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Revision 1.157 by root, Tue May 20 23:49:41 2008 UTC vs.
Revision 1.205 by root, Mon Oct 27 12:20:32 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
…		…
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 bes hared 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 syscalls are the most misdesigned of the more advanced
360	support for dup.	392	event mechanisms: probelsm include silently dropping events in some
		393	hard-to-detect cases, requiring a system call per fd change, no fork
		394	support, problems with dup and so on.
		395
		396	Epoll is also notoriously buggy - embedding epoll fds should work, but
		397	of course doesn't, and epoll just loves to report events for totally
		398	I<different> file descriptors (even already closed ones, so one cannot
		399	even remove them from the set) than registered in the set (especially
		400	on SMP systems). Libev tries to counter these spurious notifications by
		401	employing an additional generation counter and comparing that against the
		402	events to filter out spurious ones.
361		403
362	While stopping, setting and starting an I/O watcher in the same iteration	404	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	405	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	406	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	407	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	408	very well if you register events for both fds.
367		409
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
372	Best performance from this backend is achieved by not unregistering all	410	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.	411	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	412	i.e. keep at least one watcher active per fd at all times. Stopping and
		413	starting a watcher (without re-setting it) also usually doesn't cause
		414	extra overhead.
375		415
376	While nominally embeddeble in other event loops, this feature is broken in	416	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	417	all kernel versions tested so far.
378		418
		419	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		420	C<EVBACKEND_POLL>.
		421
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	422	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		423
381	Kqueue deserves special mention, as at the time of this writing, it	424	Kqueue deserves special mention, as at the time of this writing, it was
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	425	broken on all BSDs except NetBSD (usually it doesn't work reliably with
383	with anything but sockets and pipes, except on Darwin, where of course	426	anything but sockets and pipes, except on Darwin, where of course it's
384	it's completely useless). For this reason it's not being "autodetected"	427	completely useless). For this reason it's not being "auto-detected" unless
385	unless you explicitly specify it explicitly in the flags (i.e. using	428	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	429	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		430
389	You still can embed kqueue into a normal poll or select backend and use it	431	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	432	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.	433	the target platform). See C<ev_embed> watchers for more info.
392		434
393	It scales in the same way as the epoll backend, but the interface to the	435	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	436	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	437	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	438	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	439	two event changes per incident. Support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	440	drops fds silently in similarly hard-to-detect cases.
399		441
400	This backend usually performs well under most conditions.	442	This backend usually performs well under most conditions.
401		443
402	While nominally embeddable in other event loops, this doesn't work	444	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	445	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	446	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	447	(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	448	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	449	using it only for sockets.
		450
		451	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		452	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		453	C<NOTE_EOF>.
408		454
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	455	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		456
411	This is not implemented yet (and might never be, unless you send me an	457	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	458	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	462	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		463
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	464	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)).	465	it's really slow, but it still scales very well (O(active_fds)).
420		466
421	Please note that solaris event ports can deliver a lot of spurious	467	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	468	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	469	blocking when no data (or space) is available.
424		470
425	While this backend scales well, it requires one system call per active	471	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	472	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	473	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	474	might perform better.
429		475
430	On the positive side, ignoring the spurious readiness notifications, this	476	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	477	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	478	in all tests and is fully embeddable, which is a rare feat among the
		479	OS-specific backends.
		480
		481	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		482	C<EVBACKEND_POLL>.
433		483
434	=item C<EVBACKEND_ALL>	484	=item C<EVBACKEND_ALL>
435		485
436	Try all backends (even potentially broken ones that wouldn't be tried	486	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	487	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		489
440	It is definitely not recommended to use this flag.	490	It is definitely not recommended to use this flag.
441		491
442	=back	492	=back
443		493
444	If one or more of these are ored into the flags value, then only these	494	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	495	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.	496	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		497
448	The most typical usage is like this:	498	Example: This is the most typical usage.
449		499
450	if (!ev_default_loop (0))	500	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	501	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		502
453	Restrict libev to the select and poll backends, and do not allow	503	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	504	environment settings to be taken into account:
455		505
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	506	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		507
458	Use whatever libev has to offer, but make sure that kqueue is used if	508	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	509	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):	510	private event loop and only if you know the OS supports your types of
		511	fds):
461		512
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	513	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		514
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	515	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		516
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	517	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	518	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	523	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	524	default loop in the "main" or "initial" thread.
474		525
475	Example: Try to create a event loop that uses epoll and nothing else.	526	Example: Try to create a event loop that uses epoll and nothing else.
476		527
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	528	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	529	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	530	fatal ("no epoll found here, maybe it hides under your chair");
480		531
481	=item ev_default_destroy ()	532	=item ev_default_destroy ()
482		533
483	Destroys the default loop again (frees all memory and kernel state	534	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	535	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	536	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>	537	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	538	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	539	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	540	for example).
490		541
491	Note that certain global state, such as signal state, will not be freed by	542	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	543	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	544	as signal and child watchers) would need to be stopped manually.
494		545
495	In general it is not advisable to call this function except in the	546	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	547	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	548	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	549	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		574
524	=item ev_loop_fork (loop)	575	=item ev_loop_fork (loop)
525		576
526	Like C<ev_default_fork>, but acts on an event loop created by	577	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	578	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.	579	after fork that you want to re-use in the child, and how you do this is
		580	entirely your own problem.
529		581
530	=item int ev_is_default_loop (loop)	582	=item int ev_is_default_loop (loop)
531		583
532	Returns true when the given loop actually is the default loop, false otherwise.	584	Returns true when the given loop is, in fact, the default loop, and false
		585	otherwise.
533		586
534	=item unsigned int ev_loop_count (loop)	587	=item unsigned int ev_loop_count (loop)
535		588
536	Returns the count of loop iterations for the loop, which is identical to	589	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	590	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	605	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	606	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	607	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).	608	event occurring (or more correctly, libev finding out about it).
556		609
		610	=item ev_now_update (loop)
		611
		612	Establishes the current time by querying the kernel, updating the time
		613	returned by C<ev_now ()> in the progress. This is a costly operation and
		614	is usually done automatically within C<ev_loop ()>.
		615
		616	This function is rarely useful, but when some event callback runs for a
		617	very long time without entering the event loop, updating libev's idea of
		618	the current time is a good idea.
		619
		620	See also "The special problem of time updates" in the C<ev_timer> section.
		621
557	=item ev_loop (loop, int flags)	622	=item ev_loop (loop, int flags)
558		623
559	Finally, this is it, the event handler. This function usually is called	624	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	625	after you initialised all your watchers and you want to start handling
561	events.	626	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	628	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.	629	either no event watchers are active anymore or C<ev_unloop> was called.
565		630
566	Please note that an explicit C<ev_unloop> is usually better than	631	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	632	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	633	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	634	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.	635	of relying on its watchers stopping correctly, that is truly a thing of
		636	beauty.
571		637
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	638	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	639	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.	640	process in case there are no events and will return after one iteration of
		641	the loop.
575		642
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	643	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	644	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	645	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	646	be an event internal to libev itself, so there is no guarentee that a
580	external event in conjunction with something not expressible using other	647	user-registered callback will be called), and will return after one
		648	iteration of the loop.
		649
		650	This is useful if you are waiting for some external event in conjunction
		651	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	652	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.	653	usually a better approach for this kind of thing.
583		654
584	Here are the gory details of what C<ev_loop> does:	655	Here are the gory details of what C<ev_loop> does:
585		656
586	- Before the first iteration, call any pending watchers.	657	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	658	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	659	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	660	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	661	- If we have been forked, detach and recreate the kernel state
		662	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	663	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	664	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	665	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	666	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	667	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	668	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	669	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	670	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	671	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	672	- Queue all expired timers.
601	- Queue all outstanding periodics.	673	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	674	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	675	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	676	- 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	677	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	678	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	679	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	684	anymore.
613		685
614	... queue jobs here, make sure they register event watchers as long	686	... 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..)	687	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	688	ev_loop (my_loop, 0);
617	... jobs done. yeah!	689	... jobs done or somebody called unloop. yeah!
618		690
619	=item ev_unloop (loop, how)	691	=item ev_unloop (loop, how)
620		692
621	Can be used to make a call to C<ev_loop> return early (but only after it	693	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	694	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	695	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.	696	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		697
626	This "unloop state" will be cleared when entering C<ev_loop> again.	698	This "unloop state" will be cleared when entering C<ev_loop> again.
627		699
		700	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		701
628	=item ev_ref (loop)	702	=item ev_ref (loop)
629		703
630	=item ev_unref (loop)	704	=item ev_unref (loop)
631		705
632	Ref/unref can be used to add or remove a reference count on the event	706	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	707	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	708	count is nonzero, C<ev_loop> will not return on its own.
		709
635	a watcher you never unregister that should not keep C<ev_loop> from	710	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	711	from returning, call ev_unref() after starting, and ev_ref() before
		712	stopping it.
		713
637	example, libev itself uses this for its internal signal pipe: It is not	714	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	715	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	716	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	717	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>	718	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,	719	(but only if the watcher wasn't active before, or was active before,
643	respectively).	720	respectively).
644		721
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	722	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	723	running when nothing else is active.
647		724
648	struct ev_signal exitsig;	725	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	726	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	727	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	728	evf_unref (loop);
652		729
653	Example: For some weird reason, unregister the above signal handler again.	730	Example: For some weird reason, unregister the above signal handler again.
654		731
655	ev_ref (loop);	732	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	733	ev_signal_stop (loop, &exitsig);
657		734
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	735	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		736
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	737	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		738
662	These advanced functions influence the time that libev will spend waiting	739	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	740	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.	741	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		742	latency.
665		743
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	744	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	745	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	746	to increase efficiency of loop iterations (or to increase power-saving
		747	opportunities).
669		748
670	The background is that sometimes your program runs just fast enough to	749	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	750	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	751	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	752	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	753	overhead for the actual polling but can deliver many events at once.
675		754
676	By setting a higher I<io collect interval> you allow libev to spend more	755	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,	756	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	758	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.	759	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		760
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	761	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	762	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	763	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	764	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	765	value will not introduce any overhead in libev.
687		766
688	Many (busy) programs can usually benefit by setting the io collect	767	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	768	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	769	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>,	770	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.	771	as this approaches the timing granularity of most systems.
		772
		773	Setting the I<timeout collect interval> can improve the opportunity for
		774	saving power, as the program will "bundle" timer callback invocations that
		775	are "near" in time together, by delaying some, thus reducing the number of
		776	times the process sleeps and wakes up again. Another useful technique to
		777	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		778	they fire on, say, one-second boundaries only.
		779
		780	=item ev_loop_verify (loop)
		781
		782	This function only does something when C<EV_VERIFY> support has been
		783	compiled in, which is the default for non-minimal builds. It tries to go
		784	through all internal structures and checks them for validity. If anything
		785	is found to be inconsistent, it will print an error message to standard
		786	error and call C<abort ()>.
		787
		788	This can be used to catch bugs inside libev itself: under normal
		789	circumstances, this function will never abort as of course libev keeps its
		790	data structures consistent.
693		791
694	=back	792	=back
695		793
696		794
697	=head1 ANATOMY OF A WATCHER	795	=head1 ANATOMY OF A WATCHER
		796
		797	In the following description, uppercase C<TYPE> in names stands for the
		798	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		799	watchers and C<ev_io_start> for I/O watchers.
698		800
699	A watcher is a structure that you create and register to record your	801	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	802	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	803	become readable, you would create an C<ev_io> watcher for that:
702		804
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	805	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	806	{
705	ev_io_stop (w);	807	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	808	ev_unloop (loop, EVUNLOOP_ALL);
707	}	809	}
708		810
709	struct ev_loop *loop = ev_default_loop (0);	811	struct ev_loop *loop = ev_default_loop (0);
		812
710	struct ev_io stdin_watcher;	813	ev_io stdin_watcher;
		814
711	ev_init (&stdin_watcher, my_cb);	815	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	816	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	817	ev_io_start (loop, &stdin_watcher);
		818
714	ev_loop (loop, 0);	819	ev_loop (loop, 0);
715		820
716	As you can see, you are responsible for allocating the memory for your	821	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	822	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	823	stack).
		824
		825	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		826	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		827
720	Each watcher structure must be initialised by a call to C<ev_init	828	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	829	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	830	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	831	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	832	is readable and/or writable).
725		833
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	834	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	835	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	836	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	837	ev_TYPE_init (watcher *, callback, ...) >>.
730		838
731	To make the watcher actually watch out for events, you have to start it	839	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	840	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	841	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	842	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		843
736	As long as your watcher is active (has been started but not stopped) you	844	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	845	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	846	reinitialise it or call its C<ev_TYPE_set> macro.
739		847
740	Each and every callback receives the event loop pointer as first, the	848	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	849	registered watcher structure as second, and a bitset of received events as
742	third argument.	850	third argument.
743		851
…		…
803		911
804	The given async watcher has been asynchronously notified (see C<ev_async>).	912	The given async watcher has been asynchronously notified (see C<ev_async>).
805		913
806	=item C<EV_ERROR>	914	=item C<EV_ERROR>
807		915
808	An unspecified error has occured, the watcher has been stopped. This might	916	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	917	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	918	ran out of memory, a file descriptor was found to be closed or any other
		919	problem. Libev considers these application bugs.
		920
811	problem. You best act on it by reporting the problem and somehow coping	921	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	922	watcher being stopped. Note that well-written programs should not receive
		923	an error ever, so when your watcher receives it, this usually indicates a
		924	bug in your program.
813		925
814	Libev will usually signal a few "dummy" events together with an error,	926	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	927	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	928	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	929	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	930	programs, though, as the fd could already be closed and reused for another
		931	thing, so beware.
819		932
820	=back	933	=back
821		934
822	=head2 GENERIC WATCHER FUNCTIONS	935	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		936
827	=over 4	937	=over 4
828		938
829	=item C<ev_init> (ev_TYPE *watcher, callback)	939	=item C<ev_init> (ev_TYPE *watcher, callback)
830		940
…		…
836	which rolls both calls into one.	946	which rolls both calls into one.
837		947
838	You can reinitialise a watcher at any time as long as it has been stopped	948	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	949	(or never started) and there are no pending events outstanding.
840		950
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	951	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	952	int revents)>.
		953
		954	Example: Initialise an C<ev_io> watcher in two steps.
		955
		956	ev_io w;
		957	ev_init (&w, my_cb);
		958	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		959
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	960	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		961
846	This macro initialises the type-specific parts of a watcher. You need to	962	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	963	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	966	difference to the C<ev_init> macro).
851		967
852	Although some watcher types do not have type-specific arguments	968	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	969	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		970
		971	See C<ev_init>, above, for an example.
		972
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	973	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		974
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	975	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	976	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	977	a watcher. The same limitations apply, of course.
		978
		979	Example: Initialise and set an C<ev_io> watcher in one step.
		980
		981	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		982
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	983	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		984
863	Starts (activates) the given watcher. Only active watchers will receive	985	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	986	events. If the watcher is already active nothing will happen.
865		987
		988	Example: Start the C<ev_io> watcher that is being abused as example in this
		989	whole section.
		990
		991	ev_io_start (EV_DEFAULT_UC, &w);
		992
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	993	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		994
868	Stops the given watcher again (if active) and clears the pending	995	Stops the given watcher if active, and clears the pending status (whether
		996	the watcher was active or not).
		997
869	status. It is possible that stopped watchers are pending (for example,	998	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	999	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1000	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	1001	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	1002	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1003
875	=item bool ev_is_active (ev_TYPE *watcher)	1004	=item bool ev_is_active (ev_TYPE *watcher)
876		1005
877	Returns a true value iff the watcher is active (i.e. it has been started	1006	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1007	and not yet been stopped). As long as a watcher is active you must not modify
…		…
920	The default priority used by watchers when no priority has been set is	1049	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1050	always C<0>, which is supposed to not be too high and not be too low :).
922		1051
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1052	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
924	fine, as long as you do not mind that the priority value you query might	1053	fine, as long as you do not mind that the priority value you query might
925	or might not have been adjusted to be within valid range.	1054	or might not have been clamped to the valid range.
926		1055
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1056	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1057
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1058	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1059	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1060	can deal with that fact, as both are simply passed through to the
		1061	callback.
932		1062
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1063	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1064
935	If the watcher is pending, this function returns clears its pending status	1065	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1066	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1067	watcher isn't pending it does nothing and returns C<0>.
938		1068
		1069	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1070	callback to be invoked, which can be accomplished with this function.
		1071
939	=back	1072	=back
940		1073
941		1074
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1075	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1076
944	Each watcher has, by default, a member C<void *data> that you can change	1077	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1078	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1079	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1080	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1081	member, you can also "subclass" the watcher type and provide your own
949	data:	1082	data:
950		1083
951	struct my_io	1084	struct my_io
952	{	1085	{
953	struct ev_io io;	1086	ev_io io;
954	int otherfd;	1087	int otherfd;
955	void *somedata;	1088	void *somedata;
956	struct whatever *mostinteresting;	1089	struct whatever *mostinteresting;
957	}	1090	};
		1091
		1092	...
		1093	struct my_io w;
		1094	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1095
959	And since your callback will be called with a pointer to the watcher, you	1096	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1097	can cast it back to your own type:
961		1098
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1099	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1100	{
964	struct my_io *w = (struct my_io *)w_;	1101	struct my_io *w = (struct my_io *)w_;
965	...	1102	...
966	}	1103	}
967		1104
968	More interesting and less C-conformant ways of casting your callback type	1105	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1106	instead have been omitted.
970		1107
971	Another common scenario is having some data structure with multiple	1108	Another common scenario is to use some data structure with multiple
972	watchers:	1109	embedded watchers:
973		1110
974	struct my_biggy	1111	struct my_biggy
975	{	1112	{
976	int some_data;	1113	int some_data;
977	ev_timer t1;	1114	ev_timer t1;
978	ev_timer t2;	1115	ev_timer t2;
979	}	1116	}
980		1117
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1118	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1119	complicated: Either you store the address of your C<my_biggy> struct
		1120	in the C<data> member of the watcher (for woozies), or you need to use
		1121	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1122	programmers):
983		1123
984	#include <stddef.h>	1124	#include <stddef.h>
985		1125
986	static void	1126	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1127	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1128	{
989	struct my_biggy big = (struct my_biggy *	1129	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1130	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1131	}
992		1132
993	static void	1133	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1134	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1135	{
996	struct my_biggy big = (struct my_biggy *	1136	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1137	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1138	}
999		1139
1000		1140
1001	=head1 WATCHER TYPES	1141	=head1 WATCHER TYPES
1002		1142
1003	This section describes each watcher in detail, but will not repeat	1143	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1167	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1168	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1169	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1170	required if you know what you are doing).
1031		1171
1032	If you must do this, then force the use of a known-to-be-good backend	1172	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1173	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1174	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1175
1036	Another thing you have to watch out for is that it is quite easy to	1176	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1177	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1178	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1179	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1180	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1181	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1182	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1183	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1184
1045	If you cannot run the fd in non-blocking mode (for example you should not	1185	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1186	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1187	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1188	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1189	does this on its own, so its quite safe to use). Some people additionally
		1190	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1191	indefinitely.
		1192
		1193	But really, best use non-blocking mode.
1050		1194
1051	=head3 The special problem of disappearing file descriptors	1195	=head3 The special problem of disappearing file descriptors
1052		1196
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1197	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1198	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1199	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1200	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1201	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1202	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1203	fact, a different file descriptor.
1060		1204
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1235	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1236	C<EVBACKEND_POLL>.
1093		1237
1094	=head3 The special problem of SIGPIPE	1238	=head3 The special problem of SIGPIPE
1095		1239
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1240	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1241	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1242	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1243	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1244
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1245	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1246	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1247	somewhere, as that would have given you a big clue).
1105		1248
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1254	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1255
1113	=item ev_io_set (ev_io *, int fd, int events)	1256	=item ev_io_set (ev_io *, int fd, int events)
1114		1257
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1258	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1259	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1260	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1261
1119	=item int fd [read-only]	1262	=item int fd [read-only]
1120		1263
1121	The file descriptor being watched.	1264	The file descriptor being watched.
1122		1265
…		…
1130		1273
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1274	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1275	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1276	attempt to read a whole line in the callback.
1134		1277
1135	static void	1278	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1279	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1280	{
1138	ev_io_stop (loop, w);	1281	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1282	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1283	}
1141		1284
1142	...	1285	...
1143	struct ev_loop *loop = ev_default_init (0);	1286	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1287	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1288	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1289	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1290	ev_loop (loop, 0);
1148		1291
1149		1292
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1293	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1294
1152	Timer watchers are simple relative timers that generate an event after a	1295	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1296	given time, and optionally repeating in regular intervals after that.
1154		1297
1155	The timers are based on real time, that is, if you register an event that	1298	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to january last	1299	times out after an hour and you reset your system clock to January last
1157	year, it will still time out after (roughly) and hour. "Roughly" because	1300	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1301	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1302	monotonic clock option helps a lot here).
		1303
		1304	The callback is guaranteed to be invoked only I<after> its timeout has
		1305	passed, but if multiple timers become ready during the same loop iteration
		1306	then order of execution is undefined.
		1307
		1308	=head3 Be smart about timeouts
		1309
		1310	Many real-world problems involve some kind of timeout, usually for error
		1311	recovery. A typical example is an HTTP request - if the other side hangs,
		1312	you want to raise some error after a while.
		1313
		1314	What follows are some ways to handle this problem, from obvious and
		1315	inefficient to smart and efficient.
		1316
		1317	In the following, a 60 second activity timeout is assumed - a timeout that
		1318	gets reset to 60 seconds each time there is activity (e.g. each time some
		1319	data or other life sign was received).
		1320
		1321	=over 4
		1322
		1323	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1324
		1325	This is the most obvious, but not the most simple way: In the beginning,
		1326	start the watcher:
		1327
		1328	ev_timer_init (timer, callback, 60., 0.);
		1329	ev_timer_start (loop, timer);
		1330
		1331	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1332	and start it again:
		1333
		1334	ev_timer_stop (loop, timer);
		1335	ev_timer_set (timer, 60., 0.);
		1336	ev_timer_start (loop, timer);
		1337
		1338	This is relatively simple to implement, but means that each time there is
		1339	some activity, libev will first have to remove the timer from its internal
		1340	data structure and then add it again. Libev tries to be fast, but it's
		1341	still not a constant-time operation.
		1342
		1343	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1344
		1345	This is the easiest way, and involves using C<ev_timer_again> instead of
		1346	C<ev_timer_start>.
		1347
		1348	To implement this, configure an C<ev_timer> with a C<repeat> value
		1349	of C<60> and then call C<ev_timer_again> at start and each time you
		1350	successfully read or write some data. If you go into an idle state where
		1351	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1352	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1353
		1354	That means you can ignore both the C<ev_timer_start> function and the
		1355	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1356	member and C<ev_timer_again>.
		1357
		1358	At start:
		1359
		1360	ev_timer_init (timer, callback);
		1361	timer->repeat = 60.;
		1362	ev_timer_again (loop, timer);
		1363
		1364	Each time there is some activity:
		1365
		1366	ev_timer_again (loop, timer);
		1367
		1368	It is even possible to change the time-out on the fly, regardless of
		1369	whether the watcher is active or not:
		1370
		1371	timer->repeat = 30.;
		1372	ev_timer_again (loop, timer);
		1373
		1374	This is slightly more efficient then stopping/starting the timer each time
		1375	you want to modify its timeout value, as libev does not have to completely
		1376	remove and re-insert the timer from/into its internal data structure.
		1377
		1378	It is, however, even simpler than the "obvious" way to do it.
		1379
		1380	=item 3. Let the timer time out, but then re-arm it as required.
		1381
		1382	This method is more tricky, but usually most efficient: Most timeouts are
		1383	relatively long compared to the intervals between other activity - in
		1384	our example, within 60 seconds, there are usually many I/O events with
		1385	associated activity resets.
		1386
		1387	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1388	but remember the time of last activity, and check for a real timeout only
		1389	within the callback:
		1390
		1391	ev_tstamp last_activity; // time of last activity
		1392
		1393	static void
		1394	callback (EV_P_ ev_timer *w, int revents)
		1395	{
		1396	ev_tstamp now = ev_now (EV_A);
		1397	ev_tstamp timeout = last_activity + 60.;
		1398
		1399	// if last_activity + 60. is older than now, we did time out
		1400	if (timeout < now)
		1401	{
		1402	// timeout occured, take action
		1403	}
		1404	else
		1405	{
		1406	// callback was invoked, but there was some activity, re-arm
		1407	// the watcher to fire in last_activity + 60, which is
		1408	// guaranteed to be in the future, so "again" is positive:
		1409	w->again = timeout - now;
		1410	ev_timer_again (EV_A_ w);
		1411	}
		1412	}
		1413
		1414	To summarise the callback: first calculate the real timeout (defined
		1415	as "60 seconds after the last activity"), then check if that time has
		1416	been reached, which means something I<did>, in fact, time out. Otherwise
		1417	the callback was invoked too early (C<timeout> is in the future), so
		1418	re-schedule the timer to fire at that future time, to see if maybe we have
		1419	a timeout then.
		1420
		1421	Note how C<ev_timer_again> is used, taking advantage of the
		1422	C<ev_timer_again> optimisation when the timer is already running.
		1423
		1424	This scheme causes more callback invocations (about one every 60 seconds
		1425	minus half the average time between activity), but virtually no calls to
		1426	libev to change the timeout.
		1427
		1428	To start the timer, simply initialise the watcher and set C<last_activity>
		1429	to the current time (meaning we just have some activity :), then call the
		1430	callback, which will "do the right thing" and start the timer:
		1431
		1432	ev_timer_init (timer, callback);
		1433	last_activity = ev_now (loop);
		1434	callback (loop, timer, EV_TIMEOUT);
		1435
		1436	And when there is some activity, simply store the current time in
		1437	C<last_activity>, no libev calls at all:
		1438
		1439	last_actiivty = ev_now (loop);
		1440
		1441	This technique is slightly more complex, but in most cases where the
		1442	time-out is unlikely to be triggered, much more efficient.
		1443
		1444	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1445	callback :) - just change the timeout and invoke the callback, which will
		1446	fix things for you.
		1447
		1448	=item 4. Wee, just use a double-linked list for your timeouts.
		1449
		1450	If there is not one request, but many thousands (millions...), all
		1451	employing some kind of timeout with the same timeout value, then one can
		1452	do even better:
		1453
		1454	When starting the timeout, calculate the timeout value and put the timeout
		1455	at the I<end> of the list.
		1456
		1457	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1458	the list is expected to fire (for example, using the technique #3).
		1459
		1460	When there is some activity, remove the timer from the list, recalculate
		1461	the timeout, append it to the end of the list again, and make sure to
		1462	update the C<ev_timer> if it was taken from the beginning of the list.
		1463
		1464	This way, one can manage an unlimited number of timeouts in O(1) time for
		1465	starting, stopping and updating the timers, at the expense of a major
		1466	complication, and having to use a constant timeout. The constant timeout
		1467	ensures that the list stays sorted.
		1468
		1469	=back
		1470
		1471	So which method the best?
		1472
		1473	Method #2 is a simple no-brain-required solution that is adequate in most
		1474	situations. Method #3 requires a bit more thinking, but handles many cases
		1475	better, and isn't very complicated either. In most case, choosing either
		1476	one is fine, with #3 being better in typical situations.
		1477
		1478	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1479	rather complicated, but extremely efficient, something that really pays
		1480	off after the first million or so of active timers, i.e. it's usually
		1481	overkill :)
		1482
		1483	=head3 The special problem of time updates
		1484
		1485	Establishing the current time is a costly operation (it usually takes at
		1486	least two system calls): EV therefore updates its idea of the current
		1487	time only before and after C<ev_loop> collects new events, which causes a
		1488	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1489	lots of events in one iteration.
1160		1490
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1491	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1492	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1493	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1494	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1495	timeout on the current time, use something like this to adjust for this:
1166		1496
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1497	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1498
1169	The callback is guarenteed to be invoked only after its timeout has passed,	1499	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1500	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1501	()>.
1172		1502
1173	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1174		1504
1175	=over 4	1505	=over 4
1176		1506
…		…
1195	This will act as if the timer timed out and restart it again if it is	1525	This will act as if the timer timed out and restart it again if it is
1196	repeating. The exact semantics are:	1526	repeating. The exact semantics are:
1197		1527
1198	If the timer is pending, its pending status is cleared.	1528	If the timer is pending, its pending status is cleared.
1199		1529
1200	If the timer is started but nonrepeating, stop it (as if it timed out).	1530	If the timer is started but non-repeating, stop it (as if it timed out).
1201		1531
1202	If the timer is repeating, either start it if necessary (with the	1532	If the timer is repeating, either start it if necessary (with the
1203	C<repeat> value), or reset the running timer to the C<repeat> value.	1533	C<repeat> value), or reset the running timer to the C<repeat> value.
1204		1534
1205	This sounds a bit complicated, but here is a useful and typical	1535	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1206	example: Imagine you have a tcp connection and you want a so-called idle	1536	usage example.
1207	timeout, that is, you want to be called when there have been, say, 60
1208	seconds of inactivity on the socket. The easiest way to do this is to
1209	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1210	C<ev_timer_again> each time you successfully read or write some data. If
1211	you go into an idle state where you do not expect data to travel on the
1212	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1213	automatically restart it if need be.
1214
1215	That means you can ignore the C<after> value and C<ev_timer_start>
1216	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1217
1218	ev_timer_init (timer, callback, 0., 5.);
1219	ev_timer_again (loop, timer);
1220	...
1221	timer->again = 17.;
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 10.;
1225	ev_timer_again (loop, timer);
1226
1227	This is more slightly efficient then stopping/starting the timer each time
1228	you want to modify its timeout value.
1229		1537
1230	=item ev_tstamp repeat [read-write]	1538	=item ev_tstamp repeat [read-write]
1231		1539
1232	The current C<repeat> value. Will be used each time the watcher times out	1540	The current C<repeat> value. Will be used each time the watcher times out
1233	or C<ev_timer_again> is called and determines the next timeout (if any),	1541	or C<ev_timer_again> is called, and determines the next timeout (if any),
1234	which is also when any modifications are taken into account.	1542	which is also when any modifications are taken into account.
1235		1543
1236	=back	1544	=back
1237		1545
1238	=head3 Examples	1546	=head3 Examples
1239		1547
1240	Example: Create a timer that fires after 60 seconds.	1548	Example: Create a timer that fires after 60 seconds.
1241		1549
1242	static void	1550	static void
1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1551	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1244	{	1552	{
1245	.. one minute over, w is actually stopped right here	1553	.. one minute over, w is actually stopped right here
1246	}	1554	}
1247		1555
1248	struct ev_timer mytimer;	1556	ev_timer mytimer;
1249	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1557	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1250	ev_timer_start (loop, &mytimer);	1558	ev_timer_start (loop, &mytimer);
1251		1559
1252	Example: Create a timeout timer that times out after 10 seconds of	1560	Example: Create a timeout timer that times out after 10 seconds of
1253	inactivity.	1561	inactivity.
1254		1562
1255	static void	1563	static void
1256	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1564	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1257	{	1565	{
1258	.. ten seconds without any activity	1566	.. ten seconds without any activity
1259	}	1567	}
1260		1568
1261	struct ev_timer mytimer;	1569	ev_timer mytimer;
1262	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1570	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1263	ev_timer_again (&mytimer); /* start timer */	1571	ev_timer_again (&mytimer); /* start timer */
1264	ev_loop (loop, 0);	1572	ev_loop (loop, 0);
1265		1573
1266	// and in some piece of code that gets executed on any "activity":	1574	// and in some piece of code that gets executed on any "activity":
1267	// reset the timeout to start ticking again at 10 seconds	1575	// reset the timeout to start ticking again at 10 seconds
1268	ev_timer_again (&mytimer);	1576	ev_timer_again (&mytimer);
1269		1577
1270		1578
1271	=head2 C<ev_periodic> - to cron or not to cron?	1579	=head2 C<ev_periodic> - to cron or not to cron?
1272		1580
1273	Periodic watchers are also timers of a kind, but they are very versatile	1581	Periodic watchers are also timers of a kind, but they are very versatile
1274	(and unfortunately a bit complex).	1582	(and unfortunately a bit complex).
1275		1583
1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1584	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1277	but on wallclock time (absolute time). You can tell a periodic watcher	1585	but on wall clock time (absolute time). You can tell a periodic watcher
1278	to trigger after some specific point in time. For example, if you tell a	1586	to trigger after some specific point in time. For example, if you tell a
1279	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1587	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1280	+ 10.>, that is, an absolute time not a delay) and then reset your system	1588	+ 10.>, that is, an absolute time not a delay) and then reset your system
1281	clock to january of the previous year, then it will take more than year	1589	clock to January of the previous year, then it will take more than year
1282	to trigger the event (unlike an C<ev_timer>, which would still trigger	1590	to trigger the event (unlike an C<ev_timer>, which would still trigger
1283	roughly 10 seconds later as it uses a relative timeout).	1591	roughly 10 seconds later as it uses a relative timeout).
1284		1592
1285	C<ev_periodic>s can also be used to implement vastly more complex timers,	1593	C<ev_periodic>s can also be used to implement vastly more complex timers,
1286	such as triggering an event on each "midnight, local time", or other	1594	such as triggering an event on each "midnight, local time", or other
1287	complicated, rules.	1595	complicated rules.
1288		1596
1289	As with timers, the callback is guarenteed to be invoked only when the	1597	As with timers, the callback is guaranteed to be invoked only when the
1290	time (C<at>) has passed, but if multiple periodic timers become ready	1598	time (C<at>) has passed, but if multiple periodic timers become ready
1291	during the same loop iteration then order of execution is undefined.	1599	during the same loop iteration, then order of execution is undefined.
1292		1600
1293	=head3 Watcher-Specific Functions and Data Members	1601	=head3 Watcher-Specific Functions and Data Members
1294		1602
1295	=over 4	1603	=over 4
1296		1604
1297	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1605	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1298		1606
1299	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1607	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1300		1608
1301	Lots of arguments, lets sort it out... There are basically three modes of	1609	Lots of arguments, lets sort it out... There are basically three modes of
1302	operation, and we will explain them from simplest to complex:	1610	operation, and we will explain them from simplest to most complex:
1303		1611
1304	=over 4	1612	=over 4
1305		1613
1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1614	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1307		1615
1308	In this configuration the watcher triggers an event after the wallclock	1616	In this configuration the watcher triggers an event after the wall clock
1309	time C<at> has passed and doesn't repeat. It will not adjust when a time	1617	time C<at> has passed. It will not repeat and will not adjust when a time
1310	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1618	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1311	run when the system time reaches or surpasses this time.	1619	only run when the system clock reaches or surpasses this time.
1312		1620
1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1621	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1314		1622
1315	In this mode the watcher will always be scheduled to time out at the next	1623	In this mode the watcher will always be scheduled to time out at the next
1316	C<at + N * interval> time (for some integer N, which can also be negative)	1624	C<at + N * interval> time (for some integer N, which can also be negative)
1317	and then repeat, regardless of any time jumps.	1625	and then repeat, regardless of any time jumps.
1318		1626
1319	This can be used to create timers that do not drift with respect to system	1627	This can be used to create timers that do not drift with respect to the
1320	time, for example, here is a C<ev_periodic> that triggers each hour, on	1628	system clock, for example, here is a C<ev_periodic> that triggers each
1321	the hour:	1629	hour, on the hour:
1322		1630
1323	ev_periodic_set (&periodic, 0., 3600., 0);	1631	ev_periodic_set (&periodic, 0., 3600., 0);
1324		1632
1325	This doesn't mean there will always be 3600 seconds in between triggers,	1633	This doesn't mean there will always be 3600 seconds in between triggers,
1326	but only that the the callback will be called when the system time shows a	1634	but only that the callback will be called when the system time shows a
1327	full hour (UTC), or more correctly, when the system time is evenly divisible	1635	full hour (UTC), or more correctly, when the system time is evenly divisible
1328	by 3600.	1636	by 3600.
1329		1637
1330	Another way to think about it (for the mathematically inclined) is that	1638	Another way to think about it (for the mathematically inclined) is that
1331	C<ev_periodic> will try to run the callback in this mode at the next possible	1639	C<ev_periodic> will try to run the callback in this mode at the next possible
1332	time where C<time = at (mod interval)>, regardless of any time jumps.	1640	time where C<time = at (mod interval)>, regardless of any time jumps.
1333		1641
1334	For numerical stability it is preferable that the C<at> value is near	1642	For numerical stability it is preferable that the C<at> value is near
1335	C<ev_now ()> (the current time), but there is no range requirement for	1643	C<ev_now ()> (the current time), but there is no range requirement for
1336	this value, and in fact is often specified as zero.	1644	this value, and in fact is often specified as zero.
		1645
		1646	Note also that there is an upper limit to how often a timer can fire (CPU
		1647	speed for example), so if C<interval> is very small then timing stability
		1648	will of course deteriorate. Libev itself tries to be exact to be about one
		1649	millisecond (if the OS supports it and the machine is fast enough).
1337		1650
1338	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1651	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1339		1652
1340	In this mode the values for C<interval> and C<at> are both being	1653	In this mode the values for C<interval> and C<at> are both being
1341	ignored. Instead, each time the periodic watcher gets scheduled, the	1654	ignored. Instead, each time the periodic watcher gets scheduled, the
…		…
1347		1660
1348	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1661	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1349	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1662	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1350	only event loop modification you are allowed to do).	1663	only event loop modification you are allowed to do).
1351		1664
1352	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1665	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1353	*w, ev_tstamp now)>, e.g.:	1666	*w, ev_tstamp now)>, e.g.:
1354		1667
		1668	static ev_tstamp
1355	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1669	my_rescheduler (ev_periodic *w, ev_tstamp now)
1356	{	1670	{
1357	return now + 60.;	1671	return now + 60.;
1358	}	1672	}
1359		1673
1360	It must return the next time to trigger, based on the passed time value	1674	It must return the next time to trigger, based on the passed time value
…		…
1397		1711
1398	The current interval value. Can be modified any time, but changes only	1712	The current interval value. Can be modified any time, but changes only
1399	take effect when the periodic timer fires or C<ev_periodic_again> is being	1713	take effect when the periodic timer fires or C<ev_periodic_again> is being
1400	called.	1714	called.
1401		1715
1402	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1716	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1403		1717
1404	The current reschedule callback, or C<0>, if this functionality is	1718	The current reschedule callback, or C<0>, if this functionality is
1405	switched off. Can be changed any time, but changes only take effect when	1719	switched off. Can be changed any time, but changes only take effect when
1406	the periodic timer fires or C<ev_periodic_again> is being called.	1720	the periodic timer fires or C<ev_periodic_again> is being called.
1407		1721
1408	=back	1722	=back
1409		1723
1410	=head3 Examples	1724	=head3 Examples
1411		1725
1412	Example: Call a callback every hour, or, more precisely, whenever the	1726	Example: Call a callback every hour, or, more precisely, whenever the
1413	system clock is divisible by 3600. The callback invocation times have	1727	system time is divisible by 3600. The callback invocation times have
1414	potentially a lot of jittering, but good long-term stability.	1728	potentially a lot of jitter, but good long-term stability.
1415		1729
1416	static void	1730	static void
1417	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1731	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1418	{	1732	{
1419	... its now a full hour (UTC, or TAI or whatever your clock follows)	1733	... its now a full hour (UTC, or TAI or whatever your clock follows)
1420	}	1734	}
1421		1735
1422	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1423	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1737	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1424	ev_periodic_start (loop, &hourly_tick);	1738	ev_periodic_start (loop, &hourly_tick);
1425		1739
1426	Example: The same as above, but use a reschedule callback to do it:	1740	Example: The same as above, but use a reschedule callback to do it:
1427		1741
1428	#include <math.h>	1742	#include <math.h>
1429		1743
1430	static ev_tstamp	1744	static ev_tstamp
1431	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1745	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1432	{	1746	{
1433	return fmod (now, 3600.) + 3600.;	1747	return now + (3600. - fmod (now, 3600.));
1434	}	1748	}
1435		1749
1436	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1750	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1437		1751
1438	Example: Call a callback every hour, starting now:	1752	Example: Call a callback every hour, starting now:
1439		1753
1440	struct ev_periodic hourly_tick;	1754	ev_periodic hourly_tick;
1441	ev_periodic_init (&hourly_tick, clock_cb,	1755	ev_periodic_init (&hourly_tick, clock_cb,
1442	fmod (ev_now (loop), 3600.), 3600., 0);	1756	fmod (ev_now (loop), 3600.), 3600., 0);
1443	ev_periodic_start (loop, &hourly_tick);	1757	ev_periodic_start (loop, &hourly_tick);
1444		1758
1445		1759
1446	=head2 C<ev_signal> - signal me when a signal gets signalled!	1760	=head2 C<ev_signal> - signal me when a signal gets signalled!
1447		1761
1448	Signal watchers will trigger an event when the process receives a specific	1762	Signal watchers will trigger an event when the process receives a specific
1449	signal one or more times. Even though signals are very asynchronous, libev	1763	signal one or more times. Even though signals are very asynchronous, libev
1450	will try it's best to deliver signals synchronously, i.e. as part of the	1764	will try it's best to deliver signals synchronously, i.e. as part of the
1451	normal event processing, like any other event.	1765	normal event processing, like any other event.
1452		1766
		1767	If you want signals asynchronously, just use C<sigaction> as you would
		1768	do without libev and forget about sharing the signal. You can even use
		1769	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1770
1453	You can configure as many watchers as you like per signal. Only when the	1771	You can configure as many watchers as you like per signal. Only when the
1454	first watcher gets started will libev actually register a signal watcher	1772	first watcher gets started will libev actually register a signal handler
1455	with the kernel (thus it coexists with your own signal handlers as long	1773	with the kernel (thus it coexists with your own signal handlers as long as
1456	as you don't register any with libev). Similarly, when the last signal	1774	you don't register any with libev for the same signal). Similarly, when
1457	watcher for a signal is stopped libev will reset the signal handler to	1775	the last signal watcher for a signal is stopped, libev will reset the
1458	SIG_DFL (regardless of what it was set to before).	1776	signal handler to SIG_DFL (regardless of what it was set to before).
1459		1777
1460	If possible and supported, libev will install its handlers with	1778	If possible and supported, libev will install its handlers with
1461	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1779	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1462	interrupted. If you have a problem with syscalls getting interrupted by	1780	interrupted. If you have a problem with system calls getting interrupted by
1463	signals you can block all signals in an C<ev_check> watcher and unblock	1781	signals you can block all signals in an C<ev_check> watcher and unblock
1464	them in an C<ev_prepare> watcher.	1782	them in an C<ev_prepare> watcher.
1465		1783
1466	=head3 Watcher-Specific Functions and Data Members	1784	=head3 Watcher-Specific Functions and Data Members
1467		1785
…		…
1480		1798
1481	=back	1799	=back
1482		1800
1483	=head3 Examples	1801	=head3 Examples
1484		1802
1485	Example: Try to exit cleanly on SIGINT and SIGTERM.	1803	Example: Try to exit cleanly on SIGINT.
1486		1804
1487	static void	1805	static void
1488	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1806	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1489	{	1807	{
1490	ev_unloop (loop, EVUNLOOP_ALL);	1808	ev_unloop (loop, EVUNLOOP_ALL);
1491	}	1809	}
1492		1810
1493	struct ev_signal signal_watcher;	1811	ev_signal signal_watcher;
1494	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1812	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1495	ev_signal_start (loop, &sigint_cb);	1813	ev_signal_start (loop, &signal_watcher);
1496		1814
1497		1815
1498	=head2 C<ev_child> - watch out for process status changes	1816	=head2 C<ev_child> - watch out for process status changes
1499		1817
1500	Child watchers trigger when your process receives a SIGCHLD in response to	1818	Child watchers trigger when your process receives a SIGCHLD in response to
1501	some child status changes (most typically when a child of yours dies). It	1819	some child status changes (most typically when a child of yours dies or
1502	is permissible to install a child watcher I<after> the child has been	1820	exits). It is permissible to install a child watcher I<after> the child
1503	forked (which implies it might have already exited), as long as the event	1821	has been forked (which implies it might have already exited), as long
1504	loop isn't entered (or is continued from a watcher).	1822	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1823	forking and then immediately registering a watcher for the child is fine,
		1824	but forking and registering a watcher a few event loop iterations later is
		1825	not.
1505		1826
1506	Only the default event loop is capable of handling signals, and therefore	1827	Only the default event loop is capable of handling signals, and therefore
1507	you can only rgeister child watchers in the default event loop.	1828	you can only register child watchers in the default event loop.
1508		1829
1509	=head3 Process Interaction	1830	=head3 Process Interaction
1510		1831
1511	Libev grabs C<SIGCHLD> as soon as the default event loop is	1832	Libev grabs C<SIGCHLD> as soon as the default event loop is
1512	initialised. This is necessary to guarantee proper behaviour even if	1833	initialised. This is necessary to guarantee proper behaviour even if
1513	the first child watcher is started after the child exits. The occurance	1834	the first child watcher is started after the child exits. The occurrence
1514	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1835	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1515	synchronously as part of the event loop processing. Libev always reaps all	1836	synchronously as part of the event loop processing. Libev always reaps all
1516	children, even ones not watched.	1837	children, even ones not watched.
1517		1838
1518	=head3 Overriding the Built-In Processing	1839	=head3 Overriding the Built-In Processing
…		…
1522	handler, you can override it easily by installing your own handler for	1843	handler, you can override it easily by installing your own handler for
1523	C<SIGCHLD> after initialising the default loop, and making sure the	1844	C<SIGCHLD> after initialising the default loop, and making sure the
1524	default loop never gets destroyed. You are encouraged, however, to use an	1845	default loop never gets destroyed. You are encouraged, however, to use an
1525	event-based approach to child reaping and thus use libev's support for	1846	event-based approach to child reaping and thus use libev's support for
1526	that, so other libev users can use C<ev_child> watchers freely.	1847	that, so other libev users can use C<ev_child> watchers freely.
		1848
		1849	=head3 Stopping the Child Watcher
		1850
		1851	Currently, the child watcher never gets stopped, even when the
		1852	child terminates, so normally one needs to stop the watcher in the
		1853	callback. Future versions of libev might stop the watcher automatically
		1854	when a child exit is detected.
1527		1855
1528	=head3 Watcher-Specific Functions and Data Members	1856	=head3 Watcher-Specific Functions and Data Members
1529		1857
1530	=over 4	1858	=over 4
1531		1859
…		…
1560	=head3 Examples	1888	=head3 Examples
1561		1889
1562	Example: C<fork()> a new process and install a child handler to wait for	1890	Example: C<fork()> a new process and install a child handler to wait for
1563	its completion.	1891	its completion.
1564		1892
1565	ev_child cw;	1893	ev_child cw;
1566		1894
1567	static void	1895	static void
1568	child_cb (EV_P_ struct ev_child *w, int revents)	1896	child_cb (EV_P_ ev_child *w, int revents)
1569	{	1897	{
1570	ev_child_stop (EV_A_ w);	1898	ev_child_stop (EV_A_ w);
1571	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1899	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1572	}	1900	}
1573		1901
1574	pid_t pid = fork ();	1902	pid_t pid = fork ();
1575		1903
1576	if (pid < 0)	1904	if (pid < 0)
1577	// error	1905	// error
1578	else if (pid == 0)	1906	else if (pid == 0)
1579	{	1907	{
1580	// the forked child executes here	1908	// the forked child executes here
1581	exit (1);	1909	exit (1);
1582	}	1910	}
1583	else	1911	else
1584	{	1912	{
1585	ev_child_init (&cw, child_cb, pid, 0);	1913	ev_child_init (&cw, child_cb, pid, 0);
1586	ev_child_start (EV_DEFAULT_ &cw);	1914	ev_child_start (EV_DEFAULT_ &cw);
1587	}	1915	}
1588		1916
1589		1917
1590	=head2 C<ev_stat> - did the file attributes just change?	1918	=head2 C<ev_stat> - did the file attributes just change?
1591		1919
1592	This watches a filesystem path for attribute changes. That is, it calls	1920	This watches a file system path for attribute changes. That is, it calls
1593	C<stat> regularly (or when the OS says it changed) and sees if it changed	1921	C<stat> regularly (or when the OS says it changed) and sees if it changed
1594	compared to the last time, invoking the callback if it did.	1922	compared to the last time, invoking the callback if it did.
1595		1923
1596	The path does not need to exist: changing from "path exists" to "path does	1924	The path does not need to exist: changing from "path exists" to "path does
1597	not exist" is a status change like any other. The condition "path does	1925	not exist" is a status change like any other. The condition "path does
…		…
1600	the stat buffer having unspecified contents.	1928	the stat buffer having unspecified contents.
1601		1929
1602	The path I<should> be absolute and I<must not> end in a slash. If it is	1930	The path I<should> be absolute and I<must not> end in a slash. If it is
1603	relative and your working directory changes, the behaviour is undefined.	1931	relative and your working directory changes, the behaviour is undefined.
1604		1932
1605	Since there is no standard to do this, the portable implementation simply	1933	Since there is no standard kernel interface to do this, the portable
1606	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1934	implementation simply calls C<stat (2)> regularly on the path to see if
1607	can specify a recommended polling interval for this case. If you specify	1935	it changed somehow. You can specify a recommended polling interval for
1608	a polling interval of C<0> (highly recommended!) then a I<suitable,	1936	this case. If you specify a polling interval of C<0> (highly recommended!)
1609	unspecified default> value will be used (which you can expect to be around	1937	then a I<suitable, unspecified default> value will be used (which
1610	five seconds, although this might change dynamically). Libev will also	1938	you can expect to be around five seconds, although this might change
1611	impose a minimum interval which is currently around C<0.1>, but thats	1939	dynamically). Libev will also impose a minimum interval which is currently
1612	usually overkill.	1940	around C<0.1>, but thats usually overkill.
1613		1941
1614	This watcher type is not meant for massive numbers of stat watchers,	1942	This watcher type is not meant for massive numbers of stat watchers,
1615	as even with OS-supported change notifications, this can be	1943	as even with OS-supported change notifications, this can be
1616	resource-intensive.	1944	resource-intensive.
1617		1945
1618	At the time of this writing, only the Linux inotify interface is	1946	At the time of this writing, the only OS-specific interface implemented
1619	implemented (implementing kqueue support is left as an exercise for the	1947	is the Linux inotify interface (implementing kqueue support is left as
1620	reader, note, however, that the author sees no way of implementing ev_stat	1948	an exercise for the reader. Note, however, that the author sees no way
1621	semantics with kqueue). Inotify will be used to give hints only and should	1949	of implementing C<ev_stat> semantics with kqueue).
1622	not change the semantics of C<ev_stat> watchers, which means that libev
1623	sometimes needs to fall back to regular polling again even with inotify,
1624	but changes are usually detected immediately, and if the file exists there
1625	will be no polling.
1626		1950
1627	=head3 ABI Issues (Largefile Support)	1951	=head3 ABI Issues (Largefile Support)
1628		1952
1629	Libev by default (unless the user overrides this) uses the default	1953	Libev by default (unless the user overrides this) uses the default
1630	compilation environment, which means that on systems with optionally	1954	compilation environment, which means that on systems with large file
1631	disabled large file support, you get the 32 bit version of the stat	1955	support disabled by default, you get the 32 bit version of the stat
1632	structure. When using the library from programs that change the ABI to	1956	structure. When using the library from programs that change the ABI to
1633	use 64 bit file offsets the programs will fail. In that case you have to	1957	use 64 bit file offsets the programs will fail. In that case you have to
1634	compile libev with the same flags to get binary compatibility. This is	1958	compile libev with the same flags to get binary compatibility. This is
1635	obviously the case with any flags that change the ABI, but the problem is	1959	obviously the case with any flags that change the ABI, but the problem is
1636	most noticably with ev_stat and largefile support.	1960	most noticeably disabled with ev_stat and large file support.
1637		1961
1638	=head3 Inotify	1962	The solution for this is to lobby your distribution maker to make large
		1963	file interfaces available by default (as e.g. FreeBSD does) and not
		1964	optional. Libev cannot simply switch on large file support because it has
		1965	to exchange stat structures with application programs compiled using the
		1966	default compilation environment.
1639		1967
		1968	=head3 Inotify and Kqueue
		1969
1640	When C<inotify (7)> support has been compiled into libev (generally only	1970	When C<inotify (7)> support has been compiled into libev (generally
		1971	only available with Linux 2.6.25 or above due to bugs in earlier
1641	available on Linux) and present at runtime, it will be used to speed up	1972	implementations) and present at runtime, it will be used to speed up
1642	change detection where possible. The inotify descriptor will be created lazily	1973	change detection where possible. The inotify descriptor will be created
1643	when the first C<ev_stat> watcher is being started.	1974	lazily when the first C<ev_stat> watcher is being started.
1644		1975
1645	Inotify presence does not change the semantics of C<ev_stat> watchers	1976	Inotify presence does not change the semantics of C<ev_stat> watchers
1646	except that changes might be detected earlier, and in some cases, to avoid	1977	except that changes might be detected earlier, and in some cases, to avoid
1647	making regular C<stat> calls. Even in the presence of inotify support	1978	making regular C<stat> calls. Even in the presence of inotify support
1648	there are many cases where libev has to resort to regular C<stat> polling.	1979	there are many cases where libev has to resort to regular C<stat> polling,
		1980	but as long as the path exists, libev usually gets away without polling.
1649		1981
1650	(There is no support for kqueue, as apparently it cannot be used to	1982	There is no support for kqueue, as apparently it cannot be used to
1651	implement this functionality, due to the requirement of having a file	1983	implement this functionality, due to the requirement of having a file
1652	descriptor open on the object at all times).	1984	descriptor open on the object at all times, and detecting renames, unlinks
		1985	etc. is difficult.
1653		1986
1654	=head3 The special problem of stat time resolution	1987	=head3 The special problem of stat time resolution
1655		1988
1656	The C<stat ()> syscall only supports full-second resolution portably, and	1989	The C<stat ()> system call only supports full-second resolution portably, and
1657	even on systems where the resolution is higher, many filesystems still	1990	even on systems where the resolution is higher, most file systems still
1658	only support whole seconds.	1991	only support whole seconds.
1659		1992
1660	That means that, if the time is the only thing that changes, you can	1993	That means that, if the time is the only thing that changes, you can
1661	easily miss updates: on the first update, C<ev_stat> detects a change and	1994	easily miss updates: on the first update, C<ev_stat> detects a change and
1662	calls your callback, which does something. When there is another update	1995	calls your callback, which does something. When there is another update
1663	within the same second, C<ev_stat> will be unable to detect it as the stat	1996	within the same second, C<ev_stat> will be unable to detect unless the
1664	data does not change.	1997	stat data does change in other ways (e.g. file size).
1665		1998
1666	The solution to this is to delay acting on a change for slightly more	1999	The solution to this is to delay acting on a change for slightly more
1667	than a second (or till slightly after the next full second boundary), using	2000	than a second (or till slightly after the next full second boundary), using
1668	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2001	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1669	ev_timer_again (loop, w)>).	2002	ev_timer_again (loop, w)>).
…		…
1689	C<path>. The C<interval> is a hint on how quickly a change is expected to	2022	C<path>. The C<interval> is a hint on how quickly a change is expected to
1690	be detected and should normally be specified as C<0> to let libev choose	2023	be detected and should normally be specified as C<0> to let libev choose
1691	a suitable value. The memory pointed to by C<path> must point to the same	2024	a suitable value. The memory pointed to by C<path> must point to the same
1692	path for as long as the watcher is active.	2025	path for as long as the watcher is active.
1693		2026
1694	The callback will receive C<EV_STAT> when a change was detected, relative	2027	The callback will receive an C<EV_STAT> event when a change was detected,
1695	to the attributes at the time the watcher was started (or the last change	2028	relative to the attributes at the time the watcher was started (or the
1696	was detected).	2029	last change was detected).
1697		2030
1698	=item ev_stat_stat (loop, ev_stat *)	2031	=item ev_stat_stat (loop, ev_stat *)
1699		2032
1700	Updates the stat buffer immediately with new values. If you change the	2033	Updates the stat buffer immediately with new values. If you change the
1701	watched path in your callback, you could call this function to avoid	2034	watched path in your callback, you could call this function to avoid
…		…
1722		2055
1723	The specified interval.	2056	The specified interval.
1724		2057
1725	=item const char *path [read-only]	2058	=item const char *path [read-only]
1726		2059
1727	The filesystem path that is being watched.	2060	The file system path that is being watched.
1728		2061
1729	=back	2062	=back
1730		2063
1731	=head3 Examples	2064	=head3 Examples
1732		2065
1733	Example: Watch C</etc/passwd> for attribute changes.	2066	Example: Watch C</etc/passwd> for attribute changes.
1734		2067
1735	static void	2068	static void
1736	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2069	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1737	{	2070	{
1738	/* /etc/passwd changed in some way */	2071	/* /etc/passwd changed in some way */
1739	if (w->attr.st_nlink)	2072	if (w->attr.st_nlink)
1740	{	2073	{
1741	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2074	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1742	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2075	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1743	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2076	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1744	}	2077	}
1745	else	2078	else
1746	/* you shalt not abuse printf for puts */	2079	/* you shalt not abuse printf for puts */
1747	puts ("wow, /etc/passwd is not there, expect problems. "	2080	puts ("wow, /etc/passwd is not there, expect problems. "
1748	"if this is windows, they already arrived\n");	2081	"if this is windows, they already arrived\n");
1749	}	2082	}
1750		2083
1751	...	2084	...
1752	ev_stat passwd;	2085	ev_stat passwd;
1753		2086
1754	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2087	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1755	ev_stat_start (loop, &passwd);	2088	ev_stat_start (loop, &passwd);
1756		2089
1757	Example: Like above, but additionally use a one-second delay so we do not	2090	Example: Like above, but additionally use a one-second delay so we do not
1758	miss updates (however, frequent updates will delay processing, too, so	2091	miss updates (however, frequent updates will delay processing, too, so
1759	one might do the work both on C<ev_stat> callback invocation I<and> on	2092	one might do the work both on C<ev_stat> callback invocation I<and> on
1760	C<ev_timer> callback invocation).	2093	C<ev_timer> callback invocation).
1761		2094
1762	static ev_stat passwd;	2095	static ev_stat passwd;
1763	static ev_timer timer;	2096	static ev_timer timer;
1764		2097
1765	static void	2098	static void
1766	timer_cb (EV_P_ ev_timer *w, int revents)	2099	timer_cb (EV_P_ ev_timer *w, int revents)
1767	{	2100	{
1768	ev_timer_stop (EV_A_ w);	2101	ev_timer_stop (EV_A_ w);
1769		2102
1770	/* now it's one second after the most recent passwd change */	2103	/* now it's one second after the most recent passwd change */
1771	}	2104	}
1772		2105
1773	static void	2106	static void
1774	stat_cb (EV_P_ ev_stat *w, int revents)	2107	stat_cb (EV_P_ ev_stat *w, int revents)
1775	{	2108	{
1776	/* reset the one-second timer */	2109	/* reset the one-second timer */
1777	ev_timer_again (EV_A_ &timer);	2110	ev_timer_again (EV_A_ &timer);
1778	}	2111	}
1779		2112
1780	...	2113	...
1781	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2114	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1782	ev_stat_start (loop, &passwd);	2115	ev_stat_start (loop, &passwd);
1783	ev_timer_init (&timer, timer_cb, 0., 1.02);	2116	ev_timer_init (&timer, timer_cb, 0., 1.02);
1784		2117
1785		2118
1786	=head2 C<ev_idle> - when you've got nothing better to do...	2119	=head2 C<ev_idle> - when you've got nothing better to do...
1787		2120
1788	Idle watchers trigger events when no other events of the same or higher	2121	Idle watchers trigger events when no other events of the same or higher
1789	priority are pending (prepare, check and other idle watchers do not	2122	priority are pending (prepare, check and other idle watchers do not count
1790	count).	2123	as receiving "events").
1791		2124
1792	That is, as long as your process is busy handling sockets or timeouts	2125	That is, as long as your process is busy handling sockets or timeouts
1793	(or even signals, imagine) of the same or higher priority it will not be	2126	(or even signals, imagine) of the same or higher priority it will not be
1794	triggered. But when your process is idle (or only lower-priority watchers	2127	triggered. But when your process is idle (or only lower-priority watchers
1795	are pending), the idle watchers are being called once per event loop	2128	are pending), the idle watchers are being called once per event loop
…		…
1819	=head3 Examples	2152	=head3 Examples
1820		2153
1821	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2154	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1822	callback, free it. Also, use no error checking, as usual.	2155	callback, free it. Also, use no error checking, as usual.
1823		2156
1824	static void	2157	static void
1825	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2158	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1826	{	2159	{
1827	free (w);	2160	free (w);
1828	// now do something you wanted to do when the program has	2161	// now do something you wanted to do when the program has
1829	// no longer anything immediate to do.	2162	// no longer anything immediate to do.
1830	}	2163	}
1831		2164
1832	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2165	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1833	ev_idle_init (idle_watcher, idle_cb);	2166	ev_idle_init (idle_watcher, idle_cb);
1834	ev_idle_start (loop, idle_cb);	2167	ev_idle_start (loop, idle_cb);
1835		2168
1836		2169
1837	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2170	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1838		2171
1839	Prepare and check watchers are usually (but not always) used in tandem:	2172	Prepare and check watchers are usually (but not always) used in pairs:
1840	prepare watchers get invoked before the process blocks and check watchers	2173	prepare watchers get invoked before the process blocks and check watchers
1841	afterwards.	2174	afterwards.
1842		2175
1843	You I<must not> call C<ev_loop> or similar functions that enter	2176	You I<must not> call C<ev_loop> or similar functions that enter
1844	the current event loop from either C<ev_prepare> or C<ev_check>	2177	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1847	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2180	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1848	C<ev_check> so if you have one watcher of each kind they will always be	2181	C<ev_check> so if you have one watcher of each kind they will always be
1849	called in pairs bracketing the blocking call.	2182	called in pairs bracketing the blocking call.
1850		2183
1851	Their main purpose is to integrate other event mechanisms into libev and	2184	Their main purpose is to integrate other event mechanisms into libev and
1852	their use is somewhat advanced. This could be used, for example, to track	2185	their use is somewhat advanced. They could be used, for example, to track
1853	variable changes, implement your own watchers, integrate net-snmp or a	2186	variable changes, implement your own watchers, integrate net-snmp or a
1854	coroutine library and lots more. They are also occasionally useful if	2187	coroutine library and lots more. They are also occasionally useful if
1855	you cache some data and want to flush it before blocking (for example,	2188	you cache some data and want to flush it before blocking (for example,
1856	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2189	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1857	watcher).	2190	watcher).
1858		2191
1859	This is done by examining in each prepare call which file descriptors need	2192	This is done by examining in each prepare call which file descriptors
1860	to be watched by the other library, registering C<ev_io> watchers for	2193	need to be watched by the other library, registering C<ev_io> watchers
1861	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2194	for them and starting an C<ev_timer> watcher for any timeouts (many
1862	provide just this functionality). Then, in the check watcher you check for	2195	libraries provide exactly this functionality). Then, in the check watcher,
1863	any events that occured (by checking the pending status of all watchers	2196	you check for any events that occurred (by checking the pending status
1864	and stopping them) and call back into the library. The I/O and timer	2197	of all watchers and stopping them) and call back into the library. The
1865	callbacks will never actually be called (but must be valid nevertheless,	2198	I/O and timer callbacks will never actually be called (but must be valid
1866	because you never know, you know?).	2199	nevertheless, because you never know, you know?).
1867		2200
1868	As another example, the Perl Coro module uses these hooks to integrate	2201	As another example, the Perl Coro module uses these hooks to integrate
1869	coroutines into libev programs, by yielding to other active coroutines	2202	coroutines into libev programs, by yielding to other active coroutines
1870	during each prepare and only letting the process block if no coroutines	2203	during each prepare and only letting the process block if no coroutines
1871	are ready to run (it's actually more complicated: it only runs coroutines	2204	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1874	loop from blocking if lower-priority coroutines are active, thus mapping	2207	loop from blocking if lower-priority coroutines are active, thus mapping
1875	low-priority coroutines to idle/background tasks).	2208	low-priority coroutines to idle/background tasks).
1876		2209
1877	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2210	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1878	priority, to ensure that they are being run before any other watchers	2211	priority, to ensure that they are being run before any other watchers
		2212	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2213
1879	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2214	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1880	too) should not activate ("feed") events into libev. While libev fully	2215	activate ("feed") events into libev. While libev fully supports this, they
1881	supports this, they might get executed before other C<ev_check> watchers	2216	might get executed before other C<ev_check> watchers did their job. As
1882	did their job. As C<ev_check> watchers are often used to embed other	2217	C<ev_check> watchers are often used to embed other (non-libev) event
1883	(non-libev) event loops those other event loops might be in an unusable	2218	loops those other event loops might be in an unusable state until their
1884	state until their C<ev_check> watcher ran (always remind yourself to	2219	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1885	coexist peacefully with others).	2220	others).
1886		2221
1887	=head3 Watcher-Specific Functions and Data Members	2222	=head3 Watcher-Specific Functions and Data Members
1888		2223
1889	=over 4	2224	=over 4
1890		2225
…		…
1892		2227
1893	=item ev_check_init (ev_check *, callback)	2228	=item ev_check_init (ev_check *, callback)
1894		2229
1895	Initialises and configures the prepare or check watcher - they have no	2230	Initialises and configures the prepare or check watcher - they have no
1896	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2231	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1897	macros, but using them is utterly, utterly and completely pointless.	2232	macros, but using them is utterly, utterly, utterly and completely
		2233	pointless.
1898		2234
1899	=back	2235	=back
1900		2236
1901	=head3 Examples	2237	=head3 Examples
1902		2238
…		…
1911	and in a check watcher, destroy them and call into libadns. What follows	2247	and in a check watcher, destroy them and call into libadns. What follows
1912	is pseudo-code only of course. This requires you to either use a low	2248	is pseudo-code only of course. This requires you to either use a low
1913	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2249	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1914	the callbacks for the IO/timeout watchers might not have been called yet.	2250	the callbacks for the IO/timeout watchers might not have been called yet.
1915		2251
1916	static ev_io iow [nfd];	2252	static ev_io iow [nfd];
1917	static ev_timer tw;	2253	static ev_timer tw;
1918		2254
1919	static void	2255	static void
1920	io_cb (ev_loop *loop, ev_io *w, int revents)	2256	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1921	{	2257	{
1922	}	2258	}
1923		2259
1924	// create io watchers for each fd and a timer before blocking	2260	// create io watchers for each fd and a timer before blocking
1925	static void	2261	static void
1926	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2262	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1927	{	2263	{
1928	int timeout = 3600000;	2264	int timeout = 3600000;
1929	struct pollfd fds [nfd];	2265	struct pollfd fds [nfd];
1930	// actual code will need to loop here and realloc etc.	2266	// actual code will need to loop here and realloc etc.
1931	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2267	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1932		2268
1933	/* the callback is illegal, but won't be called as we stop during check */	2269	/* the callback is illegal, but won't be called as we stop during check */
1934	ev_timer_init (&tw, 0, timeout * 1e-3);	2270	ev_timer_init (&tw, 0, timeout * 1e-3);
1935	ev_timer_start (loop, &tw);	2271	ev_timer_start (loop, &tw);
1936		2272
1937	// create one ev_io per pollfd	2273	// create one ev_io per pollfd
1938	for (int i = 0; i < nfd; ++i)	2274	for (int i = 0; i < nfd; ++i)
1939	{	2275	{
1940	ev_io_init (iow + i, io_cb, fds [i].fd,	2276	ev_io_init (iow + i, io_cb, fds [i].fd,
1941	((fds [i].events & POLLIN ? EV_READ : 0)	2277	((fds [i].events & POLLIN ? EV_READ : 0)
1942	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2278	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1943		2279
1944	fds [i].revents = 0;	2280	fds [i].revents = 0;
1945	ev_io_start (loop, iow + i);	2281	ev_io_start (loop, iow + i);
1946	}	2282	}
1947	}	2283	}
1948		2284
1949	// stop all watchers after blocking	2285	// stop all watchers after blocking
1950	static void	2286	static void
1951	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2287	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1952	{	2288	{
1953	ev_timer_stop (loop, &tw);	2289	ev_timer_stop (loop, &tw);
1954		2290
1955	for (int i = 0; i < nfd; ++i)	2291	for (int i = 0; i < nfd; ++i)
1956	{	2292	{
1957	// set the relevant poll flags	2293	// set the relevant poll flags
1958	// could also call adns_processreadable etc. here	2294	// could also call adns_processreadable etc. here
1959	struct pollfd *fd = fds + i;	2295	struct pollfd *fd = fds + i;
1960	int revents = ev_clear_pending (iow + i);	2296	int revents = ev_clear_pending (iow + i);
1961	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2297	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1962	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2298	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1963		2299
1964	// now stop the watcher	2300	// now stop the watcher
1965	ev_io_stop (loop, iow + i);	2301	ev_io_stop (loop, iow + i);
1966	}	2302	}
1967		2303
1968	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2304	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1969	}	2305	}
1970		2306
1971	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2307	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1972	in the prepare watcher and would dispose of the check watcher.	2308	in the prepare watcher and would dispose of the check watcher.
1973		2309
1974	Method 3: If the module to be embedded supports explicit event	2310	Method 3: If the module to be embedded supports explicit event
1975	notification (adns does), you can also make use of the actual watcher	2311	notification (libadns does), you can also make use of the actual watcher
1976	callbacks, and only destroy/create the watchers in the prepare watcher.	2312	callbacks, and only destroy/create the watchers in the prepare watcher.
1977		2313
1978	static void	2314	static void
1979	timer_cb (EV_P_ ev_timer *w, int revents)	2315	timer_cb (EV_P_ ev_timer *w, int revents)
1980	{	2316	{
1981	adns_state ads = (adns_state)w->data;	2317	adns_state ads = (adns_state)w->data;
1982	update_now (EV_A);	2318	update_now (EV_A);
1983		2319
1984	adns_processtimeouts (ads, &tv_now);	2320	adns_processtimeouts (ads, &tv_now);
1985	}	2321	}
1986		2322
1987	static void	2323	static void
1988	io_cb (EV_P_ ev_io *w, int revents)	2324	io_cb (EV_P_ ev_io *w, int revents)
1989	{	2325	{
1990	adns_state ads = (adns_state)w->data;	2326	adns_state ads = (adns_state)w->data;
1991	update_now (EV_A);	2327	update_now (EV_A);
1992		2328
1993	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2329	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1994	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2330	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1995	}	2331	}
1996		2332
1997	// do not ever call adns_afterpoll	2333	// do not ever call adns_afterpoll
1998		2334
1999	Method 4: Do not use a prepare or check watcher because the module you	2335	Method 4: Do not use a prepare or check watcher because the module you
2000	want to embed is too inflexible to support it. Instead, youc na override	2336	want to embed is not flexible enough to support it. Instead, you can
2001	their poll function. The drawback with this solution is that the main	2337	override their poll function. The drawback with this solution is that the
2002	loop is now no longer controllable by EV. The C<Glib::EV> module does	2338	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2003	this.	2339	this approach, effectively embedding EV as a client into the horrible
		2340	libglib event loop.
2004		2341
2005	static gint	2342	static gint
2006	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2343	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2007	{	2344	{
2008	int got_events = 0;	2345	int got_events = 0;
2009		2346
2010	for (n = 0; n < nfds; ++n)	2347	for (n = 0; n < nfds; ++n)
2011	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2348	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2012		2349
2013	if (timeout >= 0)	2350	if (timeout >= 0)
2014	// create/start timer	2351	// create/start timer
2015		2352
2016	// poll	2353	// poll
2017	ev_loop (EV_A_ 0);	2354	ev_loop (EV_A_ 0);
2018		2355
2019	// stop timer again	2356	// stop timer again
2020	if (timeout >= 0)	2357	if (timeout >= 0)
2021	ev_timer_stop (EV_A_ &to);	2358	ev_timer_stop (EV_A_ &to);
2022		2359
2023	// stop io watchers again - their callbacks should have set	2360	// stop io watchers again - their callbacks should have set
2024	for (n = 0; n < nfds; ++n)	2361	for (n = 0; n < nfds; ++n)
2025	ev_io_stop (EV_A_ iow [n]);	2362	ev_io_stop (EV_A_ iow [n]);
2026		2363
2027	return got_events;	2364	return got_events;
2028	}	2365	}
2029		2366
2030		2367
2031	=head2 C<ev_embed> - when one backend isn't enough...	2368	=head2 C<ev_embed> - when one backend isn't enough...
2032		2369
2033	This is a rather advanced watcher type that lets you embed one event loop	2370	This is a rather advanced watcher type that lets you embed one event loop
…		…
2039	prioritise I/O.	2376	prioritise I/O.
2040		2377
2041	As an example for a bug workaround, the kqueue backend might only support	2378	As an example for a bug workaround, the kqueue backend might only support
2042	sockets on some platform, so it is unusable as generic backend, but you	2379	sockets on some platform, so it is unusable as generic backend, but you
2043	still want to make use of it because you have many sockets and it scales	2380	still want to make use of it because you have many sockets and it scales
2044	so nicely. In this case, you would create a kqueue-based loop and embed it	2381	so nicely. In this case, you would create a kqueue-based loop and embed
2045	into your default loop (which might use e.g. poll). Overall operation will	2382	it into your default loop (which might use e.g. poll). Overall operation
2046	be a bit slower because first libev has to poll and then call kevent, but	2383	will be a bit slower because first libev has to call C<poll> and then
2047	at least you can use both at what they are best.	2384	C<kevent>, but at least you can use both mechanisms for what they are
		2385	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2048		2386
2049	As for prioritising I/O: rarely you have the case where some fds have	2387	As for prioritising I/O: under rare circumstances you have the case where
2050	to be watched and handled very quickly (with low latency), and even	2388	some fds have to be watched and handled very quickly (with low latency),
2051	priorities and idle watchers might have too much overhead. In this case	2389	and even priorities and idle watchers might have too much overhead. In
2052	you would put all the high priority stuff in one loop and all the rest in	2390	this case you would put all the high priority stuff in one loop and all
2053	a second one, and embed the second one in the first.	2391	the rest in a second one, and embed the second one in the first.
2054		2392
2055	As long as the watcher is active, the callback will be invoked every time	2393	As long as the watcher is active, the callback will be invoked every time
2056	there might be events pending in the embedded loop. The callback must then	2394	there might be events pending in the embedded loop. The callback must then
2057	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2395	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2058	their callbacks (you could also start an idle watcher to give the embedded	2396	their callbacks (you could also start an idle watcher to give the embedded
…		…
2066	interested in that.	2404	interested in that.
2067		2405
2068	Also, there have not currently been made special provisions for forking:	2406	Also, there have not currently been made special provisions for forking:
2069	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2407	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2070	but you will also have to stop and restart any C<ev_embed> watchers	2408	but you will also have to stop and restart any C<ev_embed> watchers
2071	yourself.	2409	yourself - but you can use a fork watcher to handle this automatically,
		2410	and future versions of libev might do just that.
2072		2411
2073	Unfortunately, not all backends are embeddable, only the ones returned by	2412	Unfortunately, not all backends are embeddable: only the ones returned by
2074	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2413	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2075	portable one.	2414	portable one.
2076		2415
2077	So when you want to use this feature you will always have to be prepared	2416	So when you want to use this feature you will always have to be prepared
2078	that you cannot get an embeddable loop. The recommended way to get around	2417	that you cannot get an embeddable loop. The recommended way to get around
2079	this is to have a separate variables for your embeddable loop, try to	2418	this is to have a separate variables for your embeddable loop, try to
2080	create it, and if that fails, use the normal loop for everything.	2419	create it, and if that fails, use the normal loop for everything.
2081		2420
		2421	=head3 C<ev_embed> and fork
		2422
		2423	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2424	automatically be applied to the embedded loop as well, so no special
		2425	fork handling is required in that case. When the watcher is not running,
		2426	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2427	as applicable.
		2428
2082	=head3 Watcher-Specific Functions and Data Members	2429	=head3 Watcher-Specific Functions and Data Members
2083		2430
2084	=over 4	2431	=over 4
2085		2432
2086	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2433	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2089		2436
2090	Configures the watcher to embed the given loop, which must be	2437	Configures the watcher to embed the given loop, which must be
2091	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2438	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2092	invoked automatically, otherwise it is the responsibility of the callback	2439	invoked automatically, otherwise it is the responsibility of the callback
2093	to invoke it (it will continue to be called until the sweep has been done,	2440	to invoke it (it will continue to be called until the sweep has been done,
2094	if you do not want thta, you need to temporarily stop the embed watcher).	2441	if you do not want that, you need to temporarily stop the embed watcher).
2095		2442
2096	=item ev_embed_sweep (loop, ev_embed *)	2443	=item ev_embed_sweep (loop, ev_embed *)
2097		2444
2098	Make a single, non-blocking sweep over the embedded loop. This works	2445	Make a single, non-blocking sweep over the embedded loop. This works
2099	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2446	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2100	apropriate way for embedded loops.	2447	appropriate way for embedded loops.
2101		2448
2102	=item struct ev_loop *other [read-only]	2449	=item struct ev_loop *other [read-only]
2103		2450
2104	The embedded event loop.	2451	The embedded event loop.
2105		2452
…		…
2107		2454
2108	=head3 Examples	2455	=head3 Examples
2109		2456
2110	Example: Try to get an embeddable event loop and embed it into the default	2457	Example: Try to get an embeddable event loop and embed it into the default
2111	event loop. If that is not possible, use the default loop. The default	2458	event loop. If that is not possible, use the default loop. The default
2112	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2459	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2113	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2460	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2114	used).	2461	used).
2115		2462
2116	struct ev_loop *loop_hi = ev_default_init (0);	2463	struct ev_loop *loop_hi = ev_default_init (0);
2117	struct ev_loop *loop_lo = 0;	2464	struct ev_loop *loop_lo = 0;
2118	struct ev_embed embed;	2465	ev_embed embed;
2119		2466
2120	// see if there is a chance of getting one that works	2467	// see if there is a chance of getting one that works
2121	// (remember that a flags value of 0 means autodetection)	2468	// (remember that a flags value of 0 means autodetection)
2122	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2469	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2123	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2470	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2124	: 0;	2471	: 0;
2125		2472
2126	// if we got one, then embed it, otherwise default to loop_hi	2473	// if we got one, then embed it, otherwise default to loop_hi
2127	if (loop_lo)	2474	if (loop_lo)
2128	{	2475	{
2129	ev_embed_init (&embed, 0, loop_lo);	2476	ev_embed_init (&embed, 0, loop_lo);
2130	ev_embed_start (loop_hi, &embed);	2477	ev_embed_start (loop_hi, &embed);
2131	}	2478	}
2132	else	2479	else
2133	loop_lo = loop_hi;	2480	loop_lo = loop_hi;
2134		2481
2135	Example: Check if kqueue is available but not recommended and create	2482	Example: Check if kqueue is available but not recommended and create
2136	a kqueue backend for use with sockets (which usually work with any	2483	a kqueue backend for use with sockets (which usually work with any
2137	kqueue implementation). Store the kqueue/socket-only event loop in	2484	kqueue implementation). Store the kqueue/socket-only event loop in
2138	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2485	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2139		2486
2140	struct ev_loop *loop = ev_default_init (0);	2487	struct ev_loop *loop = ev_default_init (0);
2141	struct ev_loop *loop_socket = 0;	2488	struct ev_loop *loop_socket = 0;
2142	struct ev_embed embed;	2489	ev_embed embed;
2143		2490
2144	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2491	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2145	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2492	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2146	{	2493	{
2147	ev_embed_init (&embed, 0, loop_socket);	2494	ev_embed_init (&embed, 0, loop_socket);
2148	ev_embed_start (loop, &embed);	2495	ev_embed_start (loop, &embed);
2149	}	2496	}
2150		2497
2151	if (!loop_socket)	2498	if (!loop_socket)
2152	loop_socket = loop;	2499	loop_socket = loop;
2153		2500
2154	// now use loop_socket for all sockets, and loop for everything else	2501	// now use loop_socket for all sockets, and loop for everything else
2155		2502
2156		2503
2157	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2504	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2158		2505
2159	Fork watchers are called when a C<fork ()> was detected (usually because	2506	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2203	is that the author does not know of a simple (or any) algorithm for a	2550	is that the author does not know of a simple (or any) algorithm for a
2204	multiple-writer-single-reader queue that works in all cases and doesn't	2551	multiple-writer-single-reader queue that works in all cases and doesn't
2205	need elaborate support such as pthreads.	2552	need elaborate support such as pthreads.
2206		2553
2207	That means that if you want to queue data, you have to provide your own	2554	That means that if you want to queue data, you have to provide your own
2208	queue. But at least I can tell you would implement locking around your	2555	queue. But at least I can tell you how to implement locking around your
2209	queue:	2556	queue:
2210		2557
2211	=over 4	2558	=over 4
2212		2559
2213	=item queueing from a signal handler context	2560	=item queueing from a signal handler context
2214		2561
2215	To implement race-free queueing, you simply add to the queue in the signal	2562	To implement race-free queueing, you simply add to the queue in the signal
2216	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2563	handler but you block the signal handler in the watcher callback. Here is
2217	some fictitiuous SIGUSR1 handler:	2564	an example that does that for some fictitious SIGUSR1 handler:
2218		2565
2219	static ev_async mysig;	2566	static ev_async mysig;
2220		2567
2221	static void	2568	static void
2222	sigusr1_handler (void)	2569	sigusr1_handler (void)
…		…
2289		2636
2290	=item ev_async_init (ev_async *, callback)	2637	=item ev_async_init (ev_async *, callback)
2291		2638
2292	Initialises and configures the async watcher - it has no parameters of any	2639	Initialises and configures the async watcher - it has no parameters of any
2293	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2640	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2294	believe me.	2641	trust me.
2295		2642
2296	=item ev_async_send (loop, ev_async *)	2643	=item ev_async_send (loop, ev_async *)
2297		2644
2298	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2645	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2299	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2646	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2300	C<ev_feed_event>, this call is safe to do in other threads, signal or	2647	C<ev_feed_event>, this call is safe to do from other threads, signal or
2301	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2648	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2302	section below on what exactly this means).	2649	section below on what exactly this means).
2303		2650
2304	This call incurs the overhead of a syscall only once per loop iteration,	2651	This call incurs the overhead of a system call only once per loop iteration,
2305	so while the overhead might be noticable, it doesn't apply to repeated	2652	so while the overhead might be noticeable, it doesn't apply to repeated
2306	calls to C<ev_async_send>.	2653	calls to C<ev_async_send>.
2307		2654
2308	=item bool = ev_async_pending (ev_async *)	2655	=item bool = ev_async_pending (ev_async *)
2309		2656
2310	Returns a non-zero value when C<ev_async_send> has been called on the	2657	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2312	event loop.	2659	event loop.
2313		2660
2314	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2661	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2315	the loop iterates next and checks for the watcher to have become active,	2662	the loop iterates next and checks for the watcher to have become active,
2316	it will reset the flag again. C<ev_async_pending> can be used to very	2663	it will reset the flag again. C<ev_async_pending> can be used to very
2317	quickly check wether invoking the loop might be a good idea.	2664	quickly check whether invoking the loop might be a good idea.
2318		2665
2319	Not that this does I<not> check wether the watcher itself is pending, only	2666	Not that this does I<not> check whether the watcher itself is pending, only
2320	wether it has been requested to make this watcher pending.	2667	whether it has been requested to make this watcher pending.
2321		2668
2322	=back	2669	=back
2323		2670
2324		2671
2325	=head1 OTHER FUNCTIONS	2672	=head1 OTHER FUNCTIONS
…		…
2329	=over 4	2676	=over 4
2330		2677
2331	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2678	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2332		2679
2333	This function combines a simple timer and an I/O watcher, calls your	2680	This function combines a simple timer and an I/O watcher, calls your
2334	callback on whichever event happens first and automatically stop both	2681	callback on whichever event happens first and automatically stops both
2335	watchers. This is useful if you want to wait for a single event on an fd	2682	watchers. This is useful if you want to wait for a single event on an fd
2336	or timeout without having to allocate/configure/start/stop/free one or	2683	or timeout without having to allocate/configure/start/stop/free one or
2337	more watchers yourself.	2684	more watchers yourself.
2338		2685
2339	If C<fd> is less than 0, then no I/O watcher will be started and events	2686	If C<fd> is less than 0, then no I/O watcher will be started and the
2340	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2687	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2341	C<events> set will be craeted and started.	2688	the given C<fd> and C<events> set will be created and started.
2342		2689
2343	If C<timeout> is less than 0, then no timeout watcher will be	2690	If C<timeout> is less than 0, then no timeout watcher will be
2344	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2691	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2345	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2692	repeat = 0) will be started. C<0> is a valid timeout.
2346	dubious value.
2347		2693
2348	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2694	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2349	passed an C<revents> set like normal event callbacks (a combination of	2695	passed an C<revents> set like normal event callbacks (a combination of
2350	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2696	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2351	value passed to C<ev_once>:	2697	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2698	a timeout and an io event at the same time - you probably should give io
		2699	events precedence.
2352		2700
		2701	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2702
2353	static void stdin_ready (int revents, void *arg)	2703	static void stdin_ready (int revents, void *arg)
2354	{	2704	{
2355	if (revents & EV_TIMEOUT)
2356	/* doh, nothing entered */;
2357	else if (revents & EV_READ)	2705	if (revents & EV_READ)
2358	/* stdin might have data for us, joy! */;	2706	/* stdin might have data for us, joy! */;
		2707	else if (revents & EV_TIMEOUT)
		2708	/* doh, nothing entered */;
2359	}	2709	}
2360		2710
2361	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2711	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2362		2712
2363	=item ev_feed_event (ev_loop *, watcher *, int revents)	2713	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2364		2714
2365	Feeds the given event set into the event loop, as if the specified event	2715	Feeds the given event set into the event loop, as if the specified event
2366	had happened for the specified watcher (which must be a pointer to an	2716	had happened for the specified watcher (which must be a pointer to an
2367	initialised but not necessarily started event watcher).	2717	initialised but not necessarily started event watcher).
2368		2718
2369	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2719	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2370		2720
2371	Feed an event on the given fd, as if a file descriptor backend detected	2721	Feed an event on the given fd, as if a file descriptor backend detected
2372	the given events it.	2722	the given events it.
2373		2723
2374	=item ev_feed_signal_event (ev_loop *loop, int signum)	2724	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2375		2725
2376	Feed an event as if the given signal occured (C<loop> must be the default	2726	Feed an event as if the given signal occurred (C<loop> must be the default
2377	loop!).	2727	loop!).
2378		2728
2379	=back	2729	=back
2380		2730
2381		2731
…		…
2410	=back	2760	=back
2411		2761
2412	=head1 C++ SUPPORT	2762	=head1 C++ SUPPORT
2413		2763
2414	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2764	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2415	you to use some convinience methods to start/stop watchers and also change	2765	you to use some convenience methods to start/stop watchers and also change
2416	the callback model to a model using method callbacks on objects.	2766	the callback model to a model using method callbacks on objects.
2417		2767
2418	To use it,	2768	To use it,
2419		2769
2420	#include <ev++.h>	2770	#include <ev++.h>
2421		2771
2422	This automatically includes F<ev.h> and puts all of its definitions (many	2772	This automatically includes F<ev.h> and puts all of its definitions (many
2423	of them macros) into the global namespace. All C++ specific things are	2773	of them macros) into the global namespace. All C++ specific things are
2424	put into the C<ev> namespace. It should support all the same embedding	2774	put into the C<ev> namespace. It should support all the same embedding
2425	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2775	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2492	your compiler is good :), then the method will be fully inlined into the	2842	your compiler is good :), then the method will be fully inlined into the
2493	thunking function, making it as fast as a direct C callback.	2843	thunking function, making it as fast as a direct C callback.
2494		2844
2495	Example: simple class declaration and watcher initialisation	2845	Example: simple class declaration and watcher initialisation
2496		2846
2497	struct myclass	2847	struct myclass
2498	{	2848	{
2499	void io_cb (ev::io &w, int revents) { }	2849	void io_cb (ev::io &w, int revents) { }
2500	}	2850	}
2501		2851
2502	myclass obj;	2852	myclass obj;
2503	ev::io iow;	2853	ev::io iow;
2504	iow.set <myclass, &myclass::io_cb> (&obj);	2854	iow.set <myclass, &myclass::io_cb> (&obj);
2505		2855
2506	=item w->set<function> (void *data = 0)	2856	=item w->set<function> (void *data = 0)
2507		2857
2508	Also sets a callback, but uses a static method or plain function as	2858	Also sets a callback, but uses a static method or plain function as
2509	callback. The optional C<data> argument will be stored in the watcher's	2859	callback. The optional C<data> argument will be stored in the watcher's
…		…
2511		2861
2512	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2862	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2513		2863
2514	See the method-C<set> above for more details.	2864	See the method-C<set> above for more details.
2515		2865
2516	Example:	2866	Example: Use a plain function as callback.
2517		2867
2518	static void io_cb (ev::io &w, int revents) { }	2868	static void io_cb (ev::io &w, int revents) { }
2519	iow.set <io_cb> ();	2869	iow.set <io_cb> ();
2520		2870
2521	=item w->set (struct ev_loop *)	2871	=item w->set (struct ev_loop *)
2522		2872
2523	Associates a different C<struct ev_loop> with this watcher. You can only	2873	Associates a different C<struct ev_loop> with this watcher. You can only
2524	do this when the watcher is inactive (and not pending either).	2874	do this when the watcher is inactive (and not pending either).
2525		2875
2526	=item w->set ([args])	2876	=item w->set ([arguments])
2527		2877
2528	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2878	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2529	called at least once. Unlike the C counterpart, an active watcher gets	2879	called at least once. Unlike the C counterpart, an active watcher gets
2530	automatically stopped and restarted when reconfiguring it with this	2880	automatically stopped and restarted when reconfiguring it with this
2531	method.	2881	method.
2532		2882
2533	=item w->start ()	2883	=item w->start ()
…		…
2557	=back	2907	=back
2558		2908
2559	Example: Define a class with an IO and idle watcher, start one of them in	2909	Example: Define a class with an IO and idle watcher, start one of them in
2560	the constructor.	2910	the constructor.
2561		2911
2562	class myclass	2912	class myclass
2563	{	2913	{
2564	ev::io io; void io_cb (ev::io &w, int revents);	2914	ev::io io ; void io_cb (ev::io &w, int revents);
2565	ev:idle idle void idle_cb (ev::idle &w, int revents);	2915	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2566		2916
2567	myclass (int fd)	2917	myclass (int fd)
2568	{	2918	{
2569	io .set <myclass, &myclass::io_cb > (this);	2919	io .set <myclass, &myclass::io_cb > (this);
2570	idle.set <myclass, &myclass::idle_cb> (this);	2920	idle.set <myclass, &myclass::idle_cb> (this);
2571		2921
2572	io.start (fd, ev::READ);	2922	io.start (fd, ev::READ);
2573	}	2923	}
2574	};	2924	};
2575		2925
2576		2926
2577	=head1 OTHER LANGUAGE BINDINGS	2927	=head1 OTHER LANGUAGE BINDINGS
2578		2928
2579	Libev does not offer other language bindings itself, but bindings for a	2929	Libev does not offer other language bindings itself, but bindings for a
2580	numbe rof languages exist in the form of third-party packages. If you know	2930	number of languages exist in the form of third-party packages. If you know
2581	any interesting language binding in addition to the ones listed here, drop	2931	any interesting language binding in addition to the ones listed here, drop
2582	me a note.	2932	me a note.
2583		2933
2584	=over 4	2934	=over 4
2585		2935
2586	=item Perl	2936	=item Perl
2587		2937
2588	The EV module implements the full libev API and is actually used to test	2938	The EV module implements the full libev API and is actually used to test
2589	libev. EV is developed together with libev. Apart from the EV core module,	2939	libev. EV is developed together with libev. Apart from the EV core module,
2590	there are additional modules that implement libev-compatible interfaces	2940	there are additional modules that implement libev-compatible interfaces
2591	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2941	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2592	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2942	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2943	and C<EV::Glib>).
2593		2944
2594	It can be found and installed via CPAN, its homepage is found at	2945	It can be found and installed via CPAN, its homepage is at
2595	L<http://software.schmorp.de/pkg/EV>.	2946	L<http://software.schmorp.de/pkg/EV>.
2596		2947
		2948	=item Python
		2949
		2950	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2951	seems to be quite complete and well-documented. Note, however, that the
		2952	patch they require for libev is outright dangerous as it breaks the ABI
		2953	for everybody else, and therefore, should never be applied in an installed
		2954	libev (if python requires an incompatible ABI then it needs to embed
		2955	libev).
		2956
2597	=item Ruby	2957	=item Ruby
2598		2958
2599	Tony Arcieri has written a ruby extension that offers access to a subset	2959	Tony Arcieri has written a ruby extension that offers access to a subset
2600	of the libev API and adds filehandle abstractions, asynchronous DNS and	2960	of the libev API and adds file handle abstractions, asynchronous DNS and
2601	more on top of it. It can be found via gem servers. Its homepage is at	2961	more on top of it. It can be found via gem servers. Its homepage is at
2602	L<http://rev.rubyforge.org/>.	2962	L<http://rev.rubyforge.org/>.
2603		2963
2604	=item D	2964	=item D
2605		2965
2606	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2966	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2607	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2967	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2968
		2969	=item Ocaml
		2970
		2971	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2972	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2608		2973
2609	=back	2974	=back
2610		2975
2611		2976
2612	=head1 MACRO MAGIC	2977	=head1 MACRO MAGIC
2613		2978
2614	Libev can be compiled with a variety of options, the most fundamantal	2979	Libev can be compiled with a variety of options, the most fundamental
2615	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2980	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2616	functions and callbacks have an initial C<struct ev_loop *> argument.	2981	functions and callbacks have an initial C<struct ev_loop *> argument.
2617		2982
2618	To make it easier to write programs that cope with either variant, the	2983	To make it easier to write programs that cope with either variant, the
2619	following macros are defined:	2984	following macros are defined:
…		…
2624		2989
2625	This provides the loop I<argument> for functions, if one is required ("ev	2990	This provides the loop I<argument> for functions, if one is required ("ev
2626	loop argument"). The C<EV_A> form is used when this is the sole argument,	2991	loop argument"). The C<EV_A> form is used when this is the sole argument,
2627	C<EV_A_> is used when other arguments are following. Example:	2992	C<EV_A_> is used when other arguments are following. Example:
2628		2993
2629	ev_unref (EV_A);	2994	ev_unref (EV_A);
2630	ev_timer_add (EV_A_ watcher);	2995	ev_timer_add (EV_A_ watcher);
2631	ev_loop (EV_A_ 0);	2996	ev_loop (EV_A_ 0);
2632		2997
2633	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2998	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2634	which is often provided by the following macro.	2999	which is often provided by the following macro.
2635		3000
2636	=item C<EV_P>, C<EV_P_>	3001	=item C<EV_P>, C<EV_P_>
2637		3002
2638	This provides the loop I<parameter> for functions, if one is required ("ev	3003	This provides the loop I<parameter> for functions, if one is required ("ev
2639	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3004	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2640	C<EV_P_> is used when other parameters are following. Example:	3005	C<EV_P_> is used when other parameters are following. Example:
2641		3006
2642	// this is how ev_unref is being declared	3007	// this is how ev_unref is being declared
2643	static void ev_unref (EV_P);	3008	static void ev_unref (EV_P);
2644		3009
2645	// this is how you can declare your typical callback	3010	// this is how you can declare your typical callback
2646	static void cb (EV_P_ ev_timer *w, int revents)	3011	static void cb (EV_P_ ev_timer *w, int revents)
2647		3012
2648	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3013	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2649	suitable for use with C<EV_A>.	3014	suitable for use with C<EV_A>.
2650		3015
2651	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3016	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2667		3032
2668	Example: Declare and initialise a check watcher, utilising the above	3033	Example: Declare and initialise a check watcher, utilising the above
2669	macros so it will work regardless of whether multiple loops are supported	3034	macros so it will work regardless of whether multiple loops are supported
2670	or not.	3035	or not.
2671		3036
2672	static void	3037	static void
2673	check_cb (EV_P_ ev_timer *w, int revents)	3038	check_cb (EV_P_ ev_timer *w, int revents)
2674	{	3039	{
2675	ev_check_stop (EV_A_ w);	3040	ev_check_stop (EV_A_ w);
2676	}	3041	}
2677		3042
2678	ev_check check;	3043	ev_check check;
2679	ev_check_init (&check, check_cb);	3044	ev_check_init (&check, check_cb);
2680	ev_check_start (EV_DEFAULT_ &check);	3045	ev_check_start (EV_DEFAULT_ &check);
2681	ev_loop (EV_DEFAULT_ 0);	3046	ev_loop (EV_DEFAULT_ 0);
2682		3047
2683	=head1 EMBEDDING	3048	=head1 EMBEDDING
2684		3049
2685	Libev can (and often is) directly embedded into host	3050	Libev can (and often is) directly embedded into host
2686	applications. Examples of applications that embed it include the Deliantra	3051	applications. Examples of applications that embed it include the Deliantra
…		…
2693	libev somewhere in your source tree).	3058	libev somewhere in your source tree).
2694		3059
2695	=head2 FILESETS	3060	=head2 FILESETS
2696		3061
2697	Depending on what features you need you need to include one or more sets of files	3062	Depending on what features you need you need to include one or more sets of files
2698	in your app.	3063	in your application.
2699		3064
2700	=head3 CORE EVENT LOOP	3065	=head3 CORE EVENT LOOP
2701		3066
2702	To include only the libev core (all the C<ev_*> functions), with manual	3067	To include only the libev core (all the C<ev_*> functions), with manual
2703	configuration (no autoconf):	3068	configuration (no autoconf):
2704		3069
2705	#define EV_STANDALONE 1	3070	#define EV_STANDALONE 1
2706	#include "ev.c"	3071	#include "ev.c"
2707		3072
2708	This will automatically include F<ev.h>, too, and should be done in a	3073	This will automatically include F<ev.h>, too, and should be done in a
2709	single C source file only to provide the function implementations. To use	3074	single C source file only to provide the function implementations. To use
2710	it, do the same for F<ev.h> in all files wishing to use this API (best	3075	it, do the same for F<ev.h> in all files wishing to use this API (best
2711	done by writing a wrapper around F<ev.h> that you can include instead and	3076	done by writing a wrapper around F<ev.h> that you can include instead and
2712	where you can put other configuration options):	3077	where you can put other configuration options):
2713		3078
2714	#define EV_STANDALONE 1	3079	#define EV_STANDALONE 1
2715	#include "ev.h"	3080	#include "ev.h"
2716		3081
2717	Both header files and implementation files can be compiled with a C++	3082	Both header files and implementation files can be compiled with a C++
2718	compiler (at least, thats a stated goal, and breakage will be treated	3083	compiler (at least, thats a stated goal, and breakage will be treated
2719	as a bug).	3084	as a bug).
2720		3085
2721	You need the following files in your source tree, or in a directory	3086	You need the following files in your source tree, or in a directory
2722	in your include path (e.g. in libev/ when using -Ilibev):	3087	in your include path (e.g. in libev/ when using -Ilibev):
2723		3088
2724	ev.h	3089	ev.h
2725	ev.c	3090	ev.c
2726	ev_vars.h	3091	ev_vars.h
2727	ev_wrap.h	3092	ev_wrap.h
2728		3093
2729	ev_win32.c required on win32 platforms only	3094	ev_win32.c required on win32 platforms only
2730		3095
2731	ev_select.c only when select backend is enabled (which is enabled by default)	3096	ev_select.c only when select backend is enabled (which is enabled by default)
2732	ev_poll.c only when poll backend is enabled (disabled by default)	3097	ev_poll.c only when poll backend is enabled (disabled by default)
2733	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3098	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2734	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3099	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2735	ev_port.c only when the solaris port backend is enabled (disabled by default)	3100	ev_port.c only when the solaris port backend is enabled (disabled by default)
2736		3101
2737	F<ev.c> includes the backend files directly when enabled, so you only need	3102	F<ev.c> includes the backend files directly when enabled, so you only need
2738	to compile this single file.	3103	to compile this single file.
2739		3104
2740	=head3 LIBEVENT COMPATIBILITY API	3105	=head3 LIBEVENT COMPATIBILITY API
2741		3106
2742	To include the libevent compatibility API, also include:	3107	To include the libevent compatibility API, also include:
2743		3108
2744	#include "event.c"	3109	#include "event.c"
2745		3110
2746	in the file including F<ev.c>, and:	3111	in the file including F<ev.c>, and:
2747		3112
2748	#include "event.h"	3113	#include "event.h"
2749		3114
2750	in the files that want to use the libevent API. This also includes F<ev.h>.	3115	in the files that want to use the libevent API. This also includes F<ev.h>.
2751		3116
2752	You need the following additional files for this:	3117	You need the following additional files for this:
2753		3118
2754	event.h	3119	event.h
2755	event.c	3120	event.c
2756		3121
2757	=head3 AUTOCONF SUPPORT	3122	=head3 AUTOCONF SUPPORT
2758		3123
2759	Instead of using C<EV_STANDALONE=1> and providing your config in	3124	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2760	whatever way you want, you can also C<m4_include([libev.m4])> in your	3125	whatever way you want, you can also C<m4_include([libev.m4])> in your
2761	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3126	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2762	include F<config.h> and configure itself accordingly.	3127	include F<config.h> and configure itself accordingly.
2763		3128
2764	For this of course you need the m4 file:	3129	For this of course you need the m4 file:
2765		3130
2766	libev.m4	3131	libev.m4
2767		3132
2768	=head2 PREPROCESSOR SYMBOLS/MACROS	3133	=head2 PREPROCESSOR SYMBOLS/MACROS
2769		3134
2770	Libev can be configured via a variety of preprocessor symbols you have to	3135	Libev can be configured via a variety of preprocessor symbols you have to
2771	define before including any of its files. The default in the absense of	3136	define before including any of its files. The default in the absence of
2772	autoconf is noted for every option.	3137	autoconf is documented for every option.
2773		3138
2774	=over 4	3139	=over 4
2775		3140
2776	=item EV_STANDALONE	3141	=item EV_STANDALONE
2777		3142
…		…
2782	F<event.h> that are not directly supported by the libev core alone.	3147	F<event.h> that are not directly supported by the libev core alone.
2783		3148
2784	=item EV_USE_MONOTONIC	3149	=item EV_USE_MONOTONIC
2785		3150
2786	If defined to be C<1>, libev will try to detect the availability of the	3151	If defined to be C<1>, libev will try to detect the availability of the
2787	monotonic clock option at both compiletime and runtime. Otherwise no use	3152	monotonic clock option at both compile time and runtime. Otherwise no use
2788	of the monotonic clock option will be attempted. If you enable this, you	3153	of the monotonic clock option will be attempted. If you enable this, you
2789	usually have to link against librt or something similar. Enabling it when	3154	usually have to link against librt or something similar. Enabling it when
2790	the functionality isn't available is safe, though, although you have	3155	the functionality isn't available is safe, though, although you have
2791	to make sure you link against any libraries where the C<clock_gettime>	3156	to make sure you link against any libraries where the C<clock_gettime>
2792	function is hiding in (often F<-lrt>).	3157	function is hiding in (often F<-lrt>).
2793		3158
2794	=item EV_USE_REALTIME	3159	=item EV_USE_REALTIME
2795		3160
2796	If defined to be C<1>, libev will try to detect the availability of the	3161	If defined to be C<1>, libev will try to detect the availability of the
2797	realtime clock option at compiletime (and assume its availability at	3162	real-time clock option at compile time (and assume its availability at
2798	runtime if successful). Otherwise no use of the realtime clock option will	3163	runtime if successful). Otherwise no use of the real-time clock option will
2799	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3164	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2800	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3165	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2801	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3166	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2802		3167
2803	=item EV_USE_NANOSLEEP	3168	=item EV_USE_NANOSLEEP
…		…
2814	2.7 or newer, otherwise disabled.	3179	2.7 or newer, otherwise disabled.
2815		3180
2816	=item EV_USE_SELECT	3181	=item EV_USE_SELECT
2817		3182
2818	If undefined or defined to be C<1>, libev will compile in support for the	3183	If undefined or defined to be C<1>, libev will compile in support for the
2819	C<select>(2) backend. No attempt at autodetection will be done: if no	3184	C<select>(2) backend. No attempt at auto-detection will be done: if no
2820	other method takes over, select will be it. Otherwise the select backend	3185	other method takes over, select will be it. Otherwise the select backend
2821	will not be compiled in.	3186	will not be compiled in.
2822		3187
2823	=item EV_SELECT_USE_FD_SET	3188	=item EV_SELECT_USE_FD_SET
2824		3189
2825	If defined to C<1>, then the select backend will use the system C<fd_set>	3190	If defined to C<1>, then the select backend will use the system C<fd_set>
2826	structure. This is useful if libev doesn't compile due to a missing	3191	structure. This is useful if libev doesn't compile due to a missing
2827	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3192	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2828	exotic systems. This usually limits the range of file descriptors to some	3193	exotic systems. This usually limits the range of file descriptors to some
2829	low limit such as 1024 or might have other limitations (winsocket only	3194	low limit such as 1024 or might have other limitations (winsocket only
2830	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3195	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2831	influence the size of the C<fd_set> used.	3196	influence the size of the C<fd_set> used.
2832		3197
…		…
2881	otherwise another method will be used as fallback. This is the preferred	3246	otherwise another method will be used as fallback. This is the preferred
2882	backend for Solaris 10 systems.	3247	backend for Solaris 10 systems.
2883		3248
2884	=item EV_USE_DEVPOLL	3249	=item EV_USE_DEVPOLL
2885		3250
2886	reserved for future expansion, works like the USE symbols above.	3251	Reserved for future expansion, works like the USE symbols above.
2887		3252
2888	=item EV_USE_INOTIFY	3253	=item EV_USE_INOTIFY
2889		3254
2890	If defined to be C<1>, libev will compile in support for the Linux inotify	3255	If defined to be C<1>, libev will compile in support for the Linux inotify
2891	interface to speed up C<ev_stat> watchers. Its actual availability will	3256	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2898	access is atomic with respect to other threads or signal contexts. No such	3263	access is atomic with respect to other threads or signal contexts. No such
2899	type is easily found in the C language, so you can provide your own type	3264	type is easily found in the C language, so you can provide your own type
2900	that you know is safe for your purposes. It is used both for signal handler "locking"	3265	that you know is safe for your purposes. It is used both for signal handler "locking"
2901	as well as for signal and thread safety in C<ev_async> watchers.	3266	as well as for signal and thread safety in C<ev_async> watchers.
2902		3267
2903	In the absense of this define, libev will use C<sig_atomic_t volatile>	3268	In the absence of this define, libev will use C<sig_atomic_t volatile>
2904	(from F<signal.h>), which is usually good enough on most platforms.	3269	(from F<signal.h>), which is usually good enough on most platforms.
2905		3270
2906	=item EV_H	3271	=item EV_H
2907		3272
2908	The name of the F<ev.h> header file used to include it. The default if	3273	The name of the F<ev.h> header file used to include it. The default if
…		…
2947	When doing priority-based operations, libev usually has to linearly search	3312	When doing priority-based operations, libev usually has to linearly search
2948	all the priorities, so having many of them (hundreds) uses a lot of space	3313	all the priorities, so having many of them (hundreds) uses a lot of space
2949	and time, so using the defaults of five priorities (-2 .. +2) is usually	3314	and time, so using the defaults of five priorities (-2 .. +2) is usually
2950	fine.	3315	fine.
2951		3316
2952	If your embedding app does not need any priorities, defining these both to	3317	If your embedding application does not need any priorities, defining these
2953	C<0> will save some memory and cpu.	3318	both to C<0> will save some memory and CPU.
2954		3319
2955	=item EV_PERIODIC_ENABLE	3320	=item EV_PERIODIC_ENABLE
2956		3321
2957	If undefined or defined to be C<1>, then periodic timers are supported. If	3322	If undefined or defined to be C<1>, then periodic timers are supported. If
2958	defined to be C<0>, then they are not. Disabling them saves a few kB of	3323	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2965	code.	3330	code.
2966		3331
2967	=item EV_EMBED_ENABLE	3332	=item EV_EMBED_ENABLE
2968		3333
2969	If undefined or defined to be C<1>, then embed watchers are supported. If	3334	If undefined or defined to be C<1>, then embed watchers are supported. If
2970	defined to be C<0>, then they are not.	3335	defined to be C<0>, then they are not. Embed watchers rely on most other
		3336	watcher types, which therefore must not be disabled.
2971		3337
2972	=item EV_STAT_ENABLE	3338	=item EV_STAT_ENABLE
2973		3339
2974	If undefined or defined to be C<1>, then stat watchers are supported. If	3340	If undefined or defined to be C<1>, then stat watchers are supported. If
2975	defined to be C<0>, then they are not.	3341	defined to be C<0>, then they are not.
…		…
2986		3352
2987	=item EV_MINIMAL	3353	=item EV_MINIMAL
2988		3354
2989	If you need to shave off some kilobytes of code at the expense of some	3355	If you need to shave off some kilobytes of code at the expense of some
2990	speed, define this symbol to C<1>. Currently this is used to override some	3356	speed, define this symbol to C<1>. Currently this is used to override some
2991	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3357	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2992	much smaller 2-heap for timer management over the default 4-heap.	3358	much smaller 2-heap for timer management over the default 4-heap.
2993		3359
2994	=item EV_PID_HASHSIZE	3360	=item EV_PID_HASHSIZE
2995		3361
2996	C<ev_child> watchers use a small hash table to distribute workload by	3362	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3007	two).	3373	two).
3008		3374
3009	=item EV_USE_4HEAP	3375	=item EV_USE_4HEAP
3010		3376
3011	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3377	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3012	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3378	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3013	to C<1>. The 4-heap uses more complicated (longer) code but has	3379	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3014	noticably faster performance with many (thousands) of watchers.	3380	faster performance with many (thousands) of watchers.
3015		3381
3016	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3382	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3017	(disabled).	3383	(disabled).
3018		3384
3019	=item EV_HEAP_CACHE_AT	3385	=item EV_HEAP_CACHE_AT
3020		3386
3021	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3387	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3022	timer and periodics heap, libev can cache the timestamp (I<at>) within	3388	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3023	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3389	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3024	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3390	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3025	but avoids random read accesses on heap changes. This improves performance	3391	but avoids random read accesses on heap changes. This improves performance
3026	noticably with with many (hundreds) of watchers.	3392	noticeably with many (hundreds) of watchers.
3027		3393
3028	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3394	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3029	(disabled).	3395	(disabled).
		3396
		3397	=item EV_VERIFY
		3398
		3399	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3400	be done: If set to C<0>, no internal verification code will be compiled
		3401	in. If set to C<1>, then verification code will be compiled in, but not
		3402	called. If set to C<2>, then the internal verification code will be
		3403	called once per loop, which can slow down libev. If set to C<3>, then the
		3404	verification code will be called very frequently, which will slow down
		3405	libev considerably.
		3406
		3407	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3408	C<0>.
3030		3409
3031	=item EV_COMMON	3410	=item EV_COMMON
3032		3411
3033	By default, all watchers have a C<void *data> member. By redefining	3412	By default, all watchers have a C<void *data> member. By redefining
3034	this macro to a something else you can include more and other types of	3413	this macro to a something else you can include more and other types of
3035	members. You have to define it each time you include one of the files,	3414	members. You have to define it each time you include one of the files,
3036	though, and it must be identical each time.	3415	though, and it must be identical each time.
3037		3416
3038	For example, the perl EV module uses something like this:	3417	For example, the perl EV module uses something like this:
3039		3418
3040	#define EV_COMMON \	3419	#define EV_COMMON \
3041	SV *self; /* contains this struct */ \	3420	SV *self; /* contains this struct */ \
3042	SV *cb_sv, *fh /* note no trailing ";" */	3421	SV *cb_sv, *fh /* note no trailing ";" */
3043		3422
3044	=item EV_CB_DECLARE (type)	3423	=item EV_CB_DECLARE (type)
3045		3424
3046	=item EV_CB_INVOKE (watcher, revents)	3425	=item EV_CB_INVOKE (watcher, revents)
3047		3426
…		…
3052	definition and a statement, respectively. See the F<ev.h> header file for	3431	definition and a statement, respectively. See the F<ev.h> header file for
3053	their default definitions. One possible use for overriding these is to	3432	their default definitions. One possible use for overriding these is to
3054	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3433	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3055	method calls instead of plain function calls in C++.	3434	method calls instead of plain function calls in C++.
3056		3435
		3436	=back
		3437
3057	=head2 EXPORTED API SYMBOLS	3438	=head2 EXPORTED API SYMBOLS
3058		3439
3059	If you need to re-export the API (e.g. via a dll) and you need a list of	3440	If you need to re-export the API (e.g. via a DLL) and you need a list of
3060	exported symbols, you can use the provided F<Symbol.*> files which list	3441	exported symbols, you can use the provided F<Symbol.*> files which list
3061	all public symbols, one per line:	3442	all public symbols, one per line:
3062		3443
3063	Symbols.ev for libev proper	3444	Symbols.ev for libev proper
3064	Symbols.event for the libevent emulation	3445	Symbols.event for the libevent emulation
3065		3446
3066	This can also be used to rename all public symbols to avoid clashes with	3447	This can also be used to rename all public symbols to avoid clashes with
3067	multiple versions of libev linked together (which is obviously bad in	3448	multiple versions of libev linked together (which is obviously bad in
3068	itself, but sometimes it is inconvinient to avoid this).	3449	itself, but sometimes it is inconvenient to avoid this).
3069		3450
3070	A sed command like this will create wrapper C<#define>'s that you need to	3451	A sed command like this will create wrapper C<#define>'s that you need to
3071	include before including F<ev.h>:	3452	include before including F<ev.h>:
3072		3453
3073	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3454	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3090	file.	3471	file.
3091		3472
3092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3473	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3093	that everybody includes and which overrides some configure choices:	3474	that everybody includes and which overrides some configure choices:
3094		3475
3095	#define EV_MINIMAL 1	3476	#define EV_MINIMAL 1
3096	#define EV_USE_POLL 0	3477	#define EV_USE_POLL 0
3097	#define EV_MULTIPLICITY 0	3478	#define EV_MULTIPLICITY 0
3098	#define EV_PERIODIC_ENABLE 0	3479	#define EV_PERIODIC_ENABLE 0
3099	#define EV_STAT_ENABLE 0	3480	#define EV_STAT_ENABLE 0
3100	#define EV_FORK_ENABLE 0	3481	#define EV_FORK_ENABLE 0
3101	#define EV_CONFIG_H <config.h>	3482	#define EV_CONFIG_H <config.h>
3102	#define EV_MINPRI 0	3483	#define EV_MINPRI 0
3103	#define EV_MAXPRI 0	3484	#define EV_MAXPRI 0
3104		3485
3105	#include "ev++.h"	3486	#include "ev++.h"
3106		3487
3107	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3488	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3108		3489
3109	#include "ev_cpp.h"	3490	#include "ev_cpp.h"
3110	#include "ev.c"	3491	#include "ev.c"
3111		3492
		3493	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3112		3494
3113	=head1 THREADS AND COROUTINES	3495	=head2 THREADS AND COROUTINES
3114		3496
3115	=head2 THREADS	3497	=head3 THREADS
3116		3498
3117	Libev itself is completely threadsafe, but it uses no locking. This	3499	All libev functions are reentrant and thread-safe unless explicitly
		3500	documented otherwise, but libev implements no locking itself. This means
3118	means that you can use as many loops as you want in parallel, as long as	3501	that you can use as many loops as you want in parallel, as long as there
3119	only one thread ever calls into one libev function with the same loop	3502	are no concurrent calls into any libev function with the same loop
3120	parameter.	3503	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3504	of course): libev guarantees that different event loops share no data
		3505	structures that need any locking.
3121		3506
3122	Or put differently: calls with different loop parameters can be done in	3507	Or to put it differently: calls with different loop parameters can be done
3123	parallel from multiple threads, calls with the same loop parameter must be	3508	concurrently from multiple threads, calls with the same loop parameter
3124	done serially (but can be done from different threads, as long as only one	3509	must be done serially (but can be done from different threads, as long as
3125	thread ever is inside a call at any point in time, e.g. by using a mutex	3510	only one thread ever is inside a call at any point in time, e.g. by using
3126	per loop).	3511	a mutex per loop).
3127		3512
3128	If you want to know which design is best for your problem, then I cannot	3513	Specifically to support threads (and signal handlers), libev implements
		3514	so-called C<ev_async> watchers, which allow some limited form of
		3515	concurrency on the same event loop, namely waking it up "from the
		3516	outside".
		3517
		3518	If you want to know which design (one loop, locking, or multiple loops
		3519	without or something else still) is best for your problem, then I cannot
3129	help you but by giving some generic advice:	3520	help you, but here is some generic advice:
3130		3521
3131	=over 4	3522	=over 4
3132		3523
3133	=item * most applications have a main thread: use the default libev loop	3524	=item * most applications have a main thread: use the default libev loop
3134	in that thread, or create a seperate thread running only the default loop.	3525	in that thread, or create a separate thread running only the default loop.
3135		3526
3136	This helps integrating other libraries or software modules that use libev	3527	This helps integrating other libraries or software modules that use libev
3137	themselves and don't care/know about threading.	3528	themselves and don't care/know about threading.
3138		3529
3139	=item * one loop per thread is usually a good model.	3530	=item * one loop per thread is usually a good model.
3140		3531
3141	Doing this is almost never wrong, sometimes a better-performance model	3532	Doing this is almost never wrong, sometimes a better-performance model
3142	exists, but it is always a good start.	3533	exists, but it is always a good start.
3143		3534
3144	=item * other models exist, such as the leader/follower pattern, where one	3535	=item * other models exist, such as the leader/follower pattern, where one
3145	loop is handed through multiple threads in a kind of round-robbin fashion.	3536	loop is handed through multiple threads in a kind of round-robin fashion.
3146		3537
3147	Chosing a model is hard - look around, learn, know that usually you cna do	3538	Choosing a model is hard - look around, learn, know that usually you can do
3148	better than you currently do :-)	3539	better than you currently do :-)
3149		3540
3150	=item * often you need to talk to some other thread which blocks in the	3541	=item * often you need to talk to some other thread which blocks in the
		3542	event loop.
		3543
3151	event loop - C<ev_async> watchers can be used to wake them up from other	3544	C<ev_async> watchers can be used to wake them up from other threads safely
3152	threads safely (or from signal contexts...).	3545	(or from signal contexts...).
		3546
		3547	An example use would be to communicate signals or other events that only
		3548	work in the default loop by registering the signal watcher with the
		3549	default loop and triggering an C<ev_async> watcher from the default loop
		3550	watcher callback into the event loop interested in the signal.
3153		3551
3154	=back	3552	=back
3155		3553
3156	=head2 COROUTINES	3554	=head3 COROUTINES
3157		3555
3158	Libev is much more accomodating to coroutines ("cooperative threads"):	3556	Libev is very accommodating to coroutines ("cooperative threads"):
3159	libev fully supports nesting calls to it's functions from different	3557	libev fully supports nesting calls to its functions from different
3160	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3558	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3161	different coroutines and switch freely between both coroutines running the	3559	different coroutines, and switch freely between both coroutines running the
3162	loop, as long as you don't confuse yourself). The only exception is that	3560	loop, as long as you don't confuse yourself). The only exception is that
3163	you must not do this from C<ev_periodic> reschedule callbacks.	3561	you must not do this from C<ev_periodic> reschedule callbacks.
3164		3562
3165	Care has been invested into making sure that libev does not keep local	3563	Care has been taken to ensure that libev does not keep local state inside
3166	state inside C<ev_loop>, and other calls do not usually allow coroutine	3564	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3167	switches.	3565	they do not clal any callbacks.
3168		3566
		3567	=head2 COMPILER WARNINGS
3169		3568
3170	=head1 COMPLEXITIES	3569	Depending on your compiler and compiler settings, you might get no or a
		3570	lot of warnings when compiling libev code. Some people are apparently
		3571	scared by this.
3171		3572
3172	In this section the complexities of (many of) the algorithms used inside	3573	However, these are unavoidable for many reasons. For one, each compiler
3173	libev will be explained. For complexity discussions about backends see the	3574	has different warnings, and each user has different tastes regarding
3174	documentation for C<ev_default_init>.	3575	warning options. "Warn-free" code therefore cannot be a goal except when
		3576	targeting a specific compiler and compiler-version.
3175		3577
3176	All of the following are about amortised time: If an array needs to be	3578	Another reason is that some compiler warnings require elaborate
3177	extended, libev needs to realloc and move the whole array, but this	3579	workarounds, or other changes to the code that make it less clear and less
3178	happens asymptotically never with higher number of elements, so O(1) might	3580	maintainable.
3179	mean it might do a lengthy realloc operation in rare cases, but on average
3180	it is much faster and asymptotically approaches constant time.
3181		3581
3182	=over 4	3582	And of course, some compiler warnings are just plain stupid, or simply
		3583	wrong (because they don't actually warn about the condition their message
		3584	seems to warn about). For example, certain older gcc versions had some
		3585	warnings that resulted an extreme number of false positives. These have
		3586	been fixed, but some people still insist on making code warn-free with
		3587	such buggy versions.
3183		3588
3184	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3589	While libev is written to generate as few warnings as possible,
		3590	"warn-free" code is not a goal, and it is recommended not to build libev
		3591	with any compiler warnings enabled unless you are prepared to cope with
		3592	them (e.g. by ignoring them). Remember that warnings are just that:
		3593	warnings, not errors, or proof of bugs.
3185		3594
3186	This means that, when you have a watcher that triggers in one hour and
3187	there are 100 watchers that would trigger before that then inserting will
3188	have to skip roughly seven (C<ld 100>) of these watchers.
3189		3595
3190	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3596	=head2 VALGRIND
3191		3597
3192	That means that changing a timer costs less than removing/adding them	3598	Valgrind has a special section here because it is a popular tool that is
3193	as only the relative motion in the event queue has to be paid for.	3599	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3194		3600
3195	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3601	If you think you found a bug (memory leak, uninitialised data access etc.)
		3602	in libev, then check twice: If valgrind reports something like:
3196		3603
3197	These just add the watcher into an array or at the head of a list.	3604	==2274== definitely lost: 0 bytes in 0 blocks.
		3605	==2274== possibly lost: 0 bytes in 0 blocks.
		3606	==2274== still reachable: 256 bytes in 1 blocks.
3198		3607
3199	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3608	Then there is no memory leak, just as memory accounted to global variables
		3609	is not a memleak - the memory is still being refernced, and didn't leak.
3200		3610
3201	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3611	Similarly, under some circumstances, valgrind might report kernel bugs
		3612	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3613	although an acceptable workaround has been found here), or it might be
		3614	confused.
3202		3615
3203	These watchers are stored in lists then need to be walked to find the	3616	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3204	correct watcher to remove. The lists are usually short (you don't usually	3617	make it into some kind of religion.
3205	have many watchers waiting for the same fd or signal).
3206		3618
3207	=item Finding the next timer in each loop iteration: O(1)	3619	If you are unsure about something, feel free to contact the mailing list
		3620	with the full valgrind report and an explanation on why you think this
		3621	is a bug in libev (best check the archives, too :). However, don't be
		3622	annoyed when you get a brisk "this is no bug" answer and take the chance
		3623	of learning how to interpret valgrind properly.
3208		3624
3209	By virtue of using a binary or 4-heap, the next timer is always found at a	3625	If you need, for some reason, empty reports from valgrind for your project
3210	fixed position in the storage array.	3626	I suggest using suppression lists.
3211		3627
3212	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3213		3628
3214	A change means an I/O watcher gets started or stopped, which requires	3629	=head1 PORTABILITY NOTES
3215	libev to recalculate its status (and possibly tell the kernel, depending
3216	on backend and wether C<ev_io_set> was used).
3217		3630
3218	=item Activating one watcher (putting it into the pending state): O(1)	3631	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3219
3220	=item Priority handling: O(number_of_priorities)
3221
3222	Priorities are implemented by allocating some space for each
3223	priority. When doing priority-based operations, libev usually has to
3224	linearly search all the priorities, but starting/stopping and activating
3225	watchers becomes O(1) w.r.t. priority handling.
3226
3227	=item Sending an ev_async: O(1)
3228
3229	=item Processing ev_async_send: O(number_of_async_watchers)
3230
3231	=item Processing signals: O(max_signal_number)
3232
3233	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3234	calls in the current loop iteration. Checking for async and signal events
3235	involves iterating over all running async watchers or all signal numbers.
3236
3237	=back
3238
3239
3240	=head1 Win32 platform limitations and workarounds
3241		3632
3242	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3633	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3243	requires, and its I/O model is fundamentally incompatible with the POSIX	3634	requires, and its I/O model is fundamentally incompatible with the POSIX
3244	model. Libev still offers limited functionality on this platform in	3635	model. Libev still offers limited functionality on this platform in
3245	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3636	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3252	way (note also that glib is the slowest event library known to man).	3643	way (note also that glib is the slowest event library known to man).
3253		3644
3254	There is no supported compilation method available on windows except	3645	There is no supported compilation method available on windows except
3255	embedding it into other applications.	3646	embedding it into other applications.
3256		3647
		3648	Not a libev limitation but worth mentioning: windows apparently doesn't
		3649	accept large writes: instead of resulting in a partial write, windows will
		3650	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3651	so make sure you only write small amounts into your sockets (less than a
		3652	megabyte seems safe, but this apparently depends on the amount of memory
		3653	available).
		3654
3257	Due to the many, low, and arbitrary limits on the win32 platform and	3655	Due to the many, low, and arbitrary limits on the win32 platform and
3258	the abysmal performance of winsockets, using a large number of sockets	3656	the abysmal performance of winsockets, using a large number of sockets
3259	is not recommended (and not reasonable). If your program needs to use	3657	is not recommended (and not reasonable). If your program needs to use
3260	more than a hundred or so sockets, then likely it needs to use a totally	3658	more than a hundred or so sockets, then likely it needs to use a totally
3261	different implementation for windows, as libev offers the POSIX readiness	3659	different implementation for windows, as libev offers the POSIX readiness
3262	notification model, which cannot be implemented efficiently on windows	3660	notification model, which cannot be implemented efficiently on windows
3263	(microsoft monopoly games).	3661	(Microsoft monopoly games).
		3662
		3663	A typical way to use libev under windows is to embed it (see the embedding
		3664	section for details) and use the following F<evwrap.h> header file instead
		3665	of F<ev.h>:
		3666
		3667	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3668	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3669
		3670	#include "ev.h"
		3671
		3672	And compile the following F<evwrap.c> file into your project (make sure
		3673	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3674
		3675	#include "evwrap.h"
		3676	#include "ev.c"
3264		3677
3265	=over 4	3678	=over 4
3266		3679
3267	=item The winsocket select function	3680	=item The winsocket select function
3268		3681
3269	The winsocket C<select> function doesn't follow POSIX in that it requires	3682	The winsocket C<select> function doesn't follow POSIX in that it
3270	socket I<handles> and not socket I<file descriptors>. This makes select	3683	requires socket I<handles> and not socket I<file descriptors> (it is
3271	very inefficient, and also requires a mapping from file descriptors	3684	also extremely buggy). This makes select very inefficient, and also
3272	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3685	requires a mapping from file descriptors to socket handles (the Microsoft
3273	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3686	C runtime provides the function C<_open_osfhandle> for this). See the
3274	symbols for more info.	3687	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3688	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3275		3689
3276	The configuration for a "naked" win32 using the microsoft runtime	3690	The configuration for a "naked" win32 using the Microsoft runtime
3277	libraries and raw winsocket select is:	3691	libraries and raw winsocket select is:
3278		3692
3279	#define EV_USE_SELECT 1	3693	#define EV_USE_SELECT 1
3280	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3694	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3281		3695
3282	Note that winsockets handling of fd sets is O(n), so you can easily get a	3696	Note that winsockets handling of fd sets is O(n), so you can easily get a
3283	complexity in the O(n²) range when using win32.	3697	complexity in the O(n²) range when using win32.
3284		3698
3285	=item Limited number of file descriptors	3699	=item Limited number of file descriptors
3286		3700
3287	Windows has numerous arbitrary (and low) limits on things.	3701	Windows has numerous arbitrary (and low) limits on things.
3288		3702
3289	Early versions of winsocket's select only supported waiting for a maximum	3703	Early versions of winsocket's select only supported waiting for a maximum
3290	of C<64> handles (probably owning to the fact that all windows kernels	3704	of C<64> handles (probably owning to the fact that all windows kernels
3291	can only wait for C<64> things at the same time internally; microsoft	3705	can only wait for C<64> things at the same time internally; Microsoft
3292	recommends spawning a chain of threads and wait for 63 handles and the	3706	recommends spawning a chain of threads and wait for 63 handles and the
3293	previous thread in each. Great).	3707	previous thread in each. Great).
3294		3708
3295	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3709	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3296	to some high number (e.g. C<2048>) before compiling the winsocket select	3710	to some high number (e.g. C<2048>) before compiling the winsocket select
3297	call (which might be in libev or elsewhere, for example, perl does its own	3711	call (which might be in libev or elsewhere, for example, perl does its own
3298	select emulation on windows).	3712	select emulation on windows).
3299		3713
3300	Another limit is the number of file descriptors in the microsoft runtime	3714	Another limit is the number of file descriptors in the Microsoft runtime
3301	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3715	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3302	or something like this inside microsoft). You can increase this by calling	3716	or something like this inside Microsoft). You can increase this by calling
3303	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3717	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3304	arbitrary limit), but is broken in many versions of the microsoft runtime	3718	arbitrary limit), but is broken in many versions of the Microsoft runtime
3305	libraries.	3719	libraries.
3306		3720
3307	This might get you to about C<512> or C<2048> sockets (depending on	3721	This might get you to about C<512> or C<2048> sockets (depending on
3308	windows version and/or the phase of the moon). To get more, you need to	3722	windows version and/or the phase of the moon). To get more, you need to
3309	wrap all I/O functions and provide your own fd management, but the cost of	3723	wrap all I/O functions and provide your own fd management, but the cost of
3310	calling select (O(n²)) will likely make this unworkable.	3724	calling select (O(n²)) will likely make this unworkable.
3311		3725
3312	=back	3726	=back
3313		3727
3314
3315	=head1 PORTABILITY REQUIREMENTS	3728	=head2 PORTABILITY REQUIREMENTS
3316		3729
3317	In addition to a working ISO-C implementation, libev relies on a few	3730	In addition to a working ISO-C implementation and of course the
3318	additional extensions:	3731	backend-specific APIs, libev relies on a few additional extensions:
3319		3732
3320	=over 4	3733	=over 4
3321		3734
		3735	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3736	calling conventions regardless of C<ev_watcher_type *>.
		3737
		3738	Libev assumes not only that all watcher pointers have the same internal
		3739	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3740	assumes that the same (machine) code can be used to call any watcher
		3741	callback: The watcher callbacks have different type signatures, but libev
		3742	calls them using an C<ev_watcher *> internally.
		3743
3322	=item C<sig_atomic_t volatile> must be thread-atomic as well	3744	=item C<sig_atomic_t volatile> must be thread-atomic as well
3323		3745
3324	The type C<sig_atomic_t volatile> (or whatever is defined as	3746	The type C<sig_atomic_t volatile> (or whatever is defined as
3325	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3747	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3326	threads. This is not part of the specification for C<sig_atomic_t>, but is	3748	threads. This is not part of the specification for C<sig_atomic_t>, but is
3327	believed to be sufficiently portable.	3749	believed to be sufficiently portable.
3328		3750
3329	=item C<sigprocmask> must work in a threaded environment	3751	=item C<sigprocmask> must work in a threaded environment
3330		3752
…		…
3339	except the initial one, and run the default loop in the initial thread as	3761	except the initial one, and run the default loop in the initial thread as
3340	well.	3762	well.
3341		3763
3342	=item C<long> must be large enough for common memory allocation sizes	3764	=item C<long> must be large enough for common memory allocation sizes
3343		3765
3344	To improve portability and simplify using libev, libev uses C<long>	3766	To improve portability and simplify its API, libev uses C<long> internally
3345	internally instead of C<size_t> when allocating its data structures. On	3767	instead of C<size_t> when allocating its data structures. On non-POSIX
3346	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3768	systems (Microsoft...) this might be unexpectedly low, but is still at
3347	is still at least 31 bits everywhere, which is enough for hundreds of	3769	least 31 bits everywhere, which is enough for hundreds of millions of
3348	millions of watchers.	3770	watchers.
3349		3771
3350	=item C<double> must hold a time value in seconds with enough accuracy	3772	=item C<double> must hold a time value in seconds with enough accuracy
3351		3773
3352	The type C<double> is used to represent timestamps. It is required to	3774	The type C<double> is used to represent timestamps. It is required to
3353	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3775	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3357	=back	3779	=back
3358		3780
3359	If you know of other additional requirements drop me a note.	3781	If you know of other additional requirements drop me a note.
3360		3782
3361		3783
3362	=head1 VALGRIND	3784	=head1 ALGORITHMIC COMPLEXITIES
3363		3785
3364	Valgrind has a special section here because it is a popular tool that is	3786	In this section the complexities of (many of) the algorithms used inside
3365	highly useful, but valgrind reports are very hard to interpret.	3787	libev will be documented. For complexity discussions about backends see
		3788	the documentation for C<ev_default_init>.
3366		3789
3367	If you think you found a bug (memory leak, uninitialised data access etc.)	3790	All of the following are about amortised time: If an array needs to be
3368	in libev, then check twice: If valgrind reports something like:	3791	extended, libev needs to realloc and move the whole array, but this
		3792	happens asymptotically rarer with higher number of elements, so O(1) might
		3793	mean that libev does a lengthy realloc operation in rare cases, but on
		3794	average it is much faster and asymptotically approaches constant time.
3369		3795
3370	==2274== definitely lost: 0 bytes in 0 blocks.	3796	=over 4
3371	==2274== possibly lost: 0 bytes in 0 blocks.
3372	==2274== still reachable: 256 bytes in 1 blocks.
3373		3797
3374	then there is no memory leak. Similarly, under some circumstances,	3798	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3375	valgrind might report kernel bugs as if it were a bug in libev, or it
3376	might be confused (it is a very good tool, but only a tool).
3377		3799
3378	If you are unsure about something, feel free to contact the mailing list	3800	This means that, when you have a watcher that triggers in one hour and
3379	with the full valgrind report and an explanation on why you think this is	3801	there are 100 watchers that would trigger before that, then inserting will
3380	a bug in libev. However, don't be annoyed when you get a brisk "this is	3802	have to skip roughly seven (C<ld 100>) of these watchers.
3381	no bug" answer and take the chance of learning how to interpret valgrind
3382	properly.
3383		3803
3384	If you need, for some reason, empty reports from valgrind for your project	3804	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3385	I suggest using suppression lists.	3805
		3806	That means that changing a timer costs less than removing/adding them,
		3807	as only the relative motion in the event queue has to be paid for.
		3808
		3809	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3810
		3811	These just add the watcher into an array or at the head of a list.
		3812
		3813	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3814
		3815	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3816
		3817	These watchers are stored in lists, so they need to be walked to find the
		3818	correct watcher to remove. The lists are usually short (you don't usually
		3819	have many watchers waiting for the same fd or signal: one is typical, two
		3820	is rare).
		3821
		3822	=item Finding the next timer in each loop iteration: O(1)
		3823
		3824	By virtue of using a binary or 4-heap, the next timer is always found at a
		3825	fixed position in the storage array.
		3826
		3827	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3828
		3829	A change means an I/O watcher gets started or stopped, which requires
		3830	libev to recalculate its status (and possibly tell the kernel, depending
		3831	on backend and whether C<ev_io_set> was used).
		3832
		3833	=item Activating one watcher (putting it into the pending state): O(1)
		3834
		3835	=item Priority handling: O(number_of_priorities)
		3836
		3837	Priorities are implemented by allocating some space for each
		3838	priority. When doing priority-based operations, libev usually has to
		3839	linearly search all the priorities, but starting/stopping and activating
		3840	watchers becomes O(1) with respect to priority handling.
		3841
		3842	=item Sending an ev_async: O(1)
		3843
		3844	=item Processing ev_async_send: O(number_of_async_watchers)
		3845
		3846	=item Processing signals: O(max_signal_number)
		3847
		3848	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3849	calls in the current loop iteration. Checking for async and signal events
		3850	involves iterating over all running async watchers or all signal numbers.
		3851
		3852	=back
3386		3853
3387		3854
3388	=head1 AUTHOR	3855	=head1 AUTHOR
3389		3856
3390	Marc Lehmann <libev@schmorp.de>.	3857	Marc Lehmann <libev@schmorp.de>.

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