… | |
… | |
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> |
|
|
13 | |
|
|
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; |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_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. |
|
|
424 | |
|
|
425 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
426 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
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 |
… | |
… | |
1932 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1938 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1933 | and sees if it changed compared to the last time, invoking the callback if |
1939 | and sees if it changed compared to the last time, invoking the callback if |
1934 | it did. |
1940 | it did. |
1935 | |
1941 | |
1936 | The path does not need to exist: changing from "path exists" to "path does |
1942 | The path does not need to exist: changing from "path exists" to "path does |
1937 | not exist" is a status change like any other. The condition "path does |
1943 | not exist" is a status change like any other. The condition "path does not |
1938 | not exist" is signified by the C<st_nlink> field being zero (which is |
1944 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1939 | otherwise always forced to be at least one) and all the other fields of |
1945 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1940 | the stat buffer having unspecified contents. |
1946 | least one) and all the other fields of the stat buffer having unspecified |
|
|
1947 | contents. |
1941 | |
1948 | |
1942 | The path I<must not> end in a slash or contain special components such as |
1949 | The path I<must not> end in a slash or contain special components such as |
1943 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1950 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1944 | your working directory changes, then the behaviour is undefined. |
1951 | your working directory changes, then the behaviour is undefined. |
1945 | |
1952 | |
… | |
… | |
1955 | This watcher type is not meant for massive numbers of stat watchers, |
1962 | This watcher type is not meant for massive numbers of stat watchers, |
1956 | as even with OS-supported change notifications, this can be |
1963 | as even with OS-supported change notifications, this can be |
1957 | resource-intensive. |
1964 | resource-intensive. |
1958 | |
1965 | |
1959 | At the time of this writing, the only OS-specific interface implemented |
1966 | At the time of this writing, the only OS-specific interface implemented |
1960 | is the Linux inotify interface (implementing kqueue support is left as |
1967 | is the Linux inotify interface (implementing kqueue support is left as an |
1961 | an exercise for the reader. Note, however, that the author sees no way |
1968 | exercise for the reader. Note, however, that the author sees no way of |
1962 | of implementing C<ev_stat> semantics with kqueue). |
1969 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1963 | |
1970 | |
1964 | =head3 ABI Issues (Largefile Support) |
1971 | =head3 ABI Issues (Largefile Support) |
1965 | |
1972 | |
1966 | Libev by default (unless the user overrides this) uses the default |
1973 | Libev by default (unless the user overrides this) uses the default |
1967 | compilation environment, which means that on systems with large file |
1974 | compilation environment, which means that on systems with large file |
… | |
… | |
1978 | to exchange stat structures with application programs compiled using the |
1985 | to exchange stat structures with application programs compiled using the |
1979 | default compilation environment. |
1986 | default compilation environment. |
1980 | |
1987 | |
1981 | =head3 Inotify and Kqueue |
1988 | =head3 Inotify and Kqueue |
1982 | |
1989 | |
1983 | When C<inotify (7)> support has been compiled into libev (generally |
1990 | When C<inotify (7)> support has been compiled into libev and present at |
1984 | only available with Linux 2.6.25 or above due to bugs in earlier |
1991 | runtime, it will be used to speed up change detection where possible. The |
1985 | implementations) and present at runtime, it will be used to speed up |
1992 | inotify descriptor will be created lazily when the first C<ev_stat> |
1986 | change detection where possible. The inotify descriptor will be created |
1993 | watcher is being started. |
1987 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1988 | |
1994 | |
1989 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1995 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1990 | except that changes might be detected earlier, and in some cases, to avoid |
1996 | except that changes might be detected earlier, and in some cases, to avoid |
1991 | making regular C<stat> calls. Even in the presence of inotify support |
1997 | making regular C<stat> calls. Even in the presence of inotify support |
1992 | there are many cases where libev has to resort to regular C<stat> polling, |
1998 | there are many cases where libev has to resort to regular C<stat> polling, |
1993 | but as long as the path exists, libev usually gets away without polling. |
1999 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2000 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2001 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2002 | xfs are fully working) libev usually gets away without polling. |
1994 | |
2003 | |
1995 | 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 |
1996 | implement this functionality, due to the requirement of having a file |
2005 | implement this functionality, due to the requirement of having a file |
1997 | 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 |
1998 | etc. is difficult. |
2007 | etc. is difficult. |
|
|
2008 | |
|
|
2009 | =head3 C<stat ()> is a synchronous operation |
|
|
2010 | |
|
|
2011 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2012 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2013 | ()>, which is a synchronous operation. |
|
|
2014 | |
|
|
2015 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2016 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2017 | as the path data is suually in memory already (except when starting the |
|
|
2018 | watcher). |
|
|
2019 | |
|
|
2020 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2021 | time due to network issues, and even under good conditions, a stat call |
|
|
2022 | often takes multiple milliseconds. |
|
|
2023 | |
|
|
2024 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2025 | paths, although this is fully supported by libev. |
1999 | |
2026 | |
2000 | =head3 The special problem of stat time resolution |
2027 | =head3 The special problem of stat time resolution |
2001 | |
2028 | |
2002 | The C<stat ()> system call only supports full-second resolution portably, |
2029 | The C<stat ()> system call only supports full-second resolution portably, |
2003 | 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 |
… | |
… | |
2864 | |
2891 | |
2865 | myclass obj; |
2892 | myclass obj; |
2866 | ev::io iow; |
2893 | ev::io iow; |
2867 | iow.set <myclass, &myclass::io_cb> (&obj); |
2894 | iow.set <myclass, &myclass::io_cb> (&obj); |
2868 | |
2895 | |
|
|
2896 | =item w->set (object *) |
|
|
2897 | |
|
|
2898 | This is an B<experimental> feature that might go away in a future version. |
|
|
2899 | |
|
|
2900 | This is a variation of a method callback - leaving out the method to call |
|
|
2901 | will default the method to C<operator ()>, which makes it possible to use |
|
|
2902 | functor objects without having to manually specify the C<operator ()> all |
|
|
2903 | the time. Incidentally, you can then also leave out the template argument |
|
|
2904 | list. |
|
|
2905 | |
|
|
2906 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
2907 | int revents)>. |
|
|
2908 | |
|
|
2909 | See the method-C<set> above for more details. |
|
|
2910 | |
|
|
2911 | Example: use a functor object as callback. |
|
|
2912 | |
|
|
2913 | struct myfunctor |
|
|
2914 | { |
|
|
2915 | void operator() (ev::io &w, int revents) |
|
|
2916 | { |
|
|
2917 | ... |
|
|
2918 | } |
|
|
2919 | } |
|
|
2920 | |
|
|
2921 | myfunctor f; |
|
|
2922 | |
|
|
2923 | ev::io w; |
|
|
2924 | w.set (&f); |
|
|
2925 | |
2869 | =item w->set<function> (void *data = 0) |
2926 | =item w->set<function> (void *data = 0) |
2870 | |
2927 | |
2871 | Also sets a callback, but uses a static method or plain function as |
2928 | Also sets a callback, but uses a static method or plain function as |
2872 | callback. The optional C<data> argument will be stored in the watcher's |
2929 | callback. The optional C<data> argument will be stored in the watcher's |
2873 | C<data> member and is free for you to use. |
2930 | C<data> member and is free for you to use. |
… | |
… | |
2972 | Tony Arcieri has written a ruby extension that offers access to a subset |
3029 | Tony Arcieri has written a ruby extension that offers access to a subset |
2973 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3030 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2974 | more on top of it. It can be found via gem servers. Its homepage is at |
3031 | more on top of it. It can be found via gem servers. Its homepage is at |
2975 | L<http://rev.rubyforge.org/>. |
3032 | L<http://rev.rubyforge.org/>. |
2976 | |
3033 | |
|
|
3034 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3035 | makes rev work even on mingw. |
|
|
3036 | |
2977 | =item D |
3037 | =item D |
2978 | |
3038 | |
2979 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3039 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2980 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3040 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2981 | |
3041 | |
… | |
… | |
3157 | keeps libev from including F<config.h>, and it also defines dummy |
3217 | keeps libev from including F<config.h>, and it also defines dummy |
3158 | implementations for some libevent functions (such as logging, which is not |
3218 | implementations for some libevent functions (such as logging, which is not |
3159 | supported). It will also not define any of the structs usually found in |
3219 | supported). It will also not define any of the structs usually found in |
3160 | F<event.h> that are not directly supported by the libev core alone. |
3220 | F<event.h> that are not directly supported by the libev core alone. |
3161 | |
3221 | |
|
|
3222 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3223 | configuration, but has to be more conservative. |
|
|
3224 | |
3162 | =item EV_USE_MONOTONIC |
3225 | =item EV_USE_MONOTONIC |
3163 | |
3226 | |
3164 | If defined to be C<1>, libev will try to detect the availability of the |
3227 | If defined to be C<1>, libev will try to detect the availability of the |
3165 | monotonic clock option at both compile time and runtime. Otherwise no use |
3228 | monotonic clock option at both compile time and runtime. Otherwise no |
3166 | of the monotonic clock option will be attempted. If you enable this, you |
3229 | use of the monotonic clock option will be attempted. If you enable this, |
3167 | usually have to link against librt or something similar. Enabling it when |
3230 | you usually have to link against librt or something similar. Enabling it |
3168 | the functionality isn't available is safe, though, although you have |
3231 | when the functionality isn't available is safe, though, although you have |
3169 | to make sure you link against any libraries where the C<clock_gettime> |
3232 | to make sure you link against any libraries where the C<clock_gettime> |
3170 | function is hiding in (often F<-lrt>). |
3233 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3171 | |
3234 | |
3172 | =item EV_USE_REALTIME |
3235 | =item EV_USE_REALTIME |
3173 | |
3236 | |
3174 | If defined to be C<1>, libev will try to detect the availability of the |
3237 | If defined to be C<1>, libev will try to detect the availability of the |
3175 | real-time clock option at compile time (and assume its availability at |
3238 | real-time clock option at compile time (and assume its availability at |
3176 | runtime if successful). Otherwise no use of the real-time clock option will |
3239 | runtime if successful). Otherwise no use of the real-time clock option will |
3177 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3240 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3178 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3241 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3179 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3242 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3180 | |
3243 | |
|
|
3244 | =item EV_USE_CLOCK_SYSCALL |
|
|
3245 | |
|
|
3246 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3247 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3248 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3249 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3250 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3251 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3252 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3253 | higher, as it simplifies linking (no need for C<-lrt>). |
|
|
3254 | |
3181 | =item EV_USE_NANOSLEEP |
3255 | =item EV_USE_NANOSLEEP |
3182 | |
3256 | |
3183 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3257 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3184 | and will use it for delays. Otherwise it will use C<select ()>. |
3258 | and will use it for delays. Otherwise it will use C<select ()>. |
3185 | |
3259 | |
… | |
… | |
3200 | |
3274 | |
3201 | =item EV_SELECT_USE_FD_SET |
3275 | =item EV_SELECT_USE_FD_SET |
3202 | |
3276 | |
3203 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3277 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3204 | structure. This is useful if libev doesn't compile due to a missing |
3278 | structure. This is useful if libev doesn't compile due to a missing |
3205 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3279 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3206 | exotic systems. This usually limits the range of file descriptors to some |
3280 | on exotic systems. This usually limits the range of file descriptors to |
3207 | low limit such as 1024 or might have other limitations (winsocket only |
3281 | some low limit such as 1024 or might have other limitations (winsocket |
3208 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3282 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3209 | influence the size of the C<fd_set> used. |
3283 | configures the maximum size of the C<fd_set>. |
3210 | |
3284 | |
3211 | =item EV_SELECT_IS_WINSOCKET |
3285 | =item EV_SELECT_IS_WINSOCKET |
3212 | |
3286 | |
3213 | When defined to C<1>, the select backend will assume that |
3287 | When defined to C<1>, the select backend will assume that |
3214 | select/socket/connect etc. don't understand file descriptors but |
3288 | select/socket/connect etc. don't understand file descriptors but |