ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.154 by root, Sun May 11 11:47:27 2008 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 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_ struct 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_ struct 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	struct 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
…		…
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.
…		…
277	from multiple threads, you have to lock (note also that this is unlikely,	298	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	299	as loops cannot bes hared easily between threads anyway).
279		300
280	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	306	C<ev_default_init>.
286		307
287	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	318	thing, believe me).
298		319
299	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
300		321
301	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
306	around bugs.	327	around bugs.
…		…
313		334
314	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
320		341
321	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
323	flag.	344	flag.
324		345
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	347	environment variable.
327		348
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		350
330	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
335		356
336	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
342		367
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		369
345	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	371	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	372	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,	373	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	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	375	performance tips.
351		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		381
354	For few fds, this backend is a bit little slower than poll and select,	382	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	383	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),	384	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	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and requiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	388	support for dup.
361		389
362	While stopping, setting and starting an I/O watcher in the same iteration	390	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	391	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	392	(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	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	394	very well if you register events for both fds.
367		395
368	Please note that epoll sometimes generates spurious notifications, so you	396	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	397	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.	398	(or space) is available.
371		399
372	Best performance from this backend is achieved by not unregistering all	400	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.	401	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
375		405
376	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	407	all kernel versions tested so far.
378		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		413
381	Kqueue deserves special mention, as at the time of this writing, it	414	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	415	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	416	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"	417	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	418	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)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		420
389	You still can embed kqueue into a normal poll or select backend and use it	421	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	422	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.	423	the target platform). See C<ev_embed> watchers for more info.
392		424
393	It scales in the same way as the epoll backend, but the interface to the	425	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	426	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	427	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	428	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	429	two event changes per incident. Support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
399		431
400	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
401		433
402	While nominally embeddable in other event loops, this doesn't work	434	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	435	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	436	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	437	(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	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
408		444
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		446
411	This is not implemented yet (and might never be, unless you send me an	447	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	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		453
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	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)).	455	it's really slow, but it still scales very well (O(active_fds)).
420		456
421	Please note that solaris event ports can deliver a lot of spurious	457	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	458	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
424		460
425	While this backend scales well, it requires one system call per active	461	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	462	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	464	might perform better.
429		465
430	On the positive side, ignoring the spurious readyness notifications, this	466	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
433		473
434	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
435		475
436	Try all backends (even potentially broken ones that wouldn't be tried	476	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	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		479
440	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
441		481
442	=back	482	=back
443		483
444	If one or more of these are ored into the flags value, then only these	484	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	485	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.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		487
448	The most typical usage is like this:	488	Example: This is the most typical usage.
449		489
450	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		492
453	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	494	environment settings to be taken into account:
455		495
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		497
458	Use whatever libev has to offer, but make sure that kqueue is used if	498	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	499	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):	500	private event loop and only if you know the OS supports your types of
		501	fds):
461		502
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		504
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		506
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	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	508	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	513	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	514	default loop in the "main" or "initial" thread.
474		515
475	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
476		517
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	519	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
480		521
481	=item ev_default_destroy ()	522	=item ev_default_destroy ()
482		523
483	Destroys the default loop again (frees all memory and kernel state	524	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	525	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	526	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>	527	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	528	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	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	530	for example).
490		531
491	Note that certain global state, such as signal state, will not be freed by	532	Note that certain global state, such as signal state, will not be freed by
…		…
523		564
524	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
525		566
526	Like C<ev_default_fork>, but acts on an event loop created by	567	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	568	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.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
529		571
530	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
531		573
532	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
533		576
534	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
535		578
536	Returns the count of loop iterations for the loop, which is identical to	579	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	580	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	595	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	596	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	597	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).	598	event occurring (or more correctly, libev finding out about it).
556		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
557	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
558		613
559	Finally, this is it, the event handler. This function usually is called	614	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	615	after you initialised all your watchers and you want to start handling
561	events.	616	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	618	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.	619	either no event watchers are active anymore or C<ev_unloop> was called.
565		620
566	Please note that an explicit C<ev_unloop> is usually better than	621	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	622	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	624	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.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
571		627
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	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	629	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.	630	process in case there are no events and will return after one iteration of
		631	the loop.
575		632
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	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	634	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	635	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	636	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	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	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	642	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.	643	usually a better approach for this kind of thing.
583		644
584	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
585		646
586	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	662	- Queue all expired timers.
601	- Queue all outstanding periodics.	663	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	665	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- 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	667	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	674	anymore.
613		675
614	... queue jobs here, make sure they register event watchers as long	676	... 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..)	677	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
617	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
618		680
619	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
620		682
621	Can be used to make a call to C<ev_loop> return early (but only after it	683	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	684	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	685	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.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		687
626	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
627		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
628	=item ev_ref (loop)	692	=item ev_ref (loop)
629		693
630	=item ev_unref (loop)	694	=item ev_unref (loop)
631		695
632	Ref/unref can be used to add or remove a reference count on the event	696	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	697	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	698	count is nonzero, C<ev_loop> will not return on its own.
		699
635	a watcher you never unregister that should not keep C<ev_loop> from	700	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	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
637	example, libev itself uses this for its internal signal pipe: It is not	704	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	705	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	706	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	707	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>	708	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,	709	(but only if the watcher wasn't active before, or was active before,
643	respectively).	710	respectively).
644		711
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	713	running when nothing else is active.
647		714
648	struct ev_signal exitsig;	715	struct ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	718	evf_unref (loop);
652		719
653	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
654		721
655	ev_ref (loop);	722	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
657		724
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		726
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		728
662	These advanced functions influence the time that libev will spend waiting	729	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	730	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.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
665		733
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	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	735	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
669		738
670	The background is that sometimes your program runs just fast enough to	739	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	740	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	741	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	742	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
675		744
676	By setting a higher I<io collect interval> you allow libev to spend more	745	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,	746	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	748	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.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		750
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	755	value will not introduce any overhead in libev.
687		756
688	Many (busy) programs can usually benefit by setting the io collect	757	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	758	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	759	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>,	760	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.	761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
693		781
694	=back	782	=back
695		783
696		784
697	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
698		786
699	A watcher is a structure that you create and register to record your	787	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	788	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:	789	become readable, you would create an C<ev_io> watcher for that:
702		790
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
704	{	792	{
705	ev_io_stop (w);	793	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
707	}	795	}
708		796
709	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
710	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
711	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
714	ev_loop (loop, 0);	802	ev_loop (loop, 0);
715		803
716	As you can see, you are responsible for allocating the memory for your	804	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,	805	watcher structures (and it is usually a bad idea to do this on the stack,
718	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
719		807
720	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	809	(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	810	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	811	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	812	is readable and/or writable).
725		813
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
727	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
803		891
804	The given async watcher has been asynchronously notified (see C<ev_async>).	892	The given async watcher has been asynchronously notified (see C<ev_async>).
805		893
806	=item C<EV_ERROR>	894	=item C<EV_ERROR>
807		895
808	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	897	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	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
811	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
813		905
814	Libev will usually signal a few "dummy" events together with an error,	906	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	907	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	908	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	909	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
819		912
820	=back	913	=back
821		914
822	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
823		916
…		…
839	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
840		933
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	935	int revents)>.
843		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
		942
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		944
846	This macro initialises the type-specific parts of a watcher. You need to	945	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	946	call C<ev_init> at least once before you call this macro, but you can
848	call C<ev_TYPE_set> any number of times. You must not, however, call this	947	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
850	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
851		950
852	Although some watcher types do not have type-specific arguments	951	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.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		953
		954	See C<ev_init>, above, for an example.
		955
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		957
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	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	959	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		965
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		967
863	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
865		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		977
868	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
869	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	982	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	983	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	984	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.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		986
875	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
876		988
877	Returns a true value iff the watcher is active (i.e. it has been started	989	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	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926		1038
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1040
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	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	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
932		1045
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1047
935	If the watcher is pending, this function returns clears its pending status	1048	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	1049	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>.	1050	watcher isn't pending it does nothing and returns C<0>.
938		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
939	=back	1055	=back
940		1056
941		1057
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1059
944	Each watcher has, by default, a member C<void *data> that you can change	1060	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	1061	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	1062	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	1063	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	1064	member, you can also "subclass" the watcher type and provide your own
949	data:	1065	data:
950		1066
951	struct my_io	1067	struct my_io
952	{	1068	{
953	struct ev_io io;	1069	struct ev_io io;
954	int otherfd;	1070	int otherfd;
955	void *somedata;	1071	void *somedata;
956	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
957	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1078
959	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1080	can cast it back to your own type:
961		1081
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
963	{	1083	{
964	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
965	...	1085	...
966	}	1086	}
967		1087
968	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1089	instead have been omitted.
970		1090
971	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
972	watchers:	1092	embedded watchers:
973		1093
974	struct my_biggy	1094	struct my_biggy
975	{	1095	{
976	int some_data;	1096	int some_data;
977	ev_timer t1;	1097	ev_timer t1;
978	ev_timer t2;	1098	ev_timer t2;
979	}	1099	}
980		1100
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
983		1106
984	#include <stddef.h>	1107	#include <stddef.h>
985		1108
986	static void	1109	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ struct ev_timer *w, int revents)
988	{	1111	{
989	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1114	}
992		1115
993	static void	1116	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ struct ev_timer *w, int revents)
995	{	1118	{
996	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1121	}
999		1122
1000		1123
1001	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
1002		1125
1003	This section describes each watcher in detail, but will not repeat	1126	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	1150	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	1151	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	1152	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1153	required if you know what you are doing).
1031		1154
1032	If you must do this, then force the use of a known-to-be-good backend	1155	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	1156	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1158
1036	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1160	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	1161	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	1162	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	1163	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	1164	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	1165	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.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1167
1045	If you cannot run the fd in non-blocking mode (for example you should not	1168	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	1169	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	1170	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	1171	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
1050		1177
1051	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1052		1179
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1180	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,	1181	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	1182	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	1183	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	1184	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	1185	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1186	fact, a different file descriptor.
1060		1187
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1093		1220
1094	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1095		1222
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1223	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	1224	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	1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1227
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1228	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	1229	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).	1230	somewhere, as that would have given you a big clue).
1105		1231
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1238
1113	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1114		1240
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	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	1242	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.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1244
1119	=item int fd [read-only]	1245	=item int fd [read-only]
1120		1246
1121	The file descriptor being watched.	1247	The file descriptor being watched.
1122		1248
…		…
1130		1256
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	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	1258	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1134		1260
1135	static void	1261	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1137	{	1263	{
1138	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1266	}
1141		1267
1142	...	1268	...
1143	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1270	struct ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1148		1274
1149		1275
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1277
1152	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1154		1280
1155	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1282	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 The special problem of time updates
		1292
		1293	Establishing the current time is a costly operation (it usually takes at
		1294	least two system calls): EV therefore updates its idea of the current
		1295	time only before and after C<ev_loop> collects new events, which causes a
		1296	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1297	lots of events in one iteration.
1160		1298
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1299	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	1300	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	1301	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	1302	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:	1303	timeout on the current time, use something like this to adjust for this:
1166		1304
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1305	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1306
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1307	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	1308	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1309	()>.
1172		1310
1173	=head3 Watcher-Specific Functions and Data Members	1311	=head3 Watcher-Specific Functions and Data Members
1174		1312
1175	=over 4	1313	=over 4
1176		1314
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1315	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1316
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1317	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1318
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1319	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1320	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1321	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1322	configured to trigger again C<repeat> seconds later, again, and again,
		1323	until stopped manually.
1185		1324
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1325	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1326	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1327	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1328	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1329	do stuff) the timer will not fire more than once per event loop iteration.
1191		1330
1192	=item ev_timer_again (loop, ev_timer *)	1331	=item ev_timer_again (loop, ev_timer *)
1193		1332
1194	This will act as if the timer timed out and restart it again if it is	1333	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1334	repeating. The exact semantics are:
1196		1335
1197	If the timer is pending, its pending status is cleared.	1336	If the timer is pending, its pending status is cleared.
1198		1337
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1338	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1339
1201	If the timer is repeating, either start it if necessary (with the	1340	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	1341	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1342
1204	This sounds a bit complicated, but here is a useful and typical	1343	This sounds a bit complicated, but here is a useful and typical
1205	example: Imagine you have a tcp connection and you want a so-called idle	1344	example: Imagine you have a TCP connection and you want a so-called idle
1206	timeout, that is, you want to be called when there have been, say, 60	1345	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to	1346	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1347	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If	1348	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the	1349	you go into an idle state where you do not expect data to travel on the
…		…
1224	ev_timer_again (loop, timer);	1363	ev_timer_again (loop, timer);
1225		1364
1226	This is more slightly efficient then stopping/starting the timer each time	1365	This is more slightly efficient then stopping/starting the timer each time
1227	you want to modify its timeout value.	1366	you want to modify its timeout value.
1228		1367
		1368	Note, however, that it is often even more efficient to remember the
		1369	time of the last activity and let the timer time-out naturally. In the
		1370	callback, you then check whether the time-out is real, or, if there was
		1371	some activity, you reschedule the watcher to time-out in "last_activity +
		1372	timeout - ev_now ()" seconds.
		1373
1229	=item ev_tstamp repeat [read-write]	1374	=item ev_tstamp repeat [read-write]
1230		1375
1231	The current C<repeat> value. Will be used each time the watcher times out	1376	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	1377	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	1378	which is also when any modifications are taken into account.
1234		1379
1235	=back	1380	=back
1236		1381
1237	=head3 Examples	1382	=head3 Examples
1238		1383
1239	Example: Create a timer that fires after 60 seconds.	1384	Example: Create a timer that fires after 60 seconds.
1240		1385
1241	static void	1386	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1387	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1243	{	1388	{
1244	.. one minute over, w is actually stopped right here	1389	.. one minute over, w is actually stopped right here
1245	}	1390	}
1246		1391
1247	struct ev_timer mytimer;	1392	struct ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1394	ev_timer_start (loop, &mytimer);
1250		1395
1251	Example: Create a timeout timer that times out after 10 seconds of	1396	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1397	inactivity.
1253		1398
1254	static void	1399	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1400	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1256	{	1401	{
1257	.. ten seconds without any activity	1402	.. ten seconds without any activity
1258	}	1403	}
1259		1404
1260	struct ev_timer mytimer;	1405	struct ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1407	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1408	ev_loop (loop, 0);
1264		1409
1265	// and in some piece of code that gets executed on any "activity":	1410	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1411	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1412	ev_timer_again (&mytimer);
1268		1413
1269		1414
1270	=head2 C<ev_periodic> - to cron or not to cron?	1415	=head2 C<ev_periodic> - to cron or not to cron?
1271		1416
1272	Periodic watchers are also timers of a kind, but they are very versatile	1417	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1418	(and unfortunately a bit complex).
1274		1419
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1420	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1421	but on wall clock time (absolute time). You can tell a periodic watcher
1277	to trigger "at" some specific point in time. For example, if you tell a	1422	to trigger after some specific point in time. For example, if you tell a
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1423	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1279	+ 10.>) and then reset your system clock to the last year, then it will	1424	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1425	clock to January of the previous year, then it will take more than year
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1281	roughly 10 seconds later).	1427	roughly 10 seconds later as it uses a relative timeout).
1282		1428
1283	They can also be used to implement vastly more complex timers, such as	1429	C<ev_periodic>s can also be used to implement vastly more complex timers,
1284	triggering an event on each midnight, local time or other, complicated,	1430	such as triggering an event on each "midnight, local time", or other
1285	rules.	1431	complicated rules.
1286		1432
1287	As with timers, the callback is guarenteed to be invoked only when the	1433	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1434	time (C<at>) has passed, but if multiple periodic timers become ready
1289	during the same loop iteration then order of execution is undefined.	1435	during the same loop iteration, then order of execution is undefined.
1290		1436
1291	=head3 Watcher-Specific Functions and Data Members	1437	=head3 Watcher-Specific Functions and Data Members
1292		1438
1293	=over 4	1439	=over 4
1294		1440
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1296		1442
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1298		1444
1299	Lots of arguments, lets sort it out... There are basically three modes of	1445	Lots of arguments, lets sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1446	operation, and we will explain them from simplest to most complex:
1301		1447
1302	=over 4	1448	=over 4
1303		1449
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305		1451
1306	In this configuration the watcher triggers an event at the wallclock time	1452	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1453	time C<at> has passed. It will not repeat and will not adjust when a time
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1309	system time reaches or surpasses this time.	1455	only run when the system clock reaches or surpasses this time.
1310		1456
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312		1458
1313	In this mode the watcher will always be scheduled to time out at the next	1459	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1460	C<at + N * interval> time (for some integer N, which can also be negative)
1315	and then repeat, regardless of any time jumps.	1461	and then repeat, regardless of any time jumps.
1316		1462
1317	This can be used to create timers that do not drift with respect to system	1463	This can be used to create timers that do not drift with respect to the
1318	time:	1464	system clock, for example, here is a C<ev_periodic> that triggers each
		1465	hour, on the hour:
1319		1466
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1467	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1468
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1469	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1470	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	1471	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1472	by 3600.
1326		1473
1327	Another way to think about it (for the mathematically inclined) is that	1474	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1475	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1476	time where C<time = at (mod interval)>, regardless of any time jumps.
1330		1477
1331	For numerical stability it is preferable that the C<at> value is near	1478	For numerical stability it is preferable that the C<at> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1479	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1480	this value, and in fact is often specified as zero.
		1481
		1482	Note also that there is an upper limit to how often a timer can fire (CPU
		1483	speed for example), so if C<interval> is very small then timing stability
		1484	will of course deteriorate. Libev itself tries to be exact to be about one
		1485	millisecond (if the OS supports it and the machine is fast enough).
1334		1486
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336		1488
1337	In this mode the values for C<interval> and C<at> are both being	1489	In this mode the values for C<interval> and C<at> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1490	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1491	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1492	current time as second argument.
1341		1493
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1494	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1343	ever, or make any event loop modifications>. If you need to stop it,	1495	ever, or make ANY event loop modifications whatsoever>.
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1496
		1497	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1498	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1499	only event loop modification you are allowed to do).
		1500
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1501	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1348	ev_tstamp now)>, e.g.:	1502	*w, ev_tstamp now)>, e.g.:
1349		1503
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1504	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1351	{	1505	{
1352	return now + 60.;	1506	return now + 60.;
1353	}	1507	}
…		…
1355	It must return the next time to trigger, based on the passed time value	1509	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	1510	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	1511	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1512	might be called at other times, too.
1359		1513
1360	NOTE: I<< This callback must always return a time that is later than the	1514	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1515	equal to the passed C<now> value >>.
1362		1516
1363	This can be used to create very complex timers, such as a timer that	1517	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	1518	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	1519	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	1520	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	1521	reason I omitted it as an example).
1368		1522
1369	=back	1523	=back
…		…
1403	=back	1557	=back
1404		1558
1405	=head3 Examples	1559	=head3 Examples
1406		1560
1407	Example: Call a callback every hour, or, more precisely, whenever the	1561	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1562	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1563	potentially a lot of jitter, but good long-term stability.
1410		1564
1411	static void	1565	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1413	{	1567	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1568	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1569	}
1416		1570
1417	struct ev_periodic hourly_tick;	1571	struct ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1573	ev_periodic_start (loop, &hourly_tick);
1420		1574
1421	Example: The same as above, but use a reschedule callback to do it:	1575	Example: The same as above, but use a reschedule callback to do it:
1422		1576
1423	#include <math.h>	1577	#include <math.h>
1424		1578
1425	static ev_tstamp	1579	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1427	{	1581	{
1428	return fmod (now, 3600.) + 3600.;	1582	return now + (3600. - fmod (now, 3600.));
1429	}	1583	}
1430		1584
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1586
1433	Example: Call a callback every hour, starting now:	1587	Example: Call a callback every hour, starting now:
1434		1588
1435	struct ev_periodic hourly_tick;	1589	struct ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1590	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1591	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1592	ev_periodic_start (loop, &hourly_tick);
1439		1593
1440		1594
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1595	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1596
1443	Signal watchers will trigger an event when the process receives a specific	1597	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	1598	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	1599	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1600	normal event processing, like any other event.
1447		1601
		1602	If you want signals asynchronously, just use C<sigaction> as you would
		1603	do without libev and forget about sharing the signal. You can even use
		1604	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1605
1448	You can configure as many watchers as you like per signal. Only when the	1606	You can configure as many watchers as you like per signal. Only when the
1449	first watcher gets started will libev actually register a signal watcher	1607	first watcher gets started will libev actually register a signal handler
1450	with the kernel (thus it coexists with your own signal handlers as long	1608	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	1609	you don't register any with libev for the same signal). Similarly, when
1452	watcher for a signal is stopped libev will reset the signal handler to	1610	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1611	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1612
1455	If possible and supported, libev will install its handlers with	1613	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1614	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1615	interrupted. If you have a problem with system calls getting interrupted by
1458	signals you can block all signals in an C<ev_check> watcher and unblock	1616	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1617	them in an C<ev_prepare> watcher.
1460		1618
1461	=head3 Watcher-Specific Functions and Data Members	1619	=head3 Watcher-Specific Functions and Data Members
1462		1620
…		…
1475		1633
1476	=back	1634	=back
1477		1635
1478	=head3 Examples	1636	=head3 Examples
1479		1637
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	1638	Example: Try to exit cleanly on SIGINT.
1481		1639
1482	static void	1640	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1484	{	1642	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	1643	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	1644	}
1487		1645
1488	struct ev_signal signal_watcher;	1646	struct ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	1648	ev_signal_start (loop, &signal_watcher);
1491		1649
1492		1650
1493	=head2 C<ev_child> - watch out for process status changes	1651	=head2 C<ev_child> - watch out for process status changes
1494		1652
1495	Child watchers trigger when your process receives a SIGCHLD in response to	1653	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	1654	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	1655	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	1656	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	1657	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1658	forking and then immediately registering a watcher for the child is fine,
		1659	but forking and registering a watcher a few event loop iterations later is
		1660	not.
1500		1661
1501	Only the default event loop is capable of handling signals, and therefore	1662	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	1663	you can only register child watchers in the default event loop.
1503		1664
1504	=head3 Process Interaction	1665	=head3 Process Interaction
1505		1666
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	1667	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	1668	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	1669	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1670	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	1671	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	1672	children, even ones not watched.
1512		1673
1513	=head3 Overriding the Built-In Processing	1674	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	1678	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	1679	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	1680	default loop never gets destroyed. You are encouraged, however, to use an
1520	event-based approach to child reaping and thus use libev's support for	1681	event-based approach to child reaping and thus use libev's support for
1521	that, so other libev users can use C<ev_child> watchers freely.	1682	that, so other libev users can use C<ev_child> watchers freely.
		1683
		1684	=head3 Stopping the Child Watcher
		1685
		1686	Currently, the child watcher never gets stopped, even when the
		1687	child terminates, so normally one needs to stop the watcher in the
		1688	callback. Future versions of libev might stop the watcher automatically
		1689	when a child exit is detected.
1522		1690
1523	=head3 Watcher-Specific Functions and Data Members	1691	=head3 Watcher-Specific Functions and Data Members
1524		1692
1525	=over 4	1693	=over 4
1526		1694
…		…
1555	=head3 Examples	1723	=head3 Examples
1556		1724
1557	Example: C<fork()> a new process and install a child handler to wait for	1725	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	1726	its completion.
1559		1727
1560	ev_child cw;	1728	ev_child cw;
1561		1729
1562	static void	1730	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	1731	child_cb (EV_P_ struct ev_child *w, int revents)
1564	{	1732	{
1565	ev_child_stop (EV_A_ w);	1733	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	1735	}
1568		1736
1569	pid_t pid = fork ();	1737	pid_t pid = fork ();
1570		1738
1571	if (pid < 0)	1739	if (pid < 0)
1572	// error	1740	// error
1573	else if (pid == 0)	1741	else if (pid == 0)
1574	{	1742	{
1575	// the forked child executes here	1743	// the forked child executes here
1576	exit (1);	1744	exit (1);
1577	}	1745	}
1578	else	1746	else
1579	{	1747	{
1580	ev_child_init (&cw, child_cb, pid, 0);	1748	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	1749	ev_child_start (EV_DEFAULT_ &cw);
1582	}	1750	}
1583		1751
1584		1752
1585	=head2 C<ev_stat> - did the file attributes just change?	1753	=head2 C<ev_stat> - did the file attributes just change?
1586		1754
1587	This watches a filesystem path for attribute changes. That is, it calls	1755	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	1756	C<stat> regularly (or when the OS says it changed) and sees if it changed
1589	compared to the last time, invoking the callback if it did.	1757	compared to the last time, invoking the callback if it did.
1590		1758
1591	The path does not need to exist: changing from "path exists" to "path does	1759	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	1760	not exist" is a status change like any other. The condition "path does
…		…
1595	the stat buffer having unspecified contents.	1763	the stat buffer having unspecified contents.
1596		1764
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	1765	The path I<should> be absolute and I<must not> end in a slash. If it is
1598	relative and your working directory changes, the behaviour is undefined.	1766	relative and your working directory changes, the behaviour is undefined.
1599		1767
1600	Since there is no standard to do this, the portable implementation simply	1768	Since there is no standard kernel interface to do this, the portable
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1769	implementation simply calls C<stat (2)> regularly on the path to see if
1602	can specify a recommended polling interval for this case. If you specify	1770	it changed somehow. You can specify a recommended polling interval for
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	1771	this case. If you specify a polling interval of C<0> (highly recommended!)
1604	unspecified default> value will be used (which you can expect to be around	1772	then a I<suitable, unspecified default> value will be used (which
1605	five seconds, although this might change dynamically). Libev will also	1773	you can expect to be around five seconds, although this might change
1606	impose a minimum interval which is currently around C<0.1>, but thats	1774	dynamically). Libev will also impose a minimum interval which is currently
1607	usually overkill.	1775	around C<0.1>, but thats usually overkill.
1608		1776
1609	This watcher type is not meant for massive numbers of stat watchers,	1777	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	1778	as even with OS-supported change notifications, this can be
1611	resource-intensive.	1779	resource-intensive.
1612		1780
1613	At the time of this writing, only the Linux inotify interface is	1781	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	1782	is the Linux inotify interface (implementing kqueue support is left as
1615	reader, note, however, that the author sees no way of implementing ev_stat	1783	an exercise for the reader. Note, however, that the author sees no way
1616	semantics with kqueue). Inotify will be used to give hints only and should	1784	of implementing C<ev_stat> semantics with kqueue).
1617	not change the semantics of C<ev_stat> watchers, which means that libev
1618	sometimes needs to fall back to regular polling again even with inotify,
1619	but changes are usually detected immediately, and if the file exists there
1620	will be no polling.
1621		1785
1622	=head3 ABI Issues (Largefile Support)	1786	=head3 ABI Issues (Largefile Support)
1623		1787
1624	Libev by default (unless the user overrides this) uses the default	1788	Libev by default (unless the user overrides this) uses the default
1625	compilation environment, which means that on systems with optionally	1789	compilation environment, which means that on systems with large file
1626	disabled large file support, you get the 32 bit version of the stat	1790	support disabled by default, you get the 32 bit version of the stat
1627	structure. When using the library from programs that change the ABI to	1791	structure. When using the library from programs that change the ABI to
1628	use 64 bit file offsets the programs will fail. In that case you have to	1792	use 64 bit file offsets the programs will fail. In that case you have to
1629	compile libev with the same flags to get binary compatibility. This is	1793	compile libev with the same flags to get binary compatibility. This is
1630	obviously the case with any flags that change the ABI, but the problem is	1794	obviously the case with any flags that change the ABI, but the problem is
1631	most noticably with ev_stat and largefile support.	1795	most noticeably disabled with ev_stat and large file support.
1632		1796
1633	=head3 Inotify	1797	The solution for this is to lobby your distribution maker to make large
		1798	file interfaces available by default (as e.g. FreeBSD does) and not
		1799	optional. Libev cannot simply switch on large file support because it has
		1800	to exchange stat structures with application programs compiled using the
		1801	default compilation environment.
1634		1802
		1803	=head3 Inotify and Kqueue
		1804
1635	When C<inotify (7)> support has been compiled into libev (generally only	1805	When C<inotify (7)> support has been compiled into libev (generally
		1806	only available with Linux 2.6.25 or above due to bugs in earlier
1636	available on Linux) and present at runtime, it will be used to speed up	1807	implementations) and present at runtime, it will be used to speed up
1637	change detection where possible. The inotify descriptor will be created lazily	1808	change detection where possible. The inotify descriptor will be created
1638	when the first C<ev_stat> watcher is being started.	1809	lazily when the first C<ev_stat> watcher is being started.
1639		1810
1640	Inotify presence does not change the semantics of C<ev_stat> watchers	1811	Inotify presence does not change the semantics of C<ev_stat> watchers
1641	except that changes might be detected earlier, and in some cases, to avoid	1812	except that changes might be detected earlier, and in some cases, to avoid
1642	making regular C<stat> calls. Even in the presence of inotify support	1813	making regular C<stat> calls. Even in the presence of inotify support
1643	there are many cases where libev has to resort to regular C<stat> polling.	1814	there are many cases where libev has to resort to regular C<stat> polling,
		1815	but as long as the path exists, libev usually gets away without polling.
1644		1816
1645	(There is no support for kqueue, as apparently it cannot be used to	1817	There is no support for kqueue, as apparently it cannot be used to
1646	implement this functionality, due to the requirement of having a file	1818	implement this functionality, due to the requirement of having a file
1647	descriptor open on the object at all times).	1819	descriptor open on the object at all times, and detecting renames, unlinks
		1820	etc. is difficult.
1648		1821
1649	=head3 The special problem of stat time resolution	1822	=head3 The special problem of stat time resolution
1650		1823
1651	The C<stat ()> syscall only supports full-second resolution portably, and	1824	The C<stat ()> system call only supports full-second resolution portably, and
1652	even on systems where the resolution is higher, many filesystems still	1825	even on systems where the resolution is higher, most file systems still
1653	only support whole seconds.	1826	only support whole seconds.
1654		1827
1655	That means that, if the time is the only thing that changes, you can	1828	That means that, if the time is the only thing that changes, you can
1656	easily miss updates: on the first update, C<ev_stat> detects a change and	1829	easily miss updates: on the first update, C<ev_stat> detects a change and
1657	calls your callback, which does something. When there is another update	1830	calls your callback, which does something. When there is another update
1658	within the same second, C<ev_stat> will be unable to detect it as the stat	1831	within the same second, C<ev_stat> will be unable to detect unless the
1659	data does not change.	1832	stat data does change in other ways (e.g. file size).
1660		1833
1661	The solution to this is to delay acting on a change for slightly more	1834	The solution to this is to delay acting on a change for slightly more
1662	than second (or till slightly after the next full second boundary), using	1835	than a second (or till slightly after the next full second boundary), using
1663	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1836	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664	ev_timer_again (loop, w)>).	1837	ev_timer_again (loop, w)>).
1665		1838
1666	The C<.02> offset is added to work around small timing inconsistencies	1839	The C<.02> offset is added to work around small timing inconsistencies
1667	of some operating systems (where the second counter of the current time	1840	of some operating systems (where the second counter of the current time
…		…
1684	C<path>. The C<interval> is a hint on how quickly a change is expected to	1857	C<path>. The C<interval> is a hint on how quickly a change is expected to
1685	be detected and should normally be specified as C<0> to let libev choose	1858	be detected and should normally be specified as C<0> to let libev choose
1686	a suitable value. The memory pointed to by C<path> must point to the same	1859	a suitable value. The memory pointed to by C<path> must point to the same
1687	path for as long as the watcher is active.	1860	path for as long as the watcher is active.
1688		1861
1689	The callback will receive C<EV_STAT> when a change was detected, relative	1862	The callback will receive an C<EV_STAT> event when a change was detected,
1690	to the attributes at the time the watcher was started (or the last change	1863	relative to the attributes at the time the watcher was started (or the
1691	was detected).	1864	last change was detected).
1692		1865
1693	=item ev_stat_stat (loop, ev_stat *)	1866	=item ev_stat_stat (loop, ev_stat *)
1694		1867
1695	Updates the stat buffer immediately with new values. If you change the	1868	Updates the stat buffer immediately with new values. If you change the
1696	watched path in your callback, you could call this function to avoid	1869	watched path in your callback, you could call this function to avoid
…		…
1717		1890
1718	The specified interval.	1891	The specified interval.
1719		1892
1720	=item const char *path [read-only]	1893	=item const char *path [read-only]
1721		1894
1722	The filesystem path that is being watched.	1895	The file system path that is being watched.
1723		1896
1724	=back	1897	=back
1725		1898
1726	=head3 Examples	1899	=head3 Examples
1727		1900
1728	Example: Watch C</etc/passwd> for attribute changes.	1901	Example: Watch C</etc/passwd> for attribute changes.
1729		1902
1730	static void	1903	static void
1731	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1904	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732	{	1905	{
1733	/* /etc/passwd changed in some way */	1906	/* /etc/passwd changed in some way */
1734	if (w->attr.st_nlink)	1907	if (w->attr.st_nlink)
1735	{	1908	{
1736	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1909	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1910	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1911	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739	}	1912	}
1740	else	1913	else
1741	/* you shalt not abuse printf for puts */	1914	/* you shalt not abuse printf for puts */
1742	puts ("wow, /etc/passwd is not there, expect problems. "	1915	puts ("wow, /etc/passwd is not there, expect problems. "
1743	"if this is windows, they already arrived\n");	1916	"if this is windows, they already arrived\n");
1744	}	1917	}
1745		1918
1746	...	1919	...
1747	ev_stat passwd;	1920	ev_stat passwd;
1748		1921
1749	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1922	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750	ev_stat_start (loop, &passwd);	1923	ev_stat_start (loop, &passwd);
1751		1924
1752	Example: Like above, but additionally use a one-second delay so we do not	1925	Example: Like above, but additionally use a one-second delay so we do not
1753	miss updates (however, frequent updates will delay processing, too, so	1926	miss updates (however, frequent updates will delay processing, too, so
1754	one might do the work both on C<ev_stat> callback invocation I<and> on	1927	one might do the work both on C<ev_stat> callback invocation I<and> on
1755	C<ev_timer> callback invocation).	1928	C<ev_timer> callback invocation).
1756		1929
1757	static ev_stat passwd;	1930	static ev_stat passwd;
1758	static ev_timer timer;	1931	static ev_timer timer;
1759		1932
1760	static void	1933	static void
1761	timer_cb (EV_P_ ev_timer *w, int revents)	1934	timer_cb (EV_P_ ev_timer *w, int revents)
1762	{	1935	{
1763	ev_timer_stop (EV_A_ w);	1936	ev_timer_stop (EV_A_ w);
1764		1937
1765	/* now it's one second after the most recent passwd change */	1938	/* now it's one second after the most recent passwd change */
1766	}	1939	}
1767		1940
1768	static void	1941	static void
1769	stat_cb (EV_P_ ev_stat *w, int revents)	1942	stat_cb (EV_P_ ev_stat *w, int revents)
1770	{	1943	{
1771	/* reset the one-second timer */	1944	/* reset the one-second timer */
1772	ev_timer_again (EV_A_ &timer);	1945	ev_timer_again (EV_A_ &timer);
1773	}	1946	}
1774		1947
1775	...	1948	...
1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1949	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777	ev_stat_start (loop, &passwd);	1950	ev_stat_start (loop, &passwd);
1778	ev_timer_init (&timer, timer_cb, 0., 1.02);	1951	ev_timer_init (&timer, timer_cb, 0., 1.02);
1779		1952
1780		1953
1781	=head2 C<ev_idle> - when you've got nothing better to do...	1954	=head2 C<ev_idle> - when you've got nothing better to do...
1782		1955
1783	Idle watchers trigger events when no other events of the same or higher	1956	Idle watchers trigger events when no other events of the same or higher
1784	priority are pending (prepare, check and other idle watchers do not	1957	priority are pending (prepare, check and other idle watchers do not count
1785	count).	1958	as receiving "events").
1786		1959
1787	That is, as long as your process is busy handling sockets or timeouts	1960	That is, as long as your process is busy handling sockets or timeouts
1788	(or even signals, imagine) of the same or higher priority it will not be	1961	(or even signals, imagine) of the same or higher priority it will not be
1789	triggered. But when your process is idle (or only lower-priority watchers	1962	triggered. But when your process is idle (or only lower-priority watchers
1790	are pending), the idle watchers are being called once per event loop	1963	are pending), the idle watchers are being called once per event loop
…		…
1814	=head3 Examples	1987	=head3 Examples
1815		1988
1816	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817	callback, free it. Also, use no error checking, as usual.	1990	callback, free it. Also, use no error checking, as usual.
1818		1991
1819	static void	1992	static void
1820	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1993	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1821	{	1994	{
1822	free (w);	1995	free (w);
1823	// now do something you wanted to do when the program has	1996	// now do something you wanted to do when the program has
1824	// no longer anything immediate to do.	1997	// no longer anything immediate to do.
1825	}	1998	}
1826		1999
1827	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1828	ev_idle_init (idle_watcher, idle_cb);	2001	ev_idle_init (idle_watcher, idle_cb);
1829	ev_idle_start (loop, idle_cb);	2002	ev_idle_start (loop, idle_cb);
1830		2003
1831		2004
1832	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833		2006
1834	Prepare and check watchers are usually (but not always) used in tandem:	2007	Prepare and check watchers are usually (but not always) used in pairs:
1835	prepare watchers get invoked before the process blocks and check watchers	2008	prepare watchers get invoked before the process blocks and check watchers
1836	afterwards.	2009	afterwards.
1837		2010
1838	You I<must not> call C<ev_loop> or similar functions that enter	2011	You I<must not> call C<ev_loop> or similar functions that enter
1839	the current event loop from either C<ev_prepare> or C<ev_check>	2012	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1842	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2015	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1843	C<ev_check> so if you have one watcher of each kind they will always be	2016	C<ev_check> so if you have one watcher of each kind they will always be
1844	called in pairs bracketing the blocking call.	2017	called in pairs bracketing the blocking call.
1845		2018
1846	Their main purpose is to integrate other event mechanisms into libev and	2019	Their main purpose is to integrate other event mechanisms into libev and
1847	their use is somewhat advanced. This could be used, for example, to track	2020	their use is somewhat advanced. They could be used, for example, to track
1848	variable changes, implement your own watchers, integrate net-snmp or a	2021	variable changes, implement your own watchers, integrate net-snmp or a
1849	coroutine library and lots more. They are also occasionally useful if	2022	coroutine library and lots more. They are also occasionally useful if
1850	you cache some data and want to flush it before blocking (for example,	2023	you cache some data and want to flush it before blocking (for example,
1851	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2024	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1852	watcher).	2025	watcher).
1853		2026
1854	This is done by examining in each prepare call which file descriptors need	2027	This is done by examining in each prepare call which file descriptors
1855	to be watched by the other library, registering C<ev_io> watchers for	2028	need to be watched by the other library, registering C<ev_io> watchers
1856	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2029	for them and starting an C<ev_timer> watcher for any timeouts (many
1857	provide just this functionality). Then, in the check watcher you check for	2030	libraries provide exactly this functionality). Then, in the check watcher,
1858	any events that occured (by checking the pending status of all watchers	2031	you check for any events that occurred (by checking the pending status
1859	and stopping them) and call back into the library. The I/O and timer	2032	of all watchers and stopping them) and call back into the library. The
1860	callbacks will never actually be called (but must be valid nevertheless,	2033	I/O and timer callbacks will never actually be called (but must be valid
1861	because you never know, you know?).	2034	nevertheless, because you never know, you know?).
1862		2035
1863	As another example, the Perl Coro module uses these hooks to integrate	2036	As another example, the Perl Coro module uses these hooks to integrate
1864	coroutines into libev programs, by yielding to other active coroutines	2037	coroutines into libev programs, by yielding to other active coroutines
1865	during each prepare and only letting the process block if no coroutines	2038	during each prepare and only letting the process block if no coroutines
1866	are ready to run (it's actually more complicated: it only runs coroutines	2039	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1869	loop from blocking if lower-priority coroutines are active, thus mapping	2042	loop from blocking if lower-priority coroutines are active, thus mapping
1870	low-priority coroutines to idle/background tasks).	2043	low-priority coroutines to idle/background tasks).
1871		2044
1872	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2045	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1873	priority, to ensure that they are being run before any other watchers	2046	priority, to ensure that they are being run before any other watchers
		2047	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2048
1874	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2049	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1875	too) should not activate ("feed") events into libev. While libev fully	2050	activate ("feed") events into libev. While libev fully supports this, they
1876	supports this, they might get executed before other C<ev_check> watchers	2051	might get executed before other C<ev_check> watchers did their job. As
1877	did their job. As C<ev_check> watchers are often used to embed other	2052	C<ev_check> watchers are often used to embed other (non-libev) event
1878	(non-libev) event loops those other event loops might be in an unusable	2053	loops those other event loops might be in an unusable state until their
1879	state until their C<ev_check> watcher ran (always remind yourself to	2054	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1880	coexist peacefully with others).	2055	others).
1881		2056
1882	=head3 Watcher-Specific Functions and Data Members	2057	=head3 Watcher-Specific Functions and Data Members
1883		2058
1884	=over 4	2059	=over 4
1885		2060
…		…
1887		2062
1888	=item ev_check_init (ev_check *, callback)	2063	=item ev_check_init (ev_check *, callback)
1889		2064
1890	Initialises and configures the prepare or check watcher - they have no	2065	Initialises and configures the prepare or check watcher - they have no
1891	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2066	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1892	macros, but using them is utterly, utterly and completely pointless.	2067	macros, but using them is utterly, utterly, utterly and completely
		2068	pointless.
1893		2069
1894	=back	2070	=back
1895		2071
1896	=head3 Examples	2072	=head3 Examples
1897		2073
…		…
1906	and in a check watcher, destroy them and call into libadns. What follows	2082	and in a check watcher, destroy them and call into libadns. What follows
1907	is pseudo-code only of course. This requires you to either use a low	2083	is pseudo-code only of course. This requires you to either use a low
1908	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2084	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1909	the callbacks for the IO/timeout watchers might not have been called yet.	2085	the callbacks for the IO/timeout watchers might not have been called yet.
1910		2086
1911	static ev_io iow [nfd];	2087	static ev_io iow [nfd];
1912	static ev_timer tw;	2088	static ev_timer tw;
1913		2089
1914	static void	2090	static void
1915	io_cb (ev_loop *loop, ev_io *w, int revents)	2091	io_cb (ev_loop *loop, ev_io *w, int revents)
1916	{	2092	{
1917	}	2093	}
1918		2094
1919	// create io watchers for each fd and a timer before blocking	2095	// create io watchers for each fd and a timer before blocking
1920	static void	2096	static void
1921	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2097	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1922	{	2098	{
1923	int timeout = 3600000;	2099	int timeout = 3600000;
1924	struct pollfd fds [nfd];	2100	struct pollfd fds [nfd];
1925	// actual code will need to loop here and realloc etc.	2101	// actual code will need to loop here and realloc etc.
1926	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927		2103
1928	/* the callback is illegal, but won't be called as we stop during check */	2104	/* the callback is illegal, but won't be called as we stop during check */
1929	ev_timer_init (&tw, 0, timeout * 1e-3);	2105	ev_timer_init (&tw, 0, timeout * 1e-3);
1930	ev_timer_start (loop, &tw);	2106	ev_timer_start (loop, &tw);
1931		2107
1932	// create one ev_io per pollfd	2108	// create one ev_io per pollfd
1933	for (int i = 0; i < nfd; ++i)	2109	for (int i = 0; i < nfd; ++i)
1934	{	2110	{
1935	ev_io_init (iow + i, io_cb, fds [i].fd,	2111	ev_io_init (iow + i, io_cb, fds [i].fd,
1936	((fds [i].events & POLLIN ? EV_READ : 0)	2112	((fds [i].events & POLLIN ? EV_READ : 0)
1937	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2113	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938		2114
1939	fds [i].revents = 0;	2115	fds [i].revents = 0;
1940	ev_io_start (loop, iow + i);	2116	ev_io_start (loop, iow + i);
1941	}	2117	}
1942	}	2118	}
1943		2119
1944	// stop all watchers after blocking	2120	// stop all watchers after blocking
1945	static void	2121	static void
1946	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2122	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1947	{	2123	{
1948	ev_timer_stop (loop, &tw);	2124	ev_timer_stop (loop, &tw);
1949		2125
1950	for (int i = 0; i < nfd; ++i)	2126	for (int i = 0; i < nfd; ++i)
1951	{	2127	{
1952	// set the relevant poll flags	2128	// set the relevant poll flags
1953	// could also call adns_processreadable etc. here	2129	// could also call adns_processreadable etc. here
1954	struct pollfd *fd = fds + i;	2130	struct pollfd *fd = fds + i;
1955	int revents = ev_clear_pending (iow + i);	2131	int revents = ev_clear_pending (iow + i);
1956	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2132	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2133	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958		2134
1959	// now stop the watcher	2135	// now stop the watcher
1960	ev_io_stop (loop, iow + i);	2136	ev_io_stop (loop, iow + i);
1961	}	2137	}
1962		2138
1963	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2139	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964	}	2140	}
1965		2141
1966	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2142	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1967	in the prepare watcher and would dispose of the check watcher.	2143	in the prepare watcher and would dispose of the check watcher.
1968		2144
1969	Method 3: If the module to be embedded supports explicit event	2145	Method 3: If the module to be embedded supports explicit event
1970	notification (adns does), you can also make use of the actual watcher	2146	notification (libadns does), you can also make use of the actual watcher
1971	callbacks, and only destroy/create the watchers in the prepare watcher.	2147	callbacks, and only destroy/create the watchers in the prepare watcher.
1972		2148
1973	static void	2149	static void
1974	timer_cb (EV_P_ ev_timer *w, int revents)	2150	timer_cb (EV_P_ ev_timer *w, int revents)
1975	{	2151	{
1976	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1977	update_now (EV_A);	2153	update_now (EV_A);
1978		2154
1979	adns_processtimeouts (ads, &tv_now);	2155	adns_processtimeouts (ads, &tv_now);
1980	}	2156	}
1981		2157
1982	static void	2158	static void
1983	io_cb (EV_P_ ev_io *w, int revents)	2159	io_cb (EV_P_ ev_io *w, int revents)
1984	{	2160	{
1985	adns_state ads = (adns_state)w->data;	2161	adns_state ads = (adns_state)w->data;
1986	update_now (EV_A);	2162	update_now (EV_A);
1987		2163
1988	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2164	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2165	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990	}	2166	}
1991		2167
1992	// do not ever call adns_afterpoll	2168	// do not ever call adns_afterpoll
1993		2169
1994	Method 4: Do not use a prepare or check watcher because the module you	2170	Method 4: Do not use a prepare or check watcher because the module you
1995	want to embed is too inflexible to support it. Instead, youc na override	2171	want to embed is not flexible enough to support it. Instead, you can
1996	their poll function. The drawback with this solution is that the main	2172	override their poll function. The drawback with this solution is that the
1997	loop is now no longer controllable by EV. The C<Glib::EV> module does	2173	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1998	this.	2174	this approach, effectively embedding EV as a client into the horrible
		2175	libglib event loop.
1999		2176
2000	static gint	2177	static gint
2001	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2178	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002	{	2179	{
2003	int got_events = 0;	2180	int got_events = 0;
2004		2181
2005	for (n = 0; n < nfds; ++n)	2182	for (n = 0; n < nfds; ++n)
2006	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2183	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007		2184
2008	if (timeout >= 0)	2185	if (timeout >= 0)
2009	// create/start timer	2186	// create/start timer
2010		2187
2011	// poll	2188	// poll
2012	ev_loop (EV_A_ 0);	2189	ev_loop (EV_A_ 0);
2013		2190
2014	// stop timer again	2191	// stop timer again
2015	if (timeout >= 0)	2192	if (timeout >= 0)
2016	ev_timer_stop (EV_A_ &to);	2193	ev_timer_stop (EV_A_ &to);
2017		2194
2018	// stop io watchers again - their callbacks should have set	2195	// stop io watchers again - their callbacks should have set
2019	for (n = 0; n < nfds; ++n)	2196	for (n = 0; n < nfds; ++n)
2020	ev_io_stop (EV_A_ iow [n]);	2197	ev_io_stop (EV_A_ iow [n]);
2021		2198
2022	return got_events;	2199	return got_events;
2023	}	2200	}
2024		2201
2025		2202
2026	=head2 C<ev_embed> - when one backend isn't enough...	2203	=head2 C<ev_embed> - when one backend isn't enough...
2027		2204
2028	This is a rather advanced watcher type that lets you embed one event loop	2205	This is a rather advanced watcher type that lets you embed one event loop
…		…
2034	prioritise I/O.	2211	prioritise I/O.
2035		2212
2036	As an example for a bug workaround, the kqueue backend might only support	2213	As an example for a bug workaround, the kqueue backend might only support
2037	sockets on some platform, so it is unusable as generic backend, but you	2214	sockets on some platform, so it is unusable as generic backend, but you
2038	still want to make use of it because you have many sockets and it scales	2215	still want to make use of it because you have many sockets and it scales
2039	so nicely. In this case, you would create a kqueue-based loop and embed it	2216	so nicely. In this case, you would create a kqueue-based loop and embed
2040	into your default loop (which might use e.g. poll). Overall operation will	2217	it into your default loop (which might use e.g. poll). Overall operation
2041	be a bit slower because first libev has to poll and then call kevent, but	2218	will be a bit slower because first libev has to call C<poll> and then
2042	at least you can use both at what they are best.	2219	C<kevent>, but at least you can use both mechanisms for what they are
		2220	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2043		2221
2044	As for prioritising I/O: rarely you have the case where some fds have	2222	As for prioritising I/O: under rare circumstances you have the case where
2045	to be watched and handled very quickly (with low latency), and even	2223	some fds have to be watched and handled very quickly (with low latency),
2046	priorities and idle watchers might have too much overhead. In this case	2224	and even priorities and idle watchers might have too much overhead. In
2047	you would put all the high priority stuff in one loop and all the rest in	2225	this case you would put all the high priority stuff in one loop and all
2048	a second one, and embed the second one in the first.	2226	the rest in a second one, and embed the second one in the first.
2049		2227
2050	As long as the watcher is active, the callback will be invoked every time	2228	As long as the watcher is active, the callback will be invoked every time
2051	there might be events pending in the embedded loop. The callback must then	2229	there might be events pending in the embedded loop. The callback must then
2052	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2053	their callbacks (you could also start an idle watcher to give the embedded	2231	their callbacks (you could also start an idle watcher to give the embedded
…		…
2061	interested in that.	2239	interested in that.
2062		2240
2063	Also, there have not currently been made special provisions for forking:	2241	Also, there have not currently been made special provisions for forking:
2064	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2065	but you will also have to stop and restart any C<ev_embed> watchers	2243	but you will also have to stop and restart any C<ev_embed> watchers
2066	yourself.	2244	yourself - but you can use a fork watcher to handle this automatically,
		2245	and future versions of libev might do just that.
2067		2246
2068	Unfortunately, not all backends are embeddable, only the ones returned by	2247	Unfortunately, not all backends are embeddable: only the ones returned by
2069	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2070	portable one.	2249	portable one.
2071		2250
2072	So when you want to use this feature you will always have to be prepared	2251	So when you want to use this feature you will always have to be prepared
2073	that you cannot get an embeddable loop. The recommended way to get around	2252	that you cannot get an embeddable loop. The recommended way to get around
2074	this is to have a separate variables for your embeddable loop, try to	2253	this is to have a separate variables for your embeddable loop, try to
2075	create it, and if that fails, use the normal loop for everything.	2254	create it, and if that fails, use the normal loop for everything.
2076		2255
		2256	=head3 C<ev_embed> and fork
		2257
		2258	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2259	automatically be applied to the embedded loop as well, so no special
		2260	fork handling is required in that case. When the watcher is not running,
		2261	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2262	as applicable.
		2263
2077	=head3 Watcher-Specific Functions and Data Members	2264	=head3 Watcher-Specific Functions and Data Members
2078		2265
2079	=over 4	2266	=over 4
2080		2267
2081	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2268	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2084		2271
2085	Configures the watcher to embed the given loop, which must be	2272	Configures the watcher to embed the given loop, which must be
2086	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2273	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087	invoked automatically, otherwise it is the responsibility of the callback	2274	invoked automatically, otherwise it is the responsibility of the callback
2088	to invoke it (it will continue to be called until the sweep has been done,	2275	to invoke it (it will continue to be called until the sweep has been done,
2089	if you do not want thta, you need to temporarily stop the embed watcher).	2276	if you do not want that, you need to temporarily stop the embed watcher).
2090		2277
2091	=item ev_embed_sweep (loop, ev_embed *)	2278	=item ev_embed_sweep (loop, ev_embed *)
2092		2279
2093	Make a single, non-blocking sweep over the embedded loop. This works	2280	Make a single, non-blocking sweep over the embedded loop. This works
2094	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2281	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095	apropriate way for embedded loops.	2282	appropriate way for embedded loops.
2096		2283
2097	=item struct ev_loop *other [read-only]	2284	=item struct ev_loop *other [read-only]
2098		2285
2099	The embedded event loop.	2286	The embedded event loop.
2100		2287
…		…
2102		2289
2103	=head3 Examples	2290	=head3 Examples
2104		2291
2105	Example: Try to get an embeddable event loop and embed it into the default	2292	Example: Try to get an embeddable event loop and embed it into the default
2106	event loop. If that is not possible, use the default loop. The default	2293	event loop. If that is not possible, use the default loop. The default
2107	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2294	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2108	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109	used).	2296	used).
2110		2297
2111	struct ev_loop *loop_hi = ev_default_init (0);	2298	struct ev_loop *loop_hi = ev_default_init (0);
2112	struct ev_loop *loop_lo = 0;	2299	struct ev_loop *loop_lo = 0;
2113	struct ev_embed embed;	2300	struct ev_embed embed;
2114		2301
2115	// see if there is a chance of getting one that works	2302	// see if there is a chance of getting one that works
2116	// (remember that a flags value of 0 means autodetection)	2303	// (remember that a flags value of 0 means autodetection)
2117	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119	: 0;	2306	: 0;
2120		2307
2121	// if we got one, then embed it, otherwise default to loop_hi	2308	// if we got one, then embed it, otherwise default to loop_hi
2122	if (loop_lo)	2309	if (loop_lo)
2123	{	2310	{
2124	ev_embed_init (&embed, 0, loop_lo);	2311	ev_embed_init (&embed, 0, loop_lo);
2125	ev_embed_start (loop_hi, &embed);	2312	ev_embed_start (loop_hi, &embed);
2126	}	2313	}
2127	else	2314	else
2128	loop_lo = loop_hi;	2315	loop_lo = loop_hi;
2129		2316
2130	Example: Check if kqueue is available but not recommended and create	2317	Example: Check if kqueue is available but not recommended and create
2131	a kqueue backend for use with sockets (which usually work with any	2318	a kqueue backend for use with sockets (which usually work with any
2132	kqueue implementation). Store the kqueue/socket-only event loop in	2319	kqueue implementation). Store the kqueue/socket-only event loop in
2133	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134		2321
2135	struct ev_loop *loop = ev_default_init (0);	2322	struct ev_loop *loop = ev_default_init (0);
2136	struct ev_loop *loop_socket = 0;	2323	struct ev_loop *loop_socket = 0;
2137	struct ev_embed embed;	2324	struct ev_embed embed;
2138		2325
2139	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141	{	2328	{
2142	ev_embed_init (&embed, 0, loop_socket);	2329	ev_embed_init (&embed, 0, loop_socket);
2143	ev_embed_start (loop, &embed);	2330	ev_embed_start (loop, &embed);
2144	}	2331	}
2145		2332
2146	if (!loop_socket)	2333	if (!loop_socket)
2147	loop_socket = loop;	2334	loop_socket = loop;
2148		2335
2149	// now use loop_socket for all sockets, and loop for everything else	2336	// now use loop_socket for all sockets, and loop for everything else
2150		2337
2151		2338
2152	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2339	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153		2340
2154	Fork watchers are called when a C<fork ()> was detected (usually because	2341	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2198	is that the author does not know of a simple (or any) algorithm for a	2385	is that the author does not know of a simple (or any) algorithm for a
2199	multiple-writer-single-reader queue that works in all cases and doesn't	2386	multiple-writer-single-reader queue that works in all cases and doesn't
2200	need elaborate support such as pthreads.	2387	need elaborate support such as pthreads.
2201		2388
2202	That means that if you want to queue data, you have to provide your own	2389	That means that if you want to queue data, you have to provide your own
2203	queue. But at least I can tell you would implement locking around your	2390	queue. But at least I can tell you how to implement locking around your
2204	queue:	2391	queue:
2205		2392
2206	=over 4	2393	=over 4
2207		2394
2208	=item queueing from a signal handler context	2395	=item queueing from a signal handler context
2209		2396
2210	To implement race-free queueing, you simply add to the queue in the signal	2397	To implement race-free queueing, you simply add to the queue in the signal
2211	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2398	handler but you block the signal handler in the watcher callback. Here is
2212	some fictitiuous SIGUSR1 handler:	2399	an example that does that for some fictitious SIGUSR1 handler:
2213		2400
2214	static ev_async mysig;	2401	static ev_async mysig;
2215		2402
2216	static void	2403	static void
2217	sigusr1_handler (void)	2404	sigusr1_handler (void)
…		…
2284		2471
2285	=item ev_async_init (ev_async *, callback)	2472	=item ev_async_init (ev_async *, callback)
2286		2473
2287	Initialises and configures the async watcher - it has no parameters of any	2474	Initialises and configures the async watcher - it has no parameters of any
2288	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2289	believe me.	2476	trust me.
2290		2477
2291	=item ev_async_send (loop, ev_async *)	2478	=item ev_async_send (loop, ev_async *)
2292		2479
2293	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2295	C<ev_feed_event>, this call is safe to do in other threads, signal or	2482	C<ev_feed_event>, this call is safe to do from other threads, signal or
2296	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297	section below on what exactly this means).	2484	section below on what exactly this means).
2298		2485
2299	This call incurs the overhead of a syscall only once per loop iteration,	2486	This call incurs the overhead of a system call only once per loop iteration,
2300	so while the overhead might be noticable, it doesn't apply to repeated	2487	so while the overhead might be noticeable, it doesn't apply to repeated
2301	calls to C<ev_async_send>.	2488	calls to C<ev_async_send>.
2302		2489
2303	=item bool = ev_async_pending (ev_async *)	2490	=item bool = ev_async_pending (ev_async *)
2304		2491
2305	Returns a non-zero value when C<ev_async_send> has been called on the	2492	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2307	event loop.	2494	event loop.
2308		2495
2309	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2310	the loop iterates next and checks for the watcher to have become active,	2497	the loop iterates next and checks for the watcher to have become active,
2311	it will reset the flag again. C<ev_async_pending> can be used to very	2498	it will reset the flag again. C<ev_async_pending> can be used to very
2312	quickly check wether invoking the loop might be a good idea.	2499	quickly check whether invoking the loop might be a good idea.
2313		2500
2314	Not that this does I<not> check wether the watcher itself is pending, only	2501	Not that this does I<not> check whether the watcher itself is pending, only
2315	wether it has been requested to make this watcher pending.	2502	whether it has been requested to make this watcher pending.
2316		2503
2317	=back	2504	=back
2318		2505
2319		2506
2320	=head1 OTHER FUNCTIONS	2507	=head1 OTHER FUNCTIONS
…		…
2324	=over 4	2511	=over 4
2325		2512
2326	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2513	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2327		2514
2328	This function combines a simple timer and an I/O watcher, calls your	2515	This function combines a simple timer and an I/O watcher, calls your
2329	callback on whichever event happens first and automatically stop both	2516	callback on whichever event happens first and automatically stops both
2330	watchers. This is useful if you want to wait for a single event on an fd	2517	watchers. This is useful if you want to wait for a single event on an fd
2331	or timeout without having to allocate/configure/start/stop/free one or	2518	or timeout without having to allocate/configure/start/stop/free one or
2332	more watchers yourself.	2519	more watchers yourself.
2333		2520
2334	If C<fd> is less than 0, then no I/O watcher will be started and events	2521	If C<fd> is less than 0, then no I/O watcher will be started and the
2335	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2522	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2336	C<events> set will be craeted and started.	2523	the given C<fd> and C<events> set will be created and started.
2337		2524
2338	If C<timeout> is less than 0, then no timeout watcher will be	2525	If C<timeout> is less than 0, then no timeout watcher will be
2339	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2526	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2340	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2527	repeat = 0) will be started. C<0> is a valid timeout.
2341	dubious value.
2342		2528
2343	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2529	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2344	passed an C<revents> set like normal event callbacks (a combination of	2530	passed an C<revents> set like normal event callbacks (a combination of
2345	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2531	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346	value passed to C<ev_once>:	2532	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2533	a timeout and an io event at the same time - you probably should give io
		2534	events precedence.
2347		2535
		2536	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2537
2348	static void stdin_ready (int revents, void *arg)	2538	static void stdin_ready (int revents, void *arg)
2349	{	2539	{
2350	if (revents & EV_TIMEOUT)
2351	/* doh, nothing entered */;
2352	else if (revents & EV_READ)	2540	if (revents & EV_READ)
2353	/* stdin might have data for us, joy! */;	2541	/* stdin might have data for us, joy! */;
		2542	else if (revents & EV_TIMEOUT)
		2543	/* doh, nothing entered */;
2354	}	2544	}
2355		2545
2356	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357		2547
2358	=item ev_feed_event (ev_loop *, watcher *, int revents)	2548	=item ev_feed_event (ev_loop *, watcher *, int revents)
2359		2549
2360	Feeds the given event set into the event loop, as if the specified event	2550	Feeds the given event set into the event loop, as if the specified event
2361	had happened for the specified watcher (which must be a pointer to an	2551	had happened for the specified watcher (which must be a pointer to an
…		…
2366	Feed an event on the given fd, as if a file descriptor backend detected	2556	Feed an event on the given fd, as if a file descriptor backend detected
2367	the given events it.	2557	the given events it.
2368		2558
2369	=item ev_feed_signal_event (ev_loop *loop, int signum)	2559	=item ev_feed_signal_event (ev_loop *loop, int signum)
2370		2560
2371	Feed an event as if the given signal occured (C<loop> must be the default	2561	Feed an event as if the given signal occurred (C<loop> must be the default
2372	loop!).	2562	loop!).
2373		2563
2374	=back	2564	=back
2375		2565
2376		2566
…		…
2405	=back	2595	=back
2406		2596
2407	=head1 C++ SUPPORT	2597	=head1 C++ SUPPORT
2408		2598
2409	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2599	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410	you to use some convinience methods to start/stop watchers and also change	2600	you to use some convenience methods to start/stop watchers and also change
2411	the callback model to a model using method callbacks on objects.	2601	the callback model to a model using method callbacks on objects.
2412		2602
2413	To use it,	2603	To use it,
2414		2604
2415	#include <ev++.h>	2605	#include <ev++.h>
2416		2606
2417	This automatically includes F<ev.h> and puts all of its definitions (many	2607	This automatically includes F<ev.h> and puts all of its definitions (many
2418	of them macros) into the global namespace. All C++ specific things are	2608	of them macros) into the global namespace. All C++ specific things are
2419	put into the C<ev> namespace. It should support all the same embedding	2609	put into the C<ev> namespace. It should support all the same embedding
2420	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2610	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2487	your compiler is good :), then the method will be fully inlined into the	2677	your compiler is good :), then the method will be fully inlined into the
2488	thunking function, making it as fast as a direct C callback.	2678	thunking function, making it as fast as a direct C callback.
2489		2679
2490	Example: simple class declaration and watcher initialisation	2680	Example: simple class declaration and watcher initialisation
2491		2681
2492	struct myclass	2682	struct myclass
2493	{	2683	{
2494	void io_cb (ev::io &w, int revents) { }	2684	void io_cb (ev::io &w, int revents) { }
2495	}	2685	}
2496		2686
2497	myclass obj;	2687	myclass obj;
2498	ev::io iow;	2688	ev::io iow;
2499	iow.set <myclass, &myclass::io_cb> (&obj);	2689	iow.set <myclass, &myclass::io_cb> (&obj);
2500		2690
2501	=item w->set<function> (void *data = 0)	2691	=item w->set<function> (void *data = 0)
2502		2692
2503	Also sets a callback, but uses a static method or plain function as	2693	Also sets a callback, but uses a static method or plain function as
2504	callback. The optional C<data> argument will be stored in the watcher's	2694	callback. The optional C<data> argument will be stored in the watcher's
…		…
2506		2696
2507	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2697	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2508		2698
2509	See the method-C<set> above for more details.	2699	See the method-C<set> above for more details.
2510		2700
2511	Example:	2701	Example: Use a plain function as callback.
2512		2702
2513	static void io_cb (ev::io &w, int revents) { }	2703	static void io_cb (ev::io &w, int revents) { }
2514	iow.set <io_cb> ();	2704	iow.set <io_cb> ();
2515		2705
2516	=item w->set (struct ev_loop *)	2706	=item w->set (struct ev_loop *)
2517		2707
2518	Associates a different C<struct ev_loop> with this watcher. You can only	2708	Associates a different C<struct ev_loop> with this watcher. You can only
2519	do this when the watcher is inactive (and not pending either).	2709	do this when the watcher is inactive (and not pending either).
2520		2710
2521	=item w->set ([args])	2711	=item w->set ([arguments])
2522		2712
2523	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2713	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2524	called at least once. Unlike the C counterpart, an active watcher gets	2714	called at least once. Unlike the C counterpart, an active watcher gets
2525	automatically stopped and restarted when reconfiguring it with this	2715	automatically stopped and restarted when reconfiguring it with this
2526	method.	2716	method.
2527		2717
2528	=item w->start ()	2718	=item w->start ()
…		…
2552	=back	2742	=back
2553		2743
2554	Example: Define a class with an IO and idle watcher, start one of them in	2744	Example: Define a class with an IO and idle watcher, start one of them in
2555	the constructor.	2745	the constructor.
2556		2746
2557	class myclass	2747	class myclass
2558	{	2748	{
2559	ev::io io; void io_cb (ev::io &w, int revents);	2749	ev::io io ; void io_cb (ev::io &w, int revents);
2560	ev:idle idle void idle_cb (ev::idle &w, int revents);	2750	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2561		2751
2562	myclass (int fd)	2752	myclass (int fd)
2563	{	2753	{
2564	io .set <myclass, &myclass::io_cb > (this);	2754	io .set <myclass, &myclass::io_cb > (this);
2565	idle.set <myclass, &myclass::idle_cb> (this);	2755	idle.set <myclass, &myclass::idle_cb> (this);
2566		2756
2567	io.start (fd, ev::READ);	2757	io.start (fd, ev::READ);
2568	}	2758	}
2569	};	2759	};
2570		2760
2571		2761
2572	=head1 OTHER LANGUAGE BINDINGS	2762	=head1 OTHER LANGUAGE BINDINGS
2573		2763
2574	Libev does not offer other language bindings itself, but bindings for a	2764	Libev does not offer other language bindings itself, but bindings for a
2575	numbe rof languages exist in the form of third-party packages. If you know	2765	number of languages exist in the form of third-party packages. If you know
2576	any interesting language binding in addition to the ones listed here, drop	2766	any interesting language binding in addition to the ones listed here, drop
2577	me a note.	2767	me a note.
2578		2768
2579	=over 4	2769	=over 4
2580		2770
2581	=item Perl	2771	=item Perl
2582		2772
2583	The EV module implements the full libev API and is actually used to test	2773	The EV module implements the full libev API and is actually used to test
2584	libev. EV is developed together with libev. Apart from the EV core module,	2774	libev. EV is developed together with libev. Apart from the EV core module,
2585	there are additional modules that implement libev-compatible interfaces	2775	there are additional modules that implement libev-compatible interfaces
2586	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2776	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2587	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2777	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2778	and C<EV::Glib>).
2588		2779
2589	It can be found and installed via CPAN, its homepage is found at	2780	It can be found and installed via CPAN, its homepage is at
2590	L<http://software.schmorp.de/pkg/EV>.	2781	L<http://software.schmorp.de/pkg/EV>.
2591		2782
		2783	=item Python
		2784
		2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2786	seems to be quite complete and well-documented. Note, however, that the
		2787	patch they require for libev is outright dangerous as it breaks the ABI
		2788	for everybody else, and therefore, should never be applied in an installed
		2789	libev (if python requires an incompatible ABI then it needs to embed
		2790	libev).
		2791
2592	=item Ruby	2792	=item Ruby
2593		2793
2594	Tony Arcieri has written a ruby extension that offers access to a subset	2794	Tony Arcieri has written a ruby extension that offers access to a subset
2595	of the libev API and adds filehandle abstractions, asynchronous DNS and	2795	of the libev API and adds file handle abstractions, asynchronous DNS and
2596	more on top of it. It can be found via gem servers. Its homepage is at	2796	more on top of it. It can be found via gem servers. Its homepage is at
2597	L<http://rev.rubyforge.org/>.	2797	L<http://rev.rubyforge.org/>.
2598		2798
2599	=item D	2799	=item D
2600		2800
2601	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2602	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2603		2803
2604	=back	2804	=back
2605		2805
2606		2806
2607	=head1 MACRO MAGIC	2807	=head1 MACRO MAGIC
2608		2808
2609	Libev can be compiled with a variety of options, the most fundamantal	2809	Libev can be compiled with a variety of options, the most fundamental
2610	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2810	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611	functions and callbacks have an initial C<struct ev_loop *> argument.	2811	functions and callbacks have an initial C<struct ev_loop *> argument.
2612		2812
2613	To make it easier to write programs that cope with either variant, the	2813	To make it easier to write programs that cope with either variant, the
2614	following macros are defined:	2814	following macros are defined:
…		…
2619		2819
2620	This provides the loop I<argument> for functions, if one is required ("ev	2820	This provides the loop I<argument> for functions, if one is required ("ev
2621	loop argument"). The C<EV_A> form is used when this is the sole argument,	2821	loop argument"). The C<EV_A> form is used when this is the sole argument,
2622	C<EV_A_> is used when other arguments are following. Example:	2822	C<EV_A_> is used when other arguments are following. Example:
2623		2823
2624	ev_unref (EV_A);	2824	ev_unref (EV_A);
2625	ev_timer_add (EV_A_ watcher);	2825	ev_timer_add (EV_A_ watcher);
2626	ev_loop (EV_A_ 0);	2826	ev_loop (EV_A_ 0);
2627		2827
2628	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2828	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629	which is often provided by the following macro.	2829	which is often provided by the following macro.
2630		2830
2631	=item C<EV_P>, C<EV_P_>	2831	=item C<EV_P>, C<EV_P_>
2632		2832
2633	This provides the loop I<parameter> for functions, if one is required ("ev	2833	This provides the loop I<parameter> for functions, if one is required ("ev
2634	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2834	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2635	C<EV_P_> is used when other parameters are following. Example:	2835	C<EV_P_> is used when other parameters are following. Example:
2636		2836
2637	// this is how ev_unref is being declared	2837	// this is how ev_unref is being declared
2638	static void ev_unref (EV_P);	2838	static void ev_unref (EV_P);
2639		2839
2640	// this is how you can declare your typical callback	2840	// this is how you can declare your typical callback
2641	static void cb (EV_P_ ev_timer *w, int revents)	2841	static void cb (EV_P_ ev_timer *w, int revents)
2642		2842
2643	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2843	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644	suitable for use with C<EV_A>.	2844	suitable for use with C<EV_A>.
2645		2845
2646	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2846	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2662		2862
2663	Example: Declare and initialise a check watcher, utilising the above	2863	Example: Declare and initialise a check watcher, utilising the above
2664	macros so it will work regardless of whether multiple loops are supported	2864	macros so it will work regardless of whether multiple loops are supported
2665	or not.	2865	or not.
2666		2866
2667	static void	2867	static void
2668	check_cb (EV_P_ ev_timer *w, int revents)	2868	check_cb (EV_P_ ev_timer *w, int revents)
2669	{	2869	{
2670	ev_check_stop (EV_A_ w);	2870	ev_check_stop (EV_A_ w);
2671	}	2871	}
2672		2872
2673	ev_check check;	2873	ev_check check;
2674	ev_check_init (&check, check_cb);	2874	ev_check_init (&check, check_cb);
2675	ev_check_start (EV_DEFAULT_ &check);	2875	ev_check_start (EV_DEFAULT_ &check);
2676	ev_loop (EV_DEFAULT_ 0);	2876	ev_loop (EV_DEFAULT_ 0);
2677		2877
2678	=head1 EMBEDDING	2878	=head1 EMBEDDING
2679		2879
2680	Libev can (and often is) directly embedded into host	2880	Libev can (and often is) directly embedded into host
2681	applications. Examples of applications that embed it include the Deliantra	2881	applications. Examples of applications that embed it include the Deliantra
…		…
2688	libev somewhere in your source tree).	2888	libev somewhere in your source tree).
2689		2889
2690	=head2 FILESETS	2890	=head2 FILESETS
2691		2891
2692	Depending on what features you need you need to include one or more sets of files	2892	Depending on what features you need you need to include one or more sets of files
2693	in your app.	2893	in your application.
2694		2894
2695	=head3 CORE EVENT LOOP	2895	=head3 CORE EVENT LOOP
2696		2896
2697	To include only the libev core (all the C<ev_*> functions), with manual	2897	To include only the libev core (all the C<ev_*> functions), with manual
2698	configuration (no autoconf):	2898	configuration (no autoconf):
2699		2899
2700	#define EV_STANDALONE 1	2900	#define EV_STANDALONE 1
2701	#include "ev.c"	2901	#include "ev.c"
2702		2902
2703	This will automatically include F<ev.h>, too, and should be done in a	2903	This will automatically include F<ev.h>, too, and should be done in a
2704	single C source file only to provide the function implementations. To use	2904	single C source file only to provide the function implementations. To use
2705	it, do the same for F<ev.h> in all files wishing to use this API (best	2905	it, do the same for F<ev.h> in all files wishing to use this API (best
2706	done by writing a wrapper around F<ev.h> that you can include instead and	2906	done by writing a wrapper around F<ev.h> that you can include instead and
2707	where you can put other configuration options):	2907	where you can put other configuration options):
2708		2908
2709	#define EV_STANDALONE 1	2909	#define EV_STANDALONE 1
2710	#include "ev.h"	2910	#include "ev.h"
2711		2911
2712	Both header files and implementation files can be compiled with a C++	2912	Both header files and implementation files can be compiled with a C++
2713	compiler (at least, thats a stated goal, and breakage will be treated	2913	compiler (at least, thats a stated goal, and breakage will be treated
2714	as a bug).	2914	as a bug).
2715		2915
2716	You need the following files in your source tree, or in a directory	2916	You need the following files in your source tree, or in a directory
2717	in your include path (e.g. in libev/ when using -Ilibev):	2917	in your include path (e.g. in libev/ when using -Ilibev):
2718		2918
2719	ev.h	2919	ev.h
2720	ev.c	2920	ev.c
2721	ev_vars.h	2921	ev_vars.h
2722	ev_wrap.h	2922	ev_wrap.h
2723		2923
2724	ev_win32.c required on win32 platforms only	2924	ev_win32.c required on win32 platforms only
2725		2925
2726	ev_select.c only when select backend is enabled (which is enabled by default)	2926	ev_select.c only when select backend is enabled (which is enabled by default)
2727	ev_poll.c only when poll backend is enabled (disabled by default)	2927	ev_poll.c only when poll backend is enabled (disabled by default)
2728	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2928	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2729	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2929	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2730	ev_port.c only when the solaris port backend is enabled (disabled by default)	2930	ev_port.c only when the solaris port backend is enabled (disabled by default)
2731		2931
2732	F<ev.c> includes the backend files directly when enabled, so you only need	2932	F<ev.c> includes the backend files directly when enabled, so you only need
2733	to compile this single file.	2933	to compile this single file.
2734		2934
2735	=head3 LIBEVENT COMPATIBILITY API	2935	=head3 LIBEVENT COMPATIBILITY API
2736		2936
2737	To include the libevent compatibility API, also include:	2937	To include the libevent compatibility API, also include:
2738		2938
2739	#include "event.c"	2939	#include "event.c"
2740		2940
2741	in the file including F<ev.c>, and:	2941	in the file including F<ev.c>, and:
2742		2942
2743	#include "event.h"	2943	#include "event.h"
2744		2944
2745	in the files that want to use the libevent API. This also includes F<ev.h>.	2945	in the files that want to use the libevent API. This also includes F<ev.h>.
2746		2946
2747	You need the following additional files for this:	2947	You need the following additional files for this:
2748		2948
2749	event.h	2949	event.h
2750	event.c	2950	event.c
2751		2951
2752	=head3 AUTOCONF SUPPORT	2952	=head3 AUTOCONF SUPPORT
2753		2953
2754	Instead of using C<EV_STANDALONE=1> and providing your config in	2954	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2755	whatever way you want, you can also C<m4_include([libev.m4])> in your	2955	whatever way you want, you can also C<m4_include([libev.m4])> in your
2756	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2956	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757	include F<config.h> and configure itself accordingly.	2957	include F<config.h> and configure itself accordingly.
2758		2958
2759	For this of course you need the m4 file:	2959	For this of course you need the m4 file:
2760		2960
2761	libev.m4	2961	libev.m4
2762		2962
2763	=head2 PREPROCESSOR SYMBOLS/MACROS	2963	=head2 PREPROCESSOR SYMBOLS/MACROS
2764		2964
2765	Libev can be configured via a variety of preprocessor symbols you have to	2965	Libev can be configured via a variety of preprocessor symbols you have to
2766	define before including any of its files. The default in the absense of	2966	define before including any of its files. The default in the absence of
2767	autoconf is noted for every option.	2967	autoconf is documented for every option.
2768		2968
2769	=over 4	2969	=over 4
2770		2970
2771	=item EV_STANDALONE	2971	=item EV_STANDALONE
2772		2972
…		…
2777	F<event.h> that are not directly supported by the libev core alone.	2977	F<event.h> that are not directly supported by the libev core alone.
2778		2978
2779	=item EV_USE_MONOTONIC	2979	=item EV_USE_MONOTONIC
2780		2980
2781	If defined to be C<1>, libev will try to detect the availability of the	2981	If defined to be C<1>, libev will try to detect the availability of the
2782	monotonic clock option at both compiletime and runtime. Otherwise no use	2982	monotonic clock option at both compile time and runtime. Otherwise no use
2783	of the monotonic clock option will be attempted. If you enable this, you	2983	of the monotonic clock option will be attempted. If you enable this, you
2784	usually have to link against librt or something similar. Enabling it when	2984	usually have to link against librt or something similar. Enabling it when
2785	the functionality isn't available is safe, though, although you have	2985	the functionality isn't available is safe, though, although you have
2786	to make sure you link against any libraries where the C<clock_gettime>	2986	to make sure you link against any libraries where the C<clock_gettime>
2787	function is hiding in (often F<-lrt>).	2987	function is hiding in (often F<-lrt>).
2788		2988
2789	=item EV_USE_REALTIME	2989	=item EV_USE_REALTIME
2790		2990
2791	If defined to be C<1>, libev will try to detect the availability of the	2991	If defined to be C<1>, libev will try to detect the availability of the
2792	realtime clock option at compiletime (and assume its availability at	2992	real-time clock option at compile time (and assume its availability at
2793	runtime if successful). Otherwise no use of the realtime clock option will	2993	runtime if successful). Otherwise no use of the real-time clock option will
2794	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2795	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2796	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2797		2997
2798	=item EV_USE_NANOSLEEP	2998	=item EV_USE_NANOSLEEP
…		…
2809	2.7 or newer, otherwise disabled.	3009	2.7 or newer, otherwise disabled.
2810		3010
2811	=item EV_USE_SELECT	3011	=item EV_USE_SELECT
2812		3012
2813	If undefined or defined to be C<1>, libev will compile in support for the	3013	If undefined or defined to be C<1>, libev will compile in support for the
2814	C<select>(2) backend. No attempt at autodetection will be done: if no	3014	C<select>(2) backend. No attempt at auto-detection will be done: if no
2815	other method takes over, select will be it. Otherwise the select backend	3015	other method takes over, select will be it. Otherwise the select backend
2816	will not be compiled in.	3016	will not be compiled in.
2817		3017
2818	=item EV_SELECT_USE_FD_SET	3018	=item EV_SELECT_USE_FD_SET
2819		3019
2820	If defined to C<1>, then the select backend will use the system C<fd_set>	3020	If defined to C<1>, then the select backend will use the system C<fd_set>
2821	structure. This is useful if libev doesn't compile due to a missing	3021	structure. This is useful if libev doesn't compile due to a missing
2822	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2823	exotic systems. This usually limits the range of file descriptors to some	3023	exotic systems. This usually limits the range of file descriptors to some
2824	low limit such as 1024 or might have other limitations (winsocket only	3024	low limit such as 1024 or might have other limitations (winsocket only
2825	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2826	influence the size of the C<fd_set> used.	3026	influence the size of the C<fd_set> used.
2827		3027
…		…
2876	otherwise another method will be used as fallback. This is the preferred	3076	otherwise another method will be used as fallback. This is the preferred
2877	backend for Solaris 10 systems.	3077	backend for Solaris 10 systems.
2878		3078
2879	=item EV_USE_DEVPOLL	3079	=item EV_USE_DEVPOLL
2880		3080
2881	reserved for future expansion, works like the USE symbols above.	3081	Reserved for future expansion, works like the USE symbols above.
2882		3082
2883	=item EV_USE_INOTIFY	3083	=item EV_USE_INOTIFY
2884		3084
2885	If defined to be C<1>, libev will compile in support for the Linux inotify	3085	If defined to be C<1>, libev will compile in support for the Linux inotify
2886	interface to speed up C<ev_stat> watchers. Its actual availability will	3086	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2893	access is atomic with respect to other threads or signal contexts. No such	3093	access is atomic with respect to other threads or signal contexts. No such
2894	type is easily found in the C language, so you can provide your own type	3094	type is easily found in the C language, so you can provide your own type
2895	that you know is safe for your purposes. It is used both for signal handler "locking"	3095	that you know is safe for your purposes. It is used both for signal handler "locking"
2896	as well as for signal and thread safety in C<ev_async> watchers.	3096	as well as for signal and thread safety in C<ev_async> watchers.
2897		3097
2898	In the absense of this define, libev will use C<sig_atomic_t volatile>	3098	In the absence of this define, libev will use C<sig_atomic_t volatile>
2899	(from F<signal.h>), which is usually good enough on most platforms.	3099	(from F<signal.h>), which is usually good enough on most platforms.
2900		3100
2901	=item EV_H	3101	=item EV_H
2902		3102
2903	The name of the F<ev.h> header file used to include it. The default if	3103	The name of the F<ev.h> header file used to include it. The default if
…		…
2942	When doing priority-based operations, libev usually has to linearly search	3142	When doing priority-based operations, libev usually has to linearly search
2943	all the priorities, so having many of them (hundreds) uses a lot of space	3143	all the priorities, so having many of them (hundreds) uses a lot of space
2944	and time, so using the defaults of five priorities (-2 .. +2) is usually	3144	and time, so using the defaults of five priorities (-2 .. +2) is usually
2945	fine.	3145	fine.
2946		3146
2947	If your embedding app does not need any priorities, defining these both to	3147	If your embedding application does not need any priorities, defining these
2948	C<0> will save some memory and cpu.	3148	both to C<0> will save some memory and CPU.
2949		3149
2950	=item EV_PERIODIC_ENABLE	3150	=item EV_PERIODIC_ENABLE
2951		3151
2952	If undefined or defined to be C<1>, then periodic timers are supported. If	3152	If undefined or defined to be C<1>, then periodic timers are supported. If
2953	defined to be C<0>, then they are not. Disabling them saves a few kB of	3153	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2960	code.	3160	code.
2961		3161
2962	=item EV_EMBED_ENABLE	3162	=item EV_EMBED_ENABLE
2963		3163
2964	If undefined or defined to be C<1>, then embed watchers are supported. If	3164	If undefined or defined to be C<1>, then embed watchers are supported. If
2965	defined to be C<0>, then they are not.	3165	defined to be C<0>, then they are not. Embed watchers rely on most other
		3166	watcher types, which therefore must not be disabled.
2966		3167
2967	=item EV_STAT_ENABLE	3168	=item EV_STAT_ENABLE
2968		3169
2969	If undefined or defined to be C<1>, then stat watchers are supported. If	3170	If undefined or defined to be C<1>, then stat watchers are supported. If
2970	defined to be C<0>, then they are not.	3171	defined to be C<0>, then they are not.
…		…
2981		3182
2982	=item EV_MINIMAL	3183	=item EV_MINIMAL
2983		3184
2984	If you need to shave off some kilobytes of code at the expense of some	3185	If you need to shave off some kilobytes of code at the expense of some
2985	speed, define this symbol to C<1>. Currently this is used to override some	3186	speed, define this symbol to C<1>. Currently this is used to override some
2986	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3187	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2987	much smaller 2-heap for timer management over the default 4-heap.	3188	much smaller 2-heap for timer management over the default 4-heap.
2988		3189
2989	=item EV_PID_HASHSIZE	3190	=item EV_PID_HASHSIZE
2990		3191
2991	C<ev_child> watchers use a small hash table to distribute workload by	3192	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3002	two).	3203	two).
3003		3204
3004	=item EV_USE_4HEAP	3205	=item EV_USE_4HEAP
3005		3206
3006	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3207	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3007	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3208	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3008	to C<1>. The 4-heap uses more complicated (longer) code but has a	3209	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3009	noticable after performance with many (thousands) of watchers.	3210	faster performance with many (thousands) of watchers.
3010		3211
3011	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3012	(disabled).	3213	(disabled).
3013		3214
3014	=item EV_HEAP_CACHE_AT	3215	=item EV_HEAP_CACHE_AT
3015		3216
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3217	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev can cache the timestamp (I<at>) within	3218	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3018	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3219	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3019	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3220	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3020	but avoids random read accesses on heap changes. This noticably improves	3221	but avoids random read accesses on heap changes. This improves performance
3021	performance noticably with with many (hundreds) of watchers.	3222	noticeably with many (hundreds) of watchers.
3022		3223
3023	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3224	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3024	(disabled).	3225	(disabled).
		3226
		3227	=item EV_VERIFY
		3228
		3229	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3230	be done: If set to C<0>, no internal verification code will be compiled
		3231	in. If set to C<1>, then verification code will be compiled in, but not
		3232	called. If set to C<2>, then the internal verification code will be
		3233	called once per loop, which can slow down libev. If set to C<3>, then the
		3234	verification code will be called very frequently, which will slow down
		3235	libev considerably.
		3236
		3237	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3238	C<0>.
3025		3239
3026	=item EV_COMMON	3240	=item EV_COMMON
3027		3241
3028	By default, all watchers have a C<void *data> member. By redefining	3242	By default, all watchers have a C<void *data> member. By redefining
3029	this macro to a something else you can include more and other types of	3243	this macro to a something else you can include more and other types of
3030	members. You have to define it each time you include one of the files,	3244	members. You have to define it each time you include one of the files,
3031	though, and it must be identical each time.	3245	though, and it must be identical each time.
3032		3246
3033	For example, the perl EV module uses something like this:	3247	For example, the perl EV module uses something like this:
3034		3248
3035	#define EV_COMMON \	3249	#define EV_COMMON \
3036	SV *self; /* contains this struct */ \	3250	SV *self; /* contains this struct */ \
3037	SV *cb_sv, *fh /* note no trailing ";" */	3251	SV *cb_sv, *fh /* note no trailing ";" */
3038		3252
3039	=item EV_CB_DECLARE (type)	3253	=item EV_CB_DECLARE (type)
3040		3254
3041	=item EV_CB_INVOKE (watcher, revents)	3255	=item EV_CB_INVOKE (watcher, revents)
3042		3256
…		…
3047	definition and a statement, respectively. See the F<ev.h> header file for	3261	definition and a statement, respectively. See the F<ev.h> header file for
3048	their default definitions. One possible use for overriding these is to	3262	their default definitions. One possible use for overriding these is to
3049	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3263	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3050	method calls instead of plain function calls in C++.	3264	method calls instead of plain function calls in C++.
3051		3265
		3266	=back
		3267
3052	=head2 EXPORTED API SYMBOLS	3268	=head2 EXPORTED API SYMBOLS
3053		3269
3054	If you need to re-export the API (e.g. via a dll) and you need a list of	3270	If you need to re-export the API (e.g. via a DLL) and you need a list of
3055	exported symbols, you can use the provided F<Symbol.*> files which list	3271	exported symbols, you can use the provided F<Symbol.*> files which list
3056	all public symbols, one per line:	3272	all public symbols, one per line:
3057		3273
3058	Symbols.ev for libev proper	3274	Symbols.ev for libev proper
3059	Symbols.event for the libevent emulation	3275	Symbols.event for the libevent emulation
3060		3276
3061	This can also be used to rename all public symbols to avoid clashes with	3277	This can also be used to rename all public symbols to avoid clashes with
3062	multiple versions of libev linked together (which is obviously bad in	3278	multiple versions of libev linked together (which is obviously bad in
3063	itself, but sometimes it is inconvinient to avoid this).	3279	itself, but sometimes it is inconvenient to avoid this).
3064		3280
3065	A sed command like this will create wrapper C<#define>'s that you need to	3281	A sed command like this will create wrapper C<#define>'s that you need to
3066	include before including F<ev.h>:	3282	include before including F<ev.h>:
3067		3283
3068	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3284	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3085	file.	3301	file.
3086		3302
3087	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3303	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3088	that everybody includes and which overrides some configure choices:	3304	that everybody includes and which overrides some configure choices:
3089		3305
3090	#define EV_MINIMAL 1	3306	#define EV_MINIMAL 1
3091	#define EV_USE_POLL 0	3307	#define EV_USE_POLL 0
3092	#define EV_MULTIPLICITY 0	3308	#define EV_MULTIPLICITY 0
3093	#define EV_PERIODIC_ENABLE 0	3309	#define EV_PERIODIC_ENABLE 0
3094	#define EV_STAT_ENABLE 0	3310	#define EV_STAT_ENABLE 0
3095	#define EV_FORK_ENABLE 0	3311	#define EV_FORK_ENABLE 0
3096	#define EV_CONFIG_H <config.h>	3312	#define EV_CONFIG_H <config.h>
3097	#define EV_MINPRI 0	3313	#define EV_MINPRI 0
3098	#define EV_MAXPRI 0	3314	#define EV_MAXPRI 0
3099		3315
3100	#include "ev++.h"	3316	#include "ev++.h"
3101		3317
3102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3318	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3103		3319
3104	#include "ev_cpp.h"	3320	#include "ev_cpp.h"
3105	#include "ev.c"	3321	#include "ev.c"
3106		3322
		3323	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3107		3324
3108	=head1 THREADS AND COROUTINES	3325	=head2 THREADS AND COROUTINES
3109		3326
3110	=head2 THREADS	3327	=head3 THREADS
3111		3328
3112	Libev itself is completely threadsafe, but it uses no locking. This	3329	All libev functions are reentrant and thread-safe unless explicitly
		3330	documented otherwise, but libev implements no locking itself. This means
3113	means that you can use as many loops as you want in parallel, as long as	3331	that you can use as many loops as you want in parallel, as long as there
3114	only one thread ever calls into one libev function with the same loop	3332	are no concurrent calls into any libev function with the same loop
3115	parameter.	3333	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3334	of course): libev guarantees that different event loops share no data
		3335	structures that need any locking.
3116		3336
3117	Or put differently: calls with different loop parameters can be done in	3337	Or to put it differently: calls with different loop parameters can be done
3118	parallel from multiple threads, calls with the same loop parameter must be	3338	concurrently from multiple threads, calls with the same loop parameter
3119	done serially (but can be done from different threads, as long as only one	3339	must be done serially (but can be done from different threads, as long as
3120	thread ever is inside a call at any point in time, e.g. by using a mutex	3340	only one thread ever is inside a call at any point in time, e.g. by using
3121	per loop).	3341	a mutex per loop).
3122		3342
3123	If you want to know which design is best for your problem, then I cannot	3343	Specifically to support threads (and signal handlers), libev implements
		3344	so-called C<ev_async> watchers, which allow some limited form of
		3345	concurrency on the same event loop, namely waking it up "from the
		3346	outside".
		3347
		3348	If you want to know which design (one loop, locking, or multiple loops
		3349	without or something else still) is best for your problem, then I cannot
3124	help you but by giving some generic advice:	3350	help you, but here is some generic advice:
3125		3351
3126	=over 4	3352	=over 4
3127		3353
3128	=item * most applications have a main thread: use the default libev loop	3354	=item * most applications have a main thread: use the default libev loop
3129	in that thread, or create a seperate thread running only the default loop.	3355	in that thread, or create a separate thread running only the default loop.
3130		3356
3131	This helps integrating other libraries or software modules that use libev	3357	This helps integrating other libraries or software modules that use libev
3132	themselves and don't care/know about threading.	3358	themselves and don't care/know about threading.
3133		3359
3134	=item * one loop per thread is usually a good model.	3360	=item * one loop per thread is usually a good model.
3135		3361
3136	Doing this is almost never wrong, sometimes a better-performance model	3362	Doing this is almost never wrong, sometimes a better-performance model
3137	exists, but it is always a good start.	3363	exists, but it is always a good start.
3138		3364
3139	=item * other models exist, such as the leader/follower pattern, where one	3365	=item * other models exist, such as the leader/follower pattern, where one
3140	loop is handed through multiple threads in a kind of round-robbin fashion.	3366	loop is handed through multiple threads in a kind of round-robin fashion.
3141		3367
3142	Chosing a model is hard - look around, learn, know that usually you cna do	3368	Choosing a model is hard - look around, learn, know that usually you can do
3143	better than you currently do :-)	3369	better than you currently do :-)
3144		3370
3145	=item * often you need to talk to some other thread which blocks in the	3371	=item * often you need to talk to some other thread which blocks in the
		3372	event loop.
		3373
3146	event loop - C<ev_async> watchers can be used to wake them up from other	3374	C<ev_async> watchers can be used to wake them up from other threads safely
3147	threads safely (or from signal contexts...).	3375	(or from signal contexts...).
		3376
		3377	An example use would be to communicate signals or other events that only
		3378	work in the default loop by registering the signal watcher with the
		3379	default loop and triggering an C<ev_async> watcher from the default loop
		3380	watcher callback into the event loop interested in the signal.
3148		3381
3149	=back	3382	=back
3150		3383
3151	=head2 COROUTINES	3384	=head3 COROUTINES
3152		3385
3153	Libev is much more accomodating to coroutines ("cooperative threads"):	3386	Libev is very accommodating to coroutines ("cooperative threads"):
3154	libev fully supports nesting calls to it's functions from different	3387	libev fully supports nesting calls to its functions from different
3155	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3156	different coroutines and switch freely between both coroutines running the	3389	different coroutines, and switch freely between both coroutines running the
3157	loop, as long as you don't confuse yourself). The only exception is that	3390	loop, as long as you don't confuse yourself). The only exception is that
3158	you must not do this from C<ev_periodic> reschedule callbacks.	3391	you must not do this from C<ev_periodic> reschedule callbacks.
3159		3392
3160	Care has been invested into making sure that libev does not keep local	3393	Care has been taken to ensure that libev does not keep local state inside
3161	state inside C<ev_loop>, and other calls do not usually allow coroutine	3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3162	switches.	3395	they do not clal any callbacks.
3163		3396
		3397	=head2 COMPILER WARNINGS
3164		3398
3165	=head1 COMPLEXITIES	3399	Depending on your compiler and compiler settings, you might get no or a
		3400	lot of warnings when compiling libev code. Some people are apparently
		3401	scared by this.
3166		3402
3167	In this section the complexities of (many of) the algorithms used inside	3403	However, these are unavoidable for many reasons. For one, each compiler
3168	libev will be explained. For complexity discussions about backends see the	3404	has different warnings, and each user has different tastes regarding
3169	documentation for C<ev_default_init>.	3405	warning options. "Warn-free" code therefore cannot be a goal except when
		3406	targeting a specific compiler and compiler-version.
3170		3407
3171	All of the following are about amortised time: If an array needs to be	3408	Another reason is that some compiler warnings require elaborate
3172	extended, libev needs to realloc and move the whole array, but this	3409	workarounds, or other changes to the code that make it less clear and less
3173	happens asymptotically never with higher number of elements, so O(1) might	3410	maintainable.
3174	mean it might do a lengthy realloc operation in rare cases, but on average
3175	it is much faster and asymptotically approaches constant time.
3176		3411
3177	=over 4	3412	And of course, some compiler warnings are just plain stupid, or simply
		3413	wrong (because they don't actually warn about the condition their message
		3414	seems to warn about). For example, certain older gcc versions had some
		3415	warnings that resulted an extreme number of false positives. These have
		3416	been fixed, but some people still insist on making code warn-free with
		3417	such buggy versions.
3178		3418
3179	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3419	While libev is written to generate as few warnings as possible,
		3420	"warn-free" code is not a goal, and it is recommended not to build libev
		3421	with any compiler warnings enabled unless you are prepared to cope with
		3422	them (e.g. by ignoring them). Remember that warnings are just that:
		3423	warnings, not errors, or proof of bugs.
3180		3424
3181	This means that, when you have a watcher that triggers in one hour and
3182	there are 100 watchers that would trigger before that then inserting will
3183	have to skip roughly seven (C<ld 100>) of these watchers.
3184		3425
3185	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3426	=head2 VALGRIND
3186		3427
3187	That means that changing a timer costs less than removing/adding them	3428	Valgrind has a special section here because it is a popular tool that is
3188	as only the relative motion in the event queue has to be paid for.	3429	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3189		3430
3190	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3431	If you think you found a bug (memory leak, uninitialised data access etc.)
		3432	in libev, then check twice: If valgrind reports something like:
3191		3433
3192	These just add the watcher into an array or at the head of a list.	3434	==2274== definitely lost: 0 bytes in 0 blocks.
		3435	==2274== possibly lost: 0 bytes in 0 blocks.
		3436	==2274== still reachable: 256 bytes in 1 blocks.
3193		3437
3194	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3438	Then there is no memory leak, just as memory accounted to global variables
		3439	is not a memleak - the memory is still being refernced, and didn't leak.
3195		3440
3196	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3441	Similarly, under some circumstances, valgrind might report kernel bugs
		3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3443	although an acceptable workaround has been found here), or it might be
		3444	confused.
3197		3445
3198	These watchers are stored in lists then need to be walked to find the	3446	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3199	correct watcher to remove. The lists are usually short (you don't usually	3447	make it into some kind of religion.
3200	have many watchers waiting for the same fd or signal).
3201		3448
3202	=item Finding the next timer in each loop iteration: O(1)	3449	If you are unsure about something, feel free to contact the mailing list
		3450	with the full valgrind report and an explanation on why you think this
		3451	is a bug in libev (best check the archives, too :). However, don't be
		3452	annoyed when you get a brisk "this is no bug" answer and take the chance
		3453	of learning how to interpret valgrind properly.
3203		3454
3204	By virtue of using a binary or 4-heap, the next timer is always found at a	3455	If you need, for some reason, empty reports from valgrind for your project
3205	fixed position in the storage array.	3456	I suggest using suppression lists.
3206		3457
3207	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3208		3458
3209	A change means an I/O watcher gets started or stopped, which requires	3459	=head1 PORTABILITY NOTES
3210	libev to recalculate its status (and possibly tell the kernel, depending
3211	on backend and wether C<ev_io_set> was used).
3212		3460
3213	=item Activating one watcher (putting it into the pending state): O(1)	3461	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3214
3215	=item Priority handling: O(number_of_priorities)
3216
3217	Priorities are implemented by allocating some space for each
3218	priority. When doing priority-based operations, libev usually has to
3219	linearly search all the priorities, but starting/stopping and activating
3220	watchers becomes O(1) w.r.t. priority handling.
3221
3222	=item Sending an ev_async: O(1)
3223
3224	=item Processing ev_async_send: O(number_of_async_watchers)
3225
3226	=item Processing signals: O(max_signal_number)
3227
3228	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3229	calls in the current loop iteration. Checking for async and signal events
3230	involves iterating over all running async watchers or all signal numbers.
3231
3232	=back
3233
3234
3235	=head1 Win32 platform limitations and workarounds
3236		3462
3237	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3463	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3238	requires, and its I/O model is fundamentally incompatible with the POSIX	3464	requires, and its I/O model is fundamentally incompatible with the POSIX
3239	model. Libev still offers limited functionality on this platform in	3465	model. Libev still offers limited functionality on this platform in
3240	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3466	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3247	way (note also that glib is the slowest event library known to man).	3473	way (note also that glib is the slowest event library known to man).
3248		3474
3249	There is no supported compilation method available on windows except	3475	There is no supported compilation method available on windows except
3250	embedding it into other applications.	3476	embedding it into other applications.
3251		3477
		3478	Not a libev limitation but worth mentioning: windows apparently doesn't
		3479	accept large writes: instead of resulting in a partial write, windows will
		3480	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3481	so make sure you only write small amounts into your sockets (less than a
		3482	megabyte seems safe, but this apparently depends on the amount of memory
		3483	available).
		3484
3252	Due to the many, low, and arbitrary limits on the win32 platform and	3485	Due to the many, low, and arbitrary limits on the win32 platform and
3253	the abysmal performance of winsockets, using a large number of sockets	3486	the abysmal performance of winsockets, using a large number of sockets
3254	is not recommended (and not reasonable). If your program needs to use	3487	is not recommended (and not reasonable). If your program needs to use
3255	more than a hundred or so sockets, then likely it needs to use a totally	3488	more than a hundred or so sockets, then likely it needs to use a totally
3256	different implementation for windows, as libev offers the POSIX readyness	3489	different implementation for windows, as libev offers the POSIX readiness
3257	notification model, which cannot be implemented efficiently on windows	3490	notification model, which cannot be implemented efficiently on windows
3258	(microsoft monopoly games).	3491	(Microsoft monopoly games).
		3492
		3493	A typical way to use libev under windows is to embed it (see the embedding
		3494	section for details) and use the following F<evwrap.h> header file instead
		3495	of F<ev.h>:
		3496
		3497	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3498	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3499
		3500	#include "ev.h"
		3501
		3502	And compile the following F<evwrap.c> file into your project (make sure
		3503	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3504
		3505	#include "evwrap.h"
		3506	#include "ev.c"
3259		3507
3260	=over 4	3508	=over 4
3261		3509
3262	=item The winsocket select function	3510	=item The winsocket select function
3263		3511
3264	The winsocket C<select> function doesn't follow POSIX in that it requires	3512	The winsocket C<select> function doesn't follow POSIX in that it
3265	socket I<handles> and not socket I<file descriptors>. This makes select	3513	requires socket I<handles> and not socket I<file descriptors> (it is
3266	very inefficient, and also requires a mapping from file descriptors	3514	also extremely buggy). This makes select very inefficient, and also
3267	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3515	requires a mapping from file descriptors to socket handles (the Microsoft
3268	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3516	C runtime provides the function C<_open_osfhandle> for this). See the
3269	symbols for more info.	3517	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3518	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3270		3519
3271	The configuration for a "naked" win32 using the microsoft runtime	3520	The configuration for a "naked" win32 using the Microsoft runtime
3272	libraries and raw winsocket select is:	3521	libraries and raw winsocket select is:
3273		3522
3274	#define EV_USE_SELECT 1	3523	#define EV_USE_SELECT 1
3275	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3524	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3276		3525
3277	Note that winsockets handling of fd sets is O(n), so you can easily get a	3526	Note that winsockets handling of fd sets is O(n), so you can easily get a
3278	complexity in the O(n²) range when using win32.	3527	complexity in the O(n²) range when using win32.
3279		3528
3280	=item Limited number of file descriptors	3529	=item Limited number of file descriptors
3281		3530
3282	Windows has numerous arbitrary (and low) limits on things.	3531	Windows has numerous arbitrary (and low) limits on things.
3283		3532
3284	Early versions of winsocket's select only supported waiting for a maximum	3533	Early versions of winsocket's select only supported waiting for a maximum
3285	of C<64> handles (probably owning to the fact that all windows kernels	3534	of C<64> handles (probably owning to the fact that all windows kernels
3286	can only wait for C<64> things at the same time internally; microsoft	3535	can only wait for C<64> things at the same time internally; Microsoft
3287	recommends spawning a chain of threads and wait for 63 handles and the	3536	recommends spawning a chain of threads and wait for 63 handles and the
3288	previous thread in each. Great).	3537	previous thread in each. Great).
3289		3538
3290	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3539	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3291	to some high number (e.g. C<2048>) before compiling the winsocket select	3540	to some high number (e.g. C<2048>) before compiling the winsocket select
3292	call (which might be in libev or elsewhere, for example, perl does its own	3541	call (which might be in libev or elsewhere, for example, perl does its own
3293	select emulation on windows).	3542	select emulation on windows).
3294		3543
3295	Another limit is the number of file descriptors in the microsoft runtime	3544	Another limit is the number of file descriptors in the Microsoft runtime
3296	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3545	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3297	or something like this inside microsoft). You can increase this by calling	3546	or something like this inside Microsoft). You can increase this by calling
3298	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3547	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3299	arbitrary limit), but is broken in many versions of the microsoft runtime	3548	arbitrary limit), but is broken in many versions of the Microsoft runtime
3300	libraries.	3549	libraries.
3301		3550
3302	This might get you to about C<512> or C<2048> sockets (depending on	3551	This might get you to about C<512> or C<2048> sockets (depending on
3303	windows version and/or the phase of the moon). To get more, you need to	3552	windows version and/or the phase of the moon). To get more, you need to
3304	wrap all I/O functions and provide your own fd management, but the cost of	3553	wrap all I/O functions and provide your own fd management, but the cost of
3305	calling select (O(n²)) will likely make this unworkable.	3554	calling select (O(n²)) will likely make this unworkable.
3306		3555
3307	=back	3556	=back
3308		3557
3309
3310	=head1 PORTABILITY REQUIREMENTS	3558	=head2 PORTABILITY REQUIREMENTS
3311		3559
3312	In addition to a working ISO-C implementation, libev relies on a few	3560	In addition to a working ISO-C implementation and of course the
3313	additional extensions:	3561	backend-specific APIs, libev relies on a few additional extensions:
3314		3562
3315	=over 4	3563	=over 4
3316		3564
		3565	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3566	calling conventions regardless of C<ev_watcher_type *>.
		3567
		3568	Libev assumes not only that all watcher pointers have the same internal
		3569	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3570	assumes that the same (machine) code can be used to call any watcher
		3571	callback: The watcher callbacks have different type signatures, but libev
		3572	calls them using an C<ev_watcher *> internally.
		3573
3317	=item C<sig_atomic_t volatile> must be thread-atomic as well	3574	=item C<sig_atomic_t volatile> must be thread-atomic as well
3318		3575
3319	The type C<sig_atomic_t volatile> (or whatever is defined as	3576	The type C<sig_atomic_t volatile> (or whatever is defined as
3320	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3577	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3321	threads. This is not part of the specification for C<sig_atomic_t>, but is	3578	threads. This is not part of the specification for C<sig_atomic_t>, but is
3322	believed to be sufficiently portable.	3579	believed to be sufficiently portable.
3323		3580
3324	=item C<sigprocmask> must work in a threaded environment	3581	=item C<sigprocmask> must work in a threaded environment
3325		3582
…		…
3334	except the initial one, and run the default loop in the initial thread as	3591	except the initial one, and run the default loop in the initial thread as
3335	well.	3592	well.
3336		3593
3337	=item C<long> must be large enough for common memory allocation sizes	3594	=item C<long> must be large enough for common memory allocation sizes
3338		3595
3339	To improve portability and simplify using libev, libev uses C<long>	3596	To improve portability and simplify its API, libev uses C<long> internally
3340	internally instead of C<size_t> when allocating its data structures. On	3597	instead of C<size_t> when allocating its data structures. On non-POSIX
3341	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3598	systems (Microsoft...) this might be unexpectedly low, but is still at
3342	is still at least 31 bits everywhere, which is enough for hundreds of	3599	least 31 bits everywhere, which is enough for hundreds of millions of
3343	millions of watchers.	3600	watchers.
3344		3601
3345	=item C<double> must hold a time value in seconds with enough accuracy	3602	=item C<double> must hold a time value in seconds with enough accuracy
3346		3603
3347	The type C<double> is used to represent timestamps. It is required to	3604	The type C<double> is used to represent timestamps. It is required to
3348	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3352	=back	3609	=back
3353		3610
3354	If you know of other additional requirements drop me a note.	3611	If you know of other additional requirements drop me a note.
3355		3612
3356		3613
		3614	=head1 ALGORITHMIC COMPLEXITIES
		3615
		3616	In this section the complexities of (many of) the algorithms used inside
		3617	libev will be documented. For complexity discussions about backends see
		3618	the documentation for C<ev_default_init>.
		3619
		3620	All of the following are about amortised time: If an array needs to be
		3621	extended, libev needs to realloc and move the whole array, but this
		3622	happens asymptotically rarer with higher number of elements, so O(1) might
		3623	mean that libev does a lengthy realloc operation in rare cases, but on
		3624	average it is much faster and asymptotically approaches constant time.
		3625
		3626	=over 4
		3627
		3628	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3629
		3630	This means that, when you have a watcher that triggers in one hour and
		3631	there are 100 watchers that would trigger before that, then inserting will
		3632	have to skip roughly seven (C<ld 100>) of these watchers.
		3633
		3634	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3635
		3636	That means that changing a timer costs less than removing/adding them,
		3637	as only the relative motion in the event queue has to be paid for.
		3638
		3639	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3640
		3641	These just add the watcher into an array or at the head of a list.
		3642
		3643	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3644
		3645	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3646
		3647	These watchers are stored in lists, so they need to be walked to find the
		3648	correct watcher to remove. The lists are usually short (you don't usually
		3649	have many watchers waiting for the same fd or signal: one is typical, two
		3650	is rare).
		3651
		3652	=item Finding the next timer in each loop iteration: O(1)
		3653
		3654	By virtue of using a binary or 4-heap, the next timer is always found at a
		3655	fixed position in the storage array.
		3656
		3657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3658
		3659	A change means an I/O watcher gets started or stopped, which requires
		3660	libev to recalculate its status (and possibly tell the kernel, depending
		3661	on backend and whether C<ev_io_set> was used).
		3662
		3663	=item Activating one watcher (putting it into the pending state): O(1)
		3664
		3665	=item Priority handling: O(number_of_priorities)
		3666
		3667	Priorities are implemented by allocating some space for each
		3668	priority. When doing priority-based operations, libev usually has to
		3669	linearly search all the priorities, but starting/stopping and activating
		3670	watchers becomes O(1) with respect to priority handling.
		3671
		3672	=item Sending an ev_async: O(1)
		3673
		3674	=item Processing ev_async_send: O(number_of_async_watchers)
		3675
		3676	=item Processing signals: O(max_signal_number)
		3677
		3678	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3679	calls in the current loop iteration. Checking for async and signal events
		3680	involves iterating over all running async watchers or all signal numbers.
		3681
		3682	=back
		3683
		3684
3357	=head1 AUTHOR	3685	=head1 AUTHOR
3358		3686
3359	Marc Lehmann <libev@schmorp.de>.	3687	Marc Lehmann <libev@schmorp.de>.
3360		3688

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines