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4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 #include <ev.h> 7 #include <ev.h>
8 8
9=head1 EXAMPLE PROGRAM 9=head2 EXAMPLE PROGRAM
10 10
11 #include <ev.h> 11 #include <ev.h>
12 12
13 ev_io stdin_watcher; 13 ev_io stdin_watcher;
14 ev_timer timeout_watcher; 14 ev_timer timeout_watcher;
48 return 0; 48 return 0;
49 } 49 }
50 50
51=head1 DESCRIPTION 51=head1 DESCRIPTION
52 52
53The newest version of this document is also available as a html-formatted
54web page you might find easier to navigate when reading it for the first
55time: L<http://cvs.schmorp.de/libev/ev.html>.
56
53Libev is an event loop: you register interest in certain events (such as a 57Libev is an event loop: you register interest in certain events (such as a
54file descriptor being readable or a timeout occuring), and it will manage 58file descriptor being readable or a timeout occurring), and it will manage
55these event sources and provide your program with events. 59these event sources and provide your program with events.
56 60
57To do this, it must take more or less complete control over your process 61To do this, it must take more or less complete control over your process
58(or thread) by executing the I<event loop> handler, and will then 62(or thread) by executing the I<event loop> handler, and will then
59communicate events via a callback mechanism. 63communicate events via a callback mechanism.
61You register interest in certain events by registering so-called I<event 65You register interest in certain events by registering so-called I<event
62watchers>, which are relatively small C structures you initialise with the 66watchers>, which are relatively small C structures you initialise with the
63details of the event, and then hand it over to libev by I<starting> the 67details of the event, and then hand it over to libev by I<starting> the
64watcher. 68watcher.
65 69
66=head1 FEATURES 70=head2 FEATURES
67 71
68Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the 72Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69BSD-specific C<kqueue> and the Solaris-specific event port mechanisms 73BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70for file descriptor events (C<ev_io>), the Linux C<inotify> interface 74for file descriptor events (C<ev_io>), the Linux C<inotify> interface
71(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers 75(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
78 82
79It also is quite fast (see this 83It also is quite fast (see this
80L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent 84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
81for example). 85for example).
82 86
83=head1 CONVENTIONS 87=head2 CONVENTIONS
84 88
85Libev is very configurable. In this manual the default configuration will 89Libev is very configurable. In this manual the default configuration will
86be described, which supports multiple event loops. For more info about 90be described, which supports multiple event loops. For more info about
87various configuration options please have a look at B<EMBED> section in 91various configuration options please have a look at B<EMBED> section in
88this manual. If libev was configured without support for multiple event 92this manual. If libev was configured without support for multiple event
89loops, then all functions taking an initial argument of name C<loop> 93loops, then all functions taking an initial argument of name C<loop>
90(which is always of type C<struct ev_loop *>) will not have this argument. 94(which is always of type C<struct ev_loop *>) will not have this argument.
91 95
92=head1 TIME REPRESENTATION 96=head2 TIME REPRESENTATION
93 97
94Libev represents time as a single floating point number, representing the 98Libev represents time as a single floating point number, representing the
95(fractional) number of seconds since the (POSIX) epoch (somewhere near 99(fractional) number of seconds since the (POSIX) epoch (somewhere near
96the beginning of 1970, details are complicated, don't ask). This type is 100the beginning of 1970, details are complicated, don't ask). This type is
97called C<ev_tstamp>, which is what you should use too. It usually aliases 101called C<ev_tstamp>, which is what you should use too. It usually aliases
98to the C<double> type in C, and when you need to do any calculations on 102to the C<double> type in C, and when you need to do any calculations on
99it, you should treat it as such. 103it, you should treat it as some floatingpoint value. Unlike the name
104component C<stamp> might indicate, it is also used for time differences
105throughout libev.
100 106
101=head1 GLOBAL FUNCTIONS 107=head1 GLOBAL FUNCTIONS
102 108
103These functions can be called anytime, even before initialising the 109These functions can be called anytime, even before initialising the
104library in any way. 110library in any way.
109 115
110Returns the current time as libev would use it. Please note that the 116Returns the current time as libev would use it. Please note that the
111C<ev_now> function is usually faster and also often returns the timestamp 117C<ev_now> function is usually faster and also often returns the timestamp
112you actually want to know. 118you actually want to know.
113 119
120=item ev_sleep (ev_tstamp interval)
121
122Sleep for the given interval: The current thread will be blocked until
123either it is interrupted or the given time interval has passed. Basically
124this is a subsecond-resolution C<sleep ()>.
125
114=item int ev_version_major () 126=item int ev_version_major ()
115 127
116=item int ev_version_minor () 128=item int ev_version_minor ()
117 129
118You can find out the major and minor version numbers of the library 130You can find out the major and minor ABI version numbers of the library
119you linked against by calling the functions C<ev_version_major> and 131you linked against by calling the functions C<ev_version_major> and
120C<ev_version_minor>. If you want, you can compare against the global 132C<ev_version_minor>. If you want, you can compare against the global
121symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 133symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122version of the library your program was compiled against. 134version of the library your program was compiled against.
123 135
136These version numbers refer to the ABI version of the library, not the
137release version.
138
124Usually, it's a good idea to terminate if the major versions mismatch, 139Usually, it's a good idea to terminate if the major versions mismatch,
125as this indicates an incompatible change. Minor versions are usually 140as this indicates an incompatible change. Minor versions are usually
126compatible to older versions, so a larger minor version alone is usually 141compatible to older versions, so a larger minor version alone is usually
127not a problem. 142not a problem.
128 143
129Example: Make sure we haven't accidentally been linked against the wrong 144Example: Make sure we haven't accidentally been linked against the wrong
130version. 145version.
245flags. If that is troubling you, check C<ev_backend ()> afterwards). 260flags. If that is troubling you, check C<ev_backend ()> afterwards).
246 261
247If you don't know what event loop to use, use the one returned from this 262If you don't know what event loop to use, use the one returned from this
248function. 263function.
249 264
265The default loop is the only loop that can handle C<ev_signal> and
266C<ev_child> watchers, and to do this, it always registers a handler
267for C<SIGCHLD>. If this is a problem for your app you can either
268create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270C<ev_default_init>.
271
250The flags argument can be used to specify special behaviour or specific 272The flags argument can be used to specify special behaviour or specific
251backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). 273backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
252 274
253The following flags are supported: 275The following flags are supported:
254 276
274a fork, you can also make libev check for a fork in each iteration by 296a fork, you can also make libev check for a fork in each iteration by
275enabling this flag. 297enabling this flag.
276 298
277This works by calling C<getpid ()> on every iteration of the loop, 299This works by calling C<getpid ()> on every iteration of the loop,
278and thus this might slow down your event loop if you do a lot of loop 300and thus this might slow down your event loop if you do a lot of loop
279iterations and little real work, but is usually not noticable (on my 301iterations and little real work, but is usually not noticeable (on my
280Linux system for example, C<getpid> is actually a simple 5-insn sequence 302Linux system for example, C<getpid> is actually a simple 5-insn sequence
281without a syscall and thus I<very> fast, but my Linux system also has 303without a syscall and thus I<very> fast, but my Linux system also has
282C<pthread_atfork> which is even faster). 304C<pthread_atfork> which is even faster).
283 305
284The big advantage of this flag is that you can forget about fork (and 306The big advantage of this flag is that you can forget about fork (and
291=item C<EVBACKEND_SELECT> (value 1, portable select backend) 313=item C<EVBACKEND_SELECT> (value 1, portable select backend)
292 314
293This is your standard select(2) backend. Not I<completely> standard, as 315This is your standard select(2) backend. Not I<completely> standard, as
294libev tries to roll its own fd_set with no limits on the number of fds, 316libev tries to roll its own fd_set with no limits on the number of fds,
295but if that fails, expect a fairly low limit on the number of fds when 317but if that fails, expect a fairly low limit on the number of fds when
296using this backend. It doesn't scale too well (O(highest_fd)), but its usually 318using this backend. It doesn't scale too well (O(highest_fd)), but its
297the fastest backend for a low number of fds. 319usually the fastest backend for a low number of (low-numbered :) fds.
320
321To get good performance out of this backend you need a high amount of
322parallelity (most of the file descriptors should be busy). If you are
323writing a server, you should C<accept ()> in a loop to accept as many
324connections as possible during one iteration. You might also want to have
325a look at C<ev_set_io_collect_interval ()> to increase the amount of
326readyness notifications you get per iteration.
298 327
299=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) 328=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
300 329
301And this is your standard poll(2) backend. It's more complicated than 330And this is your standard poll(2) backend. It's more complicated
302select, but handles sparse fds better and has no artificial limit on the 331than select, but handles sparse fds better and has no artificial
303number of fds you can use (except it will slow down considerably with a 332limit on the number of fds you can use (except it will slow down
304lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 333considerably with a lot of inactive fds). It scales similarly to select,
334i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
335performance tips.
305 336
306=item C<EVBACKEND_EPOLL> (value 4, Linux) 337=item C<EVBACKEND_EPOLL> (value 4, Linux)
307 338
308For few fds, this backend is a bit little slower than poll and select, 339For few fds, this backend is a bit little slower than poll and select,
309but it scales phenomenally better. While poll and select usually scale like 340but it scales phenomenally better. While poll and select usually scale
310O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 341like O(total_fds) where n is the total number of fds (or the highest fd),
311either O(1) or O(active_fds). 342epoll scales either O(1) or O(active_fds). The epoll design has a number
343of shortcomings, such as silently dropping events in some hard-to-detect
344cases and rewiring a syscall per fd change, no fork support and bad
345support for dup.
312 346
313While stopping and starting an I/O watcher in the same iteration will 347While stopping, setting and starting an I/O watcher in the same iteration
314result in some caching, there is still a syscall per such incident 348will result in some caching, there is still a syscall per such incident
315(because the fd could point to a different file description now), so its 349(because the fd could point to a different file description now), so its
316best to avoid that. Also, dup()ed file descriptors might not work very 350best to avoid that. Also, C<dup ()>'ed file descriptors might not work
317well if you register events for both fds. 351very well if you register events for both fds.
318 352
319Please note that epoll sometimes generates spurious notifications, so you 353Please note that epoll sometimes generates spurious notifications, so you
320need to use non-blocking I/O or other means to avoid blocking when no data 354need to use non-blocking I/O or other means to avoid blocking when no data
321(or space) is available. 355(or space) is available.
322 356
357Best performance from this backend is achieved by not unregistering all
358watchers for a file descriptor until it has been closed, if possible, i.e.
359keep at least one watcher active per fd at all times.
360
361While nominally embeddeble in other event loops, this feature is broken in
362all kernel versions tested so far.
363
323=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 364=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324 365
325Kqueue deserves special mention, as at the time of this writing, it 366Kqueue deserves special mention, as at the time of this writing, it
326was broken on all BSDs except NetBSD (usually it doesn't work with 367was broken on all BSDs except NetBSD (usually it doesn't work reliably
327anything but sockets and pipes, except on Darwin, where of course its 368with anything but sockets and pipes, except on Darwin, where of course
328completely useless). For this reason its not being "autodetected" 369it's completely useless). For this reason it's not being "autodetected"
329unless you explicitly specify it explicitly in the flags (i.e. using 370unless you explicitly specify it explicitly in the flags (i.e. using
330C<EVBACKEND_KQUEUE>). 371C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
372system like NetBSD.
373
374You still can embed kqueue into a normal poll or select backend and use it
375only for sockets (after having made sure that sockets work with kqueue on
376the target platform). See C<ev_embed> watchers for more info.
331 377
332It scales in the same way as the epoll backend, but the interface to the 378It scales in the same way as the epoll backend, but the interface to the
333kernel is more efficient (which says nothing about its actual speed, of 379kernel is more efficient (which says nothing about its actual speed, of
334course). While starting and stopping an I/O watcher does not cause an 380course). While stopping, setting and starting an I/O watcher does never
335extra syscall as with epoll, it still adds up to four event changes per 381cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
336incident, so its best to avoid that. 382two event changes per incident, support for C<fork ()> is very bad and it
383drops fds silently in similarly hard-to-detect cases.
384
385This backend usually performs well under most conditions.
386
387While nominally embeddable in other event loops, this doesn't work
388everywhere, so you might need to test for this. And since it is broken
389almost everywhere, you should only use it when you have a lot of sockets
390(for which it usually works), by embedding it into another event loop
391(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
392sockets.
337 393
338=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) 394=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339 395
340This is not implemented yet (and might never be). 396This is not implemented yet (and might never be, unless you send me an
397implementation). According to reports, C</dev/poll> only supports sockets
398and is not embeddable, which would limit the usefulness of this backend
399immensely.
341 400
342=item C<EVBACKEND_PORT> (value 32, Solaris 10) 401=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343 402
344This uses the Solaris 10 port mechanism. As with everything on Solaris, 403This uses the Solaris 10 event port mechanism. As with everything on Solaris,
345it's really slow, but it still scales very well (O(active_fds)). 404it's really slow, but it still scales very well (O(active_fds)).
346 405
347Please note that solaris ports can result in a lot of spurious 406Please note that solaris event ports can deliver a lot of spurious
348notifications, so you need to use non-blocking I/O or other means to avoid 407notifications, so you need to use non-blocking I/O or other means to avoid
349blocking when no data (or space) is available. 408blocking when no data (or space) is available.
409
410While this backend scales well, it requires one system call per active
411file descriptor per loop iteration. For small and medium numbers of file
412descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413might perform better.
414
415On the positive side, ignoring the spurious readyness notifications, this
416backend actually performed to specification in all tests and is fully
417embeddable, which is a rare feat among the OS-specific backends.
350 418
351=item C<EVBACKEND_ALL> 419=item C<EVBACKEND_ALL>
352 420
353Try all backends (even potentially broken ones that wouldn't be tried 421Try all backends (even potentially broken ones that wouldn't be tried
354with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as 422with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
355C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 423C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
356 424
425It is definitely not recommended to use this flag.
426
357=back 427=back
358 428
359If one or more of these are ored into the flags value, then only these 429If one or more of these are ored into the flags value, then only these
360backends will be tried (in the reverse order as given here). If none are 430backends will be tried (in the reverse order as listed here). If none are
361specified, most compiled-in backend will be tried, usually in reverse 431specified, all backends in C<ev_recommended_backends ()> will be tried.
362order of their flag values :)
363 432
364The most typical usage is like this: 433The most typical usage is like this:
365 434
366 if (!ev_default_loop (0)) 435 if (!ev_default_loop (0))
367 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 436 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
395Destroys the default loop again (frees all memory and kernel state 464Destroys the default loop again (frees all memory and kernel state
396etc.). None of the active event watchers will be stopped in the normal 465etc.). None of the active event watchers will be stopped in the normal
397sense, so e.g. C<ev_is_active> might still return true. It is your 466sense, so e.g. C<ev_is_active> might still return true. It is your
398responsibility to either stop all watchers cleanly yoursef I<before> 467responsibility to either stop all watchers cleanly yoursef I<before>
399calling this function, or cope with the fact afterwards (which is usually 468calling this function, or cope with the fact afterwards (which is usually
400the easiest thing, youc na just ignore the watchers and/or C<free ()> them 469the easiest thing, you can just ignore the watchers and/or C<free ()> them
401for example). 470for example).
471
472Note that certain global state, such as signal state, will not be freed by
473this function, and related watchers (such as signal and child watchers)
474would need to be stopped manually.
475
476In general it is not advisable to call this function except in the
477rare occasion where you really need to free e.g. the signal handling
478pipe fds. If you need dynamically allocated loops it is better to use
479C<ev_loop_new> and C<ev_loop_destroy>).
402 480
403=item ev_loop_destroy (loop) 481=item ev_loop_destroy (loop)
404 482
405Like C<ev_default_destroy>, but destroys an event loop created by an 483Like C<ev_default_destroy>, but destroys an event loop created by an
406earlier call to C<ev_loop_new>. 484earlier call to C<ev_loop_new>.
407 485
408=item ev_default_fork () 486=item ev_default_fork ()
409 487
488This function sets a flag that causes subsequent C<ev_loop> iterations
410This function reinitialises the kernel state for backends that have 489to reinitialise the kernel state for backends that have one. Despite the
411one. Despite the name, you can call it anytime, but it makes most sense 490name, you can call it anytime, but it makes most sense after forking, in
412after forking, in either the parent or child process (or both, but that 491the child process (or both child and parent, but that again makes little
413again makes little sense). 492sense). You I<must> call it in the child before using any of the libev
493functions, and it will only take effect at the next C<ev_loop> iteration.
414 494
415You I<must> call this function in the child process after forking if and 495On the other hand, you only need to call this function in the child
416only if you want to use the event library in both processes. If you just 496process if and only if you want to use the event library in the child. If
417fork+exec, you don't have to call it. 497you just fork+exec, you don't have to call it at all.
418 498
419The function itself is quite fast and it's usually not a problem to call 499The function itself is quite fast and it's usually not a problem to call
420it just in case after a fork. To make this easy, the function will fit in 500it just in case after a fork. To make this easy, the function will fit in
421quite nicely into a call to C<pthread_atfork>: 501quite nicely into a call to C<pthread_atfork>:
422 502
423 pthread_atfork (0, 0, ev_default_fork); 503 pthread_atfork (0, 0, ev_default_fork);
424 504
425At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
426without calling this function, so if you force one of those backends you
427do not need to care.
428
429=item ev_loop_fork (loop) 505=item ev_loop_fork (loop)
430 506
431Like C<ev_default_fork>, but acts on an event loop created by 507Like C<ev_default_fork>, but acts on an event loop created by
432C<ev_loop_new>. Yes, you have to call this on every allocated event loop 508C<ev_loop_new>. Yes, you have to call this on every allocated event loop
433after fork, and how you do this is entirely your own problem. 509after fork, and how you do this is entirely your own problem.
510
511=item int ev_is_default_loop (loop)
512
513Returns true when the given loop actually is the default loop, false otherwise.
514
515=item unsigned int ev_loop_count (loop)
516
517Returns the count of loop iterations for the loop, which is identical to
518the number of times libev did poll for new events. It starts at C<0> and
519happily wraps around with enough iterations.
520
521This value can sometimes be useful as a generation counter of sorts (it
522"ticks" the number of loop iterations), as it roughly corresponds with
523C<ev_prepare> and C<ev_check> calls.
434 524
435=item unsigned int ev_backend (loop) 525=item unsigned int ev_backend (loop)
436 526
437Returns one of the C<EVBACKEND_*> flags indicating the event backend in 527Returns one of the C<EVBACKEND_*> flags indicating the event backend in
438use. 528use.
441 531
442Returns the current "event loop time", which is the time the event loop 532Returns the current "event loop time", which is the time the event loop
443received events and started processing them. This timestamp does not 533received events and started processing them. This timestamp does not
444change as long as callbacks are being processed, and this is also the base 534change as long as callbacks are being processed, and this is also the base
445time used for relative timers. You can treat it as the timestamp of the 535time used for relative timers. You can treat it as the timestamp of the
446event occuring (or more correctly, libev finding out about it). 536event occurring (or more correctly, libev finding out about it).
447 537
448=item ev_loop (loop, int flags) 538=item ev_loop (loop, int flags)
449 539
450Finally, this is it, the event handler. This function usually is called 540Finally, this is it, the event handler. This function usually is called
451after you initialised all your watchers and you want to start handling 541after you initialised all your watchers and you want to start handling
472libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is 562libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
473usually a better approach for this kind of thing. 563usually a better approach for this kind of thing.
474 564
475Here are the gory details of what C<ev_loop> does: 565Here are the gory details of what C<ev_loop> does:
476 566
477 * If there are no active watchers (reference count is zero), return. 567 - Before the first iteration, call any pending watchers.
478 - Queue prepare watchers and then call all outstanding watchers. 568 * If EVFLAG_FORKCHECK was used, check for a fork.
569 - If a fork was detected, queue and call all fork watchers.
570 - Queue and call all prepare watchers.
479 - If we have been forked, recreate the kernel state. 571 - If we have been forked, recreate the kernel state.
480 - Update the kernel state with all outstanding changes. 572 - Update the kernel state with all outstanding changes.
481 - Update the "event loop time". 573 - Update the "event loop time".
482 - Calculate for how long to block. 574 - Calculate for how long to sleep or block, if at all
575 (active idle watchers, EVLOOP_NONBLOCK or not having
576 any active watchers at all will result in not sleeping).
577 - Sleep if the I/O and timer collect interval say so.
483 - Block the process, waiting for any events. 578 - Block the process, waiting for any events.
484 - Queue all outstanding I/O (fd) events. 579 - Queue all outstanding I/O (fd) events.
485 - Update the "event loop time" and do time jump handling. 580 - Update the "event loop time" and do time jump handling.
486 - Queue all outstanding timers. 581 - Queue all outstanding timers.
487 - Queue all outstanding periodics. 582 - Queue all outstanding periodics.
488 - If no events are pending now, queue all idle watchers. 583 - If no events are pending now, queue all idle watchers.
489 - Queue all check watchers. 584 - Queue all check watchers.
490 - Call all queued watchers in reverse order (i.e. check watchers first). 585 - Call all queued watchers in reverse order (i.e. check watchers first).
491 Signals and child watchers are implemented as I/O watchers, and will 586 Signals and child watchers are implemented as I/O watchers, and will
492 be handled here by queueing them when their watcher gets executed. 587 be handled here by queueing them when their watcher gets executed.
493 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 588 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
494 were used, return, otherwise continue with step *. 589 were used, or there are no active watchers, return, otherwise
590 continue with step *.
495 591
496Example: Queue some jobs and then loop until no events are outsanding 592Example: Queue some jobs and then loop until no events are outstanding
497anymore. 593anymore.
498 594
499 ... queue jobs here, make sure they register event watchers as long 595 ... queue jobs here, make sure they register event watchers as long
500 ... as they still have work to do (even an idle watcher will do..) 596 ... as they still have work to do (even an idle watcher will do..)
501 ev_loop (my_loop, 0); 597 ev_loop (my_loop, 0);
505 601
506Can be used to make a call to C<ev_loop> return early (but only after it 602Can be used to make a call to C<ev_loop> return early (but only after it
507has processed all outstanding events). The C<how> argument must be either 603has processed all outstanding events). The C<how> argument must be either
508C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 604C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
509C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 605C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
606
607This "unloop state" will be cleared when entering C<ev_loop> again.
510 608
511=item ev_ref (loop) 609=item ev_ref (loop)
512 610
513=item ev_unref (loop) 611=item ev_unref (loop)
514 612
519returning, ev_unref() after starting, and ev_ref() before stopping it. For 617returning, ev_unref() after starting, and ev_ref() before stopping it. For
520example, libev itself uses this for its internal signal pipe: It is not 618example, libev itself uses this for its internal signal pipe: It is not
521visible to the libev user and should not keep C<ev_loop> from exiting if 619visible to the libev user and should not keep C<ev_loop> from exiting if
522no event watchers registered by it are active. It is also an excellent 620no event watchers registered by it are active. It is also an excellent
523way to do this for generic recurring timers or from within third-party 621way to do this for generic recurring timers or from within third-party
524libraries. Just remember to I<unref after start> and I<ref before stop>. 622libraries. Just remember to I<unref after start> and I<ref before stop>
623(but only if the watcher wasn't active before, or was active before,
624respectively).
525 625
526Example: Create a signal watcher, but keep it from keeping C<ev_loop> 626Example: Create a signal watcher, but keep it from keeping C<ev_loop>
527running when nothing else is active. 627running when nothing else is active.
528 628
529 struct ev_signal exitsig; 629 struct ev_signal exitsig;
533 633
534Example: For some weird reason, unregister the above signal handler again. 634Example: For some weird reason, unregister the above signal handler again.
535 635
536 ev_ref (loop); 636 ev_ref (loop);
537 ev_signal_stop (loop, &exitsig); 637 ev_signal_stop (loop, &exitsig);
638
639=item ev_set_io_collect_interval (loop, ev_tstamp interval)
640
641=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
642
643These advanced functions influence the time that libev will spend waiting
644for events. Both are by default C<0>, meaning that libev will try to
645invoke timer/periodic callbacks and I/O callbacks with minimum latency.
646
647Setting these to a higher value (the C<interval> I<must> be >= C<0>)
648allows libev to delay invocation of I/O and timer/periodic callbacks to
649increase efficiency of loop iterations.
650
651The background is that sometimes your program runs just fast enough to
652handle one (or very few) event(s) per loop iteration. While this makes
653the program responsive, it also wastes a lot of CPU time to poll for new
654events, especially with backends like C<select ()> which have a high
655overhead for the actual polling but can deliver many events at once.
656
657By setting a higher I<io collect interval> you allow libev to spend more
658time collecting I/O events, so you can handle more events per iteration,
659at the cost of increasing latency. Timeouts (both C<ev_periodic> and
660C<ev_timer>) will be not affected. Setting this to a non-null value will
661introduce an additional C<ev_sleep ()> call into most loop iterations.
662
663Likewise, by setting a higher I<timeout collect interval> you allow libev
664to spend more time collecting timeouts, at the expense of increased
665latency (the watcher callback will be called later). C<ev_io> watchers
666will not be affected. Setting this to a non-null value will not introduce
667any overhead in libev.
668
669Many (busy) programs can usually benefit by setting the io collect
670interval to a value near C<0.1> or so, which is often enough for
671interactive servers (of course not for games), likewise for timeouts. It
672usually doesn't make much sense to set it to a lower value than C<0.01>,
673as this approsaches the timing granularity of most systems.
538 674
539=back 675=back
540 676
541 677
542=head1 ANATOMY OF A WATCHER 678=head1 ANATOMY OF A WATCHER
642=item C<EV_FORK> 778=item C<EV_FORK>
643 779
644The event loop has been resumed in the child process after fork (see 780The event loop has been resumed in the child process after fork (see
645C<ev_fork>). 781C<ev_fork>).
646 782
783=item C<EV_ASYNC>
784
785The given async watcher has been asynchronously notified (see C<ev_async>).
786
647=item C<EV_ERROR> 787=item C<EV_ERROR>
648 788
649An unspecified error has occured, the watcher has been stopped. This might 789An unspecified error has occured, the watcher has been stopped. This might
650happen because the watcher could not be properly started because libev 790happen because the watcher could not be properly started because libev
651ran out of memory, a file descriptor was found to be closed or any other 791ran out of memory, a file descriptor was found to be closed or any other
722=item bool ev_is_pending (ev_TYPE *watcher) 862=item bool ev_is_pending (ev_TYPE *watcher)
723 863
724Returns a true value iff the watcher is pending, (i.e. it has outstanding 864Returns a true value iff the watcher is pending, (i.e. it has outstanding
725events but its callback has not yet been invoked). As long as a watcher 865events but its callback has not yet been invoked). As long as a watcher
726is pending (but not active) you must not call an init function on it (but 866is pending (but not active) you must not call an init function on it (but
727C<ev_TYPE_set> is safe) and you must make sure the watcher is available to 867C<ev_TYPE_set> is safe), you must not change its priority, and you must
728libev (e.g. you cnanot C<free ()> it). 868make sure the watcher is available to libev (e.g. you cannot C<free ()>
869it).
729 870
730=item callback ev_cb (ev_TYPE *watcher) 871=item callback ev_cb (ev_TYPE *watcher)
731 872
732Returns the callback currently set on the watcher. 873Returns the callback currently set on the watcher.
733 874
734=item ev_cb_set (ev_TYPE *watcher, callback) 875=item ev_cb_set (ev_TYPE *watcher, callback)
735 876
736Change the callback. You can change the callback at virtually any time 877Change the callback. You can change the callback at virtually any time
737(modulo threads). 878(modulo threads).
879
880=item ev_set_priority (ev_TYPE *watcher, priority)
881
882=item int ev_priority (ev_TYPE *watcher)
883
884Set and query the priority of the watcher. The priority is a small
885integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
886(default: C<-2>). Pending watchers with higher priority will be invoked
887before watchers with lower priority, but priority will not keep watchers
888from being executed (except for C<ev_idle> watchers).
889
890This means that priorities are I<only> used for ordering callback
891invocation after new events have been received. This is useful, for
892example, to reduce latency after idling, or more often, to bind two
893watchers on the same event and make sure one is called first.
894
895If you need to suppress invocation when higher priority events are pending
896you need to look at C<ev_idle> watchers, which provide this functionality.
897
898You I<must not> change the priority of a watcher as long as it is active or
899pending.
900
901The default priority used by watchers when no priority has been set is
902always C<0>, which is supposed to not be too high and not be too low :).
903
904Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
905fine, as long as you do not mind that the priority value you query might
906or might not have been adjusted to be within valid range.
907
908=item ev_invoke (loop, ev_TYPE *watcher, int revents)
909
910Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
911C<loop> nor C<revents> need to be valid as long as the watcher callback
912can deal with that fact.
913
914=item int ev_clear_pending (loop, ev_TYPE *watcher)
915
916If the watcher is pending, this function returns clears its pending status
917and returns its C<revents> bitset (as if its callback was invoked). If the
918watcher isn't pending it does nothing and returns C<0>.
738 919
739=back 920=back
740 921
741 922
742=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 923=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
827In general you can register as many read and/or write event watchers per 1008In general you can register as many read and/or write event watchers per
828fd as you want (as long as you don't confuse yourself). Setting all file 1009fd as you want (as long as you don't confuse yourself). Setting all file
829descriptors to non-blocking mode is also usually a good idea (but not 1010descriptors to non-blocking mode is also usually a good idea (but not
830required if you know what you are doing). 1011required if you know what you are doing).
831 1012
832You have to be careful with dup'ed file descriptors, though. Some backends
833(the linux epoll backend is a notable example) cannot handle dup'ed file
834descriptors correctly if you register interest in two or more fds pointing
835to the same underlying file/socket/etc. description (that is, they share
836the same underlying "file open").
837
838If you must do this, then force the use of a known-to-be-good backend 1013If you must do this, then force the use of a known-to-be-good backend
839(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1014(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
840C<EVBACKEND_POLL>). 1015C<EVBACKEND_POLL>).
841 1016
842Another thing you have to watch out for is that it is quite easy to 1017Another thing you have to watch out for is that it is quite easy to
848it is best to always use non-blocking I/O: An extra C<read>(2) returning 1023it is best to always use non-blocking I/O: An extra C<read>(2) returning
849C<EAGAIN> is far preferable to a program hanging until some data arrives. 1024C<EAGAIN> is far preferable to a program hanging until some data arrives.
850 1025
851If you cannot run the fd in non-blocking mode (for example you should not 1026If you cannot run the fd in non-blocking mode (for example you should not
852play around with an Xlib connection), then you have to seperately re-test 1027play around with an Xlib connection), then you have to seperately re-test
853wether a file descriptor is really ready with a known-to-be good interface 1028whether a file descriptor is really ready with a known-to-be good interface
854such as poll (fortunately in our Xlib example, Xlib already does this on 1029such as poll (fortunately in our Xlib example, Xlib already does this on
855its own, so its quite safe to use). 1030its own, so its quite safe to use).
1031
1032=head3 The special problem of disappearing file descriptors
1033
1034Some backends (e.g. kqueue, epoll) need to be told about closing a file
1035descriptor (either by calling C<close> explicitly or by any other means,
1036such as C<dup>). The reason is that you register interest in some file
1037descriptor, but when it goes away, the operating system will silently drop
1038this interest. If another file descriptor with the same number then is
1039registered with libev, there is no efficient way to see that this is, in
1040fact, a different file descriptor.
1041
1042To avoid having to explicitly tell libev about such cases, libev follows
1043the following policy: Each time C<ev_io_set> is being called, libev
1044will assume that this is potentially a new file descriptor, otherwise
1045it is assumed that the file descriptor stays the same. That means that
1046you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
1047descriptor even if the file descriptor number itself did not change.
1048
1049This is how one would do it normally anyway, the important point is that
1050the libev application should not optimise around libev but should leave
1051optimisations to libev.
1052
1053=head3 The special problem of dup'ed file descriptors
1054
1055Some backends (e.g. epoll), cannot register events for file descriptors,
1056but only events for the underlying file descriptions. That means when you
1057have C<dup ()>'ed file descriptors or weirder constellations, and register
1058events for them, only one file descriptor might actually receive events.
1059
1060There is no workaround possible except not registering events
1061for potentially C<dup ()>'ed file descriptors, or to resort to
1062C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1063
1064=head3 The special problem of fork
1065
1066Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1067useless behaviour. Libev fully supports fork, but needs to be told about
1068it in the child.
1069
1070To support fork in your programs, you either have to call
1071C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1072enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1073C<EVBACKEND_POLL>.
1074
1075
1076=head3 Watcher-Specific Functions
856 1077
857=over 4 1078=over 4
858 1079
859=item ev_io_init (ev_io *, callback, int fd, int events) 1080=item ev_io_init (ev_io *, callback, int fd, int events)
860 1081
871=item int events [read-only] 1092=item int events [read-only]
872 1093
873The events being watched. 1094The events being watched.
874 1095
875=back 1096=back
1097
1098=head3 Examples
876 1099
877Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1100Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
878readable, but only once. Since it is likely line-buffered, you could 1101readable, but only once. Since it is likely line-buffered, you could
879attempt to read a whole line in the callback. 1102attempt to read a whole line in the callback.
880 1103
914 1137
915The callback is guarenteed to be invoked only when its timeout has passed, 1138The callback is guarenteed to be invoked only when its timeout has passed,
916but if multiple timers become ready during the same loop iteration then 1139but if multiple timers become ready during the same loop iteration then
917order of execution is undefined. 1140order of execution is undefined.
918 1141
1142=head3 Watcher-Specific Functions and Data Members
1143
919=over 4 1144=over 4
920 1145
921=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1146=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
922 1147
923=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) 1148=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
931configure a timer to trigger every 10 seconds, then it will trigger at 1156configure a timer to trigger every 10 seconds, then it will trigger at
932exactly 10 second intervals. If, however, your program cannot keep up with 1157exactly 10 second intervals. If, however, your program cannot keep up with
933the timer (because it takes longer than those 10 seconds to do stuff) the 1158the timer (because it takes longer than those 10 seconds to do stuff) the
934timer will not fire more than once per event loop iteration. 1159timer will not fire more than once per event loop iteration.
935 1160
936=item ev_timer_again (loop) 1161=item ev_timer_again (loop, ev_timer *)
937 1162
938This will act as if the timer timed out and restart it again if it is 1163This will act as if the timer timed out and restart it again if it is
939repeating. The exact semantics are: 1164repeating. The exact semantics are:
940 1165
941If the timer is pending, its pending status is cleared. 1166If the timer is pending, its pending status is cleared.
976or C<ev_timer_again> is called and determines the next timeout (if any), 1201or C<ev_timer_again> is called and determines the next timeout (if any),
977which is also when any modifications are taken into account. 1202which is also when any modifications are taken into account.
978 1203
979=back 1204=back
980 1205
1206=head3 Examples
1207
981Example: Create a timer that fires after 60 seconds. 1208Example: Create a timer that fires after 60 seconds.
982 1209
983 static void 1210 static void
984 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1211 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
985 { 1212 {
1018but on wallclock time (absolute time). You can tell a periodic watcher 1245but on wallclock time (absolute time). You can tell a periodic watcher
1019to trigger "at" some specific point in time. For example, if you tell a 1246to trigger "at" some specific point in time. For example, if you tell a
1020periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () 1247periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1021+ 10.>) and then reset your system clock to the last year, then it will 1248+ 10.>) and then reset your system clock to the last year, then it will
1022take a year to trigger the event (unlike an C<ev_timer>, which would trigger 1249take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1023roughly 10 seconds later and of course not if you reset your system time 1250roughly 10 seconds later).
1024again).
1025 1251
1026They can also be used to implement vastly more complex timers, such as 1252They can also be used to implement vastly more complex timers, such as
1027triggering an event on eahc midnight, local time. 1253triggering an event on each midnight, local time or other, complicated,
1254rules.
1028 1255
1029As with timers, the callback is guarenteed to be invoked only when the 1256As with timers, the callback is guarenteed to be invoked only when the
1030time (C<at>) has been passed, but if multiple periodic timers become ready 1257time (C<at>) has been passed, but if multiple periodic timers become ready
1031during the same loop iteration then order of execution is undefined. 1258during the same loop iteration then order of execution is undefined.
1032 1259
1260=head3 Watcher-Specific Functions and Data Members
1261
1033=over 4 1262=over 4
1034 1263
1035=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) 1264=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1036 1265
1037=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) 1266=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1039Lots of arguments, lets sort it out... There are basically three modes of 1268Lots of arguments, lets sort it out... There are basically three modes of
1040operation, and we will explain them from simplest to complex: 1269operation, and we will explain them from simplest to complex:
1041 1270
1042=over 4 1271=over 4
1043 1272
1044=item * absolute timer (interval = reschedule_cb = 0) 1273=item * absolute timer (at = time, interval = reschedule_cb = 0)
1045 1274
1046In this configuration the watcher triggers an event at the wallclock time 1275In this configuration the watcher triggers an event at the wallclock time
1047C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1276C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1048that is, if it is to be run at January 1st 2011 then it will run when the 1277that is, if it is to be run at January 1st 2011 then it will run when the
1049system time reaches or surpasses this time. 1278system time reaches or surpasses this time.
1050 1279
1051=item * non-repeating interval timer (interval > 0, reschedule_cb = 0) 1280=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1052 1281
1053In this mode the watcher will always be scheduled to time out at the next 1282In this mode the watcher will always be scheduled to time out at the next
1054C<at + N * interval> time (for some integer N) and then repeat, regardless 1283C<at + N * interval> time (for some integer N, which can also be negative)
1055of any time jumps. 1284and then repeat, regardless of any time jumps.
1056 1285
1057This can be used to create timers that do not drift with respect to system 1286This can be used to create timers that do not drift with respect to system
1058time: 1287time:
1059 1288
1060 ev_periodic_set (&periodic, 0., 3600., 0); 1289 ev_periodic_set (&periodic, 0., 3600., 0);
1066 1295
1067Another way to think about it (for the mathematically inclined) is that 1296Another way to think about it (for the mathematically inclined) is that
1068C<ev_periodic> will try to run the callback in this mode at the next possible 1297C<ev_periodic> will try to run the callback in this mode at the next possible
1069time where C<time = at (mod interval)>, regardless of any time jumps. 1298time where C<time = at (mod interval)>, regardless of any time jumps.
1070 1299
1300For numerical stability it is preferable that the C<at> value is near
1301C<ev_now ()> (the current time), but there is no range requirement for
1302this value.
1303
1071=item * manual reschedule mode (reschedule_cb = callback) 1304=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1072 1305
1073In this mode the values for C<interval> and C<at> are both being 1306In this mode the values for C<interval> and C<at> are both being
1074ignored. Instead, each time the periodic watcher gets scheduled, the 1307ignored. Instead, each time the periodic watcher gets scheduled, the
1075reschedule callback will be called with the watcher as first, and the 1308reschedule callback will be called with the watcher as first, and the
1076current time as second argument. 1309current time as second argument.
1077 1310
1078NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, 1311NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1079ever, or make any event loop modifications>. If you need to stop it, 1312ever, or make any event loop modifications>. If you need to stop it,
1080return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by 1313return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1081starting a prepare watcher). 1314starting an C<ev_prepare> watcher, which is legal).
1082 1315
1083Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1316Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1084ev_tstamp now)>, e.g.: 1317ev_tstamp now)>, e.g.:
1085 1318
1086 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1319 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1109Simply stops and restarts the periodic watcher again. This is only useful 1342Simply stops and restarts the periodic watcher again. This is only useful
1110when you changed some parameters or the reschedule callback would return 1343when you changed some parameters or the reschedule callback would return
1111a different time than the last time it was called (e.g. in a crond like 1344a different time than the last time it was called (e.g. in a crond like
1112program when the crontabs have changed). 1345program when the crontabs have changed).
1113 1346
1347=item ev_tstamp offset [read-write]
1348
1349When repeating, this contains the offset value, otherwise this is the
1350absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1351
1352Can be modified any time, but changes only take effect when the periodic
1353timer fires or C<ev_periodic_again> is being called.
1354
1114=item ev_tstamp interval [read-write] 1355=item ev_tstamp interval [read-write]
1115 1356
1116The current interval value. Can be modified any time, but changes only 1357The current interval value. Can be modified any time, but changes only
1117take effect when the periodic timer fires or C<ev_periodic_again> is being 1358take effect when the periodic timer fires or C<ev_periodic_again> is being
1118called. 1359called.
1121 1362
1122The current reschedule callback, or C<0>, if this functionality is 1363The current reschedule callback, or C<0>, if this functionality is
1123switched off. Can be changed any time, but changes only take effect when 1364switched off. Can be changed any time, but changes only take effect when
1124the periodic timer fires or C<ev_periodic_again> is being called. 1365the periodic timer fires or C<ev_periodic_again> is being called.
1125 1366
1367=item ev_tstamp at [read-only]
1368
1369When active, contains the absolute time that the watcher is supposed to
1370trigger next.
1371
1126=back 1372=back
1373
1374=head3 Examples
1127 1375
1128Example: Call a callback every hour, or, more precisely, whenever the 1376Example: Call a callback every hour, or, more precisely, whenever the
1129system clock is divisible by 3600. The callback invocation times have 1377system clock is divisible by 3600. The callback invocation times have
1130potentially a lot of jittering, but good long-term stability. 1378potentially a lot of jittering, but good long-term stability.
1131 1379
1171with the kernel (thus it coexists with your own signal handlers as long 1419with the kernel (thus it coexists with your own signal handlers as long
1172as you don't register any with libev). Similarly, when the last signal 1420as you don't register any with libev). Similarly, when the last signal
1173watcher for a signal is stopped libev will reset the signal handler to 1421watcher for a signal is stopped libev will reset the signal handler to
1174SIG_DFL (regardless of what it was set to before). 1422SIG_DFL (regardless of what it was set to before).
1175 1423
1424=head3 Watcher-Specific Functions and Data Members
1425
1176=over 4 1426=over 4
1177 1427
1178=item ev_signal_init (ev_signal *, callback, int signum) 1428=item ev_signal_init (ev_signal *, callback, int signum)
1179 1429
1180=item ev_signal_set (ev_signal *, int signum) 1430=item ev_signal_set (ev_signal *, int signum)
1186 1436
1187The signal the watcher watches out for. 1437The signal the watcher watches out for.
1188 1438
1189=back 1439=back
1190 1440
1441=head3 Examples
1442
1443Example: Try to exit cleanly on SIGINT and SIGTERM.
1444
1445 static void
1446 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1447 {
1448 ev_unloop (loop, EVUNLOOP_ALL);
1449 }
1450
1451 struct ev_signal signal_watcher;
1452 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1453 ev_signal_start (loop, &sigint_cb);
1454
1191 1455
1192=head2 C<ev_child> - watch out for process status changes 1456=head2 C<ev_child> - watch out for process status changes
1193 1457
1194Child watchers trigger when your process receives a SIGCHLD in response to 1458Child watchers trigger when your process receives a SIGCHLD in response to
1195some child status changes (most typically when a child of yours dies). 1459some child status changes (most typically when a child of yours dies).
1196 1460
1461=head3 Watcher-Specific Functions and Data Members
1462
1197=over 4 1463=over 4
1198 1464
1199=item ev_child_init (ev_child *, callback, int pid) 1465=item ev_child_init (ev_child *, callback, int pid, int trace)
1200 1466
1201=item ev_child_set (ev_child *, int pid) 1467=item ev_child_set (ev_child *, int pid, int trace)
1202 1468
1203Configures the watcher to wait for status changes of process C<pid> (or 1469Configures the watcher to wait for status changes of process C<pid> (or
1204I<any> process if C<pid> is specified as C<0>). The callback can look 1470I<any> process if C<pid> is specified as C<0>). The callback can look
1205at the C<rstatus> member of the C<ev_child> watcher structure to see 1471at the C<rstatus> member of the C<ev_child> watcher structure to see
1206the status word (use the macros from C<sys/wait.h> and see your systems 1472the status word (use the macros from C<sys/wait.h> and see your systems
1207C<waitpid> documentation). The C<rpid> member contains the pid of the 1473C<waitpid> documentation). The C<rpid> member contains the pid of the
1208process causing the status change. 1474process causing the status change. C<trace> must be either C<0> (only
1475activate the watcher when the process terminates) or C<1> (additionally
1476activate the watcher when the process is stopped or continued).
1209 1477
1210=item int pid [read-only] 1478=item int pid [read-only]
1211 1479
1212The process id this watcher watches out for, or C<0>, meaning any process id. 1480The process id this watcher watches out for, or C<0>, meaning any process id.
1213 1481
1219 1487
1220The process exit/trace status caused by C<rpid> (see your systems 1488The process exit/trace status caused by C<rpid> (see your systems
1221C<waitpid> and C<sys/wait.h> documentation for details). 1489C<waitpid> and C<sys/wait.h> documentation for details).
1222 1490
1223=back 1491=back
1224
1225Example: Try to exit cleanly on SIGINT and SIGTERM.
1226
1227 static void
1228 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1229 {
1230 ev_unloop (loop, EVUNLOOP_ALL);
1231 }
1232
1233 struct ev_signal signal_watcher;
1234 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1235 ev_signal_start (loop, &sigint_cb);
1236 1492
1237 1493
1238=head2 C<ev_stat> - did the file attributes just change? 1494=head2 C<ev_stat> - did the file attributes just change?
1239 1495
1240This watches a filesystem path for attribute changes. That is, it calls 1496This watches a filesystem path for attribute changes. That is, it calls
1269semantics of C<ev_stat> watchers, which means that libev sometimes needs 1525semantics of C<ev_stat> watchers, which means that libev sometimes needs
1270to fall back to regular polling again even with inotify, but changes are 1526to fall back to regular polling again even with inotify, but changes are
1271usually detected immediately, and if the file exists there will be no 1527usually detected immediately, and if the file exists there will be no
1272polling. 1528polling.
1273 1529
1530=head3 Inotify
1531
1532When C<inotify (7)> support has been compiled into libev (generally only
1533available on Linux) and present at runtime, it will be used to speed up
1534change detection where possible. The inotify descriptor will be created lazily
1535when the first C<ev_stat> watcher is being started.
1536
1537Inotify presense does not change the semantics of C<ev_stat> watchers
1538except that changes might be detected earlier, and in some cases, to avoid
1539making regular C<stat> calls. Even in the presense of inotify support
1540there are many cases where libev has to resort to regular C<stat> polling.
1541
1542(There is no support for kqueue, as apparently it cannot be used to
1543implement this functionality, due to the requirement of having a file
1544descriptor open on the object at all times).
1545
1546=head3 The special problem of stat time resolution
1547
1548The C<stat ()> syscall only supports full-second resolution portably, and
1549even on systems where the resolution is higher, many filesystems still
1550only support whole seconds.
1551
1552That means that, if the time is the only thing that changes, you might
1553miss updates: on the first update, C<ev_stat> detects a change and calls
1554your callback, which does something. When there is another update within
1555the same second, C<ev_stat> will be unable to detect it.
1556
1557The solution to this is to delay acting on a change for a second (or till
1558the next second boundary), using a roughly one-second delay C<ev_timer>
1559(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1560is added to work around small timing inconsistencies of some operating
1561systems.
1562
1563=head3 Watcher-Specific Functions and Data Members
1564
1274=over 4 1565=over 4
1275 1566
1276=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1567=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1277 1568
1278=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) 1569=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
1285 1576
1286The callback will be receive C<EV_STAT> when a change was detected, 1577The callback will be receive C<EV_STAT> when a change was detected,
1287relative to the attributes at the time the watcher was started (or the 1578relative to the attributes at the time the watcher was started (or the
1288last change was detected). 1579last change was detected).
1289 1580
1290=item ev_stat_stat (ev_stat *) 1581=item ev_stat_stat (loop, ev_stat *)
1291 1582
1292Updates the stat buffer immediately with new values. If you change the 1583Updates the stat buffer immediately with new values. If you change the
1293watched path in your callback, you could call this fucntion to avoid 1584watched path in your callback, you could call this fucntion to avoid
1294detecting this change (while introducing a race condition). Can also be 1585detecting this change (while introducing a race condition). Can also be
1295useful simply to find out the new values. 1586useful simply to find out the new values.
1313=item const char *path [read-only] 1604=item const char *path [read-only]
1314 1605
1315The filesystem path that is being watched. 1606The filesystem path that is being watched.
1316 1607
1317=back 1608=back
1609
1610=head3 Examples
1318 1611
1319Example: Watch C</etc/passwd> for attribute changes. 1612Example: Watch C</etc/passwd> for attribute changes.
1320 1613
1321 static void 1614 static void
1322 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1615 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1335 } 1628 }
1336 1629
1337 ... 1630 ...
1338 ev_stat passwd; 1631 ev_stat passwd;
1339 1632
1340 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1633 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1341 ev_stat_start (loop, &passwd); 1634 ev_stat_start (loop, &passwd);
1342 1635
1636Example: Like above, but additionally use a one-second delay so we do not
1637miss updates (however, frequent updates will delay processing, too, so
1638one might do the work both on C<ev_stat> callback invocation I<and> on
1639C<ev_timer> callback invocation).
1640
1641 static ev_stat passwd;
1642 static ev_timer timer;
1643
1644 static void
1645 timer_cb (EV_P_ ev_timer *w, int revents)
1646 {
1647 ev_timer_stop (EV_A_ w);
1648
1649 /* now it's one second after the most recent passwd change */
1650 }
1651
1652 static void
1653 stat_cb (EV_P_ ev_stat *w, int revents)
1654 {
1655 /* reset the one-second timer */
1656 ev_timer_again (EV_A_ &timer);
1657 }
1658
1659 ...
1660 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1661 ev_stat_start (loop, &passwd);
1662 ev_timer_init (&timer, timer_cb, 0., 1.01);
1663
1343 1664
1344=head2 C<ev_idle> - when you've got nothing better to do... 1665=head2 C<ev_idle> - when you've got nothing better to do...
1345 1666
1346Idle watchers trigger events when there are no other events are pending 1667Idle watchers trigger events when no other events of the same or higher
1347(prepare, check and other idle watchers do not count). That is, as long 1668priority are pending (prepare, check and other idle watchers do not
1348as your process is busy handling sockets or timeouts (or even signals, 1669count).
1349imagine) it will not be triggered. But when your process is idle all idle 1670
1350watchers are being called again and again, once per event loop iteration - 1671That is, as long as your process is busy handling sockets or timeouts
1672(or even signals, imagine) of the same or higher priority it will not be
1673triggered. But when your process is idle (or only lower-priority watchers
1674are pending), the idle watchers are being called once per event loop
1351until stopped, that is, or your process receives more events and becomes 1675iteration - until stopped, that is, or your process receives more events
1352busy. 1676and becomes busy again with higher priority stuff.
1353 1677
1354The most noteworthy effect is that as long as any idle watchers are 1678The most noteworthy effect is that as long as any idle watchers are
1355active, the process will not block when waiting for new events. 1679active, the process will not block when waiting for new events.
1356 1680
1357Apart from keeping your process non-blocking (which is a useful 1681Apart from keeping your process non-blocking (which is a useful
1358effect on its own sometimes), idle watchers are a good place to do 1682effect on its own sometimes), idle watchers are a good place to do
1359"pseudo-background processing", or delay processing stuff to after the 1683"pseudo-background processing", or delay processing stuff to after the
1360event loop has handled all outstanding events. 1684event loop has handled all outstanding events.
1361 1685
1686=head3 Watcher-Specific Functions and Data Members
1687
1362=over 4 1688=over 4
1363 1689
1364=item ev_idle_init (ev_signal *, callback) 1690=item ev_idle_init (ev_signal *, callback)
1365 1691
1366Initialises and configures the idle watcher - it has no parameters of any 1692Initialises and configures the idle watcher - it has no parameters of any
1367kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1693kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1368believe me. 1694believe me.
1369 1695
1370=back 1696=back
1697
1698=head3 Examples
1371 1699
1372Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1700Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1373callback, free it. Also, use no error checking, as usual. 1701callback, free it. Also, use no error checking, as usual.
1374 1702
1375 static void 1703 static void
1376 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1704 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1377 { 1705 {
1378 free (w); 1706 free (w);
1379 // now do something you wanted to do when the program has 1707 // now do something you wanted to do when the program has
1380 // no longer asnything immediate to do. 1708 // no longer anything immediate to do.
1381 } 1709 }
1382 1710
1383 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1711 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1384 ev_idle_init (idle_watcher, idle_cb); 1712 ev_idle_init (idle_watcher, idle_cb);
1385 ev_idle_start (loop, idle_cb); 1713 ev_idle_start (loop, idle_cb);
1423with priority higher than or equal to the event loop and one coroutine 1751with priority higher than or equal to the event loop and one coroutine
1424of lower priority, but only once, using idle watchers to keep the event 1752of lower priority, but only once, using idle watchers to keep the event
1425loop from blocking if lower-priority coroutines are active, thus mapping 1753loop from blocking if lower-priority coroutines are active, thus mapping
1426low-priority coroutines to idle/background tasks). 1754low-priority coroutines to idle/background tasks).
1427 1755
1756It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1757priority, to ensure that they are being run before any other watchers
1758after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1759too) should not activate ("feed") events into libev. While libev fully
1760supports this, they will be called before other C<ev_check> watchers
1761did their job. As C<ev_check> watchers are often used to embed other
1762(non-libev) event loops those other event loops might be in an unusable
1763state until their C<ev_check> watcher ran (always remind yourself to
1764coexist peacefully with others).
1765
1766=head3 Watcher-Specific Functions and Data Members
1767
1428=over 4 1768=over 4
1429 1769
1430=item ev_prepare_init (ev_prepare *, callback) 1770=item ev_prepare_init (ev_prepare *, callback)
1431 1771
1432=item ev_check_init (ev_check *, callback) 1772=item ev_check_init (ev_check *, callback)
1435parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1775parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1436macros, but using them is utterly, utterly and completely pointless. 1776macros, but using them is utterly, utterly and completely pointless.
1437 1777
1438=back 1778=back
1439 1779
1440Example: To include a library such as adns, you would add IO watchers 1780=head3 Examples
1441and a timeout watcher in a prepare handler, as required by libadns, and 1781
1782There are a number of principal ways to embed other event loops or modules
1783into libev. Here are some ideas on how to include libadns into libev
1784(there is a Perl module named C<EV::ADNS> that does this, which you could
1785use for an actually working example. Another Perl module named C<EV::Glib>
1786embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
1787into the Glib event loop).
1788
1789Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1442in a check watcher, destroy them and call into libadns. What follows is 1790and in a check watcher, destroy them and call into libadns. What follows
1443pseudo-code only of course: 1791is pseudo-code only of course. This requires you to either use a low
1792priority for the check watcher or use C<ev_clear_pending> explicitly, as
1793the callbacks for the IO/timeout watchers might not have been called yet.
1444 1794
1445 static ev_io iow [nfd]; 1795 static ev_io iow [nfd];
1446 static ev_timer tw; 1796 static ev_timer tw;
1447 1797
1448 static void 1798 static void
1449 io_cb (ev_loop *loop, ev_io *w, int revents) 1799 io_cb (ev_loop *loop, ev_io *w, int revents)
1450 { 1800 {
1451 // set the relevant poll flags
1452 // could also call adns_processreadable etc. here
1453 struct pollfd *fd = (struct pollfd *)w->data;
1454 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1455 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1456 } 1801 }
1457 1802
1458 // create io watchers for each fd and a timer before blocking 1803 // create io watchers for each fd and a timer before blocking
1459 static void 1804 static void
1460 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1805 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1466 1811
1467 /* the callback is illegal, but won't be called as we stop during check */ 1812 /* the callback is illegal, but won't be called as we stop during check */
1468 ev_timer_init (&tw, 0, timeout * 1e-3); 1813 ev_timer_init (&tw, 0, timeout * 1e-3);
1469 ev_timer_start (loop, &tw); 1814 ev_timer_start (loop, &tw);
1470 1815
1471 // create on ev_io per pollfd 1816 // create one ev_io per pollfd
1472 for (int i = 0; i < nfd; ++i) 1817 for (int i = 0; i < nfd; ++i)
1473 { 1818 {
1474 ev_io_init (iow + i, io_cb, fds [i].fd, 1819 ev_io_init (iow + i, io_cb, fds [i].fd,
1475 ((fds [i].events & POLLIN ? EV_READ : 0) 1820 ((fds [i].events & POLLIN ? EV_READ : 0)
1476 | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1821 | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1477 1822
1478 fds [i].revents = 0; 1823 fds [i].revents = 0;
1479 iow [i].data = fds + i;
1480 ev_io_start (loop, iow + i); 1824 ev_io_start (loop, iow + i);
1481 } 1825 }
1482 } 1826 }
1483 1827
1484 // stop all watchers after blocking 1828 // stop all watchers after blocking
1486 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1830 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1487 { 1831 {
1488 ev_timer_stop (loop, &tw); 1832 ev_timer_stop (loop, &tw);
1489 1833
1490 for (int i = 0; i < nfd; ++i) 1834 for (int i = 0; i < nfd; ++i)
1835 {
1836 // set the relevant poll flags
1837 // could also call adns_processreadable etc. here
1838 struct pollfd *fd = fds + i;
1839 int revents = ev_clear_pending (iow + i);
1840 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1841 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1842
1843 // now stop the watcher
1491 ev_io_stop (loop, iow + i); 1844 ev_io_stop (loop, iow + i);
1845 }
1492 1846
1493 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1847 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1848 }
1849
1850Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1851in the prepare watcher and would dispose of the check watcher.
1852
1853Method 3: If the module to be embedded supports explicit event
1854notification (adns does), you can also make use of the actual watcher
1855callbacks, and only destroy/create the watchers in the prepare watcher.
1856
1857 static void
1858 timer_cb (EV_P_ ev_timer *w, int revents)
1859 {
1860 adns_state ads = (adns_state)w->data;
1861 update_now (EV_A);
1862
1863 adns_processtimeouts (ads, &tv_now);
1864 }
1865
1866 static void
1867 io_cb (EV_P_ ev_io *w, int revents)
1868 {
1869 adns_state ads = (adns_state)w->data;
1870 update_now (EV_A);
1871
1872 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1873 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1874 }
1875
1876 // do not ever call adns_afterpoll
1877
1878Method 4: Do not use a prepare or check watcher because the module you
1879want to embed is too inflexible to support it. Instead, youc na override
1880their poll function. The drawback with this solution is that the main
1881loop is now no longer controllable by EV. The C<Glib::EV> module does
1882this.
1883
1884 static gint
1885 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1886 {
1887 int got_events = 0;
1888
1889 for (n = 0; n < nfds; ++n)
1890 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1891
1892 if (timeout >= 0)
1893 // create/start timer
1894
1895 // poll
1896 ev_loop (EV_A_ 0);
1897
1898 // stop timer again
1899 if (timeout >= 0)
1900 ev_timer_stop (EV_A_ &to);
1901
1902 // stop io watchers again - their callbacks should have set
1903 for (n = 0; n < nfds; ++n)
1904 ev_io_stop (EV_A_ iow [n]);
1905
1906 return got_events;
1494 } 1907 }
1495 1908
1496 1909
1497=head2 C<ev_embed> - when one backend isn't enough... 1910=head2 C<ev_embed> - when one backend isn't enough...
1498 1911
1541portable one. 1954portable one.
1542 1955
1543So when you want to use this feature you will always have to be prepared 1956So when you want to use this feature you will always have to be prepared
1544that you cannot get an embeddable loop. The recommended way to get around 1957that you cannot get an embeddable loop. The recommended way to get around
1545this is to have a separate variables for your embeddable loop, try to 1958this is to have a separate variables for your embeddable loop, try to
1546create it, and if that fails, use the normal loop for everything: 1959create it, and if that fails, use the normal loop for everything.
1960
1961=head3 Watcher-Specific Functions and Data Members
1962
1963=over 4
1964
1965=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1966
1967=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1968
1969Configures the watcher to embed the given loop, which must be
1970embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1971invoked automatically, otherwise it is the responsibility of the callback
1972to invoke it (it will continue to be called until the sweep has been done,
1973if you do not want thta, you need to temporarily stop the embed watcher).
1974
1975=item ev_embed_sweep (loop, ev_embed *)
1976
1977Make a single, non-blocking sweep over the embedded loop. This works
1978similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1979apropriate way for embedded loops.
1980
1981=item struct ev_loop *other [read-only]
1982
1983The embedded event loop.
1984
1985=back
1986
1987=head3 Examples
1988
1989Example: Try to get an embeddable event loop and embed it into the default
1990event loop. If that is not possible, use the default loop. The default
1991loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1992C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1993used).
1547 1994
1548 struct ev_loop *loop_hi = ev_default_init (0); 1995 struct ev_loop *loop_hi = ev_default_init (0);
1549 struct ev_loop *loop_lo = 0; 1996 struct ev_loop *loop_lo = 0;
1550 struct ev_embed embed; 1997 struct ev_embed embed;
1551 1998
1562 ev_embed_start (loop_hi, &embed); 2009 ev_embed_start (loop_hi, &embed);
1563 } 2010 }
1564 else 2011 else
1565 loop_lo = loop_hi; 2012 loop_lo = loop_hi;
1566 2013
1567=over 4 2014Example: Check if kqueue is available but not recommended and create
2015a kqueue backend for use with sockets (which usually work with any
2016kqueue implementation). Store the kqueue/socket-only event loop in
2017C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1568 2018
1569=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2019 struct ev_loop *loop = ev_default_init (0);
2020 struct ev_loop *loop_socket = 0;
2021 struct ev_embed embed;
2022
2023 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2024 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2025 {
2026 ev_embed_init (&embed, 0, loop_socket);
2027 ev_embed_start (loop, &embed);
2028 }
1570 2029
1571=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2030 if (!loop_socket)
2031 loop_socket = loop;
1572 2032
1573Configures the watcher to embed the given loop, which must be 2033 // now use loop_socket for all sockets, and loop for everything else
1574embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1575invoked automatically, otherwise it is the responsibility of the callback
1576to invoke it (it will continue to be called until the sweep has been done,
1577if you do not want thta, you need to temporarily stop the embed watcher).
1578
1579=item ev_embed_sweep (loop, ev_embed *)
1580
1581Make a single, non-blocking sweep over the embedded loop. This works
1582similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1583apropriate way for embedded loops.
1584
1585=item struct ev_loop *loop [read-only]
1586
1587The embedded event loop.
1588
1589=back
1590 2034
1591 2035
1592=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2036=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1593 2037
1594Fork watchers are called when a C<fork ()> was detected (usually because 2038Fork watchers are called when a C<fork ()> was detected (usually because
1597event loop blocks next and before C<ev_check> watchers are being called, 2041event loop blocks next and before C<ev_check> watchers are being called,
1598and only in the child after the fork. If whoever good citizen calling 2042and only in the child after the fork. If whoever good citizen calling
1599C<ev_default_fork> cheats and calls it in the wrong process, the fork 2043C<ev_default_fork> cheats and calls it in the wrong process, the fork
1600handlers will be invoked, too, of course. 2044handlers will be invoked, too, of course.
1601 2045
2046=head3 Watcher-Specific Functions and Data Members
2047
1602=over 4 2048=over 4
1603 2049
1604=item ev_fork_init (ev_signal *, callback) 2050=item ev_fork_init (ev_signal *, callback)
1605 2051
1606Initialises and configures the fork watcher - it has no parameters of any 2052Initialises and configures the fork watcher - it has no parameters of any
1607kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, 2053kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1608believe me. 2054believe me.
2055
2056=back
2057
2058
2059=head2 C<ev_async> - how to wake up another event loop
2060
2061In general, you cannot use an C<ev_loop> from multiple threads or other
2062asynchronous sources such as signal handlers (as opposed to multiple event
2063loops - those are of course safe to use in different threads).
2064
2065Sometimes, however, you need to wake up another event loop you do not
2066control, for example because it belongs to another thread. This is what
2067C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
2068can signal it by calling C<ev_async_send>, which is thread- and signal
2069safe.
2070
2071This functionality is very similar to C<ev_signal> watchers, as signals,
2072too, are asynchronous in nature, and signals, too, will be compressed
2073(i.e. the number of callback invocations may be less than the number of
2074C<ev_async_sent> calls).
2075
2076Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2077just the default loop.
2078
2079=head3 Queueing
2080
2081C<ev_async> does not support queueing of data in any way. The reason
2082is that the author does not know of a simple (or any) algorithm for a
2083multiple-writer-single-reader queue that works in all cases and doesn't
2084need elaborate support such as pthreads.
2085
2086That means that if you want to queue data, you have to provide your own
2087queue. But at least I can tell you would implement locking around your
2088queue:
2089
2090=over 4
2091
2092=item queueing from a signal handler context
2093
2094To implement race-free queueing, you simply add to the queue in the signal
2095handler but you block the signal handler in the watcher callback. Here is an example that does that for
2096some fictitiuous SIGUSR1 handler:
2097
2098 static ev_async mysig;
2099
2100 static void
2101 sigusr1_handler (void)
2102 {
2103 sometype data;
2104
2105 // no locking etc.
2106 queue_put (data);
2107 ev_async_send (EV_DEFAULT_ &mysig);
2108 }
2109
2110 static void
2111 mysig_cb (EV_P_ ev_async *w, int revents)
2112 {
2113 sometype data;
2114 sigset_t block, prev;
2115
2116 sigemptyset (&block);
2117 sigaddset (&block, SIGUSR1);
2118 sigprocmask (SIG_BLOCK, &block, &prev);
2119
2120 while (queue_get (&data))
2121 process (data);
2122
2123 if (sigismember (&prev, SIGUSR1)
2124 sigprocmask (SIG_UNBLOCK, &block, 0);
2125 }
2126
2127(Note: pthreads in theory requires you to use C<pthread_setmask>
2128instead of C<sigprocmask> when you use threads, but libev doesn't do it
2129either...).
2130
2131=item queueing from a thread context
2132
2133The strategy for threads is different, as you cannot (easily) block
2134threads but you can easily preempt them, so to queue safely you need to
2135employ a traditional mutex lock, such as in this pthread example:
2136
2137 static ev_async mysig;
2138 static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2139
2140 static void
2141 otherthread (void)
2142 {
2143 // only need to lock the actual queueing operation
2144 pthread_mutex_lock (&mymutex);
2145 queue_put (data);
2146 pthread_mutex_unlock (&mymutex);
2147
2148 ev_async_send (EV_DEFAULT_ &mysig);
2149 }
2150
2151 static void
2152 mysig_cb (EV_P_ ev_async *w, int revents)
2153 {
2154 pthread_mutex_lock (&mymutex);
2155
2156 while (queue_get (&data))
2157 process (data);
2158
2159 pthread_mutex_unlock (&mymutex);
2160 }
2161
2162=back
2163
2164
2165=head3 Watcher-Specific Functions and Data Members
2166
2167=over 4
2168
2169=item ev_async_init (ev_async *, callback)
2170
2171Initialises and configures the async watcher - it has no parameters of any
2172kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2173believe me.
2174
2175=item ev_async_send (loop, ev_async *)
2176
2177Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2178an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2179C<ev_feed_event>, this call is safe to do in other threads, signal or
2180similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
2181section below on what exactly this means).
2182
2183This call incurs the overhead of a syscall only once per loop iteration,
2184so while the overhead might be noticable, it doesn't apply to repeated
2185calls to C<ev_async_send>.
1609 2186
1610=back 2187=back
1611 2188
1612 2189
1613=head1 OTHER FUNCTIONS 2190=head1 OTHER FUNCTIONS
1702 2279
1703To use it, 2280To use it,
1704 2281
1705 #include <ev++.h> 2282 #include <ev++.h>
1706 2283
1707(it is not installed by default). This automatically includes F<ev.h> 2284This automatically includes F<ev.h> and puts all of its definitions (many
1708and puts all of its definitions (many of them macros) into the global 2285of them macros) into the global namespace. All C++ specific things are
1709namespace. All C++ specific things are put into the C<ev> namespace. 2286put into the C<ev> namespace. It should support all the same embedding
2287options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1710 2288
1711It should support all the same embedding options as F<ev.h>, most notably 2289Care has been taken to keep the overhead low. The only data member the C++
1712C<EV_MULTIPLICITY>. 2290classes add (compared to plain C-style watchers) is the event loop pointer
2291that the watcher is associated with (or no additional members at all if
2292you disable C<EV_MULTIPLICITY> when embedding libev).
2293
2294Currently, functions, and static and non-static member functions can be
2295used as callbacks. Other types should be easy to add as long as they only
2296need one additional pointer for context. If you need support for other
2297types of functors please contact the author (preferably after implementing
2298it).
1713 2299
1714Here is a list of things available in the C<ev> namespace: 2300Here is a list of things available in the C<ev> namespace:
1715 2301
1716=over 4 2302=over 4
1717 2303
1733 2319
1734All of those classes have these methods: 2320All of those classes have these methods:
1735 2321
1736=over 4 2322=over 4
1737 2323
1738=item ev::TYPE::TYPE (object *, object::method *) 2324=item ev::TYPE::TYPE ()
1739 2325
1740=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *) 2326=item ev::TYPE::TYPE (struct ev_loop *)
1741 2327
1742=item ev::TYPE::~TYPE 2328=item ev::TYPE::~TYPE
1743 2329
1744The constructor takes a pointer to an object and a method pointer to 2330The constructor (optionally) takes an event loop to associate the watcher
1745the event handler callback to call in this class. The constructor calls 2331with. If it is omitted, it will use C<EV_DEFAULT>.
1746C<ev_init> for you, which means you have to call the C<set> method 2332
1747before starting it. If you do not specify a loop then the constructor 2333The constructor calls C<ev_init> for you, which means you have to call the
1748automatically associates the default loop with this watcher. 2334C<set> method before starting it.
2335
2336It will not set a callback, however: You have to call the templated C<set>
2337method to set a callback before you can start the watcher.
2338
2339(The reason why you have to use a method is a limitation in C++ which does
2340not allow explicit template arguments for constructors).
1749 2341
1750The destructor automatically stops the watcher if it is active. 2342The destructor automatically stops the watcher if it is active.
2343
2344=item w->set<class, &class::method> (object *)
2345
2346This method sets the callback method to call. The method has to have a
2347signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
2348first argument and the C<revents> as second. The object must be given as
2349parameter and is stored in the C<data> member of the watcher.
2350
2351This method synthesizes efficient thunking code to call your method from
2352the C callback that libev requires. If your compiler can inline your
2353callback (i.e. it is visible to it at the place of the C<set> call and
2354your compiler is good :), then the method will be fully inlined into the
2355thunking function, making it as fast as a direct C callback.
2356
2357Example: simple class declaration and watcher initialisation
2358
2359 struct myclass
2360 {
2361 void io_cb (ev::io &w, int revents) { }
2362 }
2363
2364 myclass obj;
2365 ev::io iow;
2366 iow.set <myclass, &myclass::io_cb> (&obj);
2367
2368=item w->set<function> (void *data = 0)
2369
2370Also sets a callback, but uses a static method or plain function as
2371callback. The optional C<data> argument will be stored in the watcher's
2372C<data> member and is free for you to use.
2373
2374The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2375
2376See the method-C<set> above for more details.
2377
2378Example:
2379
2380 static void io_cb (ev::io &w, int revents) { }
2381 iow.set <io_cb> ();
1751 2382
1752=item w->set (struct ev_loop *) 2383=item w->set (struct ev_loop *)
1753 2384
1754Associates a different C<struct ev_loop> with this watcher. You can only 2385Associates a different C<struct ev_loop> with this watcher. You can only
1755do this when the watcher is inactive (and not pending either). 2386do this when the watcher is inactive (and not pending either).
1756 2387
1757=item w->set ([args]) 2388=item w->set ([args])
1758 2389
1759Basically the same as C<ev_TYPE_set>, with the same args. Must be 2390Basically the same as C<ev_TYPE_set>, with the same args. Must be
1760called at least once. Unlike the C counterpart, an active watcher gets 2391called at least once. Unlike the C counterpart, an active watcher gets
1761automatically stopped and restarted. 2392automatically stopped and restarted when reconfiguring it with this
2393method.
1762 2394
1763=item w->start () 2395=item w->start ()
1764 2396
1765Starts the watcher. Note that there is no C<loop> argument as the 2397Starts the watcher. Note that there is no C<loop> argument, as the
1766constructor already takes the loop. 2398constructor already stores the event loop.
1767 2399
1768=item w->stop () 2400=item w->stop ()
1769 2401
1770Stops the watcher if it is active. Again, no C<loop> argument. 2402Stops the watcher if it is active. Again, no C<loop> argument.
1771 2403
1772=item w->again () C<ev::timer>, C<ev::periodic> only 2404=item w->again () (C<ev::timer>, C<ev::periodic> only)
1773 2405
1774For C<ev::timer> and C<ev::periodic>, this invokes the corresponding 2406For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1775C<ev_TYPE_again> function. 2407C<ev_TYPE_again> function.
1776 2408
1777=item w->sweep () C<ev::embed> only 2409=item w->sweep () (C<ev::embed> only)
1778 2410
1779Invokes C<ev_embed_sweep>. 2411Invokes C<ev_embed_sweep>.
1780 2412
1781=item w->update () C<ev::stat> only 2413=item w->update () (C<ev::stat> only)
1782 2414
1783Invokes C<ev_stat_stat>. 2415Invokes C<ev_stat_stat>.
1784 2416
1785=back 2417=back
1786 2418
1789Example: Define a class with an IO and idle watcher, start one of them in 2421Example: Define a class with an IO and idle watcher, start one of them in
1790the constructor. 2422the constructor.
1791 2423
1792 class myclass 2424 class myclass
1793 { 2425 {
1794 ev_io io; void io_cb (ev::io &w, int revents); 2426 ev::io io; void io_cb (ev::io &w, int revents);
1795 ev_idle idle void idle_cb (ev::idle &w, int revents); 2427 ev:idle idle void idle_cb (ev::idle &w, int revents);
1796 2428
1797 myclass (); 2429 myclass (int fd)
1798 }
1799
1800 myclass::myclass (int fd)
1801 : io (this, &myclass::io_cb),
1802 idle (this, &myclass::idle_cb)
1803 { 2430 {
2431 io .set <myclass, &myclass::io_cb > (this);
2432 idle.set <myclass, &myclass::idle_cb> (this);
2433
1804 io.start (fd, ev::READ); 2434 io.start (fd, ev::READ);
2435 }
1805 } 2436 };
1806 2437
1807 2438
1808=head1 MACRO MAGIC 2439=head1 MACRO MAGIC
1809 2440
1810Libev can be compiled with a variety of options, the most fundemantal is 2441Libev can be compiled with a variety of options, the most fundamantal
1811C<EV_MULTIPLICITY>. This option determines wether (most) functions and 2442of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1812callbacks have an initial C<struct ev_loop *> argument. 2443functions and callbacks have an initial C<struct ev_loop *> argument.
1813 2444
1814To make it easier to write programs that cope with either variant, the 2445To make it easier to write programs that cope with either variant, the
1815following macros are defined: 2446following macros are defined:
1816 2447
1817=over 4 2448=over 4
1850loop, if multiple loops are supported ("ev loop default"). 2481loop, if multiple loops are supported ("ev loop default").
1851 2482
1852=back 2483=back
1853 2484
1854Example: Declare and initialise a check watcher, utilising the above 2485Example: Declare and initialise a check watcher, utilising the above
1855macros so it will work regardless of wether multiple loops are supported 2486macros so it will work regardless of whether multiple loops are supported
1856or not. 2487or not.
1857 2488
1858 static void 2489 static void
1859 check_cb (EV_P_ ev_timer *w, int revents) 2490 check_cb (EV_P_ ev_timer *w, int revents)
1860 { 2491 {
1871Libev can (and often is) directly embedded into host 2502Libev can (and often is) directly embedded into host
1872applications. Examples of applications that embed it include the Deliantra 2503applications. Examples of applications that embed it include the Deliantra
1873Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2504Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1874and rxvt-unicode. 2505and rxvt-unicode.
1875 2506
1876The goal is to enable you to just copy the neecssary files into your 2507The goal is to enable you to just copy the necessary files into your
1877source directory without having to change even a single line in them, so 2508source directory without having to change even a single line in them, so
1878you can easily upgrade by simply copying (or having a checked-out copy of 2509you can easily upgrade by simply copying (or having a checked-out copy of
1879libev somewhere in your source tree). 2510libev somewhere in your source tree).
1880 2511
1881=head2 FILESETS 2512=head2 FILESETS
1971 2602
1972If defined to be C<1>, libev will try to detect the availability of the 2603If defined to be C<1>, libev will try to detect the availability of the
1973monotonic clock option at both compiletime and runtime. Otherwise no use 2604monotonic clock option at both compiletime and runtime. Otherwise no use
1974of the monotonic clock option will be attempted. If you enable this, you 2605of the monotonic clock option will be attempted. If you enable this, you
1975usually have to link against librt or something similar. Enabling it when 2606usually have to link against librt or something similar. Enabling it when
1976the functionality isn't available is safe, though, althoguh you have 2607the functionality isn't available is safe, though, although you have
1977to make sure you link against any libraries where the C<clock_gettime> 2608to make sure you link against any libraries where the C<clock_gettime>
1978function is hiding in (often F<-lrt>). 2609function is hiding in (often F<-lrt>).
1979 2610
1980=item EV_USE_REALTIME 2611=item EV_USE_REALTIME
1981 2612
1982If defined to be C<1>, libev will try to detect the availability of the 2613If defined to be C<1>, libev will try to detect the availability of the
1983realtime clock option at compiletime (and assume its availability at 2614realtime clock option at compiletime (and assume its availability at
1984runtime if successful). Otherwise no use of the realtime clock option will 2615runtime if successful). Otherwise no use of the realtime clock option will
1985be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2616be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1986(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries 2617(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1987in the description of C<EV_USE_MONOTONIC>, though. 2618note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2619
2620=item EV_USE_NANOSLEEP
2621
2622If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2623and will use it for delays. Otherwise it will use C<select ()>.
1988 2624
1989=item EV_USE_SELECT 2625=item EV_USE_SELECT
1990 2626
1991If undefined or defined to be C<1>, libev will compile in support for the 2627If undefined or defined to be C<1>, libev will compile in support for the
1992C<select>(2) backend. No attempt at autodetection will be done: if no 2628C<select>(2) backend. No attempt at autodetection will be done: if no
2010wants osf handles on win32 (this is the case when the select to 2646wants osf handles on win32 (this is the case when the select to
2011be used is the winsock select). This means that it will call 2647be used is the winsock select). This means that it will call
2012C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2648C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2013it is assumed that all these functions actually work on fds, even 2649it is assumed that all these functions actually work on fds, even
2014on win32. Should not be defined on non-win32 platforms. 2650on win32. Should not be defined on non-win32 platforms.
2651
2652=item EV_FD_TO_WIN32_HANDLE
2653
2654If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2655file descriptors to socket handles. When not defining this symbol (the
2656default), then libev will call C<_get_osfhandle>, which is usually
2657correct. In some cases, programs use their own file descriptor management,
2658in which case they can provide this function to map fds to socket handles.
2015 2659
2016=item EV_USE_POLL 2660=item EV_USE_POLL
2017 2661
2018If defined to be C<1>, libev will compile in support for the C<poll>(2) 2662If defined to be C<1>, libev will compile in support for the C<poll>(2)
2019backend. Otherwise it will be enabled on non-win32 platforms. It 2663backend. Otherwise it will be enabled on non-win32 platforms. It
2053 2697
2054If defined to be C<1>, libev will compile in support for the Linux inotify 2698If defined to be C<1>, libev will compile in support for the Linux inotify
2055interface to speed up C<ev_stat> watchers. Its actual availability will 2699interface to speed up C<ev_stat> watchers. Its actual availability will
2056be detected at runtime. 2700be detected at runtime.
2057 2701
2702=item EV_ATOMIC_T
2703
2704Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2705access is atomic with respect to other threads or signal contexts. No such
2706type is easily found in the C language, so you can provide your own type
2707that you know is safe for your purposes. It is used both for signal handler "locking"
2708as well as for signal and thread safety in C<ev_async> watchers.
2709
2710In the absense of this define, libev will use C<sig_atomic_t volatile>
2711(from F<signal.h>), which is usually good enough on most platforms.
2712
2058=item EV_H 2713=item EV_H
2059 2714
2060The name of the F<ev.h> header file used to include it. The default if 2715The name of the F<ev.h> header file used to include it. The default if
2061undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2716undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2062can be used to virtually rename the F<ev.h> header file in case of conflicts. 2717used to virtually rename the F<ev.h> header file in case of conflicts.
2063 2718
2064=item EV_CONFIG_H 2719=item EV_CONFIG_H
2065 2720
2066If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2721If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2067F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2722F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2068C<EV_H>, above. 2723C<EV_H>, above.
2069 2724
2070=item EV_EVENT_H 2725=item EV_EVENT_H
2071 2726
2072Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2727Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2073of how the F<event.h> header can be found. 2728of how the F<event.h> header can be found, the default is C<"event.h">.
2074 2729
2075=item EV_PROTOTYPES 2730=item EV_PROTOTYPES
2076 2731
2077If defined to be C<0>, then F<ev.h> will not define any function 2732If defined to be C<0>, then F<ev.h> will not define any function
2078prototypes, but still define all the structs and other symbols. This is 2733prototypes, but still define all the structs and other symbols. This is
2085will have the C<struct ev_loop *> as first argument, and you can create 2740will have the C<struct ev_loop *> as first argument, and you can create
2086additional independent event loops. Otherwise there will be no support 2741additional independent event loops. Otherwise there will be no support
2087for multiple event loops and there is no first event loop pointer 2742for multiple event loops and there is no first event loop pointer
2088argument. Instead, all functions act on the single default loop. 2743argument. Instead, all functions act on the single default loop.
2089 2744
2745=item EV_MINPRI
2746
2747=item EV_MAXPRI
2748
2749The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
2750C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
2751provide for more priorities by overriding those symbols (usually defined
2752to be C<-2> and C<2>, respectively).
2753
2754When doing priority-based operations, libev usually has to linearly search
2755all the priorities, so having many of them (hundreds) uses a lot of space
2756and time, so using the defaults of five priorities (-2 .. +2) is usually
2757fine.
2758
2759If your embedding app does not need any priorities, defining these both to
2760C<0> will save some memory and cpu.
2761
2090=item EV_PERIODIC_ENABLE 2762=item EV_PERIODIC_ENABLE
2091 2763
2092If undefined or defined to be C<1>, then periodic timers are supported. If 2764If undefined or defined to be C<1>, then periodic timers are supported. If
2093defined to be C<0>, then they are not. Disabling them saves a few kB of 2765defined to be C<0>, then they are not. Disabling them saves a few kB of
2094code. 2766code.
2095 2767
2768=item EV_IDLE_ENABLE
2769
2770If undefined or defined to be C<1>, then idle watchers are supported. If
2771defined to be C<0>, then they are not. Disabling them saves a few kB of
2772code.
2773
2096=item EV_EMBED_ENABLE 2774=item EV_EMBED_ENABLE
2097 2775
2098If undefined or defined to be C<1>, then embed watchers are supported. If 2776If undefined or defined to be C<1>, then embed watchers are supported. If
2099defined to be C<0>, then they are not. 2777defined to be C<0>, then they are not.
2100 2778
2104defined to be C<0>, then they are not. 2782defined to be C<0>, then they are not.
2105 2783
2106=item EV_FORK_ENABLE 2784=item EV_FORK_ENABLE
2107 2785
2108If undefined or defined to be C<1>, then fork watchers are supported. If 2786If undefined or defined to be C<1>, then fork watchers are supported. If
2787defined to be C<0>, then they are not.
2788
2789=item EV_ASYNC_ENABLE
2790
2791If undefined or defined to be C<1>, then async watchers are supported. If
2109defined to be C<0>, then they are not. 2792defined to be C<0>, then they are not.
2110 2793
2111=item EV_MINIMAL 2794=item EV_MINIMAL
2112 2795
2113If you need to shave off some kilobytes of code at the expense of some 2796If you need to shave off some kilobytes of code at the expense of some
2121than enough. If you need to manage thousands of children you might want to 2804than enough. If you need to manage thousands of children you might want to
2122increase this value (I<must> be a power of two). 2805increase this value (I<must> be a power of two).
2123 2806
2124=item EV_INOTIFY_HASHSIZE 2807=item EV_INOTIFY_HASHSIZE
2125 2808
2126C<ev_staz> watchers use a small hash table to distribute workload by 2809C<ev_stat> watchers use a small hash table to distribute workload by
2127inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 2810inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2128usually more than enough. If you need to manage thousands of C<ev_stat> 2811usually more than enough. If you need to manage thousands of C<ev_stat>
2129watchers you might want to increase this value (I<must> be a power of 2812watchers you might want to increase this value (I<must> be a power of
2130two). 2813two).
2131 2814
2148 2831
2149=item ev_set_cb (ev, cb) 2832=item ev_set_cb (ev, cb)
2150 2833
2151Can be used to change the callback member declaration in each watcher, 2834Can be used to change the callback member declaration in each watcher,
2152and the way callbacks are invoked and set. Must expand to a struct member 2835and the way callbacks are invoked and set. Must expand to a struct member
2153definition and a statement, respectively. See the F<ev.v> header file for 2836definition and a statement, respectively. See the F<ev.h> header file for
2154their default definitions. One possible use for overriding these is to 2837their default definitions. One possible use for overriding these is to
2155avoid the C<struct ev_loop *> as first argument in all cases, or to use 2838avoid the C<struct ev_loop *> as first argument in all cases, or to use
2156method calls instead of plain function calls in C++. 2839method calls instead of plain function calls in C++.
2840
2841=head2 EXPORTED API SYMBOLS
2842
2843If you need to re-export the API (e.g. via a dll) and you need a list of
2844exported symbols, you can use the provided F<Symbol.*> files which list
2845all public symbols, one per line:
2846
2847 Symbols.ev for libev proper
2848 Symbols.event for the libevent emulation
2849
2850This can also be used to rename all public symbols to avoid clashes with
2851multiple versions of libev linked together (which is obviously bad in
2852itself, but sometimes it is inconvinient to avoid this).
2853
2854A sed command like this will create wrapper C<#define>'s that you need to
2855include before including F<ev.h>:
2856
2857 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2858
2859This would create a file F<wrap.h> which essentially looks like this:
2860
2861 #define ev_backend myprefix_ev_backend
2862 #define ev_check_start myprefix_ev_check_start
2863 #define ev_check_stop myprefix_ev_check_stop
2864 ...
2157 2865
2158=head2 EXAMPLES 2866=head2 EXAMPLES
2159 2867
2160For a real-world example of a program the includes libev 2868For a real-world example of a program the includes libev
2161verbatim, you can have a look at the EV perl module 2869verbatim, you can have a look at the EV perl module
2190 2898
2191In this section the complexities of (many of) the algorithms used inside 2899In this section the complexities of (many of) the algorithms used inside
2192libev will be explained. For complexity discussions about backends see the 2900libev will be explained. For complexity discussions about backends see the
2193documentation for C<ev_default_init>. 2901documentation for C<ev_default_init>.
2194 2902
2903All of the following are about amortised time: If an array needs to be
2904extended, libev needs to realloc and move the whole array, but this
2905happens asymptotically never with higher number of elements, so O(1) might
2906mean it might do a lengthy realloc operation in rare cases, but on average
2907it is much faster and asymptotically approaches constant time.
2908
2195=over 4 2909=over 4
2196 2910
2197=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2911=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2198 2912
2913This means that, when you have a watcher that triggers in one hour and
2914there are 100 watchers that would trigger before that then inserting will
2915have to skip roughly seven (C<ld 100>) of these watchers.
2916
2199=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2917=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2200 2918
2919That means that changing a timer costs less than removing/adding them
2920as only the relative motion in the event queue has to be paid for.
2921
2201=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2922=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2202 2923
2924These just add the watcher into an array or at the head of a list.
2925
2203=item Stopping check/prepare/idle watchers: O(1) 2926=item Stopping check/prepare/idle/fork/async watchers: O(1)
2204 2927
2205=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2928=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2206 2929
2930These watchers are stored in lists then need to be walked to find the
2931correct watcher to remove. The lists are usually short (you don't usually
2932have many watchers waiting for the same fd or signal).
2933
2207=item Finding the next timer per loop iteration: O(1) 2934=item Finding the next timer in each loop iteration: O(1)
2935
2936By virtue of using a binary heap, the next timer is always found at the
2937beginning of the storage array.
2208 2938
2209=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2939=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2210 2940
2211=item Activating one watcher: O(1) 2941A change means an I/O watcher gets started or stopped, which requires
2942libev to recalculate its status (and possibly tell the kernel, depending
2943on backend and wether C<ev_io_set> was used).
2944
2945=item Activating one watcher (putting it into the pending state): O(1)
2946
2947=item Priority handling: O(number_of_priorities)
2948
2949Priorities are implemented by allocating some space for each
2950priority. When doing priority-based operations, libev usually has to
2951linearly search all the priorities, but starting/stopping and activating
2952watchers becomes O(1) w.r.t. priority handling.
2953
2954=item Sending an ev_async: O(1)
2955
2956=item Processing ev_async_send: O(number_of_async_watchers)
2957
2958=item Processing signals: O(max_signal_number)
2959
2960Sending involves a syscall I<iff> there were no other C<ev_async_send>
2961calls in the current loop iteration. Checking for async and signal events
2962involves iterating over all running async watchers or all signal numbers.
2212 2963
2213=back 2964=back
2214 2965
2215 2966
2967=head1 Win32 platform limitations and workarounds
2968
2969Win32 doesn't support any of the standards (e.g. POSIX) that libev
2970requires, and its I/O model is fundamentally incompatible with the POSIX
2971model. Libev still offers limited functionality on this platform in
2972the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2973descriptors. This only applies when using Win32 natively, not when using
2974e.g. cygwin.
2975
2976There is no supported compilation method available on windows except
2977embedding it into other applications.
2978
2979Due to the many, low, and arbitrary limits on the win32 platform and the
2980abysmal performance of winsockets, using a large number of sockets is not
2981recommended (and not reasonable). If your program needs to use more than
2982a hundred or so sockets, then likely it needs to use a totally different
2983implementation for windows, as libev offers the POSIX model, which cannot
2984be implemented efficiently on windows (microsoft monopoly games).
2985
2986=over 4
2987
2988=item The winsocket select function
2989
2990The winsocket C<select> function doesn't follow POSIX in that it requires
2991socket I<handles> and not socket I<file descriptors>. This makes select
2992very inefficient, and also requires a mapping from file descriptors
2993to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2994C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2995symbols for more info.
2996
2997The configuration for a "naked" win32 using the microsoft runtime
2998libraries and raw winsocket select is:
2999
3000 #define EV_USE_SELECT 1
3001 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3002
3003Note that winsockets handling of fd sets is O(n), so you can easily get a
3004complexity in the O(n²) range when using win32.
3005
3006=item Limited number of file descriptors
3007
3008Windows has numerous arbitrary (and low) limits on things. Early versions
3009of winsocket's select only supported waiting for a max. of C<64> handles
3010(probably owning to the fact that all windows kernels can only wait for
3011C<64> things at the same time internally; microsoft recommends spawning a
3012chain of threads and wait for 63 handles and the previous thread in each).
3013
3014Newer versions support more handles, but you need to define C<FD_SETSIZE>
3015to some high number (e.g. C<2048>) before compiling the winsocket select
3016call (which might be in libev or elsewhere, for example, perl does its own
3017select emulation on windows).
3018
3019Another limit is the number of file descriptors in the microsoft runtime
3020libraries, which by default is C<64> (there must be a hidden I<64> fetish
3021or something like this inside microsoft). You can increase this by calling
3022C<_setmaxstdio>, which can increase this limit to C<2048> (another
3023arbitrary limit), but is broken in many versions of the microsoft runtime
3024libraries.
3025
3026This might get you to about C<512> or C<2048> sockets (depending on
3027windows version and/or the phase of the moon). To get more, you need to
3028wrap all I/O functions and provide your own fd management, but the cost of
3029calling select (O(n²)) will likely make this unworkable.
3030
3031=back
3032
3033
2216=head1 AUTHOR 3034=head1 AUTHOR
2217 3035
2218Marc Lehmann <libev@schmorp.de>. 3036Marc Lehmann <libev@schmorp.de>.
2219 3037

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