… | |
… | |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
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|
13 | |
|
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14 | #include <stdio.h> // for puts |
13 | |
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_TYPE |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
… | |
… | |
417 | i.e. keep at least one watcher active per fd at all times. Stopping and |
419 | i.e. keep at least one watcher active per fd at all times. Stopping and |
418 | starting a watcher (without re-setting it) also usually doesn't cause |
420 | starting a watcher (without re-setting it) also usually doesn't cause |
419 | extra overhead. A fork can both result in spurious notifications as well |
421 | extra overhead. A fork can both result in spurious notifications as well |
420 | as in libev having to destroy and recreate the epoll object, which can |
422 | as in libev having to destroy and recreate the epoll object, which can |
421 | take considerable time and thus should be avoided. |
423 | take considerable time and thus should be avoided. |
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424 | |
|
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425 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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426 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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427 | the usage. So sad. |
422 | |
428 | |
423 | While nominally embeddable in other event loops, this feature is broken in |
429 | While nominally embeddable in other event loops, this feature is broken in |
424 | all kernel versions tested so far. |
430 | all kernel versions tested so far. |
425 | |
431 | |
426 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
432 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
… | |
… | |
1415 | else |
1421 | else |
1416 | { |
1422 | { |
1417 | // callback was invoked, but there was some activity, re-arm |
1423 | // callback was invoked, but there was some activity, re-arm |
1418 | // the watcher to fire in last_activity + 60, which is |
1424 | // the watcher to fire in last_activity + 60, which is |
1419 | // guaranteed to be in the future, so "again" is positive: |
1425 | // guaranteed to be in the future, so "again" is positive: |
1420 | w->again = timeout - now; |
1426 | w->repeat = timeout - now; |
1421 | ev_timer_again (EV_A_ w); |
1427 | ev_timer_again (EV_A_ w); |
1422 | } |
1428 | } |
1423 | } |
1429 | } |
1424 | |
1430 | |
1425 | To summarise the callback: first calculate the real timeout (defined |
1431 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1997 | |
2003 | |
1998 | There is no support for kqueue, as apparently it cannot be used to |
2004 | There is no support for kqueue, as apparently it cannot be used to |
1999 | implement this functionality, due to the requirement of having a file |
2005 | implement this functionality, due to the requirement of having a file |
2000 | descriptor open on the object at all times, and detecting renames, unlinks |
2006 | descriptor open on the object at all times, and detecting renames, unlinks |
2001 | etc. is difficult. |
2007 | etc. is difficult. |
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|
2008 | |
|
|
2009 | =head3 C<stat ()> is a synchronous operation |
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2010 | |
|
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2011 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
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2012 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2013 | ()>, which is a synchronous operation. |
|
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2014 | |
|
|
2015 | For local paths, this usually doesn't matter: unless the system is very |
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2016 | busy or the intervals between stat's are large, a stat call will be fast, |
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2017 | as the path data is suually in memory already (except when starting the |
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2018 | watcher). |
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2019 | |
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2020 | For networked file systems, calling C<stat ()> can block an indefinite |
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2021 | time due to network issues, and even under good conditions, a stat call |
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2022 | often takes multiple milliseconds. |
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2023 | |
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2024 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
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2025 | paths, although this is fully supported by libev. |
2002 | |
2026 | |
2003 | =head3 The special problem of stat time resolution |
2027 | =head3 The special problem of stat time resolution |
2004 | |
2028 | |
2005 | The C<stat ()> system call only supports full-second resolution portably, |
2029 | The C<stat ()> system call only supports full-second resolution portably, |
2006 | and even on systems where the resolution is higher, most file systems |
2030 | and even on systems where the resolution is higher, most file systems |
… | |
… | |
2975 | Tony Arcieri has written a ruby extension that offers access to a subset |
2999 | Tony Arcieri has written a ruby extension that offers access to a subset |
2976 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3000 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2977 | more on top of it. It can be found via gem servers. Its homepage is at |
3001 | more on top of it. It can be found via gem servers. Its homepage is at |
2978 | L<http://rev.rubyforge.org/>. |
3002 | L<http://rev.rubyforge.org/>. |
2979 | |
3003 | |
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3004 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
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3005 | makes rev work even on mingw. |
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3006 | |
2980 | =item D |
3007 | =item D |
2981 | |
3008 | |
2982 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3009 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2983 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3010 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2984 | |
3011 | |
… | |
… | |
3160 | keeps libev from including F<config.h>, and it also defines dummy |
3187 | keeps libev from including F<config.h>, and it also defines dummy |
3161 | implementations for some libevent functions (such as logging, which is not |
3188 | implementations for some libevent functions (such as logging, which is not |
3162 | supported). It will also not define any of the structs usually found in |
3189 | supported). It will also not define any of the structs usually found in |
3163 | F<event.h> that are not directly supported by the libev core alone. |
3190 | F<event.h> that are not directly supported by the libev core alone. |
3164 | |
3191 | |
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3192 | In stanbdalone mode, libev will still try to automatically deduce the |
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3193 | configuration, but has to be more conservative. |
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3194 | |
3165 | =item EV_USE_MONOTONIC |
3195 | =item EV_USE_MONOTONIC |
3166 | |
3196 | |
3167 | If defined to be C<1>, libev will try to detect the availability of the |
3197 | If defined to be C<1>, libev will try to detect the availability of the |
3168 | monotonic clock option at both compile time and runtime. Otherwise no use |
3198 | monotonic clock option at both compile time and runtime. Otherwise no |
3169 | of the monotonic clock option will be attempted. If you enable this, you |
3199 | use of the monotonic clock option will be attempted. If you enable this, |
3170 | usually have to link against librt or something similar. Enabling it when |
3200 | you usually have to link against librt or something similar. Enabling it |
3171 | the functionality isn't available is safe, though, although you have |
3201 | when the functionality isn't available is safe, though, although you have |
3172 | to make sure you link against any libraries where the C<clock_gettime> |
3202 | to make sure you link against any libraries where the C<clock_gettime> |
3173 | function is hiding in (often F<-lrt>). |
3203 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3174 | |
3204 | |
3175 | =item EV_USE_REALTIME |
3205 | =item EV_USE_REALTIME |
3176 | |
3206 | |
3177 | If defined to be C<1>, libev will try to detect the availability of the |
3207 | If defined to be C<1>, libev will try to detect the availability of the |
3178 | real-time clock option at compile time (and assume its availability at |
3208 | real-time clock option at compile time (and assume its availability at |
3179 | runtime if successful). Otherwise no use of the real-time clock option will |
3209 | runtime if successful). Otherwise no use of the real-time clock option will |
3180 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3210 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3181 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3211 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3182 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3212 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3183 | |
3213 | |
|
|
3214 | =item EV_USE_CLOCK_SYSCALL |
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|
3215 | |
|
|
3216 | If defined to be C<1>, libev will try to use a direct syscall instead |
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|
3217 | of calling the system-provided C<clock_gettime> function. This option |
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|
3218 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
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|
3219 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
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3220 | programs needlessly. Using a direct syscall is slightly slower, because |
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3221 | no optimised vdso implementation can be used, but avoids the pthread |
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|
3222 | dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or higher. |
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|
3223 | |
3184 | =item EV_USE_NANOSLEEP |
3224 | =item EV_USE_NANOSLEEP |
3185 | |
3225 | |
3186 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3226 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3187 | and will use it for delays. Otherwise it will use C<select ()>. |
3227 | and will use it for delays. Otherwise it will use C<select ()>. |
3188 | |
3228 | |
… | |
… | |
3203 | |
3243 | |
3204 | =item EV_SELECT_USE_FD_SET |
3244 | =item EV_SELECT_USE_FD_SET |
3205 | |
3245 | |
3206 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3246 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3207 | structure. This is useful if libev doesn't compile due to a missing |
3247 | structure. This is useful if libev doesn't compile due to a missing |
3208 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3248 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3209 | exotic systems. This usually limits the range of file descriptors to some |
3249 | on exotic systems. This usually limits the range of file descriptors to |
3210 | low limit such as 1024 or might have other limitations (winsocket only |
3250 | some low limit such as 1024 or might have other limitations (winsocket |
3211 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3251 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3212 | influence the size of the C<fd_set> used. |
3252 | configures the maximum size of the C<fd_set>. |
3213 | |
3253 | |
3214 | =item EV_SELECT_IS_WINSOCKET |
3254 | =item EV_SELECT_IS_WINSOCKET |
3215 | |
3255 | |
3216 | When defined to C<1>, the select backend will assume that |
3256 | When defined to C<1>, the select backend will assume that |
3217 | select/socket/connect etc. don't understand file descriptors but |
3257 | select/socket/connect etc. don't understand file descriptors but |