclass::io_cb> (&obj);	2870	iow.set <myclass, &myclass::io_cb> (&obj);
2521		2871
2522	=item w->set<function> (void *data = 0)	2872	=item w->set<function> (void *data = 0)
2523		2873
2524	Also sets a callback, but uses a static method or plain function as	2874	Also sets a callback, but uses a static method or plain function as
2525	callback. The optional C<data> argument will be stored in the watcher's	2875	callback. The optional C<data> argument will be stored in the watcher's
…		…
2527		2877
2528	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2878	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2529		2879
2530	See the method-C<set> above for more details.	2880	See the method-C<set> above for more details.
2531		2881
2532	Example:	2882	Example: Use a plain function as callback.
2533		2883
2534	static void io_cb (ev::io &w, int revents) { }	2884	static void io_cb (ev::io &w, int revents) { }
2535	iow.set <io_cb> ();	2885	iow.set <io_cb> ();
2536		2886
2537	=item w->set (struct ev_loop *)	2887	=item w->set (struct ev_loop *)
2538		2888
2539	Associates a different C<struct ev_loop> with this watcher. You can only	2889	Associates a different C<struct ev_loop> with this watcher. You can only
2540	do this when the watcher is inactive (and not pending either).	2890	do this when the watcher is inactive (and not pending either).
2541		2891
2542	=item w->set ([args])	2892	=item w->set ([arguments])
2543		2893
2544	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2894	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2545	called at least once. Unlike the C counterpart, an active watcher gets	2895	called at least once. Unlike the C counterpart, an active watcher gets
2546	automatically stopped and restarted when reconfiguring it with this	2896	automatically stopped and restarted when reconfiguring it with this
2547	method.	2897	method.
2548		2898
2549	=item w->start ()	2899	=item w->start ()
…		…
2573	=back	2923	=back
2574		2924
2575	Example: Define a class with an IO and idle watcher, start one of them in	2925	Example: Define a class with an IO and idle watcher, start one of them in
2576	the constructor.	2926	the constructor.
2577		2927
2578	class myclass	2928	class myclass
2579	{	2929	{
2580	ev::io io; void io_cb (ev::io &w, int revents);	2930	ev::io io ; void io_cb (ev::io &w, int revents);
2581	ev:idle idle void idle_cb (ev::idle &w, int revents);	2931	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2582		2932
2583	myclass (int fd)	2933	myclass (int fd)
2584	{	2934	{
2585	io .set <myclass, &myclass::io_cb > (this);	2935	io .set <myclass, &myclass::io_cb > (this);
2586	idle.set <myclass, &myclass::idle_cb> (this);	2936	idle.set <myclass, &myclass::idle_cb> (this);
2587		2937
2588	io.start (fd, ev::READ);	2938	io.start (fd, ev::READ);
2589	}	2939	}
2590	};	2940	};
2591		2941
2592		2942
2593	=head1 OTHER LANGUAGE BINDINGS	2943	=head1 OTHER LANGUAGE BINDINGS
2594		2944
2595	Libev does not offer other language bindings itself, but bindings for a	2945	Libev does not offer other language bindings itself, but bindings for a
2596	numbe rof languages exist in the form of third-party packages. If you know	2946	number of languages exist in the form of third-party packages. If you know
2597	any interesting language binding in addition to the ones listed here, drop	2947	any interesting language binding in addition to the ones listed here, drop
2598	me a note.	2948	me a note.
2599		2949
2600	=over 4	2950	=over 4
2601		2951
2602	=item Perl	2952	=item Perl
2603		2953
2604	The EV module implements the full libev API and is actually used to test	2954	The EV module implements the full libev API and is actually used to test
2605	libev. EV is developed together with libev. Apart from the EV core module,	2955	libev. EV is developed together with libev. Apart from the EV core module,
2606	there are additional modules that implement libev-compatible interfaces	2956	there are additional modules that implement libev-compatible interfaces
2607	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2957	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2608	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2958	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2959	and C<EV::Glib>).
2609		2960
2610	It can be found and installed via CPAN, its homepage is found at	2961	It can be found and installed via CPAN, its homepage is at
2611	L<http://software.schmorp.de/pkg/EV>.	2962	L<http://software.schmorp.de/pkg/EV>.
2612		2963
		2964	=item Python
		2965
		2966	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2967	seems to be quite complete and well-documented. Note, however, that the
		2968	patch they require for libev is outright dangerous as it breaks the ABI
		2969	for everybody else, and therefore, should never be applied in an installed
		2970	libev (if python requires an incompatible ABI then it needs to embed
		2971	libev).
		2972
2613	=item Ruby	2973	=item Ruby
2614		2974
2615	Tony Arcieri has written a ruby extension that offers access to a subset	2975	Tony Arcieri has written a ruby extension that offers access to a subset
2616	of the libev API and adds filehandle abstractions, asynchronous DNS and	2976	of the libev API and adds file handle abstractions, asynchronous DNS and
2617	more on top of it. It can be found via gem servers. Its homepage is at	2977	more on top of it. It can be found via gem servers. Its homepage is at
2618	L<http://rev.rubyforge.org/>.	2978	L<http://rev.rubyforge.org/>.
2619		2979
2620	=item D	2980	=item D
2621		2981
2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2982	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2623	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2983	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2984
		2985	=item Ocaml
		2986
		2987	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2988	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2624		2989
2625	=back	2990	=back
2626		2991
2627		2992
2628	=head1 MACRO MAGIC	2993	=head1 MACRO MAGIC
2629		2994
2630	Libev can be compiled with a variety of options, the most fundamantal	2995	Libev can be compiled with a variety of options, the most fundamental
2631	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2996	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2632	functions and callbacks have an initial C<struct ev_loop *> argument.	2997	functions and callbacks have an initial C<struct ev_loop *> argument.
2633		2998
2634	To make it easier to write programs that cope with either variant, the	2999	To make it easier to write programs that cope with either variant, the
2635	following macros are defined:	3000	following macros are defined:
…		…
2640		3005
2641	This provides the loop I<argument> for functions, if one is required ("ev	3006	This provides the loop I<argument> for functions, if one is required ("ev
2642	loop argument"). The C<EV_A> form is used when this is the sole argument,	3007	loop argument"). The C<EV_A> form is used when this is the sole argument,
2643	C<EV_A_> is used when other arguments are following. Example:	3008	C<EV_A_> is used when other arguments are following. Example:
2644		3009
2645	ev_unref (EV_A);	3010	ev_unref (EV_A);
2646	ev_timer_add (EV_A_ watcher);	3011	ev_timer_add (EV_A_ watcher);
2647	ev_loop (EV_A_ 0);	3012	ev_loop (EV_A_ 0);
2648		3013
2649	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3014	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2650	which is often provided by the following macro.	3015	which is often provided by the following macro.
2651		3016
2652	=item C<EV_P>, C<EV_P_>	3017	=item C<EV_P>, C<EV_P_>
2653		3018
2654	This provides the loop I<parameter> for functions, if one is required ("ev	3019	This provides the loop I<parameter> for functions, if one is required ("ev
2655	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3020	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2656	C<EV_P_> is used when other parameters are following. Example:	3021	C<EV_P_> is used when other parameters are following. Example:
2657		3022
2658	// this is how ev_unref is being declared	3023	// this is how ev_unref is being declared
2659	static void ev_unref (EV_P);	3024	static void ev_unref (EV_P);
2660		3025
2661	// this is how you can declare your typical callback	3026	// this is how you can declare your typical callback
2662	static void cb (EV_P_ ev_timer *w, int revents)	3027	static void cb (EV_P_ ev_timer *w, int revents)
2663		3028
2664	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3029	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2665	suitable for use with C<EV_A>.	3030	suitable for use with C<EV_A>.
2666		3031
2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3032	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2683		3048
2684	Example: Declare and initialise a check watcher, utilising the above	3049	Example: Declare and initialise a check watcher, utilising the above
2685	macros so it will work regardless of whether multiple loops are supported	3050	macros so it will work regardless of whether multiple loops are supported
2686	or not.	3051	or not.
2687		3052
2688	static void	3053	static void
2689	check_cb (EV_P_ ev_timer *w, int revents)	3054	check_cb (EV_P_ ev_timer *w, int revents)
2690	{	3055	{
2691	ev_check_stop (EV_A_ w);	3056	ev_check_stop (EV_A_ w);
2692	}	3057	}
2693		3058
2694	ev_check check;	3059	ev_check check;
2695	ev_check_init (&check, check_cb);	3060	ev_check_init (&check, check_cb);
2696	ev_check_start (EV_DEFAULT_ &check);	3061	ev_check_start (EV_DEFAULT_ &check);
2697	ev_loop (EV_DEFAULT_ 0);	3062	ev_loop (EV_DEFAULT_ 0);
2698		3063
2699	=head1 EMBEDDING	3064	=head1 EMBEDDING
2700		3065
2701	Libev can (and often is) directly embedded into host	3066	Libev can (and often is) directly embedded into host
2702	applications. Examples of applications that embed it include the Deliantra	3067	applications. Examples of applications that embed it include the Deliantra
…		…
2709	libev somewhere in your source tree).	3074	libev somewhere in your source tree).
2710		3075
2711	=head2 FILESETS	3076	=head2 FILESETS
2712		3077
2713	Depending on what features you need you need to include one or more sets of files	3078	Depending on what features you need you need to include one or more sets of files
2714	in your app.	3079	in your application.
2715		3080
2716	=head3 CORE EVENT LOOP	3081	=head3 CORE EVENT LOOP
2717		3082
2718	To include only the libev core (all the C<ev_*> functions), with manual	3083	To include only the libev core (all the C<ev_*> functions), with manual
2719	configuration (no autoconf):	3084	configuration (no autoconf):
2720		3085
2721	#define EV_STANDALONE 1	3086	#define EV_STANDALONE 1
2722	#include "ev.c"	3087	#include "ev.c"
2723		3088
2724	This will automatically include F<ev.h>, too, and should be done in a	3089	This will automatically include F<ev.h>, too, and should be done in a
2725	single C source file only to provide the function implementations. To use	3090	single C source file only to provide the function implementations. To use
2726	it, do the same for F<ev.h> in all files wishing to use this API (best	3091	it, do the same for F<ev.h> in all files wishing to use this API (best
2727	done by writing a wrapper around F<ev.h> that you can include instead and	3092	done by writing a wrapper around F<ev.h> that you can include instead and
2728	where you can put other configuration options):	3093	where you can put other configuration options):
2729		3094
2730	#define EV_STANDALONE 1	3095	#define EV_STANDALONE 1
2731	#include "ev.h"	3096	#include "ev.h"
2732		3097
2733	Both header files and implementation files can be compiled with a C++	3098	Both header files and implementation files can be compiled with a C++
2734	compiler (at least, thats a stated goal, and breakage will be treated	3099	compiler (at least, that's a stated goal, and breakage will be treated
2735	as a bug).	3100	as a bug).
2736		3101
2737	You need the following files in your source tree, or in a directory	3102	You need the following files in your source tree, or in a directory
2738	in your include path (e.g. in libev/ when using -Ilibev):	3103	in your include path (e.g. in libev/ when using -Ilibev):
2739		3104
2740	ev.h	3105	ev.h
2741	ev.c	3106	ev.c
2742	ev_vars.h	3107	ev_vars.h
2743	ev_wrap.h	3108	ev_wrap.h
2744		3109
2745	ev_win32.c required on win32 platforms only	3110	ev_win32.c required on win32 platforms only
2746		3111
2747	ev_select.c only when select backend is enabled (which is enabled by default)	3112	ev_select.c only when select backend is enabled (which is enabled by default)
2748	ev_poll.c only when poll backend is enabled (disabled by default)	3113	ev_poll.c only when poll backend is enabled (disabled by default)
2749	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3114	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2750	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3115	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2751	ev_port.c only when the solaris port backend is enabled (disabled by default)	3116	ev_port.c only when the solaris port backend is enabled (disabled by default)
2752		3117
2753	F<ev.c> includes the backend files directly when enabled, so you only need	3118	F<ev.c> includes the backend files directly when enabled, so you only need
2754	to compile this single file.	3119	to compile this single file.
2755		3120
2756	=head3 LIBEVENT COMPATIBILITY API	3121	=head3 LIBEVENT COMPATIBILITY API
2757		3122
2758	To include the libevent compatibility API, also include:	3123	To include the libevent compatibility API, also include:
2759		3124
2760	#include "event.c"	3125	#include "event.c"
2761		3126
2762	in the file including F<ev.c>, and:	3127	in the file including F<ev.c>, and:
2763		3128
2764	#include "event.h"	3129	#include "event.h"
2765		3130
2766	in the files that want to use the libevent API. This also includes F<ev.h>.	3131	in the files that want to use the libevent API. This also includes F<ev.h>.
2767		3132
2768	You need the following additional files for this:	3133	You need the following additional files for this:
2769		3134
2770	event.h	3135	event.h
2771	event.c	3136	event.c
2772		3137
2773	=head3 AUTOCONF SUPPORT	3138	=head3 AUTOCONF SUPPORT
2774		3139
2775	Instead of using C<EV_STANDALONE=1> and providing your config in	3140	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2776	whatever way you want, you can also C<m4_include([libev.m4])> in your	3141	whatever way you want, you can also C<m4_include([libev.m4])> in your
2777	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3142	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2778	include F<config.h> and configure itself accordingly.	3143	include F<config.h> and configure itself accordingly.
2779		3144
2780	For this of course you need the m4 file:	3145	For this of course you need the m4 file:
2781		3146
2782	libev.m4	3147	libev.m4
2783		3148
2784	=head2 PREPROCESSOR SYMBOLS/MACROS	3149	=head2 PREPROCESSOR SYMBOLS/MACROS
2785		3150
2786	Libev can be configured via a variety of preprocessor symbols you have to	3151	Libev can be configured via a variety of preprocessor symbols you have to
2787	define before including any of its files. The default in the absense of	3152	define before including any of its files. The default in the absence of
2788	autoconf is noted for every option.	3153	autoconf is documented for every option.
2789		3154
2790	=over 4	3155	=over 4
2791		3156
2792	=item EV_STANDALONE	3157	=item EV_STANDALONE
2793		3158
…		…
2798	F<event.h> that are not directly supported by the libev core alone.	3163	F<event.h> that are not directly supported by the libev core alone.
2799		3164
2800	=item EV_USE_MONOTONIC	3165	=item EV_USE_MONOTONIC
2801		3166
2802	If defined to be C<1>, libev will try to detect the availability of the	3167	If defined to be C<1>, libev will try to detect the availability of the
2803	monotonic clock option at both compiletime and runtime. Otherwise no use	3168	monotonic clock option at both compile time and runtime. Otherwise no use
2804	of the monotonic clock option will be attempted. If you enable this, you	3169	of the monotonic clock option will be attempted. If you enable this, you
2805	usually have to link against librt or something similar. Enabling it when	3170	usually have to link against librt or something similar. Enabling it when
2806	the functionality isn't available is safe, though, although you have	3171	the functionality isn't available is safe, though, although you have
2807	to make sure you link against any libraries where the C<clock_gettime>	3172	to make sure you link against any libraries where the C<clock_gettime>
2808	function is hiding in (often F<-lrt>).	3173	function is hiding in (often F<-lrt>).
2809		3174
2810	=item EV_USE_REALTIME	3175	=item EV_USE_REALTIME
2811		3176
2812	If defined to be C<1>, libev will try to detect the availability of the	3177	If defined to be C<1>, libev will try to detect the availability of the
2813	realtime clock option at compiletime (and assume its availability at	3178	real-time clock option at compile time (and assume its availability at
2814	runtime if successful). Otherwise no use of the realtime clock option will	3179	runtime if successful). Otherwise no use of the real-time clock option will
2815	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3180	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2816	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3181	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2817	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3182	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2818		3183
2819	=item EV_USE_NANOSLEEP	3184	=item EV_USE_NANOSLEEP
…		…
2830	2.7 or newer, otherwise disabled.	3195	2.7 or newer, otherwise disabled.
2831		3196
2832	=item EV_USE_SELECT	3197	=item EV_USE_SELECT
2833		3198
2834	If undefined or defined to be C<1>, libev will compile in support for the	3199	If undefined or defined to be C<1>, libev will compile in support for the
2835	C<select>(2) backend. No attempt at autodetection will be done: if no	3200	C<select>(2) backend. No attempt at auto-detection will be done: if no
2836	other method takes over, select will be it. Otherwise the select backend	3201	other method takes over, select will be it. Otherwise the select backend
2837	will not be compiled in.	3202	will not be compiled in.
2838		3203
2839	=item EV_SELECT_USE_FD_SET	3204	=item EV_SELECT_USE_FD_SET
2840		3205
2841	If defined to C<1>, then the select backend will use the system C<fd_set>	3206	If defined to C<1>, then the select backend will use the system C<fd_set>
2842	structure. This is useful if libev doesn't compile due to a missing	3207	structure. This is useful if libev doesn't compile due to a missing
2843	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3208	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2844	exotic systems. This usually limits the range of file descriptors to some	3209	exotic systems. This usually limits the range of file descriptors to some
2845	low limit such as 1024 or might have other limitations (winsocket only	3210	low limit such as 1024 or might have other limitations (winsocket only
2846	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3211	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2847	influence the size of the C<fd_set> used.	3212	influence the size of the C<fd_set> used.
2848		3213
…		…
2897	otherwise another method will be used as fallback. This is the preferred	3262	otherwise another method will be used as fallback. This is the preferred
2898	backend for Solaris 10 systems.	3263	backend for Solaris 10 systems.
2899		3264
2900	=item EV_USE_DEVPOLL	3265	=item EV_USE_DEVPOLL
2901		3266
2902	reserved for future expansion, works like the USE symbols above.	3267	Reserved for future expansion, works like the USE symbols above.
2903		3268
2904	=item EV_USE_INOTIFY	3269	=item EV_USE_INOTIFY
2905		3270
2906	If defined to be C<1>, libev will compile in support for the Linux inotify	3271	If defined to be C<1>, libev will compile in support for the Linux inotify
2907	interface to speed up C<ev_stat> watchers. Its actual availability will	3272	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2914	access is atomic with respect to other threads or signal contexts. No such	3279	access is atomic with respect to other threads or signal contexts. No such
2915	type is easily found in the C language, so you can provide your own type	3280	type is easily found in the C language, so you can provide your own type
2916	that you know is safe for your purposes. It is used both for signal handler "locking"	3281	that you know is safe for your purposes. It is used both for signal handler "locking"
2917	as well as for signal and thread safety in C<ev_async> watchers.	3282	as well as for signal and thread safety in C<ev_async> watchers.
2918		3283
2919	In the absense of this define, libev will use C<sig_atomic_t volatile>	3284	In the absence of this define, libev will use C<sig_atomic_t volatile>
2920	(from F<signal.h>), which is usually good enough on most platforms.	3285	(from F<signal.h>), which is usually good enough on most platforms.
2921		3286
2922	=item EV_H	3287	=item EV_H
2923		3288
2924	The name of the F<ev.h> header file used to include it. The default if	3289	The name of the F<ev.h> header file used to include it. The default if
…		…
2963	When doing priority-based operations, libev usually has to linearly search	3328	When doing priority-based operations, libev usually has to linearly search
2964	all the priorities, so having many of them (hundreds) uses a lot of space	3329	all the priorities, so having many of them (hundreds) uses a lot of space
2965	and time, so using the defaults of five priorities (-2 .. +2) is usually	3330	and time, so using the defaults of five priorities (-2 .. +2) is usually
2966	fine.	3331	fine.
2967		3332
2968	If your embedding app does not need any priorities, defining these both to	3333	If your embedding application does not need any priorities, defining these
2969	C<0> will save some memory and cpu.	3334	both to C<0> will save some memory and CPU.
2970		3335
2971	=item EV_PERIODIC_ENABLE	3336	=item EV_PERIODIC_ENABLE
2972		3337
2973	If undefined or defined to be C<1>, then periodic timers are supported. If	3338	If undefined or defined to be C<1>, then periodic timers are supported. If
2974	defined to be C<0>, then they are not. Disabling them saves a few kB of	3339	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2981	code.	3346	code.
2982		3347
2983	=item EV_EMBED_ENABLE	3348	=item EV_EMBED_ENABLE
2984		3349
2985	If undefined or defined to be C<1>, then embed watchers are supported. If	3350	If undefined or defined to be C<1>, then embed watchers are supported. If
2986	defined to be C<0>, then they are not.	3351	defined to be C<0>, then they are not. Embed watchers rely on most other
		3352	watcher types, which therefore must not be disabled.
2987		3353
2988	=item EV_STAT_ENABLE	3354	=item EV_STAT_ENABLE
2989		3355
2990	If undefined or defined to be C<1>, then stat watchers are supported. If	3356	If undefined or defined to be C<1>, then stat watchers are supported. If
2991	defined to be C<0>, then they are not.	3357	defined to be C<0>, then they are not.
…		…
3002		3368
3003	=item EV_MINIMAL	3369	=item EV_MINIMAL
3004		3370
3005	If you need to shave off some kilobytes of code at the expense of some	3371	If you need to shave off some kilobytes of code at the expense of some
3006	speed, define this symbol to C<1>. Currently this is used to override some	3372	speed, define this symbol to C<1>. Currently this is used to override some
3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3373	inlining decisions, saves roughly 30% code size on amd64. It also selects a
3008	much smaller 2-heap for timer management over the default 4-heap.	3374	much smaller 2-heap for timer management over the default 4-heap.
3009		3375
3010	=item EV_PID_HASHSIZE	3376	=item EV_PID_HASHSIZE
3011		3377
3012	C<ev_child> watchers use a small hash table to distribute workload by	3378	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3023	two).	3389	two).
3024		3390
3025	=item EV_USE_4HEAP	3391	=item EV_USE_4HEAP
3026		3392
3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3028	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3394	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3029	to C<1>. The 4-heap uses more complicated (longer) code but has	3395	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3030	noticably faster performance with many (thousands) of watchers.	3396	faster performance with many (thousands) of watchers.
3031		3397
3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3398	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3033	(disabled).	3399	(disabled).
3034		3400
3035	=item EV_HEAP_CACHE_AT	3401	=item EV_HEAP_CACHE_AT
3036		3402
3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3403	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3038	timer and periodics heap, libev can cache the timestamp (I<at>) within	3404	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3039	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3405	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3040	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3406	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3041	but avoids random read accesses on heap changes. This improves performance	3407	but avoids random read accesses on heap changes. This improves performance
3042	noticably with with many (hundreds) of watchers.	3408	noticeably with many (hundreds) of watchers.
3043		3409
3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3410	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3045	(disabled).	3411	(disabled).
3046		3412
3047	=item EV_VERIFY	3413	=item EV_VERIFY
…		…
3053	called once per loop, which can slow down libev. If set to C<3>, then the	3419	called once per loop, which can slow down libev. If set to C<3>, then the
3054	verification code will be called very frequently, which will slow down	3420	verification code will be called very frequently, which will slow down
3055	libev considerably.	3421	libev considerably.
3056		3422
3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3423	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3058	C<0.>	3424	C<0>.
3059		3425
3060	=item EV_COMMON	3426	=item EV_COMMON
3061		3427
3062	By default, all watchers have a C<void *data> member. By redefining	3428	By default, all watchers have a C<void *data> member. By redefining
3063	this macro to a something else you can include more and other types of	3429	this macro to a something else you can include more and other types of
3064	members. You have to define it each time you include one of the files,	3430	members. You have to define it each time you include one of the files,
3065	though, and it must be identical each time.	3431	though, and it must be identical each time.
3066		3432
3067	For example, the perl EV module uses something like this:	3433	For example, the perl EV module uses something like this:
3068		3434
3069	#define EV_COMMON \	3435	#define EV_COMMON \
3070	SV *self; /* contains this struct */ \	3436	SV *self; /* contains this struct */ \
3071	SV *cb_sv, *fh /* note no trailing ";" */	3437	SV *cb_sv, *fh /* note no trailing ";" */
3072		3438
3073	=item EV_CB_DECLARE (type)	3439	=item EV_CB_DECLARE (type)
3074		3440
3075	=item EV_CB_INVOKE (watcher, revents)	3441	=item EV_CB_INVOKE (watcher, revents)
3076		3442
…		…
3081	definition and a statement, respectively. See the F<ev.h> header file for	3447	definition and a statement, respectively. See the F<ev.h> header file for
3082	their default definitions. One possible use for overriding these is to	3448	their default definitions. One possible use for overriding these is to
3083	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3449	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3084	method calls instead of plain function calls in C++.	3450	method calls instead of plain function calls in C++.
3085		3451
		3452	=back
		3453
3086	=head2 EXPORTED API SYMBOLS	3454	=head2 EXPORTED API SYMBOLS
3087		3455
3088	If you need to re-export the API (e.g. via a dll) and you need a list of	3456	If you need to re-export the API (e.g. via a DLL) and you need a list of
3089	exported symbols, you can use the provided F<Symbol.*> files which list	3457	exported symbols, you can use the provided F<Symbol.*> files which list
3090	all public symbols, one per line:	3458	all public symbols, one per line:
3091		3459
3092	Symbols.ev for libev proper	3460	Symbols.ev for libev proper
3093	Symbols.event for the libevent emulation	3461	Symbols.event for the libevent emulation
3094		3462
3095	This can also be used to rename all public symbols to avoid clashes with	3463	This can also be used to rename all public symbols to avoid clashes with
3096	multiple versions of libev linked together (which is obviously bad in	3464	multiple versions of libev linked together (which is obviously bad in
3097	itself, but sometimes it is inconvinient to avoid this).	3465	itself, but sometimes it is inconvenient to avoid this).
3098		3466
3099	A sed command like this will create wrapper C<#define>'s that you need to	3467	A sed command like this will create wrapper C<#define>'s that you need to
3100	include before including F<ev.h>:	3468	include before including F<ev.h>:
3101		3469
3102	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3470	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3119	file.	3487	file.
3120		3488
3121	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3489	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3122	that everybody includes and which overrides some configure choices:	3490	that everybody includes and which overrides some configure choices:
3123		3491
3124	#define EV_MINIMAL 1	3492	#define EV_MINIMAL 1
3125	#define EV_USE_POLL 0	3493	#define EV_USE_POLL 0
3126	#define EV_MULTIPLICITY 0	3494	#define EV_MULTIPLICITY 0
3127	#define EV_PERIODIC_ENABLE 0	3495	#define EV_PERIODIC_ENABLE 0
3128	#define EV_STAT_ENABLE 0	3496	#define EV_STAT_ENABLE 0
3129	#define EV_FORK_ENABLE 0	3497	#define EV_FORK_ENABLE 0
3130	#define EV_CONFIG_H <config.h>	3498	#define EV_CONFIG_H <config.h>
3131	#define EV_MINPRI 0	3499	#define EV_MINPRI 0
3132	#define EV_MAXPRI 0	3500	#define EV_MAXPRI 0
3133		3501
3134	#include "ev++.h"	3502	#include "ev++.h"
3135		3503
3136	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3504	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3137		3505
3138	#include "ev_cpp.h"	3506	#include "ev_cpp.h"
3139	#include "ev.c"	3507	#include "ev.c"
3140		3508
		3509	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3141		3510
3142	=head1 THREADS AND COROUTINES	3511	=head2 THREADS AND COROUTINES
3143		3512
3144	=head2 THREADS	3513	=head3 THREADS
3145		3514
3146	Libev itself is completely threadsafe, but it uses no locking. This	3515	All libev functions are reentrant and thread-safe unless explicitly
		3516	documented otherwise, but libev implements no locking itself. This means
3147	means that you can use as many loops as you want in parallel, as long as	3517	that you can use as many loops as you want in parallel, as long as there
3148	only one thread ever calls into one libev function with the same loop	3518	are no concurrent calls into any libev function with the same loop
3149	parameter.	3519	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3520	of course): libev guarantees that different event loops share no data
		3521	structures that need any locking.
3150		3522
3151	Or put differently: calls with different loop parameters can be done in	3523	Or to put it differently: calls with different loop parameters can be done
3152	parallel from multiple threads, calls with the same loop parameter must be	3524	concurrently from multiple threads, calls with the same loop parameter
3153	done serially (but can be done from different threads, as long as only one	3525	must be done serially (but can be done from different threads, as long as
3154	thread ever is inside a call at any point in time, e.g. by using a mutex	3526	only one thread ever is inside a call at any point in time, e.g. by using
3155	per loop).	3527	a mutex per loop).
3156		3528
3157	If you want to know which design is best for your problem, then I cannot	3529	Specifically to support threads (and signal handlers), libev implements
		3530	so-called C<ev_async> watchers, which allow some limited form of
		3531	concurrency on the same event loop, namely waking it up "from the
		3532	outside".
		3533
		3534	If you want to know which design (one loop, locking, or multiple loops
		3535	without or something else still) is best for your problem, then I cannot
3158	help you but by giving some generic advice:	3536	help you, but here is some generic advice:
3159		3537
3160	=over 4	3538	=over 4
3161		3539
3162	=item * most applications have a main thread: use the default libev loop	3540	=item * most applications have a main thread: use the default libev loop
3163	in that thread, or create a seperate thread running only the default loop.	3541	in that thread, or create a separate thread running only the default loop.
3164		3542
3165	This helps integrating other libraries or software modules that use libev	3543	This helps integrating other libraries or software modules that use libev
3166	themselves and don't care/know about threading.	3544	themselves and don't care/know about threading.
3167		3545
3168	=item * one loop per thread is usually a good model.	3546	=item * one loop per thread is usually a good model.
3169		3547
3170	Doing this is almost never wrong, sometimes a better-performance model	3548	Doing this is almost never wrong, sometimes a better-performance model
3171	exists, but it is always a good start.	3549	exists, but it is always a good start.
3172		3550
3173	=item * other models exist, such as the leader/follower pattern, where one	3551	=item * other models exist, such as the leader/follower pattern, where one
3174	loop is handed through multiple threads in a kind of round-robbin fashion.	3552	loop is handed through multiple threads in a kind of round-robin fashion.
3175		3553
3176	Chosing a model is hard - look around, learn, know that usually you cna do	3554	Choosing a model is hard - look around, learn, know that usually you can do
3177	better than you currently do :-)	3555	better than you currently do :-)
3178		3556
3179	=item * often you need to talk to some other thread which blocks in the	3557	=item * often you need to talk to some other thread which blocks in the
		3558	event loop.
		3559
3180	event loop - C<ev_async> watchers can be used to wake them up from other	3560	C<ev_async> watchers can be used to wake them up from other threads safely
3181	threads safely (or from signal contexts...).	3561	(or from signal contexts...).
		3562
		3563	An example use would be to communicate signals or other events that only
		3564	work in the default loop by registering the signal watcher with the
		3565	default loop and triggering an C<ev_async> watcher from the default loop
		3566	watcher callback into the event loop interested in the signal.
3182		3567
3183	=back	3568	=back
3184		3569
3185	=head2 COROUTINES	3570	=head3 COROUTINES
3186		3571
3187	Libev is much more accomodating to coroutines ("cooperative threads"):	3572	Libev is very accommodating to coroutines ("cooperative threads"):
3188	libev fully supports nesting calls to it's functions from different	3573	libev fully supports nesting calls to its functions from different
3189	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3574	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3190	different coroutines and switch freely between both coroutines running the	3575	different coroutines, and switch freely between both coroutines running the
3191	loop, as long as you don't confuse yourself). The only exception is that	3576	loop, as long as you don't confuse yourself). The only exception is that
3192	you must not do this from C<ev_periodic> reschedule callbacks.	3577	you must not do this from C<ev_periodic> reschedule callbacks.
3193		3578
3194	Care has been invested into making sure that libev does not keep local	3579	Care has been taken to ensure that libev does not keep local state inside
3195	state inside C<ev_loop>, and other calls do not usually allow coroutine	3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3196	switches.	3581	they do not call any callbacks.
3197		3582
		3583	=head2 COMPILER WARNINGS
3198		3584
3199	=head1 COMPLEXITIES	3585	Depending on your compiler and compiler settings, you might get no or a
		3586	lot of warnings when compiling libev code. Some people are apparently
		3587	scared by this.
3200		3588
3201	In this section the complexities of (many of) the algorithms used inside	3589	However, these are unavoidable for many reasons. For one, each compiler
3202	libev will be explained. For complexity discussions about backends see the	3590	has different warnings, and each user has different tastes regarding
3203	documentation for C<ev_default_init>.	3591	warning options. "Warn-free" code therefore cannot be a goal except when
		3592	targeting a specific compiler and compiler-version.
3204		3593
3205	All of the following are about amortised time: If an array needs to be	3594	Another reason is that some compiler warnings require elaborate
3206	extended, libev needs to realloc and move the whole array, but this	3595	workarounds, or other changes to the code that make it less clear and less
3207	happens asymptotically never with higher number of elements, so O(1) might	3596	maintainable.
3208	mean it might do a lengthy realloc operation in rare cases, but on average
3209	it is much faster and asymptotically approaches constant time.
3210		3597
3211	=over 4	3598	And of course, some compiler warnings are just plain stupid, or simply
		3599	wrong (because they don't actually warn about the condition their message
		3600	seems to warn about). For example, certain older gcc versions had some
		3601	warnings that resulted an extreme number of false positives. These have
		3602	been fixed, but some people still insist on making code warn-free with
		3603	such buggy versions.
3212		3604
3213	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3605	While libev is written to generate as few warnings as possible,
		3606	"warn-free" code is not a goal, and it is recommended not to build libev
		3607	with any compiler warnings enabled unless you are prepared to cope with
		3608	them (e.g. by ignoring them). Remember that warnings are just that:
		3609	warnings, not errors, or proof of bugs.
3214		3610
3215	This means that, when you have a watcher that triggers in one hour and
3216	there are 100 watchers that would trigger before that then inserting will
3217	have to skip roughly seven (C<ld 100>) of these watchers.
3218		3611
3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3612	=head2 VALGRIND
3220		3613
3221	That means that changing a timer costs less than removing/adding them	3614	Valgrind has a special section here because it is a popular tool that is
3222	as only the relative motion in the event queue has to be paid for.	3615	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3223		3616
3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3617	If you think you found a bug (memory leak, uninitialised data access etc.)
		3618	in libev, then check twice: If valgrind reports something like:
3225		3619
3226	These just add the watcher into an array or at the head of a list.	3620	==2274== definitely lost: 0 bytes in 0 blocks.
		3621	==2274== possibly lost: 0 bytes in 0 blocks.
		3622	==2274== still reachable: 256 bytes in 1 blocks.
3227		3623
3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3624	Then there is no memory leak, just as memory accounted to global variables
		3625	is not a memleak - the memory is still being referenced, and didn't leak.
3229		3626
3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3627	Similarly, under some circumstances, valgrind might report kernel bugs
		3628	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3629	although an acceptable workaround has been found here), or it might be
		3630	confused.
3231		3631
3232	These watchers are stored in lists then need to be walked to find the	3632	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3233	correct watcher to remove. The lists are usually short (you don't usually	3633	make it into some kind of religion.
3234	have many watchers waiting for the same fd or signal).
3235		3634
3236	=item Finding the next timer in each loop iteration: O(1)	3635	If you are unsure about something, feel free to contact the mailing list
		3636	with the full valgrind report and an explanation on why you think this
		3637	is a bug in libev (best check the archives, too :). However, don't be
		3638	annoyed when you get a brisk "this is no bug" answer and take the chance
		3639	of learning how to interpret valgrind properly.
3237		3640
3238	By virtue of using a binary or 4-heap, the next timer is always found at a	3641	If you need, for some reason, empty reports from valgrind for your project
3239	fixed position in the storage array.	3642	I suggest using suppression lists.
3240		3643
3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3242		3644
3243	A change means an I/O watcher gets started or stopped, which requires	3645	=head1 PORTABILITY NOTES
3244	libev to recalculate its status (and possibly tell the kernel, depending
3245	on backend and wether C<ev_io_set> was used).
3246		3646
3247	=item Activating one watcher (putting it into the pending state): O(1)	3647	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3248
3249	=item Priority handling: O(number_of_priorities)
3250
3251	Priorities are implemented by allocating some space for each
3252	priority. When doing priority-based operations, libev usually has to
3253	linearly search all the priorities, but starting/stopping and activating
3254	watchers becomes O(1) w.r.t. priority handling.
3255
3256	=item Sending an ev_async: O(1)
3257
3258	=item Processing ev_async_send: O(number_of_async_watchers)
3259
3260	=item Processing signals: O(max_signal_number)
3261
3262	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3263	calls in the current loop iteration. Checking for async and signal events
3264	involves iterating over all running async watchers or all signal numbers.
3265
3266	=back
3267
3268
3269	=head1 Win32 platform limitations and workarounds
3270		3648
3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3649	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3272	requires, and its I/O model is fundamentally incompatible with the POSIX	3650	requires, and its I/O model is fundamentally incompatible with the POSIX
3273	model. Libev still offers limited functionality on this platform in	3651	model. Libev still offers limited functionality on this platform in
3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3652	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3281	way (note also that glib is the slowest event library known to man).	3659	way (note also that glib is the slowest event library known to man).
3282		3660
3283	There is no supported compilation method available on windows except	3661	There is no supported compilation method available on windows except
3284	embedding it into other applications.	3662	embedding it into other applications.
3285		3663
		3664	Not a libev limitation but worth mentioning: windows apparently doesn't
		3665	accept large writes: instead of resulting in a partial write, windows will
		3666	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3667	so make sure you only write small amounts into your sockets (less than a
		3668	megabyte seems safe, but this apparently depends on the amount of memory
		3669	available).
		3670
3286	Due to the many, low, and arbitrary limits on the win32 platform and	3671	Due to the many, low, and arbitrary limits on the win32 platform and
3287	the abysmal performance of winsockets, using a large number of sockets	3672	the abysmal performance of winsockets, using a large number of sockets
3288	is not recommended (and not reasonable). If your program needs to use	3673	is not recommended (and not reasonable). If your program needs to use
3289	more than a hundred or so sockets, then likely it needs to use a totally	3674	more than a hundred or so sockets, then likely it needs to use a totally
3290	different implementation for windows, as libev offers the POSIX readiness	3675	different implementation for windows, as libev offers the POSIX readiness
3291	notification model, which cannot be implemented efficiently on windows	3676	notification model, which cannot be implemented efficiently on windows
3292	(microsoft monopoly games).	3677	(Microsoft monopoly games).
		3678
		3679	A typical way to use libev under windows is to embed it (see the embedding
		3680	section for details) and use the following F<evwrap.h> header file instead
		3681	of F<ev.h>:
		3682
		3683	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3684	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3685
		3686	#include "ev.h"
		3687
		3688	And compile the following F<evwrap.c> file into your project (make sure
		3689	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3690
		3691	#include "evwrap.h"
		3692	#include "ev.c"
3293		3693
3294	=over 4	3694	=over 4
3295		3695
3296	=item The winsocket select function	3696	=item The winsocket select function
3297		3697
3298	The winsocket C<select> function doesn't follow POSIX in that it requires	3698	The winsocket C<select> function doesn't follow POSIX in that it
3299	socket I<handles> and not socket I<file descriptors>. This makes select	3699	requires socket I<handles> and not socket I<file descriptors> (it is
3300	very inefficient, and also requires a mapping from file descriptors	3700	also extremely buggy). This makes select very inefficient, and also
3301	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3701	requires a mapping from file descriptors to socket handles (the Microsoft
3302	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3702	C runtime provides the function C<_open_osfhandle> for this). See the
3303	symbols for more info.	3703	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3704	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3304		3705
3305	The configuration for a "naked" win32 using the microsoft runtime	3706	The configuration for a "naked" win32 using the Microsoft runtime
3306	libraries and raw winsocket select is:	3707	libraries and raw winsocket select is:
3307		3708
3308	#define EV_USE_SELECT 1	3709	#define EV_USE_SELECT 1
3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3710	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3310		3711
3311	Note that winsockets handling of fd sets is O(n), so you can easily get a	3712	Note that winsockets handling of fd sets is O(n), so you can easily get a
3312	complexity in the O(n²) range when using win32.	3713	complexity in the O(n²) range when using win32.
3313		3714
3314	=item Limited number of file descriptors	3715	=item Limited number of file descriptors
3315		3716
3316	Windows has numerous arbitrary (and low) limits on things.	3717	Windows has numerous arbitrary (and low) limits on things.
3317		3718
3318	Early versions of winsocket's select only supported waiting for a maximum	3719	Early versions of winsocket's select only supported waiting for a maximum
3319	of C<64> handles (probably owning to the fact that all windows kernels	3720	of C<64> handles (probably owning to the fact that all windows kernels
3320	can only wait for C<64> things at the same time internally; microsoft	3721	can only wait for C<64> things at the same time internally; Microsoft
3321	recommends spawning a chain of threads and wait for 63 handles and the	3722	recommends spawning a chain of threads and wait for 63 handles and the
3322	previous thread in each. Great).	3723	previous thread in each. Great).
3323		3724
3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3725	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3325	to some high number (e.g. C<2048>) before compiling the winsocket select	3726	to some high number (e.g. C<2048>) before compiling the winsocket select
3326	call (which might be in libev or elsewhere, for example, perl does its own	3727	call (which might be in libev or elsewhere, for example, perl does its own
3327	select emulation on windows).	3728	select emulation on windows).
3328		3729
3329	Another limit is the number of file descriptors in the microsoft runtime	3730	Another limit is the number of file descriptors in the Microsoft runtime
3330	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3731	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3331	or something like this inside microsoft). You can increase this by calling	3732	or something like this inside Microsoft). You can increase this by calling
3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3733	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3333	arbitrary limit), but is broken in many versions of the microsoft runtime	3734	arbitrary limit), but is broken in many versions of the Microsoft runtime
3334	libraries.	3735	libraries.
3335		3736
3336	This might get you to about C<512> or C<2048> sockets (depending on	3737	This might get you to about C<512> or C<2048> sockets (depending on
3337	windows version and/or the phase of the moon). To get more, you need to	3738	windows version and/or the phase of the moon). To get more, you need to
3338	wrap all I/O functions and provide your own fd management, but the cost of	3739	wrap all I/O functions and provide your own fd management, but the cost of
3339	calling select (O(n²)) will likely make this unworkable.	3740	calling select (O(n²)) will likely make this unworkable.
3340		3741
3341	=back	3742	=back
3342		3743
3343
3344	=head1 PORTABILITY REQUIREMENTS	3744	=head2 PORTABILITY REQUIREMENTS
3345		3745
3346	In addition to a working ISO-C implementation, libev relies on a few	3746	In addition to a working ISO-C implementation and of course the
3347	additional extensions:	3747	backend-specific APIs, libev relies on a few additional extensions:
3348		3748
3349	=over 4	3749	=over 4
3350		3750
		3751	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3752	calling conventions regardless of C<ev_watcher_type *>.
		3753
		3754	Libev assumes not only that all watcher pointers have the same internal
		3755	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3756	assumes that the same (machine) code can be used to call any watcher
		3757	callback: The watcher callbacks have different type signatures, but libev
		3758	calls them using an C<ev_watcher *> internally.
		3759
3351	=item C<sig_atomic_t volatile> must be thread-atomic as well	3760	=item C<sig_atomic_t volatile> must be thread-atomic as well
3352		3761
3353	The type C<sig_atomic_t volatile> (or whatever is defined as	3762	The type C<sig_atomic_t volatile> (or whatever is defined as
3354	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3763	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3355	threads. This is not part of the specification for C<sig_atomic_t>, but is	3764	threads. This is not part of the specification for C<sig_atomic_t>, but is
3356	believed to be sufficiently portable.	3765	believed to be sufficiently portable.
3357		3766
3358	=item C<sigprocmask> must work in a threaded environment	3767	=item C<sigprocmask> must work in a threaded environment
3359		3768
…		…
3368	except the initial one, and run the default loop in the initial thread as	3777	except the initial one, and run the default loop in the initial thread as
3369	well.	3778	well.
3370		3779
3371	=item C<long> must be large enough for common memory allocation sizes	3780	=item C<long> must be large enough for common memory allocation sizes
3372		3781
3373	To improve portability and simplify using libev, libev uses C<long>	3782	To improve portability and simplify its API, libev uses C<long> internally
3374	internally instead of C<size_t> when allocating its data structures. On	3783	instead of C<size_t> when allocating its data structures. On non-POSIX
3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3784	systems (Microsoft...) this might be unexpectedly low, but is still at
3376	is still at least 31 bits everywhere, which is enough for hundreds of	3785	least 31 bits everywhere, which is enough for hundreds of millions of
3377	millions of watchers.	3786	watchers.
3378		3787
3379	=item C<double> must hold a time value in seconds with enough accuracy	3788	=item C<double> must hold a time value in seconds with enough accuracy
3380		3789
3381	The type C<double> is used to represent timestamps. It is required to	3790	The type C<double> is used to represent timestamps. It is required to
3382	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3791	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3386	=back	3795	=back
3387		3796
3388	If you know of other additional requirements drop me a note.	3797	If you know of other additional requirements drop me a note.
3389		3798
3390		3799
3391	=head1 VALGRIND	3800	=head1 ALGORITHMIC COMPLEXITIES
3392		3801
3393	Valgrind has a special section here because it is a popular tool that is	3802	In this section the complexities of (many of) the algorithms used inside
3394	highly useful, but valgrind reports are very hard to interpret.	3803	libev will be documented. For complexity discussions about backends see
		3804	the documentation for C<ev_default_init>.
3395		3805
3396	If you think you found a bug (memory leak, uninitialised data access etc.)	3806	All of the following are about amortised time: If an array needs to be
3397	in libev, then check twice: If valgrind reports something like:	3807	extended, libev needs to realloc and move the whole array, but this
		3808	happens asymptotically rarer with higher number of elements, so O(1) might
		3809	mean that libev does a lengthy realloc operation in rare cases, but on
		3810	average it is much faster and asymptotically approaches constant time.
3398		3811
3399	==2274== definitely lost: 0 bytes in 0 blocks.	3812	=over 4
3400	==2274== possibly lost: 0 bytes in 0 blocks.
3401	==2274== still reachable: 256 bytes in 1 blocks.
3402		3813
3403	then there is no memory leak. Similarly, under some circumstances,	3814	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3404	valgrind might report kernel bugs as if it were a bug in libev, or it
3405	might be confused (it is a very good tool, but only a tool).
3406		3815
3407	If you are unsure about something, feel free to contact the mailing list	3816	This means that, when you have a watcher that triggers in one hour and
3408	with the full valgrind report and an explanation on why you think this is	3817	there are 100 watchers that would trigger before that, then inserting will
3409	a bug in libev. However, don't be annoyed when you get a brisk "this is	3818	have to skip roughly seven (C<ld 100>) of these watchers.
3410	no bug" answer and take the chance of learning how to interpret valgrind
3411	properly.
3412		3819
3413	If you need, for some reason, empty reports from valgrind for your project	3820	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3414	I suggest using suppression lists.	3821
		3822	That means that changing a timer costs less than removing/adding them,
		3823	as only the relative motion in the event queue has to be paid for.
		3824
		3825	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3826
		3827	These just add the watcher into an array or at the head of a list.
		3828
		3829	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3830
		3831	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3832
		3833	These watchers are stored in lists, so they need to be walked to find the
		3834	correct watcher to remove. The lists are usually short (you don't usually
		3835	have many watchers waiting for the same fd or signal: one is typical, two
		3836	is rare).
		3837
		3838	=item Finding the next timer in each loop iteration: O(1)
		3839
		3840	By virtue of using a binary or 4-heap, the next timer is always found at a
		3841	fixed position in the storage array.
		3842
		3843	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3844
		3845	A change means an I/O watcher gets started or stopped, which requires
		3846	libev to recalculate its status (and possibly tell the kernel, depending
		3847	on backend and whether C<ev_io_set> was used).
		3848
		3849	=item Activating one watcher (putting it into the pending state): O(1)
		3850
		3851	=item Priority handling: O(number_of_priorities)
		3852
		3853	Priorities are implemented by allocating some space for each
		3854	priority. When doing priority-based operations, libev usually has to
		3855	linearly search all the priorities, but starting/stopping and activating
		3856	watchers becomes O(1) with respect to priority handling.
		3857
		3858	=item Sending an ev_async: O(1)
		3859
		3860	=item Processing ev_async_send: O(number_of_async_watchers)
		3861
		3862	=item Processing signals: O(max_signal_number)
		3863
		3864	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3865	calls in the current loop iteration. Checking for async and signal events
		3866	involves iterating over all running async watchers or all signal numbers.
		3867
		3868	=back
3415		3869
3416		3870
3417	=head1 AUTHOR	3871	=head1 AUTHOR
3418		3872
3419	Marc Lehmann <libev@schmorp.de>.	3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3420		3874

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