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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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… | |
396 | |
398 | |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
399 | If this flag bit is or'ed into the flag value (or the program runs setuid |
398 | or setgid) then libev will I<not> look at the environment variable |
400 | or setgid) then libev will I<not> look at the environment variable |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
401 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
400 | override the flags completely if it is found in the environment. This is |
402 | override the flags completely if it is found in the environment. This is |
401 | useful to try out specific backends to test their performance, or to work |
403 | useful to try out specific backends to test their performance, to work |
402 | around bugs. |
404 | around bugs, or to make libev threadsafe (accessing environment variables |
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405 | cannot be done in a threadsafe way, but usually it works if no other |
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406 | thread modifies them). |
403 | |
407 | |
404 | =item C<EVFLAG_FORKCHECK> |
408 | =item C<EVFLAG_FORKCHECK> |
405 | |
409 | |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
410 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
407 | make libev check for a fork in each iteration by enabling this flag. |
411 | make libev check for a fork in each iteration by enabling this flag. |
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… | |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
413 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
417 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
414 | C<pthread_atfork> which is even faster). |
418 | C<pthread_atfork> which is even faster). |
415 | |
419 | |
416 | The big advantage of this flag is that you can forget about fork (and |
420 | The big advantage of this flag is that you can forget about fork (and |
417 | forget about forgetting to tell libev about forking) when you use this |
421 | forget about forgetting to tell libev about forking, although you still |
418 | flag. |
422 | have to ignore C<SIGPIPE>) when you use this flag. |
419 | |
423 | |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
424 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
421 | environment variable. |
425 | environment variable. |
422 | |
426 | |
423 | =item C<EVFLAG_NOINOTIFY> |
427 | =item C<EVFLAG_NOINOTIFY> |
… | |
… | |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
682 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
679 | and C<ev_loop_destroy>. |
683 | and C<ev_loop_destroy>. |
680 | |
684 | |
681 | =item ev_loop_fork (loop) |
685 | =item ev_loop_fork (loop) |
682 | |
686 | |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
687 | This function sets a flag that causes subsequent C<ev_run> iterations |
684 | reinitialise the kernel state for backends that have one. Despite the |
688 | to reinitialise the kernel state for backends that have one. Despite |
685 | name, you can call it anytime, but it makes most sense after forking, in |
689 | the name, you can call it anytime you are allowed to start or stop |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
690 | watchers (except inside an C<ev_prepare> callback), but it makes most |
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691 | sense after forking, in the child process. You I<must> call it (or use |
687 | child before resuming or calling C<ev_run>. |
692 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
688 | |
693 | |
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694 | In addition, if you want to reuse a loop (via this function or |
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695 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
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696 | |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
697 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
698 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
699 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
692 | during fork. |
700 | during fork. |
693 | |
701 | |
694 | On the other hand, you only need to call this function in the child |
702 | On the other hand, you only need to call this function in the child |
… | |
… | |
2024 | |
2032 | |
2025 | The relative timeouts are calculated relative to the C<ev_now ()> |
2033 | The relative timeouts are calculated relative to the C<ev_now ()> |
2026 | time. This is usually the right thing as this timestamp refers to the time |
2034 | time. This is usually the right thing as this timestamp refers to the time |
2027 | of the event triggering whatever timeout you are modifying/starting. If |
2035 | of the event triggering whatever timeout you are modifying/starting. If |
2028 | you suspect event processing to be delayed and you I<need> to base the |
2036 | you suspect event processing to be delayed and you I<need> to base the |
2029 | timeout on the current time, use something like this to adjust for this: |
2037 | timeout on the current time, use something like the following to adjust |
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2038 | for it: |
2030 | |
2039 | |
2031 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2040 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
2032 | |
2041 | |
2033 | If the event loop is suspended for a long time, you can also force an |
2042 | If the event loop is suspended for a long time, you can also force an |
2034 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2043 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2035 | ()>. |
2044 | ()>, although that will push the event time of all outstanding events |
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2045 | further into the future. |
2036 | |
2046 | |
2037 | =head3 The special problem of unsynchronised clocks |
2047 | =head3 The special problem of unsynchronised clocks |
2038 | |
2048 | |
2039 | Modern systems have a variety of clocks - libev itself uses the normal |
2049 | Modern systems have a variety of clocks - libev itself uses the normal |
2040 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
2050 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
… | |
… | |
2389 | |
2399 | |
2390 | ev_periodic hourly_tick; |
2400 | ev_periodic hourly_tick; |
2391 | ev_periodic_init (&hourly_tick, clock_cb, |
2401 | ev_periodic_init (&hourly_tick, clock_cb, |
2392 | fmod (ev_now (loop), 3600.), 3600., 0); |
2402 | fmod (ev_now (loop), 3600.), 3600., 0); |
2393 | ev_periodic_start (loop, &hourly_tick); |
2403 | ev_periodic_start (loop, &hourly_tick); |
2394 | |
2404 | |
2395 | |
2405 | |
2396 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2406 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2397 | |
2407 | |
2398 | Signal watchers will trigger an event when the process receives a specific |
2408 | Signal watchers will trigger an event when the process receives a specific |
2399 | signal one or more times. Even though signals are very asynchronous, libev |
2409 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2409 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2419 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2410 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2420 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2411 | C<SIGINT> in both the default loop and another loop at the same time. At |
2421 | C<SIGINT> in both the default loop and another loop at the same time. At |
2412 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2422 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2413 | |
2423 | |
2414 | When the first watcher gets started will libev actually register something |
2424 | Only after the first watcher for a signal is started will libev actually |
2415 | with the kernel (thus it coexists with your own signal handlers as long as |
2425 | register something with the kernel. It thus coexists with your own signal |
2416 | you don't register any with libev for the same signal). |
2426 | handlers as long as you don't register any with libev for the same signal. |
2417 | |
2427 | |
2418 | If possible and supported, libev will install its handlers with |
2428 | If possible and supported, libev will install its handlers with |
2419 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2429 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2420 | not be unduly interrupted. If you have a problem with system calls getting |
2430 | not be unduly interrupted. If you have a problem with system calls getting |
2421 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2431 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2606 | |
2616 | |
2607 | =head2 C<ev_stat> - did the file attributes just change? |
2617 | =head2 C<ev_stat> - did the file attributes just change? |
2608 | |
2618 | |
2609 | This watches a file system path for attribute changes. That is, it calls |
2619 | This watches a file system path for attribute changes. That is, it calls |
2610 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2620 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2611 | and sees if it changed compared to the last time, invoking the callback if |
2621 | and sees if it changed compared to the last time, invoking the callback |
2612 | it did. |
2622 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
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2623 | happen after the watcher has been started will be reported. |
2613 | |
2624 | |
2614 | The path does not need to exist: changing from "path exists" to "path does |
2625 | The path does not need to exist: changing from "path exists" to "path does |
2615 | not exist" is a status change like any other. The condition "path does not |
2626 | not exist" is a status change like any other. The condition "path does not |
2616 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2627 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2617 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2628 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2902 | |
2913 | |
2903 | Prepare and check watchers are often (but not always) used in pairs: |
2914 | Prepare and check watchers are often (but not always) used in pairs: |
2904 | prepare watchers get invoked before the process blocks and check watchers |
2915 | prepare watchers get invoked before the process blocks and check watchers |
2905 | afterwards. |
2916 | afterwards. |
2906 | |
2917 | |
2907 | You I<must not> call C<ev_run> or similar functions that enter |
2918 | You I<must not> call C<ev_run> (or similar functions that enter the |
2908 | the current event loop from either C<ev_prepare> or C<ev_check> |
2919 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2909 | watchers. Other loops than the current one are fine, however. The |
2920 | C<ev_check> watchers. Other loops than the current one are fine, |
2910 | rationale behind this is that you do not need to check for recursion in |
2921 | however. The rationale behind this is that you do not need to check |
2911 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2922 | for recursion in those watchers, i.e. the sequence will always be |
2912 | C<ev_check> so if you have one watcher of each kind they will always be |
2923 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2913 | called in pairs bracketing the blocking call. |
2924 | kind they will always be called in pairs bracketing the blocking call. |
2914 | |
2925 | |
2915 | Their main purpose is to integrate other event mechanisms into libev and |
2926 | Their main purpose is to integrate other event mechanisms into libev and |
2916 | their use is somewhat advanced. They could be used, for example, to track |
2927 | their use is somewhat advanced. They could be used, for example, to track |
2917 | variable changes, implement your own watchers, integrate net-snmp or a |
2928 | variable changes, implement your own watchers, integrate net-snmp or a |
2918 | coroutine library and lots more. They are also occasionally useful if |
2929 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
3208 | used). |
3219 | used). |
3209 | |
3220 | |
3210 | struct ev_loop *loop_hi = ev_default_init (0); |
3221 | struct ev_loop *loop_hi = ev_default_init (0); |
3211 | struct ev_loop *loop_lo = 0; |
3222 | struct ev_loop *loop_lo = 0; |
3212 | ev_embed embed; |
3223 | ev_embed embed; |
3213 | |
3224 | |
3214 | // see if there is a chance of getting one that works |
3225 | // see if there is a chance of getting one that works |
3215 | // (remember that a flags value of 0 means autodetection) |
3226 | // (remember that a flags value of 0 means autodetection) |
3216 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3227 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3217 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3228 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3218 | : 0; |
3229 | : 0; |
… | |
… | |
3232 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3243 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3233 | |
3244 | |
3234 | struct ev_loop *loop = ev_default_init (0); |
3245 | struct ev_loop *loop = ev_default_init (0); |
3235 | struct ev_loop *loop_socket = 0; |
3246 | struct ev_loop *loop_socket = 0; |
3236 | ev_embed embed; |
3247 | ev_embed embed; |
3237 | |
3248 | |
3238 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3249 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3239 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3250 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3240 | { |
3251 | { |
3241 | ev_embed_init (&embed, 0, loop_socket); |
3252 | ev_embed_init (&embed, 0, loop_socket); |
3242 | ev_embed_start (loop, &embed); |
3253 | ev_embed_start (loop, &embed); |
… | |
… | |
3258 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3269 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3259 | of course. |
3270 | of course. |
3260 | |
3271 | |
3261 | =head3 The special problem of life after fork - how is it possible? |
3272 | =head3 The special problem of life after fork - how is it possible? |
3262 | |
3273 | |
3263 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3274 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3264 | up/change the process environment, followed by a call to C<exec()>. This |
3275 | up/change the process environment, followed by a call to C<exec()>. This |
3265 | sequence should be handled by libev without any problems. |
3276 | sequence should be handled by libev without any problems. |
3266 | |
3277 | |
3267 | This changes when the application actually wants to do event handling |
3278 | This changes when the application actually wants to do event handling |
3268 | in the child, or both parent in child, in effect "continuing" after the |
3279 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3892 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3903 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3893 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3904 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3894 | |
3905 | |
3895 | // my_ev.h |
3906 | // my_ev.h |
3896 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3907 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3897 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3908 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3898 | #include "../libev/ev.h" |
3909 | #include "../libev/ev.h" |
3899 | |
3910 | |
3900 | // my_ev.c |
3911 | // my_ev.c |
3901 | #define EV_H "my_ev.h" |
3912 | #define EV_H "my_ev.h" |
3902 | #include "../libev/ev.c" |
3913 | #include "../libev/ev.c" |
… | |
… | |
3979 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3990 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3980 | you to use some convenience methods to start/stop watchers and also change |
3991 | you to use some convenience methods to start/stop watchers and also change |
3981 | the callback model to a model using method callbacks on objects. |
3992 | the callback model to a model using method callbacks on objects. |
3982 | |
3993 | |
3983 | To use it, |
3994 | To use it, |
3984 | |
3995 | |
3985 | #include <ev++.h> |
3996 | #include <ev++.h> |
3986 | |
3997 | |
3987 | This automatically includes F<ev.h> and puts all of its definitions (many |
3998 | This automatically includes F<ev.h> and puts all of its definitions (many |
3988 | of them macros) into the global namespace. All C++ specific things are |
3999 | of them macros) into the global namespace. All C++ specific things are |
3989 | put into the C<ev> namespace. It should support all the same embedding |
4000 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
4092 | void operator() (ev::io &w, int revents) |
4103 | void operator() (ev::io &w, int revents) |
4093 | { |
4104 | { |
4094 | ... |
4105 | ... |
4095 | } |
4106 | } |
4096 | } |
4107 | } |
4097 | |
4108 | |
4098 | myfunctor f; |
4109 | myfunctor f; |
4099 | |
4110 | |
4100 | ev::io w; |
4111 | ev::io w; |
4101 | w.set (&f); |
4112 | w.set (&f); |
4102 | |
4113 | |
… | |
… | |
4617 | different cpus (or different cpu cores). This reduces dependencies |
4628 | different cpus (or different cpu cores). This reduces dependencies |
4618 | and makes libev faster. |
4629 | and makes libev faster. |
4619 | |
4630 | |
4620 | =item EV_NO_THREADS |
4631 | =item EV_NO_THREADS |
4621 | |
4632 | |
4622 | If defined to be C<1>, libev will assume that it will never be called |
4633 | If defined to be C<1>, libev will assume that it will never be called from |
4623 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
4634 | different threads (that includes signal handlers), which is a stronger |
4624 | above. This reduces dependencies and makes libev faster. |
4635 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
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|
4636 | libev faster. |
4625 | |
4637 | |
4626 | =item EV_ATOMIC_T |
4638 | =item EV_ATOMIC_T |
4627 | |
4639 | |
4628 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4640 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4629 | access is atomic with respect to other threads or signal contexts. No |
4641 | access is atomic with respect to other threads or signal contexts. No |
… | |
… | |
5425 | =over 4 |
5437 | =over 4 |
5426 | |
5438 | |
5427 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5439 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5428 | |
5440 | |
5429 | The backward compatibility mechanism can be controlled by |
5441 | The backward compatibility mechanism can be controlled by |
5430 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
5442 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5431 | section. |
5443 | section. |
5432 | |
5444 | |
5433 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5445 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5434 | |
5446 | |
5435 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5447 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |