[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs.
Revision 1.370 by root, Thu Jun 2 23:42:40 2011 UTC

…		…
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_run (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
442		442
443	This behaviour is useful when you want to do your own signal handling, or	443	This behaviour is useful when you want to do your own signal handling, or
444	want to handle signals only in specific threads and want to avoid libev	444	want to handle signals only in specific threads and want to avoid libev
445	unblocking the signals.	445	unblocking the signals.
446		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
447	This flag's behaviour will become the default in future versions of libev.	450	This flag's behaviour will become the default in future versions of libev.
448		451
449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
450		453
451	This is your standard select(2) backend. Not I<completely> standard, as	454	This is your standard select(2) backend. Not I<completely> standard, as
…		…
480	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
481		484
482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
483	kernels).	486	kernels).
484		487
485	For few fds, this backend is a bit little slower than poll and select,	488	For few fds, this backend is a bit little slower than poll and select, but
486	but it scales phenomenally better. While poll and select usually scale	489	it scales phenomenally better. While poll and select usually scale like
487	like O(total_fds) where n is the total number of fds (or the highest fd),	490	O(total_fds) where total_fds is the total number of fds (or the highest
488	epoll scales either O(1) or O(active_fds).	491	fd), epoll scales either O(1) or O(active_fds).
489		492
490	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
491	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
492	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
493	descriptor (and unnecessary guessing of parameters), problems with dup,	496	descriptor (and unnecessary guessing of parameters), problems with dup,
…		…
496	0.1ms) and so on. The biggest issue is fork races, however - if a program	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
497	forks then I<both> parent and child process have to recreate the epoll	500	forks then I<both> parent and child process have to recreate the epoll
498	set, which can take considerable time (one syscall per file descriptor)	501	set, which can take considerable time (one syscall per file descriptor)
499	and is of course hard to detect.	502	and is of course hard to detect.
500		503
501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
502	of course I<doesn't>, and epoll just loves to report events for totally	505	but of course I<doesn't>, and epoll just loves to report events for
503	I<different> file descriptors (even already closed ones, so one cannot	506	totally I<different> file descriptors (even already closed ones, so
504	even remove them from the set) than registered in the set (especially	507	one cannot even remove them from the set) than registered in the set
505	on SMP systems). Libev tries to counter these spurious notifications by	508	(especially on SMP systems). Libev tries to counter these spurious
506	employing an additional generation counter and comparing that against the	509	notifications by employing an additional generation counter and comparing
507	events to filter out spurious ones, recreating the set when required. Last	510	that against the events to filter out spurious ones, recreating the set
		511	when required. Epoll also errornously rounds down timeouts, but gives you
		512	no way to know when and by how much, so sometimes you have to busy-wait
		513	because epoll returns immediately despite a nonzero timeout. And last
508	not least, it also refuses to work with some file descriptors which work	514	not least, it also refuses to work with some file descriptors which work
509	perfectly fine with C<select> (files, many character devices...).	515	perfectly fine with C<select> (files, many character devices...).
510		516
511	Epoll is truly the train wreck analog among event poll mechanisms,	517	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
512	a frankenpoll, cobbled together in a hurry, no thought to design or	518	cobbled together in a hurry, no thought to design or interaction with
513	interaction with others.	519	others. Oh, the pain, will it ever stop...
514		520
515	While stopping, setting and starting an I/O watcher in the same iteration	521	While stopping, setting and starting an I/O watcher in the same iteration
516	will result in some caching, there is still a system call per such	522	will result in some caching, there is still a system call per such
517	incident (because the same I<file descriptor> could point to a different	523	incident (because the same I<file descriptor> could point to a different
518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	524	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
822	This is useful if you are waiting for some external event in conjunction	828	This is useful if you are waiting for some external event in conjunction
823	with something not expressible using other libev watchers (i.e. "roll your	829	with something not expressible using other libev watchers (i.e. "roll your
824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	830	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
825	usually a better approach for this kind of thing.	831	usually a better approach for this kind of thing.
826		832
827	Here are the gory details of what C<ev_run> does:	833	Here are the gory details of what C<ev_run> does (this is for your
		834	understanding, not a guarantee that things will work exactly like this in
		835	future versions):
828		836
829	- Increment loop depth.	837	- Increment loop depth.
830	- Reset the ev_break status.	838	- Reset the ev_break status.
831	- Before the first iteration, call any pending watchers.	839	- Before the first iteration, call any pending watchers.
832	LOOP:	840	LOOP:
…		…
865	anymore.	873	anymore.
866		874
867	... queue jobs here, make sure they register event watchers as long	875	... queue jobs here, make sure they register event watchers as long
868	... as they still have work to do (even an idle watcher will do..)	876	... as they still have work to do (even an idle watcher will do..)
869	ev_run (my_loop, 0);	877	ev_run (my_loop, 0);
870	... jobs done or somebody called unloop. yeah!	878	... jobs done or somebody called break. yeah!
871		879
872	=item ev_break (loop, how)	880	=item ev_break (loop, how)
873		881
874	Can be used to make a call to C<ev_run> return early (but only after it	882	Can be used to make a call to C<ev_run> return early (but only after it
875	has processed all outstanding events). The C<how> argument must be either	883	has processed all outstanding events). The C<how> argument must be either
…		…
1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1365	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1358	functions that do not need a watcher.	1366	functions that do not need a watcher.
1359		1367
1360	=back	1368	=back
1361		1369
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1370	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
1363		1371	OWN COMPOSITE WATCHERS> idioms.
1364	Each watcher has, by default, a member C<void *data> that you can change
1365	and read at any time: libev will completely ignore it. This can be used
1366	to associate arbitrary data with your watcher. If you need more data and
1367	don't want to allocate memory and store a pointer to it in that data
1368	member, you can also "subclass" the watcher type and provide your own
1369	data:
1370
1371	struct my_io
1372	{
1373	ev_io io;
1374	int otherfd;
1375	void *somedata;
1376	struct whatever *mostinteresting;
1377	};
1378
1379	...
1380	struct my_io w;
1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1382
1383	And since your callback will be called with a pointer to the watcher, you
1384	can cast it back to your own type:
1385
1386	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1387	{
1388	struct my_io w = (struct my_io )w_;
1389	...
1390	}
1391
1392	More interesting and less C-conformant ways of casting your callback type
1393	instead have been omitted.
1394
1395	Another common scenario is to use some data structure with multiple
1396	embedded watchers:
1397
1398	struct my_biggy
1399	{
1400	int some_data;
1401	ev_timer t1;
1402	ev_timer t2;
1403	}
1404
1405	In this case getting the pointer to C<my_biggy> is a bit more
1406	complicated: Either you store the address of your C<my_biggy> struct
1407	in the C<data> member of the watcher (for woozies), or you need to use
1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
1409	programmers):
1410
1411	#include <stddef.h>
1412
1413	static void
1414	t1_cb (EV_P_ ev_timer *w, int revents)
1415	{
1416	struct my_biggy big = (struct my_biggy *)
1417	(((char *)w) - offsetof (struct my_biggy, t1));
1418	}
1419
1420	static void
1421	t2_cb (EV_P_ ev_timer *w, int revents)
1422	{
1423	struct my_biggy big = (struct my_biggy *)
1424	(((char *)w) - offsetof (struct my_biggy, t2));
1425	}
1426		1372
1427	=head2 WATCHER STATES	1373	=head2 WATCHER STATES
1428		1374
1429	There are various watcher states mentioned throughout this manual -	1375	There are various watcher states mentioned throughout this manual -
1430	active, pending and so on. In this section these states and the rules to	1376	active, pending and so on. In this section these states and the rules to
…		…
1437		1383
1438	Before a watcher can be registered with the event looop it has to be	1384	Before a watcher can be registered with the event looop it has to be
1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1385	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1386	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1441		1387
1442	In this state it is simply some block of memory that is suitable for use	1388	In this state it is simply some block of memory that is suitable for
1443	in an event loop. It can be moved around, freed, reused etc. at will.	1389	use in an event loop. It can be moved around, freed, reused etc. at
		1390	will - as long as you either keep the memory contents intact, or call
		1391	C<ev_TYPE_init> again.
1444		1392
1445	=item started/running/active	1393	=item started/running/active
1446		1394
1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1395	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1448	property of the event loop, and is actively waiting for events. While in	1396	property of the event loop, and is actively waiting for events. While in
…		…
1476	latter will clear any pending state the watcher might be in, regardless	1424	latter will clear any pending state the watcher might be in, regardless
1477	of whether it was active or not, so stopping a watcher explicitly before	1425	of whether it was active or not, so stopping a watcher explicitly before
1478	freeing it is often a good idea.	1426	freeing it is often a good idea.
1479		1427
1480	While stopped (and not pending) the watcher is essentially in the	1428	While stopped (and not pending) the watcher is essentially in the
1481	initialised state, that is it can be reused, moved, modified in any way	1429	initialised state, that is, it can be reused, moved, modified in any way
1482	you wish.	1430	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1431	it again).
1483		1432
1484	=back	1433	=back
1485		1434
1486	=head2 WATCHER PRIORITY MODELS	1435	=head2 WATCHER PRIORITY MODELS
1487		1436
…		…
1680	always get a readiness notification instantly, and your read (or possibly	1629	always get a readiness notification instantly, and your read (or possibly
1681	write) will still block on the disk I/O.	1630	write) will still block on the disk I/O.
1682		1631
1683	Another way to view it is that in the case of sockets, pipes, character	1632	Another way to view it is that in the case of sockets, pipes, character
1684	devices and so on, there is another party (the sender) that delivers data	1633	devices and so on, there is another party (the sender) that delivers data
1685	on it's own, but in the case of files, there is no such thing: the disk	1634	on its own, but in the case of files, there is no such thing: the disk
1686	will not send data on it's own, simply because it doesn't know what you	1635	will not send data on its own, simply because it doesn't know what you
1687	wish to read - you would first have to request some data.	1636	wish to read - you would first have to request some data.
1688		1637
1689	Since files are typically not-so-well supported by advanced notification	1638	Since files are typically not-so-well supported by advanced notification
1690	mechanism, libev tries hard to emulate POSIX behaviour with respect	1639	mechanism, libev tries hard to emulate POSIX behaviour with respect
1691	to files, even though you should not use it. The reason for this is	1640	to files, even though you should not use it. The reason for this is
…		…
2207		2156
2208	Another way to think about it (for the mathematically inclined) is that	2157	Another way to think about it (for the mathematically inclined) is that
2209	C<ev_periodic> will try to run the callback in this mode at the next possible	2158	C<ev_periodic> will try to run the callback in this mode at the next possible
2210	time where C<time = offset (mod interval)>, regardless of any time jumps.	2159	time where C<time = offset (mod interval)>, regardless of any time jumps.
2211		2160
2212	For numerical stability it is preferable that the C<offset> value is near	2161	The C<interval> I<MUST> be positive, and for numerical stability, the
2213	C<ev_now ()> (the current time), but there is no range requirement for	2162	interval value should be higher than C<1/8192> (which is around 100
2214	this value, and in fact is often specified as zero.	2163	microseconds) and C<offset> should be higher than C<0> and should have
		2164	at most a similar magnitude as the current time (say, within a factor of
		2165	ten). Typical values for offset are, in fact, C<0> or something between
		2166	C<0> and C<interval>, which is also the recommended range.
2215		2167
2216	Note also that there is an upper limit to how often a timer can fire (CPU	2168	Note also that there is an upper limit to how often a timer can fire (CPU
2217	speed for example), so if C<interval> is very small then timing stability	2169	speed for example), so if C<interval> is very small then timing stability
2218	will of course deteriorate. Libev itself tries to be exact to be about one	2170	will of course deteriorate. Libev itself tries to be exact to be about one
2219	millisecond (if the OS supports it and the machine is fast enough).	2171	millisecond (if the OS supports it and the machine is fast enough).
…		…
2362	=head3 The special problem of inheritance over fork/execve/pthread_create	2314	=head3 The special problem of inheritance over fork/execve/pthread_create
2363		2315
2364	Both the signal mask (C<sigprocmask>) and the signal disposition	2316	Both the signal mask (C<sigprocmask>) and the signal disposition
2365	(C<sigaction>) are unspecified after starting a signal watcher (and after	2317	(C<sigaction>) are unspecified after starting a signal watcher (and after
2366	stopping it again), that is, libev might or might not block the signal,	2318	stopping it again), that is, libev might or might not block the signal,
2367	and might or might not set or restore the installed signal handler.	2319	and might or might not set or restore the installed signal handler (but
		2320	see C<EVFLAG_NOSIGMASK>).
2368		2321
2369	While this does not matter for the signal disposition (libev never	2322	While this does not matter for the signal disposition (libev never
2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2323	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2371	C<execve>), this matters for the signal mask: many programs do not expect	2324	C<execve>), this matters for the signal mask: many programs do not expect
2372	certain signals to be blocked.	2325	certain signals to be blocked.
…		…
3243	atexit (program_exits);	3196	atexit (program_exits);
3244		3197
3245		3198
3246	=head2 C<ev_async> - how to wake up an event loop	3199	=head2 C<ev_async> - how to wake up an event loop
3247		3200
3248	In general, you cannot use an C<ev_run> from multiple threads or other	3201	In general, you cannot use an C<ev_loop> from multiple threads or other
3249	asynchronous sources such as signal handlers (as opposed to multiple event	3202	asynchronous sources such as signal handlers (as opposed to multiple event
3250	loops - those are of course safe to use in different threads).	3203	loops - those are of course safe to use in different threads).
3251		3204
3252	Sometimes, however, you need to wake up an event loop you do not control,	3205	Sometimes, however, you need to wake up an event loop you do not control,
3253	for example because it belongs to another thread. This is what C<ev_async>	3206	for example because it belongs to another thread. This is what C<ev_async>
…		…
3363	trust me.	3316	trust me.
3364		3317
3365	=item ev_async_send (loop, ev_async *)	3318	=item ev_async_send (loop, ev_async *)
3366		3319
3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3320	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3321	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3322	returns.
		3323
3369	C<ev_feed_event>, this call is safe to do from other threads, signal or	3324	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3325	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3371	section below on what exactly this means).	3326	embedding section below on what exactly this means).
3372		3327
3373	Note that, as with other watchers in libev, multiple events might get	3328	Note that, as with other watchers in libev, multiple events might get
3374	compressed into a single callback invocation (another way to look at this	3329	compressed into a single callback invocation (another way to look at this
3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3330	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3376	reset when the event loop detects that).	3331	reset when the event loop detects that).
…		…
3456		3411
3457	This section explains some common idioms that are not immediately	3412	This section explains some common idioms that are not immediately
3458	obvious. Note that examples are sprinkled over the whole manual, and this	3413	obvious. Note that examples are sprinkled over the whole manual, and this
3459	section only contains stuff that wouldn't fit anywhere else.	3414	section only contains stuff that wouldn't fit anywhere else.
3460		3415
3461	=over 4	3416	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
3462		3417
3463	=item Model/nested event loop invocations and exit conditions.	3418	Each watcher has, by default, a C<void *data> member that you can read
		3419	or modify at any time: libev will completely ignore it. This can be used
		3420	to associate arbitrary data with your watcher. If you need more data and
		3421	don't want to allocate memory separately and store a pointer to it in that
		3422	data member, you can also "subclass" the watcher type and provide your own
		3423	data:
		3424
		3425	struct my_io
		3426	{
		3427	ev_io io;
		3428	int otherfd;
		3429	void *somedata;
		3430	struct whatever *mostinteresting;
		3431	};
		3432
		3433	...
		3434	struct my_io w;
		3435	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3436
		3437	And since your callback will be called with a pointer to the watcher, you
		3438	can cast it back to your own type:
		3439
		3440	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
		3441	{
		3442	struct my_io w = (struct my_io )w_;
		3443	...
		3444	}
		3445
		3446	More interesting and less C-conformant ways of casting your callback
		3447	function type instead have been omitted.
		3448
		3449	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3450
		3451	Another common scenario is to use some data structure with multiple
		3452	embedded watchers, in effect creating your own watcher that combines
		3453	multiple libev event sources into one "super-watcher":
		3454
		3455	struct my_biggy
		3456	{
		3457	int some_data;
		3458	ev_timer t1;
		3459	ev_timer t2;
		3460	}
		3461
		3462	In this case getting the pointer to C<my_biggy> is a bit more
		3463	complicated: Either you store the address of your C<my_biggy> struct in
		3464	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3465	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3466	real programmers):
		3467
		3468	#include <stddef.h>
		3469
		3470	static void
		3471	t1_cb (EV_P_ ev_timer *w, int revents)
		3472	{
		3473	struct my_biggy big = (struct my_biggy *)
		3474	(((char *)w) - offsetof (struct my_biggy, t1));
		3475	}
		3476
		3477	static void
		3478	t2_cb (EV_P_ ev_timer *w, int revents)
		3479	{
		3480	struct my_biggy big = (struct my_biggy *)
		3481	(((char *)w) - offsetof (struct my_biggy, t2));
		3482	}
		3483
		3484	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3464		3485
3465	Often (especially in GUI toolkits) there are places where you have	3486	Often (especially in GUI toolkits) there are places where you have
3466	I<modal> interaction, which is most easily implemented by recursively	3487	I<modal> interaction, which is most easily implemented by recursively
3467	invoking C<ev_run>.	3488	invoking C<ev_run>.
3468		3489
…		…
3497	exit_main_loop = 1;	3518	exit_main_loop = 1;
3498		3519
3499	// exit both	3520	// exit both
3500	exit_main_loop = exit_nested_loop = 1;	3521	exit_main_loop = exit_nested_loop = 1;
3501		3522
3502	=item Thread locking example	3523	=head2 THREAD LOCKING EXAMPLE
3503		3524
3504	Here is a fictitious example of how to run an event loop in a different	3525	Here is a fictitious example of how to run an event loop in a different
3505	thread than where callbacks are being invoked and watchers are	3526	thread from where callbacks are being invoked and watchers are
3506	created/added/removed.	3527	created/added/removed.
3507		3528
3508	For a real-world example, see the C<EV::Loop::Async> perl module,	3529	For a real-world example, see the C<EV::Loop::Async> perl module,
3509	which uses exactly this technique (which is suited for many high-level	3530	which uses exactly this technique (which is suited for many high-level
3510	languages).	3531	languages).
…		…
3536	// now associate this with the loop	3557	// now associate this with the loop
3537	ev_set_userdata (EV_A_ u);	3558	ev_set_userdata (EV_A_ u);
3538	ev_set_invoke_pending_cb (EV_A_ l_invoke);	3559	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3539	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);	3560	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3540		3561
3541	// then create the thread running ev_loop	3562	// then create the thread running ev_run
3542	pthread_create (&u->tid, 0, l_run, EV_A);	3563	pthread_create (&u->tid, 0, l_run, EV_A);
3543	}	3564	}
3544		3565
3545	The callback for the C<ev_async> watcher does nothing: the watcher is used	3566	The callback for the C<ev_async> watcher does nothing: the watcher is used
3546	solely to wake up the event loop so it takes notice of any new watchers	3567	solely to wake up the event loop so it takes notice of any new watchers
…		…
3635	Note that sending the C<ev_async> watcher is required because otherwise	3656	Note that sending the C<ev_async> watcher is required because otherwise
3636	an event loop currently blocking in the kernel will have no knowledge	3657	an event loop currently blocking in the kernel will have no knowledge
3637	about the newly added timer. By waking up the loop it will pick up any new	3658	about the newly added timer. By waking up the loop it will pick up any new
3638	watchers in the next event loop iteration.	3659	watchers in the next event loop iteration.
3639		3660
3640	=back	3661	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3662
		3663	While the overhead of a callback that e.g. schedules a thread is small, it
		3664	is still an overhead. If you embed libev, and your main usage is with some
		3665	kind of threads or coroutines, you might want to customise libev so that
		3666	doesn't need callbacks anymore.
		3667
		3668	Imagine you have coroutines that you can switch to using a function
		3669	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3670	and that due to some magic, the currently active coroutine is stored in a
		3671	global called C<current_coro>. Then you can build your own "wait for libev
		3672	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3673	the differing C<;> conventions):
		3674
		3675	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3676	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3677
		3678	That means instead of having a C callback function, you store the
		3679	coroutine to switch to in each watcher, and instead of having libev call
		3680	your callback, you instead have it switch to that coroutine.
		3681
		3682	A coroutine might now wait for an event with a function called
		3683	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3684	matter when, or whether the watcher is active or not when this function is
		3685	called):
		3686
		3687	void
		3688	wait_for_event (ev_watcher *w)
		3689	{
		3690	ev_cb_set (w) = current_coro;
		3691	switch_to (libev_coro);
		3692	}
		3693
		3694	That basically suspends the coroutine inside C<wait_for_event> and
		3695	continues the libev coroutine, which, when appropriate, switches back to
		3696	this or any other coroutine. I am sure if you sue this your own :)
		3697
		3698	You can do similar tricks if you have, say, threads with an event queue -
		3699	instead of storing a coroutine, you store the queue object and instead of
		3700	switching to a coroutine, you push the watcher onto the queue and notify
		3701	any waiters.
		3702
		3703	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3704	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3705
		3706	// my_ev.h
		3707	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3708	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3709	#include "../libev/ev.h"
		3710
		3711	// my_ev.c
		3712	#define EV_H "my_ev.h"
		3713	#include "../libev/ev.c"
		3714
		3715	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3716	F<my_ev.c> into your project. When properly specifying include paths, you
		3717	can even use F<ev.h> as header file name directly.
3641		3718
3642		3719
3643	=head1 LIBEVENT EMULATION	3720	=head1 LIBEVENT EMULATION
3644		3721
3645	Libev offers a compatibility emulation layer for libevent. It cannot	3722	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
4135	F<event.h> that are not directly supported by the libev core alone.	4212	F<event.h> that are not directly supported by the libev core alone.
4136		4213
4137	In standalone mode, libev will still try to automatically deduce the	4214	In standalone mode, libev will still try to automatically deduce the
4138	configuration, but has to be more conservative.	4215	configuration, but has to be more conservative.
4139		4216
		4217	=item EV_USE_FLOOR
		4218
		4219	If defined to be C<1>, libev will use the C<floor ()> function for its
		4220	periodic reschedule calculations, otherwise libev will fall back on a
		4221	portable (slower) implementation. If you enable this, you usually have to
		4222	link against libm or something equivalent. Enabling this when the C<floor>
		4223	function is not available will fail, so the safe default is to not enable
		4224	this.
		4225
4140	=item EV_USE_MONOTONIC	4226	=item EV_USE_MONOTONIC
4141		4227
4142	If defined to be C<1>, libev will try to detect the availability of the	4228	If defined to be C<1>, libev will try to detect the availability of the
4143	monotonic clock option at both compile time and runtime. Otherwise no	4229	monotonic clock option at both compile time and runtime. Otherwise no
4144	use of the monotonic clock option will be attempted. If you enable this,	4230	use of the monotonic clock option will be attempted. If you enable this,
…		…
4575	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4661	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4576		4662
4577	#include "ev_cpp.h"	4663	#include "ev_cpp.h"
4578	#include "ev.c"	4664	#include "ev.c"
4579		4665
4580	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4666	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4581		4667
4582	=head2 THREADS AND COROUTINES	4668	=head2 THREADS AND COROUTINES
4583		4669
4584	=head3 THREADS	4670	=head3 THREADS
4585		4671
…		…
4636	default loop and triggering an C<ev_async> watcher from the default loop	4722	default loop and triggering an C<ev_async> watcher from the default loop
4637	watcher callback into the event loop interested in the signal.	4723	watcher callback into the event loop interested in the signal.
4638		4724
4639	=back	4725	=back
4640		4726
4641	See also L<Thread locking example>.	4727	See also L<THREAD LOCKING EXAMPLE>.
4642		4728
4643	=head3 COROUTINES	4729	=head3 COROUTINES
4644		4730
4645	Libev is very accommodating to coroutines ("cooperative threads"):	4731	Libev is very accommodating to coroutines ("cooperative threads"):
4646	libev fully supports nesting calls to its functions from different	4732	libev fully supports nesting calls to its functions from different
…		…
5155	The physical time that is observed. It is apparently strictly monotonic :)	5241	The physical time that is observed. It is apparently strictly monotonic :)
5156		5242
5157	=item wall-clock time	5243	=item wall-clock time
5158		5244
5159	The time and date as shown on clocks. Unlike real time, it can actually	5245	The time and date as shown on clocks. Unlike real time, it can actually
5160	be wrong and jump forwards and backwards, e.g. when the you adjust your	5246	be wrong and jump forwards and backwards, e.g. when you adjust your
5161	clock.	5247	clock.
5162		5248
5163	=item watcher	5249	=item watcher
5164		5250
5165	A data structure that describes interest in certain events. Watchers need	5251	A data structure that describes interest in certain events. Watchers need
…		…
5168	=back	5254	=back
5169		5255
5170	=head1 AUTHOR	5256	=head1 AUTHOR
5171		5257
5172	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5258	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5173	Magnusson and Emanuele Giaquinta.	5259	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5174		5260

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Comparing libev/ev.pod (file contents): Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs. Revision 1.370 by root, Thu Jun 2 23:42:40 2011 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs.
Revision 1.370 by root, Thu Jun 2 23:42:40 2011 UTC