… | |
… | |
130 | .\} |
130 | .\} |
131 | .rm #[ #] #H #V #F C |
131 | .rm #[ #] #H #V #F C |
132 | .\" ======================================================================== |
132 | .\" ======================================================================== |
133 | .\" |
133 | .\" |
134 | .IX Title "LIBEV 3" |
134 | .IX Title "LIBEV 3" |
135 | .TH LIBEV 3 "2008-09-29" "libev-3.44" "libev - high performance full featured event loop" |
135 | .TH LIBEV 3 "2009-04-25" "libev-3.6" "libev - high performance full featured event loop" |
136 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
136 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
137 | .\" way too many mistakes in technical documents. |
137 | .\" way too many mistakes in technical documents. |
138 | .if n .ad l |
138 | .if n .ad l |
139 | .nh |
139 | .nh |
140 | .SH "NAME" |
140 | .SH "NAME" |
… | |
… | |
148 | .IX Subsection "EXAMPLE PROGRAM" |
148 | .IX Subsection "EXAMPLE PROGRAM" |
149 | .Vb 2 |
149 | .Vb 2 |
150 | \& // a single header file is required |
150 | \& // a single header file is required |
151 | \& #include <ev.h> |
151 | \& #include <ev.h> |
152 | \& |
152 | \& |
|
|
153 | \& #include <stdio.h> // for puts |
|
|
154 | \& |
153 | \& // every watcher type has its own typedef\*(Aqd struct |
155 | \& // every watcher type has its own typedef\*(Aqd struct |
154 | \& // with the name ev_<type> |
156 | \& // with the name ev_TYPE |
155 | \& ev_io stdin_watcher; |
157 | \& ev_io stdin_watcher; |
156 | \& ev_timer timeout_watcher; |
158 | \& ev_timer timeout_watcher; |
157 | \& |
159 | \& |
158 | \& // all watcher callbacks have a similar signature |
160 | \& // all watcher callbacks have a similar signature |
159 | \& // this callback is called when data is readable on stdin |
161 | \& // this callback is called when data is readable on stdin |
160 | \& static void |
162 | \& static void |
161 | \& stdin_cb (EV_P_ struct ev_io *w, int revents) |
163 | \& stdin_cb (EV_P_ ev_io *w, int revents) |
162 | \& { |
164 | \& { |
163 | \& puts ("stdin ready"); |
165 | \& puts ("stdin ready"); |
164 | \& // for one\-shot events, one must manually stop the watcher |
166 | \& // for one\-shot events, one must manually stop the watcher |
165 | \& // with its corresponding stop function. |
167 | \& // with its corresponding stop function. |
166 | \& ev_io_stop (EV_A_ w); |
168 | \& ev_io_stop (EV_A_ w); |
… | |
… | |
169 | \& ev_unloop (EV_A_ EVUNLOOP_ALL); |
171 | \& ev_unloop (EV_A_ EVUNLOOP_ALL); |
170 | \& } |
172 | \& } |
171 | \& |
173 | \& |
172 | \& // another callback, this time for a time\-out |
174 | \& // another callback, this time for a time\-out |
173 | \& static void |
175 | \& static void |
174 | \& timeout_cb (EV_P_ struct ev_timer *w, int revents) |
176 | \& timeout_cb (EV_P_ ev_timer *w, int revents) |
175 | \& { |
177 | \& { |
176 | \& puts ("timeout"); |
178 | \& puts ("timeout"); |
177 | \& // this causes the innermost ev_loop to stop iterating |
179 | \& // this causes the innermost ev_loop to stop iterating |
178 | \& ev_unloop (EV_A_ EVUNLOOP_ONE); |
180 | \& ev_unloop (EV_A_ EVUNLOOP_ONE); |
179 | \& } |
181 | \& } |
… | |
… | |
199 | \& |
201 | \& |
200 | \& // unloop was called, so exit |
202 | \& // unloop was called, so exit |
201 | \& return 0; |
203 | \& return 0; |
202 | \& } |
204 | \& } |
203 | .Ve |
205 | .Ve |
204 | .SH "DESCRIPTION" |
206 | .SH "ABOUT THIS DOCUMENT" |
205 | .IX Header "DESCRIPTION" |
207 | .IX Header "ABOUT THIS DOCUMENT" |
|
|
208 | This document documents the libev software package. |
|
|
209 | .PP |
206 | The newest version of this document is also available as an html-formatted |
210 | The newest version of this document is also available as an html-formatted |
207 | web page you might find easier to navigate when reading it for the first |
211 | web page you might find easier to navigate when reading it for the first |
208 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
212 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
209 | .PP |
213 | .PP |
|
|
214 | While this document tries to be as complete as possible in documenting |
|
|
215 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
216 | on event-based programming, nor will it introduce event-based programming |
|
|
217 | with libev. |
|
|
218 | .PP |
|
|
219 | Familarity with event based programming techniques in general is assumed |
|
|
220 | throughout this document. |
|
|
221 | .SH "ABOUT LIBEV" |
|
|
222 | .IX Header "ABOUT LIBEV" |
210 | Libev is an event loop: you register interest in certain events (such as a |
223 | Libev is an event loop: you register interest in certain events (such as a |
211 | file descriptor being readable or a timeout occurring), and it will manage |
224 | file descriptor being readable or a timeout occurring), and it will manage |
212 | these event sources and provide your program with events. |
225 | these event sources and provide your program with events. |
213 | .PP |
226 | .PP |
214 | To do this, it must take more or less complete control over your process |
227 | To do this, it must take more or less complete control over your process |
… | |
… | |
240 | Libev is very configurable. In this manual the default (and most common) |
253 | Libev is very configurable. In this manual the default (and most common) |
241 | configuration will be described, which supports multiple event loops. For |
254 | configuration will be described, which supports multiple event loops. For |
242 | more info about various configuration options please have a look at |
255 | more info about various configuration options please have a look at |
243 | \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
256 | \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
244 | for multiple event loops, then all functions taking an initial argument of |
257 | for multiple event loops, then all functions taking an initial argument of |
245 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have |
258 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`ev_loop *\*(C'\fR) will not have |
246 | this argument. |
259 | this argument. |
247 | .Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
260 | .Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
248 | .IX Subsection "TIME REPRESENTATION" |
261 | .IX Subsection "TIME REPRESENTATION" |
249 | Libev represents time as a single floating point number, representing the |
262 | Libev represents time as a single floating point number, representing |
250 | (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
263 | the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere |
251 | the beginning of 1970, details are complicated, don't ask). This type is |
264 | near the beginning of 1970, details are complicated, don't ask). This |
252 | called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
265 | type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually |
253 | to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
266 | aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do any calculations |
254 | it, you should treat it as some floating point value. Unlike the name |
267 | on it, you should treat it as some floating point value. Unlike the name |
255 | component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
268 | component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
256 | throughout libev. |
269 | throughout libev. |
257 | .SH "ERROR HANDLING" |
270 | .SH "ERROR HANDLING" |
258 | .IX Header "ERROR HANDLING" |
271 | .IX Header "ERROR HANDLING" |
259 | Libev knows three classes of errors: operating system errors, usage errors |
272 | Libev knows three classes of errors: operating system errors, usage errors |
… | |
… | |
406 | \& ... |
419 | \& ... |
407 | \& ev_set_syserr_cb (fatal_error); |
420 | \& ev_set_syserr_cb (fatal_error); |
408 | .Ve |
421 | .Ve |
409 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
422 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
410 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
423 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
411 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
424 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR |
412 | types of such loops, the \fIdefault\fR loop, which supports signals and child |
425 | is \fInot\fR optional in this case, as there is also an \f(CW\*(C`ev_loop\*(C'\fR |
413 | events, and dynamically created loops which do not. |
426 | \&\fIfunction\fR). |
|
|
427 | .PP |
|
|
428 | The library knows two types of such loops, the \fIdefault\fR loop, which |
|
|
429 | supports signals and child events, and dynamically created loops which do |
|
|
430 | not. |
414 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
431 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
415 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
432 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
416 | This will initialise the default event loop if it hasn't been initialised |
433 | This will initialise the default event loop if it hasn't been initialised |
417 | yet and return it. If the default loop could not be initialised, returns |
434 | yet and return it. If the default loop could not be initialised, returns |
418 | false. If it already was initialised it simply returns it (and ignores the |
435 | false. If it already was initialised it simply returns it (and ignores the |
… | |
… | |
421 | If you don't know what event loop to use, use the one returned from this |
438 | If you don't know what event loop to use, use the one returned from this |
422 | function. |
439 | function. |
423 | .Sp |
440 | .Sp |
424 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
441 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
425 | from multiple threads, you have to lock (note also that this is unlikely, |
442 | from multiple threads, you have to lock (note also that this is unlikely, |
426 | as loops cannot bes hared easily between threads anyway). |
443 | as loops cannot be shared easily between threads anyway). |
427 | .Sp |
444 | .Sp |
428 | The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
445 | The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
429 | \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
446 | \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
430 | for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
447 | for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
431 | create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
448 | create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
… | |
… | |
506 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
523 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
507 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
524 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
508 | For few fds, this backend is a bit little slower than poll and select, |
525 | For few fds, this backend is a bit little slower than poll and select, |
509 | but it scales phenomenally better. While poll and select usually scale |
526 | but it scales phenomenally better. While poll and select usually scale |
510 | like O(total_fds) where n is the total number of fds (or the highest fd), |
527 | like O(total_fds) where n is the total number of fds (or the highest fd), |
511 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
528 | epoll scales either O(1) or O(active_fds). |
512 | of shortcomings, such as silently dropping events in some hard-to-detect |
529 | .Sp |
513 | cases and requiring a system call per fd change, no fork support and bad |
530 | The epoll mechanism deserves honorable mention as the most misdesigned |
514 | support for dup. |
531 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
532 | dropping file descriptors, requiring a system call per change per file |
|
|
533 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
534 | so on. The biggest issue is fork races, however \- if a program forks then |
|
|
535 | \&\fIboth\fR parent and child process have to recreate the epoll set, which can |
|
|
536 | take considerable time (one syscall per file descriptor) and is of course |
|
|
537 | hard to detect. |
|
|
538 | .Sp |
|
|
539 | Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but |
|
|
540 | of course \fIdoesn't\fR, and epoll just loves to report events for totally |
|
|
541 | \&\fIdifferent\fR file descriptors (even already closed ones, so one cannot |
|
|
542 | even remove them from the set) than registered in the set (especially |
|
|
543 | on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by |
|
|
544 | employing an additional generation counter and comparing that against the |
|
|
545 | events to filter out spurious ones, recreating the set when required. |
515 | .Sp |
546 | .Sp |
516 | While stopping, setting and starting an I/O watcher in the same iteration |
547 | While stopping, setting and starting an I/O watcher in the same iteration |
517 | will result in some caching, there is still a system call per such incident |
548 | will result in some caching, there is still a system call per such |
518 | (because the fd could point to a different file description now), so its |
549 | incident (because the same \fIfile descriptor\fR could point to a different |
519 | best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work |
550 | \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
520 | very well if you register events for both fds. |
551 | file descriptors might not work very well if you register events for both |
521 | .Sp |
552 | file descriptors. |
522 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
523 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
524 | (or space) is available. |
|
|
525 | .Sp |
553 | .Sp |
526 | Best performance from this backend is achieved by not unregistering all |
554 | Best performance from this backend is achieved by not unregistering all |
527 | watchers for a file descriptor until it has been closed, if possible, |
555 | watchers for a file descriptor until it has been closed, if possible, |
528 | i.e. keep at least one watcher active per fd at all times. Stopping and |
556 | i.e. keep at least one watcher active per fd at all times. Stopping and |
529 | starting a watcher (without re-setting it) also usually doesn't cause |
557 | starting a watcher (without re-setting it) also usually doesn't cause |
530 | extra overhead. |
558 | extra overhead. A fork can both result in spurious notifications as well |
|
|
559 | as in libev having to destroy and recreate the epoll object, which can |
|
|
560 | take considerable time and thus should be avoided. |
|
|
561 | .Sp |
|
|
562 | All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
|
|
563 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
564 | the usage. So sad. |
531 | .Sp |
565 | .Sp |
532 | While nominally embeddable in other event loops, this feature is broken in |
566 | While nominally embeddable in other event loops, this feature is broken in |
533 | all kernel versions tested so far. |
567 | all kernel versions tested so far. |
534 | .Sp |
568 | .Sp |
535 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
569 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
536 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
570 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
537 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
571 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
538 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
572 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
539 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
573 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
540 | Kqueue deserves special mention, as at the time of this writing, it was |
574 | Kqueue deserves special mention, as at the time of this writing, it |
541 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
575 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
542 | anything but sockets and pipes, except on Darwin, where of course it's |
576 | with anything but sockets and pipes, except on Darwin, where of course |
543 | completely useless). For this reason it's not being \*(L"auto-detected\*(R" unless |
577 | it's completely useless). Unlike epoll, however, whose brokenness |
544 | you explicitly specify it in the flags (i.e. using \f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or |
578 | is by design, these kqueue bugs can (and eventually will) be fixed |
545 | libev was compiled on a known-to-be-good (\-enough) system like NetBSD. |
579 | without \s-1API\s0 changes to existing programs. For this reason it's not being |
|
|
580 | \&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using |
|
|
581 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
|
|
582 | system like NetBSD. |
546 | .Sp |
583 | .Sp |
547 | You still can embed kqueue into a normal poll or select backend and use it |
584 | You still can embed kqueue into a normal poll or select backend and use it |
548 | only for sockets (after having made sure that sockets work with kqueue on |
585 | only for sockets (after having made sure that sockets work with kqueue on |
549 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
586 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
550 | .Sp |
587 | .Sp |
551 | It scales in the same way as the epoll backend, but the interface to the |
588 | It scales in the same way as the epoll backend, but the interface to the |
552 | kernel is more efficient (which says nothing about its actual speed, of |
589 | kernel is more efficient (which says nothing about its actual speed, of |
553 | course). While stopping, setting and starting an I/O watcher does never |
590 | course). While stopping, setting and starting an I/O watcher does never |
554 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
591 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
555 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it |
592 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but |
556 | drops fds silently in similarly hard-to-detect cases. |
593 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
594 | cases |
557 | .Sp |
595 | .Sp |
558 | This backend usually performs well under most conditions. |
596 | This backend usually performs well under most conditions. |
559 | .Sp |
597 | .Sp |
560 | While nominally embeddable in other event loops, this doesn't work |
598 | While nominally embeddable in other event loops, this doesn't work |
561 | everywhere, so you might need to test for this. And since it is broken |
599 | everywhere, so you might need to test for this. And since it is broken |
562 | almost everywhere, you should only use it when you have a lot of sockets |
600 | almost everywhere, you should only use it when you have a lot of sockets |
563 | (for which it usually works), by embedding it into another event loop |
601 | (for which it usually works), by embedding it into another event loop |
564 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and, did I mention it, |
602 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course |
565 | using it only for sockets. |
603 | also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets. |
566 | .Sp |
604 | .Sp |
567 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
605 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
568 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with |
606 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with |
569 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
607 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
570 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
608 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
… | |
… | |
590 | might perform better. |
628 | might perform better. |
591 | .Sp |
629 | .Sp |
592 | On the positive side, with the exception of the spurious readiness |
630 | On the positive side, with the exception of the spurious readiness |
593 | notifications, this backend actually performed fully to specification |
631 | notifications, this backend actually performed fully to specification |
594 | in all tests and is fully embeddable, which is a rare feat among the |
632 | in all tests and is fully embeddable, which is a rare feat among the |
595 | OS-specific backends. |
633 | OS-specific backends (I vastly prefer correctness over speed hacks). |
596 | .Sp |
634 | .Sp |
597 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
635 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
598 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
636 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
599 | .ie n .IP """EVBACKEND_ALL""" 4 |
637 | .ie n .IP """EVBACKEND_ALL""" 4 |
600 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
638 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
… | |
… | |
660 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
698 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
661 | calling this function, or cope with the fact afterwards (which is usually |
699 | calling this function, or cope with the fact afterwards (which is usually |
662 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
700 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
663 | for example). |
701 | for example). |
664 | .Sp |
702 | .Sp |
665 | Note that certain global state, such as signal state, will not be freed by |
703 | Note that certain global state, such as signal state (and installed signal |
666 | this function, and related watchers (such as signal and child watchers) |
704 | handlers), will not be freed by this function, and related watchers (such |
667 | would need to be stopped manually. |
705 | as signal and child watchers) would need to be stopped manually. |
668 | .Sp |
706 | .Sp |
669 | In general it is not advisable to call this function except in the |
707 | In general it is not advisable to call this function except in the |
670 | rare occasion where you really need to free e.g. the signal handling |
708 | rare occasion where you really need to free e.g. the signal handling |
671 | pipe fds. If you need dynamically allocated loops it is better to use |
709 | pipe fds. If you need dynamically allocated loops it is better to use |
672 | \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
710 | \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
… | |
… | |
733 | This function is rarely useful, but when some event callback runs for a |
771 | This function is rarely useful, but when some event callback runs for a |
734 | very long time without entering the event loop, updating libev's idea of |
772 | very long time without entering the event loop, updating libev's idea of |
735 | the current time is a good idea. |
773 | the current time is a good idea. |
736 | .Sp |
774 | .Sp |
737 | See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
775 | See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
|
|
776 | .IP "ev_suspend (loop)" 4 |
|
|
777 | .IX Item "ev_suspend (loop)" |
|
|
778 | .PD 0 |
|
|
779 | .IP "ev_resume (loop)" 4 |
|
|
780 | .IX Item "ev_resume (loop)" |
|
|
781 | .PD |
|
|
782 | These two functions suspend and resume a loop, for use when the loop is |
|
|
783 | not used for a while and timeouts should not be processed. |
|
|
784 | .Sp |
|
|
785 | A typical use case would be an interactive program such as a game: When |
|
|
786 | the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it |
|
|
787 | would be best to handle timeouts as if no time had actually passed while |
|
|
788 | the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR |
|
|
789 | in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling |
|
|
790 | \&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing. |
|
|
791 | .Sp |
|
|
792 | Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend |
|
|
793 | between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers |
|
|
794 | will be rescheduled (that is, they will lose any events that would have |
|
|
795 | occured while suspended). |
|
|
796 | .Sp |
|
|
797 | After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the |
|
|
798 | given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR |
|
|
799 | without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR. |
|
|
800 | .Sp |
|
|
801 | Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the |
|
|
802 | event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). |
738 | .IP "ev_loop (loop, int flags)" 4 |
803 | .IP "ev_loop (loop, int flags)" 4 |
739 | .IX Item "ev_loop (loop, int flags)" |
804 | .IX Item "ev_loop (loop, int flags)" |
740 | Finally, this is it, the event handler. This function usually is called |
805 | Finally, this is it, the event handler. This function usually is called |
741 | after you initialised all your watchers and you want to start handling |
806 | after you initialised all your watchers and you want to start handling |
742 | events. |
807 | events. |
… | |
… | |
757 | the loop. |
822 | the loop. |
758 | .Sp |
823 | .Sp |
759 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
824 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
760 | necessary) and will handle those and any already outstanding ones. It |
825 | necessary) and will handle those and any already outstanding ones. It |
761 | will block your process until at least one new event arrives (which could |
826 | will block your process until at least one new event arrives (which could |
762 | be an event internal to libev itself, so there is no guarentee that a |
827 | be an event internal to libev itself, so there is no guarantee that a |
763 | user-registered callback will be called), and will return after one |
828 | user-registered callback will be called), and will return after one |
764 | iteration of the loop. |
829 | iteration of the loop. |
765 | .Sp |
830 | .Sp |
766 | This is useful if you are waiting for some external event in conjunction |
831 | This is useful if you are waiting for some external event in conjunction |
767 | with something not expressible using other libev watchers (i.e. "roll your |
832 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
813 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
878 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
814 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
879 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
815 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
880 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
816 | .Sp |
881 | .Sp |
817 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
882 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
|
|
883 | .Sp |
|
|
884 | It is safe to call \f(CW\*(C`ev_unloop\*(C'\fR from otuside any \f(CW\*(C`ev_loop\*(C'\fR calls. |
818 | .IP "ev_ref (loop)" 4 |
885 | .IP "ev_ref (loop)" 4 |
819 | .IX Item "ev_ref (loop)" |
886 | .IX Item "ev_ref (loop)" |
820 | .PD 0 |
887 | .PD 0 |
821 | .IP "ev_unref (loop)" 4 |
888 | .IP "ev_unref (loop)" 4 |
822 | .IX Item "ev_unref (loop)" |
889 | .IX Item "ev_unref (loop)" |
… | |
… | |
827 | .Sp |
894 | .Sp |
828 | If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR |
895 | If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR |
829 | from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before |
896 | from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before |
830 | stopping it. |
897 | stopping it. |
831 | .Sp |
898 | .Sp |
832 | As an example, libev itself uses this for its internal signal pipe: It is |
899 | As an example, libev itself uses this for its internal signal pipe: It |
833 | not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting |
900 | is not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
834 | if no event watchers registered by it are active. It is also an excellent |
901 | exiting if no event watchers registered by it are active. It is also an |
835 | way to do this for generic recurring timers or from within third-party |
902 | excellent way to do this for generic recurring timers or from within |
836 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR |
903 | third-party libraries. Just remember to \fIunref after start\fR and \fIref |
837 | (but only if the watcher wasn't active before, or was active before, |
904 | before stop\fR (but only if the watcher wasn't active before, or was active |
838 | respectively). |
905 | before, respectively. Note also that libev might stop watchers itself |
|
|
906 | (e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR |
|
|
907 | in the callback). |
839 | .Sp |
908 | .Sp |
840 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
909 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
841 | running when nothing else is active. |
910 | running when nothing else is active. |
842 | .Sp |
911 | .Sp |
843 | .Vb 4 |
912 | .Vb 4 |
844 | \& struct ev_signal exitsig; |
913 | \& ev_signal exitsig; |
845 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
914 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
846 | \& ev_signal_start (loop, &exitsig); |
915 | \& ev_signal_start (loop, &exitsig); |
847 | \& evf_unref (loop); |
916 | \& evf_unref (loop); |
848 | .Ve |
917 | .Ve |
849 | .Sp |
918 | .Sp |
… | |
… | |
900 | reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
969 | reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
901 | they fire on, say, one-second boundaries only. |
970 | they fire on, say, one-second boundaries only. |
902 | .IP "ev_loop_verify (loop)" 4 |
971 | .IP "ev_loop_verify (loop)" 4 |
903 | .IX Item "ev_loop_verify (loop)" |
972 | .IX Item "ev_loop_verify (loop)" |
904 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
973 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
905 | compiled in. which is the default for non-minimal builds. It tries to go |
974 | compiled in, which is the default for non-minimal builds. It tries to go |
906 | through all internal structures and checks them for validity. If anything |
975 | through all internal structures and checks them for validity. If anything |
907 | is found to be inconsistent, it will print an error message to standard |
976 | is found to be inconsistent, it will print an error message to standard |
908 | error and call \f(CW\*(C`abort ()\*(C'\fR. |
977 | error and call \f(CW\*(C`abort ()\*(C'\fR. |
909 | .Sp |
978 | .Sp |
910 | This can be used to catch bugs inside libev itself: under normal |
979 | This can be used to catch bugs inside libev itself: under normal |
911 | circumstances, this function will never abort as of course libev keeps its |
980 | circumstances, this function will never abort as of course libev keeps its |
912 | data structures consistent. |
981 | data structures consistent. |
913 | .SH "ANATOMY OF A WATCHER" |
982 | .SH "ANATOMY OF A WATCHER" |
914 | .IX Header "ANATOMY OF A WATCHER" |
983 | .IX Header "ANATOMY OF A WATCHER" |
|
|
984 | In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the |
|
|
985 | watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer |
|
|
986 | watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers. |
|
|
987 | .PP |
915 | A watcher is a structure that you create and register to record your |
988 | A watcher is a structure that you create and register to record your |
916 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
989 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
917 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
990 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
918 | .PP |
991 | .PP |
919 | .Vb 5 |
992 | .Vb 5 |
920 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
993 | \& static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
921 | \& { |
994 | \& { |
922 | \& ev_io_stop (w); |
995 | \& ev_io_stop (w); |
923 | \& ev_unloop (loop, EVUNLOOP_ALL); |
996 | \& ev_unloop (loop, EVUNLOOP_ALL); |
924 | \& } |
997 | \& } |
925 | \& |
998 | \& |
926 | \& struct ev_loop *loop = ev_default_loop (0); |
999 | \& struct ev_loop *loop = ev_default_loop (0); |
|
|
1000 | \& |
927 | \& struct ev_io stdin_watcher; |
1001 | \& ev_io stdin_watcher; |
|
|
1002 | \& |
928 | \& ev_init (&stdin_watcher, my_cb); |
1003 | \& ev_init (&stdin_watcher, my_cb); |
929 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1004 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
930 | \& ev_io_start (loop, &stdin_watcher); |
1005 | \& ev_io_start (loop, &stdin_watcher); |
|
|
1006 | \& |
931 | \& ev_loop (loop, 0); |
1007 | \& ev_loop (loop, 0); |
932 | .Ve |
1008 | .Ve |
933 | .PP |
1009 | .PP |
934 | As you can see, you are responsible for allocating the memory for your |
1010 | As you can see, you are responsible for allocating the memory for your |
935 | watcher structures (and it is usually a bad idea to do this on the stack, |
1011 | watcher structures (and it is \fIusually\fR a bad idea to do this on the |
936 | although this can sometimes be quite valid). |
1012 | stack). |
|
|
1013 | .PP |
|
|
1014 | Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR |
|
|
1015 | or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs). |
937 | .PP |
1016 | .PP |
938 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
1017 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
939 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
1018 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
940 | callback gets invoked each time the event occurs (or, in the case of I/O |
1019 | callback gets invoked each time the event occurs (or, in the case of I/O |
941 | watchers, each time the event loop detects that the file descriptor given |
1020 | watchers, each time the event loop detects that the file descriptor given |
942 | is readable and/or writable). |
1021 | is readable and/or writable). |
943 | .PP |
1022 | .PP |
944 | Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
1023 | Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR |
945 | with arguments specific to this watcher type. There is also a macro |
1024 | macro to configure it, with arguments specific to the watcher type. There |
946 | to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init |
1025 | is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR. |
947 | (watcher *, callback, ...)\*(C'\fR. |
|
|
948 | .PP |
1026 | .PP |
949 | To make the watcher actually watch out for events, you have to start it |
1027 | To make the watcher actually watch out for events, you have to start it |
950 | with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher |
1028 | with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher |
951 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
1029 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
952 | corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
1030 | corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. |
953 | .PP |
1031 | .PP |
954 | As long as your watcher is active (has been started but not stopped) you |
1032 | As long as your watcher is active (has been started but not stopped) you |
955 | must not touch the values stored in it. Most specifically you must never |
1033 | must not touch the values stored in it. Most specifically you must never |
956 | reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. |
1034 | reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. |
957 | .PP |
1035 | .PP |
958 | Each and every callback receives the event loop pointer as first, the |
1036 | Each and every callback receives the event loop pointer as first, the |
959 | registered watcher structure as second, and a bitset of received events as |
1037 | registered watcher structure as second, and a bitset of received events as |
960 | third argument. |
1038 | third argument. |
961 | .PP |
1039 | .PP |
… | |
… | |
1022 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
1100 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
1023 | .ie n .IP """EV_ASYNC""" 4 |
1101 | .ie n .IP """EV_ASYNC""" 4 |
1024 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
1102 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
1025 | .IX Item "EV_ASYNC" |
1103 | .IX Item "EV_ASYNC" |
1026 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
1104 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
|
|
1105 | .ie n .IP """EV_CUSTOM""" 4 |
|
|
1106 | .el .IP "\f(CWEV_CUSTOM\fR" 4 |
|
|
1107 | .IX Item "EV_CUSTOM" |
|
|
1108 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1109 | by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR). |
1027 | .ie n .IP """EV_ERROR""" 4 |
1110 | .ie n .IP """EV_ERROR""" 4 |
1028 | .el .IP "\f(CWEV_ERROR\fR" 4 |
1111 | .el .IP "\f(CWEV_ERROR\fR" 4 |
1029 | .IX Item "EV_ERROR" |
1112 | .IX Item "EV_ERROR" |
1030 | An unspecified error has occurred, the watcher has been stopped. This might |
1113 | An unspecified error has occurred, the watcher has been stopped. This might |
1031 | happen because the watcher could not be properly started because libev |
1114 | happen because the watcher could not be properly started because libev |
1032 | ran out of memory, a file descriptor was found to be closed or any other |
1115 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1116 | problem. Libev considers these application bugs. |
|
|
1117 | .Sp |
1033 | problem. You best act on it by reporting the problem and somehow coping |
1118 | You best act on it by reporting the problem and somehow coping with the |
1034 | with the watcher being stopped. |
1119 | watcher being stopped. Note that well-written programs should not receive |
|
|
1120 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1121 | bug in your program. |
1035 | .Sp |
1122 | .Sp |
1036 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
1123 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
1037 | example it might indicate that a fd is readable or writable, and if your |
1124 | example it might indicate that a fd is readable or writable, and if your |
1038 | callbacks is well-written it can just attempt the operation and cope with |
1125 | callbacks is well-written it can just attempt the operation and cope with |
1039 | the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
1126 | the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
1040 | programs, though, as the fd could already be closed and reused for another |
1127 | programs, though, as the fd could already be closed and reused for another |
1041 | thing, so beware. |
1128 | thing, so beware. |
1042 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
1129 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
1043 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
1130 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
1044 | In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
|
|
1045 | e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
|
|
1046 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
1131 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
1047 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
1132 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
1048 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
1133 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
1049 | This macro initialises the generic portion of a watcher. The contents |
1134 | This macro initialises the generic portion of a watcher. The contents |
1050 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
1135 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
… | |
… | |
1054 | which rolls both calls into one. |
1139 | which rolls both calls into one. |
1055 | .Sp |
1140 | .Sp |
1056 | You can reinitialise a watcher at any time as long as it has been stopped |
1141 | You can reinitialise a watcher at any time as long as it has been stopped |
1057 | (or never started) and there are no pending events outstanding. |
1142 | (or never started) and there are no pending events outstanding. |
1058 | .Sp |
1143 | .Sp |
1059 | The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
1144 | The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
1060 | int revents)\*(C'\fR. |
1145 | int revents)\*(C'\fR. |
1061 | .Sp |
1146 | .Sp |
1062 | Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
1147 | Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
1063 | .Sp |
1148 | .Sp |
1064 | .Vb 3 |
1149 | .Vb 3 |
… | |
… | |
1104 | \& ev_io_start (EV_DEFAULT_UC, &w); |
1189 | \& ev_io_start (EV_DEFAULT_UC, &w); |
1105 | .Ve |
1190 | .Ve |
1106 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1191 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1107 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1192 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1108 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1193 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1109 | Stops the given watcher again (if active) and clears the pending |
1194 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1195 | the watcher was active or not). |
|
|
1196 | .Sp |
1110 | status. It is possible that stopped watchers are pending (for example, |
1197 | It is possible that stopped watchers are pending \- for example, |
1111 | non-repeating timers are being stopped when they become pending), but |
1198 | non-repeating timers are being stopped when they become pending \- but |
1112 | \&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If |
1199 | calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor |
1113 | you want to free or reuse the memory used by the watcher it is therefore a |
1200 | pending. If you want to free or reuse the memory used by the watcher it is |
1114 | good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1201 | therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1115 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1202 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1116 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1203 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1117 | Returns a true value iff the watcher is active (i.e. it has been started |
1204 | Returns a true value iff the watcher is active (i.e. it has been started |
1118 | and not yet been stopped). As long as a watcher is active you must not modify |
1205 | and not yet been stopped). As long as a watcher is active you must not modify |
1119 | it. |
1206 | it. |
… | |
… | |
1142 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1229 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1143 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1230 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1144 | before watchers with lower priority, but priority will not keep watchers |
1231 | before watchers with lower priority, but priority will not keep watchers |
1145 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1232 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1146 | .Sp |
1233 | .Sp |
1147 | This means that priorities are \fIonly\fR used for ordering callback |
|
|
1148 | invocation after new events have been received. This is useful, for |
|
|
1149 | example, to reduce latency after idling, or more often, to bind two |
|
|
1150 | watchers on the same event and make sure one is called first. |
|
|
1151 | .Sp |
|
|
1152 | If you need to suppress invocation when higher priority events are pending |
1234 | If you need to suppress invocation when higher priority events are pending |
1153 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1235 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1154 | .Sp |
1236 | .Sp |
1155 | You \fImust not\fR change the priority of a watcher as long as it is active or |
1237 | You \fImust not\fR change the priority of a watcher as long as it is active or |
1156 | pending. |
1238 | pending. |
1157 | .Sp |
1239 | .Sp |
|
|
1240 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
|
|
1241 | fine, as long as you do not mind that the priority value you query might |
|
|
1242 | or might not have been clamped to the valid range. |
|
|
1243 | .Sp |
1158 | The default priority used by watchers when no priority has been set is |
1244 | The default priority used by watchers when no priority has been set is |
1159 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1245 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1160 | .Sp |
1246 | .Sp |
1161 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
1247 | See \*(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\*(R", below, for a more thorough treatment of |
1162 | fine, as long as you do not mind that the priority value you query might |
1248 | priorities. |
1163 | or might not have been adjusted to be within valid range. |
|
|
1164 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1249 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1165 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1250 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1166 | Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
1251 | Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
1167 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1252 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1168 | can deal with that fact, as both are simply passed through to the |
1253 | can deal with that fact, as both are simply passed through to the |
… | |
… | |
1185 | data: |
1270 | data: |
1186 | .PP |
1271 | .PP |
1187 | .Vb 7 |
1272 | .Vb 7 |
1188 | \& struct my_io |
1273 | \& struct my_io |
1189 | \& { |
1274 | \& { |
1190 | \& struct ev_io io; |
1275 | \& ev_io io; |
1191 | \& int otherfd; |
1276 | \& int otherfd; |
1192 | \& void *somedata; |
1277 | \& void *somedata; |
1193 | \& struct whatever *mostinteresting; |
1278 | \& struct whatever *mostinteresting; |
1194 | \& }; |
1279 | \& }; |
1195 | \& |
1280 | \& |
… | |
… | |
1200 | .PP |
1285 | .PP |
1201 | And since your callback will be called with a pointer to the watcher, you |
1286 | And since your callback will be called with a pointer to the watcher, you |
1202 | can cast it back to your own type: |
1287 | can cast it back to your own type: |
1203 | .PP |
1288 | .PP |
1204 | .Vb 5 |
1289 | .Vb 5 |
1205 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1290 | \& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1206 | \& { |
1291 | \& { |
1207 | \& struct my_io *w = (struct my_io *)w_; |
1292 | \& struct my_io *w = (struct my_io *)w_; |
1208 | \& ... |
1293 | \& ... |
1209 | \& } |
1294 | \& } |
1210 | .Ve |
1295 | .Ve |
… | |
… | |
1232 | .PP |
1317 | .PP |
1233 | .Vb 1 |
1318 | .Vb 1 |
1234 | \& #include <stddef.h> |
1319 | \& #include <stddef.h> |
1235 | \& |
1320 | \& |
1236 | \& static void |
1321 | \& static void |
1237 | \& t1_cb (EV_P_ struct ev_timer *w, int revents) |
1322 | \& t1_cb (EV_P_ ev_timer *w, int revents) |
1238 | \& { |
1323 | \& { |
1239 | \& struct my_biggy big = (struct my_biggy * |
1324 | \& struct my_biggy big = (struct my_biggy * |
1240 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
1325 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
1241 | \& } |
1326 | \& } |
1242 | \& |
1327 | \& |
1243 | \& static void |
1328 | \& static void |
1244 | \& t2_cb (EV_P_ struct ev_timer *w, int revents) |
1329 | \& t2_cb (EV_P_ ev_timer *w, int revents) |
1245 | \& { |
1330 | \& { |
1246 | \& struct my_biggy big = (struct my_biggy * |
1331 | \& struct my_biggy big = (struct my_biggy * |
1247 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
1332 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
1248 | \& } |
1333 | \& } |
1249 | .Ve |
1334 | .Ve |
|
|
1335 | .Sh "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0" |
|
|
1336 | .IX Subsection "WATCHER PRIORITY MODELS" |
|
|
1337 | Many event loops support \fIwatcher priorities\fR, which are usually small |
|
|
1338 | integers that influence the ordering of event callback invocation |
|
|
1339 | between watchers in some way, all else being equal. |
|
|
1340 | .PP |
|
|
1341 | In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its |
|
|
1342 | description for the more technical details such as the actual priority |
|
|
1343 | range. |
|
|
1344 | .PP |
|
|
1345 | There are two common ways how these these priorities are being interpreted |
|
|
1346 | by event loops: |
|
|
1347 | .PP |
|
|
1348 | In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation |
|
|
1349 | of lower priority watchers, which means as long as higher priority |
|
|
1350 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1351 | .PP |
|
|
1352 | The less common only-for-ordering model uses priorities solely to order |
|
|
1353 | callback invocation within a single event loop iteration: Higher priority |
|
|
1354 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1355 | before polling for new events. |
|
|
1356 | .PP |
|
|
1357 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1358 | except for idle watchers (which use the lock-out model). |
|
|
1359 | .PP |
|
|
1360 | The rationale behind this is that implementing the lock-out model for |
|
|
1361 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1362 | libraries will just poll for the same events again and again as long as |
|
|
1363 | their callbacks have not been executed, which is very inefficient in the |
|
|
1364 | common case of one high-priority watcher locking out a mass of lower |
|
|
1365 | priority ones. |
|
|
1366 | .PP |
|
|
1367 | Static (ordering) priorities are most useful when you have two or more |
|
|
1368 | watchers handling the same resource: a typical usage example is having an |
|
|
1369 | \&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle |
|
|
1370 | timeouts. Under load, data might be received while the program handles |
|
|
1371 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1372 | handler will be executed before checking for data. In that case, giving |
|
|
1373 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1374 | handled first even under adverse conditions (which is usually, but not |
|
|
1375 | always, what you want). |
|
|
1376 | .PP |
|
|
1377 | Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers |
|
|
1378 | will only be executed when no same or higher priority watchers have |
|
|
1379 | received events, they can be used to implement the \*(L"lock-out\*(R" model when |
|
|
1380 | required. |
|
|
1381 | .PP |
|
|
1382 | For example, to emulate how many other event libraries handle priorities, |
|
|
1383 | you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in |
|
|
1384 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1385 | processing is done in the idle watcher callback. This causes libev to |
|
|
1386 | continously poll and process kernel event data for the watcher, but when |
|
|
1387 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1388 | workable. |
|
|
1389 | .PP |
|
|
1390 | Usually, however, the lock-out model implemented that way will perform |
|
|
1391 | miserably under the type of load it was designed to handle. In that case, |
|
|
1392 | it might be preferable to stop the real watcher before starting the |
|
|
1393 | idle watcher, so the kernel will not have to process the event in case |
|
|
1394 | the actual processing will be delayed for considerable time. |
|
|
1395 | .PP |
|
|
1396 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1397 | priority than the default, and which should only process data when no |
|
|
1398 | other events are pending: |
|
|
1399 | .PP |
|
|
1400 | .Vb 2 |
|
|
1401 | \& ev_idle idle; // actual processing watcher |
|
|
1402 | \& ev_io io; // actual event watcher |
|
|
1403 | \& |
|
|
1404 | \& static void |
|
|
1405 | \& io_cb (EV_P_ ev_io *w, int revents) |
|
|
1406 | \& { |
|
|
1407 | \& // stop the I/O watcher, we received the event, but |
|
|
1408 | \& // are not yet ready to handle it. |
|
|
1409 | \& ev_io_stop (EV_A_ w); |
|
|
1410 | \& |
|
|
1411 | \& // start the idle watcher to ahndle the actual event. |
|
|
1412 | \& // it will not be executed as long as other watchers |
|
|
1413 | \& // with the default priority are receiving events. |
|
|
1414 | \& ev_idle_start (EV_A_ &idle); |
|
|
1415 | \& } |
|
|
1416 | \& |
|
|
1417 | \& static void |
|
|
1418 | \& idle\-cb (EV_P_ ev_idle *w, int revents) |
|
|
1419 | \& { |
|
|
1420 | \& // actual processing |
|
|
1421 | \& read (STDIN_FILENO, ...); |
|
|
1422 | \& |
|
|
1423 | \& // have to start the I/O watcher again, as |
|
|
1424 | \& // we have handled the event |
|
|
1425 | \& ev_io_start (EV_P_ &io); |
|
|
1426 | \& } |
|
|
1427 | \& |
|
|
1428 | \& // initialisation |
|
|
1429 | \& ev_idle_init (&idle, idle_cb); |
|
|
1430 | \& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1431 | \& ev_io_start (EV_DEFAULT_ &io); |
|
|
1432 | .Ve |
|
|
1433 | .PP |
|
|
1434 | In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that |
|
|
1435 | low-priority connections can not be locked out forever under load. This |
|
|
1436 | enables your program to keep a lower latency for important connections |
|
|
1437 | during short periods of high load, while not completely locking out less |
|
|
1438 | important ones. |
1250 | .SH "WATCHER TYPES" |
1439 | .SH "WATCHER TYPES" |
1251 | .IX Header "WATCHER TYPES" |
1440 | .IX Header "WATCHER TYPES" |
1252 | This section describes each watcher in detail, but will not repeat |
1441 | This section describes each watcher in detail, but will not repeat |
1253 | information given in the last section. Any initialisation/set macros, |
1442 | information given in the last section. Any initialisation/set macros, |
1254 | functions and members specific to the watcher type are explained. |
1443 | functions and members specific to the watcher type are explained. |
… | |
… | |
1277 | descriptors to non-blocking mode is also usually a good idea (but not |
1466 | descriptors to non-blocking mode is also usually a good idea (but not |
1278 | required if you know what you are doing). |
1467 | required if you know what you are doing). |
1279 | .PP |
1468 | .PP |
1280 | If you cannot use non-blocking mode, then force the use of a |
1469 | If you cannot use non-blocking mode, then force the use of a |
1281 | known-to-be-good backend (at the time of this writing, this includes only |
1470 | known-to-be-good backend (at the time of this writing, this includes only |
1282 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
1471 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). The same applies to file |
|
|
1472 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1473 | files) \- libev doesn't guarentee any specific behaviour in that case. |
1283 | .PP |
1474 | .PP |
1284 | Another thing you have to watch out for is that it is quite easy to |
1475 | Another thing you have to watch out for is that it is quite easy to |
1285 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
1476 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
1286 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1477 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1287 | because there is no data. Not only are some backends known to create a |
1478 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1383 | readable, but only once. Since it is likely line-buffered, you could |
1574 | readable, but only once. Since it is likely line-buffered, you could |
1384 | attempt to read a whole line in the callback. |
1575 | attempt to read a whole line in the callback. |
1385 | .PP |
1576 | .PP |
1386 | .Vb 6 |
1577 | .Vb 6 |
1387 | \& static void |
1578 | \& static void |
1388 | \& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1579 | \& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1389 | \& { |
1580 | \& { |
1390 | \& ev_io_stop (loop, w); |
1581 | \& ev_io_stop (loop, w); |
1391 | \& .. read from stdin here (or from w\->fd) and handle any I/O errors |
1582 | \& .. read from stdin here (or from w\->fd) and handle any I/O errors |
1392 | \& } |
1583 | \& } |
1393 | \& |
1584 | \& |
1394 | \& ... |
1585 | \& ... |
1395 | \& struct ev_loop *loop = ev_default_init (0); |
1586 | \& struct ev_loop *loop = ev_default_init (0); |
1396 | \& struct ev_io stdin_readable; |
1587 | \& ev_io stdin_readable; |
1397 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1588 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1398 | \& ev_io_start (loop, &stdin_readable); |
1589 | \& ev_io_start (loop, &stdin_readable); |
1399 | \& ev_loop (loop, 0); |
1590 | \& ev_loop (loop, 0); |
1400 | .Ve |
1591 | .Ve |
1401 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
1592 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
… | |
… | |
1409 | year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
1600 | year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
1410 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1601 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1411 | monotonic clock option helps a lot here). |
1602 | monotonic clock option helps a lot here). |
1412 | .PP |
1603 | .PP |
1413 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
1604 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
1414 | passed, but if multiple timers become ready during the same loop iteration |
1605 | passed (not \fIat\fR, so on systems with very low-resolution clocks this |
1415 | then order of execution is undefined. |
1606 | might introduce a small delay). If multiple timers become ready during the |
|
|
1607 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1608 | before ones with later time-out values (but this is no longer true when a |
|
|
1609 | callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively). |
|
|
1610 | .PP |
|
|
1611 | \fIBe smart about timeouts\fR |
|
|
1612 | .IX Subsection "Be smart about timeouts" |
|
|
1613 | .PP |
|
|
1614 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1615 | recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs, |
|
|
1616 | you want to raise some error after a while. |
|
|
1617 | .PP |
|
|
1618 | What follows are some ways to handle this problem, from obvious and |
|
|
1619 | inefficient to smart and efficient. |
|
|
1620 | .PP |
|
|
1621 | In the following, a 60 second activity timeout is assumed \- a timeout that |
|
|
1622 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1623 | data or other life sign was received). |
|
|
1624 | .IP "1. Use a timer and stop, reinitialise and start it on activity." 4 |
|
|
1625 | .IX Item "1. Use a timer and stop, reinitialise and start it on activity." |
|
|
1626 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1627 | start the watcher: |
|
|
1628 | .Sp |
|
|
1629 | .Vb 2 |
|
|
1630 | \& ev_timer_init (timer, callback, 60., 0.); |
|
|
1631 | \& ev_timer_start (loop, timer); |
|
|
1632 | .Ve |
|
|
1633 | .Sp |
|
|
1634 | Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it |
|
|
1635 | and start it again: |
|
|
1636 | .Sp |
|
|
1637 | .Vb 3 |
|
|
1638 | \& ev_timer_stop (loop, timer); |
|
|
1639 | \& ev_timer_set (timer, 60., 0.); |
|
|
1640 | \& ev_timer_start (loop, timer); |
|
|
1641 | .Ve |
|
|
1642 | .Sp |
|
|
1643 | This is relatively simple to implement, but means that each time there is |
|
|
1644 | some activity, libev will first have to remove the timer from its internal |
|
|
1645 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1646 | still not a constant-time operation. |
|
|
1647 | .ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4 |
|
|
1648 | .el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4 |
|
|
1649 | .IX Item "2. Use a timer and re-start it with ev_timer_again inactivity." |
|
|
1650 | This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of |
|
|
1651 | \&\f(CW\*(C`ev_timer_start\*(C'\fR. |
|
|
1652 | .Sp |
|
|
1653 | To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value |
|
|
1654 | of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you |
|
|
1655 | successfully read or write some data. If you go into an idle state where |
|
|
1656 | you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR |
|
|
1657 | the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be. |
|
|
1658 | .Sp |
|
|
1659 | That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the |
|
|
1660 | \&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR |
|
|
1661 | member and \f(CW\*(C`ev_timer_again\*(C'\fR. |
|
|
1662 | .Sp |
|
|
1663 | At start: |
|
|
1664 | .Sp |
|
|
1665 | .Vb 3 |
|
|
1666 | \& ev_timer_init (timer, callback); |
|
|
1667 | \& timer\->repeat = 60.; |
|
|
1668 | \& ev_timer_again (loop, timer); |
|
|
1669 | .Ve |
|
|
1670 | .Sp |
|
|
1671 | Each time there is some activity: |
|
|
1672 | .Sp |
|
|
1673 | .Vb 1 |
|
|
1674 | \& ev_timer_again (loop, timer); |
|
|
1675 | .Ve |
|
|
1676 | .Sp |
|
|
1677 | It is even possible to change the time-out on the fly, regardless of |
|
|
1678 | whether the watcher is active or not: |
|
|
1679 | .Sp |
|
|
1680 | .Vb 2 |
|
|
1681 | \& timer\->repeat = 30.; |
|
|
1682 | \& ev_timer_again (loop, timer); |
|
|
1683 | .Ve |
|
|
1684 | .Sp |
|
|
1685 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1686 | you want to modify its timeout value, as libev does not have to completely |
|
|
1687 | remove and re-insert the timer from/into its internal data structure. |
|
|
1688 | .Sp |
|
|
1689 | It is, however, even simpler than the \*(L"obvious\*(R" way to do it. |
|
|
1690 | .IP "3. Let the timer time out, but then re-arm it as required." 4 |
|
|
1691 | .IX Item "3. Let the timer time out, but then re-arm it as required." |
|
|
1692 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1693 | relatively long compared to the intervals between other activity \- in |
|
|
1694 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1695 | associated activity resets. |
|
|
1696 | .Sp |
|
|
1697 | In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
|
|
1698 | but remember the time of last activity, and check for a real timeout only |
|
|
1699 | within the callback: |
|
|
1700 | .Sp |
|
|
1701 | .Vb 1 |
|
|
1702 | \& ev_tstamp last_activity; // time of last activity |
|
|
1703 | \& |
|
|
1704 | \& static void |
|
|
1705 | \& callback (EV_P_ ev_timer *w, int revents) |
|
|
1706 | \& { |
|
|
1707 | \& ev_tstamp now = ev_now (EV_A); |
|
|
1708 | \& ev_tstamp timeout = last_activity + 60.; |
|
|
1709 | \& |
|
|
1710 | \& // if last_activity + 60. is older than now, we did time out |
|
|
1711 | \& if (timeout < now) |
|
|
1712 | \& { |
|
|
1713 | \& // timeout occured, take action |
|
|
1714 | \& } |
|
|
1715 | \& else |
|
|
1716 | \& { |
|
|
1717 | \& // callback was invoked, but there was some activity, re\-arm |
|
|
1718 | \& // the watcher to fire in last_activity + 60, which is |
|
|
1719 | \& // guaranteed to be in the future, so "again" is positive: |
|
|
1720 | \& w\->repeat = timeout \- now; |
|
|
1721 | \& ev_timer_again (EV_A_ w); |
|
|
1722 | \& } |
|
|
1723 | \& } |
|
|
1724 | .Ve |
|
|
1725 | .Sp |
|
|
1726 | To summarise the callback: first calculate the real timeout (defined |
|
|
1727 | as \*(L"60 seconds after the last activity\*(R"), then check if that time has |
|
|
1728 | been reached, which means something \fIdid\fR, in fact, time out. Otherwise |
|
|
1729 | the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so |
|
|
1730 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1731 | a timeout then. |
|
|
1732 | .Sp |
|
|
1733 | Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the |
|
|
1734 | \&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running. |
|
|
1735 | .Sp |
|
|
1736 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1737 | minus half the average time between activity), but virtually no calls to |
|
|
1738 | libev to change the timeout. |
|
|
1739 | .Sp |
|
|
1740 | To start the timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR |
|
|
1741 | to the current time (meaning we just have some activity :), then call the |
|
|
1742 | callback, which will \*(L"do the right thing\*(R" and start the timer: |
|
|
1743 | .Sp |
|
|
1744 | .Vb 3 |
|
|
1745 | \& ev_timer_init (timer, callback); |
|
|
1746 | \& last_activity = ev_now (loop); |
|
|
1747 | \& callback (loop, timer, EV_TIMEOUT); |
|
|
1748 | .Ve |
|
|
1749 | .Sp |
|
|
1750 | And when there is some activity, simply store the current time in |
|
|
1751 | \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
|
|
1752 | .Sp |
|
|
1753 | .Vb 1 |
|
|
1754 | \& last_actiivty = ev_now (loop); |
|
|
1755 | .Ve |
|
|
1756 | .Sp |
|
|
1757 | This technique is slightly more complex, but in most cases where the |
|
|
1758 | time-out is unlikely to be triggered, much more efficient. |
|
|
1759 | .Sp |
|
|
1760 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1761 | callback :) \- just change the timeout and invoke the callback, which will |
|
|
1762 | fix things for you. |
|
|
1763 | .IP "4. Wee, just use a double-linked list for your timeouts." 4 |
|
|
1764 | .IX Item "4. Wee, just use a double-linked list for your timeouts." |
|
|
1765 | If there is not one request, but many thousands (millions...), all |
|
|
1766 | employing some kind of timeout with the same timeout value, then one can |
|
|
1767 | do even better: |
|
|
1768 | .Sp |
|
|
1769 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1770 | at the \fIend\fR of the list. |
|
|
1771 | .Sp |
|
|
1772 | Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of |
|
|
1773 | the list is expected to fire (for example, using the technique #3). |
|
|
1774 | .Sp |
|
|
1775 | When there is some activity, remove the timer from the list, recalculate |
|
|
1776 | the timeout, append it to the end of the list again, and make sure to |
|
|
1777 | update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list. |
|
|
1778 | .Sp |
|
|
1779 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1780 | starting, stopping and updating the timers, at the expense of a major |
|
|
1781 | complication, and having to use a constant timeout. The constant timeout |
|
|
1782 | ensures that the list stays sorted. |
|
|
1783 | .PP |
|
|
1784 | So which method the best? |
|
|
1785 | .PP |
|
|
1786 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1787 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1788 | better, and isn't very complicated either. In most case, choosing either |
|
|
1789 | one is fine, with #3 being better in typical situations. |
|
|
1790 | .PP |
|
|
1791 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1792 | rather complicated, but extremely efficient, something that really pays |
|
|
1793 | off after the first million or so of active timers, i.e. it's usually |
|
|
1794 | overkill :) |
1416 | .PP |
1795 | .PP |
1417 | \fIThe special problem of time updates\fR |
1796 | \fIThe special problem of time updates\fR |
1418 | .IX Subsection "The special problem of time updates" |
1797 | .IX Subsection "The special problem of time updates" |
1419 | .PP |
1798 | .PP |
1420 | Establishing the current time is a costly operation (it usually takes at |
1799 | Establishing the current time is a costly operation (it usually takes at |
… | |
… | |
1466 | If the timer is started but non-repeating, stop it (as if it timed out). |
1845 | If the timer is started but non-repeating, stop it (as if it timed out). |
1467 | .Sp |
1846 | .Sp |
1468 | If the timer is repeating, either start it if necessary (with the |
1847 | If the timer is repeating, either start it if necessary (with the |
1469 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
1848 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
1470 | .Sp |
1849 | .Sp |
1471 | This sounds a bit complicated, but here is a useful and typical |
1850 | This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
1472 | example: Imagine you have a \s-1TCP\s0 connection and you want a so-called idle |
1851 | usage example. |
1473 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1474 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1475 | configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call |
|
|
1476 | \&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If |
|
|
1477 | you go into an idle state where you do not expect data to travel on the |
|
|
1478 | socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will |
|
|
1479 | automatically restart it if need be. |
|
|
1480 | .Sp |
|
|
1481 | That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR |
|
|
1482 | altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR: |
|
|
1483 | .Sp |
|
|
1484 | .Vb 8 |
|
|
1485 | \& ev_timer_init (timer, callback, 0., 5.); |
|
|
1486 | \& ev_timer_again (loop, timer); |
|
|
1487 | \& ... |
|
|
1488 | \& timer\->again = 17.; |
|
|
1489 | \& ev_timer_again (loop, timer); |
|
|
1490 | \& ... |
|
|
1491 | \& timer\->again = 10.; |
|
|
1492 | \& ev_timer_again (loop, timer); |
|
|
1493 | .Ve |
|
|
1494 | .Sp |
|
|
1495 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1496 | you want to modify its timeout value. |
|
|
1497 | .Sp |
|
|
1498 | Note, however, that it is often even more efficient to remember the |
|
|
1499 | time of the last activity and let the timer time-out naturally. In the |
|
|
1500 | callback, you then check whether the time-out is real, or, if there was |
|
|
1501 | some activity, you reschedule the watcher to time-out in \*(L"last_activity + |
|
|
1502 | timeout \- ev_now ()\*(R" seconds. |
|
|
1503 | .IP "ev_tstamp repeat [read\-write]" 4 |
1852 | .IP "ev_tstamp repeat [read\-write]" 4 |
1504 | .IX Item "ev_tstamp repeat [read-write]" |
1853 | .IX Item "ev_tstamp repeat [read-write]" |
1505 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1854 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1506 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
1855 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
1507 | which is also when any modifications are taken into account. |
1856 | which is also when any modifications are taken into account. |
… | |
… | |
1511 | .PP |
1860 | .PP |
1512 | Example: Create a timer that fires after 60 seconds. |
1861 | Example: Create a timer that fires after 60 seconds. |
1513 | .PP |
1862 | .PP |
1514 | .Vb 5 |
1863 | .Vb 5 |
1515 | \& static void |
1864 | \& static void |
1516 | \& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1865 | \& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1517 | \& { |
1866 | \& { |
1518 | \& .. one minute over, w is actually stopped right here |
1867 | \& .. one minute over, w is actually stopped right here |
1519 | \& } |
1868 | \& } |
1520 | \& |
1869 | \& |
1521 | \& struct ev_timer mytimer; |
1870 | \& ev_timer mytimer; |
1522 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1871 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1523 | \& ev_timer_start (loop, &mytimer); |
1872 | \& ev_timer_start (loop, &mytimer); |
1524 | .Ve |
1873 | .Ve |
1525 | .PP |
1874 | .PP |
1526 | Example: Create a timeout timer that times out after 10 seconds of |
1875 | Example: Create a timeout timer that times out after 10 seconds of |
1527 | inactivity. |
1876 | inactivity. |
1528 | .PP |
1877 | .PP |
1529 | .Vb 5 |
1878 | .Vb 5 |
1530 | \& static void |
1879 | \& static void |
1531 | \& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1880 | \& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1532 | \& { |
1881 | \& { |
1533 | \& .. ten seconds without any activity |
1882 | \& .. ten seconds without any activity |
1534 | \& } |
1883 | \& } |
1535 | \& |
1884 | \& |
1536 | \& struct ev_timer mytimer; |
1885 | \& ev_timer mytimer; |
1537 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1886 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1538 | \& ev_timer_again (&mytimer); /* start timer */ |
1887 | \& ev_timer_again (&mytimer); /* start timer */ |
1539 | \& ev_loop (loop, 0); |
1888 | \& ev_loop (loop, 0); |
1540 | \& |
1889 | \& |
1541 | \& // and in some piece of code that gets executed on any "activity": |
1890 | \& // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1546 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
1895 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
1547 | .IX Subsection "ev_periodic - to cron or not to cron?" |
1896 | .IX Subsection "ev_periodic - to cron or not to cron?" |
1548 | Periodic watchers are also timers of a kind, but they are very versatile |
1897 | Periodic watchers are also timers of a kind, but they are very versatile |
1549 | (and unfortunately a bit complex). |
1898 | (and unfortunately a bit complex). |
1550 | .PP |
1899 | .PP |
1551 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
1900 | Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or |
1552 | but on wall clock time (absolute time). You can tell a periodic watcher |
1901 | relative time, the physical time that passes) but on wall clock time |
1553 | to trigger after some specific point in time. For example, if you tell a |
1902 | (absolute time, the thing you can read on your calender or clock). The |
1554 | periodic watcher to trigger in 10 seconds (by specifying e.g. \f(CW\*(C`ev_now () |
1903 | difference is that wall clock time can run faster or slower than real |
1555 | + 10.\*(C'\fR, that is, an absolute time not a delay) and then reset your system |
1904 | time, and time jumps are not uncommon (e.g. when you adjust your |
1556 | clock to January of the previous year, then it will take more than year |
1905 | wrist-watch). |
1557 | to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would still trigger |
|
|
1558 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1559 | .PP |
1906 | .PP |
|
|
1907 | You can tell a periodic watcher to trigger after some specific point |
|
|
1908 | in time: for example, if you tell a periodic watcher to trigger \*(L"in 10 |
|
|
1909 | seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time |
|
|
1910 | not a delay) and then reset your system clock to January of the previous |
|
|
1911 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1912 | \&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting |
|
|
1913 | it, as it uses a relative timeout). |
|
|
1914 | .PP |
1560 | \&\f(CW\*(C`ev_periodic\*(C'\fRs can also be used to implement vastly more complex timers, |
1915 | \&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex |
1561 | such as triggering an event on each \*(L"midnight, local time\*(R", or other |
1916 | timers, such as triggering an event on each \*(L"midnight, local time\*(R", or |
1562 | complicated rules. |
1917 | other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as |
|
|
1918 | those cannot react to time jumps. |
1563 | .PP |
1919 | .PP |
1564 | As with timers, the callback is guaranteed to be invoked only when the |
1920 | As with timers, the callback is guaranteed to be invoked only when the |
1565 | time (\f(CW\*(C`at\*(C'\fR) has passed, but if multiple periodic timers become ready |
1921 | point in time where it is supposed to trigger has passed. If multiple |
1566 | during the same loop iteration, then order of execution is undefined. |
1922 | timers become ready during the same loop iteration then the ones with |
|
|
1923 | earlier time-out values are invoked before ones with later time-out values |
|
|
1924 | (but this is no longer true when a callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively). |
1567 | .PP |
1925 | .PP |
1568 | \fIWatcher-Specific Functions and Data Members\fR |
1926 | \fIWatcher-Specific Functions and Data Members\fR |
1569 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1927 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1570 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
1928 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1571 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
1929 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1572 | .PD 0 |
1930 | .PD 0 |
1573 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
1931 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1574 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
1932 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1575 | .PD |
1933 | .PD |
1576 | Lots of arguments, lets sort it out... There are basically three modes of |
1934 | Lots of arguments, let's sort it out... There are basically three modes of |
1577 | operation, and we will explain them from simplest to most complex: |
1935 | operation, and we will explain them from simplest to most complex: |
1578 | .RS 4 |
1936 | .RS 4 |
1579 | .IP "\(bu" 4 |
1937 | .IP "\(bu" 4 |
1580 | absolute timer (at = time, interval = reschedule_cb = 0) |
1938 | absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1581 | .Sp |
1939 | .Sp |
1582 | In this configuration the watcher triggers an event after the wall clock |
1940 | In this configuration the watcher triggers an event after the wall clock |
1583 | time \f(CW\*(C`at\*(C'\fR has passed. It will not repeat and will not adjust when a time |
1941 | time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a |
1584 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1942 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1585 | only run when the system clock reaches or surpasses this time. |
1943 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1944 | this point in time. |
1586 | .IP "\(bu" 4 |
1945 | .IP "\(bu" 4 |
1587 | repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1946 | repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1588 | .Sp |
1947 | .Sp |
1589 | In this mode the watcher will always be scheduled to time out at the next |
1948 | In this mode the watcher will always be scheduled to time out at the next |
1590 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) |
1949 | \&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be |
1591 | and then repeat, regardless of any time jumps. |
1950 | negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR |
|
|
1951 | argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods. |
1592 | .Sp |
1952 | .Sp |
1593 | This can be used to create timers that do not drift with respect to the |
1953 | This can be used to create timers that do not drift with respect to the |
1594 | system clock, for example, here is a \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
1954 | system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
1595 | hour, on the hour: |
1955 | hour, on the hour (with respect to \s-1UTC\s0): |
1596 | .Sp |
1956 | .Sp |
1597 | .Vb 1 |
1957 | .Vb 1 |
1598 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
1958 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
1599 | .Ve |
1959 | .Ve |
1600 | .Sp |
1960 | .Sp |
… | |
… | |
1603 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1963 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1604 | by 3600. |
1964 | by 3600. |
1605 | .Sp |
1965 | .Sp |
1606 | Another way to think about it (for the mathematically inclined) is that |
1966 | Another way to think about it (for the mathematically inclined) is that |
1607 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1967 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1608 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
1968 | time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps. |
1609 | .Sp |
1969 | .Sp |
1610 | For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near |
1970 | For numerical stability it is preferable that the \f(CW\*(C`offset\*(C'\fR value is near |
1611 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
1971 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
1612 | this value, and in fact is often specified as zero. |
1972 | this value, and in fact is often specified as zero. |
1613 | .Sp |
1973 | .Sp |
1614 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
1974 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
1615 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
1975 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
1616 | will of course deteriorate. Libev itself tries to be exact to be about one |
1976 | will of course deteriorate. Libev itself tries to be exact to be about one |
1617 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
1977 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
1618 | .IP "\(bu" 4 |
1978 | .IP "\(bu" 4 |
1619 | manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1979 | manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1620 | .Sp |
1980 | .Sp |
1621 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
1981 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being |
1622 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1982 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1623 | reschedule callback will be called with the watcher as first, and the |
1983 | reschedule callback will be called with the watcher as first, and the |
1624 | current time as second argument. |
1984 | current time as second argument. |
1625 | .Sp |
1985 | .Sp |
1626 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
1986 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever, |
1627 | ever, or make \s-1ANY\s0 event loop modifications whatsoever\fR. |
1987 | or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly |
|
|
1988 | allowed by documentation here\fR. |
1628 | .Sp |
1989 | .Sp |
1629 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
1990 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
1630 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
1991 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
1631 | only event loop modification you are allowed to do). |
1992 | only event loop modification you are allowed to do). |
1632 | .Sp |
1993 | .Sp |
1633 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic |
1994 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic |
1634 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
1995 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
1635 | .Sp |
1996 | .Sp |
1636 | .Vb 4 |
1997 | .Vb 5 |
|
|
1998 | \& static ev_tstamp |
1637 | \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1999 | \& my_rescheduler (ev_periodic *w, ev_tstamp now) |
1638 | \& { |
2000 | \& { |
1639 | \& return now + 60.; |
2001 | \& return now + 60.; |
1640 | \& } |
2002 | \& } |
1641 | .Ve |
2003 | .Ve |
1642 | .Sp |
2004 | .Sp |
… | |
… | |
1662 | when you changed some parameters or the reschedule callback would return |
2024 | when you changed some parameters or the reschedule callback would return |
1663 | a different time than the last time it was called (e.g. in a crond like |
2025 | a different time than the last time it was called (e.g. in a crond like |
1664 | program when the crontabs have changed). |
2026 | program when the crontabs have changed). |
1665 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
2027 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
1666 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
2028 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
1667 | When active, returns the absolute time that the watcher is supposed to |
2029 | When active, returns the absolute time that the watcher is supposed |
1668 | trigger next. |
2030 | to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to |
|
|
2031 | \&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual |
|
|
2032 | rescheduling modes. |
1669 | .IP "ev_tstamp offset [read\-write]" 4 |
2033 | .IP "ev_tstamp offset [read\-write]" 4 |
1670 | .IX Item "ev_tstamp offset [read-write]" |
2034 | .IX Item "ev_tstamp offset [read-write]" |
1671 | When repeating, this contains the offset value, otherwise this is the |
2035 | When repeating, this contains the offset value, otherwise this is the |
1672 | absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). |
2036 | absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR, |
|
|
2037 | although libev might modify this value for better numerical stability). |
1673 | .Sp |
2038 | .Sp |
1674 | Can be modified any time, but changes only take effect when the periodic |
2039 | Can be modified any time, but changes only take effect when the periodic |
1675 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2040 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1676 | .IP "ev_tstamp interval [read\-write]" 4 |
2041 | .IP "ev_tstamp interval [read\-write]" 4 |
1677 | .IX Item "ev_tstamp interval [read-write]" |
2042 | .IX Item "ev_tstamp interval [read-write]" |
1678 | The current interval value. Can be modified any time, but changes only |
2043 | The current interval value. Can be modified any time, but changes only |
1679 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
2044 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
1680 | called. |
2045 | called. |
1681 | .IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
2046 | .IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
1682 | .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" |
2047 | .IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]" |
1683 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
2048 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
1684 | switched off. Can be changed any time, but changes only take effect when |
2049 | switched off. Can be changed any time, but changes only take effect when |
1685 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2050 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1686 | .PP |
2051 | .PP |
1687 | \fIExamples\fR |
2052 | \fIExamples\fR |
… | |
… | |
1691 | system time is divisible by 3600. The callback invocation times have |
2056 | system time is divisible by 3600. The callback invocation times have |
1692 | potentially a lot of jitter, but good long-term stability. |
2057 | potentially a lot of jitter, but good long-term stability. |
1693 | .PP |
2058 | .PP |
1694 | .Vb 5 |
2059 | .Vb 5 |
1695 | \& static void |
2060 | \& static void |
1696 | \& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2061 | \& clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1697 | \& { |
2062 | \& { |
1698 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2063 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1699 | \& } |
2064 | \& } |
1700 | \& |
2065 | \& |
1701 | \& struct ev_periodic hourly_tick; |
2066 | \& ev_periodic hourly_tick; |
1702 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2067 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1703 | \& ev_periodic_start (loop, &hourly_tick); |
2068 | \& ev_periodic_start (loop, &hourly_tick); |
1704 | .Ve |
2069 | .Ve |
1705 | .PP |
2070 | .PP |
1706 | Example: The same as above, but use a reschedule callback to do it: |
2071 | Example: The same as above, but use a reschedule callback to do it: |
1707 | .PP |
2072 | .PP |
1708 | .Vb 1 |
2073 | .Vb 1 |
1709 | \& #include <math.h> |
2074 | \& #include <math.h> |
1710 | \& |
2075 | \& |
1711 | \& static ev_tstamp |
2076 | \& static ev_tstamp |
1712 | \& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2077 | \& my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1713 | \& { |
2078 | \& { |
1714 | \& return now + (3600. \- fmod (now, 3600.)); |
2079 | \& return now + (3600. \- fmod (now, 3600.)); |
1715 | \& } |
2080 | \& } |
1716 | \& |
2081 | \& |
1717 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2082 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1718 | .Ve |
2083 | .Ve |
1719 | .PP |
2084 | .PP |
1720 | Example: Call a callback every hour, starting now: |
2085 | Example: Call a callback every hour, starting now: |
1721 | .PP |
2086 | .PP |
1722 | .Vb 4 |
2087 | .Vb 4 |
1723 | \& struct ev_periodic hourly_tick; |
2088 | \& ev_periodic hourly_tick; |
1724 | \& ev_periodic_init (&hourly_tick, clock_cb, |
2089 | \& ev_periodic_init (&hourly_tick, clock_cb, |
1725 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
2090 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
1726 | \& ev_periodic_start (loop, &hourly_tick); |
2091 | \& ev_periodic_start (loop, &hourly_tick); |
1727 | .Ve |
2092 | .Ve |
1728 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
2093 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
… | |
… | |
1765 | The signal the watcher watches out for. |
2130 | The signal the watcher watches out for. |
1766 | .PP |
2131 | .PP |
1767 | \fIExamples\fR |
2132 | \fIExamples\fR |
1768 | .IX Subsection "Examples" |
2133 | .IX Subsection "Examples" |
1769 | .PP |
2134 | .PP |
1770 | Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. |
2135 | Example: Try to exit cleanly on \s-1SIGINT\s0. |
1771 | .PP |
2136 | .PP |
1772 | .Vb 5 |
2137 | .Vb 5 |
1773 | \& static void |
2138 | \& static void |
1774 | \& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2139 | \& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1775 | \& { |
2140 | \& { |
1776 | \& ev_unloop (loop, EVUNLOOP_ALL); |
2141 | \& ev_unloop (loop, EVUNLOOP_ALL); |
1777 | \& } |
2142 | \& } |
1778 | \& |
2143 | \& |
1779 | \& struct ev_signal signal_watcher; |
2144 | \& ev_signal signal_watcher; |
1780 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2145 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1781 | \& ev_signal_start (loop, &sigint_cb); |
2146 | \& ev_signal_start (loop, &signal_watcher); |
1782 | .Ve |
2147 | .Ve |
1783 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
2148 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
1784 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
2149 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
1785 | .IX Subsection "ev_child - watch out for process status changes" |
2150 | .IX Subsection "ev_child - watch out for process status changes" |
1786 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
2151 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
… | |
… | |
1859 | .PP |
2224 | .PP |
1860 | .Vb 1 |
2225 | .Vb 1 |
1861 | \& ev_child cw; |
2226 | \& ev_child cw; |
1862 | \& |
2227 | \& |
1863 | \& static void |
2228 | \& static void |
1864 | \& child_cb (EV_P_ struct ev_child *w, int revents) |
2229 | \& child_cb (EV_P_ ev_child *w, int revents) |
1865 | \& { |
2230 | \& { |
1866 | \& ev_child_stop (EV_A_ w); |
2231 | \& ev_child_stop (EV_A_ w); |
1867 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
2232 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
1868 | \& } |
2233 | \& } |
1869 | \& |
2234 | \& |
… | |
… | |
1884 | .Ve |
2249 | .Ve |
1885 | .ie n .Sh """ev_stat"" \- did the file attributes just change?" |
2250 | .ie n .Sh """ev_stat"" \- did the file attributes just change?" |
1886 | .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
2251 | .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
1887 | .IX Subsection "ev_stat - did the file attributes just change?" |
2252 | .IX Subsection "ev_stat - did the file attributes just change?" |
1888 | This watches a file system path for attribute changes. That is, it calls |
2253 | This watches a file system path for attribute changes. That is, it calls |
1889 | \&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed |
2254 | \&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed) |
1890 | compared to the last time, invoking the callback if it did. |
2255 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2256 | it did. |
1891 | .PP |
2257 | .PP |
1892 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
2258 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
1893 | not exist\*(R" is a status change like any other. The condition \*(L"path does |
2259 | not exist\*(R" is a status change like any other. The condition \*(L"path does not |
1894 | not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is |
2260 | exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the |
1895 | otherwise always forced to be at least one) and all the other fields of |
2261 | \&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at |
1896 | the stat buffer having unspecified contents. |
2262 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2263 | contents. |
1897 | .PP |
2264 | .PP |
1898 | The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is |
2265 | The path \fImust not\fR end in a slash or contain special components such as |
|
|
2266 | \&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and |
1899 | relative and your working directory changes, the behaviour is undefined. |
2267 | your working directory changes, then the behaviour is undefined. |
1900 | .PP |
2268 | .PP |
1901 | Since there is no standard kernel interface to do this, the portable |
2269 | Since there is no portable change notification interface available, the |
1902 | implementation simply calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if |
2270 | portable implementation simply calls \f(CWstat(2)\fR regularly on the path |
1903 | it changed somehow. You can specify a recommended polling interval for |
2271 | to see if it changed somehow. You can specify a recommended polling |
1904 | this case. If you specify a polling interval of \f(CW0\fR (highly recommended!) |
2272 | interval for this case. If you specify a polling interval of \f(CW0\fR (highly |
1905 | then a \fIsuitable, unspecified default\fR value will be used (which |
2273 | recommended!) then a \fIsuitable, unspecified default\fR value will be used |
1906 | you can expect to be around five seconds, although this might change |
2274 | (which you can expect to be around five seconds, although this might |
1907 | dynamically). Libev will also impose a minimum interval which is currently |
2275 | change dynamically). Libev will also impose a minimum interval which is |
1908 | around \f(CW0.1\fR, but thats usually overkill. |
2276 | currently around \f(CW0.1\fR, but that's usually overkill. |
1909 | .PP |
2277 | .PP |
1910 | This watcher type is not meant for massive numbers of stat watchers, |
2278 | This watcher type is not meant for massive numbers of stat watchers, |
1911 | as even with OS-supported change notifications, this can be |
2279 | as even with OS-supported change notifications, this can be |
1912 | resource-intensive. |
2280 | resource-intensive. |
1913 | .PP |
2281 | .PP |
1914 | At the time of this writing, the only OS-specific interface implemented |
2282 | At the time of this writing, the only OS-specific interface implemented |
1915 | is the Linux inotify interface (implementing kqueue support is left as |
2283 | is the Linux inotify interface (implementing kqueue support is left as an |
1916 | an exercise for the reader. Note, however, that the author sees no way |
2284 | exercise for the reader. Note, however, that the author sees no way of |
1917 | of implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue). |
2285 | implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint). |
1918 | .PP |
2286 | .PP |
1919 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
2287 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
1920 | .IX Subsection "ABI Issues (Largefile Support)" |
2288 | .IX Subsection "ABI Issues (Largefile Support)" |
1921 | .PP |
2289 | .PP |
1922 | Libev by default (unless the user overrides this) uses the default |
2290 | Libev by default (unless the user overrides this) uses the default |
… | |
… | |
1924 | support disabled by default, you get the 32 bit version of the stat |
2292 | support disabled by default, you get the 32 bit version of the stat |
1925 | structure. When using the library from programs that change the \s-1ABI\s0 to |
2293 | structure. When using the library from programs that change the \s-1ABI\s0 to |
1926 | use 64 bit file offsets the programs will fail. In that case you have to |
2294 | use 64 bit file offsets the programs will fail. In that case you have to |
1927 | compile libev with the same flags to get binary compatibility. This is |
2295 | compile libev with the same flags to get binary compatibility. This is |
1928 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
2296 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
1929 | most noticeably disabled with ev_stat and large file support. |
2297 | most noticeably displayed with ev_stat and large file support. |
1930 | .PP |
2298 | .PP |
1931 | The solution for this is to lobby your distribution maker to make large |
2299 | The solution for this is to lobby your distribution maker to make large |
1932 | file interfaces available by default (as e.g. FreeBSD does) and not |
2300 | file interfaces available by default (as e.g. FreeBSD does) and not |
1933 | optional. Libev cannot simply switch on large file support because it has |
2301 | optional. Libev cannot simply switch on large file support because it has |
1934 | to exchange stat structures with application programs compiled using the |
2302 | to exchange stat structures with application programs compiled using the |
1935 | default compilation environment. |
2303 | default compilation environment. |
1936 | .PP |
2304 | .PP |
1937 | \fIInotify and Kqueue\fR |
2305 | \fIInotify and Kqueue\fR |
1938 | .IX Subsection "Inotify and Kqueue" |
2306 | .IX Subsection "Inotify and Kqueue" |
1939 | .PP |
2307 | .PP |
1940 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only |
2308 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at |
1941 | available with Linux) and present at runtime, it will be used to speed up |
2309 | runtime, it will be used to speed up change detection where possible. The |
1942 | change detection where possible. The inotify descriptor will be created lazily |
2310 | inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR |
1943 | when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started. |
2311 | watcher is being started. |
1944 | .PP |
2312 | .PP |
1945 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
2313 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
1946 | except that changes might be detected earlier, and in some cases, to avoid |
2314 | except that changes might be detected earlier, and in some cases, to avoid |
1947 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
2315 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
1948 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
2316 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
1949 | but as long as the path exists, libev usually gets away without polling. |
2317 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2318 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2319 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2320 | xfs are fully working) libev usually gets away without polling. |
1950 | .PP |
2321 | .PP |
1951 | There is no support for kqueue, as apparently it cannot be used to |
2322 | There is no support for kqueue, as apparently it cannot be used to |
1952 | implement this functionality, due to the requirement of having a file |
2323 | implement this functionality, due to the requirement of having a file |
1953 | descriptor open on the object at all times, and detecting renames, unlinks |
2324 | descriptor open on the object at all times, and detecting renames, unlinks |
1954 | etc. is difficult. |
2325 | etc. is difficult. |
1955 | .PP |
2326 | .PP |
|
|
2327 | \fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR |
|
|
2328 | .IX Subsection "stat () is a synchronous operation" |
|
|
2329 | .PP |
|
|
2330 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2331 | the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat |
|
|
2332 | ()\*(C'\fR, which is a synchronous operation. |
|
|
2333 | .PP |
|
|
2334 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2335 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2336 | as the path data is usually in memory already (except when starting the |
|
|
2337 | watcher). |
|
|
2338 | .PP |
|
|
2339 | For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite |
|
|
2340 | time due to network issues, and even under good conditions, a stat call |
|
|
2341 | often takes multiple milliseconds. |
|
|
2342 | .PP |
|
|
2343 | Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked |
|
|
2344 | paths, although this is fully supported by libev. |
|
|
2345 | .PP |
1956 | \fIThe special problem of stat time resolution\fR |
2346 | \fIThe special problem of stat time resolution\fR |
1957 | .IX Subsection "The special problem of stat time resolution" |
2347 | .IX Subsection "The special problem of stat time resolution" |
1958 | .PP |
2348 | .PP |
1959 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, and |
2349 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, |
1960 | even on systems where the resolution is higher, most file systems still |
2350 | and even on systems where the resolution is higher, most file systems |
1961 | only support whole seconds. |
2351 | still only support whole seconds. |
1962 | .PP |
2352 | .PP |
1963 | That means that, if the time is the only thing that changes, you can |
2353 | That means that, if the time is the only thing that changes, you can |
1964 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
2354 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
1965 | calls your callback, which does something. When there is another update |
2355 | calls your callback, which does something. When there is another update |
1966 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
2356 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
… | |
… | |
2104 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
2494 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
2105 | event loop has handled all outstanding events. |
2495 | event loop has handled all outstanding events. |
2106 | .PP |
2496 | .PP |
2107 | \fIWatcher-Specific Functions and Data Members\fR |
2497 | \fIWatcher-Specific Functions and Data Members\fR |
2108 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2498 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2109 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
2499 | .IP "ev_idle_init (ev_idle *, callback)" 4 |
2110 | .IX Item "ev_idle_init (ev_signal *, callback)" |
2500 | .IX Item "ev_idle_init (ev_idle *, callback)" |
2111 | Initialises and configures the idle watcher \- it has no parameters of any |
2501 | Initialises and configures the idle watcher \- it has no parameters of any |
2112 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
2502 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
2113 | believe me. |
2503 | believe me. |
2114 | .PP |
2504 | .PP |
2115 | \fIExamples\fR |
2505 | \fIExamples\fR |
… | |
… | |
2118 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
2508 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
2119 | callback, free it. Also, use no error checking, as usual. |
2509 | callback, free it. Also, use no error checking, as usual. |
2120 | .PP |
2510 | .PP |
2121 | .Vb 7 |
2511 | .Vb 7 |
2122 | \& static void |
2512 | \& static void |
2123 | \& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2513 | \& idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2124 | \& { |
2514 | \& { |
2125 | \& free (w); |
2515 | \& free (w); |
2126 | \& // now do something you wanted to do when the program has |
2516 | \& // now do something you wanted to do when the program has |
2127 | \& // no longer anything immediate to do. |
2517 | \& // no longer anything immediate to do. |
2128 | \& } |
2518 | \& } |
2129 | \& |
2519 | \& |
2130 | \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2520 | \& ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2131 | \& ev_idle_init (idle_watcher, idle_cb); |
2521 | \& ev_idle_init (idle_watcher, idle_cb); |
2132 | \& ev_idle_start (loop, idle_cb); |
2522 | \& ev_idle_start (loop, idle_cb); |
2133 | .Ve |
2523 | .Ve |
2134 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
2524 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
2135 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
2525 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
… | |
… | |
2216 | .Vb 2 |
2606 | .Vb 2 |
2217 | \& static ev_io iow [nfd]; |
2607 | \& static ev_io iow [nfd]; |
2218 | \& static ev_timer tw; |
2608 | \& static ev_timer tw; |
2219 | \& |
2609 | \& |
2220 | \& static void |
2610 | \& static void |
2221 | \& io_cb (ev_loop *loop, ev_io *w, int revents) |
2611 | \& io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2222 | \& { |
2612 | \& { |
2223 | \& } |
2613 | \& } |
2224 | \& |
2614 | \& |
2225 | \& // create io watchers for each fd and a timer before blocking |
2615 | \& // create io watchers for each fd and a timer before blocking |
2226 | \& static void |
2616 | \& static void |
2227 | \& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2617 | \& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2228 | \& { |
2618 | \& { |
2229 | \& int timeout = 3600000; |
2619 | \& int timeout = 3600000; |
2230 | \& struct pollfd fds [nfd]; |
2620 | \& struct pollfd fds [nfd]; |
2231 | \& // actual code will need to loop here and realloc etc. |
2621 | \& // actual code will need to loop here and realloc etc. |
2232 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2622 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
2247 | \& } |
2637 | \& } |
2248 | \& } |
2638 | \& } |
2249 | \& |
2639 | \& |
2250 | \& // stop all watchers after blocking |
2640 | \& // stop all watchers after blocking |
2251 | \& static void |
2641 | \& static void |
2252 | \& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2642 | \& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2253 | \& { |
2643 | \& { |
2254 | \& ev_timer_stop (loop, &tw); |
2644 | \& ev_timer_stop (loop, &tw); |
2255 | \& |
2645 | \& |
2256 | \& for (int i = 0; i < nfd; ++i) |
2646 | \& for (int i = 0; i < nfd; ++i) |
2257 | \& { |
2647 | \& { |
… | |
… | |
2357 | some fds have to be watched and handled very quickly (with low latency), |
2747 | some fds have to be watched and handled very quickly (with low latency), |
2358 | and even priorities and idle watchers might have too much overhead. In |
2748 | and even priorities and idle watchers might have too much overhead. In |
2359 | this case you would put all the high priority stuff in one loop and all |
2749 | this case you would put all the high priority stuff in one loop and all |
2360 | the rest in a second one, and embed the second one in the first. |
2750 | the rest in a second one, and embed the second one in the first. |
2361 | .PP |
2751 | .PP |
2362 | As long as the watcher is active, the callback will be invoked every time |
2752 | As long as the watcher is active, the callback will be invoked every |
2363 | there might be events pending in the embedded loop. The callback must then |
2753 | time there might be events pending in the embedded loop. The callback |
2364 | call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke |
2754 | must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single |
2365 | their callbacks (you could also start an idle watcher to give the embedded |
2755 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2366 | loop strictly lower priority for example). You can also set the callback |
2756 | \&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher |
2367 | to \f(CW0\fR, in which case the embed watcher will automatically execute the |
2757 | to give the embedded loop strictly lower priority for example). |
2368 | embedded loop sweep. |
|
|
2369 | .PP |
2758 | .PP |
2370 | As long as the watcher is started it will automatically handle events. The |
2759 | You can also set the callback to \f(CW0\fR, in which case the embed watcher |
2371 | callback will be invoked whenever some events have been handled. You can |
2760 | will automatically execute the embedded loop sweep whenever necessary. |
2372 | set the callback to \f(CW0\fR to avoid having to specify one if you are not |
|
|
2373 | interested in that. |
|
|
2374 | .PP |
2761 | .PP |
2375 | Also, there have not currently been made special provisions for forking: |
2762 | Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher |
2376 | when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, |
2763 | is active, i.e., the embedded loop will automatically be forked when the |
2377 | but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers |
2764 | embedding loop forks. In other cases, the user is responsible for calling |
2378 | yourself \- but you can use a fork watcher to handle this automatically, |
2765 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop. |
2379 | and future versions of libev might do just that. |
|
|
2380 | .PP |
2766 | .PP |
2381 | Unfortunately, not all backends are embeddable: only the ones returned by |
2767 | Unfortunately, not all backends are embeddable: only the ones returned by |
2382 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
2768 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
2383 | portable one. |
2769 | portable one. |
2384 | .PP |
2770 | .PP |
… | |
… | |
2428 | used). |
2814 | used). |
2429 | .PP |
2815 | .PP |
2430 | .Vb 3 |
2816 | .Vb 3 |
2431 | \& struct ev_loop *loop_hi = ev_default_init (0); |
2817 | \& struct ev_loop *loop_hi = ev_default_init (0); |
2432 | \& struct ev_loop *loop_lo = 0; |
2818 | \& struct ev_loop *loop_lo = 0; |
2433 | \& struct ev_embed embed; |
2819 | \& ev_embed embed; |
2434 | \& |
2820 | \& |
2435 | \& // see if there is a chance of getting one that works |
2821 | \& // see if there is a chance of getting one that works |
2436 | \& // (remember that a flags value of 0 means autodetection) |
2822 | \& // (remember that a flags value of 0 means autodetection) |
2437 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2823 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2438 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2824 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2454 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
2840 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
2455 | .PP |
2841 | .PP |
2456 | .Vb 3 |
2842 | .Vb 3 |
2457 | \& struct ev_loop *loop = ev_default_init (0); |
2843 | \& struct ev_loop *loop = ev_default_init (0); |
2458 | \& struct ev_loop *loop_socket = 0; |
2844 | \& struct ev_loop *loop_socket = 0; |
2459 | \& struct ev_embed embed; |
2845 | \& ev_embed embed; |
2460 | \& |
2846 | \& |
2461 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2847 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2462 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2848 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2463 | \& { |
2849 | \& { |
2464 | \& ev_embed_init (&embed, 0, loop_socket); |
2850 | \& ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2478 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
2864 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
2479 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
2865 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
2480 | and only in the child after the fork. If whoever good citizen calling |
2866 | and only in the child after the fork. If whoever good citizen calling |
2481 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
2867 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
2482 | handlers will be invoked, too, of course. |
2868 | handlers will be invoked, too, of course. |
|
|
2869 | .PP |
|
|
2870 | \fIThe special problem of life after fork \- how is it possible?\fR |
|
|
2871 | .IX Subsection "The special problem of life after fork - how is it possible?" |
|
|
2872 | .PP |
|
|
2873 | Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to ste |
|
|
2874 | up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This |
|
|
2875 | sequence should be handled by libev without any problems. |
|
|
2876 | .PP |
|
|
2877 | This changes when the application actually wants to do event handling |
|
|
2878 | in the child, or both parent in child, in effect \*(L"continuing\*(R" after the |
|
|
2879 | fork. |
|
|
2880 | .PP |
|
|
2881 | The default mode of operation (for libev, with application help to detect |
|
|
2882 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2883 | when \fIeither\fR the parent \fIor\fR the child process continues. |
|
|
2884 | .PP |
|
|
2885 | When both processes want to continue using libev, then this is usually the |
|
|
2886 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2887 | supposed to continue with all watchers in place as before, while the other |
|
|
2888 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2889 | .PP |
|
|
2890 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2891 | simply create a new event loop, which of course will be \*(L"empty\*(R", and |
|
|
2892 | use that for new watchers. This has the advantage of not touching more |
|
|
2893 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2894 | disadvantage of having to use multiple event loops (which do not support |
|
|
2895 | signal watchers). |
|
|
2896 | .PP |
|
|
2897 | When this is not possible, or you want to use the default loop for |
|
|
2898 | other reasons, then in the process that wants to start \*(L"fresh\*(R", call |
|
|
2899 | \&\f(CW\*(C`ev_default_destroy ()\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR. Destroying |
|
|
2900 | the default loop will \*(L"orphan\*(R" (not stop) all registered watchers, so you |
|
|
2901 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2902 | also that in that case, you have to re-register any signal watchers. |
2483 | .PP |
2903 | .PP |
2484 | \fIWatcher-Specific Functions and Data Members\fR |
2904 | \fIWatcher-Specific Functions and Data Members\fR |
2485 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2905 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2486 | .IP "ev_fork_init (ev_signal *, callback)" 4 |
2906 | .IP "ev_fork_init (ev_signal *, callback)" 4 |
2487 | .IX Item "ev_fork_init (ev_signal *, callback)" |
2907 | .IX Item "ev_fork_init (ev_signal *, callback)" |
… | |
… | |
2521 | queue. But at least I can tell you how to implement locking around your |
2941 | queue. But at least I can tell you how to implement locking around your |
2522 | queue: |
2942 | queue: |
2523 | .IP "queueing from a signal handler context" 4 |
2943 | .IP "queueing from a signal handler context" 4 |
2524 | .IX Item "queueing from a signal handler context" |
2944 | .IX Item "queueing from a signal handler context" |
2525 | To implement race-free queueing, you simply add to the queue in the signal |
2945 | To implement race-free queueing, you simply add to the queue in the signal |
2526 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2946 | handler but you block the signal handler in the watcher callback. Here is |
2527 | some fictitious \s-1SIGUSR1\s0 handler: |
2947 | an example that does that for some fictitious \s-1SIGUSR1\s0 handler: |
2528 | .Sp |
2948 | .Sp |
2529 | .Vb 1 |
2949 | .Vb 1 |
2530 | \& static ev_async mysig; |
2950 | \& static ev_async mysig; |
2531 | \& |
2951 | \& |
2532 | \& static void |
2952 | \& static void |
… | |
… | |
2596 | \fIWatcher-Specific Functions and Data Members\fR |
3016 | \fIWatcher-Specific Functions and Data Members\fR |
2597 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3017 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2598 | .IP "ev_async_init (ev_async *, callback)" 4 |
3018 | .IP "ev_async_init (ev_async *, callback)" 4 |
2599 | .IX Item "ev_async_init (ev_async *, callback)" |
3019 | .IX Item "ev_async_init (ev_async *, callback)" |
2600 | Initialises and configures the async watcher \- it has no parameters of any |
3020 | Initialises and configures the async watcher \- it has no parameters of any |
2601 | kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless, |
3021 | kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
2602 | trust me. |
3022 | trust me. |
2603 | .IP "ev_async_send (loop, ev_async *)" 4 |
3023 | .IP "ev_async_send (loop, ev_async *)" 4 |
2604 | .IX Item "ev_async_send (loop, ev_async *)" |
3024 | .IX Item "ev_async_send (loop, ev_async *)" |
2605 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
3025 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
2606 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
3026 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
2607 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or |
3027 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or |
2608 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
3028 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
2609 | section below on what exactly this means). |
3029 | section below on what exactly this means). |
2610 | .Sp |
3030 | .Sp |
|
|
3031 | Note that, as with other watchers in libev, multiple events might get |
|
|
3032 | compressed into a single callback invocation (another way to look at this |
|
|
3033 | is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered, set on \f(CW\*(C`ev_async_send\*(C'\fR, |
|
|
3034 | reset when the event loop detects that). |
|
|
3035 | .Sp |
2611 | This call incurs the overhead of a system call only once per loop iteration, |
3036 | This call incurs the overhead of a system call only once per event loop |
2612 | so while the overhead might be noticeable, it doesn't apply to repeated |
3037 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2613 | calls to \f(CW\*(C`ev_async_send\*(C'\fR. |
3038 | repeated calls to \f(CW\*(C`ev_async_send\*(C'\fR for the same event loop. |
2614 | .IP "bool = ev_async_pending (ev_async *)" 4 |
3039 | .IP "bool = ev_async_pending (ev_async *)" 4 |
2615 | .IX Item "bool = ev_async_pending (ev_async *)" |
3040 | .IX Item "bool = ev_async_pending (ev_async *)" |
2616 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
3041 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
2617 | watcher but the event has not yet been processed (or even noted) by the |
3042 | watcher but the event has not yet been processed (or even noted) by the |
2618 | event loop. |
3043 | event loop. |
… | |
… | |
2620 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
3045 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
2621 | the loop iterates next and checks for the watcher to have become active, |
3046 | the loop iterates next and checks for the watcher to have become active, |
2622 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
3047 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
2623 | quickly check whether invoking the loop might be a good idea. |
3048 | quickly check whether invoking the loop might be a good idea. |
2624 | .Sp |
3049 | .Sp |
2625 | Not that this does \fInot\fR check whether the watcher itself is pending, only |
3050 | Not that this does \fInot\fR check whether the watcher itself is pending, |
2626 | whether it has been requested to make this watcher pending. |
3051 | only whether it has been requested to make this watcher pending: there |
|
|
3052 | is a time window between the event loop checking and resetting the async |
|
|
3053 | notification, and the callback being invoked. |
2627 | .SH "OTHER FUNCTIONS" |
3054 | .SH "OTHER FUNCTIONS" |
2628 | .IX Header "OTHER FUNCTIONS" |
3055 | .IX Header "OTHER FUNCTIONS" |
2629 | There are some other functions of possible interest. Described. Here. Now. |
3056 | There are some other functions of possible interest. Described. Here. Now. |
2630 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
3057 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
2631 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
3058 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
2632 | This function combines a simple timer and an I/O watcher, calls your |
3059 | This function combines a simple timer and an I/O watcher, calls your |
2633 | callback on whichever event happens first and automatically stop both |
3060 | callback on whichever event happens first and automatically stops both |
2634 | watchers. This is useful if you want to wait for a single event on an fd |
3061 | watchers. This is useful if you want to wait for a single event on an fd |
2635 | or timeout without having to allocate/configure/start/stop/free one or |
3062 | or timeout without having to allocate/configure/start/stop/free one or |
2636 | more watchers yourself. |
3063 | more watchers yourself. |
2637 | .Sp |
3064 | .Sp |
2638 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
3065 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the |
2639 | is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
3066 | \&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for |
2640 | \&\f(CW\*(C`events\*(C'\fR set will be created and started. |
3067 | the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started. |
2641 | .Sp |
3068 | .Sp |
2642 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
3069 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
2643 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
3070 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
2644 | repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
3071 | repeat = 0) will be started. \f(CW0\fR is a valid timeout. |
2645 | dubious value. |
|
|
2646 | .Sp |
3072 | .Sp |
2647 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
3073 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
2648 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
3074 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
2649 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
3075 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
2650 | value passed to \f(CW\*(C`ev_once\*(C'\fR: |
3076 | value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR |
|
|
3077 | a timeout and an io event at the same time \- you probably should give io |
|
|
3078 | events precedence. |
|
|
3079 | .Sp |
|
|
3080 | Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0. |
2651 | .Sp |
3081 | .Sp |
2652 | .Vb 7 |
3082 | .Vb 7 |
2653 | \& static void stdin_ready (int revents, void *arg) |
3083 | \& static void stdin_ready (int revents, void *arg) |
2654 | \& { |
3084 | \& { |
|
|
3085 | \& if (revents & EV_READ) |
|
|
3086 | \& /* stdin might have data for us, joy! */; |
2655 | \& if (revents & EV_TIMEOUT) |
3087 | \& else if (revents & EV_TIMEOUT) |
2656 | \& /* doh, nothing entered */; |
3088 | \& /* doh, nothing entered */; |
2657 | \& else if (revents & EV_READ) |
|
|
2658 | \& /* stdin might have data for us, joy! */; |
|
|
2659 | \& } |
3089 | \& } |
2660 | \& |
3090 | \& |
2661 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3091 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2662 | .Ve |
3092 | .Ve |
2663 | .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 |
3093 | .IP "ev_feed_event (struct ev_loop *, watcher *, int revents)" 4 |
2664 | .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" |
3094 | .IX Item "ev_feed_event (struct ev_loop *, watcher *, int revents)" |
2665 | Feeds the given event set into the event loop, as if the specified event |
3095 | Feeds the given event set into the event loop, as if the specified event |
2666 | had happened for the specified watcher (which must be a pointer to an |
3096 | had happened for the specified watcher (which must be a pointer to an |
2667 | initialised but not necessarily started event watcher). |
3097 | initialised but not necessarily started event watcher). |
2668 | .IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 |
3098 | .IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4 |
2669 | .IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" |
3099 | .IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" |
2670 | Feed an event on the given fd, as if a file descriptor backend detected |
3100 | Feed an event on the given fd, as if a file descriptor backend detected |
2671 | the given events it. |
3101 | the given events it. |
2672 | .IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 |
3102 | .IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4 |
2673 | .IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" |
3103 | .IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)" |
2674 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
3104 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
2675 | loop!). |
3105 | loop!). |
2676 | .SH "LIBEVENT EMULATION" |
3106 | .SH "LIBEVENT EMULATION" |
2677 | .IX Header "LIBEVENT EMULATION" |
3107 | .IX Header "LIBEVENT EMULATION" |
2678 | Libev offers a compatibility emulation layer for libevent. It cannot |
3108 | Libev offers a compatibility emulation layer for libevent. It cannot |
… | |
… | |
2789 | \& } |
3219 | \& } |
2790 | \& |
3220 | \& |
2791 | \& myclass obj; |
3221 | \& myclass obj; |
2792 | \& ev::io iow; |
3222 | \& ev::io iow; |
2793 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
3223 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3224 | .Ve |
|
|
3225 | .IP "w\->set (object *)" 4 |
|
|
3226 | .IX Item "w->set (object *)" |
|
|
3227 | This is an \fBexperimental\fR feature that might go away in a future version. |
|
|
3228 | .Sp |
|
|
3229 | This is a variation of a method callback \- leaving out the method to call |
|
|
3230 | will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use |
|
|
3231 | functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all |
|
|
3232 | the time. Incidentally, you can then also leave out the template argument |
|
|
3233 | list. |
|
|
3234 | .Sp |
|
|
3235 | The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w, |
|
|
3236 | int revents)\*(C'\fR. |
|
|
3237 | .Sp |
|
|
3238 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
3239 | .Sp |
|
|
3240 | Example: use a functor object as callback. |
|
|
3241 | .Sp |
|
|
3242 | .Vb 7 |
|
|
3243 | \& struct myfunctor |
|
|
3244 | \& { |
|
|
3245 | \& void operator() (ev::io &w, int revents) |
|
|
3246 | \& { |
|
|
3247 | \& ... |
|
|
3248 | \& } |
|
|
3249 | \& } |
|
|
3250 | \& |
|
|
3251 | \& myfunctor f; |
|
|
3252 | \& |
|
|
3253 | \& ev::io w; |
|
|
3254 | \& w.set (&f); |
2794 | .Ve |
3255 | .Ve |
2795 | .IP "w\->set<function> (void *data = 0)" 4 |
3256 | .IP "w\->set<function> (void *data = 0)" 4 |
2796 | .IX Item "w->set<function> (void *data = 0)" |
3257 | .IX Item "w->set<function> (void *data = 0)" |
2797 | Also sets a callback, but uses a static method or plain function as |
3258 | Also sets a callback, but uses a static method or plain function as |
2798 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
3259 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
… | |
… | |
2878 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
3339 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
2879 | <http://software.schmorp.de/pkg/EV>. |
3340 | <http://software.schmorp.de/pkg/EV>. |
2880 | .IP "Python" 4 |
3341 | .IP "Python" 4 |
2881 | .IX Item "Python" |
3342 | .IX Item "Python" |
2882 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
3343 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
2883 | seems to be quite complete and well-documented. Note, however, that the |
3344 | seems to be quite complete and well-documented. |
2884 | patch they require for libev is outright dangerous as it breaks the \s-1ABI\s0 |
|
|
2885 | for everybody else, and therefore, should never be applied in an installed |
|
|
2886 | libev (if python requires an incompatible \s-1ABI\s0 then it needs to embed |
|
|
2887 | libev). |
|
|
2888 | .IP "Ruby" 4 |
3345 | .IP "Ruby" 4 |
2889 | .IX Item "Ruby" |
3346 | .IX Item "Ruby" |
2890 | Tony Arcieri has written a ruby extension that offers access to a subset |
3347 | Tony Arcieri has written a ruby extension that offers access to a subset |
2891 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
3348 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
2892 | more on top of it. It can be found via gem servers. Its homepage is at |
3349 | more on top of it. It can be found via gem servers. Its homepage is at |
2893 | <http://rev.rubyforge.org/>. |
3350 | <http://rev.rubyforge.org/>. |
|
|
3351 | .Sp |
|
|
3352 | Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
|
|
3353 | makes rev work even on mingw. |
|
|
3354 | .IP "Haskell" 4 |
|
|
3355 | .IX Item "Haskell" |
|
|
3356 | A haskell binding to libev is available at |
|
|
3357 | <http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>. |
2894 | .IP "D" 4 |
3358 | .IP "D" 4 |
2895 | .IX Item "D" |
3359 | .IX Item "D" |
2896 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
3360 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
2897 | be found at <http://proj.llucax.com.ar/wiki/evd>. |
3361 | be found at <http://proj.llucax.com.ar/wiki/evd>. |
|
|
3362 | .IP "Ocaml" 4 |
|
|
3363 | .IX Item "Ocaml" |
|
|
3364 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3365 | <http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>. |
2898 | .SH "MACRO MAGIC" |
3366 | .SH "MACRO MAGIC" |
2899 | .IX Header "MACRO MAGIC" |
3367 | .IX Header "MACRO MAGIC" |
2900 | Libev can be compiled with a variety of options, the most fundamental |
3368 | Libev can be compiled with a variety of options, the most fundamental |
2901 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
3369 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
2902 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
3370 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
… | |
… | |
3004 | \& #define EV_STANDALONE 1 |
3472 | \& #define EV_STANDALONE 1 |
3005 | \& #include "ev.h" |
3473 | \& #include "ev.h" |
3006 | .Ve |
3474 | .Ve |
3007 | .PP |
3475 | .PP |
3008 | Both header files and implementation files can be compiled with a \*(C+ |
3476 | Both header files and implementation files can be compiled with a \*(C+ |
3009 | compiler (at least, thats a stated goal, and breakage will be treated |
3477 | compiler (at least, that's a stated goal, and breakage will be treated |
3010 | as a bug). |
3478 | as a bug). |
3011 | .PP |
3479 | .PP |
3012 | You need the following files in your source tree, or in a directory |
3480 | You need the following files in your source tree, or in a directory |
3013 | in your include path (e.g. in libev/ when using \-Ilibev): |
3481 | in your include path (e.g. in libev/ when using \-Ilibev): |
3014 | .PP |
3482 | .PP |
… | |
… | |
3077 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
3545 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
3078 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
3546 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
3079 | implementations for some libevent functions (such as logging, which is not |
3547 | implementations for some libevent functions (such as logging, which is not |
3080 | supported). It will also not define any of the structs usually found in |
3548 | supported). It will also not define any of the structs usually found in |
3081 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
3549 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
|
|
3550 | .Sp |
|
|
3551 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3552 | configuration, but has to be more conservative. |
3082 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
3553 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
3083 | .IX Item "EV_USE_MONOTONIC" |
3554 | .IX Item "EV_USE_MONOTONIC" |
3084 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3555 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3085 | monotonic clock option at both compile time and runtime. Otherwise no use |
3556 | monotonic clock option at both compile time and runtime. Otherwise no |
3086 | of the monotonic clock option will be attempted. If you enable this, you |
3557 | use of the monotonic clock option will be attempted. If you enable this, |
3087 | usually have to link against librt or something similar. Enabling it when |
3558 | you usually have to link against librt or something similar. Enabling it |
3088 | the functionality isn't available is safe, though, although you have |
3559 | when the functionality isn't available is safe, though, although you have |
3089 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
3560 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
3090 | function is hiding in (often \fI\-lrt\fR). |
3561 | function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
3091 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
3562 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
3092 | .IX Item "EV_USE_REALTIME" |
3563 | .IX Item "EV_USE_REALTIME" |
3093 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3564 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3094 | real-time clock option at compile time (and assume its availability at |
3565 | real-time clock option at compile time (and assume its availability |
3095 | runtime if successful). Otherwise no use of the real-time clock option will |
3566 | at runtime if successful). Otherwise no use of the real-time clock |
3096 | be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
3567 | option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR |
3097 | (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the |
3568 | by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect |
3098 | note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
3569 | correctness. See the note about libraries in the description of |
|
|
3570 | \&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of |
|
|
3571 | \&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
|
|
3572 | .IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4 |
|
|
3573 | .IX Item "EV_USE_CLOCK_SYSCALL" |
|
|
3574 | If defined to be \f(CW1\fR, libev will try to use a direct syscall instead |
|
|
3575 | of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option |
|
|
3576 | exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR |
|
|
3577 | unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded |
|
|
3578 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3579 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3580 | the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or |
|
|
3581 | higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
3099 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
3582 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
3100 | .IX Item "EV_USE_NANOSLEEP" |
3583 | .IX Item "EV_USE_NANOSLEEP" |
3101 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
3584 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
3102 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
3585 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
3103 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
3586 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
… | |
… | |
3115 | will not be compiled in. |
3598 | will not be compiled in. |
3116 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
3599 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
3117 | .IX Item "EV_SELECT_USE_FD_SET" |
3600 | .IX Item "EV_SELECT_USE_FD_SET" |
3118 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
3601 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
3119 | structure. This is useful if libev doesn't compile due to a missing |
3602 | structure. This is useful if libev doesn't compile due to a missing |
3120 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout on |
3603 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout |
3121 | exotic systems. This usually limits the range of file descriptors to some |
3604 | on exotic systems. This usually limits the range of file descriptors to |
3122 | low limit such as 1024 or might have other limitations (winsocket only |
3605 | some low limit such as 1024 or might have other limitations (winsocket |
3123 | allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might |
3606 | only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, |
3124 | influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. |
3607 | configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR. |
3125 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
3608 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
3126 | .IX Item "EV_SELECT_IS_WINSOCKET" |
3609 | .IX Item "EV_SELECT_IS_WINSOCKET" |
3127 | When defined to \f(CW1\fR, the select backend will assume that |
3610 | When defined to \f(CW1\fR, the select backend will assume that |
3128 | select/socket/connect etc. don't understand file descriptors but |
3611 | select/socket/connect etc. don't understand file descriptors but |
3129 | wants osf handles on win32 (this is the case when the select to |
3612 | wants osf handles on win32 (this is the case when the select to |
… | |
… | |
3398 | .PP |
3881 | .PP |
3399 | .Vb 2 |
3882 | .Vb 2 |
3400 | \& #include "ev_cpp.h" |
3883 | \& #include "ev_cpp.h" |
3401 | \& #include "ev.c" |
3884 | \& #include "ev.c" |
3402 | .Ve |
3885 | .Ve |
3403 | .SH "THREADS AND COROUTINES" |
3886 | .SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
|
|
3887 | .IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
|
|
3888 | .Sh "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0" |
3404 | .IX Header "THREADS AND COROUTINES" |
3889 | .IX Subsection "THREADS AND COROUTINES" |
3405 | .Sh "\s-1THREADS\s0" |
3890 | \fI\s-1THREADS\s0\fR |
3406 | .IX Subsection "THREADS" |
3891 | .IX Subsection "THREADS" |
|
|
3892 | .PP |
3407 | All libev functions are reentrant and thread-safe unless explicitly |
3893 | All libev functions are reentrant and thread-safe unless explicitly |
3408 | documented otherwise, but it uses no locking itself. This means that you |
3894 | documented otherwise, but libev implements no locking itself. This means |
3409 | can use as many loops as you want in parallel, as long as there are no |
3895 | that you can use as many loops as you want in parallel, as long as there |
3410 | concurrent calls into any libev function with the same loop parameter |
3896 | are no concurrent calls into any libev function with the same loop |
3411 | (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, of |
3897 | parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, |
3412 | course): libev guarantees that different event loops share no data |
3898 | of course): libev guarantees that different event loops share no data |
3413 | structures that need any locking. |
3899 | structures that need any locking. |
3414 | .PP |
3900 | .PP |
3415 | Or to put it differently: calls with different loop parameters can be done |
3901 | Or to put it differently: calls with different loop parameters can be done |
3416 | concurrently from multiple threads, calls with the same loop parameter |
3902 | concurrently from multiple threads, calls with the same loop parameter |
3417 | must be done serially (but can be done from different threads, as long as |
3903 | must be done serially (but can be done from different threads, as long as |
… | |
… | |
3452 | .Sp |
3938 | .Sp |
3453 | An example use would be to communicate signals or other events that only |
3939 | An example use would be to communicate signals or other events that only |
3454 | work in the default loop by registering the signal watcher with the |
3940 | work in the default loop by registering the signal watcher with the |
3455 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
3941 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
3456 | watcher callback into the event loop interested in the signal. |
3942 | watcher callback into the event loop interested in the signal. |
3457 | .Sh "\s-1COROUTINES\s0" |
3943 | .PP |
|
|
3944 | \fI\s-1COROUTINES\s0\fR |
3458 | .IX Subsection "COROUTINES" |
3945 | .IX Subsection "COROUTINES" |
|
|
3946 | .PP |
3459 | Libev is much more accommodating to coroutines (\*(L"cooperative threads\*(R"): |
3947 | Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
3460 | libev fully supports nesting calls to it's functions from different |
3948 | libev fully supports nesting calls to its functions from different |
3461 | coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
3949 | coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
3462 | different coroutines and switch freely between both coroutines running the |
3950 | different coroutines, and switch freely between both coroutines running the |
3463 | loop, as long as you don't confuse yourself). The only exception is that |
3951 | loop, as long as you don't confuse yourself). The only exception is that |
3464 | you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
3952 | you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
3465 | .PP |
3953 | .PP |
3466 | Care has been taken to ensure that libev does not keep local state inside |
3954 | Care has been taken to ensure that libev does not keep local state inside |
3467 | \&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow coroutine switches. |
3955 | \&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow for coroutine switches as |
|
|
3956 | they do not call any callbacks. |
|
|
3957 | .Sh "\s-1COMPILER\s0 \s-1WARNINGS\s0" |
|
|
3958 | .IX Subsection "COMPILER WARNINGS" |
|
|
3959 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3960 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3961 | scared by this. |
|
|
3962 | .PP |
|
|
3963 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3964 | has different warnings, and each user has different tastes regarding |
|
|
3965 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
3966 | targeting a specific compiler and compiler-version. |
|
|
3967 | .PP |
|
|
3968 | Another reason is that some compiler warnings require elaborate |
|
|
3969 | workarounds, or other changes to the code that make it less clear and less |
|
|
3970 | maintainable. |
|
|
3971 | .PP |
|
|
3972 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3973 | wrong (because they don't actually warn about the condition their message |
|
|
3974 | seems to warn about). For example, certain older gcc versions had some |
|
|
3975 | warnings that resulted an extreme number of false positives. These have |
|
|
3976 | been fixed, but some people still insist on making code warn-free with |
|
|
3977 | such buggy versions. |
|
|
3978 | .PP |
|
|
3979 | While libev is written to generate as few warnings as possible, |
|
|
3980 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
3981 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3982 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3983 | warnings, not errors, or proof of bugs. |
|
|
3984 | .Sh "\s-1VALGRIND\s0" |
|
|
3985 | .IX Subsection "VALGRIND" |
|
|
3986 | Valgrind has a special section here because it is a popular tool that is |
|
|
3987 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
3988 | .PP |
|
|
3989 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3990 | in libev, then check twice: If valgrind reports something like: |
|
|
3991 | .PP |
|
|
3992 | .Vb 3 |
|
|
3993 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3994 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3995 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3996 | .Ve |
|
|
3997 | .PP |
|
|
3998 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3999 | is not a memleak \- the memory is still being referenced, and didn't leak. |
|
|
4000 | .PP |
|
|
4001 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4002 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4003 | although an acceptable workaround has been found here), or it might be |
|
|
4004 | confused. |
|
|
4005 | .PP |
|
|
4006 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
4007 | make it into some kind of religion. |
|
|
4008 | .PP |
|
|
4009 | If you are unsure about something, feel free to contact the mailing list |
|
|
4010 | with the full valgrind report and an explanation on why you think this |
|
|
4011 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4012 | annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance |
|
|
4013 | of learning how to interpret valgrind properly. |
|
|
4014 | .PP |
|
|
4015 | If you need, for some reason, empty reports from valgrind for your project |
|
|
4016 | I suggest using suppression lists. |
|
|
4017 | .SH "PORTABILITY NOTES" |
|
|
4018 | .IX Header "PORTABILITY NOTES" |
|
|
4019 | .Sh "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0" |
|
|
4020 | .IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
|
|
4021 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
|
|
4022 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
|
|
4023 | model. Libev still offers limited functionality on this platform in |
|
|
4024 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
|
|
4025 | descriptors. This only applies when using Win32 natively, not when using |
|
|
4026 | e.g. cygwin. |
|
|
4027 | .PP |
|
|
4028 | Lifting these limitations would basically require the full |
|
|
4029 | re-implementation of the I/O system. If you are into these kinds of |
|
|
4030 | things, then note that glib does exactly that for you in a very portable |
|
|
4031 | way (note also that glib is the slowest event library known to man). |
|
|
4032 | .PP |
|
|
4033 | There is no supported compilation method available on windows except |
|
|
4034 | embedding it into other applications. |
|
|
4035 | .PP |
|
|
4036 | Sensible signal handling is officially unsupported by Microsoft \- libev |
|
|
4037 | tries its best, but under most conditions, signals will simply not work. |
|
|
4038 | .PP |
|
|
4039 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
4040 | accept large writes: instead of resulting in a partial write, windows will |
|
|
4041 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
|
|
4042 | so make sure you only write small amounts into your sockets (less than a |
|
|
4043 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
4044 | available). |
|
|
4045 | .PP |
|
|
4046 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
4047 | the abysmal performance of winsockets, using a large number of sockets |
|
|
4048 | is not recommended (and not reasonable). If your program needs to use |
|
|
4049 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
4050 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
4051 | notification model, which cannot be implemented efficiently on windows |
|
|
4052 | (due to Microsoft monopoly games). |
|
|
4053 | .PP |
|
|
4054 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
4055 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
4056 | of \fIev.h\fR: |
|
|
4057 | .PP |
|
|
4058 | .Vb 2 |
|
|
4059 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
4060 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
4061 | \& |
|
|
4062 | \& #include "ev.h" |
|
|
4063 | .Ve |
|
|
4064 | .PP |
|
|
4065 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
4066 | you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
|
|
4067 | .PP |
|
|
4068 | .Vb 2 |
|
|
4069 | \& #include "evwrap.h" |
|
|
4070 | \& #include "ev.c" |
|
|
4071 | .Ve |
|
|
4072 | .IP "The winsocket select function" 4 |
|
|
4073 | .IX Item "The winsocket select function" |
|
|
4074 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
4075 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
4076 | also extremely buggy). This makes select very inefficient, and also |
|
|
4077 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
4078 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
4079 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
4080 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
4081 | .Sp |
|
|
4082 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
|
|
4083 | libraries and raw winsocket select is: |
|
|
4084 | .Sp |
|
|
4085 | .Vb 2 |
|
|
4086 | \& #define EV_USE_SELECT 1 |
|
|
4087 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
4088 | .Ve |
|
|
4089 | .Sp |
|
|
4090 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
4091 | complexity in the O(nA\*^X) range when using win32. |
|
|
4092 | .IP "Limited number of file descriptors" 4 |
|
|
4093 | .IX Item "Limited number of file descriptors" |
|
|
4094 | Windows has numerous arbitrary (and low) limits on things. |
|
|
4095 | .Sp |
|
|
4096 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
4097 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
|
|
4098 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
|
|
4099 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
4100 | previous thread in each. Sounds great!). |
|
|
4101 | .Sp |
|
|
4102 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
4103 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
4104 | call (which might be in libev or elsewhere, for example, perl and many |
|
|
4105 | other interpreters do their own select emulation on windows). |
|
|
4106 | .Sp |
|
|
4107 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
4108 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR |
|
|
4109 | fetish or something like this inside Microsoft). You can increase this |
|
|
4110 | by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR |
|
|
4111 | (another arbitrary limit), but is broken in many versions of the Microsoft |
|
|
4112 | runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets |
|
|
4113 | (depending on windows version and/or the phase of the moon). To get more, |
|
|
4114 | you need to wrap all I/O functions and provide your own fd management, but |
|
|
4115 | the cost of calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
4116 | .Sh "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0" |
|
|
4117 | .IX Subsection "PORTABILITY REQUIREMENTS" |
|
|
4118 | In addition to a working ISO-C implementation and of course the |
|
|
4119 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
4120 | .ie n .IP """void (*)(ev_watcher_type *, int revents)""\fR must have compatible calling conventions regardless of \f(CW""ev_watcher_type *""." 4 |
|
|
4121 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
4122 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
4123 | Libev assumes not only that all watcher pointers have the same internal |
|
|
4124 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
4125 | assumes that the same (machine) code can be used to call any watcher |
|
|
4126 | callback: The watcher callbacks have different type signatures, but libev |
|
|
4127 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
4128 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
4129 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
4130 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
4131 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
4132 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
|
|
4133 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
4134 | believed to be sufficiently portable. |
|
|
4135 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
4136 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
4137 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
4138 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
4139 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
4140 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
4141 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
4142 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
4143 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
4144 | .Sp |
|
|
4145 | The most portable way to handle signals is to block signals in all threads |
|
|
4146 | except the initial one, and run the default loop in the initial thread as |
|
|
4147 | well. |
|
|
4148 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
4149 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
4150 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
4151 | To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally |
|
|
4152 | instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX |
|
|
4153 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
4154 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
4155 | watchers. |
|
|
4156 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
4157 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
4158 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
4159 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
4160 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
4161 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
4162 | implementations implementing \s-1IEEE\s0 754 (basically all existing ones). |
|
|
4163 | .PP |
|
|
4164 | If you know of other additional requirements drop me a note. |
3468 | .SH "COMPLEXITIES" |
4165 | .SH "ALGORITHMIC COMPLEXITIES" |
3469 | .IX Header "COMPLEXITIES" |
4166 | .IX Header "ALGORITHMIC COMPLEXITIES" |
3470 | In this section the complexities of (many of) the algorithms used inside |
4167 | In this section the complexities of (many of) the algorithms used inside |
3471 | libev will be explained. For complexity discussions about backends see the |
4168 | libev will be documented. For complexity discussions about backends see |
3472 | documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
4169 | the documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
3473 | .PP |
4170 | .PP |
3474 | All of the following are about amortised time: If an array needs to be |
4171 | All of the following are about amortised time: If an array needs to be |
3475 | extended, libev needs to realloc and move the whole array, but this |
4172 | extended, libev needs to realloc and move the whole array, but this |
3476 | happens asymptotically never with higher number of elements, so O(1) might |
4173 | happens asymptotically rarer with higher number of elements, so O(1) might |
3477 | mean it might do a lengthy realloc operation in rare cases, but on average |
4174 | mean that libev does a lengthy realloc operation in rare cases, but on |
3478 | it is much faster and asymptotically approaches constant time. |
4175 | average it is much faster and asymptotically approaches constant time. |
3479 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
4176 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
3480 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
4177 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
3481 | This means that, when you have a watcher that triggers in one hour and |
4178 | This means that, when you have a watcher that triggers in one hour and |
3482 | there are 100 watchers that would trigger before that then inserting will |
4179 | there are 100 watchers that would trigger before that, then inserting will |
3483 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
4180 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
3484 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
4181 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
3485 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
4182 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
3486 | That means that changing a timer costs less than removing/adding them |
4183 | That means that changing a timer costs less than removing/adding them, |
3487 | as only the relative motion in the event queue has to be paid for. |
4184 | as only the relative motion in the event queue has to be paid for. |
3488 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
4185 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
3489 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
4186 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
3490 | These just add the watcher into an array or at the head of a list. |
4187 | These just add the watcher into an array or at the head of a list. |
3491 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
4188 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
3492 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
4189 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
3493 | .PD 0 |
4190 | .PD 0 |
3494 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
4191 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
3495 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
4192 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
3496 | .PD |
4193 | .PD |
3497 | These watchers are stored in lists then need to be walked to find the |
4194 | These watchers are stored in lists, so they need to be walked to find the |
3498 | correct watcher to remove. The lists are usually short (you don't usually |
4195 | correct watcher to remove. The lists are usually short (you don't usually |
3499 | have many watchers waiting for the same fd or signal). |
4196 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
4197 | is rare). |
3500 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
4198 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
3501 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
4199 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
3502 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
4200 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
3503 | fixed position in the storage array. |
4201 | fixed position in the storage array. |
3504 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
4202 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
… | |
… | |
3525 | .IX Item "Processing signals: O(max_signal_number)" |
4223 | .IX Item "Processing signals: O(max_signal_number)" |
3526 | .PD |
4224 | .PD |
3527 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
4225 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
3528 | calls in the current loop iteration. Checking for async and signal events |
4226 | calls in the current loop iteration. Checking for async and signal events |
3529 | involves iterating over all running async watchers or all signal numbers. |
4227 | involves iterating over all running async watchers or all signal numbers. |
3530 | .SH "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
4228 | .SH "GLOSSARY" |
3531 | .IX Header "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
4229 | .IX Header "GLOSSARY" |
3532 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
4230 | .IP "active" 4 |
3533 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
4231 | .IX Item "active" |
3534 | model. Libev still offers limited functionality on this platform in |
4232 | A watcher is active as long as it has been started (has been attached to |
3535 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
4233 | an event loop) but not yet stopped (disassociated from the event loop). |
3536 | descriptors. This only applies when using Win32 natively, not when using |
4234 | .IP "application" 4 |
3537 | e.g. cygwin. |
4235 | .IX Item "application" |
3538 | .PP |
4236 | In this document, an application is whatever is using libev. |
3539 | Lifting these limitations would basically require the full |
4237 | .IP "callback" 4 |
3540 | re-implementation of the I/O system. If you are into these kinds of |
4238 | .IX Item "callback" |
3541 | things, then note that glib does exactly that for you in a very portable |
4239 | The address of a function that is called when some event has been |
3542 | way (note also that glib is the slowest event library known to man). |
4240 | detected. Callbacks are being passed the event loop, the watcher that |
3543 | .PP |
4241 | received the event, and the actual event bitset. |
3544 | There is no supported compilation method available on windows except |
4242 | .IP "callback invocation" 4 |
3545 | embedding it into other applications. |
4243 | .IX Item "callback invocation" |
3546 | .PP |
4244 | The act of calling the callback associated with a watcher. |
3547 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4245 | .IP "event" 4 |
3548 | accept large writes: instead of resulting in a partial write, windows will |
4246 | .IX Item "event" |
3549 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
4247 | A change of state of some external event, such as data now being available |
3550 | so make sure you only write small amounts into your sockets (less than a |
4248 | for reading on a file descriptor, time having passed or simply not having |
3551 | megabyte seems safe, but this apparently depends on the amount of memory |
4249 | any other events happening anymore. |
3552 | available). |
|
|
3553 | .PP |
|
|
3554 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3555 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3556 | is not recommended (and not reasonable). If your program needs to use |
|
|
3557 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3558 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
3559 | notification model, which cannot be implemented efficiently on windows |
|
|
3560 | (Microsoft monopoly games). |
|
|
3561 | .PP |
|
|
3562 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3563 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
3564 | of \fIev.h\fR: |
|
|
3565 | .PP |
|
|
3566 | .Vb 2 |
|
|
3567 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3568 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3569 | \& |
|
|
3570 | \& #include "ev.h" |
|
|
3571 | .Ve |
|
|
3572 | .PP |
|
|
3573 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
3574 | you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
|
|
3575 | .PP |
|
|
3576 | .Vb 2 |
|
|
3577 | \& #include "evwrap.h" |
|
|
3578 | \& #include "ev.c" |
|
|
3579 | .Ve |
|
|
3580 | .IP "The winsocket select function" 4 |
|
|
3581 | .IX Item "The winsocket select function" |
|
|
3582 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
3583 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
3584 | also extremely buggy). This makes select very inefficient, and also |
|
|
3585 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3586 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
3587 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
3588 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
3589 | .Sp |
4250 | .Sp |
3590 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
4251 | In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or |
3591 | libraries and raw winsocket select is: |
4252 | \&\f(CW\*(C`EV_TIMEOUT\*(C'\fR). |
|
|
4253 | .IP "event library" 4 |
|
|
4254 | .IX Item "event library" |
|
|
4255 | A software package implementing an event model and loop. |
|
|
4256 | .IP "event loop" 4 |
|
|
4257 | .IX Item "event loop" |
|
|
4258 | An entity that handles and processes external events and converts them |
|
|
4259 | into callback invocations. |
|
|
4260 | .IP "event model" 4 |
|
|
4261 | .IX Item "event model" |
|
|
4262 | The model used to describe how an event loop handles and processes |
|
|
4263 | watchers and events. |
|
|
4264 | .IP "pending" 4 |
|
|
4265 | .IX Item "pending" |
|
|
4266 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4267 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4268 | pending status is explicitly cleared by the application. |
3592 | .Sp |
4269 | .Sp |
3593 | .Vb 2 |
4270 | A watcher can be pending, but not active. Stopping a watcher also clears |
3594 | \& #define EV_USE_SELECT 1 |
4271 | its pending status. |
3595 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4272 | .IP "real time" 4 |
3596 | .Ve |
4273 | .IX Item "real time" |
3597 | .Sp |
4274 | The physical time that is observed. It is apparently strictly monotonic :) |
3598 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4275 | .IP "wall-clock time" 4 |
3599 | complexity in the O(nA\*^X) range when using win32. |
4276 | .IX Item "wall-clock time" |
3600 | .IP "Limited number of file descriptors" 4 |
4277 | The time and date as shown on clocks. Unlike real time, it can actually |
3601 | .IX Item "Limited number of file descriptors" |
4278 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
3602 | Windows has numerous arbitrary (and low) limits on things. |
4279 | clock. |
3603 | .Sp |
4280 | .IP "watcher" 4 |
3604 | Early versions of winsocket's select only supported waiting for a maximum |
4281 | .IX Item "watcher" |
3605 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
4282 | A data structure that describes interest in certain events. Watchers need |
3606 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
4283 | to be started (attached to an event loop) before they can receive events. |
3607 | recommends spawning a chain of threads and wait for 63 handles and the |
4284 | .IP "watcher invocation" 4 |
3608 | previous thread in each. Great). |
4285 | .IX Item "watcher invocation" |
3609 | .Sp |
4286 | The act of calling the callback associated with a watcher. |
3610 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
3611 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
3612 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3613 | select emulation on windows). |
|
|
3614 | .Sp |
|
|
3615 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3616 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish |
|
|
3617 | or something like this inside Microsoft). You can increase this by calling |
|
|
3618 | \&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another |
|
|
3619 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3620 | libraries. |
|
|
3621 | .Sp |
|
|
3622 | This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on |
|
|
3623 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3624 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3625 | calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
3626 | .SH "PORTABILITY REQUIREMENTS" |
|
|
3627 | .IX Header "PORTABILITY REQUIREMENTS" |
|
|
3628 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3629 | additional extensions: |
|
|
3630 | .ie n .IP """void (*)(ev_watcher_type *, int revents)""\fR must have compatible calling conventions regardless of \f(CW""ev_watcher_type *""." 4 |
|
|
3631 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
3632 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
3633 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3634 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
3635 | assumes that the same (machine) code can be used to call any watcher |
|
|
3636 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3637 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
3638 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
3639 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
3640 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
3641 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
3642 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
|
|
3643 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
3644 | believed to be sufficiently portable. |
|
|
3645 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
3646 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
3647 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
3648 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
3649 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
3650 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
3651 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
3652 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
3653 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
3654 | .Sp |
|
|
3655 | The most portable way to handle signals is to block signals in all threads |
|
|
3656 | except the initial one, and run the default loop in the initial thread as |
|
|
3657 | well. |
|
|
3658 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
3659 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
3660 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
3661 | To improve portability and simplify using libev, libev uses \f(CW\*(C`long\*(C'\fR |
|
|
3662 | internally instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On |
|
|
3663 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3664 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3665 | millions of watchers. |
|
|
3666 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
3667 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
3668 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
3669 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
3670 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3671 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3672 | implementations implementing \s-1IEEE\s0 754 (basically all existing ones). |
|
|
3673 | .PP |
|
|
3674 | If you know of other additional requirements drop me a note. |
|
|
3675 | .SH "COMPILER WARNINGS" |
|
|
3676 | .IX Header "COMPILER WARNINGS" |
|
|
3677 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3678 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3679 | scared by this. |
|
|
3680 | .PP |
|
|
3681 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3682 | has different warnings, and each user has different tastes regarding |
|
|
3683 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
3684 | targeting a specific compiler and compiler-version. |
|
|
3685 | .PP |
|
|
3686 | Another reason is that some compiler warnings require elaborate |
|
|
3687 | workarounds, or other changes to the code that make it less clear and less |
|
|
3688 | maintainable. |
|
|
3689 | .PP |
|
|
3690 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3691 | wrong (because they don't actually warn about the condition their message |
|
|
3692 | seems to warn about). |
|
|
3693 | .PP |
|
|
3694 | While libev is written to generate as few warnings as possible, |
|
|
3695 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
3696 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3697 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3698 | warnings, not errors, or proof of bugs. |
|
|
3699 | .SH "VALGRIND" |
|
|
3700 | .IX Header "VALGRIND" |
|
|
3701 | Valgrind has a special section here because it is a popular tool that is |
|
|
3702 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3703 | .PP |
|
|
3704 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3705 | in libev, then check twice: If valgrind reports something like: |
|
|
3706 | .PP |
|
|
3707 | .Vb 3 |
|
|
3708 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3709 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3710 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3711 | .Ve |
|
|
3712 | .PP |
|
|
3713 | Then there is no memory leak. Similarly, under some circumstances, |
|
|
3714 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3715 | might be confused (it is a very good tool, but only a tool). |
|
|
3716 | .PP |
|
|
3717 | If you are unsure about something, feel free to contact the mailing list |
|
|
3718 | with the full valgrind report and an explanation on why you think this is |
|
|
3719 | a bug in libev. However, don't be annoyed when you get a brisk \*(L"this is |
|
|
3720 | no bug\*(R" answer and take the chance of learning how to interpret valgrind |
|
|
3721 | properly. |
|
|
3722 | .PP |
|
|
3723 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3724 | I suggest using suppression lists. |
|
|
3725 | .SH "AUTHOR" |
4287 | .SH "AUTHOR" |
3726 | .IX Header "AUTHOR" |
4288 | .IX Header "AUTHOR" |
3727 | Marc Lehmann <libev@schmorp.de>. |
4289 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |