… | |
… | |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
68 | |
70 | |
69 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
70 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
71 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familiarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
72 | |
84 | |
73 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
74 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
75 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
76 | |
88 | |
… | |
… | |
86 | =head2 FEATURES |
98 | =head2 FEATURES |
87 | |
99 | |
88 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
89 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
90 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
91 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
92 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
93 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
94 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
95 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
96 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
97 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
98 | |
111 | |
99 | It also is quite fast (see this |
112 | It also is quite fast (see this |
100 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
101 | for example). |
114 | for example). |
102 | |
115 | |
… | |
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105 | Libev is very configurable. In this manual the default (and most common) |
118 | Libev is very configurable. In this manual the default (and most common) |
106 | configuration will be described, which supports multiple event loops. For |
119 | configuration will be described, which supports multiple event loops. For |
107 | more info about various configuration options please have a look at |
120 | more info about various configuration options please have a look at |
108 | B<EMBED> section in this manual. If libev was configured without support |
121 | B<EMBED> section in this manual. If libev was configured without support |
109 | for multiple event loops, then all functions taking an initial argument of |
122 | for multiple event loops, then all functions taking an initial argument of |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
111 | this argument. |
124 | this argument. |
112 | |
125 | |
113 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
114 | |
127 | |
115 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practise |
117 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | somewhere near the beginning of 1970, details are complicated, don't |
118 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
119 | to the C<double> type in C, and when you need to do any calculations on |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
120 | it, you should treat it as some floating point value. Unlike the name |
133 | any calculations on it, you should treat it as some floating point value. |
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134 | |
121 | component C<stamp> might indicate, it is also used for time differences |
135 | Unlike the name component C<stamp> might indicate, it is also used for |
122 | throughout libev. |
136 | time differences (e.g. delays) throughout libev. |
123 | |
137 | |
124 | =head1 ERROR HANDLING |
138 | =head1 ERROR HANDLING |
125 | |
139 | |
126 | Libev knows three classes of errors: operating system errors, usage errors |
140 | Libev knows three classes of errors: operating system errors, usage errors |
127 | and internal errors (bugs). |
141 | and internal errors (bugs). |
… | |
… | |
178 | as this indicates an incompatible change. Minor versions are usually |
192 | as this indicates an incompatible change. Minor versions are usually |
179 | compatible to older versions, so a larger minor version alone is usually |
193 | compatible to older versions, so a larger minor version alone is usually |
180 | not a problem. |
194 | not a problem. |
181 | |
195 | |
182 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
183 | version. |
197 | version (note, however, that this will not detect ABI mismatches :). |
184 | |
198 | |
185 | assert (("libev version mismatch", |
199 | assert (("libev version mismatch", |
186 | ev_version_major () == EV_VERSION_MAJOR |
200 | ev_version_major () == EV_VERSION_MAJOR |
187 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
188 | |
202 | |
… | |
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332 | useful to try out specific backends to test their performance, or to work |
346 | useful to try out specific backends to test their performance, or to work |
333 | around bugs. |
347 | around bugs. |
334 | |
348 | |
335 | =item C<EVFLAG_FORKCHECK> |
349 | =item C<EVFLAG_FORKCHECK> |
336 | |
350 | |
337 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
351 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
338 | a fork, you can also make libev check for a fork in each iteration by |
352 | make libev check for a fork in each iteration by enabling this flag. |
339 | enabling this flag. |
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340 | |
353 | |
341 | This works by calling C<getpid ()> on every iteration of the loop, |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
342 | and thus this might slow down your event loop if you do a lot of loop |
355 | and thus this might slow down your event loop if you do a lot of loop |
343 | iterations and little real work, but is usually not noticeable (on my |
356 | iterations and little real work, but is usually not noticeable (on my |
344 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
350 | flag. |
363 | flag. |
351 | |
364 | |
352 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
353 | environment variable. |
366 | environment variable. |
354 | |
367 | |
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368 | =item C<EVFLAG_NOINOTIFY> |
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369 | |
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370 | When this flag is specified, then libev will not attempt to use the |
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371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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372 | testing, this flag can be useful to conserve inotify file descriptors, as |
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373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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374 | |
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375 | =item C<EVFLAG_SIGNALFD> |
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376 | |
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377 | When this flag is specified, then libev will attempt to use the |
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378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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379 | delivers signals synchronously, which makes it both faster and might make |
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380 | it possible to get the queued signal data. It can also simplify signal |
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381 | handling with threads, as long as you properly block signals in your |
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382 | threads that are not interested in handling them. |
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383 | |
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384 | Signalfd will not be used by default as this changes your signal mask, and |
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385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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386 | example) that can't properly initialise their signal masks. |
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387 | |
355 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
356 | |
389 | |
357 | This is your standard select(2) backend. Not I<completely> standard, as |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
358 | libev tries to roll its own fd_set with no limits on the number of fds, |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
359 | but if that fails, expect a fairly low limit on the number of fds when |
392 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
382 | |
415 | |
383 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
416 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
384 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
417 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
385 | |
418 | |
386 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
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420 | |
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421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
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422 | kernels). |
387 | |
423 | |
388 | For few fds, this backend is a bit little slower than poll and select, |
424 | For few fds, this backend is a bit little slower than poll and select, |
389 | but it scales phenomenally better. While poll and select usually scale |
425 | but it scales phenomenally better. While poll and select usually scale |
390 | like O(total_fds) where n is the total number of fds (or the highest fd), |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
391 | epoll scales either O(1) or O(active_fds). |
427 | epoll scales either O(1) or O(active_fds). |
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403 | of course I<doesn't>, and epoll just loves to report events for totally |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
404 | I<different> file descriptors (even already closed ones, so one cannot |
440 | I<different> file descriptors (even already closed ones, so one cannot |
405 | even remove them from the set) than registered in the set (especially |
441 | even remove them from the set) than registered in the set (especially |
406 | on SMP systems). Libev tries to counter these spurious notifications by |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
407 | employing an additional generation counter and comparing that against the |
443 | employing an additional generation counter and comparing that against the |
408 | events to filter out spurious ones, recreating the set when required. |
444 | events to filter out spurious ones, recreating the set when required. Last |
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445 | not least, it also refuses to work with some file descriptors which work |
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446 | perfectly fine with C<select> (files, many character devices...). |
409 | |
447 | |
410 | While stopping, setting and starting an I/O watcher in the same iteration |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
411 | will result in some caching, there is still a system call per such |
449 | will result in some caching, there is still a system call per such |
412 | incident (because the same I<file descriptor> could point to a different |
450 | incident (because the same I<file descriptor> could point to a different |
413 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
451 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
506 | |
544 | |
507 | It is definitely not recommended to use this flag. |
545 | It is definitely not recommended to use this flag. |
508 | |
546 | |
509 | =back |
547 | =back |
510 | |
548 | |
511 | If one or more of these are or'ed into the flags value, then only these |
549 | If one or more of the backend flags are or'ed into the flags value, |
512 | backends will be tried (in the reverse order as listed here). If none are |
550 | then only these backends will be tried (in the reverse order as listed |
513 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
551 | here). If none are specified, all backends in C<ev_recommended_backends |
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552 | ()> will be tried. |
514 | |
553 | |
515 | Example: This is the most typical usage. |
554 | Example: This is the most typical usage. |
516 | |
555 | |
517 | if (!ev_default_loop (0)) |
556 | if (!ev_default_loop (0)) |
518 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
557 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
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530 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
569 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
531 | |
570 | |
532 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
571 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
533 | |
572 | |
534 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
573 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
535 | always distinct from the default loop. Unlike the default loop, it cannot |
574 | always distinct from the default loop. |
536 | handle signal and child watchers, and attempts to do so will be greeted by |
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537 | undefined behaviour (or a failed assertion if assertions are enabled). |
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538 | |
575 | |
539 | Note that this function I<is> thread-safe, and the recommended way to use |
576 | Note that this function I<is> thread-safe, and one common way to use |
540 | libev with threads is indeed to create one loop per thread, and using the |
577 | libev with threads is indeed to create one loop per thread, and using the |
541 | default loop in the "main" or "initial" thread. |
578 | default loop in the "main" or "initial" thread. |
542 | |
579 | |
543 | Example: Try to create a event loop that uses epoll and nothing else. |
580 | Example: Try to create a event loop that uses epoll and nothing else. |
544 | |
581 | |
… | |
… | |
546 | if (!epoller) |
583 | if (!epoller) |
547 | fatal ("no epoll found here, maybe it hides under your chair"); |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
548 | |
585 | |
549 | =item ev_default_destroy () |
586 | =item ev_default_destroy () |
550 | |
587 | |
551 | Destroys the default loop again (frees all memory and kernel state |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
552 | etc.). None of the active event watchers will be stopped in the normal |
589 | of the active event watchers will be stopped in the normal sense, so |
553 | sense, so e.g. C<ev_is_active> might still return true. It is your |
590 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
554 | responsibility to either stop all watchers cleanly yourself I<before> |
591 | either stop all watchers cleanly yourself I<before> calling this function, |
555 | calling this function, or cope with the fact afterwards (which is usually |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
556 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
593 | can just ignore the watchers and/or C<free ()> them for example). |
557 | for example). |
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558 | |
594 | |
559 | Note that certain global state, such as signal state (and installed signal |
595 | Note that certain global state, such as signal state (and installed signal |
560 | handlers), will not be freed by this function, and related watchers (such |
596 | handlers), will not be freed by this function, and related watchers (such |
561 | as signal and child watchers) would need to be stopped manually. |
597 | as signal and child watchers) would need to be stopped manually. |
562 | |
598 | |
563 | In general it is not advisable to call this function except in the |
599 | In general it is not advisable to call this function except in the |
564 | rare occasion where you really need to free e.g. the signal handling |
600 | rare occasion where you really need to free e.g. the signal handling |
565 | pipe fds. If you need dynamically allocated loops it is better to use |
601 | pipe fds. If you need dynamically allocated loops it is better to use |
566 | C<ev_loop_new> and C<ev_loop_destroy>). |
602 | C<ev_loop_new> and C<ev_loop_destroy>. |
567 | |
603 | |
568 | =item ev_loop_destroy (loop) |
604 | =item ev_loop_destroy (loop) |
569 | |
605 | |
570 | Like C<ev_default_destroy>, but destroys an event loop created by an |
606 | Like C<ev_default_destroy>, but destroys an event loop created by an |
571 | earlier call to C<ev_loop_new>. |
607 | earlier call to C<ev_loop_new>. |
… | |
… | |
577 | name, you can call it anytime, but it makes most sense after forking, in |
613 | name, you can call it anytime, but it makes most sense after forking, in |
578 | the child process (or both child and parent, but that again makes little |
614 | the child process (or both child and parent, but that again makes little |
579 | sense). You I<must> call it in the child before using any of the libev |
615 | sense). You I<must> call it in the child before using any of the libev |
580 | functions, and it will only take effect at the next C<ev_loop> iteration. |
616 | functions, and it will only take effect at the next C<ev_loop> iteration. |
581 | |
617 | |
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618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
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619 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
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620 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
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621 | during fork. |
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622 | |
582 | On the other hand, you only need to call this function in the child |
623 | On the other hand, you only need to call this function in the child |
583 | process if and only if you want to use the event library in the child. If |
624 | process if and only if you want to use the event loop in the child. If you |
584 | you just fork+exec, you don't have to call it at all. |
625 | just fork+exec or create a new loop in the child, you don't have to call |
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626 | it at all. |
585 | |
627 | |
586 | The function itself is quite fast and it's usually not a problem to call |
628 | The function itself is quite fast and it's usually not a problem to call |
587 | it just in case after a fork. To make this easy, the function will fit in |
629 | it just in case after a fork. To make this easy, the function will fit in |
588 | quite nicely into a call to C<pthread_atfork>: |
630 | quite nicely into a call to C<pthread_atfork>: |
589 | |
631 | |
… | |
… | |
591 | |
633 | |
592 | =item ev_loop_fork (loop) |
634 | =item ev_loop_fork (loop) |
593 | |
635 | |
594 | Like C<ev_default_fork>, but acts on an event loop created by |
636 | Like C<ev_default_fork>, but acts on an event loop created by |
595 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
637 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
596 | after fork that you want to re-use in the child, and how you do this is |
638 | after fork that you want to re-use in the child, and how you keep track of |
597 | entirely your own problem. |
639 | them is entirely your own problem. |
598 | |
640 | |
599 | =item int ev_is_default_loop (loop) |
641 | =item int ev_is_default_loop (loop) |
600 | |
642 | |
601 | Returns true when the given loop is, in fact, the default loop, and false |
643 | Returns true when the given loop is, in fact, the default loop, and false |
602 | otherwise. |
644 | otherwise. |
603 | |
645 | |
604 | =item unsigned int ev_loop_count (loop) |
646 | =item unsigned int ev_iteration (loop) |
605 | |
647 | |
606 | Returns the count of loop iterations for the loop, which is identical to |
648 | Returns the current iteration count for the loop, which is identical to |
607 | the number of times libev did poll for new events. It starts at C<0> and |
649 | the number of times libev did poll for new events. It starts at C<0> and |
608 | happily wraps around with enough iterations. |
650 | happily wraps around with enough iterations. |
609 | |
651 | |
610 | This value can sometimes be useful as a generation counter of sorts (it |
652 | This value can sometimes be useful as a generation counter of sorts (it |
611 | "ticks" the number of loop iterations), as it roughly corresponds with |
653 | "ticks" the number of loop iterations), as it roughly corresponds with |
612 | C<ev_prepare> and C<ev_check> calls. |
654 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
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655 | prepare and check phases. |
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656 | |
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657 | =item unsigned int ev_depth (loop) |
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658 | |
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659 | Returns the number of times C<ev_loop> was entered minus the number of |
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660 | times C<ev_loop> was exited, in other words, the recursion depth. |
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661 | |
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662 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
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663 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
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664 | in which case it is higher. |
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665 | |
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666 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
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667 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
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668 | ungentleman behaviour unless it's really convenient. |
613 | |
669 | |
614 | =item unsigned int ev_backend (loop) |
670 | =item unsigned int ev_backend (loop) |
615 | |
671 | |
616 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
672 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
617 | use. |
673 | use. |
… | |
… | |
632 | |
688 | |
633 | This function is rarely useful, but when some event callback runs for a |
689 | This function is rarely useful, but when some event callback runs for a |
634 | very long time without entering the event loop, updating libev's idea of |
690 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
691 | the current time is a good idea. |
636 | |
692 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
693 | See also L<The special problem of time updates> in the C<ev_timer> section. |
638 | |
694 | |
639 | =item ev_suspend (loop) |
695 | =item ev_suspend (loop) |
640 | |
696 | |
641 | =item ev_resume (loop) |
697 | =item ev_resume (loop) |
642 | |
698 | |
… | |
… | |
651 | C<ev_resume> directly afterwards to resume timer processing. |
707 | C<ev_resume> directly afterwards to resume timer processing. |
652 | |
708 | |
653 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
709 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
654 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
710 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
655 | will be rescheduled (that is, they will lose any events that would have |
711 | will be rescheduled (that is, they will lose any events that would have |
656 | occured while suspended). |
712 | occurred while suspended). |
657 | |
713 | |
658 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
714 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
659 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
715 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
660 | without a previous call to C<ev_suspend>. |
716 | without a previous call to C<ev_suspend>. |
661 | |
717 | |
… | |
… | |
663 | event loop time (see C<ev_now_update>). |
719 | event loop time (see C<ev_now_update>). |
664 | |
720 | |
665 | =item ev_loop (loop, int flags) |
721 | =item ev_loop (loop, int flags) |
666 | |
722 | |
667 | Finally, this is it, the event handler. This function usually is called |
723 | Finally, this is it, the event handler. This function usually is called |
668 | after you initialised all your watchers and you want to start handling |
724 | after you have initialised all your watchers and you want to start |
669 | events. |
725 | handling events. |
670 | |
726 | |
671 | If the flags argument is specified as C<0>, it will not return until |
727 | If the flags argument is specified as C<0>, it will not return until |
672 | either no event watchers are active anymore or C<ev_unloop> was called. |
728 | either no event watchers are active anymore or C<ev_unloop> was called. |
673 | |
729 | |
674 | Please note that an explicit C<ev_unloop> is usually better than |
730 | Please note that an explicit C<ev_unloop> is usually better than |
… | |
… | |
738 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
794 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
739 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
795 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
740 | |
796 | |
741 | This "unloop state" will be cleared when entering C<ev_loop> again. |
797 | This "unloop state" will be cleared when entering C<ev_loop> again. |
742 | |
798 | |
743 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
799 | It is safe to call C<ev_unloop> from outside any C<ev_loop> calls. |
744 | |
800 | |
745 | =item ev_ref (loop) |
801 | =item ev_ref (loop) |
746 | |
802 | |
747 | =item ev_unref (loop) |
803 | =item ev_unref (loop) |
748 | |
804 | |
749 | Ref/unref can be used to add or remove a reference count on the event |
805 | Ref/unref can be used to add or remove a reference count on the event |
750 | loop: Every watcher keeps one reference, and as long as the reference |
806 | loop: Every watcher keeps one reference, and as long as the reference |
751 | count is nonzero, C<ev_loop> will not return on its own. |
807 | count is nonzero, C<ev_loop> will not return on its own. |
752 | |
808 | |
753 | If you have a watcher you never unregister that should not keep C<ev_loop> |
809 | This is useful when you have a watcher that you never intend to |
754 | from returning, call ev_unref() after starting, and ev_ref() before |
810 | unregister, but that nevertheless should not keep C<ev_loop> from |
|
|
811 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
755 | stopping it. |
812 | before stopping it. |
756 | |
813 | |
757 | As an example, libev itself uses this for its internal signal pipe: It |
814 | As an example, libev itself uses this for its internal signal pipe: It |
758 | is not visible to the libev user and should not keep C<ev_loop> from |
815 | is not visible to the libev user and should not keep C<ev_loop> from |
759 | exiting if no event watchers registered by it are active. It is also an |
816 | exiting if no event watchers registered by it are active. It is also an |
760 | excellent way to do this for generic recurring timers or from within |
817 | excellent way to do this for generic recurring timers or from within |
… | |
… | |
799 | |
856 | |
800 | By setting a higher I<io collect interval> you allow libev to spend more |
857 | By setting a higher I<io collect interval> you allow libev to spend more |
801 | time collecting I/O events, so you can handle more events per iteration, |
858 | time collecting I/O events, so you can handle more events per iteration, |
802 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
859 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
803 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
860 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
804 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
861 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
862 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
863 | once per this interval, on average. |
805 | |
864 | |
806 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
865 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
807 | to spend more time collecting timeouts, at the expense of increased |
866 | to spend more time collecting timeouts, at the expense of increased |
808 | latency/jitter/inexactness (the watcher callback will be called |
867 | latency/jitter/inexactness (the watcher callback will be called |
809 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
868 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
811 | |
870 | |
812 | Many (busy) programs can usually benefit by setting the I/O collect |
871 | Many (busy) programs can usually benefit by setting the I/O collect |
813 | interval to a value near C<0.1> or so, which is often enough for |
872 | interval to a value near C<0.1> or so, which is often enough for |
814 | interactive servers (of course not for games), likewise for timeouts. It |
873 | interactive servers (of course not for games), likewise for timeouts. It |
815 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
874 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
816 | as this approaches the timing granularity of most systems. |
875 | as this approaches the timing granularity of most systems. Note that if |
|
|
876 | you do transactions with the outside world and you can't increase the |
|
|
877 | parallelity, then this setting will limit your transaction rate (if you |
|
|
878 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
879 | then you can't do more than 100 transactions per second). |
817 | |
880 | |
818 | Setting the I<timeout collect interval> can improve the opportunity for |
881 | Setting the I<timeout collect interval> can improve the opportunity for |
819 | saving power, as the program will "bundle" timer callback invocations that |
882 | saving power, as the program will "bundle" timer callback invocations that |
820 | are "near" in time together, by delaying some, thus reducing the number of |
883 | are "near" in time together, by delaying some, thus reducing the number of |
821 | times the process sleeps and wakes up again. Another useful technique to |
884 | times the process sleeps and wakes up again. Another useful technique to |
822 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
885 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
823 | they fire on, say, one-second boundaries only. |
886 | they fire on, say, one-second boundaries only. |
824 | |
887 | |
|
|
888 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
889 | more often than 100 times per second: |
|
|
890 | |
|
|
891 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
892 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
893 | |
|
|
894 | =item ev_invoke_pending (loop) |
|
|
895 | |
|
|
896 | This call will simply invoke all pending watchers while resetting their |
|
|
897 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
898 | but when overriding the invoke callback this call comes handy. |
|
|
899 | |
|
|
900 | =item int ev_pending_count (loop) |
|
|
901 | |
|
|
902 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
903 | are pending. |
|
|
904 | |
|
|
905 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
906 | |
|
|
907 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
908 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
909 | this callback instead. This is useful, for example, when you want to |
|
|
910 | invoke the actual watchers inside another context (another thread etc.). |
|
|
911 | |
|
|
912 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
913 | callback. |
|
|
914 | |
|
|
915 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
916 | |
|
|
917 | Sometimes you want to share the same loop between multiple threads. This |
|
|
918 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
919 | each call to a libev function. |
|
|
920 | |
|
|
921 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
922 | wait for it to return. One way around this is to wake up the loop via |
|
|
923 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
924 | and I<acquire> callbacks on the loop. |
|
|
925 | |
|
|
926 | When set, then C<release> will be called just before the thread is |
|
|
927 | suspended waiting for new events, and C<acquire> is called just |
|
|
928 | afterwards. |
|
|
929 | |
|
|
930 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
931 | C<acquire> will just call the mutex_lock function again. |
|
|
932 | |
|
|
933 | While event loop modifications are allowed between invocations of |
|
|
934 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
935 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
936 | have no effect on the set of file descriptors being watched, or the time |
|
|
937 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
938 | to take note of any changes you made. |
|
|
939 | |
|
|
940 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
941 | invocations of C<release> and C<acquire>. |
|
|
942 | |
|
|
943 | See also the locking example in the C<THREADS> section later in this |
|
|
944 | document. |
|
|
945 | |
|
|
946 | =item ev_set_userdata (loop, void *data) |
|
|
947 | |
|
|
948 | =item ev_userdata (loop) |
|
|
949 | |
|
|
950 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
951 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
952 | C<0.> |
|
|
953 | |
|
|
954 | These two functions can be used to associate arbitrary data with a loop, |
|
|
955 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
956 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
957 | any other purpose as well. |
|
|
958 | |
825 | =item ev_loop_verify (loop) |
959 | =item ev_loop_verify (loop) |
826 | |
960 | |
827 | This function only does something when C<EV_VERIFY> support has been |
961 | This function only does something when C<EV_VERIFY> support has been |
828 | compiled in, which is the default for non-minimal builds. It tries to go |
962 | compiled in, which is the default for non-minimal builds. It tries to go |
829 | through all internal structures and checks them for validity. If anything |
963 | through all internal structures and checks them for validity. If anything |
… | |
… | |
905 | =item C<EV_WRITE> |
1039 | =item C<EV_WRITE> |
906 | |
1040 | |
907 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1041 | The file descriptor in the C<ev_io> watcher has become readable and/or |
908 | writable. |
1042 | writable. |
909 | |
1043 | |
910 | =item C<EV_TIMEOUT> |
1044 | =item C<EV_TIMER> |
911 | |
1045 | |
912 | The C<ev_timer> watcher has timed out. |
1046 | The C<ev_timer> watcher has timed out. |
913 | |
1047 | |
914 | =item C<EV_PERIODIC> |
1048 | =item C<EV_PERIODIC> |
915 | |
1049 | |
… | |
… | |
1005 | |
1139 | |
1006 | ev_io w; |
1140 | ev_io w; |
1007 | ev_init (&w, my_cb); |
1141 | ev_init (&w, my_cb); |
1008 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1142 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1009 | |
1143 | |
1010 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1144 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
1011 | |
1145 | |
1012 | This macro initialises the type-specific parts of a watcher. You need to |
1146 | This macro initialises the type-specific parts of a watcher. You need to |
1013 | call C<ev_init> at least once before you call this macro, but you can |
1147 | call C<ev_init> at least once before you call this macro, but you can |
1014 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1148 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1015 | macro on a watcher that is active (it can be pending, however, which is a |
1149 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
1028 | |
1162 | |
1029 | Example: Initialise and set an C<ev_io> watcher in one step. |
1163 | Example: Initialise and set an C<ev_io> watcher in one step. |
1030 | |
1164 | |
1031 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1165 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1032 | |
1166 | |
1033 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1167 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
1034 | |
1168 | |
1035 | Starts (activates) the given watcher. Only active watchers will receive |
1169 | Starts (activates) the given watcher. Only active watchers will receive |
1036 | events. If the watcher is already active nothing will happen. |
1170 | events. If the watcher is already active nothing will happen. |
1037 | |
1171 | |
1038 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1172 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1039 | whole section. |
1173 | whole section. |
1040 | |
1174 | |
1041 | ev_io_start (EV_DEFAULT_UC, &w); |
1175 | ev_io_start (EV_DEFAULT_UC, &w); |
1042 | |
1176 | |
1043 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1177 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1044 | |
1178 | |
1045 | Stops the given watcher if active, and clears the pending status (whether |
1179 | Stops the given watcher if active, and clears the pending status (whether |
1046 | the watcher was active or not). |
1180 | the watcher was active or not). |
1047 | |
1181 | |
1048 | It is possible that stopped watchers are pending - for example, |
1182 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1073 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1207 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1074 | |
1208 | |
1075 | Change the callback. You can change the callback at virtually any time |
1209 | Change the callback. You can change the callback at virtually any time |
1076 | (modulo threads). |
1210 | (modulo threads). |
1077 | |
1211 | |
1078 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1212 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1079 | |
1213 | |
1080 | =item int ev_priority (ev_TYPE *watcher) |
1214 | =item int ev_priority (ev_TYPE *watcher) |
1081 | |
1215 | |
1082 | Set and query the priority of the watcher. The priority is a small |
1216 | Set and query the priority of the watcher. The priority is a small |
1083 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1217 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
… | |
… | |
1096 | or might not have been clamped to the valid range. |
1230 | or might not have been clamped to the valid range. |
1097 | |
1231 | |
1098 | The default priority used by watchers when no priority has been set is |
1232 | The default priority used by watchers when no priority has been set is |
1099 | always C<0>, which is supposed to not be too high and not be too low :). |
1233 | always C<0>, which is supposed to not be too high and not be too low :). |
1100 | |
1234 | |
1101 | See L<WATCHER PRIORITIES>, below, for a more thorough treatment of |
1235 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1102 | priorities. |
1236 | priorities. |
1103 | |
1237 | |
1104 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1238 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1105 | |
1239 | |
1106 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1240 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1114 | returns its C<revents> bitset (as if its callback was invoked). If the |
1248 | returns its C<revents> bitset (as if its callback was invoked). If the |
1115 | watcher isn't pending it does nothing and returns C<0>. |
1249 | watcher isn't pending it does nothing and returns C<0>. |
1116 | |
1250 | |
1117 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1251 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1118 | callback to be invoked, which can be accomplished with this function. |
1252 | callback to be invoked, which can be accomplished with this function. |
|
|
1253 | |
|
|
1254 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1255 | |
|
|
1256 | Feeds the given event set into the event loop, as if the specified event |
|
|
1257 | had happened for the specified watcher (which must be a pointer to an |
|
|
1258 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1259 | not free the watcher as long as it has pending events. |
|
|
1260 | |
|
|
1261 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1262 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1263 | not started in the first place. |
|
|
1264 | |
|
|
1265 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1266 | functions that do not need a watcher. |
1119 | |
1267 | |
1120 | =back |
1268 | =back |
1121 | |
1269 | |
1122 | |
1270 | |
1123 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1271 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
1172 | #include <stddef.h> |
1320 | #include <stddef.h> |
1173 | |
1321 | |
1174 | static void |
1322 | static void |
1175 | t1_cb (EV_P_ ev_timer *w, int revents) |
1323 | t1_cb (EV_P_ ev_timer *w, int revents) |
1176 | { |
1324 | { |
1177 | struct my_biggy big = (struct my_biggy * |
1325 | struct my_biggy big = (struct my_biggy *) |
1178 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1326 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1179 | } |
1327 | } |
1180 | |
1328 | |
1181 | static void |
1329 | static void |
1182 | t2_cb (EV_P_ ev_timer *w, int revents) |
1330 | t2_cb (EV_P_ ev_timer *w, int revents) |
1183 | { |
1331 | { |
1184 | struct my_biggy big = (struct my_biggy * |
1332 | struct my_biggy big = (struct my_biggy *) |
1185 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1333 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1186 | } |
1334 | } |
1187 | |
1335 | |
1188 | =head2 WATCHER PRIORITY MODELS |
1336 | =head2 WATCHER PRIORITY MODELS |
1189 | |
1337 | |
… | |
… | |
1234 | |
1382 | |
1235 | For example, to emulate how many other event libraries handle priorities, |
1383 | For example, to emulate how many other event libraries handle priorities, |
1236 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1384 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1237 | the normal watcher callback, you just start the idle watcher. The real |
1385 | the normal watcher callback, you just start the idle watcher. The real |
1238 | processing is done in the idle watcher callback. This causes libev to |
1386 | processing is done in the idle watcher callback. This causes libev to |
1239 | continously poll and process kernel event data for the watcher, but when |
1387 | continuously poll and process kernel event data for the watcher, but when |
1240 | the lock-out case is known to be rare (which in turn is rare :), this is |
1388 | the lock-out case is known to be rare (which in turn is rare :), this is |
1241 | workable. |
1389 | workable. |
1242 | |
1390 | |
1243 | Usually, however, the lock-out model implemented that way will perform |
1391 | Usually, however, the lock-out model implemented that way will perform |
1244 | miserably under the type of load it was designed to handle. In that case, |
1392 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1258 | { |
1406 | { |
1259 | // stop the I/O watcher, we received the event, but |
1407 | // stop the I/O watcher, we received the event, but |
1260 | // are not yet ready to handle it. |
1408 | // are not yet ready to handle it. |
1261 | ev_io_stop (EV_A_ w); |
1409 | ev_io_stop (EV_A_ w); |
1262 | |
1410 | |
1263 | // start the idle watcher to ahndle the actual event. |
1411 | // start the idle watcher to handle the actual event. |
1264 | // it will not be executed as long as other watchers |
1412 | // it will not be executed as long as other watchers |
1265 | // with the default priority are receiving events. |
1413 | // with the default priority are receiving events. |
1266 | ev_idle_start (EV_A_ &idle); |
1414 | ev_idle_start (EV_A_ &idle); |
1267 | } |
1415 | } |
1268 | |
1416 | |
1269 | static void |
1417 | static void |
1270 | idle-cb (EV_P_ ev_idle *w, int revents) |
1418 | idle_cb (EV_P_ ev_idle *w, int revents) |
1271 | { |
1419 | { |
1272 | // actual processing |
1420 | // actual processing |
1273 | read (STDIN_FILENO, ...); |
1421 | read (STDIN_FILENO, ...); |
1274 | |
1422 | |
1275 | // have to start the I/O watcher again, as |
1423 | // have to start the I/O watcher again, as |
… | |
… | |
1320 | descriptors to non-blocking mode is also usually a good idea (but not |
1468 | descriptors to non-blocking mode is also usually a good idea (but not |
1321 | required if you know what you are doing). |
1469 | required if you know what you are doing). |
1322 | |
1470 | |
1323 | If you cannot use non-blocking mode, then force the use of a |
1471 | If you cannot use non-blocking mode, then force the use of a |
1324 | known-to-be-good backend (at the time of this writing, this includes only |
1472 | known-to-be-good backend (at the time of this writing, this includes only |
1325 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1473 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1474 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1475 | files) - libev doesn't guarantee any specific behaviour in that case. |
1326 | |
1476 | |
1327 | Another thing you have to watch out for is that it is quite easy to |
1477 | Another thing you have to watch out for is that it is quite easy to |
1328 | receive "spurious" readiness notifications, that is your callback might |
1478 | receive "spurious" readiness notifications, that is your callback might |
1329 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1479 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1330 | because there is no data. Not only are some backends known to create a |
1480 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1395 | |
1545 | |
1396 | So when you encounter spurious, unexplained daemon exits, make sure you |
1546 | So when you encounter spurious, unexplained daemon exits, make sure you |
1397 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1547 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1398 | somewhere, as that would have given you a big clue). |
1548 | somewhere, as that would have given you a big clue). |
1399 | |
1549 | |
|
|
1550 | =head3 The special problem of accept()ing when you can't |
|
|
1551 | |
|
|
1552 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1553 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1554 | connection from the pending queue in all error cases. |
|
|
1555 | |
|
|
1556 | For example, larger servers often run out of file descriptors (because |
|
|
1557 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1558 | rejecting the connection, leading to libev signalling readiness on |
|
|
1559 | the next iteration again (the connection still exists after all), and |
|
|
1560 | typically causing the program to loop at 100% CPU usage. |
|
|
1561 | |
|
|
1562 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1563 | operating systems, there is usually little the app can do to remedy the |
|
|
1564 | situation, and no known thread-safe method of removing the connection to |
|
|
1565 | cope with overload is known (to me). |
|
|
1566 | |
|
|
1567 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1568 | - when the program encounters an overload, it will just loop until the |
|
|
1569 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1570 | event-based way to handle this situation, so it's the best one can do. |
|
|
1571 | |
|
|
1572 | A better way to handle the situation is to log any errors other than |
|
|
1573 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1574 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1575 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1576 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1577 | usage. |
|
|
1578 | |
|
|
1579 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1580 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1581 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1582 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1583 | clients under typical overload conditions. |
|
|
1584 | |
|
|
1585 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1586 | is often done with C<malloc> failures, but this results in an easy |
|
|
1587 | opportunity for a DoS attack. |
1400 | |
1588 | |
1401 | =head3 Watcher-Specific Functions |
1589 | =head3 Watcher-Specific Functions |
1402 | |
1590 | |
1403 | =over 4 |
1591 | =over 4 |
1404 | |
1592 | |
… | |
… | |
1451 | year, it will still time out after (roughly) one hour. "Roughly" because |
1639 | year, it will still time out after (roughly) one hour. "Roughly" because |
1452 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1640 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1453 | monotonic clock option helps a lot here). |
1641 | monotonic clock option helps a lot here). |
1454 | |
1642 | |
1455 | The callback is guaranteed to be invoked only I<after> its timeout has |
1643 | The callback is guaranteed to be invoked only I<after> its timeout has |
1456 | passed. If multiple timers become ready during the same loop iteration |
1644 | passed (not I<at>, so on systems with very low-resolution clocks this |
1457 | then the ones with earlier time-out values are invoked before ones with |
1645 | might introduce a small delay). If multiple timers become ready during the |
1458 | later time-out values (but this is no longer true when a callback calls |
1646 | same loop iteration then the ones with earlier time-out values are invoked |
1459 | C<ev_loop> recursively). |
1647 | before ones of the same priority with later time-out values (but this is |
|
|
1648 | no longer true when a callback calls C<ev_loop> recursively). |
1460 | |
1649 | |
1461 | =head3 Be smart about timeouts |
1650 | =head3 Be smart about timeouts |
1462 | |
1651 | |
1463 | Many real-world problems involve some kind of timeout, usually for error |
1652 | Many real-world problems involve some kind of timeout, usually for error |
1464 | recovery. A typical example is an HTTP request - if the other side hangs, |
1653 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1508 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1697 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1509 | member and C<ev_timer_again>. |
1698 | member and C<ev_timer_again>. |
1510 | |
1699 | |
1511 | At start: |
1700 | At start: |
1512 | |
1701 | |
1513 | ev_timer_init (timer, callback); |
1702 | ev_init (timer, callback); |
1514 | timer->repeat = 60.; |
1703 | timer->repeat = 60.; |
1515 | ev_timer_again (loop, timer); |
1704 | ev_timer_again (loop, timer); |
1516 | |
1705 | |
1517 | Each time there is some activity: |
1706 | Each time there is some activity: |
1518 | |
1707 | |
… | |
… | |
1550 | ev_tstamp timeout = last_activity + 60.; |
1739 | ev_tstamp timeout = last_activity + 60.; |
1551 | |
1740 | |
1552 | // if last_activity + 60. is older than now, we did time out |
1741 | // if last_activity + 60. is older than now, we did time out |
1553 | if (timeout < now) |
1742 | if (timeout < now) |
1554 | { |
1743 | { |
1555 | // timeout occured, take action |
1744 | // timeout occurred, take action |
1556 | } |
1745 | } |
1557 | else |
1746 | else |
1558 | { |
1747 | { |
1559 | // callback was invoked, but there was some activity, re-arm |
1748 | // callback was invoked, but there was some activity, re-arm |
1560 | // the watcher to fire in last_activity + 60, which is |
1749 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1580 | |
1769 | |
1581 | To start the timer, simply initialise the watcher and set C<last_activity> |
1770 | To start the timer, simply initialise the watcher and set C<last_activity> |
1582 | to the current time (meaning we just have some activity :), then call the |
1771 | to the current time (meaning we just have some activity :), then call the |
1583 | callback, which will "do the right thing" and start the timer: |
1772 | callback, which will "do the right thing" and start the timer: |
1584 | |
1773 | |
1585 | ev_timer_init (timer, callback); |
1774 | ev_init (timer, callback); |
1586 | last_activity = ev_now (loop); |
1775 | last_activity = ev_now (loop); |
1587 | callback (loop, timer, EV_TIMEOUT); |
1776 | callback (loop, timer, EV_TIMER); |
1588 | |
1777 | |
1589 | And when there is some activity, simply store the current time in |
1778 | And when there is some activity, simply store the current time in |
1590 | C<last_activity>, no libev calls at all: |
1779 | C<last_activity>, no libev calls at all: |
1591 | |
1780 | |
1592 | last_actiivty = ev_now (loop); |
1781 | last_activity = ev_now (loop); |
1593 | |
1782 | |
1594 | This technique is slightly more complex, but in most cases where the |
1783 | This technique is slightly more complex, but in most cases where the |
1595 | time-out is unlikely to be triggered, much more efficient. |
1784 | time-out is unlikely to be triggered, much more efficient. |
1596 | |
1785 | |
1597 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1786 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
… | |
… | |
1651 | |
1840 | |
1652 | If the event loop is suspended for a long time, you can also force an |
1841 | If the event loop is suspended for a long time, you can also force an |
1653 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1842 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1654 | ()>. |
1843 | ()>. |
1655 | |
1844 | |
|
|
1845 | =head3 The special problems of suspended animation |
|
|
1846 | |
|
|
1847 | When you leave the server world it is quite customary to hit machines that |
|
|
1848 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1849 | |
|
|
1850 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1851 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1852 | to run until the system is suspended, but they will not advance while the |
|
|
1853 | system is suspended. That means, on resume, it will be as if the program |
|
|
1854 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1855 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1856 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1857 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1858 | be adjusted accordingly. |
|
|
1859 | |
|
|
1860 | I would not be surprised to see different behaviour in different between |
|
|
1861 | operating systems, OS versions or even different hardware. |
|
|
1862 | |
|
|
1863 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1864 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1865 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1866 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1867 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1868 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1869 | |
|
|
1870 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1871 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1872 | deterministic behaviour in this case (you can do nothing against |
|
|
1873 | C<SIGSTOP>). |
|
|
1874 | |
1656 | =head3 Watcher-Specific Functions and Data Members |
1875 | =head3 Watcher-Specific Functions and Data Members |
1657 | |
1876 | |
1658 | =over 4 |
1877 | =over 4 |
1659 | |
1878 | |
1660 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1879 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1685 | If the timer is repeating, either start it if necessary (with the |
1904 | If the timer is repeating, either start it if necessary (with the |
1686 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1905 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1687 | |
1906 | |
1688 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1907 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1689 | usage example. |
1908 | usage example. |
|
|
1909 | |
|
|
1910 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
1911 | |
|
|
1912 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1913 | then this time is relative to the current event loop time, otherwise it's |
|
|
1914 | the timeout value currently configured. |
|
|
1915 | |
|
|
1916 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1917 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
1918 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1919 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1920 | too), and so on. |
1690 | |
1921 | |
1691 | =item ev_tstamp repeat [read-write] |
1922 | =item ev_tstamp repeat [read-write] |
1692 | |
1923 | |
1693 | The current C<repeat> value. Will be used each time the watcher times out |
1924 | The current C<repeat> value. Will be used each time the watcher times out |
1694 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1925 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1894 | Example: Call a callback every hour, or, more precisely, whenever the |
2125 | Example: Call a callback every hour, or, more precisely, whenever the |
1895 | system time is divisible by 3600. The callback invocation times have |
2126 | system time is divisible by 3600. The callback invocation times have |
1896 | potentially a lot of jitter, but good long-term stability. |
2127 | potentially a lot of jitter, but good long-term stability. |
1897 | |
2128 | |
1898 | static void |
2129 | static void |
1899 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2130 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1900 | { |
2131 | { |
1901 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2132 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1902 | } |
2133 | } |
1903 | |
2134 | |
1904 | ev_periodic hourly_tick; |
2135 | ev_periodic hourly_tick; |
… | |
… | |
1930 | Signal watchers will trigger an event when the process receives a specific |
2161 | Signal watchers will trigger an event when the process receives a specific |
1931 | signal one or more times. Even though signals are very asynchronous, libev |
2162 | signal one or more times. Even though signals are very asynchronous, libev |
1932 | will try it's best to deliver signals synchronously, i.e. as part of the |
2163 | will try it's best to deliver signals synchronously, i.e. as part of the |
1933 | normal event processing, like any other event. |
2164 | normal event processing, like any other event. |
1934 | |
2165 | |
1935 | If you want signals asynchronously, just use C<sigaction> as you would |
2166 | If you want signals to be delivered truly asynchronously, just use |
1936 | do without libev and forget about sharing the signal. You can even use |
2167 | C<sigaction> as you would do without libev and forget about sharing |
1937 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2168 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2169 | synchronously wake up an event loop. |
1938 | |
2170 | |
1939 | You can configure as many watchers as you like per signal. Only when the |
2171 | You can configure as many watchers as you like for the same signal, but |
|
|
2172 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2173 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2174 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2175 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2176 | |
1940 | first watcher gets started will libev actually register a signal handler |
2177 | When the first watcher gets started will libev actually register something |
1941 | with the kernel (thus it coexists with your own signal handlers as long as |
2178 | with the kernel (thus it coexists with your own signal handlers as long as |
1942 | you don't register any with libev for the same signal). Similarly, when |
2179 | you don't register any with libev for the same signal). |
1943 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1944 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1945 | |
2180 | |
1946 | If possible and supported, libev will install its handlers with |
2181 | If possible and supported, libev will install its handlers with |
1947 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2182 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1948 | interrupted. If you have a problem with system calls getting interrupted by |
2183 | not be unduly interrupted. If you have a problem with system calls getting |
1949 | signals you can block all signals in an C<ev_check> watcher and unblock |
2184 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1950 | them in an C<ev_prepare> watcher. |
2185 | and unblock them in an C<ev_prepare> watcher. |
|
|
2186 | |
|
|
2187 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2188 | |
|
|
2189 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2190 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2191 | stopping it again), that is, libev might or might not block the signal, |
|
|
2192 | and might or might not set or restore the installed signal handler. |
|
|
2193 | |
|
|
2194 | While this does not matter for the signal disposition (libev never |
|
|
2195 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2196 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2197 | certain signals to be blocked. |
|
|
2198 | |
|
|
2199 | This means that before calling C<exec> (from the child) you should reset |
|
|
2200 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2201 | choice usually). |
|
|
2202 | |
|
|
2203 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2204 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2205 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2206 | |
|
|
2207 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2208 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2209 | the window of opportunity for problems, it will not go away, as libev |
|
|
2210 | I<has> to modify the signal mask, at least temporarily. |
|
|
2211 | |
|
|
2212 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2213 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2214 | is not a libev-specific thing, this is true for most event libraries. |
1951 | |
2215 | |
1952 | =head3 Watcher-Specific Functions and Data Members |
2216 | =head3 Watcher-Specific Functions and Data Members |
1953 | |
2217 | |
1954 | =over 4 |
2218 | =over 4 |
1955 | |
2219 | |
… | |
… | |
1987 | some child status changes (most typically when a child of yours dies or |
2251 | some child status changes (most typically when a child of yours dies or |
1988 | exits). It is permissible to install a child watcher I<after> the child |
2252 | exits). It is permissible to install a child watcher I<after> the child |
1989 | has been forked (which implies it might have already exited), as long |
2253 | has been forked (which implies it might have already exited), as long |
1990 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2254 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1991 | forking and then immediately registering a watcher for the child is fine, |
2255 | forking and then immediately registering a watcher for the child is fine, |
1992 | but forking and registering a watcher a few event loop iterations later is |
2256 | but forking and registering a watcher a few event loop iterations later or |
1993 | not. |
2257 | in the next callback invocation is not. |
1994 | |
2258 | |
1995 | Only the default event loop is capable of handling signals, and therefore |
2259 | Only the default event loop is capable of handling signals, and therefore |
1996 | you can only register child watchers in the default event loop. |
2260 | you can only register child watchers in the default event loop. |
1997 | |
2261 | |
|
|
2262 | Due to some design glitches inside libev, child watchers will always be |
|
|
2263 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2264 | libev) |
|
|
2265 | |
1998 | =head3 Process Interaction |
2266 | =head3 Process Interaction |
1999 | |
2267 | |
2000 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2268 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2001 | initialised. This is necessary to guarantee proper behaviour even if |
2269 | initialised. This is necessary to guarantee proper behaviour even if the |
2002 | the first child watcher is started after the child exits. The occurrence |
2270 | first child watcher is started after the child exits. The occurrence |
2003 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2271 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2004 | synchronously as part of the event loop processing. Libev always reaps all |
2272 | synchronously as part of the event loop processing. Libev always reaps all |
2005 | children, even ones not watched. |
2273 | children, even ones not watched. |
2006 | |
2274 | |
2007 | =head3 Overriding the Built-In Processing |
2275 | =head3 Overriding the Built-In Processing |
… | |
… | |
2017 | =head3 Stopping the Child Watcher |
2285 | =head3 Stopping the Child Watcher |
2018 | |
2286 | |
2019 | Currently, the child watcher never gets stopped, even when the |
2287 | Currently, the child watcher never gets stopped, even when the |
2020 | child terminates, so normally one needs to stop the watcher in the |
2288 | child terminates, so normally one needs to stop the watcher in the |
2021 | callback. Future versions of libev might stop the watcher automatically |
2289 | callback. Future versions of libev might stop the watcher automatically |
2022 | when a child exit is detected. |
2290 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2291 | problem). |
2023 | |
2292 | |
2024 | =head3 Watcher-Specific Functions and Data Members |
2293 | =head3 Watcher-Specific Functions and Data Members |
2025 | |
2294 | |
2026 | =over 4 |
2295 | =over 4 |
2027 | |
2296 | |
… | |
… | |
2353 | // no longer anything immediate to do. |
2622 | // no longer anything immediate to do. |
2354 | } |
2623 | } |
2355 | |
2624 | |
2356 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2625 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2357 | ev_idle_init (idle_watcher, idle_cb); |
2626 | ev_idle_init (idle_watcher, idle_cb); |
2358 | ev_idle_start (loop, idle_cb); |
2627 | ev_idle_start (loop, idle_watcher); |
2359 | |
2628 | |
2360 | |
2629 | |
2361 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2630 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2362 | |
2631 | |
2363 | Prepare and check watchers are usually (but not always) used in pairs: |
2632 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2456 | struct pollfd fds [nfd]; |
2725 | struct pollfd fds [nfd]; |
2457 | // actual code will need to loop here and realloc etc. |
2726 | // actual code will need to loop here and realloc etc. |
2458 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2727 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2459 | |
2728 | |
2460 | /* the callback is illegal, but won't be called as we stop during check */ |
2729 | /* the callback is illegal, but won't be called as we stop during check */ |
2461 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2730 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2462 | ev_timer_start (loop, &tw); |
2731 | ev_timer_start (loop, &tw); |
2463 | |
2732 | |
2464 | // create one ev_io per pollfd |
2733 | // create one ev_io per pollfd |
2465 | for (int i = 0; i < nfd; ++i) |
2734 | for (int i = 0; i < nfd; ++i) |
2466 | { |
2735 | { |
… | |
… | |
2696 | event loop blocks next and before C<ev_check> watchers are being called, |
2965 | event loop blocks next and before C<ev_check> watchers are being called, |
2697 | and only in the child after the fork. If whoever good citizen calling |
2966 | and only in the child after the fork. If whoever good citizen calling |
2698 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2967 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2699 | handlers will be invoked, too, of course. |
2968 | handlers will be invoked, too, of course. |
2700 | |
2969 | |
|
|
2970 | =head3 The special problem of life after fork - how is it possible? |
|
|
2971 | |
|
|
2972 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
2973 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2974 | sequence should be handled by libev without any problems. |
|
|
2975 | |
|
|
2976 | This changes when the application actually wants to do event handling |
|
|
2977 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2978 | fork. |
|
|
2979 | |
|
|
2980 | The default mode of operation (for libev, with application help to detect |
|
|
2981 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2982 | when I<either> the parent I<or> the child process continues. |
|
|
2983 | |
|
|
2984 | When both processes want to continue using libev, then this is usually the |
|
|
2985 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2986 | supposed to continue with all watchers in place as before, while the other |
|
|
2987 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2988 | |
|
|
2989 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2990 | simply create a new event loop, which of course will be "empty", and |
|
|
2991 | use that for new watchers. This has the advantage of not touching more |
|
|
2992 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2993 | disadvantage of having to use multiple event loops (which do not support |
|
|
2994 | signal watchers). |
|
|
2995 | |
|
|
2996 | When this is not possible, or you want to use the default loop for |
|
|
2997 | other reasons, then in the process that wants to start "fresh", call |
|
|
2998 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2999 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
3000 | have to be careful not to execute code that modifies those watchers. Note |
|
|
3001 | also that in that case, you have to re-register any signal watchers. |
|
|
3002 | |
2701 | =head3 Watcher-Specific Functions and Data Members |
3003 | =head3 Watcher-Specific Functions and Data Members |
2702 | |
3004 | |
2703 | =over 4 |
3005 | =over 4 |
2704 | |
3006 | |
2705 | =item ev_fork_init (ev_signal *, callback) |
3007 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2709 | believe me. |
3011 | believe me. |
2710 | |
3012 | |
2711 | =back |
3013 | =back |
2712 | |
3014 | |
2713 | |
3015 | |
2714 | =head2 C<ev_async> - how to wake up another event loop |
3016 | =head2 C<ev_async> - how to wake up an event loop |
2715 | |
3017 | |
2716 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3018 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2717 | asynchronous sources such as signal handlers (as opposed to multiple event |
3019 | asynchronous sources such as signal handlers (as opposed to multiple event |
2718 | loops - those are of course safe to use in different threads). |
3020 | loops - those are of course safe to use in different threads). |
2719 | |
3021 | |
2720 | Sometimes, however, you need to wake up another event loop you do not |
3022 | Sometimes, however, you need to wake up an event loop you do not control, |
2721 | control, for example because it belongs to another thread. This is what |
3023 | for example because it belongs to another thread. This is what C<ev_async> |
2722 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3024 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2723 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3025 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2724 | safe. |
|
|
2725 | |
3026 | |
2726 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3027 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2727 | too, are asynchronous in nature, and signals, too, will be compressed |
3028 | too, are asynchronous in nature, and signals, too, will be compressed |
2728 | (i.e. the number of callback invocations may be less than the number of |
3029 | (i.e. the number of callback invocations may be less than the number of |
2729 | C<ev_async_sent> calls). |
3030 | C<ev_async_sent> calls). |
… | |
… | |
2734 | =head3 Queueing |
3035 | =head3 Queueing |
2735 | |
3036 | |
2736 | C<ev_async> does not support queueing of data in any way. The reason |
3037 | C<ev_async> does not support queueing of data in any way. The reason |
2737 | is that the author does not know of a simple (or any) algorithm for a |
3038 | is that the author does not know of a simple (or any) algorithm for a |
2738 | multiple-writer-single-reader queue that works in all cases and doesn't |
3039 | multiple-writer-single-reader queue that works in all cases and doesn't |
2739 | need elaborate support such as pthreads. |
3040 | need elaborate support such as pthreads or unportable memory access |
|
|
3041 | semantics. |
2740 | |
3042 | |
2741 | That means that if you want to queue data, you have to provide your own |
3043 | That means that if you want to queue data, you have to provide your own |
2742 | queue. But at least I can tell you how to implement locking around your |
3044 | queue. But at least I can tell you how to implement locking around your |
2743 | queue: |
3045 | queue: |
2744 | |
3046 | |
… | |
… | |
2883 | |
3185 | |
2884 | If C<timeout> is less than 0, then no timeout watcher will be |
3186 | If C<timeout> is less than 0, then no timeout watcher will be |
2885 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3187 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2886 | repeat = 0) will be started. C<0> is a valid timeout. |
3188 | repeat = 0) will be started. C<0> is a valid timeout. |
2887 | |
3189 | |
2888 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3190 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2889 | passed an C<revents> set like normal event callbacks (a combination of |
3191 | passed an C<revents> set like normal event callbacks (a combination of |
2890 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3192 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2891 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3193 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2892 | a timeout and an io event at the same time - you probably should give io |
3194 | a timeout and an io event at the same time - you probably should give io |
2893 | events precedence. |
3195 | events precedence. |
2894 | |
3196 | |
2895 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3197 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2896 | |
3198 | |
2897 | static void stdin_ready (int revents, void *arg) |
3199 | static void stdin_ready (int revents, void *arg) |
2898 | { |
3200 | { |
2899 | if (revents & EV_READ) |
3201 | if (revents & EV_READ) |
2900 | /* stdin might have data for us, joy! */; |
3202 | /* stdin might have data for us, joy! */; |
2901 | else if (revents & EV_TIMEOUT) |
3203 | else if (revents & EV_TIMER) |
2902 | /* doh, nothing entered */; |
3204 | /* doh, nothing entered */; |
2903 | } |
3205 | } |
2904 | |
3206 | |
2905 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3207 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2906 | |
3208 | |
2907 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2908 | |
|
|
2909 | Feeds the given event set into the event loop, as if the specified event |
|
|
2910 | had happened for the specified watcher (which must be a pointer to an |
|
|
2911 | initialised but not necessarily started event watcher). |
|
|
2912 | |
|
|
2913 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3209 | =item ev_feed_fd_event (loop, int fd, int revents) |
2914 | |
3210 | |
2915 | Feed an event on the given fd, as if a file descriptor backend detected |
3211 | Feed an event on the given fd, as if a file descriptor backend detected |
2916 | the given events it. |
3212 | the given events it. |
2917 | |
3213 | |
2918 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3214 | =item ev_feed_signal_event (loop, int signum) |
2919 | |
3215 | |
2920 | Feed an event as if the given signal occurred (C<loop> must be the default |
3216 | Feed an event as if the given signal occurred (C<loop> must be the default |
2921 | loop!). |
3217 | loop!). |
2922 | |
3218 | |
2923 | =back |
3219 | =back |
… | |
… | |
3003 | |
3299 | |
3004 | =over 4 |
3300 | =over 4 |
3005 | |
3301 | |
3006 | =item ev::TYPE::TYPE () |
3302 | =item ev::TYPE::TYPE () |
3007 | |
3303 | |
3008 | =item ev::TYPE::TYPE (struct ev_loop *) |
3304 | =item ev::TYPE::TYPE (loop) |
3009 | |
3305 | |
3010 | =item ev::TYPE::~TYPE |
3306 | =item ev::TYPE::~TYPE |
3011 | |
3307 | |
3012 | The constructor (optionally) takes an event loop to associate the watcher |
3308 | The constructor (optionally) takes an event loop to associate the watcher |
3013 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3309 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
3046 | myclass obj; |
3342 | myclass obj; |
3047 | ev::io iow; |
3343 | ev::io iow; |
3048 | iow.set <myclass, &myclass::io_cb> (&obj); |
3344 | iow.set <myclass, &myclass::io_cb> (&obj); |
3049 | |
3345 | |
3050 | =item w->set (object *) |
3346 | =item w->set (object *) |
3051 | |
|
|
3052 | This is an B<experimental> feature that might go away in a future version. |
|
|
3053 | |
3347 | |
3054 | This is a variation of a method callback - leaving out the method to call |
3348 | This is a variation of a method callback - leaving out the method to call |
3055 | will default the method to C<operator ()>, which makes it possible to use |
3349 | will default the method to C<operator ()>, which makes it possible to use |
3056 | functor objects without having to manually specify the C<operator ()> all |
3350 | functor objects without having to manually specify the C<operator ()> all |
3057 | the time. Incidentally, you can then also leave out the template argument |
3351 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3090 | Example: Use a plain function as callback. |
3384 | Example: Use a plain function as callback. |
3091 | |
3385 | |
3092 | static void io_cb (ev::io &w, int revents) { } |
3386 | static void io_cb (ev::io &w, int revents) { } |
3093 | iow.set <io_cb> (); |
3387 | iow.set <io_cb> (); |
3094 | |
3388 | |
3095 | =item w->set (struct ev_loop *) |
3389 | =item w->set (loop) |
3096 | |
3390 | |
3097 | Associates a different C<struct ev_loop> with this watcher. You can only |
3391 | Associates a different C<struct ev_loop> with this watcher. You can only |
3098 | do this when the watcher is inactive (and not pending either). |
3392 | do this when the watcher is inactive (and not pending either). |
3099 | |
3393 | |
3100 | =item w->set ([arguments]) |
3394 | =item w->set ([arguments]) |
3101 | |
3395 | |
3102 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3396 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
3103 | called at least once. Unlike the C counterpart, an active watcher gets |
3397 | method or a suitable start method must be called at least once. Unlike the |
3104 | automatically stopped and restarted when reconfiguring it with this |
3398 | C counterpart, an active watcher gets automatically stopped and restarted |
3105 | method. |
3399 | when reconfiguring it with this method. |
3106 | |
3400 | |
3107 | =item w->start () |
3401 | =item w->start () |
3108 | |
3402 | |
3109 | Starts the watcher. Note that there is no C<loop> argument, as the |
3403 | Starts the watcher. Note that there is no C<loop> argument, as the |
3110 | constructor already stores the event loop. |
3404 | constructor already stores the event loop. |
3111 | |
3405 | |
|
|
3406 | =item w->start ([arguments]) |
|
|
3407 | |
|
|
3408 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3409 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3410 | the configure C<set> method of the watcher. |
|
|
3411 | |
3112 | =item w->stop () |
3412 | =item w->stop () |
3113 | |
3413 | |
3114 | Stops the watcher if it is active. Again, no C<loop> argument. |
3414 | Stops the watcher if it is active. Again, no C<loop> argument. |
3115 | |
3415 | |
3116 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3416 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
3128 | |
3428 | |
3129 | =back |
3429 | =back |
3130 | |
3430 | |
3131 | =back |
3431 | =back |
3132 | |
3432 | |
3133 | Example: Define a class with an IO and idle watcher, start one of them in |
3433 | Example: Define a class with two I/O and idle watchers, start the I/O |
3134 | the constructor. |
3434 | watchers in the constructor. |
3135 | |
3435 | |
3136 | class myclass |
3436 | class myclass |
3137 | { |
3437 | { |
3138 | ev::io io ; void io_cb (ev::io &w, int revents); |
3438 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3439 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
3139 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3440 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3140 | |
3441 | |
3141 | myclass (int fd) |
3442 | myclass (int fd) |
3142 | { |
3443 | { |
3143 | io .set <myclass, &myclass::io_cb > (this); |
3444 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3445 | io2 .set <myclass, &myclass::io2_cb > (this); |
3144 | idle.set <myclass, &myclass::idle_cb> (this); |
3446 | idle.set <myclass, &myclass::idle_cb> (this); |
3145 | |
3447 | |
3146 | io.start (fd, ev::READ); |
3448 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3449 | io.start (); // start it whenever convenient |
|
|
3450 | |
|
|
3451 | io2.start (fd, ev::READ); // set + start in one call |
3147 | } |
3452 | } |
3148 | }; |
3453 | }; |
3149 | |
3454 | |
3150 | |
3455 | |
3151 | =head1 OTHER LANGUAGE BINDINGS |
3456 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
3197 | =item Ocaml |
3502 | =item Ocaml |
3198 | |
3503 | |
3199 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3504 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3200 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3505 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3201 | |
3506 | |
|
|
3507 | =item Lua |
|
|
3508 | |
|
|
3509 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3510 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3511 | L<http://github.com/brimworks/lua-ev>. |
|
|
3512 | |
3202 | =back |
3513 | =back |
3203 | |
3514 | |
3204 | |
3515 | |
3205 | =head1 MACRO MAGIC |
3516 | =head1 MACRO MAGIC |
3206 | |
3517 | |
… | |
… | |
3359 | libev.m4 |
3670 | libev.m4 |
3360 | |
3671 | |
3361 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3672 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3362 | |
3673 | |
3363 | Libev can be configured via a variety of preprocessor symbols you have to |
3674 | Libev can be configured via a variety of preprocessor symbols you have to |
3364 | define before including any of its files. The default in the absence of |
3675 | define before including (or compiling) any of its files. The default in |
3365 | autoconf is documented for every option. |
3676 | the absence of autoconf is documented for every option. |
|
|
3677 | |
|
|
3678 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3679 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3680 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3681 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3682 | users of libev and the libev code itself must be compiled with compatible |
|
|
3683 | settings. |
3366 | |
3684 | |
3367 | =over 4 |
3685 | =over 4 |
3368 | |
3686 | |
3369 | =item EV_STANDALONE |
3687 | =item EV_STANDALONE (h) |
3370 | |
3688 | |
3371 | Must always be C<1> if you do not use autoconf configuration, which |
3689 | Must always be C<1> if you do not use autoconf configuration, which |
3372 | keeps libev from including F<config.h>, and it also defines dummy |
3690 | keeps libev from including F<config.h>, and it also defines dummy |
3373 | implementations for some libevent functions (such as logging, which is not |
3691 | implementations for some libevent functions (such as logging, which is not |
3374 | supported). It will also not define any of the structs usually found in |
3692 | supported). It will also not define any of the structs usually found in |
3375 | F<event.h> that are not directly supported by the libev core alone. |
3693 | F<event.h> that are not directly supported by the libev core alone. |
3376 | |
3694 | |
3377 | In stanbdalone mode, libev will still try to automatically deduce the |
3695 | In standalone mode, libev will still try to automatically deduce the |
3378 | configuration, but has to be more conservative. |
3696 | configuration, but has to be more conservative. |
3379 | |
3697 | |
3380 | =item EV_USE_MONOTONIC |
3698 | =item EV_USE_MONOTONIC |
3381 | |
3699 | |
3382 | If defined to be C<1>, libev will try to detect the availability of the |
3700 | If defined to be C<1>, libev will try to detect the availability of the |
… | |
… | |
3447 | be used is the winsock select). This means that it will call |
3765 | be used is the winsock select). This means that it will call |
3448 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3766 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3449 | it is assumed that all these functions actually work on fds, even |
3767 | it is assumed that all these functions actually work on fds, even |
3450 | on win32. Should not be defined on non-win32 platforms. |
3768 | on win32. Should not be defined on non-win32 platforms. |
3451 | |
3769 | |
3452 | =item EV_FD_TO_WIN32_HANDLE |
3770 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3453 | |
3771 | |
3454 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3772 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3455 | file descriptors to socket handles. When not defining this symbol (the |
3773 | file descriptors to socket handles. When not defining this symbol (the |
3456 | default), then libev will call C<_get_osfhandle>, which is usually |
3774 | default), then libev will call C<_get_osfhandle>, which is usually |
3457 | correct. In some cases, programs use their own file descriptor management, |
3775 | correct. In some cases, programs use their own file descriptor management, |
3458 | in which case they can provide this function to map fds to socket handles. |
3776 | in which case they can provide this function to map fds to socket handles. |
|
|
3777 | |
|
|
3778 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3779 | |
|
|
3780 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3781 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3782 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3783 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3784 | |
|
|
3785 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3786 | |
|
|
3787 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3788 | macro can be used to override the C<close> function, useful to unregister |
|
|
3789 | file descriptors again. Note that the replacement function has to close |
|
|
3790 | the underlying OS handle. |
3459 | |
3791 | |
3460 | =item EV_USE_POLL |
3792 | =item EV_USE_POLL |
3461 | |
3793 | |
3462 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3794 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3463 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3795 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3510 | as well as for signal and thread safety in C<ev_async> watchers. |
3842 | as well as for signal and thread safety in C<ev_async> watchers. |
3511 | |
3843 | |
3512 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3844 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3513 | (from F<signal.h>), which is usually good enough on most platforms. |
3845 | (from F<signal.h>), which is usually good enough on most platforms. |
3514 | |
3846 | |
3515 | =item EV_H |
3847 | =item EV_H (h) |
3516 | |
3848 | |
3517 | The name of the F<ev.h> header file used to include it. The default if |
3849 | The name of the F<ev.h> header file used to include it. The default if |
3518 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3850 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3519 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3851 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3520 | |
3852 | |
3521 | =item EV_CONFIG_H |
3853 | =item EV_CONFIG_H (h) |
3522 | |
3854 | |
3523 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3855 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3524 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3856 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3525 | C<EV_H>, above. |
3857 | C<EV_H>, above. |
3526 | |
3858 | |
3527 | =item EV_EVENT_H |
3859 | =item EV_EVENT_H (h) |
3528 | |
3860 | |
3529 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3861 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3530 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3862 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3531 | |
3863 | |
3532 | =item EV_PROTOTYPES |
3864 | =item EV_PROTOTYPES (h) |
3533 | |
3865 | |
3534 | If defined to be C<0>, then F<ev.h> will not define any function |
3866 | If defined to be C<0>, then F<ev.h> will not define any function |
3535 | prototypes, but still define all the structs and other symbols. This is |
3867 | prototypes, but still define all the structs and other symbols. This is |
3536 | occasionally useful if you want to provide your own wrapper functions |
3868 | occasionally useful if you want to provide your own wrapper functions |
3537 | around libev functions. |
3869 | around libev functions. |
… | |
… | |
3559 | fine. |
3891 | fine. |
3560 | |
3892 | |
3561 | If your embedding application does not need any priorities, defining these |
3893 | If your embedding application does not need any priorities, defining these |
3562 | both to C<0> will save some memory and CPU. |
3894 | both to C<0> will save some memory and CPU. |
3563 | |
3895 | |
3564 | =item EV_PERIODIC_ENABLE |
3896 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3897 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3898 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3565 | |
3899 | |
3566 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3900 | If undefined or defined to be C<1> (and the platform supports it), then |
3567 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3901 | the respective watcher type is supported. If defined to be C<0>, then it |
3568 | code. |
3902 | is not. Disabling watcher types mainly saves code size. |
3569 | |
3903 | |
3570 | =item EV_IDLE_ENABLE |
3904 | =item EV_FEATURES |
3571 | |
|
|
3572 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3573 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3574 | code. |
|
|
3575 | |
|
|
3576 | =item EV_EMBED_ENABLE |
|
|
3577 | |
|
|
3578 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3579 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3580 | watcher types, which therefore must not be disabled. |
|
|
3581 | |
|
|
3582 | =item EV_STAT_ENABLE |
|
|
3583 | |
|
|
3584 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3585 | defined to be C<0>, then they are not. |
|
|
3586 | |
|
|
3587 | =item EV_FORK_ENABLE |
|
|
3588 | |
|
|
3589 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3590 | defined to be C<0>, then they are not. |
|
|
3591 | |
|
|
3592 | =item EV_ASYNC_ENABLE |
|
|
3593 | |
|
|
3594 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3595 | defined to be C<0>, then they are not. |
|
|
3596 | |
|
|
3597 | =item EV_MINIMAL |
|
|
3598 | |
3905 | |
3599 | If you need to shave off some kilobytes of code at the expense of some |
3906 | If you need to shave off some kilobytes of code at the expense of some |
3600 | speed, define this symbol to C<1>. Currently this is used to override some |
3907 | speed (but with the full API), you can define this symbol to request |
3601 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3908 | certain subsets of functionality. The default is to enable all features |
3602 | much smaller 2-heap for timer management over the default 4-heap. |
3909 | that can be enabled on the platform. |
|
|
3910 | |
|
|
3911 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
3912 | with some broad features you want) and then selectively re-enable |
|
|
3913 | additional parts you want, for example if you want everything minimal, |
|
|
3914 | but multiple event loop support, async and child watchers and the poll |
|
|
3915 | backend, use this: |
|
|
3916 | |
|
|
3917 | #define EV_FEATURES 0 |
|
|
3918 | #define EV_MULTIPLICITY 1 |
|
|
3919 | #define EV_USE_POLL 1 |
|
|
3920 | #define EV_CHILD_ENABLE 1 |
|
|
3921 | #define EV_ASYNC_ENABLE 1 |
|
|
3922 | |
|
|
3923 | The actual value is a bitset, it can be a combination of the following |
|
|
3924 | values: |
|
|
3925 | |
|
|
3926 | =over 4 |
|
|
3927 | |
|
|
3928 | =item C<1> - faster/larger code |
|
|
3929 | |
|
|
3930 | Use larger code to speed up some operations. |
|
|
3931 | |
|
|
3932 | Currently this is used to override some inlining decisions (enlarging the |
|
|
3933 | code size by roughly 30% on amd64). |
|
|
3934 | |
|
|
3935 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3936 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3937 | assertions. |
|
|
3938 | |
|
|
3939 | =item C<2> - faster/larger data structures |
|
|
3940 | |
|
|
3941 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3942 | hash table sizes and so on. This will usually further increase code size |
|
|
3943 | and can additionally have an effect on the size of data structures at |
|
|
3944 | runtime. |
|
|
3945 | |
|
|
3946 | =item C<4> - full API configuration |
|
|
3947 | |
|
|
3948 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3949 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3950 | |
|
|
3951 | =item C<8> - full API |
|
|
3952 | |
|
|
3953 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
3954 | details on which parts of the API are still available without this |
|
|
3955 | feature, and do not complain if this subset changes over time. |
|
|
3956 | |
|
|
3957 | =item C<16> - enable all optional watcher types |
|
|
3958 | |
|
|
3959 | Enables all optional watcher types. If you want to selectively enable |
|
|
3960 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3961 | embed, async, child...) you can enable them manually by defining |
|
|
3962 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3963 | |
|
|
3964 | =item C<32> - enable all backends |
|
|
3965 | |
|
|
3966 | This enables all backends - without this feature, you need to enable at |
|
|
3967 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3968 | |
|
|
3969 | =item C<64> - enable OS-specific "helper" APIs |
|
|
3970 | |
|
|
3971 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3972 | default. |
|
|
3973 | |
|
|
3974 | =back |
|
|
3975 | |
|
|
3976 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3977 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
3978 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
3979 | watchers, timers and monotonic clock support. |
|
|
3980 | |
|
|
3981 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3982 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3983 | your program might be left out as well - a binary starting a timer and an |
|
|
3984 | I/O watcher then might come out at only 5Kb. |
|
|
3985 | |
|
|
3986 | =item EV_AVOID_STDIO |
|
|
3987 | |
|
|
3988 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3989 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
3990 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3991 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3992 | big. |
|
|
3993 | |
|
|
3994 | Note that error messages might become less precise when this option is |
|
|
3995 | enabled. |
|
|
3996 | |
|
|
3997 | =item EV_NSIG |
|
|
3998 | |
|
|
3999 | The highest supported signal number, +1 (or, the number of |
|
|
4000 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4001 | automatically, but sometimes this fails, in which case it can be |
|
|
4002 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4003 | good for about any system in existence) can save some memory, as libev |
|
|
4004 | statically allocates some 12-24 bytes per signal number. |
3603 | |
4005 | |
3604 | =item EV_PID_HASHSIZE |
4006 | =item EV_PID_HASHSIZE |
3605 | |
4007 | |
3606 | C<ev_child> watchers use a small hash table to distribute workload by |
4008 | C<ev_child> watchers use a small hash table to distribute workload by |
3607 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4009 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3608 | than enough. If you need to manage thousands of children you might want to |
4010 | usually more than enough. If you need to manage thousands of children you |
3609 | increase this value (I<must> be a power of two). |
4011 | might want to increase this value (I<must> be a power of two). |
3610 | |
4012 | |
3611 | =item EV_INOTIFY_HASHSIZE |
4013 | =item EV_INOTIFY_HASHSIZE |
3612 | |
4014 | |
3613 | C<ev_stat> watchers use a small hash table to distribute workload by |
4015 | C<ev_stat> watchers use a small hash table to distribute workload by |
3614 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4016 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3615 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4017 | disabled), usually more than enough. If you need to manage thousands of |
3616 | watchers you might want to increase this value (I<must> be a power of |
4018 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3617 | two). |
4019 | power of two). |
3618 | |
4020 | |
3619 | =item EV_USE_4HEAP |
4021 | =item EV_USE_4HEAP |
3620 | |
4022 | |
3621 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4023 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3622 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4024 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3623 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4025 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3624 | faster performance with many (thousands) of watchers. |
4026 | faster performance with many (thousands) of watchers. |
3625 | |
4027 | |
3626 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4028 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3627 | (disabled). |
4029 | will be C<0>. |
3628 | |
4030 | |
3629 | =item EV_HEAP_CACHE_AT |
4031 | =item EV_HEAP_CACHE_AT |
3630 | |
4032 | |
3631 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4033 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3632 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4034 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3633 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4035 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3634 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4036 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3635 | but avoids random read accesses on heap changes. This improves performance |
4037 | but avoids random read accesses on heap changes. This improves performance |
3636 | noticeably with many (hundreds) of watchers. |
4038 | noticeably with many (hundreds) of watchers. |
3637 | |
4039 | |
3638 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4040 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3639 | (disabled). |
4041 | will be C<0>. |
3640 | |
4042 | |
3641 | =item EV_VERIFY |
4043 | =item EV_VERIFY |
3642 | |
4044 | |
3643 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4045 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
3644 | be done: If set to C<0>, no internal verification code will be compiled |
4046 | be done: If set to C<0>, no internal verification code will be compiled |
… | |
… | |
3646 | called. If set to C<2>, then the internal verification code will be |
4048 | called. If set to C<2>, then the internal verification code will be |
3647 | called once per loop, which can slow down libev. If set to C<3>, then the |
4049 | called once per loop, which can slow down libev. If set to C<3>, then the |
3648 | verification code will be called very frequently, which will slow down |
4050 | verification code will be called very frequently, which will slow down |
3649 | libev considerably. |
4051 | libev considerably. |
3650 | |
4052 | |
3651 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4053 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3652 | C<0>. |
4054 | will be C<0>. |
3653 | |
4055 | |
3654 | =item EV_COMMON |
4056 | =item EV_COMMON |
3655 | |
4057 | |
3656 | By default, all watchers have a C<void *data> member. By redefining |
4058 | By default, all watchers have a C<void *data> member. By redefining |
3657 | this macro to a something else you can include more and other types of |
4059 | this macro to something else you can include more and other types of |
3658 | members. You have to define it each time you include one of the files, |
4060 | members. You have to define it each time you include one of the files, |
3659 | though, and it must be identical each time. |
4061 | though, and it must be identical each time. |
3660 | |
4062 | |
3661 | For example, the perl EV module uses something like this: |
4063 | For example, the perl EV module uses something like this: |
3662 | |
4064 | |
… | |
… | |
3715 | file. |
4117 | file. |
3716 | |
4118 | |
3717 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4119 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3718 | that everybody includes and which overrides some configure choices: |
4120 | that everybody includes and which overrides some configure choices: |
3719 | |
4121 | |
3720 | #define EV_MINIMAL 1 |
4122 | #define EV_FEATURES 8 |
3721 | #define EV_USE_POLL 0 |
4123 | #define EV_USE_SELECT 1 |
3722 | #define EV_MULTIPLICITY 0 |
|
|
3723 | #define EV_PERIODIC_ENABLE 0 |
4124 | #define EV_PREPARE_ENABLE 1 |
|
|
4125 | #define EV_IDLE_ENABLE 1 |
3724 | #define EV_STAT_ENABLE 0 |
4126 | #define EV_SIGNAL_ENABLE 1 |
3725 | #define EV_FORK_ENABLE 0 |
4127 | #define EV_CHILD_ENABLE 1 |
|
|
4128 | #define EV_USE_STDEXCEPT 0 |
3726 | #define EV_CONFIG_H <config.h> |
4129 | #define EV_CONFIG_H <config.h> |
3727 | #define EV_MINPRI 0 |
|
|
3728 | #define EV_MAXPRI 0 |
|
|
3729 | |
4130 | |
3730 | #include "ev++.h" |
4131 | #include "ev++.h" |
3731 | |
4132 | |
3732 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4133 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3733 | |
4134 | |
… | |
… | |
3793 | default loop and triggering an C<ev_async> watcher from the default loop |
4194 | default loop and triggering an C<ev_async> watcher from the default loop |
3794 | watcher callback into the event loop interested in the signal. |
4195 | watcher callback into the event loop interested in the signal. |
3795 | |
4196 | |
3796 | =back |
4197 | =back |
3797 | |
4198 | |
|
|
4199 | =head4 THREAD LOCKING EXAMPLE |
|
|
4200 | |
|
|
4201 | Here is a fictitious example of how to run an event loop in a different |
|
|
4202 | thread than where callbacks are being invoked and watchers are |
|
|
4203 | created/added/removed. |
|
|
4204 | |
|
|
4205 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4206 | which uses exactly this technique (which is suited for many high-level |
|
|
4207 | languages). |
|
|
4208 | |
|
|
4209 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4210 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4211 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4212 | |
|
|
4213 | First, you need to associate some data with the event loop: |
|
|
4214 | |
|
|
4215 | typedef struct { |
|
|
4216 | mutex_t lock; /* global loop lock */ |
|
|
4217 | ev_async async_w; |
|
|
4218 | thread_t tid; |
|
|
4219 | cond_t invoke_cv; |
|
|
4220 | } userdata; |
|
|
4221 | |
|
|
4222 | void prepare_loop (EV_P) |
|
|
4223 | { |
|
|
4224 | // for simplicity, we use a static userdata struct. |
|
|
4225 | static userdata u; |
|
|
4226 | |
|
|
4227 | ev_async_init (&u->async_w, async_cb); |
|
|
4228 | ev_async_start (EV_A_ &u->async_w); |
|
|
4229 | |
|
|
4230 | pthread_mutex_init (&u->lock, 0); |
|
|
4231 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4232 | |
|
|
4233 | // now associate this with the loop |
|
|
4234 | ev_set_userdata (EV_A_ u); |
|
|
4235 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4236 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4237 | |
|
|
4238 | // then create the thread running ev_loop |
|
|
4239 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4240 | } |
|
|
4241 | |
|
|
4242 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4243 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4244 | that might have been added: |
|
|
4245 | |
|
|
4246 | static void |
|
|
4247 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4248 | { |
|
|
4249 | // just used for the side effects |
|
|
4250 | } |
|
|
4251 | |
|
|
4252 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4253 | protecting the loop data, respectively. |
|
|
4254 | |
|
|
4255 | static void |
|
|
4256 | l_release (EV_P) |
|
|
4257 | { |
|
|
4258 | userdata *u = ev_userdata (EV_A); |
|
|
4259 | pthread_mutex_unlock (&u->lock); |
|
|
4260 | } |
|
|
4261 | |
|
|
4262 | static void |
|
|
4263 | l_acquire (EV_P) |
|
|
4264 | { |
|
|
4265 | userdata *u = ev_userdata (EV_A); |
|
|
4266 | pthread_mutex_lock (&u->lock); |
|
|
4267 | } |
|
|
4268 | |
|
|
4269 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4270 | into C<ev_loop>: |
|
|
4271 | |
|
|
4272 | void * |
|
|
4273 | l_run (void *thr_arg) |
|
|
4274 | { |
|
|
4275 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4276 | |
|
|
4277 | l_acquire (EV_A); |
|
|
4278 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4279 | ev_loop (EV_A_ 0); |
|
|
4280 | l_release (EV_A); |
|
|
4281 | |
|
|
4282 | return 0; |
|
|
4283 | } |
|
|
4284 | |
|
|
4285 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4286 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4287 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4288 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4289 | and b) skipping inter-thread-communication when there are no pending |
|
|
4290 | watchers is very beneficial): |
|
|
4291 | |
|
|
4292 | static void |
|
|
4293 | l_invoke (EV_P) |
|
|
4294 | { |
|
|
4295 | userdata *u = ev_userdata (EV_A); |
|
|
4296 | |
|
|
4297 | while (ev_pending_count (EV_A)) |
|
|
4298 | { |
|
|
4299 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4300 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4301 | } |
|
|
4302 | } |
|
|
4303 | |
|
|
4304 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4305 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4306 | thread to continue: |
|
|
4307 | |
|
|
4308 | static void |
|
|
4309 | real_invoke_pending (EV_P) |
|
|
4310 | { |
|
|
4311 | userdata *u = ev_userdata (EV_A); |
|
|
4312 | |
|
|
4313 | pthread_mutex_lock (&u->lock); |
|
|
4314 | ev_invoke_pending (EV_A); |
|
|
4315 | pthread_cond_signal (&u->invoke_cv); |
|
|
4316 | pthread_mutex_unlock (&u->lock); |
|
|
4317 | } |
|
|
4318 | |
|
|
4319 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4320 | event loop, you will now have to lock: |
|
|
4321 | |
|
|
4322 | ev_timer timeout_watcher; |
|
|
4323 | userdata *u = ev_userdata (EV_A); |
|
|
4324 | |
|
|
4325 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4326 | |
|
|
4327 | pthread_mutex_lock (&u->lock); |
|
|
4328 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4329 | ev_async_send (EV_A_ &u->async_w); |
|
|
4330 | pthread_mutex_unlock (&u->lock); |
|
|
4331 | |
|
|
4332 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4333 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4334 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4335 | watchers in the next event loop iteration. |
|
|
4336 | |
3798 | =head3 COROUTINES |
4337 | =head3 COROUTINES |
3799 | |
4338 | |
3800 | Libev is very accommodating to coroutines ("cooperative threads"): |
4339 | Libev is very accommodating to coroutines ("cooperative threads"): |
3801 | libev fully supports nesting calls to its functions from different |
4340 | libev fully supports nesting calls to its functions from different |
3802 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4341 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3803 | different coroutines, and switch freely between both coroutines running the |
4342 | different coroutines, and switch freely between both coroutines running |
3804 | loop, as long as you don't confuse yourself). The only exception is that |
4343 | the loop, as long as you don't confuse yourself). The only exception is |
3805 | you must not do this from C<ev_periodic> reschedule callbacks. |
4344 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3806 | |
4345 | |
3807 | Care has been taken to ensure that libev does not keep local state inside |
4346 | Care has been taken to ensure that libev does not keep local state inside |
3808 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4347 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3809 | they do not call any callbacks. |
4348 | they do not call any callbacks. |
3810 | |
4349 | |
… | |
… | |
3824 | maintainable. |
4363 | maintainable. |
3825 | |
4364 | |
3826 | And of course, some compiler warnings are just plain stupid, or simply |
4365 | And of course, some compiler warnings are just plain stupid, or simply |
3827 | wrong (because they don't actually warn about the condition their message |
4366 | wrong (because they don't actually warn about the condition their message |
3828 | seems to warn about). For example, certain older gcc versions had some |
4367 | seems to warn about). For example, certain older gcc versions had some |
3829 | warnings that resulted an extreme number of false positives. These have |
4368 | warnings that resulted in an extreme number of false positives. These have |
3830 | been fixed, but some people still insist on making code warn-free with |
4369 | been fixed, but some people still insist on making code warn-free with |
3831 | such buggy versions. |
4370 | such buggy versions. |
3832 | |
4371 | |
3833 | While libev is written to generate as few warnings as possible, |
4372 | While libev is written to generate as few warnings as possible, |
3834 | "warn-free" code is not a goal, and it is recommended not to build libev |
4373 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3870 | I suggest using suppression lists. |
4409 | I suggest using suppression lists. |
3871 | |
4410 | |
3872 | |
4411 | |
3873 | =head1 PORTABILITY NOTES |
4412 | =head1 PORTABILITY NOTES |
3874 | |
4413 | |
|
|
4414 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4415 | |
|
|
4416 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4417 | interfaces but I<disables> them by default. |
|
|
4418 | |
|
|
4419 | That means that libev compiled in the default environment doesn't support |
|
|
4420 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4421 | |
|
|
4422 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4423 | by enabling the large file API, which makes them incompatible with the |
|
|
4424 | standard libev compiled for their system. |
|
|
4425 | |
|
|
4426 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4427 | suddenly make it incompatible to the default compile time environment, |
|
|
4428 | i.e. all programs not using special compile switches. |
|
|
4429 | |
|
|
4430 | =head2 OS/X AND DARWIN BUGS |
|
|
4431 | |
|
|
4432 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4433 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4434 | OpenGL drivers. |
|
|
4435 | |
|
|
4436 | =head3 C<kqueue> is buggy |
|
|
4437 | |
|
|
4438 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4439 | only sockets, many support pipes. |
|
|
4440 | |
|
|
4441 | Libev tries to work around this by not using C<kqueue> by default on |
|
|
4442 | this rotten platform, but of course you can still ask for it when creating |
|
|
4443 | a loop. |
|
|
4444 | |
|
|
4445 | =head3 C<poll> is buggy |
|
|
4446 | |
|
|
4447 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4448 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4449 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4450 | |
|
|
4451 | Libev tries to work around this by not using C<poll> by default on |
|
|
4452 | this rotten platform, but of course you can still ask for it when creating |
|
|
4453 | a loop. |
|
|
4454 | |
|
|
4455 | =head3 C<select> is buggy |
|
|
4456 | |
|
|
4457 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4458 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4459 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4460 | you use more. |
|
|
4461 | |
|
|
4462 | There is an undocumented "workaround" for this - defining |
|
|
4463 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4464 | work on OS/X. |
|
|
4465 | |
|
|
4466 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4467 | |
|
|
4468 | =head3 C<errno> reentrancy |
|
|
4469 | |
|
|
4470 | The default compile environment on Solaris is unfortunately so |
|
|
4471 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4472 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
|
|
4473 | isn't defined by default. |
|
|
4474 | |
|
|
4475 | If you want to use libev in threaded environments you have to make sure |
|
|
4476 | it's compiled with C<_REENTRANT> defined. |
|
|
4477 | |
|
|
4478 | =head3 Event port backend |
|
|
4479 | |
|
|
4480 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
|
|
4481 | this mechanism is very buggy. If you run into high CPU usage, your program |
|
|
4482 | freezes or you get a large number of spurious wakeups, make sure you have |
|
|
4483 | all the relevant and latest kernel patches applied. No, I don't know which |
|
|
4484 | ones, but there are multiple ones. |
|
|
4485 | |
|
|
4486 | If you can't get it to work, you can try running the program by setting |
|
|
4487 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4488 | C<select> backends. |
|
|
4489 | |
|
|
4490 | =head2 AIX POLL BUG |
|
|
4491 | |
|
|
4492 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4493 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4494 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4495 | with large bitsets, and AIX is dead anyway. |
|
|
4496 | |
3875 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4497 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4498 | |
|
|
4499 | =head3 General issues |
3876 | |
4500 | |
3877 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4501 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3878 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4502 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3879 | model. Libev still offers limited functionality on this platform in |
4503 | model. Libev still offers limited functionality on this platform in |
3880 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4504 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3881 | descriptors. This only applies when using Win32 natively, not when using |
4505 | descriptors. This only applies when using Win32 natively, not when using |
3882 | e.g. cygwin. |
4506 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4507 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4508 | environment. |
3883 | |
4509 | |
3884 | Lifting these limitations would basically require the full |
4510 | Lifting these limitations would basically require the full |
3885 | re-implementation of the I/O system. If you are into these kinds of |
4511 | re-implementation of the I/O system. If you are into this kind of thing, |
3886 | things, then note that glib does exactly that for you in a very portable |
4512 | then note that glib does exactly that for you in a very portable way (note |
3887 | way (note also that glib is the slowest event library known to man). |
4513 | also that glib is the slowest event library known to man). |
3888 | |
4514 | |
3889 | There is no supported compilation method available on windows except |
4515 | There is no supported compilation method available on windows except |
3890 | embedding it into other applications. |
4516 | embedding it into other applications. |
|
|
4517 | |
|
|
4518 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4519 | tries its best, but under most conditions, signals will simply not work. |
3891 | |
4520 | |
3892 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4521 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3893 | accept large writes: instead of resulting in a partial write, windows will |
4522 | accept large writes: instead of resulting in a partial write, windows will |
3894 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4523 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3895 | so make sure you only write small amounts into your sockets (less than a |
4524 | so make sure you only write small amounts into your sockets (less than a |
… | |
… | |
3900 | the abysmal performance of winsockets, using a large number of sockets |
4529 | the abysmal performance of winsockets, using a large number of sockets |
3901 | is not recommended (and not reasonable). If your program needs to use |
4530 | is not recommended (and not reasonable). If your program needs to use |
3902 | more than a hundred or so sockets, then likely it needs to use a totally |
4531 | more than a hundred or so sockets, then likely it needs to use a totally |
3903 | different implementation for windows, as libev offers the POSIX readiness |
4532 | different implementation for windows, as libev offers the POSIX readiness |
3904 | notification model, which cannot be implemented efficiently on windows |
4533 | notification model, which cannot be implemented efficiently on windows |
3905 | (Microsoft monopoly games). |
4534 | (due to Microsoft monopoly games). |
3906 | |
4535 | |
3907 | A typical way to use libev under windows is to embed it (see the embedding |
4536 | A typical way to use libev under windows is to embed it (see the embedding |
3908 | section for details) and use the following F<evwrap.h> header file instead |
4537 | section for details) and use the following F<evwrap.h> header file instead |
3909 | of F<ev.h>: |
4538 | of F<ev.h>: |
3910 | |
4539 | |
… | |
… | |
3917 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4546 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3918 | |
4547 | |
3919 | #include "evwrap.h" |
4548 | #include "evwrap.h" |
3920 | #include "ev.c" |
4549 | #include "ev.c" |
3921 | |
4550 | |
3922 | =over 4 |
|
|
3923 | |
|
|
3924 | =item The winsocket select function |
4551 | =head3 The winsocket C<select> function |
3925 | |
4552 | |
3926 | The winsocket C<select> function doesn't follow POSIX in that it |
4553 | The winsocket C<select> function doesn't follow POSIX in that it |
3927 | requires socket I<handles> and not socket I<file descriptors> (it is |
4554 | requires socket I<handles> and not socket I<file descriptors> (it is |
3928 | also extremely buggy). This makes select very inefficient, and also |
4555 | also extremely buggy). This makes select very inefficient, and also |
3929 | requires a mapping from file descriptors to socket handles (the Microsoft |
4556 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3938 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4565 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3939 | |
4566 | |
3940 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4567 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3941 | complexity in the O(n²) range when using win32. |
4568 | complexity in the O(n²) range when using win32. |
3942 | |
4569 | |
3943 | =item Limited number of file descriptors |
4570 | =head3 Limited number of file descriptors |
3944 | |
4571 | |
3945 | Windows has numerous arbitrary (and low) limits on things. |
4572 | Windows has numerous arbitrary (and low) limits on things. |
3946 | |
4573 | |
3947 | Early versions of winsocket's select only supported waiting for a maximum |
4574 | Early versions of winsocket's select only supported waiting for a maximum |
3948 | of C<64> handles (probably owning to the fact that all windows kernels |
4575 | of C<64> handles (probably owning to the fact that all windows kernels |
3949 | can only wait for C<64> things at the same time internally; Microsoft |
4576 | can only wait for C<64> things at the same time internally; Microsoft |
3950 | recommends spawning a chain of threads and wait for 63 handles and the |
4577 | recommends spawning a chain of threads and wait for 63 handles and the |
3951 | previous thread in each. Great). |
4578 | previous thread in each. Sounds great!). |
3952 | |
4579 | |
3953 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4580 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3954 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4581 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3955 | call (which might be in libev or elsewhere, for example, perl does its own |
4582 | call (which might be in libev or elsewhere, for example, perl and many |
3956 | select emulation on windows). |
4583 | other interpreters do their own select emulation on windows). |
3957 | |
4584 | |
3958 | Another limit is the number of file descriptors in the Microsoft runtime |
4585 | Another limit is the number of file descriptors in the Microsoft runtime |
3959 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4586 | libraries, which by default is C<64> (there must be a hidden I<64> |
3960 | or something like this inside Microsoft). You can increase this by calling |
4587 | fetish or something like this inside Microsoft). You can increase this |
3961 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4588 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3962 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4589 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3963 | libraries. |
|
|
3964 | |
|
|
3965 | This might get you to about C<512> or C<2048> sockets (depending on |
4590 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3966 | windows version and/or the phase of the moon). To get more, you need to |
4591 | (depending on windows version and/or the phase of the moon). To get more, |
3967 | wrap all I/O functions and provide your own fd management, but the cost of |
4592 | you need to wrap all I/O functions and provide your own fd management, but |
3968 | calling select (O(n²)) will likely make this unworkable. |
4593 | the cost of calling select (O(n²)) will likely make this unworkable. |
3969 | |
|
|
3970 | =back |
|
|
3971 | |
4594 | |
3972 | =head2 PORTABILITY REQUIREMENTS |
4595 | =head2 PORTABILITY REQUIREMENTS |
3973 | |
4596 | |
3974 | In addition to a working ISO-C implementation and of course the |
4597 | In addition to a working ISO-C implementation and of course the |
3975 | backend-specific APIs, libev relies on a few additional extensions: |
4598 | backend-specific APIs, libev relies on a few additional extensions: |
… | |
… | |
4016 | =item C<double> must hold a time value in seconds with enough accuracy |
4639 | =item C<double> must hold a time value in seconds with enough accuracy |
4017 | |
4640 | |
4018 | The type C<double> is used to represent timestamps. It is required to |
4641 | The type C<double> is used to represent timestamps. It is required to |
4019 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4642 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4020 | enough for at least into the year 4000. This requirement is fulfilled by |
4643 | enough for at least into the year 4000. This requirement is fulfilled by |
4021 | implementations implementing IEEE 754 (basically all existing ones). |
4644 | implementations implementing IEEE 754, which is basically all existing |
|
|
4645 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4646 | 2200. |
4022 | |
4647 | |
4023 | =back |
4648 | =back |
4024 | |
4649 | |
4025 | If you know of other additional requirements drop me a note. |
4650 | If you know of other additional requirements drop me a note. |
4026 | |
4651 | |
… | |
… | |
4094 | involves iterating over all running async watchers or all signal numbers. |
4719 | involves iterating over all running async watchers or all signal numbers. |
4095 | |
4720 | |
4096 | =back |
4721 | =back |
4097 | |
4722 | |
4098 | |
4723 | |
|
|
4724 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4725 | |
|
|
4726 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4727 | |
|
|
4728 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4729 | compatibility, so most programs should still compile. Those might be |
|
|
4730 | removed in later versions of libev, so better update early than late. |
|
|
4731 | |
|
|
4732 | =over 4 |
|
|
4733 | |
|
|
4734 | =item C<ev_loop_count> renamed to C<ev_iteration> |
|
|
4735 | |
|
|
4736 | =item C<ev_loop_depth> renamed to C<ev_depth> |
|
|
4737 | |
|
|
4738 | =item C<ev_loop_verify> renamed to C<ev_verify> |
|
|
4739 | |
|
|
4740 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4741 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
|
|
4742 | still called C<ev_loop_fork> because it would otherwise clash with the |
|
|
4743 | C<ev_fork> typedef. |
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|
4744 | |
|
|
4745 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
|
|
4746 | |
|
|
4747 | This is a simple rename - all other watcher types use their name |
|
|
4748 | as revents flag, and now C<ev_timer> does, too. |
|
|
4749 | |
|
|
4750 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
|
|
4751 | and continue to be present for the foreseeable future, so this is mostly a |
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4752 | documentation change. |
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4753 | |
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|
4754 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
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4755 | |
|
|
4756 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4757 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4758 | and work, but the library code will of course be larger. |
|
|
4759 | |
|
|
4760 | =back |
|
|
4761 | |
|
|
4762 | |
|
|
4763 | =head1 GLOSSARY |
|
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4764 | |
|
|
4765 | =over 4 |
|
|
4766 | |
|
|
4767 | =item active |
|
|
4768 | |
|
|
4769 | A watcher is active as long as it has been started (has been attached to |
|
|
4770 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4771 | |
|
|
4772 | =item application |
|
|
4773 | |
|
|
4774 | In this document, an application is whatever is using libev. |
|
|
4775 | |
|
|
4776 | =item callback |
|
|
4777 | |
|
|
4778 | The address of a function that is called when some event has been |
|
|
4779 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4780 | received the event, and the actual event bitset. |
|
|
4781 | |
|
|
4782 | =item callback invocation |
|
|
4783 | |
|
|
4784 | The act of calling the callback associated with a watcher. |
|
|
4785 | |
|
|
4786 | =item event |
|
|
4787 | |
|
|
4788 | A change of state of some external event, such as data now being available |
|
|
4789 | for reading on a file descriptor, time having passed or simply not having |
|
|
4790 | any other events happening anymore. |
|
|
4791 | |
|
|
4792 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4793 | C<EV_TIMER>). |
|
|
4794 | |
|
|
4795 | =item event library |
|
|
4796 | |
|
|
4797 | A software package implementing an event model and loop. |
|
|
4798 | |
|
|
4799 | =item event loop |
|
|
4800 | |
|
|
4801 | An entity that handles and processes external events and converts them |
|
|
4802 | into callback invocations. |
|
|
4803 | |
|
|
4804 | =item event model |
|
|
4805 | |
|
|
4806 | The model used to describe how an event loop handles and processes |
|
|
4807 | watchers and events. |
|
|
4808 | |
|
|
4809 | =item pending |
|
|
4810 | |
|
|
4811 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4812 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4813 | pending status is explicitly cleared by the application. |
|
|
4814 | |
|
|
4815 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4816 | its pending status. |
|
|
4817 | |
|
|
4818 | =item real time |
|
|
4819 | |
|
|
4820 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4821 | |
|
|
4822 | =item wall-clock time |
|
|
4823 | |
|
|
4824 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4825 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4826 | clock. |
|
|
4827 | |
|
|
4828 | =item watcher |
|
|
4829 | |
|
|
4830 | A data structure that describes interest in certain events. Watchers need |
|
|
4831 | to be started (attached to an event loop) before they can receive events. |
|
|
4832 | |
|
|
4833 | =item watcher invocation |
|
|
4834 | |
|
|
4835 | The act of calling the callback associated with a watcher. |
|
|
4836 | |
|
|
4837 | =back |
|
|
4838 | |
4099 | =head1 AUTHOR |
4839 | =head1 AUTHOR |
4100 | |
4840 | |
4101 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4841 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4102 | |
4842 | |